U.S. patent application number 13/164508 was filed with the patent office on 2011-10-13 for apparatus and method for optimizing atrioventricular delay.
Invention is credited to Jiang Ding, Jeffrey E. Stahmann, Yinghong Yu.
Application Number | 20110251655 13/164508 |
Document ID | / |
Family ID | 36975560 |
Filed Date | 2011-10-13 |
United States Patent
Application |
20110251655 |
Kind Code |
A1 |
Yu; Yinghong ; et
al. |
October 13, 2011 |
APPARATUS AND METHOD FOR OPTIMIZING ATRIOVENTRICULAR DELAY
Abstract
Systems and methods to optimize atrioventricular delay during
sensing or pacing of the atrium and for a plurality of sensed rates
or pacing rates. In one example, a paced atrioventricular delay is
calculated using a sensed atrioventricular interval and a paced
atrioventricular interval. In another example, a plurality of paced
atrioventricular delays for different pacing rates can be
calculated. In another example embodiment, a plurality of sensed
atrioventricular delays for different sensing rates can be
calculated. Combinations of the various systems and methods are
also possible.
Inventors: |
Yu; Yinghong; (Shoreview,
MN) ; Ding; Jiang; (Shoreview, CA) ; Stahmann;
Jeffrey E.; (Ramsey, MN) |
Family ID: |
36975560 |
Appl. No.: |
13/164508 |
Filed: |
June 20, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11126490 |
May 11, 2005 |
7966066 |
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13164508 |
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Current U.S.
Class: |
607/25 |
Current CPC
Class: |
A61N 1/3682 20130101;
A61N 1/3706 20130101; A61N 1/3627 20130101 |
Class at
Publication: |
607/25 |
International
Class: |
A61N 1/365 20060101
A61N001/365 |
Claims
1. A method for operating a cardiac rhythm management device,
comprising: delivering cardiac resynchronization therapy with a
selected atrioventricular delay, wherein the cardiac
resynchronization therapy includes delivering ventricular pacing
upon expiration of a selected atrioventricular delay AVD.sub.s
after an atrial sense and upon expiration of a selected
atrioventricular delay AVD.sub.p after an atrial pace; sensing and
timing a plurality of sensed and paced intrinsic atrioventricular
intervals at a plurality of rates, wherein a sensed intrinsic
atrioventricular interval is the interval between an atrial sense
and a ventricular sense and wherein a paced intrinsic
atrioventricular interval is the interval between an atrial pace
and a ventricular sense; calculating a plurality of AVD.sub.s
values and AVD.sub.p values for use in delivering resynchronization
therapy at different atrial rates based on the plurality of
atrioventricular intervals; calculating a plurality of different
AVD.sub.s values for each of a plurality of a sensed atrial rates
by: 1) operating in a ventricular pacing mode with atrial sensing
but no atrial pacing, 2) when the currently sensed atrial rate
corresponds to one of the plurality of sensed atrial rates,
calculating and storing an AVD.sub.s value for that sensed atrial
rate as a function of the intrinsic atrioventricular interval, 3)
storing each calculated AVD.sub.s value with an associated
specified expiration interval so that the AVD.sub.s value expires
after the expiration interval lapses, 4) when the currently sensed
atrial rate corresponds to one of the plurality of sensed atrial
rates for which the AVD.sub.s value has been previously calculated
but has expired, recalculating and storing the AVD.sub.s value for
that sensed atrial rate; calculating a plurality of different
AVD.sub.p values for each of a plurality of a paced atrial rates
by: 1) operating in a ventricular pacing mode with atrial pacing,
2) varying the atrial pacing rate to corresponds to each of the
plurality of paced atrial rates, and 3) calculating and storing an
AVD.sub.p value for each paced atrial rate as a function of the
intrinsic atrioventricular interval measured at each particular
atrial pacing rate; and, selecting one of the plurality of stored
AVD.sub.s values and AVD.sub.p values for use in delivering cardiac
resynchronization pacing based on an interval between atrial beats
of consecutive cardiac cycles.
2. The method of claim 1, further comprising selecting one of the
plurality of atrioventricular delay values based on a current
sensed rate after switching from a ventricular pacing mode with
atrial pacing to a ventricular pacing mode with no atrial
pacing.
3. The method of claim 1, further comprising selecting one of the
plurality of atrioventricular delay values based on a current
pacing rate after switching from a ventricular pacing mode with no
atrial pacing to a ventricular pacing mode with atrial pacing.
4. The method of claim 1, further comprising selecting pacing the
heart at increasing rates, sensing and timing a paced
atrioventricular interval at each increased pacing rate, and
calculating the plurality of atrioventricular delay values based on
the associated paced atrioventricular interval.
5. The method of claim 1, further comprising selecting determining
whether a previous value has been calculated or has expired for the
plurality of atrioventricular delay values.
6. The method of claim 1, further comprising storing an
atrioventricular delay value if the previous value has not been
calculated or has expired.
7. The method of claim 1, further comprising selecting between a
sensed atrioventricular delay and a paced atrioventricular delay
based on a mode in which the cardiac resynchronization device is
operating.
8. The method of claim 1, further comprising: calculating an
AVD.sub.s value for a particular atrial rate as a function of a
sensed intrinsic atrioventricular interval AVI.sub.s measured at
that particular atrial rate as AVD.sub.s=K1(AVI.sub.s)-K2; and,
calculating an AVD.sub.p value for a particular atrial pacing rate
as a function of a paced intrinsic atrioventricular interval
AVI.sub.p measured at that particular atrial pacing rate as
AVD.sub.p=K1(AVI.sub.p)-K2.
9. The method of claim 1, further comprising increasing the atrial
pacing rate through a range of different pacing rates in order to
collect paced intrinsic atrioventricular intervals at different
atrial pacing rates and calculate corresponding AVD.sub.p
values.
10. The method of claim 1, further comprising opportunistically
calculating corresponding AVD.sub.s values as atrial senses occur
and subsequently increase the atrial pacing rate by a specified
amount above the intrinsic atrial rate to calculate an AVD.sub.p
value.
11. A method for operating a cardiac rhythm management device,
comprising: delivering cardiac resynchronization therapy with a
selected atrioventricular delay, wherein the cardiac
resynchronization therapy includes delivering ventricular pacing
upon expiration of a selected atrioventricular delay AVD.sub.s
after an atrial sense and upon expiration of a selected
atrioventricular delay AVD.sub.p after an atrial pace; sensing and
timing a plurality of sensed and paced intrinsic atrioventricular
intervals at a plurality of rates, wherein a sensed intrinsic
atrioventricular interval is the interval between an atrial sense
and a ventricular sense and wherein a paced intrinsic
atrioventricular interval is the interval between an atrial pace
and a ventricular sense; calculating a plurality of AVD.sub.s
values and AVD.sub.p values for use in delivering resynchronization
therapy at different atrial rates based on the plurality of
atrioventricular intervals; calculating a plurality of different
AVD.sub.s values for each of a plurality of a sensed atrial rates
by: 1) operating in a ventricular pacing mode with atrial sensing
but no atrial pacing, 2) when the currently sensed atrial rate
corresponds to first sensed atrial rate, calculating and storing an
AVD.sub.s value for the first sensed atrial rate as a function of
the intrinsic atrioventricular interval, 3) when the currently
sensed atrial rate corresponds to second sensed atrial rate,
calculating and storing an AVD.sub.s value for the second sensed
atrial rate as a function of the intrinsic atrioventricular
interval, 4) calculating and storing a plurality of AVD.sub.s
values by linearly interpolating between the calculated AVD.sub.s
values for the first and second sensed atrial rates, 5) storing
each calculated AVD.sub.s value with an associated specified
expiration interval so that the AVD.sub.s value expires after the
expiration interval lapses, 6) when the currently sensed atrial
rate corresponds to one of the plurality of sensed atrial rates for
which the AVD.sub.s value has been previously calculated but has
expired, recalculating and storing the AVD.sub.s value for that
sensed atrial rate; calculating a plurality of different AVD.sub.p
values for each of a plurality of a paced atrial rates by: 1)
operating in a ventricular pacing mode with atrial pacing, 2)
varying the atrial pacing rate to corresponds to each of the
plurality of paced atrial rates, and 3) calculating and storing an
AVD.sub.p value for each paced atrial rate as a function of the
intrinsic atrioventricular interval measured at each particular
atrial pacing rate; and, selecting one of the plurality of stored
AVD.sub.s values and AVD.sub.p values for use in delivering cardiac
resynchronization pacing based on an interval between atrial beats
of consecutive cardiac cycles.
12. The method of claim 11, further comprising selecting one of the
plurality of atrioventricular delay values based on a current
sensed rate after switching from a ventricular pacing mode with
atrial pacing to a ventricular pacing mode with no atrial
pacing.
13. The method of claim 11, further comprising selecting one of the
plurality of atrioventricular delay values based on a current
pacing rate after switching from a ventricular pacing mode with no
atrial pacing to a ventricular pacing mode with atrial pacing.
14. The method of claim 11, further comprising selecting pacing the
heart at increasing rates, sensing and timing a paced
atrioventricular interval at each increased pacing rate, and
calculating the plurality of atrioventricular delay values based on
the associated paced atrioventricular interval.
15. The method of claim 11, further comprising selecting
determining whether a previous value has been calculated or has
expired for the plurality of atrioventricular delay values.
16. The method of claim 11, further comprising storing an
atrioventricular delay value if the previous value has not been
calculated or has expired.
17. The method of claim 11, further comprising selecting between a
sensed atrioventricular delay and a paced atrioventricular delay
based on a mode in which the cardiac resynchronization device is
operating.
18. The method of claim 11, further comprising: calculating an
AVD.sub.s value for a particular atrial rate as a function of a
sensed intrinsic atrioventricular interval AVI.sub.s measured at
that particular atrial rate as AVD.sub.s=K1(AVI.sub.s)-K2; and,
calculating an AVD.sub.p value for a particular atrial pacing rate
as a function of a paced intrinsic atrioventricular interval
AVI.sub.p measured at that particular atrial pacing rate as
AVD.sub.p=K1(AVI.sub.p)-K2.
19. The method of claim 11, further comprising increasing the
atrial pacing rate through a range of different pacing rates in
order to collect paced intrinsic atrioventricular intervals at
different atrial pacing rates and calculate corresponding AVD.sub.p
values.
20. The method of claim 11, further comprising opportunistically
calculating corresponding AVD.sub.s values as atrial senses occur
and subsequently increase the atrial pacing rate by a specified
amount above the intrinsic atrial rate to calculate an AVD.sub.p
value.
Description
CLAIM OF PRIORITY
[0001] This application is a continuation of and claims the benefit
of priority under 35 U.S.C. .sctn.120 to U.S. patent application
Ser. No. 11/126,490, filed on May 11, 2005, which is hereby
incorporated by reference herein in its entirety.
TECHNICAL FIELD
[0002] The present invention is directed to cardiac
resynchronization therapy systems. More specifically, the present
invention is directed to systems and methods to optimize
atrioventricular delay during cardiac resynchronization
therapy.
BACKGROUND
[0003] The heart is a muscular organ comprising multiple chambers
that operate in concert to circulate blood throughout the body's
circulatory system. As shown in FIG. 1, the heart 100 includes a
right-side portion or pump 102 and a left-side portion or pump 104.
The right-side portion 102 includes a right atrium 106 and a right
ventricle 108. Similarly, the left-side portion 104 includes a left
atrium 110 and a left ventricle 112 separated by an
interventricular septum 105. Oxygen-depleted blood returning to the
heart 100 from the body collects in the right atrium 106. When the
right atrium 106 fills, the oxygen-depleted blood passes into the
right ventricle 108 where it can be pumped to the lungs (not
shown") via the pulmonary arteries 117.
[0004] Within the lungs, waste products such as carbon dioxide are
removed from the blood and expelled from the body and oxygen is
transferred to the blood. Oxygen-rich blood returning to the heart
100 from the lungs via the pulmonary veins (not shown) collects in
the left atrium 110. The circuit between the right-side portion
102, the lungs, and the left atrium 110 is generally referred to as
the pulmonary circulation. After the left atrium 110 fills, the
oxygen-rich blood passes into the left ventricle 112 where it can
be pumped throughout the entire body. In so doing, the heart 100 is
able to supply oxygen to the body and facilitate the removal of
waste products from the body.
[0005] To circulate blood throughout the body's circulatory system
as described above, a beating heart performs a cardiac cycle that
includes a systolic phase and a diastolic phase. During the
systolic phase, or systole, the ventricular muscle cells of the
right and left ventricles 108 and 112 contract to pump blood
through the pulmonary circulation and throughout the body,
respectively. Conversely, during the diastolic phase, or diastole,
the ventricular muscle cells of the right and left ventricles 108
and 112 relax, during which the right and left atriums 106 and 110
contract to force blood into the right and left ventricles 108 and
112, respectively. Typically, the cardiac cycle occurs at a
frequency between 60 and 100 cycles per minute and can vary
depending on physical exertion and/or emotional stimuli, such as
pain or anger.
[0006] The contractions of the muscular walls of each chamber of
the heart 100 are controlled by a complex conduction system that
propagates electrical signals to the heart muscle tissue to
effectuate the atrial and ventricular contractions necessary to
circulate the blood. As shown in FIG. 2, the complex conduction
system includes an atrial node 120 (the sinoatrial node) and a
ventricular node 122 (the atrioventricular node). The sinoatrial
node 120 initiates an electrical impulse that spreads through the
muscle tissues of the right and left atriums 106 and 110 and the
atrioventricular node 122. As a result, the right and left atriums
106 and 110 contract to pump blood into the right and left
ventricles 108 and 112, as discussed above.
[0007] At the atrioventricular node 122, the electrical signal is
momentarily delayed before propagating through the right and left
ventricles 108 and 112. Within the right and left ventricles 108
and 112, the conduction system includes right and left bundle
branches 126 and 128 that extend from the atrioventricular node 122
via the Bundle of His 124. The electrical impulse spreads through
the muscle tissues of the right and left ventricles 108 and 112 via
the right and left bundle branches 126 and 128, respectively. As a
result, the right and left ventricles 108, 112 contract to pump
blood throughout the body as discussed above.
[0008] Normally, the muscular walls of each chamber of the heart
100 contract synchronously in a precise sequence to efficiently
circulate the blood as described above. In particular, both the
right and left atriums 106 and 110 contract and relax
synchronously. Shortly after the atrial contractions, both the
right and left ventricles 108 and 112 contract and relax
synchronously. Several disorders or arrhythmias of the heart can
prevent the heart from operating normally, such as, blockage of the
conduction system, heart disease (e.g., coronary artery disease),
abnormal heart valve function, or heart failure.
[0009] Blockage in the conduction system can cause a slight or
severe delay in the electrical impulses propagating through the
atrioventricular node 122, causing inadequate ventricular
contraction, relaxation, and filling. In situations where the
blockage is in the ventricles (e.g., the right and left bundle
branches 126 and 128), the right and/or left ventricles 108 and 112
can only be excited through slow muscle tissue conduction. As a
result, the muscular walls of the affected ventricle (108 and/or
112) do not contract synchronously (known as asynchronous
contraction), thereby reducing the overall effectiveness of the
heart 100 to pump oxygen-rich blood throughout the body.
[0010] Various medical procedures have been developed to address
heart disorders. In particular, cardiac resynchronization therapy
("CRT") can be used to improve the conduction pattern and sequence
of the heart 100. CRT involves the use of an artificial electrical
stimulator that is surgically implanted within the patient's body.
Leads from the stimulator can be affixed at a desired location
within the heart 100 to effectuate synchronous atrial and/or
ventricular contractions. Typically, the location of the leads, or
the stimulation site, is selected based upon the severity and/or
location of the blockage. Electrical stimulation signals can be
delivered to resynchronize the heart, thereby improving cardiac
performance.
[0011] One important parameter associated with CRT is
atrioventricular delay or "AV delay," which is the programmed time
interval between a paced or sensed atrial event and the
corresponding paced or sensed ventricular event. Referring to FIGS.
3-7, an example timeline and method are shown for calculating an AV
delay.
[0012] Referring to FIG. 3, a specific instant in atrial ("A") and
ventricle ("V") activity is illustrated. For example, the sensing
of atrial ("A.sub.s") activity and sensing of ventricle ("V.sub.s")
activity during intrinsic heart activity is shown for a single
heartbeat. The time A.sub.s represents when atrial depolarization
(or electrical activation) is sensed. The time V.sub.s represents
when ventricular depolarization is sensed. The interval between
A.sub.s and V.sub.s is the sensed atrioventricular interval
("AVI.sub.s").
[0013] The AVI.sub.s can be used to calculate an optimal AV delay
for ventricular pacing during intrinsic or sensed atrial
contraction ("AVD.sub.s"), as shown in FIG. 4, using various
techniques. For example, methods described in U.S. Pat. No.
6,144,880 to Ding et al. and U.S. patent application Ser. Nos.
10/314,899 and 10/314,910 to Yu et al., all of which are hereby
incorporated by reference in their entireties, can be used to
calculate AVD.sub.s from AVI.sub.s. Equation 1 below generally
illustrates one possible relationship between AVI.sub.s and an
optimized AVD.sub.s.
AVD.sub.s=K1(AVI.sub.s)-K2 (1)
The constants K1 and K2 may vary depending on the interval measured
and patient diversity. See U.S. Pat. No. 6,144,880.
[0014] In another example, U.S. patent application Ser. No.
10/352,780 to Ding et al., which is hereby incorporate by
reference, describes methods for calculating optimal AVD.sub.s. For
example, the following equation can be used to calculate an optimal
AVD.sub.s: AVD.sub.s=k.sub.1AV.sub.Rs+k.sub.2AV.sub.Ls, where
AV.sub.Rs is the interval between atrial sense and right
ventricular sense, and AV.sub.Ls is the interval between atrial
sense and left ventricular sense.
[0015] Referring now to FIG. 5, an embodiment in which the atrium
is paced ("A.sub.p") is illustrated. A.sub.p represents the
introduction of an electrical impulse to the atrium, and, as
previously noted, V.sub.s represents sensing of intrinsic
ventricular activity. The interval between A.sub.p and V.sub.s is
the atrioventricular interval during atrial pacing and ventricular
sensing ("AVI.sub.p").
[0016] As shown in FIG. 6, a difference between AVI.sub.s and
AVI.sub.p, labeled as the offset, can be calculated using Equation
2.
offset=AVI.sub.p-AVI.sub.s (2)
Using this offset, the optimal atrioventricular delay for atrial
and ventricular pacing ("AVD.sub.p") can be calculated using
Equation 3.
AVD.sub.p=AVD.sub.s+offset (3)
[0017] Referring now to FIG. 7, using Equations 2 and 3 described
above, an example method is shown to calculate the AVD.sub.p for a
CRT device. In operation 310, the AVI.sub.s is measured by the CRT
device. In operation 320, the optimal AVD.sub.s for sensed atrium
and paced ventricle is calculated as described above. Then, in
operation 330, the atrium is paced for one or more beats. In
operation 340, the AVI.sub.p is measured. Next, the offset is
calculated in operation 350 using Equation 2 above. Finally, in
operation 360, the optimal AVD.sub.p for paced atrium and paced
ventricle can be calculated using Equation 3.
[0018] Other methods can also be used to calculate an optimized
AVD.sub.p. For example, U.S. patent application Ser. No. 10/243,811
to Ding et al., which is hereby incorporated by reference in its
entirety, describes a method to calculate AVD.sub.p using
AVI.sub.p, according to the following Equation 4.
AVD.sub.p=K1(AVI.sub.p)-K2 (4)
[0019] The above example methods illustrated in Equations 1-4 allow
for the calculation of AVD.sub.s or AVD.sub.p using a fixed atrial
sensing or pacing rate. A typical pacing system uses a standard
pre-set AV delay when pacing a heart. Therefore, prior art systems
do not account for changes in atrioventricular delays associated
with changes in heart rate or pacing rate, or changes in the mode
in which the heart is being paced (e.g., changes from atrial
sensing to atrial pacing).
[0020] However, optimal AV delays can vary depending on the rate of
pacing and on whether the atrium is being sensed or paced. For
example, as illustrated in FIGS. 4 and 6, AVD.sub.s is usually
shorter than AVD.sub.p because when pacing the right atrium,
activation of the left atrium is further delayed. In order to
maintain the appropriate contraction sequence of the left atrium
and ventricle, the timing of left ventricular stimulation needs to
be delayed correspondingly, which necessitates a longer
AVD.sub.p.
[0021] The AV delay can have a significant impact on the
hemodynamic efficiency of the heart 100. AV delays of greater than
or less than optimal length can cause asynchronous contraction,
which can result in less oxygen-rich blood being pumped during each
stroke of the heart 100.
[0022] Therefore, there is a need for systems and methods that can
efficiently and accurately optimize AV delay, and utilize these AV
delays at different sensing and pacing rates and during different
pacing modes (e.g., atrial sensing or atrial pacing).
SUMMARY
[0023] The present invention is directed to cardiac
resynchronization therapy systems. More specifically, the present
invention is directed to systems and methods to optimize
atrioventricular delay during cardiac resynchronization
therapy.
[0024] According to one aspect, embodiments of the invention relate
to a cardiac resynchronization device associated with a heart, the
cardiac resynchronization device including a therapy module for
delivering resynchronization therapy to the heart, and a sensing
module and a timer module capable of sensing and timing a plurality
of atrioventricular intervals at a plurality of rates. The device
also includes a controller coupled to the timer module capable of
calculating a plurality of atrioventricular delays for
resynchronization therapy based on the plurality of
atrioventricular intervals, and a memory module capable of storing
the plurality of atrioventricular delays.
[0025] According to another aspect, embodiments of the invention
relate to method for optimizing atrioventricular delay for a
cardiac resynchronization device, including: measuring a plurality
of atrioventricular intervals of a heart at a plurality of rates;
calculating an atrioventricular delay for each of the plurality of
atrioventricular intervals; and storing the atrioventricular delay
for each of the plurality of atrioventricular intervals in a memory
of the cardiac resynchronization device.
[0026] According to yet another aspect, embodiments of the
invention relate to a method for optimizing atrioventricular delay
for a cardiac resynchronization device, including: pacing a heart
at a first rate; measuring a first atrioventricular interval;
calculating a first atrioventricular delay; storing the first
atrioventricular delay in a lookup table in a memory of the cardiac
resynchronization device; pacing the heart at a second rate greater
than the first rate; measuring a second atrioventricular interval;
calculating a second atrioventricular delay; and storing the second
atrioventricular delay in the lookup table in the memory of the
cardiac resynchronization device.
[0027] According to another aspect, embodiments of the invention
relate to a method for optimizing atrioventricular delay for
cardiac resynchronization therapy, including: measuring a first
atrioventricular interval at a first pacing rate, the first
atrioventricular interval spanning a first event corresponding to
atrial activity of an atrium and a second event corresponding to
ventricular activity of a ventricle of a heart; calculating a first
atrioventricular delay based on the first atrioventricular
interval; storing the first atrioventricular delay and the first
pacing rate in a lookup table in a memory of a cardiac
resynchronization device; measuring a second atrioventricular
interval at a second pacing rate; calculating a second
atrioventricular delay; and storing the second atrioventricular
delay and the second pacing rate in the lookup table in the memory
of the cardiac resynchronization device.
[0028] According to another aspect, embodiments of the invention
relate to a method for optimizing sensed atrioventricular delay for
a cardiac resynchronization device, including: measuring a first
sensed rate; determining if the first sensed rate exceeds a
threshold; and if the first sensed rate exceeds a threshold,
determining if a first sensed atrioventricular delay has not been
previously calculated or has expired for the first sensed rate. If
the first sensed atrioventricular delay has not been previously
calculated or has expired: measuring a first sensed
atrioventricular interval; calculating the first sensed
atrioventricular delay from the first sensed atrioventricular
interval; and storing the first sensed atrioventricular delay in a
memory of the cardiac resynchronization device.
[0029] According to yet another aspect, embodiments of the
invention relate to a method for optimizing sensed and paced
atrioventricular delays for a cardiac resynchronization device
associated with a heart, including: measuring a sensed
atrioventricular interval of the heart; pacing an atrium of the
heart; measuring a paced atrioventricular interval; and calculating
an offset based on the sensed atrioventricular interval and the
paced atrioventricular interval.
[0030] The above summary is not intended to describe each disclosed
embodiment or every implementation of the present invention. The
figures and detailed description that follow more particularly
exemplify embodiments of the invention. While certain embodiments
will be illustrated and described, the invention is not limited to
use in such embodiments.
DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a simplified illustration depicting primary
pumping components of a human heart.
[0032] FIG. 2 is a simplified illustration depicting a human heart
and the transmission paths over which a normal heart provides
depolarization waves to the heart chambers.
[0033] FIG. 3 is a timeline illustrating an example
atrioventricular interval between sensed atrial and ventricle
activity.
[0034] FIG. 4 is a timeline illustrating an example calculated
optimized atrioventricular delay for sensed atrial and paced
ventricular activity.
[0035] FIG. 5 is a timeline illustrating an example
atrioventricular interval between paced atrial and sensed ventricle
activity.
[0036] FIG. 6 is a timeline illustrating an example offset and an
example calculated optimized atrioventricular delay for paced
atrial and paced ventricular activity.
[0037] FIG. 7 is an example flow diagram for calculating an
atrioventricular delay.
[0038] FIG. 8 is a schematic/plan drawing of an example embodiment
of a cardiac rhythm management system coupled to a human heart.
[0039] FIG. 9 is an example flow diagram for calculating a
plurality of optimized atrioventricular delays for a paced atrium
at a plurality of pacing rates.
[0040] FIG. 10A is an example flow diagram for calculating a
plurality of optimized atrioventricular delays for a sensed atrium
at a plurality of sensed rates.
[0041] FIG. 10B is another example flow diagram for calculating a
plurality of optimized atrioventricular delays for a sensed atrium
at a plurality of sensed rates induced by pacing.
[0042] FIG. 11 is an example flow diagram for a cardiac rhythm
management system applying optimized sensed and paced
atrioventricular delays during a mode switch.
[0043] FIG. 12 is an example flow diagram for a cardiac rhythm
management system implementing optimized atrioventricular delay for
a plurality of pacing rates and for both atrial sensing and pacing
modes.
[0044] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the
invention.
DETAILED DESCRIPTION
[0045] The present invention generally relates to cardiac
resynchronization therapy systems. More specifically, the present
invention is directed to systems and methods to optimize
atrioventricular delay during cardiac resynchronization
therapy.
[0046] As used herein, the terms "intrinsic" and "sensed" mean the
natural or unprovoked activity of the heart such as, for example,
depolarization of the heart. The term "paced" is used herein to
mean stimulation of the heart caused by one or more electrical
impulses delivered to the heart by, for example, a cardiac rhythm
management ("CRM") system including a cardiac resynchronization
therapy ("CRT") device.
[0047] In addition, the term "atrioventricular interval," whether
sensed or paced, means an interval between an identifiable portion
of atrial electrical activity and an identifiable portion of
ventricular electrical activity. This interval can be measured
using various methods. For example, the interval AQ.sub.s* or
AQ.sub.p* (the interval between a sensed or paced atrial event and
the onset of the ventricular electrical event) or AVI.sub.s or
AVI.sub.p (the interval between a sensed or paced atrial event and
a sensed ventricular electrical event) can be used to measure the
atrioventricular interval. See, for example, U.S. Pat. No.
6,144,880 to Ding et al. and U.S. patent application Ser. Nos.
10/314,899 and 10/314,910 both to Yu et al. for example methods for
measuring the atrioventricular interval.
[0048] Embodiments of the present invention can be used to optimize
atrioventricular ("AV") delay ("AVD") during sensing or pacing of
the atrium and for a plurality of pacing rates. In one example
embodiment, a plurality of paced AV delays for different rates can
be calculated. In another example embodiment, a plurality of sensed
AV delays for different sensing rates can be calculated. In another
embodiment, a plurality of sensed AV delays for different sensing
rates are converted from paced AV delays calculated at different
pacing rates. In other embodiments, the sensed AV delays for
different sensing rates are calculated and populated as needed.
Combinations of the various embodiments are also possible.
[0049] The present systems and methods are described with respect
to implantable CRM systems, such as pacemakers,
cardioverter/defibrillators, pacer/defibrillators, and
multi-chamber and/or multi-site (in a single or multiple heart
chambers) CRT devices. Such CRT devices are included within CRM
systems even though the CRT devices need not necessarily modulate
heart rate. Such CRT devices may instead provide
contraction-evoking stimulations that establish or modify the
conduction path of propagating depolarizations to obtain more
efficient pumping of the heart. Moreover, the present systems and
methods also find application in other implantable medical devices,
and in unimplanted ("external") devices, including, but not limited
to, external pacemakers, cardioverter/defibrillators,
pacer/defibrillators, multi-chamber and/or multi-site CRT devices,
monitors, programmers, and recorders, whether such devices are used
for providing a diagnostic, a therapy, or both.
[0050] The methods disclosed herein may be manually implemented by,
for example, a caregiver. Alternatively, the CRT device may
automatically perform one or more of the methods. The CRT device
may perform one or more of the methods subsequent to implantation
and prior to delivery of therapy. In addition, the CRT device may
perform one or more of the methods at selected or periodic
intervals in order to re-optimize operating parameters.
I. System
[0051] Referring now to FIG. 8, one embodiment illustrating various
components of a CRM system 205 is shown along with the heart 100.
In this embodiment, the CRM system 205 includes, among other
elements, CRT device 206, which is coupled by leads 210, 211, and
212 to the heart 100. Lead 210 is positioned in the right
ventricle, lead 211 positioned in the right atrium, and lead 212
positioned on the left ventricle.
[0052] In one embodiment, leads 210, 211, and 212 include
electrodes 220, 230, and 290 associated with the right ventricle,
right atrium, and left ventricle, respectively. Each electrode is
"associated" with the particular heart chamber by inserting it into
that heart chamber, or by inserting it into a portion of the
heart's vasculature that is close to that heart chamber, or by
epicardially placing the electrode outside that heart chamber, or
by any other technique of configuring and situating an electrode
for sensing signals and/or providing therapy with respect to that
heart chamber. Leads 210, 211, and 212 may alternatively also
include ring electrodes 225, 235, and 295. Each electrode may be
used for unipolar sensing of heart signals and/or unipolar delivery
of contraction-evoking stimulations in conjunction with one or more
other electrodes associated with the heart 100. Alternatively,
bipolar sensing and/or therapy may be delivered, for example,
between electrodes 220 and 225 of lead 210.
[0053] The CRT device 206 includes a sensing module 260, which is
coupled to one or more of the electrodes for sensing electrical
depolarizations corresponding to heart chamber activity. Such
electrical depolarizations of the heart tissue include atrial
depolarizations, referred to as P-waves, and ventricular
depolarizations, referred to as QRS complexes. The QRS complex is a
rapid sequence of several signal excursions away from a baseline in
sequentially switching polarity, with the largest excursion
referred to as an R-wave.
[0054] A peak detector 265 is coupled to the sensing module 260 for
detecting, for example, the P-wave peak from the right atrium 106,
obtained by bipolar sensing between electrodes 230 and 235, or by
any other sensing technique. Peak detector 265 may also sense the
R-wave peak at a plurality of different sites associated with the
left ventricle 112 or right ventricle 108, such as at each of the
electrodes 290 and 295. Sensing may be unipolar or bipolar. The
peak detector 265 may detect a variety of points associated with
the electrical activity of the heart 100.
[0055] A timer module 270 is coupled to the peak detector 265 for
timing one or more intervals between one or more events. For
example, the timer module 270 may be used to time an interval
between atrial and ventricular activity. As previously described,
this interval is known as the atrioventricular ("AV") interval
("AVI"). Because the interval is measured during sensing of the
atrium and ventricle, the interval is referred to herein as the
sensed atrioventricular interval ("AVI.sub.s"). The timer module
270 is also coupled to the therapy module 285, which provides the
time at which an atrial stimulation is delivered. Thus, timer
module 270 can also measure the interval between an atrial pacing
impulse and sensed ventricular activity ("AVI.sub.p").
[0056] A controller 280 is coupled to the timer module 270. The
controller 280 may process the one or more intervals measured by
the timer module 270. For example, the controller 280 may implement
one or more of the methods described in sections II-IV below. The
controller 280 may store one or more calculations in a memory
module 282 coupled to the controller 280.
[0057] A therapy module 285 is coupled to the controller 280. The
controller 280 controls the therapy module 285, and the therapy
module 285 is configured to deliver electrical impulses to the
heart 100 by leads 210, 211, and/or 212. The electrical impulses
may be used to stimulate activity (e.g., contraction) in one or
more chambers of the heart.
[0058] The CRM system 205 also includes a telemetry transceiver
275, which is communicatively coupled to an external programmer
277. The external programmer 277 may remotely communicate with the
telemetry transceiver 275 to, for example, extract data from or
reprogram the CRM system 205. In the example embodiments of the
present invention, the external programmer 277 is used to control
the mode and pacing of the CRM system 205.
[0059] The CRT device 206 may operate in a variety of modes. In a
first mode, VDD, the atrium 106 is sensed and one or both of the
ventricles 108 and 112 are paced. In a second mode, DDD, both the
atrium 106 and one or both of the ventricles 108 and 112 are paced.
A switch between VDD and DDD pacing is referred to as a mode
switch.
[0060] As described by one or more of the methods below, this
invention relates to methods to calculate optimized sensed and/or
paced AV delays at a plurality of rates. In addition, methods are
provided to allow for switching to different modes (e.g., between
atrial sensing and pacing) at different paced and sensed rates.
II. Optimization of Paced AV Delay for a Plurality of Atrial Pacing
Rates
[0061] In accordance with an example embodiment of the invention,
the paced atrioventricular delay ("AVD.sub.p") for a plurality of
pacing rates may be optimized when a CRT device is operating in a
paced atrial mode (e.g., DDD mode) using one or more of the methods
described below.
[0062] For example, one example method for calculating a plurality
of AVD.sub.p at a plurality of pacing rates is shown in FIG. 9. In
operation 510, a variable N is set equal to zero. As described
below, the variable N is used to increment the pacing rate. In
operation 520, the atrium is paced at a rate that is incremented
according to Equation 5.
Pacing Rate=X+KN (5)
The variable X is the resting heart rate or lowest desired heart
rate of the individual. K is a constant used to control the steps
taken between adjacent AVI.sub.p readings. For example, in one
embodiment, the constant K is set at 5, so that the pacing rate is
incremented by 5 beats for each measured AVI.sub.p. Other constants
may also be used. For example, K can be set equal to 1 if it is
desirable to measure the AVI.sub.p for each pacing rate or may be
increased to greater than 5 if less readings are desired.
[0063] With N set equal to 1 for the first loop of the method, the
heart is paced at a rate of X+K. Next, in operation 530, the
AVI.sub.p for the given pacing rate ("AVI.sub.Np") is measured.
Next, in operation 540, the AVD.sub.p for the given pacing rate
("AVD.sub.Np") is calculated. The AVD.sub.Np may be calculated
using, for example, an equation similar to Equation 4 described
above.
[0064] Once the AVD.sub.Np is calculated, the AVD.sub.Np and
associated pacing rate are stored in CRT device memory in operation
550. Then, in operation 560, the current pacing rate is compared to
a maximum pacing rate. This maximum pacing rate may be set to any
desired value, such as, for example, 180 beats/minute. If the
current pacing rate meets or exceeds the maximum rate, the
measurements are complete. If the maximum rate has not been
reached, in operation 570 the variable N is incremented and control
is passed back to operation 520 for a second loop of the
method.
[0065] During the second loop of the method, the pacing rate is
calculated according to Equation 5. A new AVI.sub.Np at the new
pacing rate is measured in operation 530, and a new AVD.sub.Np is
calculated in operation 540. The AVD.sub.Np and associated pacing
rate are also stored in memory in operation 550. The method is
continued until the maximum pacing rate is reached.
[0066] The AVD.sub.Np for each pacing rate that is stored in memory
of the CRT device may be assembled in a lookup table similar to
Table 1 shown below.
TABLE-US-00001 TABLE 1 Pacing Rate Optimized AVD.sub.p X + KN
AVD.sub.Np X + K(N + 1) AVD.sub.(N+1)p X + K(N + 2) AVD.sub.(N+2)p
X + K(N + 3) AVD.sub.(N+3)p X + K(N + 4) AVD.sub.(N+4)p X + K(N +
5) AVD.sub.(N+5)p
[0067] A CRT device may utilize a table such as Table 1 to look up
an optimal AVD.sub.p depending on the current atrial pacing rate.
As the CRT device pacing rate changes, the CRT device can lookup
the appropriate AVD.sub.p, thereby maintaining an optimal AVD.sub.p
as the pacing rate changes.
III. Optimization of Sensed AV Delay for a Plurality of Sensed
Rates
[0068] In accordance with other embodiments of the invention, the
AVD.sub.s can be optimized for a plurality of sensed heart rates
when a CRT device is operating in a sensed atrial mode (e.g., VDD
mode). This may be advantageous, for example, for patients
exhibiting normal sinus node function but requiring CRT.
[0069] For example, a method is illustrated in FIG. 10A for
calculating a plurality of different AVD.sub.s at a plurality of
sensed heart rates. In operation 810, the current sensed atrial
rate is measured. Next, in operation 820, if the current sensed
atrial rate has not exceeded the threshold, control is passed back
to operation 810. If the current sensed atrial rate has exceed the
threshold, control is passed to operation 830, where it is
determined whether or not the AVD.sub.Ns for the current sensed
atrial rate X.sub.N has been previously calculated or is
expired.
[0070] If the AVD.sub.Ns associated with the current sensed atrial
rate X.sub.N has not been previously calculated, control is passed
to operation 840, and the AVI.sub.Ns at the current sensed rate
X.sub.1 is measured. Next, in operation 850, the AVD.sub.Ns for the
particular sensed rate is estimated (using, for example, Equation 1
above) and stored, for example, in a table such as Table 2
below.
TABLE-US-00002 TABLE 2 Sensed rate Optimized AVD.sub.s X.sub.1
AVD.sub.1s X.sub.2 AVD.sub.2s X.sub.3 AVD.sub.3s X.sub.4 AVD.sub.4s
X.sub.5 AVD.sub.5s X.sub.6 AVD.sub.6s
In addition, if the AVD.sub.Ns associated with the current sensed
atrial rate X.sub.N has been previously calculated but has expired,
control is passed to operation 850, where the AVD.sub.Ns is
recalculated and stored in Table 2. The AVD.sub.Ns can be set to
expire at a certain interval after calculation such as, for
example, one week, one month, two months, etc., so that if the
sensed atrial rate is reached after expiration of the interval, the
AVD.sub.Ns can be recalculated. Control is then passed back to
operation 810.
[0071] If it is determined in operation 830 that the current sensed
atrial rate X.sub.N has been previously calculated and has not
expired, control is passed back to operation 810 to continue
measuring the current sensed atrial rate.
[0072] In this manner, the AVD.sub.Ns can be populated in Table 2
as each sensed atrial rate is reached as the patient's heart rate
intrinsically fluctuates. Therefore, the values for the AVD.sub.Ns
are advantageously populated "on the fly." In addition, the values
for the AVD.sub.Ns can be recalculated at set intervals to account
for changes in the patient's condition over time.
[0073] Another example method for estimating a plurality of
AVD.sub.s at a plurality of atrial pacing rates is shown in FIG.
10B. In operation 605, the AVI.sub.s is measured at a first sensed
rate, typically a resting heart rate. Then, in operation 610 the
AVD.sub.s is calculated using a known method described above and
stored in memory in operation 612. Next, in operation 615, the
heart is paced at a rate X slightly higher than the initial sensed
rate. In operation 620, the AVI.sub.p is measured, and an offset is
calculated in operation 625 using AVI.sub.p and AVI.sub.s. See
Equation 2 above.
[0074] Next, in operation 635 the variable N is set equal to 1, and
the atrium is paced at a rate calculated in operation 640 according
to Equation 5. Then, in operation 645, the AVI.sub.Np is measured
for the paced rate, and AVD.sub.Np is calculated in operation 647
using a known method as describe above. Next, an AVI.sub.N, is
estimated in operation 650 using Equation 6, a modified form of
Equation 2.
AVI.sub.Ns=AVI.sub.Np-offset (6)
[0075] Then, in operation 655, an AVD.sub.Ns based on the
AVI.sub.Ns can be calculated using, for example, one or more of the
methods described above. The AVD.sub.Ns as well as AVD.sub.Np and
associated rate are stored in operation 657. In operation 660, the
CRT device determines whether a maximum pacing rate has been
reached. If the maximum rate has been reached, the measurements are
complete and the atrial test pacing is ceased. If the maximum rate
has not been reached, the variable N is incremented and control is
passed back to operation 640 for a new set of measurements and
calculation of a new AVD.sub.Ns (and ADV.sub.Np) at a higher pacing
rate.
[0076] Once all measurements are completed, the CRT device 206 may
create a table, such as example Table 3 illustrated below,
including the AVD.sub.Ns and AVD.sub.Np for each pacing rate. A CRT
device may utilize such a table to look up an optimal AVD.sub.s or
AVD.sub.p depending on the sensed/paced atrial rate. As the atrial
sensed or paced rate changes, the CRT device 206 can lookup the
appropriate AVD.sub.s or ADV.sub.p, thereby maintaining an optimal
AVD.sub.s or AVD.sub.p as the sensed or paced rate changes.
TABLE-US-00003 TABLE 3 Pacing Rate Optimized AVD.sub.s Optimized
AVD.sub.p X + KN AVD.sub.Ns AVD.sub.Np X + K(N + 1) AVD.sub.(N+1)s
AVD.sub.(N+1)p X + K(N + 2) AVD.sub.(N+2)s AVD.sub.(N+2)p X + K(N +
3) AVD.sub.(N+3)s AVD.sub.(N+3)p X + K(N + 4) AVD.sub.(N+4)s
AVD.sub.(N+4)p X + K(N + 5) AVD.sub.(N+5)s AVD.sub.(N+5)p
IV. Optimization of Sensed AV Delay During Mode Switch Between
Atrial Sensing and Pacing
[0077] Knowing both the AVD.sub.s and AVD.sub.p for a particular
patient can be important because a CRT device may undergo a mode
switch during use. A mode switch can include a switch from atrial
pacing to atrial sensing such as, for example, when a patient
changes status from resting to exercising. During such a mode
switch from pacing to sensing (or vice versa), the CRT device
should switch from the optimized AVD.sub.p to the optimized
AVD.sub.s of the CRT device, thereby continuing to maintain an
optimized AVD.
[0078] For example, an operation flow for an example CRT device is
shown in FIG. 11. In operation 410, CRT is applied to a patient. In
operation 420, the CRT device determines if a mode switch has
occurred. The mode switch may be from atrial sensing to pacing, or
atrial pacing to sensing. If a mode switch has occurred, control is
passed to operation 430, wherein the device determines the current
mode in which the CRT device is operating. If the CRT device is now
operating in atrial sensing mode, control is passed to operation
450 and the optimized AVD.sub.s is selected. Conversely, if the CRT
device is now operating in atrial pacing mode, control is passed to
operation 460 and the optimized AVD.sub.p is selected. In this
manner, AVD may be optimized before and after a mode switch.
[0079] For example, a flow diagram shown in FIG. 12 illustrates how
a CRT device may utilize lookup tables including a plurality of
AVD.sub.Np and AVD.sub.Ns. In operation 710, an appropriate AVD,
based on a current pacing or sensing rate, is selected. An
appropriate AVD is selected, for example, by looking up the AVD in
either a pacing lookup table or a sensing lookup table stored on
the CRT device. If the CRT is functioning in sensing mode, the
current sensed rate is used to select an appropriate AVD.sub.s from
the sensing lookup table. Alternatively, if the CRT device is
functioning in pacing mode, the current pacing rate is used to
select an appropriate AVD.sub.p from the pacing lookup table.
[0080] Next, in operation 720, CRT is applied. In operation 730,
the CRT device determines whether there has been a mode switch,
either from sensing to pacing or from pacing to sensing. If a mode
switch has occurred, control is passed to 740, wherein the current
mode is determined. If the current mode is sensing, control is
passed to operation 760, in which an appropriate AVD.sub.s from the
sensing lookup table for the current pacing rate is selected. If
the current mode is pacing, control is passed to operation 765, in
which an appropriate AVD.sub.p from the pacing lookup table for the
current pacing rate is selected. After selecting an appropriate
AVD.sub.s or AVD.sub.p, control is passed back to operation 720 and
CRT continues.
[0081] If, in operation 730, the CRT device determines that a mode
switch has not occurred, control is passed to operation 735, in
which the CRT device determines if the current pacing rate has
changed. If the pacing rate has changed, control is passed to
operation 710, in which a new AVD is looked up in either the
sensing or pacing lookup table. If, in operation 735, the pacing
rate has not changed, control is passed back to operation 720 and
CRT continues.
V. Alternative Embodiments
[0082] The above systems and methods can be modified without
departing from the inventive concepts disclosed herein. For
example, instead of calculating a plurality of AVD.sub.s at
different pacing rates as described in section III above, it may
only be necessary to calculate two AVD.sub.s, one at a low pacing
rate and one at a high pacing rate. Using these two AVD.sub.s, it
may be possible to interpolate the remaining values, assuming a
relationship such as a linear relationship between AVD.sub.s for
different sensed rates. In addition, other methods besides those
illustrated above can be used to calculate an optimal AVD.sub.s and
AVD.sub.p.
[0083] The logical operations for calculating the optimized
AVD.sub.s may be performed by a device other than an implanted CRT
device 206. For example, an external device programmer,
communicating via telemetry, may be used. Furthermore, the logical
operations may be implemented (1) as a sequence of computer
implemented steps running on a computer system, and/or (2) as
interconnected machine modules.
[0084] This implementation is a matter of choice dependent on the
performance requirements of the device 206 or device programmer
implementing the invention. Accordingly, the logical operations
making up the embodiments of the invention described herein are
referred to as operations, steps, or modules. It will be recognized
by one of ordinary skill in the art that the operations, steps, and
modules may be implemented in software, in firmware, in special
purpose digital logic, analog circuits, and any combination thereof
without deviating from the spirit and scope of the present
invention as recited within the claims attached hereto.
[0085] While the invention has been particularly shown and
described with reference to preferred embodiments thereof, it will
be understood by those skilled in the art that various other
changes in the form and details may be made therein without
departing from the spirit and scope of the invention.
* * * * *