U.S. patent application number 17/023725 was filed with the patent office on 2021-01-21 for method and device for verifying atrial activity oversensing consistency on his sensing channel.
The applicant listed for this patent is Pacesetter, Inc.. Invention is credited to Wenwen Li, Jan O. Mangual-Soto, Luke C. McSpadden, Yun Qiao.
Application Number | 20210016096 17/023725 |
Document ID | / |
Family ID | 1000005090680 |
Filed Date | 2021-01-21 |
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United States Patent
Application |
20210016096 |
Kind Code |
A1 |
Qiao; Yun ; et al. |
January 21, 2021 |
METHOD AND DEVICE FOR VERIFYING ATRIAL ACTIVITY OVERSENSING
CONSISTENCY ON HIS SENSING CHANNEL
Abstract
Methods and systems are provided herein and include an HIS
electrode configured to be located proximate to a HIS bundle and to
at least partially define a HIS sensing channel. The system
includes memory to store cardiac activity (CA) signals obtained
over the HIS sensing channel, the memory to store program
instructions; and one or more processors that, when executing the
program instructions, are configured for utilizing an atrial
oversensing (AO) process to analyze the CA signals, obtained over
the HIS sensing channel during an AO avoidance (AOA) window, for an
atrial activity (AA) component to identify AA beats. The system
applies a consistency criteria to the AA beats to determine a
number of the AA beats that are indicative of consistent AO. Based
on the consistency criteria and the number of AA beats indicative
of consistent AO, the system performs at least one of adjusting an
AO parameter utilized by the AO process or disabling the AO process
and manages HIS bundle pacing based on a ventricular event.
Inventors: |
Qiao; Yun; (Sunnyvale,
CA) ; Li; Wenwen; (San Jose, CA) ;
Mangual-Soto; Jan O.; (Rho, IT) ; McSpadden; Luke
C.; (Los Angeles, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pacesetter, Inc. |
Sylmar |
CA |
US |
|
|
Family ID: |
1000005090680 |
Appl. No.: |
17/023725 |
Filed: |
September 17, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16904837 |
Jun 18, 2020 |
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17023725 |
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16871166 |
May 11, 2020 |
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16904837 |
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62948047 |
Dec 13, 2019 |
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62875863 |
Jul 18, 2019 |
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62948047 |
Dec 13, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/36521 20130101;
A61N 1/371 20130101; A61N 1/36592 20130101; A61N 1/39622 20170801;
A61N 1/3937 20130101 |
International
Class: |
A61N 1/37 20060101
A61N001/37; A61N 1/365 20060101 A61N001/365; A61N 1/39 20060101
A61N001/39 |
Claims
1. A system, comprising: a HIS electrode configured to be located
proximate to a HIS bundle and to at least partially define a HIS
sensing channel; memory to store cardiac activity (CA) signals
obtained over the HIS sensing channel, the memory to store program
instructions; and one or more processors that, when executing the
program instructions, are configured for: utilizing an atrial
oversensing (AO) process to analyze the CA signals, obtained over
the HIS sensing channel during an AO avoidance (AOA) window, for an
atrial activity (AA) component to identify AA beats; applying a
consistency criteria to the AA beats to determine a number of the
AA beats that are indicative of consistent AO; based on the
consistency criteria and the number of AA beats indicative of
consistent AO, performing at least one of adjusting an AO parameter
utilized by the AO process or disabling the AO process; and
managing HIS bundle pacing based on a ventricular event.
2. The system of claim 1, wherein the one or more processors are
further configured to determine, for at least a portion of the AA
beats, an interval between a paced or sensed atrial (A) event and a
characteristic of interest (COI) within the AA component (A/AA
interval) of the corresponding AA beat, the applying the
consistency criteria including identifying a subset of the AA
beats, for which the A/AA interval is within a first connection
criteria.
3. The system of claim 1, wherein the one or more processors are
further configured to determine, for at least a portion of the AA
beats, a peak of the AA component (AA peak) of the corresponding AA
beat, the applying the consistency criteria including identifying a
subset of the AA beats, for which the AA peak is within a second
connection criteria.
4. The system of claim 1, wherein the one or more processors are
further configured to identify first and second subsets of the AA
beats, for which first and second characteristics of interest (COI)
of the AA components fall within the corresponding first and second
limits; and determining whether a number of beats in the first and
second subsets of the AA beats is indicative of consistent AO.
5. The system of claim 4, wherein the consistency criteria
correspond to limits about first and second median values for
corresponding first and second COI, the one or more processors
further configured to utilize the consistency criteria to
distinguish between candidate AA beats and outlier AA beats.
6. The system of claim 1, wherein the one or more processors are
further configured to adjust an AO parameter utilized by the AO
process when the number of AA beats indicative of AO exceed a
threshold, the AO parameter representing at least one of i) a start
time for the AOA window, a duration for the AOA window, or an AO
sensitivity profile utilized to analyze the CA signals over the HIS
sensing channel during the AOA window.
7. The system of claim 1, wherein the one or more processors are
further configured to disable the AO process when the number of AA
beats indicative of AO fall below a threshold.
8. The system of claim 1, wherein the one or more processors are
further configured to manage the HIS pacing by lowering a
sensitivity level of a ventricular event (VE) sensitivity profile
for the HIS sensing channel.
9. The system of claim 1, wherein the one or more processors are
further configured to maintain a count of a number of AA components
over a series of beats and, based on the count, determine whether
to maintain or change current settings for the length of the AOA
window and/or sensitivity profile.
10. The system of claim 1, wherein the AOA window represents a time
window enclosing atrial component activity components.
11. A method for pacing a HIS bundle of a patient heart using an
implantable medical device (IMD), the method comprising: obtaining
cardiac activity (CA) signals over a HIS sensing channel, the HIS
sensing channel utilizing a HIS electrode; utilizing an atrial
oversensing (AO) process to analyze the CA signals, obtained over
the HIS sensing channel during an AO avoidance (AOA) window, for an
atrial activity (AA) component to identify AA beats; applying a
consistency criteria to the AA beats to determine a number of the
AA beats that are indicative of consistent AO; based on the
consistency criteria and the number of AA beats indicative of
consistent AO, performing at least one of adjusting an AO parameter
utilized by the AO process or disabling the AO process; and
managing HIS bundle pacing based on a ventricular event.
12. The method of claim 11, further comprising determining, for at
least a portion of the AA beats, an interval between a paced or
sensed atrial (A) event and a characteristic of interest (COI)
within the AA component (A/AA interval) of the corresponding AA
beat, the applying the consistency criteria including identifying a
subset of the AA beats, for which the A/AA interval is within a
first connection criteria.
13. The method of claim 12, further comprising determining, for at
least a portion of the AA beats, a peak of the AA component (AA
peak) of the corresponding AA beat, the applying the consistency
criteria including identifying a subset of the AA beats, for which
the AA peak is within a second connection criteria.
14. The method of claim 11, wherein the applying the consistency
criteria further comprises identifying first and second subsets of
the AA beats, for which first and second characteristics of
interest (COI) of the AA components fall within the corresponding
first and second limits; and determining whether a number of beats
in the first and second subsets of the AA beats is indicative of
consistent AO.
15. The method of claim 14, wherein the consistency criteria
correspond to limits about first and second median values for
corresponding first and second COI, the method further comprising
utilizing the consistency criteria to distinguish between candidate
AA beats and outlier AA beats.
16. The method of claim 11, wherein the performing includes
adjusting an AO parameter utilized by the AO process when the
number of AA beats indicative of AO exceed a threshold, the AO
parameter representing at least one of i) a start time for the AOA
window, a duration for the AOA window, or an AO sensitivity profile
utilized to analyze the CA signals over the HIS sensing channel
during the AOA window.
17. The method of claim 11, wherein the performing includes
disabling the AO process when the number of AA beats indicative of
AO fall below a threshold.
18. The method of claim 11, wherein the managing the HIS pacing
includes lowering a sensitivity level of a ventricular event (VE)
sensitivity profile for the HIS sensing channel.
19. The method of claim 11, further comprising maintaining a count
of a number of AA components over a series of beats and, based on
the count, determining whether to maintain or change current
settings for the length of the AOA window and/or sensitivity
profile.
20. The method of claim 11, wherein the AOA window represents a
time window enclosing atrial component activity components.
Description
RELATED APPLICATION DATA
[0001] The present applications relates to, and claims priority,
from: U.S. Provisional Application 62/948,047, Titled "AUTOMATIC
PACING IMPULSE CALIBRATION USING PACING RESPONSE TRANSITIONS"
(Docket 13653USL1), filed Dec. 13, 2019; is a continuation
application of U.S. application Ser. No. 16/904,837, Titled
"SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND BACKUP PACING
TIMING", (Docket 13936US01) (13-0392US1), filed Jun. 18, 2020; and
is a continuation application of U.S. application Ser. No.
16/871,166, Titled "SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND
BACKUP PACING TIMING" (Docket 13845US01) (13-0381US01), filed May
11, 2020, which claims priority to: U.S. Provisional Application
62/875,863, Titled "SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND
BACKUP PACING TIMING" (Docket 13652USL1), filed Jul. 18, 2019, and
to U.S. Provisional Application 62/948,047, Titled "AUTOMATIC
PACING IMPULSE CALIBRATION USING PACING RESPONSE TRANSITIONS"
(Docket 13653USL1), filed Dec. 13, 2019, the complete subject
matter of which are expressly incorporated herein by reference in
their entireties.
BACKGROUND
[0002] Embodiments of the present disclosure generally relate to
HIS bundle pacing and more specifically, to avoid atrial activity
over sensing and to automatic pacing impulse calibration using
pacing response transitions.
[0003] In a normal human heart, the sinus node, generally located
near the junction of the superior vena cava and the right atrium,
constitutes the primary natural pacemaker initiating rhythmic
electrical excitation of the heart chambers. The cardiac impulse
arising from the sinus node is transmitted to the two atrial
chambers, causing a depolarization known as a P-wave and the
resulting atrial chamber contractions. The excitation pulse is
further transmitted to and through the ventricles via the
atrioventricular (AV) node and a ventricular conduction system
comprised of the bundle of HIS (also referred to as the HIS
bundle), the left and right bundle branches, and the Purkinje
fibers, causing a depolarization and the resulting ventricular
chamber contractions. The depolarization of the interventricular
septum and ventricles is generally referred to as a QRS complex and
is observed and measured through the use of electrocardiograms
(ECGs) and similar equipment for measuring electrical activity of
the heart.
[0004] Disruption of this natural pace-making and conduction system
as a result of aging or disease can be successfully treated by
artificial cardiac pacing using implantable cardiac stimulation
devices, including pacemakers and implantable defibrillators, which
deliver rhythmic electrical pulses or other anti-arrhythmia
therapies to the heart, via electrodes implanted in contact with
the heart tissue, at a desired energy and rate. To the extent the
electrical pulses are sufficient to induce depolarization of the
associated heart tissue, the heart tissue is said to be captured
and the minimum electrical pulse resulting in capture is generally
referred to as the capture threshold.
[0005] In the majority of individuals, the most effective heartbeat
is triggered by the patient's own natural pacing physiology.
Implantable cardiac stimulation devices are intended to fill in
when the natural pacing functionality of the patient's heart falls
or acts inefficiently (such as in cases of sinus arrest and
symptomatic bradycardia, respectively) or when the heart's
conduction system fails or acts inefficiently (such as in cases of
third-degree and second-degree (i.e., Mobitz II) AV blocks,
respectively). In a large number of heart failure patients, natural
conduction through the AV node and the HIS bundle are intact and
disruption of ventricular rhythm is the result of conduction
disorders residing in the left and/or right bundle branches.
Dilatation of the heart due to congestive heart failure (CNF) has
been associated with delayed conduction through the ventricles.
This delayed conduction leads to reduced hemodynamic efficiency of
the failing heart because of the resulting poor synchronization of
the heart chambers.
[0006] Direct stimulation of the HIS bundle has been found to
provide hemodynamic improvement for various patients including
those suffering from dilated cardiomyopathy but having normal
ventricular activation. Other examples of patients that may benefit
from direct stimulation of the HIS bundle include those with
atrioventricular junction (AVJ) ablation or third-degree AV block
that require permanent ventricular pacing. Accordingly, the natural
conduction system, when intact, can provide hemodynamically optimal
depolarization timing of the heart chambers.
[0007] However, an opportunity remains to improve upon HIS bundle
pacing methods and systems. For example, IMDs that include a HIS
bundle pacing (HBP) lead also have a HIS bundle sensing channel
that utilizes one or more electrodes on the HIS bundle pacing lead
to sense atrial and ventricular activity. Systems, that utilize HIS
bundle pacing, experience oversensing of atrial signals over the
HIS sensing channel. Heretofore, clinicians have attempted to avoid
over sensing by manually programming parameters associated with the
HIS sensing channel, such as to lower sensitivity and to extend a
ventricular blanking period.
[0008] The close proximity of the HIS bundle to the basal-septal
atrial myocardium, atrioventricular (AV) node, and basal-septal
ventricular myocardium presents unique challenges to physicians
during the implant process, especially those new to HIS implanting.
AV node capture or simultaneous HIS and atrial capture may not be
immediately apparent during implant without performing additional
testing. In cases with successful HIS capture, the multi-component
(one or more of atrial, HIS, and ventricular) signal in the HIS
intracardiac electrograms (IEGM) could also disrupt implantable
device logic and effect normal functionality. For example, a large
atrial signal, that is present on the HIS bipolar or unipolar IEGM,
can cause atrial oversensing (AO) and have undesirable
consequences.
[0009] Algorithms have been proposed for automated measurement of
HIS capture type and threshold based on the bipolar and unipolar
evoked responses. A large atrial signal or unintended atrial and AV
node capture may cause unreliable sensing of the HBP evoked
response thus rendering the algorithm inaccurate.
[0010] A need remains for methods and devices that overcome the
foregoing and other disadvantages of conventional approaches. For
example, a need remains for methods and systems that provide a
consistency verification, after identifying AO, to assure true AO
is identified.
[0011] Further, HBP could have the following responses: loss of
capture (LOC), RV/myocardial capture, non-selective HIS bundle (HB)
capture, and selective HB capture. Currently, the HBP capture types
and thresholds are being diagnosed in clinics by healthcare
professionals using 12-lead surface ECG. Various device-based
algorithms have been proposed to automatically diagnose HBP capture
types and thresholds. Notwithstanding, a large safety margin is
commonly used when programming the HBP output. An opportunity
remains to provide improved device-based algorithms for automatic
measurement and programming of HIS capture threshold, in order to
maximize HIS pacing while improving battery longevity.
[0012] Heretofore, HIS capture threshold test algorithms have been
proposed that identify HBP thresholds based on changes in evoked
response (ER) following a train of HBP at decremental amplitudes.
The HBP at decremental amplitudes is proposed to be performed in
DDD mode with short AV delay or in WI mode with overdrive pacing.
It is desirable to minimize the test duration to reduce any patient
discomfort. However, the HIS capture threshold test, utilizing
decremental HBP amplitudes, has experienced certain limitations. In
particular, an effect is experienced during the HIS capture
threshold test, in which capture thresholds measured, in response
to successive HBP at decrementing amplitudes, are usually slightly
lower as compared to capture thresholds that are measured, in
response to successive HBP at incrementing amplitudes.
[0013] A need remains for methods and systems that limit or avoid
the effect on capture thresholds resulting from the nature of the
changes in the amplitude (e.g., incrementing or decrementing) of
the successive HBP pulses, while minimizing test duration without
sacrificing accuracy when determining HBP capture type.
SUMMARY
[0014] In accordance with embodiments herein, an AO setup test is
provided to detect AO using the atrial timing on the atrial channel
and the time separation of atrial and ventricular signals on the
HIS channel during intrinsic AV conduction. The AO setup test is
generally applied when the device is in DDD mode as the AO setup
test utilizes the atrial sensed or paced event to initiate the
search (AOA) window for the atrial signal on the HIS channel. In
accordance with one implementation, the AO setup test measures both
atrial and ventricular (if available) signal amplitude on the HIS
channel during the AO setup test.
[0015] In accordance with embodiments herein, methods and systems
are described that automatically verifies AO consistency from the
HIS IEGM to ensure true AO is identified. The methods and systems
may further comprise a sequential step by step verification of the
AO identified.
[0016] In accordance with embodiments herein, methods and systems
are described that provide a nonsequential threshold search that
includes successive HBP pulses delivered at rough amplitude steps
over a first (e.g., large) range of pacing amplitudes, followed by
fine amplitude steps over a second (e.g., small) range of pacing
amplitudes. For example, the rough amplitude steps may be utilized
while decrementing amplitude between successive HBP pulses over the
first range, while the fine amplitude steps are utilized while
incrementing amplitudes between successive HBP pulses over the
second range. The nonsequential threshold search is managed in a
manner that seeks to limit/minimize test duration and to
limit/minimize a Wedensky effect without sacrificing accuracy.
[0017] In one aspect of the present disclosure, a method of
identifying pacing thresholds and programming a stimulation device
for HIS bundle pacing is provided. The stimulation device includes
a pulse generator, a stimulating electrode in proximity to a HIS
bundle of a patient heart, at least one sensing electrode adapted
to sense electrical activity of the patient heart, a processor, and
a memory. The method includes applying, using the pulse generator
and stimulating electrode, a first pacing impulse having a first
pacing impulse energy to the HIS bundle and, in response to
applying the first pacing impulse, collecting first response data
using the at least one sensing electrode. The method further
includes applying, using the pulse generator and stimulating
electrode, a second pacing impulse having a second pacing impulse
energy to the HIS bundle, the second pacing impulse energy being
different than the first pacing impulse energy and, in response to
applying the second pacing impulse, collecting second response data
using the at least one sensing electrode. The method also includes
identifying a change in one or more response characteristics
between the first response data and the second response data, the
response characteristics indicative of a change from a first
capture type for the first pacing impulse energy and a second
capture type for the second pacing impulse energy and, in response
to identifying the change in the one or more response
characteristics, setting a pacing impulse energy setting of the
stimulation device to the first pacing impulse energy.
[0018] In certain implementations, the first response data includes
a first unipolar electrogram (EGM) and the second response data
includes a second unipolar EGM. In such implementations, the
response characteristics may include unipolar stim-to-onset time
and unipolar width. In other implementations, the first response
data includes a first bipolar EGM and the second response data
includes a second bipolar EGM. In still other implementations,
wherein the first response data includes each of a first unipolar
electrogram (EGM) and a first bipolar EGM, the second response data
includes each of a second unipolar EGM and a second bipolar EGM,
and the response characteristics include each of bipolar
stim-to-peak and unipolar width. In yet other implementations, the
response characteristics include at least one of bipolar
stim-to-peak, unipolar width, unipolar stim-to-onset time, and
unipolar maximum positive slope. In other implementations, the
response characteristics include a first response characteristic
corresponding to total ventricular activation time and a second
response characteristic corresponding to time between pacing and
activation. In certain implementations, the first capture type
indicates capture of the HIS bundle and the second capture type
indicates a loss of capture of the HIS bundle. In still other
implementations, the first capture type indicates correction of a
branch bundle block and the second capture type indicates a loss of
branch bundle block correction.
[0019] In another aspect of the present disclosure, a cardiac
stimulation system adapted to deliver impulses for pacing the HIS
bundle of a patient heart is provided. The system includes a pulse
generator adapted to generate electrical impulses, a processor
communicatively coupled to the pulse generator and adapted to
measure responses of the patient heart using at least one sensing
electrode, and a memory communicatively coupled to the processor
including instructions executable by the processor. The
instructions cause the processor to apply, using the pulse
generator and a stimulating electrode, a first pacing impulse
having a first pacing impulse energy to the HIS bundle and, in
response to applying the first pacing impulse, to collect first
response data using a sensing electrode. The instructions further
cause the process to apply, using the pulse generator and the
stimulating electrode, a second pacing impulse having second pacing
impulse energy to the HIS bundle, the second pacing impulse energy
being different than the first pacing impulse energy and, in
response to applying the second pacing impulse, to collect second
response data using the at least one sensing electrode. The
instructions also cause the processor to identify a change in one
or more response characteristics between the first response data
and the second response data, the response characteristics
indicative of a change from a first capture type for the first
pacing impulse energy and a second capture type for the second
pacing impulse energy. The instructions further cause the process
to set a pacing impulse energy setting of the stimulation device to
the first pacing impulse energy in response to identifying the
change in the one or more response characteristics.
[0020] In certain implementations, the first response data includes
a first unipolar electrogram (EGM) and the second response data
includes a second unipolar EGM. In other implementations, the first
response data includes a first bipolar EGM and the second response
data includes a second bipolar EGM. In still other implementations,
the response characteristics include at least one of bipolar
stim-to-peak, unipolar width, unipolar stim-to-onset time, and
unipolar maximum positive slope. In other implementations, the
response characteristics include a first response characteristic
corresponding to total ventricular activation time and a second
response characteristic corresponding to time between pacing and
activation. In still other implementation, the first capture type
indicates capture of the HIS bundle and the second capture type
indicates a loss of capture of the HIS bundle. In other
implementations, the first capture type indicates correction of a
branch bundle block and the second capture type indicates a loss of
branch bundle block correction.
[0021] In yet another aspect of the present disclosure, a method of
identifying pacing thresholds and programming a stimulation device
for HIS bundle pacing is provided. The stimulation device includes
a pulse generator, a stimulating electrode in proximity to a HIS
bundle of a patient heart, and at least one sensing electrode
adapted to sense electrical activity of the patient heart. The
method includes collecting a first response data set for a first
pacing impulse energy. Collecting the first response data set
includes applying, using the pulse generator and stimulating
electrode, a plurality of first pacing impulses having the first
pacing impulse energy to the HIS bundle and measuring a response to
each of the plurality of first pacing impulses using the at least
one sensing electrode. The method further includes collecting a
second response data set for a second pacing impulse energy
different than the first pacing impulse energy. Collecting the
second response data set includes applying, using the pulse
generator and stimulating electrode, a plurality of second pacing
impulses having the second pacing impulse energy to the HIS bundle
and measuring a response to each of the plurality of second pacing
impulses using the at least one sensing electrode. Subsequent to
determining a variance of the responses of the first response data
set is below a variance value, the method includes identifying a
change in one or more response characteristics between the first
set of response data and the second set of response data, the
response characteristics indicative of a change from a first
capture type for the first pacing impulse energy and a second
capture type for the second pacing impulse energy. The method
further includes, in response to identifying the change in the one
or more response characteristic, setting a pacing impulse energy
setting of the stimulation device to the first pacing impulse
energy.
[0022] In certain implementations, each response of the first
response data set and each response of the second response data set
includes a unipolar electrogram (EGM). In other implementations,
each response of the first response data set and each response of
the second response data set includes a unipolar electrogram (EGM).
In still other implementations, the one or more response
characteristics include a first response characteristic
corresponding to total ventricular activation time and a second
response characteristic corresponding to time between pacing and
activation.
[0023] In accordance with another aspect herein, a method is
provided for identifying pacing thresholds and programming a
stimulation device for His bundle pacing (HBP), the stimulation
device including a pulse generator, a stimulating electrode in
proximity to a His bundle of a patient heart, and at least one
sensing electrode adapted to sense electrical activity of the
patient heart. The method comprises: applying, using the pulse
generator and stimulating electrode, a HBP pulse having an impulse
energy to the His bundle; in response to the applying a first
pacing impulse, measuring response data for a corresponding evoked
response using the at least one sensing electrode; determining a
response characteristic based on the response data; adjusting the
impulse energy and repeating the applying, measuring and
determining, wherein the impulse energy is adjusted in a
non-sequential manner between HBP pulses; identifying a change in
the response characteristic indicative of a change from a first
capture type and a second capture type; and setting one or more
parameters of a HBP therapy based on the change in the response
characteristic.
[0024] In accordance with other aspects herein, the repeating the
applying, measuring, determining and adjusting obtains a collection
of response characteristics for a collection of HBP pulses at
corresponding different impulse energies. Additionally or
alternatively, the adjusting in the non-sequential manner includes
at least one rough energy adjustment between first and second HBP
pulses and at least one fine energy adjustment between third and
fourth HBP pulses. Additionally or alternatively, the at least one
rough energy adjustment includes a voltage step-up of at least 1.0V
between the first and second HBP pulses and the at least one fine
energy adjustment includes a voltage step-down of no more than
0.25V between the third and fourth HBP pulses. Additionally or
alternatively, the adjusting applies the at least one rough energy
adjustment during a rough HBP test between upper and lower rough
limits and applies the at least one fine energy adjustment during a
fine HBP test between upper and lower fine limits, the upper and
lower fine limits defined based on a transition point identified
during the rough HBP test. Additionally or alternatively, the
identifying further comprises identifying a rough transition point
based on the response characteristic associated with the first and
second HBP pulses separated by the at least one rough energy
adjustment and refining the rough transition point to a fine
transition point based on the response characteristic associated
with the third and fourth HBP pulses separated by the at least one
fine energy adjustment.
[0025] In accordance with new and unique aspects herein, a system
is provided. The system comprises: a HIS electrode configured to be
located proximate to the HIS bundle and to at least partially
define a HIS sensing channel; memory to store cardiac activity (CA)
signals obtained over the HIS sensing channel, the memory to store
program instructions; and one or more processors that, when
executing the program instructions, are configured for: applying,
using a pulse generator and a stimulating electrode, a HBP pulse
having an impulse energy to the His bundle; in response to applying
a first pacing impulse, measuring response data for a corresponding
evoked response using at least one sensing electrode; determining a
response characteristic based on the response data; adjusting the
impulse energy and repeating the applying, measuring and
determining, wherein the impulse energy is adjusted in a
non-sequential manner between HBP pulses; identifying a change in
the response characteristic indicative of a change from a first
capture type and a second capture type; and setting one or more
parameters of a HBP therapy based on the change in the response
characteristic.
[0026] Additionally or alternatively, the one or more processors
repeat the applying, measuring, determining, and adjusting to
obtain a collection of response characteristics for a collection of
HBP pulses at corresponding different impulse energies.
Additionally or alternatively, the adjusting in the non-sequential
manner includes at least one rough energy adjustment between first
and second HBP pulses and at least one fine energy adjustment
between third and fourth HBP pulses. Additionally or alternatively,
the at least one rough energy adjustment includes a voltage step-up
of at least 1.0V between the first and second HBP pulses and the at
least one fine energy adjustment includes a voltage step-down of no
more than 0.25V between the third and fourth HBP pulses.
Additionally or alternatively, the adjusting applies the at least
one rough energy adjustment during a rough HBP test between upper
and lower rough limits and applies the at least one fine energy
adjustment during a fine HBP test between upper and lower fine
limits, the upper and lower fine limits defined based on a
transition point identified during the rough HBP test. Additionally
or alternatively, the identifying further comprises identifying a
rough transition point based on the response characteristic
associated with the first and second HBP pulses separated by the at
least one rough energy adjustment and refining the rough transition
point to a fine transition point based on the response
characteristic associated with the third and fourth HBP pulses
separated by the at least one fine energy adjustment.
[0027] In accordance with embodiments herein, a system is provided.
The system includes an HIS electrode configured to be located
proximate to a HIS bundle and to at least partially define a HIS
sensing channel. The system includes memory to store cardiac
activity (CA) signals obtained over the HIS sensing channel, the
memory to store program instructions; and one or more processors
that, when executing the program instructions, are configured for
utilizing an atrial oversensing (AO) process to analyze the CA
signals, obtained over the HIS sensing channel during an AO
avoidance (AOA) window, for an atrial activity (AA) component to
identify AA beats. The system applies a consistency criteria to the
AA beats to determine a number of the AA beats that are indicative
of consistent AO. Based on the consistency criteria and the number
of AA beats indicative of consistent AO, the system performs at
least one of adjusting an AO parameter utilized by the AO process
or disabling the AO process and manages HIS bundle pacing based on
a ventricular event.
[0028] Optionally, the one or more processors may be further
configured to determine, for at least a portion of the AA beats, an
interval between a paced or sensed atrial (A) event and a
characteristic of interest (COI) within the AA component (A/AA
interval) of the corresponding AA beat. The applying the
consistency criteria may include identifying a subset of the AA
beats, for which the A/AA interval is within a first connection
criteria. The one or more processors may be further configured to
determine, for at least a portion of the AA beats, a peak of the AA
component (AA peak) of the corresponding AA beat. The applying the
consistency criteria may include identifying a subset of the AA
beats, for which the AA peak is within a second connection
criteria. The one or more processors may be further configured to
identify first and second subsets of the AA beats, for which first
and second characteristics of interest (COI) of the AA components
fall within the corresponding first and second limits and may
determine whether a number of beats in the first and second subsets
of the AA beats is indicative of consistent AO.
[0029] Optionally, the consistency criteria may correspond to
limits about first and second median values for corresponding first
and second COI. The one or more processors may be further
configured to utilize the consistency criteria to distinguish
between candidate AA beats and outlier AA beats. The one or more
processors may be further configured to adjust an AO parameter
utilized by the AO process when the number of AA beats indicative
of AO exceed a threshold. The AO parameter may represent at least
one of i) a start time for the AOA window, a duration for the AOA
window, or an AO sensitivity profile utilized to analyze the CA
signals over the HIS sensing channel during the AOA window. The one
or more processors may be further configured to disable the AO
process when the number of AA beats indicative of AO fall below a
threshold. The one or more processors may be further configured to
manage the HIS pacing by lowering a sensitivity level of a
ventricular event (VE) sensitivity profile for the HIS sensing
channel. The one or more processors may be further configured to
maintain a count of a number of AA components over a series of
beats and, based on the count, determine whether to maintain or
change current settings for the length of the AOA window and/or
sensitivity profile. The AOA window may represent a time window
enclosing atrial component activity components.
[0030] In accordance with embodiments herein, a method for pacing a
HIS bundle of a patient heart using an implantable medical device
(IMD) is provided. The method obtains cardiac activity (CA) signals
over a HIS sensing channel. The HIS sensing channel utilizes a HIS
electrode and utilizes an atrial oversensing (AO) process to
analyze the CA signals, obtained over the HIS sensing channel
during an AO avoidance (AOA) window, for an atrial activity (AA)
component to identify AA beats. The method applies a consistency
criteria to the AA beats to determine a number of the AA beats that
are indicative of consistent AO. Based on the consistency criteria
and the number of AA beats indicative of consistent AO, the method
performs at least one of adjusting an AO parameter utilized by the
AO process or disabling the AO process and manages HIS bundle
pacing based on a ventricular event.
[0031] The method may determine for at least a portion of the AA
beats, an interval between a paced or sensed atrial (A) event and a
characteristic of interest (COI) within the AA component (A/AA
interval) of the corresponding AA beat. The applying the
consistency criteria may include identifying a subset of the AA
beats, for which the A/AA interval may be within a first connection
criteria. The method may determine, for at least a portion of the
AA beats, a peak of the AA component (AA peak) of the corresponding
AA beat. The applying the consistency criteria may include
identifying a subset of the AA beats, for which the AA peak is
within a second connection criteria. The applying the consistency
criteria may further comprise identifying first and second subsets
of the AA beats, for which first and second characteristics of
interest (COI) of the AA components fall within the corresponding
first and second limits; and may determine whether a number of
beats in the first and second subsets of the AA beats is indicative
of consistent AO. The consistency criteria may correspond to limits
about first and second median values for corresponding first and
second COI. The method may further comprise utilizing the
consistency criteria to distinguish between candidate AA beats and
outlier AA beats.
[0032] Optionally, the performing may include adjusting an AO
parameter utilized by the AO process when the number of AA beats
indicative of AO exceed a threshold. The AO parameter may represent
at least one of i) a start time for the AOA window, a duration for
the AOA window, or an AO sensitivity profile utilized to analyze
the CA signals over the HIS sensing channel during the AOA window.
The performing may include disabling the AO process when the number
of AA beats indicative of AO fall below a threshold. The managing
the HIS pacing may include lowering a sensitivity level of a
ventricular event (VE) sensitivity profile for the HIS sensing
channel. The method may maintain a count of a number of AA
components over a series of beats and based on the count,
determining whether to maintain or change current settings for the
length of the AOA window and/or sensitivity profile. The AOA window
may represent a time window enclosing atrial component activity
components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 illustrates a stimulation device in electrical
communication with a patient's heart by way of one or more of four
leads and suitable for delivering multi-chamber stimulation and
shock therapy in accordance with embodiments herein.
[0034] FIG. 2 illustrates a dual chamber stimulation device in
communication with one atrium, one ventricle, and the HIS bundle in
accordance with embodiments herein.
[0035] FIG. 3 illustrates a simplified block diagram of the
multi-chamber implantable stimulation device of FIG. 1, which is
capable of treating both fast and slow arrhythmias with stimulation
therapy, including cardioversion, defibrillation, and pacing
stimulation in accordance with embodiments herein.
[0036] FIG. 4A illustrates a process for implementing an atrial
over sensing (AOS) set up test in accordance with embodiments
herein.
[0037] FIG. 4B illustrates example CA signals collected over atrial
and HIS sensing channels and analyzed in accordance with
embodiments herein.
[0038] FIG. 4C illustrates example CA signals collected over atrial
and HIS sensing channels and analyzed in accordance with
embodiments herein.
[0039] FIG. 5 illustrates a process for implementing an AO
consistency check in accordance with embodiments herein.
[0040] FIG. 6 illustrates a first method in which pacing impulses
are applied at different energies and corresponding responses are
measured and recorded.
[0041] FIG. 7 illustrates a second method in which the results,
such as those obtained from the method of FIG. 6, are analyzed and
classified to determine pacing settings for the stimulation
device.
[0042] FIG. 8, for example, is a flow chart illustrating a method
that combines collection and analysis of response data to configure
pacing settings of a stimulation device.
[0043] FIG. 9 is a flow chart illustrating a method for collecting
multiple sets of response data for each of a range of pacing
impulse voltages.
[0044] FIG. 10 is a flow chart illustrating a method in which the
results obtained from the method of FIG. 9, are analyzed and
classified to determine pacing settings for the stimulation
device.
[0045] FIG. 11 illustrates a process for implementing a
nonsequential capture threshold test in accordance with embodiments
herein.
DETAILED DESCRIPTION
[0046] It will be readily understood that the components of the
embodiments as generally described and illustrated in the figures
herein, may be arranged and designed in a wide variety of different
configurations in addition to the described example embodiments.
Thus, the following more detailed description of the example
embodiments, as represented in the figures, is not intended to
limit the scope of the embodiments, as claimed, but is merely
representative of example embodiments.
[0047] Reference throughout this specification to "one embodiment"
or "an embodiment" (or the like) means that a particular feature,
structure, or characteristic described in connection with the
embodiment is included in at least one embodiment. Thus,
appearances of the phrases "in one embodiment" or "in an
embodiment" or the like in various places throughout this
specification are not necessarily all referring to the same
embodiment.
[0048] Furthermore, the described features, structures, or
characteristics may be combined in any suitable manner in one or
more embodiments. In the following description, numerous specific
details are provided to give a thorough understanding of
embodiments. One skilled in the relevant art will recognize,
however, that the various embodiments can be practiced without one
or more of the specific details, or with other methods, components,
materials, etc. In other instances, well-known structures,
materials, or operations are not shown or described in detail to
avoid obfuscation. The following description is intended only by
way of example, and simply illustrates certain example
embodiments.
[0049] The methods described herein may employ structures or
aspects of various embodiments (e.g., systems and/or methods)
discussed herein. In various embodiments, certain operations may be
omitted or added, certain operations may be combined, certain
operations may be performed simultaneously, certain operations may
be performed concurrently, certain operations may be split into
multiple operations, certain operations may be performed in a
different order, or certain operations or series of operations may
be re-performed in an iterative fashion. It should be noted that,
other methods may be used, in accordance with an embodiment herein.
Further, wherein indicated, the methods may be fully or partially
implemented by one or more processors of one or more devices or
systems. By way of example, one or more operations of each method
described herein may be implemented by one or more processors or
circuitry of an implantable medical device, while one or more other
operations of the methods described herein may be implemented by
one or more processors of an external device, such as a local
external device, clinician programmer and/or a remote server. While
the operations of some methods may be described as performed by the
processor(s) of one device, additionally, some or all of such
operations may be performed by the processor(s) of another device
described herein.
[0050] The terms "atrial activity component" and "AA component"
shall mean atrial pacing spikes or atrial evoked propagation or
spontaneous intrinsic atrial propagation sensed at HIS lead.
[0051] The terms "consistency" and "consistent," when used in
connection with describing AA beats an atrial over sensing, shall
mean that one or more characteristics of interest (COI) do not
change beyond a defined limit or range over a defined interval or
defined number of beats and that the one or more COI appear in the
same manner over the time. For example, consistency criteria shall
mean criteria utilized to determine whether AA beats exhibit one or
more characteristics that remain unchanged or within a defined
range over a collection of beats. As another example, consistent AO
shall mean that atrial over sensing was detected over the defined
interval or defined number of beats.
[0052] The term "intrinsic atrial-HIS delay" or "intrinsic AH
delay" shall mean conduction delay from the time of As or Ap event
in RA channel to the time HIS signal sensed at HIS lead electrodes.
Practically it can be derived from time delay of As or AP to sensed
ventricular depolarization (A-Vs)-the delay from pacing HIS to V
sense (HVs)+pacing latency at HIS. The peak means the max peak in
the specified window with either rectified or the absolute
values.
[0053] The term "outlier", when used in connection with AA beats,
A/AA intervals, AA peaks and the like, is used relative to a
mathematical reference or range to refer to items outside of or at
an outer boundary of the mathematical reference (e.g., mean,
average) or range.
[0054] The terms "rough" and "fine" are used, relative to one
another, to describe a general degree or level of amplitude change
between successive HBP pulses. As nonlimiting examples, a "rough"
amplitude change may correspond to steps of 1-5 V (and more
preferably between 0.5 V and 2 V) between successive HBP pulses,
while a "fine" amplitude change may correspond to steps of 0.1-0.5
V (and more preferably between 0.1 V and 0.25 V) between successive
HBP pulses. As another nonlimiting example, a fine amplitude change
may be a percentage (e.g., between 10% and 25%) of a rough
amplitude change.
[0055] The term "obtain" or "obtaining", as used in connection with
data, signals, information and the like, includes at least one of
i) accessing memory of an external device or remote server where
the data, signals, information, etc. are stored, ii) receiving the
data, signals, information, etc. over a wireless communications
link between the IMD and a local external device, and/or iii)
receiving the data, signals, information, etc. at a remote server
over a network connection. The obtaining operation, when from the
perspective of an IMD, may include sensing new signals in real
time, and/or accessing memory to read stored data, signals,
information, etc. from memory within the IMD. The obtaining
operation, when from the perspective of a local external device,
includes receiving the data, signals, information, etc. at a
transceiver of the local external device where the data, signals,
information, etc. are transmitted from an IMD and/or a remote
server. The obtaining operation may be from the perspective of a
remote server, such as when receiving the data, signals,
information, etc. at a network interface from a local external
device and/or directly from an IMD. The remote server may also
obtain the data, signals, information, etc. from local memory
and/or from other memory, such as within a cloud storage
environment and/or from the memory of a workstation or clinician
external programmer.
[0056] The obtaining operation, when from the perspective of an
IMD, may include sensing new signals in real time, and/or accessing
memory to read stored data, signals, information, etc. from memory
within the IMD. The obtaining operation, when from the perspective
of a local external device, includes receiving the data, signals,
information, etc. at a transceiver of the local external device
where the data, signals, information, etc. are transmitted from an
IMD and/or a remote server. The obtaining operation may be from the
perspective of a remote server, such as when receiving the data,
signals, information, etc. at a network interface from a local
external device and/or directly from the IMD. The remote server may
also obtain the data, signals, information, etc. from local memory
and/or from other memory, such as within a cloud storage
environment and/or from the memory of a workstation or clinician
external programmer.
[0057] Embodiments may be implemented in connection with one or
more implantable medical devices (IMDs). Non-limiting examples of
IMDs include one or more of a cardiac monitoring device, pacemaker,
cardioverter, cardiac rhythm management device, defibrillator,
neurostimulator, leadless monitoring device, leadless pacemaker,
and the like. For example, embodiments herein may be implemented
by, or in connection with, the systems and methods described in
U.S. Patent Application 2019/0022378, titled "SYSTEMS AND METHODS
FOR AUTOMATED CAPTURE THRESHOLD TESTING AND ASSOCIATED HIS BUNDLE
PACING", published Jan. 24, 2019, and/or U.S. patent application
Ser. No. 15/973,351, titled "METHOD AND SYSTEM TO DETECT R-WAVES IN
CARDIAC ARRHYTHMIC PATTERNS" the complete subject matter of which
is incorporated herein by reference in its entirety.
[0058] Additionally or alternatively, embodiments may be
implemented in connection with a transvenous IMD and/or one or more
leadless implantable medical device (LIMD) that include one or more
structural and/or functional aspects of the device(s) described in
U.S. Pat. No. 9,216,285 "Leadless Implantable Medical Device Having
Removable And Fixed Components" and U.S. Pat. No. 8,831,747
"LEADLESS NEUROSTIMULATION DEVICE AND METHOD INCLUDING THE SAME",
which are hereby incorporated by reference. Additionally or
alternatively, the IMD may include one or more structural and/or
functional aspects of the device(s) described in U.S. Pat. No.
8,391,980 "METHOD AND SYSTEM FOR IDENTIFYING A POTENTIAL LEAD
FAILURE IN AN IMPLANTABLE MEDICAL DEVICE" and U.S. Pat. No.
9,232,485 "System And Method For Selectively Communicating With An
Implantable Medical Device", which are hereby incorporated by
reference. The LIMD may communicate with one another to practice
the methods and systems described herein. Additionally or
alternatively, a transvenous IMD may communicate with one or more
LIMD to practice the methods and systems described herein.
[0059] Additionally or alternatively, embodiments may be
implemented in connection with a transvenous or leadless IMD and a
subcutaneous IMD that includes one or more structural and/or
functional aspects of the device(s) described in U.S. application
Ser. No. 15/973,195, titled "Subcutaneous Implantation Medical
Device With Multiple Parasternal-Anterior Electrodes" and filed May
7, 2018; U.S. application Ser. No. 15/973,219, titled "IMPLANTABLE
MEDICAL SYSTEMS AND METHODS INCLUDING PULSE GENERATORS AND LEADS"
filed May 7, 2018; U.S. application Ser. No. 15/973,249, titled
"SINGLE SITE IMPLANTATION METHODS FOR MEDICAL DEVICES HAVING
MULTIPLE LEADS", filed May 7, 2018, which are hereby incorporated
by reference in their entireties. Further, one or more combinations
of IMDs may be utilized from the above incorporated patents and
applications in accordance with embodiments herein.
[0060] Additionally or alternatively, embodiments herein may be
implemented by, and/or in connection with, the systems and methods
described in: U.S. Patent Application 2019/0022378, titled "SYSTEMS
AND METHODS FOR AUTOMATED CAPTURE THRESHOLD TESTING AND ASSOCIATED
HIS BUNDLE PACING", published Jan. 24, 2019, and/or U.S. patent
application Ser. No. 15/973,351, titled "METHOD AND SYSTEM TO
DETECT R-WAVES IN CARDIAC ARRHYTHMIC PATTERNS"; U.S. application
Ser. No. 16/904,837, filed Jun. 18, 2020, titled "SYSTEMS AND
METHODS FOR IMPROVED HIS BUNDLE AND BACKUP PACING TIMING"; U.S.
Provisional Application No. 62/902,698, Titled "METHOD AND DEVICE
FOR AVOIDING ATRIAL ACTIVITY OVERSENSING ON HIS SENSING CHANNEL,"
on Sep. 19, 2019, the complete subject matter of which are
incorporated herein by reference in their entireties.
[0061] Additionally or alternatively, embodiments herein may be
implemented by, and/or in connection with, the systems and methods
described in: U.S. application Ser. No. 16/904,837, Titled "SYSTEMS
AND METHODS FOR IMPROVED HIS BUNDLE AND BACKUP PACING TIMING",
(Docket 13936US01) (13-0392US1), filed Jun. 18, 2020; U.S.
application Ser. No. 16/871,166, Titled "SYSTEMS AND METHODS FOR
IMPROVED HIS BUNDLE AND BACKUP PACING TIMING" (Docket 13845US01)
(13-0381US01), filed May 11, 2020; U.S. Provisional Application
62/875,863, Titled "SYSTEMS AND METHODS FOR IMPROVED HIS BUNDLE AND
BACKUP PACING TIMING" (Docket 13652USL1), filed Jul. 18, 2019; U.S.
application Ser. No. 16/181,234, Titled "AUTOMATED OPTIMIZATION OF
HIS BUNDLE PACING FOR CARDIAC RESYNCHRONIZATION THERAPY" (Docket
13217US01) (13-0375US01), filed Nov. 5, 2018; U.S. application Ser.
No. 16/138,766, Titled "SYSTEMS AND METHODS FOR AUTOMATED CAPTURE
THRESHOLD TESTING AND ASSOCIATED HIS BUNDLE PACING" (Docket
13349US01) (13-0373US01), filed Sep. 21, 2018; U.S. application
Ser. No. 15/653,357, Titled "SYSTEMS AND METHODS FOR AUTOMATED
CAPTURE THRESHOLD TESTING AND ASSOCIATED HIS BUNDLE PACING" (Docket
A17P1011) (13-0371US01), filed Jul. 18, 2017; U.S. Provisional
Application 62/948,047, Titled "AUTOMATIC PACING IMPULSE
CALIBRATION USING PACING RESPONSE TRANSITIONS" (Docket 13653USL1),
filed Dec. 13, 2019, the complete subject matter of which are
incorporated herein by reference in their entireties.
[0062] Embodiments herein provide a consistency check for processes
that seek to avoid atrial over sensing (AO). As described in one or
more of the applications and/or patents referenced and incorporated
herein, AO avoidance processes may utilize P-wave duration (PWD),
intrinsic atrial-HIS (AH) delay and/or intrinsic atrial conduction
delay (IACD) to estimate a risk of oversensing atrial activity and
to automatically adjust a length of a post atrial ventricular
period (PAVP), which in some imitations may be referred to as an
atrial oversensing avoidance (AOA) window. The AO avoidance
processes may further adjust a maximum sensitivity setting with
ventricular safety pacing. PAVP is an initial time window for the
purpose of including atrial components and processing the signals
such as the peak and its location etc. The term PAVP may be used to
represent a subset of implementations for an AOA window. For
example, the term PAVP may be utilized to refer to implementations
in which the corresponding period is used as a device refractory
period, whereas the term "AOA window" is more generally used to
refer to a PAVP as well as implementations in which the
corresponding window period is not limited to only device
refractory periods, such as when a sense refractory period could
have other functions or features that are not used in connection
herewith.
[0063] The AO avoidance processes address the challenges that arise
when a HIS sensing channel is utilized to monitor for RV activity.
When the HIS electrode is located in the RA, the HIS sensing
channel detects RV activity as a low amplitude component of the CA
signal because the ventricular activity is occurring in the far
field and exhibits a low-frequency content which is filtered by the
HIS sense amplifier. Given that the HIS sensing channel is
configured to detect low amplitude, low frequency far field RV
signals, the potential arises that the IMD may over sense atrial or
HIS activity over the HIS sensing channel. The potential also
exists to over sense atrial activity when the HIS electrode is
located in the RV.
[0064] Embodiments of the present disclosure may be implemented in
either a dual chamber or multi-chamber cardiac stimulation device.
For example, the present disclosure may be implemented in a
rate-responsive multi-chamber cardiac stimulation device. Certain
cardiac pacemakers and defibrillators incorporate a pacing lead in
the right ventricle and may also include a second lead in the right
atrium. High-burden right ventricle pacing may contribute to the
development of pacing-induced cardiomyopathy and symptoms
associated with heart failure (HF). Several pathophysiologic
mechanisms have been implicated in the development of
pacing-induced HF, each of which likely stems from
non-physiological electrical and mechanical activation patterns
produced by right ventricle pacing. HIS bundle pacing (HBP) may
restore physiological activation patterns by utilizing a patient's
intrinsic conduction system and may do so even in the presence of
bundle branch block. HBP has also been shown to provide significant
QRS narrowing, with improved ejection fraction.
[0065] Another possible clinical application of HBP is cardiac
resynchronization therapy (CRT). Conventional CRT systems include
pacing from both a right ventricular and a left ventricular lead,
and have been shown most effective for patients exhibiting a wide
QRS complex and left bundle branch block. HBP has also been shown
to be effective at narrowing the QRS complex in patients with left
bundle branch block, likely due to the anatomy of the HIS bundle,
which includes right and left bundle fibers that are longitudinally
dissociated. Therefore, what is thought of as left bundle branch
block, can be a result of a proximal blockage within the HIS bundle
that eventually branches to the left bundle. As a result, by pacing
the HIS bundle distal to the blockage, a normalized QRS complex can
be achieved in some patients. Theoretically, this pacing mode may
provide even better results than known CRT treatments, as
activation propagates rapidly through natural conduction
pathways.
[0066] FIG. 1 illustrates a stimulation device 10 in electrical
communication with a patient's heart 12 by way of one or more of
four leads, 20, 21, 24, and 30 and suitable for delivering
multi-chamber stimulation and shock therapy. To sense atrial
cardiac signals and to provide right atrial chamber stimulation
therapy, the stimulation device 10 is coupled to an implantable
right atrial lead 20 having at least an atrial tip electrode 22,
which typically is implanted in the patient's right atrial
appendage or atrial septum. To sense left atrial and ventricular
cardiac signals and to provide left chamber pacing therapy, the
stimulation device 10 is coupled to a "coronary sinus" lead 24
designed for placement in the "coronary sinus region" via the
coronary sinus ostium for positioning a distal electrode within the
coronary veins overlying the left ventricle and/or additional
electrode(s) adjacent to the left atrium. As used herein, the
phrase "coronary sinus region" refers to the vasculature of the
left ventricle, including any portion of the coronary sinus, great
cardiac vein, left marginal vein, left posterior ventricular vein,
middle cardiac vein, and/or small cardiac vein or any other cardiac
vein accessible by the coronary sinus which overlies the left
ventricle. Accordingly, an exemplary coronary sinus lead 24 is
designed to receive atrial and ventricular cardiac signals and to
deliver left ventricular pacing therapy using at least a left
ventricular tip electrode 26, left atrial pacing therapy using at
least a left atrial ring electrode 27, and shocking therapy using
at least a left atrial coil electrode 28. In another embodiment, an
additional electrode for providing left ventricular defibrillation
shocking therapy may be included in the portion of the lead
overlying the left ventricle, adjacent to the ring electrode 25.
The stimulation device 10 is also shown in electrical communication
with the patient's heart 12 by way of an implantable right
ventricular lead 30 having, in this embodiment, a right ventricular
tip electrode 32, a right ventricular ring electrode 34, a right
ventricular coil electrode 36, and a superior vena cava (SVC) coil
electrode 38. Typically, the right ventricular lead 30 is
transvenously inserted into the heart 12 so as to place the right
ventricular tip electrode 32 in the right ventricular apex so that
the right ventricular coil electrode 36 will be positioned in the
right ventricle and the SVC coil electrode 38 will be positioned in
the superior vena cava. Accordingly, the right ventricular lead 30
is capable of receiving cardiac signals and delivering stimulation
in the form of pacing and shock therapy to the right ventricle.
[0067] The stimulation device 10 is further connected to a HIS
bundle lead 21 having a HIS tip electrode 16, such as a helical
active fixation device, and a HIS ring electrode 19 located
proximal from the HIS tip electrode 16. In certain implementations,
the HIS ring electrode 19 is located approximately 10 mm proximal
the HIS tip electrode 16. The HIS bundle lead 21 may be
transvenously inserted into the heart 12 so that the HIS tip
electrode 16 is positioned in the tissue of the HIS bundle. The HIS
bundle lead 21 may be located proximate the HIS bundle in the RA or
in the RV. Accordingly, the HIS bundle lead 21 is capable of
receiving depolarization signals propagated in the HIS bundle or
delivering stimulation to the HIS bundle, creating a depolarization
that can be propagated through the lower conductive pathways of the
right and left ventricles (i.e., the right and left bundle branches
and Purkinje fibers).
[0068] An alternative embodiment of the present disclosure is shown
in FIG. 2 in which a dual chamber stimulation device 210 is in
communication with one atrium, one ventricle, and the HIS bundle.
Though not explicitly illustrated in FIG. 2, a right atrial lead 20
can be optionally included. In such implementations, the
stimulation device 210 maintains communication with the right
atrium of the heart 12 via a right atrial lead 20 having at least
an atrial tip electrode 22 and an atrial ring electrode 23, and an
SVC coil electrode 239. A HIS bundle lead 221, having a HIS tip
electrode 216 and a HIS ring electrode 219, is positioned such that
the HIS tip electrode 216 is proximate the HIS bundle tissue. The
stimulation device 210 is shown in FIG. 2 in electrical
communication with the patient's heart 12 by way of a right
ventricular lead 230 including a right ventricular tip electrode
232, a right ventricular ring electrode 234, and a right
ventricular coil electrode 236.
[0069] Optionally, the distal end of the HIS bundle lead 21 is
further provided with a non-traumatic conductive surface (also
referred to herein interchangeably as a mapping collar). The
non-traumatic conductive surface is advantageously used to make
electrical measurements that indicate the location of the HIS
bundle without having to anchor the HIS bundle tip electrode 16
into the endocardial tissue. The non-traumatic conductive surface
and the HIS bundle tip electrode 16 are electrically coupled within
the lead body of the HIS bundle lead 21 and together form one
conductive element for the purposes of sensing, stimulation, and
impedance measurements. Drugs, for example an acute anti-arrhythmic
drug such as lidocaine and/or an anti-inflammatory agent such as
dexamethasone sodium phosphate, can be stored, for example, within
a reservoir (not shown) at the base of the HIS bundle tip electrode
16 for local dispensation.
[0070] The HIS bundle lead 21 is also provided with a HIS ring
electrode 19. The HIS ring electrode 19 is preferably spaced
between approximately 2 mm and 30 mm, but preferably 10 mm, from
the HIS tip electrode 16. The HIS ring electrode 19 may function as
the return electrode during bipolar sensing, stimulation, or
impedance measurement operations.
[0071] The HIS tip electrode 16 and the HIS ring electrode 19 are
each connected to flexible conductors respectively, which may run
the entire length of the HIS bundle lead 21. The flexible conductor
is connected to the HIS tip electrode 16 and is electrically
insulated from the flexible conductor by a layer of insulation. The
conductor is connected to the HIS ring electrode 19. The flexible
conductors serve to electrically couple the HIS ring electrode 19
and the HIS tip electrode 16 to the HIS ring electrode terminal 51
and the HIS tip electrode terminal 50, respectively. One embodiment
of the HIS bundle lead 21 is available from St. Jude Medical CRMD
as lead model No. 1488T.
[0072] Optionally, the HIS lead may be implanted in the RV with the
HIS tip electrode (16 or 216) located proximate the HIS bundle
along the septum wall. As a further option, the HIS tip electrode
may be configured as and/or provided on, a helical screw at the
distal end of the HIS lead, such that the HIS electrode is screwed
into the septum wall of the RV proximate the HIS bundle.
[0073] FIG. 3 illustrates a simplified block diagram of the
multi-chamber implantable stimulation device 10 of FIG. 1, which is
capable of treating both fast and slow arrhythmias with stimulation
therapy, including cardioversion, defibrillation, and pacing
stimulation. While a particular multi-chamber device is shown, this
is for illustration purposes only, and one of skill in the art
could readily duplicate, eliminate or disable the appropriate
circuitry in any desired combination to provide a device capable of
treating the appropriate chambers) with cardioversion,
defibrillation and pacing stimulation. The housing 40 for the
stimulation device 10, shown schematically in FIG. 3, is often
referred to as the "can", "case" or "case electrode" and may be
programmably selected to act as the return electrode for all
"unipolar" modes. The housing 40 may further be used as a return
electrode alone or in combination with one or more of the coil
electrodes 28, 36, and 38 (shown in FIG. 1) for shocking purposes.
The housing 40 further includes a connector (not shown) having a
plurality of terminals 42, 44, 46, 48, 50-52, 54, 56, and 58 (shown
schematically and, for convenience, next to the names of the
electrodes to which they are connected). As such, to achieve right
atrial sensing and pacing, the connector includes at least a right
atrial tip terminal (AR TIP) 42 adapted for connection to the
atrial tip electrode 22 (shown in FIG. 1).
[0074] To achieve left chamber sensing, pacing and shocking, the
connector includes at least a left ventricular tip terminal
(V.sub.L TIP) 44, a left atrial ring terminal (A.sub.L RING) 46,
and a left atrial shocking terminal (A.sub.L COIL) 48, which are
adapted for connection to the left ventricular tip electrode 26,
the left atrial ring electrode 27, and the left atrial coil
electrode 28, respectively (each shown in FIG. 1). To support right
chamber sensing, pacing and shocking, the connector further
includes a right ventricular tip terminal (V.sub.R TIP) 52, a right
ventricular ring terminal (V.sub.R RING) 54, a right ventricular
shocking terminal (RV COIL) 56, and an SVC shocking terminal (SVC
COIL) 58, which are adapted for connection to the right ventricular
tip electrode 32, right ventricular ring electrode 34, the right
ventricular coil electrode 36, and the SVC coil electrode 38,
respectively (each shown in FIG. 1). To achieve HIS bundle sensing,
or sensing and stimulation, the connector further includes a HIS
bundle lead tip terminal 50 and a HIS bundle lead ring terminal 51
which are adapted for connection to the HIS tip electrode 16 and
the HIS ring electrode 19, respectively (each shown in FIG. 1).
[0075] At the core of the stimulation device 10 is a programmable
microcontroller 60 which controls the various modes of stimulation
therapy. The microcontroller 60 includes a microprocessor, or
equivalent control circuitry, designed specifically for controlling
the delivery of stimulation therapy and may further include RAM or
ROM memory, logic and timing circuitry, state machine circuitry,
and I/O circuitry. Typically, the microcontroller 60 includes the
ability to process or monitor input signals (data) as controlled by
a program code stored in a designated block of memory. The details
of the design and operation of the microcontroller 60 are not
critical to the present disclosure. Rather, any suitable
microcontroller 60 may be used that carries out the functions
described herein.
[0076] As shown in FIG. 3, an atrial pulse generator 70 and a
ventricular pulse generator 72 generate pacing stimulation pulses
for delivery by the right atrial lead 20, the right ventricular
lead 30, the coronary sinus lead 24, and/or the HIS bundle lead 21
via an electrode configuration switch 74. It is understood that in
order to provide stimulation therapy in each of the four chambers
of the heart, the atrial and ventricular pulse generators 70, 72
may include dedicated, independent pulse generators, multiplexed
pulse generators, or shared pulse generators. The pulse generators
70, 72 are controlled by the microcontroller 60 via appropriate
control signals 76, 78, respectively, to trigger or inhibit the
stimulation pulses. As used herein, the shape of the stimulation
pulses is not limited to an exact square or rectangular shape, but
may assume any one of a plurality of shapes which is adequate for
the delivery of an energy pulse, packet, or stimulus.
[0077] The microcontroller 60 further includes timing control
circuitry 79 which is used to control the timing of such
stimulation pulses (e.g., pacing rate) as well as to keep track of
the timing of refractory periods, blanking intervals, noise
detection windows, evoked response windows, alert intervals, marker
channel timing, etc., which is well known in the art. According to
one embodiment of the present disclosure, timing control circuitry
79 also controls the onset and duration of a HIS signal sensing
window during which a depolarization signal conducted through the
AV node to the HIS bundle can be detected. Timing control circuitry
79 also controls a timing delay provided after a detected HIS
signal detection, prior to the delivery of a right and/or left
ventricular stimulation pulse. The switch 74 includes a plurality
of switches for connecting the desired electrodes to the
appropriate I/O circuits, thereby providing complete electrode
programmability. Accordingly, the switch 74, in response to a
control signal 80 from the microcontroller 60, determines the
polarity of the stimulation pulses (e.g., unipolar, bipolar,
cross-chamber, etc.) by selectively closing the appropriate
combination of switches (not shown) as is known in the art.
[0078] Atrial sensing circuits 82 and ventricular sensing circuits
84 may also be selectively coupled to the right atrial lead 20,
coronary sinus lead 24, and the right ventricular lead 30, through
the switch 74 for detecting the presence of cardiac activity in
each of the four chambers of the heart. Accordingly, the atrial
(ATR. SENSE) and ventricular (VTR. SENSE) sensing circuits 82, 84
may include dedicated sense amplifiers, multiplexed amplifiers, or
shared amplifiers. The switch 74 determines the "sensing polarity"
of the cardiac signal by selectively closing the appropriate
switches, as is also known in the art. In this way, the clinician
may program the sensing polarity independent of the stimulation
polarity.
[0079] According to one embodiment of the present disclosure, a HIS
sensing circuit 83 is selectively coupled to the HIS bundle lead 21
(shown in FIG. 1) for detecting the presence of a conducted
depolarization arising in the atria and conducted to the HIS bundle
via the AV node. As used herein, each of the atrial sensing circuit
82, the ventricular sensing circuit 84, and the HIS sensing circuit
83, includes a discriminator, which is a circuit that senses and
can indicate or discriminate the origin of a cardiac signal in each
of the cardiac chambers. Each sensing circuit 82-84 preferably
employs one or more low power, precision amplifiers with
programmable gain and/or automatic gain control, bandpass
filtering, and a threshold detection circuit to selectively sense
the cardiac signal of interest. The automatic gain control enables
the device 10 to deal effectively with the difficult problem of
sensing the low amplitude signal characteristics of atrial or
ventricular fibrillation. The outputs of the sensing circuits 82-84
are connected to the microcontroller 60 which, in turn, is able to
trigger or inhibit the atrial and ventricular pulse generators 70,
72, respectively, in a demand fashion in response to the absence or
presence of cardiac activity in the appropriate chambers of the
heart. The atrial and ventricular sensing circuits 82, 84, in turn,
receive control signals ever signal lines 86, 88, from the
microcontroller 60 for purposes of controlling the gain, threshold,
polarization charge removal circuitry (not shown), and the timing
of any blocking circuitry (not shown) coupled to the inputs of the
sensing circuits 82, 84.
[0080] For arrhythmia detection, the stimulation device 10 includes
an arrhythmia detector 77 that utilizes the atrial and ventricular
sensing circuits 82, 84, to sense cardiac signals to determine
whether a rhythm is physiologic or pathologic. As used herein
"sensing" is reserved for the noting of an electrical signal, and
"detection" is the processing of these sensed signals and noting
the presence of an arrhythmia. The timing intervals between sensed
events (e.g., P-waves, R-waves, and depolarization signals
associated with fibrillation) are then classified by the
microcontroller 60 by comparing them to a predefined rate zone
limit (i.e., bradycardia, normal, low rate VT, high rate VT, and
fibrillation rate zones) and various other characteristics (e.g.,
sudden onset, stability, physiologic sensors, and morphology, etc.)
in order to determine the type of remedial therapy that is needed
(e.g., bradycardia pacing, anti-tachycardia pacing, cardioversion
shocks or defibrillation shocks, collectively referred to as
"tiered therapy").
[0081] Cardiac signals are also applied to the inputs of an
analog-to-digital (ND) data acquisition system 90 represented by an
ND converter. The data acquisition system 90 is configured to
acquire intracardiac electrogram signals, convert the raw analog
data into a digital signal, and store the digital signals for later
processing and/or telemetric transmission to an external device
102. The data acquisition system 90 is coupled to the right atrial
lead 20, the HIS bundle lead 21, the coronary sinus lead 24, and
the right ventricular lead 30 through the switch 74 to sample
cardiac signals across any pair of desired electrodes.
[0082] In one embodiment, the data acquisition system 90 is coupled
to microcontroller 60, or to other detection circuitry, for
detecting a desired feature of the HIS bundle signal. In one
embodiment, an averager is used to determine a sliding average of
the HIS bundle signal during a HIS signal sensing window using
known or available signal averaging techniques.
[0083] Advantageously, the data acquisition system 90 may be
coupled to the microcontroller 60, or other detection circuitry,
for detecting an evoked response from the heart 12 in response to
an applied stimulus, thereby aiding in the detection of capture.
The microcontroller 60 detects a depolarization signal during a
window following a stimulation pulse, the presence of which
indicates that capture has occurred. The microcontroller 60 enables
capture detection by triggering the ventricular pulse generator 72
to generate a stimulation pulse, starting a capture detection
window using the timing control circuitry 79 within the
microcontroller 60, and enabling the data acquisition system 90 via
control signal 92 to sample the cardiac signal that falls in the
capture detection window and, based on the amplitude, determines if
capture has occurred.
[0084] The microcontroller 60 is further coupled to a memory 94 by
a suitable data/address bus 96, wherein the programmable operating
parameters used by the microcontroller 60 are stored and modified,
as required, in order to customize the operation of the stimulation
device 10 to suit the needs of a particular patient. Such operating
parameters define, for example, pacing pulse amplitude, pulse
duration, electrode polarity, rate, sensitivity, automatic
features, arrhythmia detection criteria, and the amplitude,
waveshape and vector of each shocking pulse to be delivered to the
patient's heart 12 within each respective tier of therapy.
[0085] The HIS sensing circuit 83 is connected to one or more HIS
electrodes, to collectively define the HIS sensing channel that
collects at least a portion of the CA signals. The atrial sensing
circuit 82 is connected to one or more RA electrodes, to
collectively define an RA sensing channel. The memory 94 is
configured to store the CA signals obtained over the RA sensing
channel and over the HIS sensing channel. The memory also is
configured to store program instructions.
[0086] The microcontroller 60 is configured, when executing the
program instructions, for: utilizing an atrial oversensing (AO)
process to analyze the CA signals, obtained over the HIS sensing
channel during an AO avoidance (AOA) window, for an atrial activity
(AA) component to identify AA beats; applying a consistency
criteria to the AA beats to determining a number of the AA beats
that are indicative of consistent AO; based on the consistency
criteria and the number of AA beats indicative of consistent AO,
performing at least one of adjusting an AO parameter utilized by
the AO process or disabling the AO process; and managing HIS bundle
pacing based on the ventricular event.
[0087] Additionally or alternatively, the microcontroller 60 be
configured to determine, for at least a portion of the AA beats, an
interval between a paced or sensed atrial (A) event and a
characteristic of interest (COI) within the AA component (A/AA
interval) of the corresponding AA beat, the applying the
consistency criteria including identifying a subset of the AA
beats, for which the A/AA interval is within a first connection
criteria. Additionally or alternatively, the microcontroller 60 be
configured to determine, for at least a portion of the AA beats, a
peak of the AA component (AA peak) of the corresponding AA beat,
the applying the consistency criteria including identifying a
subset of the AA beats, for which the AA peak is within a second
connection criteria. Additionally or alternatively, the
microcontroller 60 be configured to identify first and second
subsets of the AA beats, for which first and second characteristics
of interest (COI) of the AA components fall within the
corresponding first and second limits; and determining whether a
number of beats in the first and second subsets of the AA beats is
indicative of consistent AO. Additionally or alternatively, the
first and second criteria correspond to limits about first and
second median values for corresponding first and second COI, the
one or more processors further configured to utilize the first and
second criteria to distinguish between candidate AA beats and
outlier AA beats.
[0088] Additionally or alternatively, the microcontroller 60 be
configured to adjust an AO parameter utilized by the AO process
when the number of AA beats indicative of AO exceed a threshold,
the AO parameter representing at least one of i) a start time for
the AOA window, a duration for the AOA window, or an AO sensitivity
profile utilized to analyze the CA signals over the his sensing
channel during the AOA window. Additionally or alternatively, the
microcontroller 60 be configured to disable the AO process when the
number of AA beats indicative of AO fall below a threshold.
Additionally or alternatively, the microcontroller 60 be configured
to manage the HIS pacing by lowering a sensitivity level of the VE
sensitivity profile for the HIS sensing channel.
[0089] Additionally or alternatively, the microcontroller 60 be
configured to maintain a count of a number of AA components over a
series of beats and based on the count, determine whether to
maintain or change current settings for the length of the AOA
window and/or sensitivity profile. Additionally or alternatively,
the AOA window represents a time window enclosing atrial component
activity components.
[0090] Further, in accordance with aspects herein, the
microcontroller 60 may be configured to apply, using the pulse
generator and stimulating electrode, a HBP pulse having an impulse
energy to the His bundle; in response to applying the first pacing
impulse, measure response data for a corresponding evoked response
using the at least one sensing electrode; determine a response
characteristic based on the response data; adjust the impulse
energy and repeating the applying, measuring and determining,
wherein the impulse energy is adjusted in a non-sequential manner
between the HBP pulses; identify a change in the response
characteristic indicative of a change from a first capture type and
a second capture type; and set one or more parameters of a HBP
therapy based on the change in the response characteristic.
[0091] Additionally or alternatively, the microcontroller 60 may be
configured to repeat the applying, measuring, determining, and
adjusting to obtain a collection of response characteristics for a
collection of HBP pulses at corresponding different impulse
energies. Additionally or alternatively, the adjusting in the
non-sequential manner includes at least one rough energy adjustment
between first and second HBP pulses and at least one fine energy
adjustment between third and fourth HBP pulses. As explained
herein, at least one rough energy adjustment includes a voltage
step-up of at least 1.0V between the first and second HBP pulses
and the at least one fine energy adjustment includes a voltage
step-down of no more than 0.25V between the third and fourth HBP
pulses. Additionally or alternatively, the microcontroller 60 may
be further configured to apply the at least one rough energy
adjustment during a rough HBP test between upper and lower rough
limits and applies the at least one fine energy adjustment during a
fine HBP test between upper and lower fine limits, the upper and
lower fine limits defined based on a transition point identified
during the rough HBP test. Additionally or alternatively, the
microcontroller 60 may be configured to identify a rough transition
point based on the response characteristic associated with the
first and second HBP pulses separated by the at least one rough
energy adjustment and refine the rough transition point to a fine
transition point based on the response characteristic associated
with the third and fourth HBP pulses separated by the at least one
fine energy adjustment.
[0092] In the present example, the above operations are performed
by an implantable medical device having a housing that includes the
memory and the one or more processors, the housing configured to be
coupled to the RA electrode and HRIS electrode. Optionally, the IMD
may have at least a portion of the one or more processors, while an
external device has at least a portion of the one or more
processors. The IMD and external device both perform at least a
portion of the identifying, calculating, analyzing, adjusting,
monitoring, and managing operations.
[0093] Advantageously, the operating parameters of the implantable
device 10 may be non-invasively programmed into the memory 94
through a telemetry circuit 100 in telemetric communication with
the external device 102, such as a programmer, trans-telephonic
transceiver, or a diagnostic system analyzer. The telemetry circuit
100 is activated by the microcontroller 60 by a control signal 106.
The telemetry circuit 100 advantageously allows intracardiac
electrograms and status information relating to the operation of
the device 10 (as contained in the microcontroller 60 or memory 94)
to be sent to the external device 102 through an established
communication link 104.
[0094] In the preferred embodiment, the stimulation device 10
further includes a physiologic sensor 108, commonly referred to as
a "rate-responsive" sensor because it is typically used to adjust
pacing stimulation rate according to the exercise state of the
patient. However, the physiologic sensor 108 may further be used to
detect changes in cardiac output, changes in the physiological
condition of the heart, or diurnal changes in activity (e.g.,
detecting sleep and wake states). Accordingly, the microcontroller
60 responds by adjusting the various pacing parameters (such as
rate, stimulation delays, etc.) at which the atrial and ventricular
pulse generators 70, 72 generate stimulation pulses.
[0095] A common type of rate responsive sensor is an activity
sensor, such as an accelerometer or a piezoelectric crystal, which
is mounted within the housing 40 of the stimulation device 10.
Other types of physiologic sensors are also known, for example,
sensors which sense the oxygen content of blood, respiration rate
and/or minute ventilation, pH of blood, ventricular gradient, etc.
However, any suitable sensor may be used which is capable of
sensing a physiological parameter which corresponds to the exercise
state of the patient. The type of sensor used is not critical to
the present disclosure and is shown only for completeness.
[0096] The stimulation device 10 additionally includes a battery
110 which provides operating power to all of the circuits shown in
FIG. 3. For the stimulation device 10, which employs shocking
therapy, the battery 110 must be capable of operating at low
current drains for long periods of time, and then be capable of
providing high-current pulses (for capacitor charging) when the
patient requires a shock pulse. The battery 110 must also have a
predictable discharge characteristic so that elective replacement
time can be detected. Accordingly, the device 10 preferably employs
lithium/silver vanadium oxide batteries, as is true for most (if
not all) current devices.
[0097] The device 10 is shown in FIG. 3 as having an impedance
measuring circuit 112 which is enabled by the microcontroller 60
via a control signal 114. The known uses for an impedance measuring
circuit 112 include, but are not limited to, lead impedance
surveillance during the acute and chronic phases for detecting
proper lead positioning or dislodgement; detecting operable
electrodes and conductors; and automatically switching to an
operable pair if dislodgement or electrical disruption occurs;
measuring respiration or minute ventilation; measuring thoracic
impedance for determining shock thresholds; detecting when the
device has been implanted; measuring stroke volume; and detecting
the opening of heart valves, etc. The impedance measuring circuit
112 is advantageously coupled to the switch 74 so that any desired
electrode may be used.
[0098] In the case where the stimulation device 10 is intended to
operate as an implantable cardioverter/defibrillator (ICD) device,
it must detect the occurrence of an arrhythmia, and automatically
apply an appropriate electrical shock therapy to the heart aimed at
terminating the detected arrhythmia. To this end, the
microcontroller 60 further controls a shocking circuit 116 by way
of a control signal 118. The shocking circuit 116 generates
shocking pulses of low (for example, up to 0.5 joules), moderate
(for example, 0.5-10 joules), or high energy (for example, 11-40
joules), as controlled by the microcontroller 60. Such shocking
pulses are applied to the patient's heart 12 through at least two
shocking electrodes, and as shown in this embodiment, selected from
the left atrial coil electrode 28, the right ventricular coil
electrode 36, and the SVC coil electrode 38. As noted above, the
housing 40 may act as an active electrode in combination with the
right ventricular electrode 36, or as part of a split electrical
vector using the SVC coil electrode 38 or the left atrial coil
electrode 28 (i.e., using the right ventricular electrode 36 as a
common electrode).
[0099] Cardioversion shocks are generally considered to be of low
to moderate energy level (so as to minimize pain felt by the
patient), and/or synchronized with an R-wave and/or pertaining to
the treatment of tachycardia. Defibrillation shocks are generally
of moderate to high energy level (i.e., corresponding to thresholds
in the range of 5-40 joules), delivered asynchronously (since
R-waves may be too disorganized), and pertaining exclusively to the
treatment of fibrillation. Accordingly, the microcontroller 60 is
capable of controlling the synchronous or asynchronous delivery of
the shocking pulses.
[0100] The device 10 includes two separate connection terminals,
one for each of the two flexible conductors that are further
connected to switch 74. The two flexible conductors can then be
selectively connected as desired to the HIS sensing circuit 83,
ventricular pulse generator 72, or impedance measuring circuit 112
for sensing, stimulating, and measuring tissue impedance at the
site of the HIS bundle. Using the lead 21, it is possible to effect
stimulation with the HIS tip electrode 16 and the HIS ring
electrode 19, and to effect sensing with the conductive surfaces.
According to another design, the sensing is affected by the
conductive surfaces and stimulation is affected by means of the
leads other than the HIS lead, for example the right atrial lead
20. For more details regarding a heart electrode equipped with
multiple conductive surfaces, reference is made to U.S. Pat. Nos.
5,306,292 and 5,645,580, which are incorporated herein by
reference. The HIS tip electrode 16 may be secured in the HIS
bundle thereby anchoring the HIS tip electrode 16 in contact with
the HIS bundle tissue. The electrogram signal arising from the HIS
bundle can then be received by the HIS sensing circuit 83. A bypass
filter (not shown) that allows signals ranging from 30-200 Hz to be
received may be used to block the high frequency alternating
current excitation signals.
Methods and Systems to Avoid Over Sensing Atrial Activity
Components
[0101] Various embodiments are described hereafter for avoiding
oversensing of atrial activity components. It should be recognized
that the various embodiments may be implemented dynamically within
an external or implantable medical device. Embodiments may be
implemented continuously and/or based on predetermined criteria in
an automatic manner by an IMD. Additionally or alternatively, an
external programmer may instruct an IMD to initiate the
measurements and calculations described herein. Additionally or
alternatively, various embodiments may be implemented entirely, or
in part, by an IMD, a local external device, a programmer and/or
remote server. For example, an IMD may receive an instruction from
a local external device, a programmer and/or remote server to
initiate collecting CA signals and/or other information calculated
from the CA signals as described herein. The CA signals and/or
subsequent calculations may be streamed to a local external device,
server and/or programmer. The data streamed from the IMD may be
processed on a local external device, programmer, and/or remote
server to automatically set HBP parameter settings, including but
not limited to the component sensitivity profile, VE sensitivity
profile, AOA window length, PAVP window length and the like.
[0102] In the following discussion of the methods for managing
sensing, at least some operations are described with respect to CA
signals generally. It is understood that the corresponding
operations may be performed on a beat by beat basis and/or may be
performed utilizing an ensemble of a predetermined number of beats.
Additionally or alternatively, the operations described herein may
be performed over multiple beats during one respiration cycle
(e.g., 8-10 beats) or more than one respiration cycles. By
utilizing an ensemble of beats over a respiration cycle,
embodiments account for variations between beats at different
phases in the respiration cycle.
[0103] FIG. 4A illustrates a process for implementing an atrial
over sensing (AOS) set up test in accordance with embodiments
herein. At 402, the one or more processors initiate an AOS set up
test. The AOS set up test is configured to detect AOS using atrial
timing on an RA sensing channel and the time separation of atrial
and ventricular events as detected over the HIS sensing channel
during an intrinsic AV conduction. The AOS set up test is generally
run while the IMD is operating in a DDD mode as the test utilizes
atrial sensed or atrial paced events to initiate the AOA window for
which the CA signals received over the HIS sensing channel are
analyzed for AA components. As described hereafter in connection
with the operations of FIG. 4A, during the AOS set up test, atrial
and ventricular event amplitudes are measured over the HIS sensing
channel.
[0104] At 404, the one or more processors extend the sensed/paced
atrioventricular delay (AVD) by a preprogrammed or automatically
determined amount to allow intrinsic ventricular activation without
intervention of a HIS pacing event. For example, the AVD may be
extended up to 300 ms following an atrial sensed event or the AV
delay may be extended up to 350 ms following an atrial paced event.
If an intrinsic AV conduction is not detected, HIS pacing is
delivered when the AVD times out. At 404, the one or more
processors further set the sensitivity for the HIS sensing channel
to have a high sensitivity level (e.g., 0.5 mV).
[0105] At 406, the one or more processors initiate a beat counter
(e.g., n=1). The beat counter is utilized to keep track of a total
number of beats, from which a subset may be declared to be AA
beats.
[0106] At 408, the one or more processors detect an atrial sensed
or paced event over the RA sensing channel and initiate an AOA
window. The one or more processors search the CA signals obtained
over the HIS sensing channel during the AOA window for an AA
component. As a nonlimiting example, the AOA window may be set to
100 ms when the atrial event represents an atrial sensed event, and
the AOA window may be set to 160 ms when the atrial event
represents an atrial paced event. Additionally or alternatively,
different durations may be programmed for the AOA window duration,
such as in connection with different sensing configurations (e.g.,
bipolar versus unipolar sensing).
[0107] At 410, the one or more processors determine whether an AA
component was detected over the HIS sensing channel during the AOA
window. For example, the presence of an AA component may be
declared when an amplitude of the CA signals, sensed over the HIS
sensing channel, cross a sensitivity profile (referred to herein as
a "component sensitivity profile", or "AO sensitivity profile")
that is defined for the HIS sensing channel during the AOA window.
By way of example, the component sensitivity profile may represent
a preprogrammed sensitivity threshold that is not change over time.
For example, the AO sensitivity profile may be set to a constant AO
sensitivity threshold that corresponds to a percentage (e.g., 150%)
of a maximum prior measured AA peak.
[0108] Additionally or alternatively, the component sensitivity
profile may vary over time, such as described in the '351
application which describes various parameters that may be adjusted
to define a sensitivity profile. As a nonlimiting example, an AA
component may be declared when the CA signal exhibits an amplitude
that exceeds a component sensitivity profile/threshold of 0.5 mV
during the AOA window. It is recognized that the operation to
detect an AA component during an AOA window is separate and
distinct from the operation of detecting ventricular events over
the HIS sensing channel.
[0109] Detection of ventricular events is based on CA signals that
follow the AOA window and is based on a VE sensitivity profile
which may be the same as or different from the AO sensitivity
profile utilized to search for AA components during the AOA window.
For example, the VE sensitivity profile may be manually programmed
to 0.5 mV or another value based on a peak of prior detective
ventricular events.
[0110] When an AA component is detected to exceed the AO
sensitivity profile, the process declares an AO event to have
occurred, and flow moves to 412. When an amplitude of the CA
signals during the AOA window does not exceed the AO sensing
profile, the process determines that an AA component is not
detected, and flow moves to 414.
[0111] At 412, the one or more processors determine and record a
A/AA interval between the paced or sensed event (as denoted by an
atrial marker) and a COI within the AA component. For example, the
A/AA interval may be between onset or a peak of the atrial paced or
sensed event (as denoted by an atrial marker) and onset, peak or
termination of the AA component. Additionally or alternatively, an
A/AA period may be measured as the time delay from the atrial
marker to the end of the AA component. At 412, the one or more
processors further identify an amplitude of the AA component as a
second COI (e.g., the peak amplitude of the AA component). As
explained hereafter, the A/AA interval and the AA peak are recorded
in connection with each AA component identified at 410 and
subsequently used in connection with the consistency check of FIG.
5. The operations of FIG. 4A are repeated to build a set of AA
beats with corresponding A/AA intervals and AA peaks. At the end of
the operations of FIG. 4A, the AA beats represent candidate AO
beats as the AA beats have not yet been analyzed for consistency
and determined to represent resultant AO beats.
[0112] In accordance with new and unique aspects herein, it has
been recognized that the delay from an atrial paced or sensed event
to a COI within the AA component (e.g., the peak of an AO event is
very consistent beat by beat). Accordingly, at 412, for each AA
beat, the A/AA interval is measured and subsequently checked for
consistency (in accordance with the operations of FIG. 5). As
explained below in connection with FIG. 5, erroneously detected AA
beats or outlier AA beats are excluded. A nonlimiting example of
outlier AA beats may arise due to premature ventricular
contractions (PVCs) a risk of atrial over sensing is confirmed when
a desired number (e.g., two or more) effective atrial over sensed
the beats are detected over one or more atrial over sensed beats
are detected where the amplitude of the AA component is within a
defined window (e.g., 0.5 mV to 1.0 mV).
[0113] At 414, the one or more processors record a characteristic
of interest from the ventricular event, such as the amplitude of
the ventricular event following the AOA window.
[0114] At 416, the one or more processors determine whether a
desired number of beats have been analyzed for AA components (e.g.,
five beats). If not, flow moves to 418 where the count of the
number of beats is incremented (e.g., n+n+1). Next flow moves to
408 where the AOA window is reset in connection with the next
sensed or paced atrial event. The operations at 408-416 are
repeated for desired number of beats, after which flow moves to
420. As one example, the operations at 408-416 may be repeated to
collect information concerning a number of atrial sensed beats in
order to characterize characteristics of interest in the AA
components following atrial sensed beats. As another example, the
operations at 408-416 may be repeated to collect information
concerning a number of atrial paced beats in order to characterize
characteristics of interest in the AA components following atrial
paced beats.
[0115] At 420, the one or more processors determine whether atrial
over sensing has been identified. For example, the one or more
processors may merely determine if, for any or a select number of
the beats, the process detected an AA component during the AOA
window. Additionally or alternatively, the one or more processors
may implement the various operations and processes described in the
patent applications and patents referenced and incorporated herein
to determine whether atrial over sensing has been identified. When
atrial over sensing is not identified at 420, flow moves to
422.
[0116] At 422, the one or more processors determined that atrial
oversensing has not been identified utilizing the present set of AO
parameters. In response thereto, the AO process may be disabled.
Additionally or alternatively, the parameters of the AO process may
be modified and the operations of FIG. 4A repeated. For example,
when the AO process is disabled, the VE sensitivity profile may
revert to a user programmed VE sensitivity profile (e.g., such is
set to a minimum allowed sensitivity, 0.5 mV and the like).
[0117] At 420, when an atrial over sensing is identified, flow
moves to 424.
[0118] At 424, the one or more processors perform an AO consistency
check, as explained herein in accordance with embodiments herein.
Depending on the outcome at 424, flow moves to either 426 or
returns to 422.
[0119] At 426, the one or more processors identify AO parameters to
be utilized by the AO process. For example, the AOA window may be
set to have a duration that is a function of one or more prior
measured a/AA intervals. For example, the AOA window following an
atrial sensed event, may be set to have a duration corresponding to
the longest prior interval from an atrial sensed event to an AA
component (AS/AA interval) times a multiple (e.g., 1.25). As
another example, the AOA window following an atrial paced, may be
set to have a duration corresponding to the longest prior interval
from an atrial paced event to an AA component (AP/AA interval)
times a multiple (e.g., 1.25). For example, the AO sensitivity
profile may be set to a constant AO sensitivity threshold that
corresponds to a percentage (e.g., 150%) of a maximum prior
measured AA peak. For example, the VE sensitivity profile may be
manually programmed to 0.5 mV or another value based on a peak of
prior detective ventricular events.
[0120] Among other things, the one or more processors apply one or
more consistency criteria to the AA beats to determining a number
of the AA beats that are indicative of consistent AO. Based on the
number of AA beats indicative of consistent AO, the one or more
processors perform at least one of an adjustment of an AO parameter
utilized by the AO process (at 426) or disabling the AO process (at
422). Thereafter, the one or more processors continue to manage HIS
bundle pacing based on the ventricular event.
[0121] It is desirable to utilize the AO avoidance process when a
set up test detects a risk of atrial over sensing. Optionally, the
AA peaks and the A/AA intervals associated with effective AA beats
may be displayed to a user may be utilized to program parameters of
the AO process automatically. Additionally or alternatively, when
atrial over sensing occurs, amplitudes of the ventricular signal
and the V/AA amplitude ratio may be displayed to the user. When no
atrial over sensing beats are detected, the AO process may be
disabled and the VE sensitivity may be programmed by the user.
[0122] FIG. 4B illustrates example CA signals collected over atrial
and HIS sensing channels and analyzed in accordance with
embodiments herein. The atrial EGM 450 represents the CA signals
collected over the atrial sensing channel, while the HIS EGM 452
represents the CA signals collected over the HIS sensing channel.
An atrial sensed (AS) or atrial paced (AP) event 454 is denoted at
the marker "AS or AP" 456 (over a marker channel 458) corresponding
to the vertical dashed line. The AS or AP event 454 is detected at
402 (FIG. 4A), followed by the start of the AOA window at 408.
During the AOA window, the HIS EGM 452 is analyzed based on an AO a
sensitivity profile 460 to detect AA component 462 (at 410). At
412, the one or more processors record an A/AA interval 464 between
an onset of the AS/AP event 454 and an end of the AA component 462.
At 412, the one or more processors also record an AA peak (as
denoted at 466 in connection with the next AA component 468.
[0123] The AA components 462, 468 are followed by ventricular
events 470, 472 within the HIS EGM. The ventricular events 470, 472
are detected and assigned markers VS at 478, 479. FIG. 4B further
illustrates, within the atrial EGM 450, examples of the ventricular
event components 474, 476 that appear over the atrial sensing
channel.
[0124] The CA signals, such as atrial and HIS EGM 450, 452, are
obtained for multiple beats over atrial and HIS sensing channels
utilizing corresponding electrodes located in the RA and proximate
to the HIS. The atrial over sensing process of FIG. 4A analyzes the
atrial and HIS EGM 450, 452 over the series of beats during a
corresponding AOA windows following AS or AP events in search of AA
components to identify AA beats.
[0125] Optionally, the process of FIG. 4A may be implemented
without extending the AVD at 404. Instead, a normal AV delay may be
utilized, and only atrial signal amplitude is measured over the HIS
channel. For example, the process would measure atrial signal
amplitude in the HIS channel, such as within either the 100/160 ms
after an atrial sensed/paced event search window, or before the
programmed AV delay, whichever of these two is smallest. In the
present example, the process would not measure the atrial
oversensing signal on the HIS channel delay, given that pacing by
the programmed AV delay could overlap with the end of the atrial
signal delay. The ventricular signal amplitude may be measured over
the HIS channel during normal ventricular sensing with the AOA
process enabled or disabled.
[0126] FIG. 4C illustrates example CA signals collected over atrial
and HIS sensing channels and analyzed in accordance with
embodiments herein. The atrial EGM 480 represents the CA signals
collected over the atrial sensing channel, while the HIS EGM 42
represents the CA signals collected over the HIS sensing channel.
An atrial sensed (AS) or atrial paced (AP) event 484 is denoted at
the marker "AS or AP" (over a marker channel) corresponding to the
vertical dashed line. The AS or AP event is detected at 402 (FIG.
4A), followed by the start of the AOA window 486 at 408.
[0127] The AOA process (as described further in the above
referenced and incorporated patents and applications) may be
implemented utilizing a reduced sensitivity profile when searching
for AA components over the HIS channel during the AOA window. As
explained herein and elsewhere, reducing the AO sensitivity profile
is utilized to avoid atrial over sensing and ensure proper
ventricular sensing on the HIS channel. For example, during the AOA
window 486, the HIS EGM 42 is analyzed based on an AO sensitivity
profile 488 to detect AA component 490 (at 410). At 412, the one or
more processors record an AA peak for the corresponding AA beat.
Following the AOA window 486, the sensitivity profile is shifted
from the AO sensitivity profile 488 to a VE sensitivity profile
492. The VE sensitivity profile 492 is utilized to identify
ventricular events 496. The AO sensitivity profile 488 utilizes a
sensitivity threshold that is set to a higher level, relative to a
sensitivity threshold utilized during the VE sensitivity profile
492.
[0128] Optionally, the AO sensitivity and AOA window may be
programmed manually by the user or automatically using the
measurements from prior detection of atrial over sensing.
[0129] FIG. 5 illustrates a process for implementing an AO
consistency check in accordance with embodiments herein. For
example, the AO consistency check may be implemented at 424 in FIG.
4. At 502, the one or more processors determine whether a number of
detected AA beats exceeds a predetermined criteria, such as a
desired percentage of the total number of beats tested. For
example, the one or more processors may determine whether a percent
of the tested beats were initially declared to represent AA beats
that are potentially indicative of AO. When the number of AA beats
relative to the total number of tested beats exceeds the threshold,
flow moves 504. Alternatively, when the number of AA beats,
relative to the total number of beats, falls below the threshold,
flow moves to 514.
[0130] At 504-508, the one or more processors apply a consistency
criteria to the AA beats to determine a number of the AA beats that
are indicative of consistent AO.
[0131] At 504, the one or more processors identifies the AA beats,
from at least a portion of the AA beats determined in connection
with FIG. 4A, that have an A/AA interval that satisfies a first
consistency criteria. For example, the one or more processors may
determine a mathematical combination (e.g., median or mean) for the
A/AA intervals for the set of AA beats. Based on the mathematical
combination, the one or more processors determine limits or a
desired range to distinguish acceptable AA beats from outlier AA
beats. The one or more processors identify a first subset of the AA
beats that have an A/AA interval that meets a first consistency
criteria, namely the number of AA beats that have an A/AA interval
that falls within a desired range or limits of a reference level.
For example, the one or more processors may identify the first
subset of the AA beats that have an A/AA interval that is within
0.5 to 1.5 of a median A/AA interval. The median A/AA interval may
be preprogrammed or automatically determined from the operations at
FIG. 4A. The first subset of beats within the desired range/limits
of the A/AA interval median are maintained as a first count of
candidate AA beats.
[0132] At 506, the one or more processors identify the AA beats,
from at least a portion of the AA beats determined in connection
with FIG. 4a, that have a peak of the AA component (AA peak) that
satisfies a second consistency criteria. For example, the one or
more processors apply the consistency criteria to identify a subset
of the AA beats, for which the AA peak is within the second
connection criteria. For example, the one or more processors may
determine a mathematical combination (e.g., median or mean) for the
AA peaks for the set of AA beats. Based on the mathematical
combination, the one or more processors determine limits or a
desired range to distinguish acceptable AA beats from outlier AA
beats. The one or more processors identify a second subset of the
AA beats that have an AA peak that meets a second consistency
criteria, namely the number of AA beats that have an AA peak that
falls within a desired range or limits of a reference level. For
example, the one or more processors may identify the second subset
of the AA beats that have an AA peak that is within 0.25 to 1.75 of
the median AA peak. The median AA peak amplitude may correspond to
the median of the peaks for all of the AA beats. The median AA peak
may be preprogrammed or automatically determined from the
operations at FIG. 4A. The second subset of beats within the
desired range/limits of the AA peak median are maintained as a
second count of candidate AA beats.
[0133] At 508, the one or more processors count the number of beats
in the first subset and the second subset that satisfy the first
and second criteria. When the number of beats that satisfy one or
both of the first and second criteria exceeds a threshold (e.g.,
two or more beats), flow moves to 512. Alternatively, when the
number of beats that satisfy the one or both of the first and
second criteria for below the threshold, flow moves 510.
[0134] At 512, the one or more processors declare the current AO
process to be operating in an effective manner and sets the
parameters of the AO process (utilized in connection with FIG. 4)
to be the resultant AO process parameters. For example, the one or
more processors may adjust an AO parameter for at least one of i) a
start time for the AOA window, a duration for the AOA window, or an
AO sensitivity profile utilized to analyze the CA signals over the
HIS sensing channel during the AOA window. At 510, the one or more
processors determined declare the current AO process to be
operating in an inconsistent manner and accordingly disables the AO
process from further use until adjustments are made or for a
predetermined period of time.
[0135] Returning to 502, when the number of detected AA beats falls
below the threshold, flow moves to 514. At 514, the one or more
processors analyze the peaks of the AA beats. At 514, the one or
more processors compare the peaks to a predetermined range, such as
0.5 mV to 1.0 mV. At 516, the one or more processors determine
whether the number of AA beats that have an AA peak within the
predetermined range satisfy a criteria (e.g., greater than or equal
to one). When a sufficient number of the number of AA beats have an
AA peak within the predetermined range, flow moves to 512 (where
the present AO parameters are utilized). Alternatively, when too
few AA beats have AA peaks within the predetermined range, flow
moves 510 (where the AO process is disabled).
[0136] In accordance with the foregoing, the operations at 502-516
apply consistency criteria to the AA beats to determine a number of
the AE beats that are indicative of consistent AO. The operations
at 504, 506 and 514, identify a subset of the AA beats, for which
one or more characteristic of interest of the AA components fall
within limits. At 504, the limits represent a range surrounding a
mathematical combination (e.g., mean value) for the A/AA interval
for the set of AA beats. At 506, the limits represent a range
surrounding a mathematical combination (e.g., mean value) for the
AA peaks for the set of AA beats. At 514, the limits represent a
predetermined range for the AA peak. At 508 and 516, the process
determines whether a number of beats in the subset of the AA beats
is indicative of consistent AO.
Automatic Pacing Threshold Testing
[0137] New and unique aspects herein relate to stimulation devices
and corresponding methods related to HIS bundle pacing. Among other
things, the present methods and devices provide for automatic
determination of HIS bundle capture thresholds, for configuring
stimulation devices based on determined capture thresholds, for
identifying different capture types in response to application of
pacing impulses of varying energies, and other related features and
functions. Aspects may be implemented in any suitable stimulation
device including, but not limited to, implantable dual chamber and
multi-chamber cardiac stimulation devices as well as external
programming units for such stimulation devices. Certain cardiac
pacemakers and defibrillators incorporate a pacing lead in the
right ventricle and may also include a second lead in the right
atrium. High-burden right ventricle apical pacing may contribute to
the development of pacing-induced cardiomyopathy and symptoms
associated with heart failure (HF). Several pathophysiologic
mechanisms have been implicated in the development of
pacing-induced HF, each of which likely stems from
non-physiological electrical and mechanical activation patterns
produced by right ventricle pacing. HIS bundle pacing (HBP) has
been shown to restore physiological activation patterns by
utilizing a patient's intrinsic conduction system, even in the
presence of bundle branch block. HBP has also been shown to provide
significant QRS narrowing, with improved ejection fraction.
[0138] Another possible clinical application of HBP is cardiac
resynchronization therapy (CRT). Conventional CRT systems include
pacing from both a right ventricular and a left ventricular lead
and have been shown to be most effective for patients exhibiting a
wide QRS complex and left bundle branch block. HBP has also been
shown to be effective at narrowing the QRS complex in patients with
left bundle branch block, likely due to restoration of conduction
through the Purkinje fibers, which include right and left bundle
fibers that are longitudinally dissociated. Therefore, what is
thought of as left bundle branch block, can be a result of a
proximal blockage within the HIS bundle that eventually branches to
the left bundle. By pacing the HIS bundle distal to the blockage, a
normalized QRS complex can be achieved in some patients.
Theoretically, this pacing mode may provide even better results
than known CRT treatments, as activation propagates rapidly through
natural conduction pathways.
[0139] Depending on electrode position, pacing output, patient
physiology, and other factors, pacing impulses delivered to the HIS
bundle may result in capture of different cardiac tissue. As used
herein, the term "capture" refers to when a pacing impulse has
sufficient energy to depolarize cardiac tissue, thereby causing the
depolarized cardiac tissue to contract. In the context of HBP,
pacing of the HIS bundle will generally result in one of four
capture scenarios: non-selective HIS bundle capture, selective HIS
bundle capture, myocardium-only capture, or loss of capture (or
non-capture). Non-selective capture refers to when a pacing impulse
results in capture of both the HIS bundle and the local myocardium
surrounding the HIS bundle. Because of the simultaneous
depolarization of the HIS bundle and myocardium, non-selective HIS
bundle capture generally results in a combined or condensed
electrical response as compared to normal heart activity in which
the HIS bundle and myocardium are depolarized sequentially,
Accordingly, non-selective HIS bundle capture may be characterized
by a shortened delay between application of the pacing impulse and
ventricular depolarization (e.g., on the order of 20 ms) because
the myocardial depolarization propagates immediately without
exclusively traveling through the HIS-Purkinje system.
Nevertheless, because the HIS bundle is stimulated and captured,
the QRS duration is similar to the native QRS duration but may be
slightly longer due to the myocardial excitation (e.g., 70-120 ms).
In contrast, selective HIS bundle capture refers to exclusive
capture of the HIS bundle without depolarization of the surrounding
myocardial tissue. With selective HIS bundle capture, the stimulus
to ventricular depolarization interval is virtually the same as the
native delay between HIS bundle activation and subsequent
ventricular depolarization and the QRS duration is essentially
identical to the native QRS duration. In myocardium-only capture,
the tissue surrounding the HIS bundle is captured without capturing
the HIS bundle itself, resulting in slow or delayed signal
conduction and activation. Finally, loss of capture generally
refers to circumstances in which the applied stimulus is
insufficient or otherwise unable to elicit a response. In such
cases, backup pacing may be applied. For patients with branch
bundle block or similar conduction disorders, the foregoing capture
types may be further characterized by whether they result in
correction of the conduction disorder. For example, a pacing
impulse may result in any of non-selective HIS bundle capture with
correction, non-selective HIS bundle capture without correction,
selective HIS bundle capture with correction, or selective HIS
bundle capture without correction.
[0140] While both selective and non-selective HIS bundle capture
may be used to improve cardiac function, selective HIS bundle
capture is generally preferred as the corresponding response more
closely approximates natural heart function. However, due to the
complexity and dynamic nature of certain cardiomyopathies and
cardiac anatomies, selective HIS bundle capture may not be possible
or, if possible, at one time, may no longer be possible as a
patient's condition changes over time. Moreover, a patient's
condition may also progress such that HIS bundle capture (whether
selective or non-selective) may become unavailable and, as a
result, direct ventricular pacing may be required.
[0141] In light of the foregoing, this methods and apparatuses are
directed to optimizing HBP. More specifically, this disclosure
describes stimulation devices capable of HBP and processes that may
be implemented by such stimulation devices to initialize device
settings. To do so, stimulation devices or a programming unit in
communication with the stimulation device executes a capture
threshold test in which response data is collected for a range of
pacing impulse energies (e.g., a range of pacing impulse voltages,
pacing impulse pulse widths, or combinations thereof). In certain
implementations, the response data may include unipolar, bipolar,
or both unipolar and bipolar responses (e.g., electrograms)
recorded and stored by the stimulation device or programming unit.
Transitions between capture types are then identified by analyzing
changes in response characteristics for the various pacing impulse
energy settings that were tested. Based on the number of observed
transitions, the nature of the changes indicating the transitions
(e.g., how the particular response characteristics change), an
initial capture type, and/or other similar factors, the capture
pacing impulse energies may then be assigned a capture type. The
stimulation device or programming unit may then identify capture
thresholds based on the pacing impulse energies at which
transitions between different capture types occur and calibrate or
adjust stimulation device settings to the best available pacing
impulse energy (e.g., the lowest energy (the lowest voltage, pulse
width, or combination thereof) for which HBP capture is achieved)
according to the assigned capture types and/or identified capture
thresholds. By relying on response data obtained from the patient,
the settings of the stimulation device are specifically tailored to
the individual patient and, as a result, improve both pacing
reliability and overall life and function of the stimulation
device.
[0142] Permanent HIS bundle pacing (HBP) has been proven feasible
by delivering pacing stimuli at the HIS bundle with an implantable
pacing lead and pacemaker. HBP activates the heart through the
native HIS-Purkinje conduction system, thus offering the most
physiologic pacing approach to correcting electrical dyssynchrony,
among other things. HBP has also emerged as a safe alternative to
conventional pacemaker therapy by exhibiting a range of clinical
and electrophysiological advantages over conventional pacemaker
therapy.
[0143] In conventional right ventricle (RV) pacing applications,
implantable pacemakers may execute algorithms that automatically
measure capture thresholds and apply a small safety margin to
ensure RV capture. Such pacemakers may also include algorithms that
automatically detect loss of capture (LOC). Among other things,
such algorithms may provide backup pacing, adjust pacing output to
ensure capture, or trigger automatic capture threshold searching
when LOC recovery pacing output is too high.
[0144] However, conventional pacemaker-based algorithms are
generally inappropriate and not readily adaptable for use in HBP
applications due to differences in the response of the HIS bundle
and local surrounding myocardium to pacing (as compared to other
cardiac tissue) and other related complexities associated with HBP.
Therefore, existing automatic capture threshold testing approaches
implemented in RV pacing applications generally do not work for HBP
applications. Accordingly, a new capture management approach is
required for HBP applications. Such an approach should preferably
result in HBP with minimal pacing output to improve overall battery
and device life, among other things.
[0145] Pacing of the HIS bundle may result in a range of capture
scenarios depending on various factors including, among other
things, the physiology of the heart, the energy of the pacing
impulse, whether the patient has any cardiac conditions affecting
conduction, and the like. For example and as previously discussed,
for patients with healthy conduction system (e.g., as exhibited by
a narrow/normal QRS width), pacing of the HIS bundle may result in
one of four general scenarios. First, selective capture may occur
in which only the HIS bundle is captured. By capturing only the HIS
bundle, subsequent conduction along the HIS/Purkinje system is the
same or substantially similar to normal sinus beats. Second,
non-selective capture may occur in which both the HIS bundle and
local myocardium are captured. The resulting ventricular conduction
is substantially similar to normal sinus beats but capture of the
local myocardium activation adds a small delta wave prior to the
main QRS complex. However, because the conduction speed of
HIS-Purkinje system is much faster than that of the myocardium,
there is little to no difference in clinical outcome between
selective and non-selective HIS bundle capture. Third,
myocardium-only capture may occur in which the myocardium is
captured without capturing this HIS bundle, resulting in relatively
slow/delayed activation of the ventricles. Finally, a loss of
capture may occur in which neither the myocardium nor the HIS
bundle is captured. For patients with bundle branch block (BBB) or
other similar conduction-related issues (e.g., as exhibited by a
wide/long QRS duration), each of the selective and non-selective
cases may be further classified as resulting in a response with or
without correction of the BBB.
[0146] Conventionally, the HBP responses discussed above and the
corresponding capture thresholds are identified and diagnosed
in-clinic by healthcare professionals using relatively complicated
electrocardiogram systems, such as 12-lead surface ECGs. HBP pacing
devices are then configured to implement HBP according to the
capture thresholds identified during such testing. In addition to
such approaches being time-consuming and complicated, if subsequent
adjustments to a device's settings are required, a patient
typically has to revisit the clinic for the healthcare professional
to repeat the capture threshold test. Moreover, to account for
changes that may occur between such visits, healthcare
professionals may set pacing settings to include a large safety
margin, e.g., by adjusting impulse energy settings well above that
required to achieve a desired capture result. While such safety
margins may be sufficient to account for changes when they occur,
such over-stimulation is otherwise inefficient, leading to reduced
battery and device life.
[0147] Devices and methods are provided herein to address the
various issues identified above, among others. More specifically,
the present disclosure is directed to methods of performing
automatic capture threshold testing for determining efficient
settings for stimulation devices for implementing HBP. In certain
implementations, the automatic capture threshold testing methods
described herein may be executed by the stimulation device itself.
Notably, such a device-based approach eliminates or reduces the
need for a patient to revisit a clinic or healthcare professional
to adjust settings of their stimulation device. Moreover, the
device-based approach enables the device to execute the capture
threshold test itself (e.g., periodically, in response to a loss or
change in capture, etc.) and to dynamically adjust the settings of
the stimulation device between clinic visits. By doing so, the need
for a significant safety margin is reduced and the stimulation
device may be operated in a more efficient manner as compared to
conventional pacing approaches.
[0148] While the example implementations of the present disclosure
focus primarily on implementation in stimulation devices and
implementation in the stimulation device carries certain
advantages, it should be appreciated that the methods discussed
herein may also be implemented by devices capable of communicating
with a stimulation device. For example, the process methods of
performing automatic capture threshold testing discussed herein may
be implemented in programmers or similar devices adapted to
monitor, receive data from, and configure stimulation devices.
[0149] Systems and methods according to the present disclosure
leverage observed changes in the heart's response to different
pacing impulse energies resulting to identify capture thresholds
and corresponding pacing settings. For example, in one
implementation, pacing impulses are applied using a range of pacing
impulse energies and one or both of a unipolar and bipolar
electrogram (EGM) are measured after each impulse using the HIS
bundle lead. The collected response data is then analyzed to
determine changes in characteristics of the measured responses
indicative of a change in capture type between pacing impulse
energy settings. The stimulation device may then be automatically
configured based on the results of the analysis to achieve the best
available capture scenario using the lowest pacing impulse
energy.
[0150] For example, in one implementation, the stimulation device
may apply pacing impulses at different energies (e.g., starting at
maximum pacing impulse energy and gradually decrementing the pacing
impulse energy until a loss of capture occurs) and may record one
or both of a unipolar and a bipolar EGM for each pacing impulse
energy. The stimulation device may then analyze the data to
determine when changes in certain characteristics of the unipolar
and bipolar responses have occurred. For example, in one
implementation, each of a unipolar width and a bipolar stim-to-peak
time (as measured from the unipolar and bipolar EGMs, respectively)
may be measured and changes (e.g., a relative change exceeding
about 10%) in one or both of the unipolar width and the
stim-to-bipolar peak time may be used to identify when a transition
between capture types has occurred. As discussed below in further
detail, in at least certain implementations of the present
disclosure, a capture type may then be associated with each pacing
impulse energy based on the number of identified transitions, an
initial capture type (e.g., a capture type achievable using a
relatively high pacing impulse energy), known information regarding
the patient (e.g., whether the patient has a branch bundle block or
similar conduction-related condition), and other information. The
stimulation system may then select a preferred pacing impulse
energy which, in certain cases, is the minimum pacing impulse
energy resulting in a particular capture type (e.g., selective
capture, if possible, in patients with normal conduction or
selective capture with correction in patients exhibiting branch
bundle block or similar conduction-related conditions).
[0151] Although unipolar width and bipolar stim-to-peak time are
used as examples, it should be appreciated that other
characteristics of the response may be used to identify transitions
between capture types. For example, and without limitation,
unipolar width may be substituted with another response
characteristic indicative of total ventricular activation time.
Similarly, bipolar peak-to-stim time may be substituted with any
suitable response characteristic indicative of the local activation
time relative to pacing of the HIS bundle. For example, the bipolar
peak-to-stim time may be substituted with a metric for
stim-to-onset time, such as unipolar stim-to-onset time. Moreover,
either of unipolar or bipolar response data may be used for each
response characteristic.
[0152] Pacing impulse energy is generally used herein to describe
the energy of a given pacing impulse. Pacing impulse energy may be
determined as a function of the voltage and the duration (e.g., the
pulse width) of the pacing impulse. Accordingly, to the extent the
present disclosure discusses modifying pacing impulse energy, such
modifications can be made by changing one or both of the voltage or
the duration of the pacing impulse. For example, in certain
implementations, decreasing the pacing impulse energy of the
stimulation device may include reducing a pacing impulse voltage
setting while maintaining a pulse width setting. Alternatively,
decreasing the pacing impulse energy may instead include reducing
the pulse width setting while maintaining a constant pacing impulse
voltage. In still other implementations, reducing the pacing
impulse energy may include reducing both the voltage and pulse
width settings of the stimulation device simultaneously, in an
alternating fashion (e.g., reducing voltage for a first set of one
or more pacing impulses then reducing duration for a second set of
one or more pacing impulses), or in any other suitable
sequence.
[0153] Notably, in conventional approaches to capture threshold
testing, empirical/historical data collected from a wide range of
patients is often used to generate templates, determine ranges for
response characteristics, or otherwise determine capture type for a
given pacing impulse energy. Such approaches inherently rely on
some universal cutoff applicable to all patients. In contrast, the
approaches described herein rely on relative changes exhibited by a
specific patient in response to application of pacing impulses of
varying energies. As a result, the disclosed approach may be used
to identify the best possible pacing settings for a specific
patient, taking into account any abnormalities or idiosyncrasies of
the patient that may not be fully reflected in available empirical
data and that may cause the patient to deviate from any sort of
general standard.
[0154] The approaches to capture threshold testing and device
configuration described herein generally rely on the principle that
patients exhibit only a limited number of capture sequences as
pacing impulse energy is decreased. In other words, a patient will
generally exhibit a first capture type at relatively high pacing
impulse energy and will transition to one or more capture types
(including loss of capture) as pacing impulse energy is
decreased.
[0155] For patients with substantially intact conduction systems
(e.g., patients exhibiting narrow/normal QRS widths), such
transitions are summarized below in Tables 1a and 1b. For purposes
of Tables 1a and 1b, nonselective capture is indicated as "NS",
selective is indicated as "S", myocardium-only capture is indicated
as "M", and loss of capture is indicated as "LOC".
TABLE-US-00001 TABLE 1a Capture Type Transitions for Normal
Conduction (Single Transition Cases) Starting Capture Type After
Transition 1. NS LOC 2. S LOC 3. M LOC
TABLE-US-00002 TABLE 1b Capture Type Transitions for Normal
Conduction (Two-Transition Cases) Starting Capture Type After
1.sup.st Transition After 2.sup.nd Transition 1. NS M LOC 2. NS S
LOC
[0156] As illustrated in Table 1 a, the single transition cases
generally include transitioning from one capture type
(non-selective, selective, or myocardium-only) to a loss of
capture. In contrast, the two-transition cases are only applicable
for patients for which non-selective capture is possible, as each
of selective and myocardium-only capture necessarily transition to
loss of capture only as pacing impulse energy is decreased. As
indicated in Table 1 b, the transitions in such cases include
transitioning from non-selective capture to one of myocardium-only
or selective capture and then subsequently transitioning to loss of
capture.
[0157] Tables 2a-2c, below, provides a similar summary of possible
transitions for patients with conduction issues, such as branch
bundle block. In contrast to Tables 1a and 1b, Tables 2a-2c further
indicate whether non-selective and selective capture is with or
without correction ("w/corr." or "w/o corr.", respectively).
TABLE-US-00003 TABLE 2a Capture Type Transitions for BBB Patients
(Single Transition Cases) Starting Capture Type After Transition 1.
S (w/corr.) LOC 2. S (w/o corr.) LOC 3. NS (w/corr.) LOC 4. NS (w/o
corr.) LOC 5. M LOC
TABLE-US-00004 TABLE 2b Capture Type Transitions for BBB Patients
(Two-Transition Cases) Starting Capture After 1.sup.st After
2.sup.nd Type Transition Transition 1. S (w/corr.) S (w/o corr.)
LOC 2. NS (w/corr.) S (w/corr.) LOC 3. NS (w/corr.) NS (w/o corr.)
LOC 4. NS (w/corr.) S (w/o corr.) LOC 5. NS (w/corr.) M LOC 6. NS
(w/o corr.) S (w/o corr.) LOC 7. NS (w/o corr.) M LOC
TABLE-US-00005 TABLE 2c Capture Type Transitions for BBB Patients
(Three-Transition Cases) Starting After 1.sup.st After 2.sup.nd
After 3.sup.rd Capture Type Transition Transition Transition 1. NS
(w/corr.) S (w/corr.) S (w/o corr.) LOC 2. NS (w/corr.) NS (w/o
corr.) S (w/o corr.) LOC 3. NS (w/corr.) NS (w/o corr.) M LOC
[0158] Similar to Table 1a, the single transitions possible in
cases where patients have a conduction-related issue generally
include transitioning from one type of capture to a loss of
capture. As indicated in Tables 2a and 2b, additional cases in
which correction is lost arise in the context of patients with
conduction related issues. Notably, once correction is lost, it is
generally not regained as pacing impulse energy is further
decreased.
[0159] With the foregoing in mind, FIGS. 6 and 7 are flow charts
that illustrate methods that may be implemented together to
configure a stimulation device for purposes of providing HIS bundle
pacing. More specifically, FIG. 6 illustrates a first method 600 in
which pacing impulses are applied at different energies and
corresponding responses are measured and recorded. FIG. 7
illustrates a second method 700 in which the results, such as those
obtained from the method 600 of FIG. 6, are analyzed and classified
to determine pacing settings for the stimulation device.
[0160] Referring first to FIG. 6, the method 600 generally begins
with initializing the pacing impulse energy setting of the
stimulation device (operation 602). Although the initial pacing
impulse energy setting may vary, in at least certain
implementations of the present disclosure, the initial pacing
impulse energy setting is the maximum output energy of the
stimulation device. For purposes of the following example, pacing
impulse energy is controlled based on voltage alone (e.g., by
maintaining a constant pulse width) and the initial voltage is
assumed to be 7.5V; however, in other implementations and for
different devices, the initial pacing impulse energy setting value
may differ. In certain implementations, initializing the pacing
impulse energy setting of the stimulation device may also include
setting an operational mode of the stimulation device. Although
specific modes and settings for particular applications may vary,
in at least one example implementation, the stimulation device may
be set a DDD operational mode with a short A-H delay. In another
example implementation, the stimulation device may be set to a WI
mode with ventricular overdrive pacing (i.e., pacing of the
ventricle occurring at a higher than intrinsic rate).
[0161] At operation 604 a pacing impulse is applied to the HIS
bundle at the current pacing impulse energy setting and a
corresponding response is recorded (operation 606). As indicated in
FIG. 6, in at least certain implementations the response includes
each of a unipolar and bipolar response, which may be recorded and
analyzed as an electrogram (EGM) or similar response data
format.
[0162] Although the response in FIG. 6 includes both a unipolar and
bipolar EGM, in other implementations of the present disclosure,
the response data may instead include only one of a unipolar or
bipolar response. As discussed below in further detail, subsequent
analysis and classification of the response obtained in operation
604 may vary depending on whether bipolar, unipolar, or both
bipolar and unipolar data is available.
[0163] During recordation of the unipolar and bipolar responses,
the stimulation device may generally monitor for a response to the
applied pacing impulse (operation 608). In certain implementations,
detecting the response may include, among other things, detecting
the onset of the local myocardium activation resulting from
application of the pacing impulse. Such monitoring may continue
until either a response is detected, or a response timeout occurs
(operation 610).
[0164] When a response is detected, the measured response data is
stored, e.g., in memory of the stimulation device (operation 612).
If a minimum pacing impulse energy has not yet been reached
(operation 614), the pacing impulse energy of the stimulation
device is decreased (operation 616). For example and without
limitation, decreasing the pacing impulse energy may include one or
both of reducing the pacing impulse voltage (e.g., by 0.25V or some
other predetermined amount), changing the pacing impulse pulse
width, or a combination thereof. After decreasing the pacing
impulse energy, a subsequent pacing impulse is applied at the new
pacing impulse energy, and the foregoing process of detecting and
recording each of a unipolar and bipolar response are repeated. If,
on the other hand, a response is obtained for a minimum pacing
impulse energy (which may be a minimum pacing voltage, a minimum
pulse width, minimum combination of voltage and pulse width, or
minimum for any other parameter associated with pacing impulse
energy for purposes of the capture threshold test), the stimulation
device may proceed to analyzing the results of the test (operation
618).
[0165] As previously noted, a timeout may occur when monitoring a
response to the pacing impulse applied in operation 604. In other
words, a response to the applied pacing impulse may not be detected
within a predetermined period of time. If such a timeout occurs, a
backup impulse with higher pacing impulse energy may be applied to
ensure a heartbeat (operation 620) and the current pacing impulse
energy may be classified as resulting in loss of capture (operation
622). In certain implementations, the test may then be terminated,
and the stimulation device may proceed to analysis of the test
results (operation 618) as further reductions in the pacing impulse
energy would be unlikely to result in anything but loss of capture.
In other implementations, the test may be terminated in response to
detecting loss of capture for a predetermined number of pacing
impulse energy settings, e.g., loss of capture for two or more
consecutive pacing impulse energy settings.
[0166] Analysis of test results, such as those obtained via the
method 600 of FIG. 6, can be conducted in various ways; however,
FIG. 7 illustrates one example approach 700 to analyzing such
results to identify and implement patient-specific settings for a
stimulation device. In general, the method 700 is based on an
implementation in which the response data includes each of a
unipolar and a bipolar response and in which analysis of the
response data involves comparing each of the unipolar and bipolar
EGM response data for a current pacing impulse energy to those of a
next higher pacing impulse energy. If the device identifies a
change in one or both of the unipolar or bipolar responses between
the different pacing impulse energies, a capture type transition is
identified. After such analysis is conducted for each pacing
impulse energy, the system classifies each of the pacing impulse
energies as resulting in a particular capture type. As discussed
below in further detail, such classification may be based on the
number of transitions identified, the particular changes indicating
the occurrence of the transitions, an initial capture type, and the
like. The device may then configure its pacing settings based on
the classifications. For example, assuming that one or more pacing
impulse energies resulted in selective capture, the device may set
its pacing impulse energy to be the lowest energy for which
selective capture was achieved.
[0167] Referring now to FIG. 7, the method 700 generally assumes
that a collection of pacing response data is available for
analysis. As previously discussed in the context of FIG. 6, such
data may generally include a range of pacing impulse energies and,
for each pacing impulse energy, each of unipolar and bipolar EGM
response data. However, in other implementations, the response data
may include only one of unipolar or bipolar EGM response data. With
such response data available, the method 700 generally includes
initializing an index for purposes of traversing the data
(operation 702). Although other approaches may be implemented, in
the specific example of FIG. 7, the index is assumed to be
initialized to the second entry of the response data, which in
certain implementations may be, the entry corresponding to a pacing
impulse energy that is one step below the maximum energy (e.g., the
maximum voltage) of the device or a maximum impulse energy used
when collecting response data.
[0168] At operation 704, the unipolar and bipolar EGM data for the
current pacing energy is compared to that of the next highest
energy (e.g., by comparing the unipolar and bipolar EGM data for
the current index value to that of the previous index).
[0169] At operation 706, an analysis is conducted to determine
whether a change indicative of a transition is reflected by the two
sets of unipolar and bipolar EGM data. More specifically, one or
more characteristics of the unipolar response data and one or more
characteristics of the bipolar response data are compared between
the two sets to see if the different pacing impulse energies
elicited substantially different responses. In at least certain
implementations, the response characteristics may include the
activation time of the local ventricular myocardium in the
neighborhood of the HIS bundle and an estimate of the total
activation time of the ventricles. Various approaches may be used
to measure these characteristics from the collected response data.
For example and without limitation, the local activation time of
the ventricular myocardium may be measured from any of bipolar
stimulation-to-peak time (BSP), bipolar stimulation-to-onset, or
unipolar stimulation-to-onset. Similarly and without limitation,
total ventricular activation time may be estimated using unipolar
width (UW) or differentiated using unipolar maximum positive slope
(dv/dt). For purposes of the current example, however, BSP and UW
are used as the primary response characteristics for distinguishing
between capture types. Nevertheless, it should be appreciated that
other implementations of the present disclosure may rely on other
response characteristics for distinguishing between capture types,
including, but not limited to, any of the other response
characteristics noted above or otherwise discussed herein.
[0170] The threshold for determining whether a change has occurred
in the responses between successive pacing impulse energies may
vary between applications and may vary based on the specific
response characteristics being compared. The threshold for
determining a change may be relative (e.g., a percentage change) or
absolute between the responses. Also, depending on the
characteristics of interest, a change may be based on any of an
increase in the characteristic, a decrease in the characteristic,
or any other suitable change.
[0171] In at least one specific implementation, a change is
considered to have occurred if at least one response characteristic
of interest changes between pacing impulse energies by at least
about 10% (or an absolute equivalent for the response
characteristics of interest). So, for example, in the current
example in which BSP and UW are the characteristics of interest, a
change of at least about 10% between responses is considered to
indicate a change. During testing in conjunction with development
of the concepts herein, it was observed that as pacing impulse
energies change, BSP either increases or stays relatively constant
(e.g., does not change by more than about 10%) while UW may
increase, decrease, or stay constant. Accordingly, for the purposes
of the current example, a change in response characteristics is
considered to have occurred when BSP increases by at least about
10% between responses and/or if UW either increases or decreases by
at least about 10% between responses.
[0172] Referring back to FIG. 7, if a change is measured, a
transition is noted, and the observed change may be stored
(operation 708). For example, the stimulation device may generate a
flag, record, or similar indicator for purposes of noting that the
current pacing impulse energy resulted in a change in one or more
response characteristics. The stimulation device may also store
data or measurements describing the change in the response
characteristics. For example, the stimulation device may generate a
record that indicates that the current pacing impulse energy
resulted in a change and that includes related information such as
the characteristic that changed, the direction of the change (e.g.,
increase or decrease), the magnitude of the change (measured in
absolute or relative terms), or any other aspect of the change that
may be used in further characterizing the change.
[0173] The foregoing method may be repeated for each pacing impulse
energy for which a response was recorded. For example, in one
implementation, the stimulation device determines if the current
index is the maximum index (e.g., the index corresponding to the
lowest tests pacing impulse energy) (operation 710). If not, the
index is incremented (operation 712) and the process of comparing
the response for the pacing impulse energy associated with the
current index with the response of the next highest pacing impulse
energy and determining whether a change has occurred is
repeated.
[0174] If, on the other hand, the maximum index is reached, the
stimulation device determines the capture type for each pacing
impulse energy (operation 714). As previously discussed, capture
types for ranges of pacing impulse energies generally follow a
predetermined pattern. In other words, particular capture types
tend to transition along a limited number of known transition
sequences. As a result, by knowing the number of transitions that
occurred, the change in characteristics associated with the
transitions, and, in some cases, an initial capture type (e.g., a
capture type associated with a relatively high pacing impulse
voltage), capture types may be readily assigned to pacing impulse
energies.
[0175] The following tables provide different transition paths and
the various indications by which they may be identified when UW and
BSP are the response characteristics of interest. Tables 3a and 3b
provide transitions and indications for patients with substantially
normal conduction and for which correction is not required. Tables
4a-4c provide transitions and indications for patients with
conduction issues, such as branch bundle block. In each of the
tables, the capture types include selective capture (S),
non-selective capture (NS), myocardium-only capture (M), and loss
of capture (LOC). For each of selective and non-selective capture,
Tables 4a-4c further indicate whether the given capture type
includes correction ("w/corr.") or lacks correction ("w/o corr.").
As previously noted, the current example generally relies on
bipolar stim-to-peak time (BSP) and unipolar width (UW) as the
primary characteristics for identifying transitions. Accordingly,
for each of BSP and UW, each transition listed in the tables
further includes whether the transition is indicated by each of BSP
and UW increasing (+), decreasing (-), or remaining unchanged (=).
As previously discussed, an increase or a decrease may, in certain
implementations, correspond to a change of at least about 10% in a
response characteristic; however, the specific threshold used in
identifying a change may vary between applications and patients. In
general, it should be understood that for purposes of the present
disclosure a characteristic being "unchanged" generally means that
any changes to the characteristic fall below the threshold for
indicating a change. For example, if a 10% threshold is
implemented, any change less than 10% would be considered
"unchanged".
TABLE-US-00006 TABLE 3a Transition Indications for Normal
Conduction (Single Transition Cases) Transition Indication 1. NS
.fwdarw. LOC BSP + UW- 2. S .fwdarw. LOC BSP + UW= 3. M .fwdarw.
LOC BSP + UW-
TABLE-US-00007 TABLE 3b Transition Indications for Normal
Conduction (Two-Transition Cases) Transition 1.sup.st 2.sup.nd
Progression Indication Indication 1. NS .fwdarw. M .fwdarw. LOC BSP
= UW+ BSP + UW- 2. NS .fwdarw. S .fwdarw. LOC BSP + UW- BSP +
UW=
TABLE-US-00008 TABLE 4a Transition Indications for BBB Patients
(Single Transition Cases) Transition Indication 1. S (w/corr.)
.fwdarw. LOC BSP + UW+ 2. S (w/o corr.) .fwdarw. LOC BSP + UW= 3.
NS (w/corr.) .fwdarw. LOC BSP + UW+ 4. NS (w/o corr.) .fwdarw. LOC
BSP + UW- 5. M .fwdarw. LOC BSP + UW-
TABLE-US-00009 TABLE 4b Transition Indications for BBB Patients
(Two-Transition Cases) 1.sup.st 2.sup.nd Transition Progression
Indication Indication 1. S (w/corr.) .fwdarw. S (w/o corr.)
.fwdarw. LOC BSP = UW+ BSP + UW= 2. NS (w/corr.) .fwdarw. S
(w/corr.) .fwdarw. LOC BSP + UW- BSP + UW+ 3. NS (w/corr.) .fwdarw.
NS (w/o corr.) .fwdarw. LOC BSP = UW+ BSP + UW- 4. NS (w/corr.)
.fwdarw. S (w/o corr.) .fwdarw. LOC BSP + UW+ BSP + UW= 5. NS
(w/corr.) .fwdarw. M .fwdarw. LOC BSP = UW+ BSP + UW- 6. NS (w/o
corr.) .fwdarw. S (w/o corr.) .fwdarw. LOC BSP + UW- BSP + UW= 7.
NS (w/o corr.) .fwdarw. M .fwdarw. LOC BSP = UW+ BSP + UW-
TABLE-US-00010 TABLE 4c Transition Indications for BBB Patients
(Three-Transition Cases) 1.sup.st 2.sup.nd 3.sup.rd Transition
Progression Indication Indication Indication 1. NS (w/corr.)
.fwdarw. S (w/corr.) .fwdarw. S (w/o corr.) .fwdarw. LOC BSP + UW-
BSP + UW+ BSP + UW= 2. NS (w/corr.) .fwdarw. NS (w/o corr.)
.fwdarw. S (w/o corr.) .fwdarw. LOC BSP = UW+ BSP + UW- BSP + UW=
3. NS (w/corr.) .fwdarw. NS (w/o corr.) .fwdarw. M .fwdarw. LOC BSP
= UW+ BSP = UW+ BSP + UW-
[0176] Referring to Tables 3a-4c, the process of determining
capture types for each pacing impulse voltage (operation 714) may
be conducted by first determining the type of patient conduction
(e.g., normal or BBB) and determining which table is applicable
based on the number of transitions observed during analysis of the
response data. For example, if a patient has substantially normal
conduction and two transitions were identified during analysis of
the response data, the transition and indication information for
Table 3b would apply. As another example, if three transitions were
identified in a patient known to have BBB, the information in Table
4c would apply.
[0177] The specific characteristics of the identified transitions
would then be analyzed to determine which transition sequence is
applicable. For example, referring to Table 3b, if the transition
resulted in an increase in each of BSP and UW, then the transition
sequence is most likely NS S LOC. Accordingly, all pacing impulse
energies above the pacing impulse energy identified as the first
transition would be classified as resulting in non-selective
capture, all pacing impulse energies from the first transition
pacing impulse energy to the second pacing impulse energy would be
classified as resulting in selective capture, and all remaining
pacing impulse energies would be classified as resulting in loss of
capture.
[0178] In certain cases, such as the foregoing example, only one
transition needs to be analyzed in order to determine the capture
types for each pacing impulse energy. However, in other scenarios,
analysis of multiple transitions may be required to determine the
applicable transition sequence. For example, each of the NS
(w/corr.) S (w/corr.) LOC sequence and the NS (w/o corr.) S (w/o
corr.) LOC sequence included in Table 4b share a common indication
for their first transition (namely, an increase in BSP and a
decrease in UW), but differ in the indication for their second
transition (namely, an increase in both BSP and UW for the former
and an increase in BSP only for the latter). Accordingly, analysis
of multiple transitions may be required to determine the applicable
transition sequence.
[0179] Certain transition sequences may share all indications and,
as a result, may be indistinguishable from each on the basis of the
identified transitions alone. In such cases, additional information
regarding the patient may be required to determine the applicable
transition sequence. For example, in at least one implementation,
the capture type corresponding to the maximum pacing impulse energy
(or other high pacing impulse energy) may first be identified using
any suitable technique. This initial capture type may then be used
to identify the correct transition sequence.
[0180] In one alternative implementation, the initial capture type
may be determined automatically by the stimulation device by
conducting a test in which the response elicited by applying the
maximum pacing impulse energy (or other high pacing impulse energy)
is analyzed in detail, such as by measuring certain characteristics
or comparing the response to one or more stored templates to
determine its corresponding capture type. Based on this initial
capture type, the stimulation device may then be able to
distinguish between transition sequences having otherwise similar
indications.
[0181] In still other instances, neither the transition sequence
nor the initial capture type may distinguish between transition
sequences. For example, as indicated in Table 4b, the transition
sequences NS (w/corr.).fwdarw.NS (w/o corr.).fwdarw.LOC and NS
(w/corr.).fwdarw.M.fwdarw.LOC have the same transition indicators
and the same initial capture type. In certain implementations, such
a result may be addressed by classifying pacing impulse energies
between the first and second transitions as resulting in an
indeterminate capture type.
[0182] Following classification of the pacing impulse energies, the
stimulation device identifies a preferred pacing impulse energy
setting and sets its pacing settings accordingly (operation 716).
Selection of a pacing impulse energy setting may include
identifying the lowest pacing impulse energy resulting in the
"best" available capture type. In patients with intact conduction
systems, the stimulation device may identify the lowers pacing
impulse energy for which selective or non-selective capture was
achieved and program the stimulation device's pacing settings
accordingly. In patients with branch bundle block or similar
conduction issues, corrective results are generally preferred over
non-corrective results. Therefore, the stimulation device may
identify the lowest pacing energy that leads to capture (either
selective or non-selective) and correction and program the
stimulation device's pacing settings accordingly.
[0183] In certain implementations, a margin of safety may be
applied to the selected pacing impulse energy. To do so, the pacing
impulse energy setting of the stimulation device may be set higher
(e.g., 10-20% higher) than the optimal pacing impulse energy
identified based on the response data (e.g., by increasing the
voltage and/or the pulse width over that corresponding to the
selected pacing impulse energy). In certain implementations, such a
margin of safety may be applied when a beat-by-beat capture
management mode of the stimulation device is subsequently activated
in which pacing is applied and monitored continuously. In general,
however, the foregoing approach results in the identification and
implementation of pacing settings for optimal heart function for
the specific patient while improving overall life and functionality
of the stimulation device and its battery by avoiding unnecessary
overstimulation.
[0184] The foregoing capture threshold test can be run manually
in-clinic or periodically out-of-clinic. In certain
implementations, the response data and/or any particular response
characteristics for each capture type obtained during the capture
threshold test may be stored as one or more patient-specific
templates. Such templates may then be used when the stimulation
device actively provides beat-by-beat pacing and capture
management. In one specific implementation, during beat-by-beat
pacing and capture management, the stimulation device collects
response data (e.g., EGM response data) following application of
pacing impulses and analyzes the collected response data.
[0185] In one implementation, the stimulation device analyzes the
response data collected during beat-by-beat pacing by comparing the
collected response data to data collected during the capture
threshold test. For example, as noted above, as part of the capture
threshold test, the stimulation device may determine and store
values or ranges of values of response characteristics that
indicate particular capture types. The stimulation device may then
compare the response data collected during beat-by-beat pacing to
the values identified during the capture threshold test to classify
the pacing response, to determine when HIS bundle capture has been
lost (e.g., when myocardium only capture has occurred), and/or when
there has been a loss of capture. To the extent a loss of HIS
bundle capture or total loss of capture occurs, the stimulation
device may take appropriate recovery actions. Such recovery actions
may include, without limitation, increasing the pacing impulse
energy to regain capture or delivering one or more back-up pacing
impulses.
[0186] In one specific example, following initial calibration of a
stimulation device, the stimulation device may continuously or
periodically measure unipolar and/or bipolar responses resulting
from applied pacing impulses. The stimulation device may further
determine the resulting capture type for each pacing impulse. If
the stimulation device identifies a change in capture type (e.g.,
from selective or non-selective capture to myocardium only capture
of loss of capture), the stimulation device may execute the capture
threshold test describe above to identify new pacing impulse energy
settings to regain capture. The stimulation device may also be
configured to execute the capture threshold test in response to
identifying a loss of capture (or predetermined number of loss of
capture events).
[0187] The example method discussed above generally relies on the
use of both unipolar and bipolar EGM characteristics to identify
transitions between capture types. More specifically and as
illustrated in Tables 3a-4c, the foregoing example relies on
changes in unipolar width (UW) and bipolar stim-to-peak time (BSP)
to detect changes in capture type. However, as previously
discussed, other characteristics may be used to detect changes in
capture type.
[0188] In certain implementations, capture threshold tests
according to the present disclosure may instead rely on
characteristics of a unipolar response (e.g., a unipolar EGM) only
instead of on a combination of a unipolar and bipolar response. For
example and without limitation, instead of BSP and UW, the method
may instead be based on unipolar stim-to-onset time (USO) and
unipolar width (UW). Similar to Tables 3a-4c, tables 5a-6c list the
indications for each transition for a method using USO and UPS
TABLE-US-00011 TABLE 5a Transition Indications for Normal
Conduction (Single Transition Cases) Transition Indication 1. NS
.fwdarw. LOC USO + UW- 2. S .fwdarw. LOC USO + UW= 3. M .fwdarw.
LOC USO + UW-
TABLE-US-00012 TABLE 5b Transition Indications for Normal
Conduction (Two-Transition Cases) Transition 1.sup.st 2.sup.nd
Progression Indication Indication 1. NS .fwdarw. M .fwdarw. LOC USO
= UW+ USO + UW- 2. NS .fwdarw. S .fwdarw. LOC USO + UW- USO +
UW=
TABLE-US-00013 TABLE 6a Transition Indications for BBB Patients
(Single Transition Cases) Transition Indication 1. S (w/corr.)
.fwdarw. LOC USO + UW+ 2. S (w/o corr.) .fwdarw. LOC USO + UW= 3.
NS (w/corr.) .fwdarw. LOC USO + UW+ 4. NS (w/o corr.) .fwdarw. LOC
USO + UW- 5. M .fwdarw. LOC USO + UW-
TABLE-US-00014 TABLE 6b Transition Indications for BBB Patients
(Two-Transition Cases) 1.sup.st 2.sup.nd Transition Progression
Indication Indication 1. S (w/corr.) .fwdarw. S (w/o corr.)
.fwdarw. LOC USO = UW+ USO + UW= 2. NS (w/corr.) .fwdarw. S
(w/corr.) .fwdarw. LOC USO + UW- USO + UW+ 3. NS (w/corr.) .fwdarw.
NS (w/o corr.) .fwdarw. LOC USO = UW+ USO + UW- 4. NS (w/corr.)
.fwdarw. S (w/o corr.) .fwdarw. LOC USO + UW+ USO + UW= 5. NS
(w/corr.) .fwdarw. M .fwdarw. LOC USO = UW+ USO + UW- 6. NS (w/o
corr.) .fwdarw. S (w/o corr.) .fwdarw. LOC USO + UW- USO + UW= 7.
NS (w/o corr.) .fwdarw. M .fwdarw. LOC USO = UW+ USO + UW-
TABLE-US-00015 TABLE 6c Transition Indications for BBB Patients
(Three-Transition Cases) 1.sup.st 2.sup.nd 3.sup.rd Transition
Progression Indication Indication Indication 1. NS (w/corr.)
.fwdarw. S (w/corr.) .fwdarw. S (w/o corr.) .fwdarw. LOC USO + UW-
USO + UW+ USO + UW= 2. NS (w/corr.) .fwdarw. NS (w/o corr.)
.fwdarw. S (w/o corr.) .fwdarw. LOC USO = UW+ USO + UW- USO + UW=
3. NS (w/corr.) .fwdarw. NS (w/o corr.) .fwdarw. M .fwdarw. LOC USO
= UW+ USO = UW USO + UW-
[0189] The methods 600 of FIGS. 6 and 700 of FIG. 7 provide a
relatively complete analysis of pacing impulse energy settings and
their respective responses. More specifically, the methods 600 and
700 identify the capture type for each pacing impulse energy
setting and all transitions between capture types. Nevertheless, it
should be appreciated that in certain instances, it may only be
necessary to identify a particular transition and to configure the
pacing impulse energy settings of the pacing device based on the
particular threshold.
[0190] In applications for patients with narrow QRS, for example,
the systems and methods disclosed herein may be modified to
identify the minimum pacing impulse energy below which capture of
the HIS bundle has been lost and to configure the pacing device to
deliver pacing impulses at that minimum pacing impulse energy. In
other words, the systems and methods may identify the threshold at
which the capture type transitions from either of selective or
non-selective capture to either of myocardium-only capture or loss
of capture and then set the pacing impulse energy of the
stimulation device above the energy at which capture of the HIS
bundle is lost. In applications for patients with wide QRS, the
systems and methods disclosed herein may be modified to identify
the minimum pacing impulse energy below which BBB correction is
lost and to configure the pacing device to deliver pacing impulses
at that minimum pacing impulse energy. In other words, the systems
and methods may identify the threshold at which the capture type
transitions from either selective or non-selective capture with
correction to a capture type without correction (including any of
selective or non-selective capture without correction, myocardium
only capture, or loss of capture) and then set the pacing impulse
energy of the stimulation device above the energy at which
correction is lost.
[0191] It should also be understood that while the method 700 is
generally described as occurring after the method 600, in certain
applications, the two methods may be combined. More specifically,
in the foregoing example, the unipolar and/or bipolar response data
for multiple pacing impulse energies are first collected using the
method 600 of FIG. 6. That response data is then processed to
identify transitions using the method 700 of FIG. 7. In other
implementations, certain operations of the method 700 of FIG. 7 may
be performed as pacing impulse response data is collected such that
the process of collecting, analyzing, and classifying the response
data may be combined.
[0192] FIG. 8, for example, is a flow chart illustrating a method
800 that combines collection and analysis of response data to
configure pacing settings of a stimulation device. Similar to the
method 600 of FIG. 6, the method 800 of FIG. 8 begins by
initializing the pacing energy setting (operation 802), applying a
pacing impulse to the HIS bundle (operation 804), and recording
corresponding response data (operation 806), the response data
including one or both of unipolar and bipolar responses to the
pacing impulse. The method 800 also similarly includes monitoring
for a response to the applied pacing impulse (operation 808) and
determining whether a timeout has occurred (operation 810). In the
event of a timeout (e.g., a timeout caused by a loss of capture),
the method includes applying a backup impulse (operation 822)
before terminating the test process (operation 824). Termination of
the test process is discussed below in further detail.
[0193] Assuming loss of capture has not occurred and if the pacing
impulse applied at operation 804 is the first pacing impulse of the
test (operation 818), the pacing impulse energy is decreased
(operation 814, e.g., by decreasing the duration and/or amplitude
of the impulse as previously discussed in the context of operation
616). A subsequent pacing impulse is then delivered and the process
of recording and identifying a response or identifying loss of
capture is repeated such that two sets of response data are
available, each corresponding to a respective pacing impulse
energy.
[0194] If response data is available for two consecutive pacing
impulse energies, the response data for the pacing impulses is
compared (operation 818) to determine whether a capture threshold
has been identified (operation 820). The process of comparing
consecutive sets of response data generally includes comparing the
response data to identify changes indicative of a change in capture
type and, more specifically, whether a change in one or more
response characteristics between the two response data sets is
indicative of a transition between capture types. As discussed in
the context of operation 704 of FIG. 7, in certain implementations,
the response data for each pacing impulse energy may include both
unipolar and bipolar response data. In such implementations, the
response characteristics may include, for example and without
limitation, each of bipolar stim-to-peak time and unipolar width.
In implementations in which only unipolar response data is
collected, the response characteristics may include, for example
and without limitation, unipolar stim-to-onset time, and unipolar
width.
[0195] The process of comparing the sets of response data in
operation 816 aims to determine whether a capture threshold has
been crossed between the two different pacing impulse energies
corresponding to the sets of response data. In applications for
patients with narrow QRS, for example, the comparison of operation
816 may determine whether a loss of HIS bundle capture occurred
between the pacing impulses. To do so, the comparison may include
determining whether the response characteristics indicate a
transition from either of selective or non-selective capture to
myocardium-only or loss of capture occurred in response to reducing
the pacing impulse energy (as listed, e.g., in Tables 3a-b for
applications including unipolar and bipolar response data or Tables
5a-b for application including unipolar response data only). In
applications for patients with BBB, the comparison of operation 816
may determine whether a loss of BBB correction has occurred. For
example, the comparison may include determining whether the
response characteristics indicate a transition from a corrective
response to a non-corrective response in response to reducing the
pacing impulse energy (as listed, e.g., in Tables 4a-c
(unipolar/bipolar case) and 6a-c (unipolar only case)).
[0196] If a threshold is not identified, a check is performed to
determine if the lowest pacing impulse energy has been reached
(operation 820). If not, the pacing impulse energy is decreased and
the process of applying a pacing impulse, measuring the
corresponding response, and comparing the response to the
previously collected response for purposes of identifying a
threshold is repeated.
[0197] If, on the other hand, a threshold is identified, minimum
pacing impulse energy is reached, or (as noted above) loss of
capture occurs, the test process is ended (operation 824). When
loss of capture or reaching a minimum pacing impulse energy results
in termination of the pacing test, various remedial steps may be
initiated including, among other things, generating and
transmission of alerts or alarms, restarting of the pacing test,
initiation of a backup pacing routine, and the like.
[0198] In cases where the test process is terminated in response to
identifying a threshold (e.g., a HIS bundle capture threshold or
correction threshold), completing the test process at operation 824
includes configuring the pacing settings of the stimulation device
based on the threshold. In particular, the pacing settings of the
stimulation device are configured such that the pacing impulse
energy of the stimulation device is the lowest at which the
threshold is not crossed. In applications in which the threshold is
for HIS bundle capture or BBB correction, for example, the pacing
settings of the stimulation device would be modified to have the
lowest pacing energy at which HIS bundle capture or BBB correction
are achieved. As a result, the stimulation device is automatically
configured to achieve HIS bundle capture or correction efficiently
by using the minimum pacing impulse energy possible.
[0199] In certain applications of the present disclosure, accuracy
of the capture threshold test may be improved by capturing multiple
sets of response data for each pacing impulse energy and relying on
a statistical combination of such responses in identifying
thresholds and capture types. For example, FIG. 9 is a flow chart
illustrating a method 9000 for collecting multiple sets of response
data for each of a range of pacing impulse voltages and FIG. 10 is
a flow chart illustrating a method 1000 in which the results
obtained from the method 900 of FIG. 9, are analyzed and classified
to determine pacing settings for the stimulation device.
[0200] Referring first to FIG. 9, the method 9 generally begins
with initializing the pacing impulse energy setting of the
stimulation device (operation 902). Although the initial pacing
impulse energy settings may vary, in at least certain
implementations of the present disclosure, the initial pacing
impulse energy is the maximum output energy of the stimulation
device or a similar upper bound value.
[0201] At operation 904 a first pacing impulse at the current
pacing impulse energy setting is applied to the HIS bundle and a
first corresponding response is recorded (operation 906). In at
least certain implementations the first response includes one or
both of a unipolar response and a bipolar, which may be recorded as
an EGM or similar data. During recordation of the response, the
stimulation device may generally monitor for a response to the
applied pacing impulse (operation 908) and, if no such response is
detected prior to a timeout (operation 910), a backup impulse may
be applied (operation 920) and the current pacing impulse energy
setting may be classified as resulting in loss of capture
(operation 922). In certain implementations, the test may then be
terminated (with each subsequent pacing impulse energy similarly
being designated as resulting in loss of capture) and the
stimulation device may proceed to analyzing of the test results
(operation 918).
[0202] When a response is detected, on the other hand, the recorded
responses are stored in memory of the stimulation device (operation
912). The stimulation device then determines whether a required
quantity of responses (e.g., three) for the current pacing impulse
energy have been collected (operation 913). If not, another pacing
impulse is applied at the current energy and another response is
recorded and stored. If, on the other hand, the quantity of
recorded responses for the current pacing impulse energy is met,
another check is conducted to see if the current pacing impulse
energy is a minimum pacing impulse energy (operation 914). If so,
then response collection is complete, and analysis begins
(operation 918). If not, the pacing impulse energy is decreased
(operation 916) and response data is collected for the reduced
energy.
[0203] The method 900 results in the collection of multiple sets of
response data for each of a range of pacing impulse energies.
Following such collection, the collected response data may
subsequently be analyzed to identify capture thresholds, to
identify preferred pacing impulse energy settings for the
stimulation device, or perform similar operations.
[0204] In one example implementation, analysis of the multiple sets
of response data may include averaging or otherwise mathematically
combining the response data for each pacing impulse energy. For
example, the response data for each pacing impulse energy may be
averaged to generate a mean response for each pacing impulse
energy. The combined responses may then be analyzed (such as by
using the method 700 of FIG. 7) to identify capture thresholds,
capture type transitions, and the like for purposes of determining
optimal pacing impulse settings.
[0205] In other implementations, analyzing the multiple sets of
response data may include identifying pacing impulse energies that
resulted in highly variable or otherwise inconsistent responses. To
the extent such pacing impulse energies are identified, they may be
rejected as potential settings for the pacing impulse energy. In
certain implementations, additional analysis may also be conducted
to determine whether the inconsistency of the response data for a
given pacing impulse energy is a result of poor detection or a
result of the pacing impulse energy being at or near a transition
energy between two capture types. In the former case, the pacing
impulse energy may still be considered a candidate for the optimal
pacing impulse energy setting. In the latter case, however, the
pacing impulse energy would result in inconsistent and
unpredictable capture and would therefore remain rejected as a
potential candidate for the optimal pacing impulse energy setting.
By way of this process, potentially problematic pacing impulse
energy settings (e.g., those that may result in multiple capture
types) are avoided and the likelihood that the ultimately selected
pacing impulse energy setting will consistently result in the best
available capture scenario is increased.
[0206] FIGS. 9 and 10 are flow charts of example methods 900, 1000
for collecting and analyzing response data and identifying an
optimal pacing impulse setting for a given patient based on the
response data. More specifically, the method 900 illustrates a
method for collecting response data for a patient that includes
multiple response data samples for a range of pacing impulse
energies. The method 1000, in contrast, illustrates analysis of
such response data for purposes of identifying an optimal pacing
impulse energy setting for the patient. The methods 900 and 1000
may be executed by an implanted stimulation device or a programming
unit in communication with such an implanted stimulation
device.
[0207] The method 1000 generally assumes that patient response data
is available for analysis. The patient response data generally
includes a range of pacing impulse energies and, for each pacing
impulse energy, measured responses/samples for each of multiple
pacing impulses delivered to the patient at the pacing impulse
energy. In certain implementations, each measured response may be
stored as one or both of a unipolar or bipolar EGM or as values
corresponding to one or both of a unipolar or bipolar EGM.
[0208] The method 1000 begins by obtaining response data (operation
1002), such as by executing the response collection method 900 of
FIG. 9. Next, any pacing impulse energies resulting in inconsistent
responses are excluded (operation 1004). Although the approach to
identifying inconsistent responses may vary, in at least one
example implementation, a variance metric is calculated for each
pacing impulse energy that indicates the variance between the
measured responses for the particular pacing impulse energy. If the
variance metric exceeds a threshold (or similar value), the pacing
impulse energy is excluded from further consideration as a
potential pacing impulse energy setting.
[0209] The variance metric may be any suitable measure of
variability. However, in certain implementations, the variance
metric may correspond to the variance for one or more response
characteristics and, in particular, response characteristics that
may later be used to identify transitions between capture types.
For example, as previously discussed, in certain implementations of
the present disclosure, transitions between capture types may be
identified based on unipolar width and bipolar stim-to-peak. In
such implementations, when evaluating a given pacing impulse
energy, the variance metric used to determine whether to exclude
the pacing impulse energy, may be based on the variance in unipolar
width and/or bipolar stim-to-peak time for the pacing impulse
energy. For example, if unipolar width and/or bipolar stim-to-peak
time vary by 10% or more for the pacing impulse energy, the pacing
impulse energy may be excluded.
[0210] In certain implementations, the process of excluding
inconsistent pacing impulse energies may include generating updated
patient response data that omits the pacing impulse energies having
inconsistent responses. In other implementations, each of the
inconsistent pacing impulse energies may be marked, flagged, or
otherwise noted for exclusion from further consideration and
analysis.
[0211] After identifying and excluding pacing impulse energies
exhibiting high variance, a subsequent analysis of the remaining
pacing impulse energy candidates may be conducted to determine an
optimal pacing impulse energy setting. Such analysis may vary in
implementations of the present disclosure; however, the process of
analyzing the updated patient response data generally includes
comparing characteristics of the response data for consecutive
pacing impulse energies to identify transitions between capture
types.
[0212] In the specific example of the method 1000, analysis begins
by initializing an index for purposes of traversing the updated
patient response data (operation 1006). The index of the example
method 1000 is assumed to be initialized to the second pacing
impulse energy of the updated patient response data, i.e., to the
pacing impulse energy that is one step below the maximum pacing
impulse energy included in the updated patient response data.
[0213] The index of the method 1000 is just one approach to
traversing the updated patient response data. More generally, any
suitable method for comparing responses for consecutive pacing
impulse energies of the updated patient response data may be used
in implementations of the present disclosure.
[0214] At operation 1008, the response data for the current pacing
impulse energy is compared to that of the next highest pacing
impulse energy to determine whether a capture type transition has
occurred. As previously noted, each pacing impulse energy includes
a set of measured responses. Accordingly, comparing the responses
of any two pacing impulse energies may first include averaging or
otherwise combining the set of measured responses for each of the
two pacing impulses. Combining a set of measured responses may
include generating an average response from which one or more
response characteristics may be determined. So, for example, in
implementations in which multiple responses are obtained for each
pacing impulse energy and each response includes a bipolar and
unipolar EGM, combining the set of measured responses may include
generating each of an average bipolar EGM and an average unipolar
EGM representative of the set. In other implementations, combining
a set of measured responses for a particular pacing impulse energy
may include calculating average values for one or more response
characteristics for each response in the set and, in particular,
for response characteristics that may be used subsequently to
identify transitions between capture types. For example, in
implementations in which transitions are identified using bipolar
stim-to-peak and unipolar width, combining a set of measured
responses for a particular pacing impulse energy may include
calculating each of an average bipolar stim-to-peak value and an
average unipolar width representative of the set.
[0215] Regardless of how response data for each pacing impulse
energy is combined, operation 1008 generally includes comparing the
combined response data for the current pacing impulse energy to
that of the next highest pacing impulse energy to determine whether
a change in response occurred between the two pacing impulse
energies (operation 1010). As previously discussed in the context
of FIG. 7, the threshold for determining whether a change in
response has occurred may vary between applications and particular
patients; however, in at least one implementation, a change may be
considered to have occurred if a given response characteristics
varies between the combined response data of the current pacing
impulse energy and the combined response data of the next highest
pacing impulse energy by at least about 10%. If a change is
identified in operation 1010, the current pacing impulse energy may
be marked, flagged, or otherwise noted as corresponding to a
transition (operation 1012).
[0216] The foregoing operations may be repeated for each pacing
impulse energy included in the updated patient response data. For
example, in one implementation, if the current index is not the
maximum index (i.e., the index corresponding to the last available
voltage) (operation 1014), the index is incremented (operation
1016) and the process of comparing response data to identify a
change/transition is repeated for the next consecutive pair of
pacing impulse energies included in the updated patient response
data.
[0217] If, on the other hand, the maximum index is reached, the
stimulation device determines the capture type for each pacing
impulse voltage (operation 1018) and the stimulation device sets
its pacing settings based on the available capture types (operation
1020) using processes substantially similar to those discussed
above in the context of FIG. 7. As discussed in the context of FIG.
7, such a process may generally include identifying capture types
based on the number of observed transitions, the nature of the
changes observed between transitions, and/or an initial capture
type for the patient. Based on the identified capture types, the
stimulation device may then identify the lowest pacing impulse
energy that results in the best available capture type for the
particular patient (e.g., the lowest pacing impulse energy that
maintains capture of the HIS bundle or that corrects a branch
bundle block). In contrast to the method of FIG. 7, however, such
analysis in the context of the method 1000 excludes from
consideration any pacing impulse energies identified as potentially
resulting in inconsistent pacing responses. By doing so, the
stimulation device improves the likelihood that the selected pacing
impulse energy setting will result in consistent pacing and
capture/correction.
[0218] Certain implementations of the current disclosure may also
include additional analysis of pacing impulse energies excluded in
operation 1004 to determine whether the inconsistent response data
for the excluded pacing impulse energy was a result of poor
detection during collection of the response data or a result of the
pacing impulse energy corresponding to a transition between capture
types. In the former case, the pacing impulse energy may be
reconsidered as a potential pacing impulse setting while in the
latter case, the pacing impulse energy would remain excluded.
[0219] One example approach to the foregoing analysis for a pacing
impulse energy may include examining the response data and/or
capture type for each of the next highest and next lowest pacing
impulse energies. If the next highest and next lowest pacing
impulse energies resulted in substantially similar response
characteristics or otherwise resulted in the same capture type, the
inconsistent response data for the pacing impulse energy in
question is likely the result of poor detection. In such cases, the
pacing impulse energy may be assigned the same capture type as the
neighboring pacing impulse energies and may be reconsidered as a
candidate for the pacing impulse energy setting of the stimulation
device. Alternatively, new response data for the pacing impulse
energy may be collected with the goal of obtaining consistent
response data. Such new response data may be subsequently analyzed
as discussed above. Conversely, if the next highest and next lowest
pacing impulse resulted in substantially different response
characteristics or otherwise resulted in different capture types,
then the inconsistent response data for the pacing impulse energy
in question is likely the result of the pacing impulse energy being
at or near a transition energy between capture types. Accordingly,
to avoid unpredictable pacing results, the pacing impulse energy in
question would remain excluded from consideration as a pacing
impulse energy setting.
[0220] As discussed above, the method 900 of FIG. 9 and the method
1000 of FIG. 10 provide methods for collecting and then analyzing
response data, respectively. According to the methods, a full set
of response data is collected and then subsequently analyzed. In
other implementations, aspects, and operations of the method 900 of
FIG. 9 and the method 1000 of FIG. 10 may be combined such that the
process of collecting and analyzing the response data is combined.
For example and similar to the method 800 of FIG. 8, the response
data for each pacing impulse energy may be analyzed as it is
collected. Such analysis may include, among other things,
determining whether the samples of response data for the pacing
impulse energy are consistent and whether the response data
indicates a transition from a previously applied pacing impulse
energy, each of which are discussed above.
Non-Sequential Capture Threshold Testing
[0221] The HIS capture threshold test is generally performed while
the IMD is operating in a DDD mode, utilizing a short AV delay, or
the IMD is operating in a WI mode, while utilizing overdrive
pacing, both of which introduce added pacing beyond what a patient
may normally experience, thereby introducing patient discomfort.
Embodiments herein seek to minimize the HIS capture threshold test
duration to reduce any patient discomfort. In addition, during HIS
capture threshold testing, embodiments herein seek to avoid or
limit the Wedensky effect, in which capture thresholds measured, in
response to successive HBP at decrementing amplitudes, are usually
slightly lower as compared to capture thresholds that are measured,
in response to successive HBP at incrementing amplitudes.
[0222] As previously noted, threshold searching refers to the
process of identifying particular impulse characteristics at which
different types of capture occur. In general, such processes
include applying a pacing impulse at a starting voltage, measuring
the corresponding response (e.g., by IEGM), determining what type
of capture (if any) has occurred, and based on the type of capture,
modifying the voltage. The process of applying an impulse,
measuring, and classifying the response, and adjusting the voltage
for a subsequent impulse is repeated to eventually converge on an
optimal voltage setting. As described below and in the applications
and patents referenced and incorporated herein, approaches to
setting the starting voltage, modifying the voltage, and conducting
other aspects of the threshold test may be varied.
[0223] FIG. 11 illustrates a process for implementing a
nonsequential capture threshold test in accordance with embodiments
herein. As explained herein, the non-sequential threshold search
first performs "rough" decremental HB pacing followed by processing
of the evoked response to identify candidate NS, S, and/or Myo
capture thresholds. Afterward, the nonsequential threshold search
performs "fine" incremental HB pacing starting from below the
identified candidate NS, S and/or Myo thresholds to determine the
NS, S and/or Myo thresholds more precisely. The capture threshold
test is considered a "nonsequential, in that one or both of i)
steps between successive HBP pacing pulses are decremented over a
portion of the test and then incremented over a portion of the
test, and/or ii) steps between a first subset of the HBP pacing
pulses have one amplitude, while steps between a second subset of
the HBP pacing pulses have a second different amplitude.
[0224] Further, the nonsequential capture threshold test manages
the upper and lower limits and range for the second subset of HBP
pacing pulses based on one or more transitions identified from the
first subset of HBP pacing pulses.
[0225] For example, the fine incremental HB pacing may terminate at
0.25V above the candidate capture thresholds identified from the
rough decremental HB pacing to account for the Wedensky effect.
Depending on the underlying capture type, the non-sequential
threshold search may be 40% to 50% shorter in duration than a
sequential threshold search while achieving the same or better
precision.
[0226] In general, the method illustrated in FIG. 11 may be viewed
as a "rough step down/fine step up" approach to threshold
searching. In particular, the method applies a first impulse that
achieves non-selective capture and reduces the voltage until
capture of the HIS bundle is lost. The step size is decreased, and
the step is inverted such that the voltage is increased until
capture is regained. This process repeats with progressively
smaller step sizes until a final impulse voltage is reached.
[0227] At 1102, the one or more processors initialize the HB pacing
for a rough capture test.
[0228] At 1104, the one or more processors apply one or more HB
pacing pulses at an impulse energy (as defined by an amplitude and
duration) set for the rough capture test. At operation 1104, the
impulse voltage is set to a relatively high initial value (e.g.,
7.5V) and a relatively large negative step size (e.g., -1.0V).
[0229] At 1106, the one or more processors measures response data
for a corresponding response characteristic, also referred to as an
evoked response (ER) characteristic of interest. More generally,
the one or more processors, in response to applying the first
pacing impulse, collect first response data using at least one
sensing electrode configured to sense electrical activity of the
heart.
[0230] In addition, at 1106, the one or more processors determine
one or more response characteristics based on the measured
response. One response characteristic may represent an ER interval
from the time when the HB pacing pulse is delivered to a time when
onset of the evoked response is detected (also referred to as onset
ER interval). Optionally, the ER interval may be from the time when
the HB pacing pulse is delivered to a peak of the evoked response
(also referred to as stim-to-peak time). Optionally, the ER
interval may be from the time when the HB pacing pulses delivered
to an ending point of the evoked response (also referred to as
termination ER interval).
[0231] Additionally or alternatively, the response characteristic
may represent a maximum slope of the evoked response. For example,
the maximum slope may be identified as the point at which the
derivative of the evoked response is at a maximum level.
Additionally or alternatively, the response characteristic may
correspond to a morphology of the evoked response, an area under
the curve in the evoked response, a duration of the evoked
response, a maximum amplitude of the evoked response and the
like.
[0232] At 1106, the one or processors maintain a list associating
each HBP impulse level with the response characteristics.
Optionally, at 1106, the one or more processors may classify the
response to determine a type of capture that was achieved (e.g., in
S, Selective, Myo, LOC). Optionally, the one or more processors may
not necessarily classify the response into one of the various types
of capture, but instead may simply determine whether the HIS bundle
has been captured.
[0233] At 1108, the one or more processors determine whether the
process has reached the limit for the rough HBP test. For example,
upper and lower limits may be defined for the rough HBP test (e.g.,
7.5 V and a 0.5 V). At 1108, the one or more processors determine
whether the impulse voltage for the current HBP has reached the
lower limit. When the limit of the rough test has not been reached,
flow returns to 1110. Alternatively, when the limit of the rough
test is reached, flow continues to 1112.
[0234] At 1110, the one or more processors change the impulse level
of the HBP by a rough step. For example, the one or more processors
may decrease the impulse level by a negative rough step size (e.g.,
1.0 V). Thereafter, a new HBP is applied at the new impulse level
at 1104. The operations at 1104-1110 are repeated until the
decision at 1108 moves the flow to 1112. The operations at
1104-1110 build a list of HBP impulse levels with corresponding
response characteristics, where each of the response characteristic
is indicative of a corresponding type of capture achieved by the
HBP. Changes in the level of the response characteristic are
indicative of changes in a type of capture achieved by the HBP. For
example, when the voltage delivered at the HBP is relatively low,
the HBP may not achieve capture. When loss of capture is present,
the ER interval from the HBP to ER onset may be 140 ms or greater.
As another nonlimiting example, when the HBP achieves selective
capture, the ER interval from the HBP to ER onset may be between 80
ms and 140 ms. When the HBP achieves nonselective capture, the ER
interval may be between 110 ms and 80 ms. Embodiments herein record
the ER interval in connection with each level of the HBP as an
indication of a type of capture and/or whether a change in the type
of capture has occurred.
[0235] Additionally or alternatively, the response characteristic
may correspond to a maximum slope in the evoked response. Each type
of capture may exhibit a corresponding maximum ER slope, with at
least some types of capture exhibiting different maximum ER slopes
relative to one another. For example, the nonselective capture type
may exhibit a substantially greater maximum ER slope, as compared
to the maximum ER slope exhibited during myocardial only capture.
In addition, the maximum ER slope during selective capture may
substantially differ from the maximum ER slope during nonselective
capture or during myocardial only capture. When the maximum ER
slope is relatively constant between successive HBP, the process
may interpret the relatively constant condition as an indication
that the capture type is not changing. Alternatively, when the
maximum ER slope significantly changes between successive HBP, the
process interprets the relative change as an indication that the
capture type is changed. As a further example, when the maximum ER
slope exhibits a significant decrease (e.g., 20% or more reduction)
between successive HBP, the process may interpret the change as an
indication that the capture type has changed from nonselective to
myocardial only.
[0236] By way of example, embodiments herein may distinguish
between NS, MYO and LOC capture types by utilizing the ER interval
to identify the transition between MYO and LOC capture types and
then utilized the ER slope to identify transitions between NS and
MYO capture types.
[0237] At 1112, the one or more processors analyzes the results of
the rough HBP test to identify changes in the response
characteristics indicative of transitions between capture types.
For example, Table 5 illustrates examples of a collection of rough
HBP voltages and fine HBP voltages along with corresponding
measurements for ER intervals and ER slopes. Changes in the ER
interval, that exceed a limit or step between ranges, are
indicative of transitions between capture types. For example, a
capture type transition may be indicated when an ER interval
switches between first and second ER interval ranges associated
with different capture types (e.g., transitioning from a first ER
interval range of 60-80 milliseconds to a second ER interval range
of 80-140 ms). In the example of table 5, a change in the ER
interval is noted, during the rough HBP test, from 4 V to 3V,
thereby indicating a transition from nonselective capture to
selective capture, with 4V being the nonselective capture threshold
Also, during the rough HBP test, from 1 V to 0.5V, a second
transition occurs indicating a change from selective capture to
loss of capture, with 1V being the selective capture threshold
Additionally or alternatively, a transition between capture types
may be indicated by changes in the ER interval that exceed certain
percentage limits, such as a change of 25% or more between
successive HBP test may indicate a transition between capture
types.
[0238] Additionally or alternatively, the transitions in capture
type may be denoted by the changes in the ER slope. For example,
certain limits may be defined for ER slopes, where each ER slope
range is associated with the corresponding capture type. As another
example, a capture type transitions may be indicated by a
predetermined percentage change in an ER slope (e.g., a change of
20% or more reduction) (Table 2).
[0239] By way of example, in connection with TABLE 5, embodiments
herein may distinguish between NS, S and LOC capture types based on
the ER interval along, such that ER slope may not be utilized to
distinguish between NS, S and LOC capture types.
TABLE-US-00016 TABLE 5 HBP HBP Voltage ER ER Voltage ER ER (Rough
Test) Interval Slope (Fine Test) Interval Slope 7.0 V 65 ms 1 mV/ms
0.75 V 140 ms 1.1 mV/ms 6.0 V 65 ms 1 mV/ms 1.0 V 100 ms 1.1 mV/ms
5.0 V 65 ms 1 mV/ms 1.25 V 100 ms 1.1 mV/ms 4.0 V 65 ms 1 mV/ms
3.25 V 100 ms 1.1 mV/ms 3.0 V 100 ms 1.1 mV/ms 3.5 V 65 ms 1 mV/ms
2.0 V 100 ms 1.1 mV/ms 3.75 V 65 ms 1 mV/ms 1.0 V 100 ms 1.1 mV/ms
4.0 V 65 ms 1 mV/ms 0.5 V 140 ms 1.1 mV/ms 4.25 V 65 ms 1 mV/ms
[0240] By way of example, in connection with TABLE 6, embodiments
herein may distinguish between NS, MYO and LOC capture types by
utilizing the ER interval to identify the transition between MYO
and LOC capture types and then utilized the ER slope to identify
transitions between NS and MYO capture types.
TABLE-US-00017 TABLE 6 HBP HBP Voltage ER ER Voltage ER ER (Rough
Test) Interval Slope (Fine Test) Interval Slope 7.0 V 65 ms 1 mV/ms
0.75 V 140 ms 1.1 mV/ms 6.0 V 65 ms 1 mV/ms 1.0 V 65 ms 0.5 mV/ms
5.0 V 65 ms 1 mV/ms 1.25 V 65 ms 0.5 mV/ms 4.0 V 65 ms 1 mV/ms 3.25
V 65 ms 0.5 mV/ms 3.0 V 65 ms 0.5 mV/ms 3.5 V 65 ms 1 mV/ms 2.0 V
65 ms 0.5 mV/ms 3.75 V 65 ms 1 mV/ms 1.0 V 65 ms 0.5 mV/ms 4 V 65
ms 1 mV/ms 0.5 V 140 ms 1.1 mV/ms 4.25 V 65 ms 1 mV/ms
[0241] At 1112, the one or more processors identify one or more
transition points indicated by the response characteristics. In the
example of table 5, transition points are indicated at 4 V and 1 V.
Accordingly, the one or more processors define a first HBP fine
test generally centered about the lower transition point at 1.0 V
and a second HBP fine test generally centered about the upper
transition point at 4.0 V. At 1112, the one or more processors
define upper and lower limits for each fine test. For example, the
upper and lower limits may be set to be a predetermined voltage
amount above and below the voltage identified in the rough HBP test
as a transition point. In the above example, the upper and lower
limits for a first fine test are defined at 0.75 V and 1.2 V,
namely 0.25 V above and below the transition point of 1.0 V
identified in the rough HBP test.
[0242] As another example above, upper and lower limits are defined
for a second fine HBP test at 3.25 V and 4.25 V, namely 0.25 V
above the transition point of 4.0 V minus the rough decremental
step size (4V-1V+0.25V=3.25V) and 0.25 V above the transition point
of 4.0 V. The upper and lower limits for the second fine HBP test
are not necessarily evenly distributed about the transition point
identified during the rough HBP test.
[0243] At 1114, the one or more processors apply one or more HB
pacing pulses at an impulse level set for the first fine capture
test. Continuing the example of table 5, the first HBP voltage is
set at 0.75 V.
[0244] At 1116, the one or more processors measure a corresponding
evoked response to the HBP. In addition, at 1116, the one or more
processors determine one or more response characteristic based on
the measured response (e.g., ER interval, ER slope). Additionally
or alternatively, the response characteristic may correspond to a
morphology of the evoked response, an area under the curve in the
evoked response, a duration of the evoked response, a maximum
amplitude of the evoked response and the like.
[0245] At 1116, the one or processors updates the list associating
each HBP impulse level, from the fine HBP test, with the
corresponding response characteristics. At 1118, the one or more
processors determine whether the process has reached the limit for
the fine HBP test. For example, upper and lower limits may be
defined for the first fine HBP test (e.g., 0.75 V and 1.25 V) with
a 0.25 V step between successive HBPs. At 1118, the one or more
processors determine whether the impulse voltage for the current
HBP has reached the lower limit. When the limit of the fine test
has not been reached, flow returns to 1120. In addition, when the
limit of the first fine test has been reached, the one or more
processors determine whether additional fine test should be
performed. In the above example, first and second fine test are to
be applied. Accordingly, once the first fine test has been
completed, flow returns to 1114 and the operations at 1114-1120 are
repeated for the second fine test with upper and lower limits set
at 3.25 V and 4.25 V, and with a 0.25 V step between successive
HBPs. When all of the fine test have been completed, flow moves to
1122.
[0246] At 1122, the one or more processors analyze the results
recorded in the table and set the HBP based on the measured
responses. For example, in the above table 5, the one or more
processors may determine that, at least 1.0 V is needed to achieve
selective capture, with voltage levels below 1.0 V resulting in
loss of capture. In addition, from the results recorded in table 5,
the one or more processors may determine that a stimulus level of
3.5 V is necessary to achieve nonselective capture, with voltage
levels above 3.5 V resulting in nonselective capture. The final
pacing pulse amplitude is programmed based on the capture threshold
of either selective or nonselective capture, whichever is lower,
plus a safety margin programmed by the user in clinic. For example,
in the above table 5, given a safety margin of 1V, the final pacing
pulse amplitude would be programmed to 2.0V (1.0V for selective
capture+1V safety margin). In another example, in the above Table
6, given a safety margin of 1V, the final pacing amplitude would be
programmed to 4.5V since only nonselective capture is available and
the nonselective capture threshold is 3.5V.
[0247] In the process of FIG. 11, the rough HBP test is implemented
in a decreasing manner, in which a maximum/upper voltage is
initially used and stepped down at each successive HBP pulse
applied during the rough test. The fine HBP test is implemented in
an increasing manner, in which a minimum/lowest voltage is
initially used and stepped up at each successive HBP pulse applied
during the fine test. In the foregoing example, a large transition
steps from 1.25 V up to 3.25 V when switching from the fine test
surrounding the lower transition point in the rough HBP up to the
upper transition point in the rough HBP.
[0248] The foregoing search approach can be applied to identify
thresholds for any or all types of capture associated with a
patient. For example, it may be desirable to first identify a
nonselective capture threshold and/or upper and lower limits for
non-selective capture. Next, the process may be repeated to
identify a selective capture threshold and/or upper and lower
limits for selective capture. Next, the process may be repeated to
identify a myocardial only capture threshold and/or upper and lower
limits for myocardial only capture.
[0249] It should be appreciated that the foregoing threshold search
method is provided merely as an example search method that may be
used in implementations of the present disclosure. Moreover, to the
extent any specific values are included in the foregoing
description (e.g., for the initial voltage, initial step size, and
the like), such values are included only as examples and should not
be viewed as limiting.
[0250] As explained herein, in accordance with another aspect
herein, a method is provided for identifying pacing thresholds and
programming a stimulation device for His bundle pacing (HBP), the
stimulation device including a pulse generator, a stimulating
electrode in proximity to a His bundle of a patient heart, and at
least one sensing electrode adapted to sense electrical activity of
the patient heart. The method comprises: applying, using the pulse
generator and stimulating electrode, a HBP pulse having an impulse
energy to the His bundle; in response to the applying a first
pacing impulse, measuring response data for a corresponding evoked
response using the at least one sensing electrode; determining a
response characteristic based on the response data; adjusting the
impulse energy and repeating the applying, measuring and
determining, wherein the impulse energy is adjusted in a
non-sequential manner between HBP pulses; identifying a change in
the response characteristic indicative of a change from a first
capture type and a second capture type; and setting one or more
parameters of a HBP therapy based on the change in the response
characteristic.
[0251] In accordance with other aspects herein, the repeating the
applying, measuring, determining, and adjusting obtains a
collection of response characteristics for a collection of HBP
pulses at corresponding different impulse energies. Additionally or
alternatively, the adjusting in the non-sequential manner includes
at least one rough energy adjustment between first and second HBP
pulses and at least one fine energy adjustment between third and
fourth HBP pulses. Additionally or alternatively, the at least one
rough energy adjustment includes a voltage step-up of at least 1.0V
between the first and second HBP pulses and the at least one fine
energy adjustment includes a voltage step-down of no more than
0.25V between the third and fourth HBP pulses. Additionally or
alternatively, the adjusting applies the at least one rough energy
adjustment during a rough HBP test between upper and lower rough
limits and applies the at least one fine energy adjustment during a
fine HBP test between upper and lower fine limits, the upper and
lower fine limits defined based on a transition point identified
during the rough HBP test. Additionally or alternatively, the
identifying further comprises identifying a rough transition point
based on the response characteristic associated with the first and
second HBP pulses separated by the at least one rough energy
adjustment and refining the rough transition point to a fine
transition point based on the response characteristic associated
with the third and fourth HBP pulses separated by the at least one
fine energy adjustment.
[0252] In accordance with new and unique aspects herein, a system
is provided. The system comprises: a HIS electrode configured to be
located proximate to the HIS bundle and to at least partially
define a HIS sensing channel; memory to store cardiac activity (CA)
signals obtained over the HIS sensing channel, the memory to store
program instructions; and one or more processors that, when
executing the program instructions, are configured for: applying,
using a pulse generator and a stimulating electrode, a HBP pulse
having an impulse energy to the His bundle; in response to applying
a first pacing impulse, measuring response data for a corresponding
evoked response using at least one sensing electrode; determining a
response characteristic based on the response data; adjusting the
impulse energy and repeating the applying, measuring and
determining, wherein the impulse energy is adjusted in a
non-sequential manner between HBP pulses; identifying a change in
the response characteristic indicative of a change from a first
capture type and a second capture type; and setting one or more
parameters of a HBP therapy based on the change in the response
characteristic.
[0253] Additionally or alternatively, the one or more processors
repeat the applying, measuring, determining, and adjusting to
obtain a collection of response characteristics for a collection of
HBP pulses at corresponding different impulse energies.
Additionally or alternatively, the adjusting in the non-sequential
manner includes at least one rough energy adjustment between first
and second HBP pulses and at least one fine energy adjustment
between third and fourth HBP pulses. Additionally or alternatively,
the at least one rough energy adjustment includes a voltage step-up
of at least 1.0V between the first and second HBP pulses and the at
least one fine energy adjustment includes a voltage step-down of no
more than 0.25V between the third and fourth HBP pulses.
Additionally or alternatively, the adjusting applies the at least
one rough energy adjustment during a rough HBP test between upper
and lower rough limits and applies the at least one fine energy
adjustment during a fine HBP test between upper and lower fine
limits, the upper and lower fine limits defined based on a
transition point identified during the rough HBP test. Additionally
or alternatively, the identifying further comprises identifying a
rough transition point based on the response characteristic
associated with the first and second HBP pulses separated by the at
least one rough energy adjustment and refining the rough transition
point to a fine transition point based on the response
characteristic associated with the third and fourth HBP pulses
separated by the at least one fine energy adjustment.
CLOSING STATEMENTS
[0254] It should be clearly understood that the various
arrangements and processes broadly described and illustrated with
respect to the Figures, and/or one or more individual components or
elements of such arrangements and/or one or more process operations
associated of such processes, can be employed independently from or
together with one or more other components, elements and/or process
operations described and illustrated herein. Accordingly, while
various arrangements and processes are broadly contemplated,
described and illustrated herein, it should be understood that they
are provided merely in illustrative and non-restrictive fashion,
and furthermore can be regarded as but mere examples of possible
working environments in which one or more arrangements or processes
may function or operate.
[0255] As will be appreciated by one skilled in the art, various
aspects may be embodied as a system, method, or computer (device)
program product. Accordingly, aspects may take the form of an
entirely hardware embodiment or an embodiment including hardware
and software that may all generally be referred to herein as a
"circuit," "module" or "system." Furthermore, aspects may take the
form of a computer (device) program product embodied in one or more
computer (device) readable storage medium(s) having computer
(device) readable program code embodied thereon.
[0256] Any combination of one or more non-signal computer (device)
readable medium(s) may be utilized. The non-signal medium may be a
storage medium. A storage medium may be, for example, an
electronic, magnetic, optical, electromagnetic, infrared, or
semiconductor system, apparatus, or device, or any suitable
combination of the foregoing. More specific examples of a storage
medium would include the following: a portable computer diskette, a
hard disk, a random access memory (RAM), a dynamic random access
memory (DRAM), a read-only memory (ROM), an erasable programmable
read-only memory (EPROM or Flash memory), a portable compact disc
read-only memory (CD-ROM), an optical storage device, a magnetic
storage device, or any suitable combination of the foregoing.
[0257] Program code for carrying out operations may be written in
any combination of one or more programming languages. The program
code may execute entirely on a single device, partly on a single
device, as a stand-alone software package, partly on single device
and partly on another device, or entirely on the other device. In
some cases, the devices may be connected through any type of
network, including a local area network (LAN) or a wide area
network (WAN), or the connection may be made through other devices
(for example, through the Internet using an Internet Service
Provider) or through a hard wire connection, such as over a USB
connection. For example, a server having a first processor, a
network interface, and a storage device for storing code may store
the program code for carrying out the operations and provide this
code through its network interface via a network to a second device
having a second processor for execution of the code on the second
device.
[0258] Aspects are described herein with reference to the figures,
which illustrate example methods, devices, and program products
according to various example embodiments. These program
instructions may be provided to a processor of a general purpose
computer, special purpose computer, or other programmable data
processing device or information handling device to produce a
machine, such that the instructions, which execute via a processor
of the device implement the functions/acts specified. The program
instructions may also be stored in a device readable medium that
can direct a device to function in a particular manner, such that
the instructions stored in the device readable medium produce an
article of manufacture including instructions which implement the
function/act specified. The program instructions may also be loaded
onto a device to cause a series of operational steps to be
performed on the device to produce a device implemented process
such that the instructions which execute on the device provide
processes for implementing the functions/acts specified.
[0259] The units/modules/applications herein may include any
processor-based or microprocessor-based system including systems
using microcontrollers, reduced instruction set computers (RISC),
application specific integrated circuits (ASICs),
field-programmable gate arrays (FPGAs), logic circuits, and any
other circuit or processor capable of executing the functions
described herein. Additionally or alternatively, the
modules/controllers herein may represent circuit modules that may
be implemented as hardware with associated instructions (for
example, software stored on a tangible and non-transitory computer
readable storage medium, such as a computer hard drive, ROM, RAM,
or the like) that perform the operations described herein. The
above examples are exemplary only, and are thus not intended to
limit in any way the definition and/or meaning of the term
"controller." The units/modules/applications herein may execute a
set of instructions that are stored in one or more storage
elements, in order to process data. The storage elements may also
store data or other information as desired or needed. The storage
element may be in the form of an information source or a physical
memory element within the modules/controllers herein. The set of
instructions may include various commands that instruct the
modules/applications herein to perform specific operations such as
the methods and processes of the various embodiments of the subject
matter described herein. The set of instructions may be in the form
of a software program. The software may be in various forms such as
system software or application software. Further, the software may
be in the form of a collection of separate programs or modules, a
program module within a larger program or a portion of a program
module. The software also may include modular programming in the
form of object-oriented programming. The processing of input data
by the processing machine may be in response to user commands, or
in response to results of previous processing, or in response to a
request made by another processing machine.
[0260] It is to be understood that the subject matter described
herein is not limited in its application to the details of
construction and the arrangement of components set forth in the
description herein or illustrated in the drawings hereof. The
subject matter described herein is capable of other embodiments and
of being practiced or of being carried out in various ways. Also,
it is to be understood that the phraseology and terminology used
herein is for the purpose of description and should not be regarded
as limiting. The use of "including," "comprising," or "having" and
variations thereof herein is meant to encompass the items listed
thereafter and equivalents thereof as well as additional items.
[0261] It is to be understood that the above description is
intended to be illustrative, and not restrictive. For example, the
above-described embodiments (and/or aspects thereof) may be used in
combination with each other. In addition, many modifications may be
made to adapt a particular situation or material to the teachings
herein without departing from its scope. While the dimensions,
types of materials and coatings described herein are intended to
define various parameters, they are by no means limiting and are
illustrative in nature. Many other embodiments will be apparent to
those of skill in the art upon reviewing the above description. The
scope of the embodiments should, therefore, be determined with
reference to the appended claims, along with the full scope of
equivalents to which such claims are entitled. In the appended
claims, the terms "including" and "in which" are used as the
plain-English equivalents of the respective terms "comprising" and
"wherein." Moreover, in the following claims, the terms "first,"
"second," and "third," etc. are used merely as labels, and are not
intended to impose numerical requirements on their objects or order
of execution on their acts.
[0262] All references, including publications, patent applications
and patents, cited herein are hereby incorporated by reference to
the same extent as if each reference were individually and
specifically indicated to be incorporated by reference and were set
forth in its entirety herein.
* * * * *