U.S. patent application number 10/756897 was filed with the patent office on 2004-11-18 for implantable defibrillators with programmable cross-chamber blanking.
This patent application is currently assigned to Cardiac Pacemakers, Inc.. Invention is credited to Birkholz, Doug M., Gilkerson, James O., Perschbacher, David L..
Application Number | 20040230232 10/756897 |
Document ID | / |
Family ID | 23490575 |
Filed Date | 2004-11-18 |
United States Patent
Application |
20040230232 |
Kind Code |
A1 |
Gilkerson, James O. ; et
al. |
November 18, 2004 |
Implantable defibrillators with programmable cross-chamber
blanking
Abstract
Miniature defibrillators and cardioverters detect abnormal heart
rhythms and automatically apply electrical therapy to restore
normal heart function. Therapy decisions are typically based on the
time between successive beats of various chambers of the heart,
such as the left atrium and left ventricle. To prevent confusing a
left ventricle beat for a left atrium beat, some devices use
cross-chamber blanking, a technique which disables sensing of
atrial beats for a certain time period after sensing.
Conventionally, these devices lack any mechanism for adjusting
length of this period. Accordingly, the inventor devised a
implantable device including a mechanism for adjusting this time
period. This mechanism ultimately allows tailoring of the
cross-chamber blanking period to fit the needs of individual
patients.
Inventors: |
Gilkerson, James O.;
(Stillwater, MN) ; Birkholz, Doug M.; (Shoreview,
MN) ; Perschbacher, David L.; (Coon Rapids,
MN) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Cardiac Pacemakers, Inc.
|
Family ID: |
23490575 |
Appl. No.: |
10/756897 |
Filed: |
January 14, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10756897 |
Jan 14, 2004 |
|
|
|
09981326 |
Oct 16, 2001 |
|
|
|
6687539 |
|
|
|
|
09981326 |
Oct 16, 2001 |
|
|
|
09377803 |
Aug 20, 1999 |
|
|
|
6304778 |
|
|
|
|
Current U.S.
Class: |
607/5 |
Current CPC
Class: |
A61N 1/3956
20130101 |
Class at
Publication: |
607/005 |
International
Class: |
A61N 001/39 |
Claims
1. An implantable dual-chamber defibrillation or cardioversion
device, comprising: at least first and second input leads for
sensing atrial and ventricular electrical signals from a heart; a
therapy circuit for delivering electrical energy through one or
more of the leads; and a monitoring circuit for monitoring the
electrical signals through one or more of the leads, the monitoring
circuit comprising: a programmable memory device for storing one or
more cross-chamber blanking settings; and circuitry for blanking an
effect of atrial electrical signals in the monitoring circuitry for
a period of time based on at least one of the cross-chamber
blanking settings.
2. A dual-chamber defibrillation or cardioversion system
comprising: a dual-chamber defibrillator or cardioverter including
first and second leads for sensing signals from respective first
and second chambers of a heart and a monitoring circuit for
monitoring signals sensed at the first and second leads, the
monitoring circuit having: preset time period based on at least one
of the settings; and means for changing one or more of the
cross-chamber blanking settings after implantation of the
defibrillator or cardioverter.
3-5. (Canceled)
6. The device of claim 1, wherein the circuitry for blanking
includes means for computing a noise window width based on a
refractory period and one of the cross-chamber blanking
settings.
7. The system of claim 2, wherein the cross-chamber blanking module
includes means for computing a noise window width based on at least
the one of the cross-chamber blanking settings.
8. An implantable dual-chamber cardioversion or defibrillation
device, comprising: first and second leads for sensing signals from
respective first and second chambers of a heart; a monitoring
module for monitoring signals sensed at the first and second leads,
the monitoring means including: a memory module for storing one or
more cross-chamber-blanking settings; and cross-chamber-blanking
module responsive to at least one of the settings for disabling
sensing signals at the first or second lead or for ignoring signals
at the first or second lead for a time period based on at least one
of the stored cross-chamber blanking settings; means, coupled to
the memory module, for wirelessly receiving at least one
cross-chamber blanking settings after implantation of the device
and for programming the memory module based on the one received
cross-chamber blanking setting; and a therapy module, responsive to
the monitoring module, for delivering a therapeutic agent to the
heart.
9. The device of claim 7, wherein the therapeutic agent is a
non-electrical agent.
10. The device of claim 7, wherein the cross-chamber-blanking
module comprises means for computing a noise window duration based
at least on the one cross-chamber blanking setting.
Description
TECHNICAL FIELD
[0001] The present invention concerns implantable defibrillators
and cardioverters and methods for ensuring accurate interval
measurements in these devices.
BACKGROUND OF THE INVENTION
[0002] Since the early 1980s, thousands of patients prone to
irregular and sometimes life threatening heart rhythms have had
miniature defibrillators and cardioverters implanted in their
bodies. These devices detect onset of abnormal heart rhythms and
automatically apply corrective electrical therapy, specifically one
or more bursts of electric current, to hearts. When the bursts of
electric current are properly sized and timed, they restore normal
heart function without human intervention, sparing patients
considerable discomfort and often saving their lives.
[0003] The typical defibrillator or cardioverter includes a set of
electrical leads, which extend from a sealed housing through the
veinous system into the inner walls of a heart after implantation.
Within the housing are a battery for supplying power, a capacitor
for delivering bursts of electric current through the leads to the
heart, and monitoring circuitry for monitoring the heart and
determining not only when and where to apply the current bursts but
also their number and magnitude. The monitoring circuitry generally
includes a microprocessor and a memory that stores instructions
directing the microprocessor to interpret electrical signals that
naturally occur in the heart as normal or abnormal rhythms. For
abnormal rhythms, the instructions, or more generally
signal-processing algorithm, tell the processor what, if any,
electrical therapy should be given to restore normal heart
function.
[0004] In general, these algorithms use the time intervals between
successive heart beats, or cardiac events, as key determinants of
therapy decisions. Thus, to ensure the validity of therapy
decisions, it is very important to ensure accuracy of these
intervals.
[0005] Determining these intervals can be especially problematic in
dual-chamber defibrillation and cardioversion devices, which
monitor the beats of two chambers of the heart, such as the left
ventricle and the left atrium. In these devices, there is a
significant risk of mistaking a ventricle beat for an atrial beat,
and therefore counting too many atrial beats and miscalculating
some atrial intervals (the time between atrial beats). Because of
this risk, many dual-chamber devices use a technique, known as
cross-chamber blanking, to ensure accuracy of atrial interval
measurements.
[0006] Cross-chamber blanking entails using a blanking period to
prevent sensing atrial beats for a certain time period after the
last ventricular beat. In other words, atrial sensing is
temporarily disabled after each ventricular beat to prevent
mistaking the ventricular beat for an atrial beat. In conventional
dual-chamber devices, the length, or duration, of the blanking
period is fixed during manufacture and cannot be tailored to fit
the unique needs of some patients. Accordingly, the inventors
recognized a need for dual-chamber defibrillation and cardioversion
devices that have programmable cross-chamber blanking periods.
SUMMARY OF THE INVENTION
[0007] To address this and other needs, the inventor devised a
dual-chamber implantable defibrillation and/or cardioversion device
which includes a memory storing one or more programmable or
reprogrammable settings for use as a cross-chamber blanking period.
An exemplary embodiment applies one of the settings to disable
atrial sensing for a period of time based on the programmed
setting. Ultimately, various embodiments of the invention
facilitate tailoring defibrillation and/or cardioversion devices to
individual patients.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a block diagram of an exemplary medical device
system 100 incorporating teachings of the present invention.
[0009] FIG. 2 is a flow chart illustrating an exemplary method
incorporating teachings of the present invention.
[0010] FIG. 3 is an exemplary timing diagram illustrating operation
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] The following detailed description, which references and
incorporates FIGS. 1-3, describes and illustrates one or more
specific embodiments of the invention. These embodiments, offered
not to limit but only to exemplify and teach the invention, are
shown and described in sufficient detail to enable those skilled in
the art to practice the invention. Thus, where appropriate to avoid
obscuring the invention, the description may omit certain
information known to those of skill in the art.
[0012] FIG. 1 shows an exemplary medical device system 100 which
includes a device programmer 110 and an implantable dual-chamber
defibrillation and/or cardioversion device 120 in accord with
teachings of the present invention. Device programmer 110, which
generally communicates programming information, such as one or more
cross-chamber blanking settings, to defibrillator 120, includes a
user interface 112, microcontroller or processor 114, a memory 116,
and a wireless transceiver 118.
[0013] User interface 112, which includes a keyboard and
graphical-user interface (not shown) generated by processor 114,
facilitates selection of one or more cross-chamber settings or
insertion of one or more manual settings, during a refractory
programming mode. Memory 116 stores, among other things, a number
of cross-chamber blanking settings 116a, for example a set of times
ranging from 30-200 milliseconds in 10-millisecond increments or a
set of temporal indices which can be used to determine duration of
a blanking period. Settings 116a are displayed for user selection
by user interface 112 during the programming mode.
[0014] In the exemplary embodiment, determination of appropriate
blanking period settings or times follows an iterative procedure of
visually analyzing electrogram data to determine whether a
particular cross-chamber blanking period is either too long or too
short, programming a new blanking period, and then visually
analyzing updated electrogram data. The selected or manually
inserted settings can then be communicated alone or in combination
with other programmable parameters into implantable device 120.
[0015] Implantable dual-chamber device 120 includes a wireless
transceiver 130 monitoring system 140, a lead system 150, a therapy
system 160, a power system 170, and an interconnective bus 180.
Wireless transceiver 130 communicates with wireless transceiver 118
of device programmer 110. Monitoring system 140 includes a
processor or microcontroller 142 and a memory 144. Memory 144
includes one or more software modules 144a which store one or more
computer instructions in accord with the present invention.
Additionally, memory 144 includes one or more parameter storage
portions 144b which store one or more programmed cross-chamber
blanking settings in accord with the present invention.
[0016] Some embodiments of the invention replace software modules
144a with one or more hardware or firmware modules. In the
exemplary embodiment, processor 142 is a ZiLOG.TM. Z80
microprocessor (with a math coprocessor). However, the invention is
not limited to any particular microprocessor, microcontroller, or
memory.
[0017] Lead system 150, in the exemplary embodiment, includes one
or more electrically conductive leads--for example, atrial,
ventricular, or defibrillation leads--suitable for insertion into a
heart. One or more of these are suitable for sensing electrical
signals from a portion of the heart and one or more are suitable
for transmitting therapeutic doses of electrical energy. Lead
system 120 also includes associated sensing and signal-conditioning
electronics, such as atrial or ventricular sense amplifiers and/or
analog-to-digital converters, as known or will be known in the
art.
[0018] In some embodiments, lead system 150 supports ventricular
epicardial rate sensing, atrial endocardial bipolar pacing and
sensing, ventricular endocardial bipolar pacing and sensing,
epicardial patches, and Endotak.RTM. Series and ancillary leads. In
some embodiments, lead system 120 also supports two or more pacing
regimens, including DDD pacing. Also, some embodiments use a
housing for device 100 as an optional defibrillation electrode. The
invention, however, is not limited in terms of lead or electrode
types, lead or electrode configurations, sensing electronics, or
signal-conditioning electronics.
[0019] Therapy system 160 includes one or more capacitors and other
circuitry (not shown) for delivering or transmitting electrical
energy in measured doses through lead system 150 to a heart or
other living tissue (not shown). In the exemplary embodiment,
therapy system 160 includes aluminum electrolytic or polymer-based
capacitors. However, other embodiments use one or more other
devices for administering non-electrical therapeutic agents, such
as pharmaceuticals, to a heart. Thus, the invention is not limited
to any particular type of therapy system.
[0020] In general operation, lead system 150 senses atrial or
ventricular electrical activity and provides data representative of
this activity to monitoring system 140. Monitoring system 140,
specifically processor 142, processes this data according to
instructions of software module 144a of memory 144. If appropriate,
processor 142 then directs or causes therapy system 160 to deliver
one or more measured doses of electrical energy or other
therapeutic agents through lead system 150 to a heart.
[0021] More precisely, FIG. 2 shows a flow chart 200, illustrating
an exemplary method at least partly embodied within software
modules 144a and executed by processor 142. Flow chart 200 includes
blocks 202-224, which are executed serially in the exemplary
embodiment. However, other embodiments of the invention may execute
two or more blocks in parallel using multiple processors or a
single processor organized as two or more virtual machines or
subprocessors. Moreover, still other embodiments implement the
blocks as two or more specific interconnected hardware modules with
related control and data signals communicated between and through
the modules. Thus, the exemplary process flow is instructive to
software, hardware, and firmware implementations.
[0022] In process block 202, device 120 is programmed using device
programmer 110. In the exemplary embodiment, this entails wireless
transceiver 130 receiving one or more cross-chamber blanking
settings via wireless transceiver 118 of device programmer 110. The
one or more settings take any desired value or form, for example,
one or more time values ranging from 30-200 milliseconds or one or
more temporal indices which are used as a basis for determining
time values. In any event, upon receipt of the one or more
settings, processor 142 stores them in portion 144b of memory 144.
At completion of this and any other programming procedures related
to operational criteria for device 120, execution of the exemplary
method proceeds to block 220.
[0023] In block 220, which assumes normal post-programming
operation, processor 142 retrieves one or more of the programmed
cross-chamber blanking settings from portion 144b of memory 144. In
the exemplary embodiment, this entails retrieving one time value,
for example, 45, 65, or 85 milliseconds, for use as the
cross-chamber blanking period and then computing a corresponding
noise window based on the difference between a preset refractory
period value (also stored in memory portion 144b), such as 86
milliseconds, and the retrieved cross-chamber blanking period. In
other words, the exemplary embodiment implements a refractory
period having two parts, the cross-chamber blanking part and the
noise window part, with the duration of the noise window contingent
on the cross-chamber blanking period. However, other embodiments
implement refractory periods with more or less than two parts
and/or without noise windows.
[0024] After retrieving the cross-chamber blanking setting,
processor 146 registers a ventricular event sensed through lead
system 150, as indicated in block 222. In the exemplary embodiment,
this entails recording a marker in memory 144 along with
appropriate timing indicia, before proceeding to block 224. The
marker can represent either a sensed ventricular signal or a
ventricular pacing signal.
[0025] In block 224, processor 142 invokes cross-chamber blanking
to prevent sensing of further atrial events via lead system 150 for
the duration of the cross-chamber blanking period. In the exemplary
embodiment, this entails electronically disabling an appropriate
portion of lead system 150 for the duration of the cross-chamber
blanking period. However, other embodiments ignore or discard data
from the appropriate portion of lead system 150 for the duration of
the blanking period. After termination of the blanking period,
sensing resumes.
[0026] FIG. 3 shows an exemplary timing diagram 300 which
illustrates function of the cross-chamber blanking interval.
Specifically, diagram 300 includes a horizontal time axis 302, a
ventricular event marker 304, and a refractory period 306 having a
programmable cross-chamber-blanking portion 306a and noise-window
portion 306b. Ventricular event marker 304 represents a ventricular
event sensed at block 224 in FIG. 2. Refractory period 306
represents the result of retrieving a programmed
cross-chamber-blanking setting from memory portion 144b, which
defines where blanking period 306a ends and noise window 306b
begins. This point is shown as broken line segment 306c in the
Figure. Atrial sensing is blanked during blanking period 306a.
Thus, apparent atrial events such as 308 are either not sensed
because of atrial sensing electronics are disabled or are ignored.
Events occurring within noise window 306b are assumed to be noise
and are thus similarly ignored.
Conclusion
[0027] In furtherance of the art, the inventors have presented an
implantable dual-chamber defibrillator and/or cardioverter which
includes programmable cross-chamber blanking. Unlike conventional
dual-chamber devices, those in accord with the present invention
allow physicians or other medically trained personnel to tailor the
cross-chamber blanking period to fit the needs of individual
patients.
[0028] The embodiments described above are intended only to
illustrate and teach one or more ways of practicing or implementing
the present invention, not to restrict its breadth or scope. The
actual scope of the invention, which embraces all ways of
practicing or implementing the teachings of the invention, is
defined only by the following claims and their equivalents.
* * * * *