US 6,847,842 B1Grant

Method and apparatus for reducing early recurrence of atrial fibrillation with defibrillation shock therapy

Issue Date:2005-01-25

•12 Claims

•3 Drawing Sheets

Abstract

An apparatus and method for delivering electrical shock therapy in order to treat atrial tachyarrhythmias such as fibrillation in which atrial defibrillation pulses are delivered within a maximum pre-shock R—R synchronization interval. The method has been found to reduce the incidence of early recurrence of atrial fibrillation (ERAF).

Metadata

Assignee

Cardiac Pacemakers, Inc.

Inventors

Kristen Rodenhiser
Mark Schwartz

Application Information

Application Number:US 09/570,645

Filing Date:2000-05-15

Priority Date:2000-05-15

Art Unit:3762

Patent Drawings (3 sheets)

Description

Field of the Invention

[00002] This invention pertains to methods for treating atrial tachyarrhythmias. In particular, the invention relates to an apparatus and method for delivering shock therapy to terminate atrial fibrillation.

Background

[00003] Tachyarrhythmias are abnormal heart rhythms characterized by a rapid heart rate, typically expressed in units of beats per minute (bpm). They can occur in either chamber of the heart (i.e., ventricles or atria) or both. Examples of tachyarrhythmias include sinus tachycardia, ventricular tachycardia, ventricular fibrillation (VF), atrial tachycardia, and atrial fibrillation (AF). Tachycardia is characterized by a rapid rate, either due to an ectopic excitatory focus or abnormal excitation by normal pacemaker tissue. Fibrillation occurs when the chamber depolarizes in a chaotic fashion with abnormal depolarization waveforms as reflected by an EKG.

[00004] An electrical shock applied to a heart chamber (i.e., defibrillation or cardioversion) can be used to terminate most tachyarrhythmias by depolarizing excitable myocardium, which thereby prolongs refractoriness, interrupts reentrant circuits, and discharges excitatory foci. Implantable cardioverter/defibrillators (ICDs) provide this kind of therapy by delivering a shock pulse to the heart when fibrillation is detected by the device. An ICD is a computerized device containing a pulse generator that is usually implanted into the chest or abdominal wall. Electrodes connected by leads to the ICD are placed on the heart, or passed transvenously into the heart, to sense cardiac activity and to conduct the shock pulses from the pulse generator. ICDs can be designed to treat either atrial or ventricular tachyarrhythmias, or both, and also incorporate cardiac pacing functionality.

[00005] The most dangerous tachyarrythmias are ventricular tachycardia and ventricular fibrillation, and ICDs have most commonly been applied in the treatment of those conditions. ICDs are also capable, however, of detecting atrial fibrillation and delivering a shock pulse to the atria in order to terminate the arrhythmia. Although not immediately life-threatening, it is important to treat atrial fibrillation for several reasons. First, atrial fibrillation is associated with a loss of atrio-ventricular synchrony which can be hemodynamically compromising and cause such symptoms as dyspnea, fatigue, vertigo, and angina. Atrial fibrillation can also predispose to strokes resulting from emboli forming in the left atrium. Although drug therapy and/or in-hospital cardioversion are acceptable treatment modalities for atrial fibrillation, ICDs configured to treat AF offer a number of advantages to certain patients, including convenience and greater efficacy.

[00006] An ICD terminates atrial fibrillation by delivering a shock pulse to electrodes disposed in or near the atria. The resulting depolarization also spreads to the ventricles, however, and there is a risk that such an atrial shock pulse can actually induce ventricular fibrillation, a condition much worse than atrial fibrillation. This risk can be reduced by delaying the delivery of an atrial shock pulse until the intrinsic ventricular rhythm is below a specified maximum rate and then delivering the shock synchronously with a sensed ventricular depolarization.

[00007] Another problem associated with defibrillation shock therapy is early recurrence of atrial fibrillation or ERAF. ERAF is defined as the recurrence of atrial fibrillation within a few minutes after successful cardioversion with atrial shock therapy. Certain patients are more prone than others to experience ERAF, and these patients may experience difficulty with repeated atrial defibrillation therapy. Reducing the incidence of ERAF would improve the efficacy of atrial defibrillation and expand the population of patients for whom an ICD is an acceptable therapy option. It is this problem with which the present invention is primarily concerned.

Summary of the Invention

[00008] The present invention is a method and apparatus for delivering atrial defibrillation therapy in which an atrial shock pulse is delivered within a specified maximum time interval after a preceding sensed ventricular depolarization or ventricular pace (R wave). In one embodiment, an R—R interval, defined as the time elapsed between a previous R wave and a present R wave, is measured after each sensed R wave. The atrial defibrillation shock pulse is then delivered synchronously with an R wave that occurs within a specified time window with respect to the previous R wave as defined by specified minimum and maximum R—R interval values. In another embodiment, an atrial shock pulse is delivered at a specified time after the previous R wave unless inhibited by an intrinsic ventricular depolarization occurring before the specified time. The atrial defibrillation shock can also be delivered in synchrony with a ventricular pace delivered at a specified time after the previous R wave unless inhibited by an R wave occurring before that time.

[00009] In one embodiment, an R—R interval, defined as the time elapsed between a previous R wave and a present R wave, is measured after each sensed R wave. The atrial defibrillation shock pulse is then delivered synchronously with an R wave that occurs within a specified time window with respect to the previous R wave as defined by specified minimum and maximum R—R interval values. In another embodiment, an atrial shock pulse delivered at a specified time after the previous R wave unless inhibited by an intrinsic ventricular depolarization occurring before the specified time. The atrial defibrillation shock can also be delivered in synchrony with a ventricular pace delivered at a specified time after the previous R wave unless inhibited by an R wave occurring before that time.

Brief Description of the Drawings

[00010] FIGS. 1A and 1B are timing diagrams illustrating embodiments of the invention.

[00011] FIG. 2 is a system diagram of an implantable defibrillator.

Detailed Description of the Invention

[00012] The present invention is a method and apparatus for delivering atrial defibrillation shock therapy. As used herein, atrial defibrillation shock therapy should be taken to mean shock therapy for treating any atrial tachyarrhythmia, such as atrial flutter, as well as atrial fibrillation.

[00013] In order to avoid the possible induction of ventricular fibrillation, atrial defibrillation shocks are usually delivered synchronously with a sensed R wave and after a minimum pre-shock R—R interval. (The R—R interval is the time between the immediately preceding R wave and the presently sensed R wave, and an R wave may be regarded as either a spontaneously occurring depolarization or a ventricular pace.) This is done because the ventricle is especially vulnerable to induction of fibrillation by a depolarizing shock delivered at a time too near the end of the preceding ventricular contraction (i.e., close to the T wave on an EKG). Delivering the shock synchronously with a sensed R wave thus moves the shock away from the vulnerable period, but at a very rapid ventricular rhythm, the ventricular beats may be so close together that even synchronously delivered shocks may induce ventricular fibrillation. To prevent this, shocking can be delayed until the ventricular rhythm is slow enough to safely deliver the defibrillation pulse as determined by measuring the R—R interval. That is, a minimum limit value for the R—R interval is specified, and shocking is inhibited if the sensed R wave occurs after a shorter interval. Recent clinical data has shown, however, that the incidence of early recurrence of atrial fibrillation (ERAF) after atrial defibrillation is positively correlated with the length of the pre-shock R—R interval.

[00014] In accordance with the present invention, atrial defibrillation shocks are delivered within a specified maximum time interval after a preceding sensed ventricular depolarization or ventricular pace (R wave). In one embodiment, the atrial defibrillation shock is delivered in synchrony with a sensed R wave. An R—R interval, defined as the time elapsed between a previous R wave and a present R wave, is measured after each sensed R wave. In contradistinction to previous methods, however, a shockable R—R interval is specified with both minimum and maximum limit values. The atrial defibrillation shock pulse is thus delivered synchronously with an R wave that occurs within a time window with respect to the previous R wave as defined by specified minimum and maximum R—R interval values. FIG. 1A is a diagram showing a sequence of intrinsic ventricular depolarizations IVD occurring during an episode of atrial defibrillation. After the depolarization labeled IVD1, a time window TW as defined by a minimum R—R interval MIN and a maximum R—R interval MAX is shown. This time window is considered a shockable R—R interval, and exemplary minimum and maximum limit values are 500 and 800 milliseconds, respectively. Thus, an atrial defibrillation shock ADF can be delivered in synchrony with an R wave IVD2 occurring within the shockable interval and with a reduced risk of causing either ventricular fibrillation or ERAF.

[00015] In another embodiment, an atrial shock pulse is delivered at a specified time after the previous R wave unless inhibited by an intrinsic ventricular depolarization occurring before the specified time. FIG. 1B shows another exemplary sequence of intrinsic ventricular depolarizations IVD occurring during an episode of atrial defibrillation. After the depolarization labeled IVD1, a specified time T1 is defined in which an atrial defibrillation shock ADF is to be delivered. The time T1 would preferably fall somewhere within the shockable R—R interval as defined above even though the atrial shock is not delivered in synchrony with an R wave. Delivering the atrial shock pulse at the time T1 thus reduces the risk of ERAF as in the first embodiment. Induction of ventricular fibrillation is prevented by both specifying the time T1 to be above a minimum value considered safe to shock and inhibiting the atrial shock if an intrinsic R wave occurs prior to the time T1. The atrial defibrillation shock can also be delivered in synchrony with a ventricular pace delivered at the specified time T1 after the previous R wave unless inhibited by an R wave occurring before that time.

[00016] FIG. 2 is a system diagram of a microprocessor-based implantable cardioverter/defibrillator device for treating atrial tachyarrthmias that also incorporates a pacemaker functionality. In this embodiment, a microprocessor and associated circuitry make up the controller of the device, enabling it to output pacing or shock pulses in response to sensed events and lapsed time intervals. The microprocessor 10 communicates with a memory 12 via a bidirectional data bus. The memory 12 typically comprises a ROM or RAM for program storage and a RAM for data storage. The ICD has atrial sensing and pacing channels comprising electrode 34, lead 33, sensing amplifier 31, pulse generator 32, and an atrial channel interface 30 which communicates bidirectionally with a port of microprocessor 10. The ventricular sensing and pacing channels similarly comprise electrode 24, lead 23, sensing amplifier 21, pulse generator 22, and a ventricular channel interface 20. For each channel, the same lead and electrode are used for both sensing and pacing. The sensing channels are used to control pacing and for measuring heart rate in order to detect tachyarrythmias such as fibrillation. The ICD detects an atrial tachyarrhythmia, for example, by measuring the atrial rate as well as possibly performing other processing on data received from the atrial sensing channel. A shock pulse generator 50 is interfaced to the microprocessor for delivering shock pulses to the atrium via a pair of terminals 51a and 51b that are connected by defibrillation leads to shock electrodes placed in proximity to regions of the heart. The defibrillation leads have along their length electrically conductive coils that act as electrodes for defibrillation stimuli. A similar shock pulse generator 60 and shock electrodes 61a and 61b are provided to deliver ventricular fibrillation therapy in the event of an induced ventricular fibrillation from atrial shock pulses.

[00017] The device depicted in FIG. 2 can be configured to deliver atrial defibrillation therapy in accordance with the invention as described above by appropriate programming of the microprocessor. Thus, once an episode of atrial fibrillation is detected with the atrial sensing channel, the device prepares to deliver an atrial defibrillation shock. As described above, the ventricular rhythm can monitored by measuring the R—R interval associated with each sensed R wave. If a sensed R wave occurs at an R—R interval longer than a specified minimum limit value and shorter than a specified maximum limit value, the interval is considered shockable so that the sensed R wave is safe to shock on. An atrial defibrillation shock can then delivered immediately so as to be practically synchronous with the sensed R wave. Alternatively, the atrial shock pulse can be delivered at a specified time after the preceding sensed R wave, either synchronously with a ventricular pace or not, unless inhibited by a sensed intrinsic R wave occurring prior to the time specified for delivering the atrial shock.

[00018] In another embodiment of the invention, an atrial defibrillation shock pulse is preceded by ventricular pacing in order to decrease the intrinsic ventricular rhythm to a rate at which the atrial defibrillation shock pulse can be more safely delivered. After atrial fibrillation is detected, a sequence of one or more ventricular pacing pulses is delivered at a rate intended to be above the intrinsic ventricular rate. After the last pacing pulse in the sequence is delivered, a compensatory pause is produced before the next intrinsic ventricular beat. The atrial defibrillation shock pulse can then be delivered synchronously with that beat if the sensed R wave occurs within the shockable R—R interval as defined by specified minimum and maximum limit value. In the embodiment where the atrial defibrillation pulse is to be delivered at a specified time after the preceding R wave, either with or without an accompanying ventricular pace, the compensatory pause also delays the next R wave so that inhibition of the atrial shock is less likely to occur.

[00019] Although the invention has been described in conjunction with the foregoing specific embodiment, many alternatives, variations, and modifications will be apparent to those of ordinary skill in the art. Such alternatives, variations, and modifications are intended to fall within the scope of the following appended claims.

Claims

Certificate of Correction present

The claims shown below may not include correction changes. Use the corrected PDF for authoritative text.

1. A method for delivering atrial defibrillation therapy, comprising:

detecting an episode of atrial fibrillation;

sensing ventricular depolarizations (R waves);

delivering a first ventricular pacing pulse after a sensed R wave; and

delivering an atrial defibrillation shock without an accompanying second ventricular pacing pulse at a specified time after the first ventricular pacing pulse but inhibiting the atrial defibrillation shock if a second R wave subsequent to the first ventricular pacing pulse occurs before the specified time.

2. The method of claim 1 wherein the specified time for delivering the atrial defibrillation shock is less than 800 milliseconds.

3. The method of claim 1 wherein the specified time for delivering the atrial defibrillation shock is greater than 500 milliseconds and less than 800 milliseconds.

4. The method of claim 1 wherein the first ventricular pacing pulse is preceded by one or more additional ventricular pacing pulses delivered after the sensed R wave at a rate greater than the measured intrinsic rate.

5. The method of claim 1 wherein the specified time for delivering the atrial defibrillation shock is less than 800 milliseconds.

6. The method of claim 5 wherein the specified time for delivering the atrial defibrillation shock is greater than 500 milliseconds and less than 800 milliseconds.

7. The method of claim 1 wherein the first ventricular pacing pulse is delivered after the sensed R wave at a rate above an intrinsic ventricular rate.

8. An apparatus for delivering atrial defibrillation therapy to an atrium, comprising:

sensing channels for sensing atrial and ventricular depolarizations (R waves);

a ventricular pacing channel for delivering ventricular pacing pulses;

an atrial defibrillation pulse generator and electrodes disposed in proximity to the atrium; and

a controller for detecting atrial fibrillation and for controlling delivery of atrial defibrillation shocks and ventricular pacing pulses, wherein, upon detection of atrial fibrillation, the controller is configured to:

deliver a first ventricular pacing pulse after a sensed R wave; and

deliver an atrial defibrillation shock without an accompanying second ventricular pacing pulse at a specified time after the first ventricular pacing pulse but inhibit the atrial defibrillation shock if an R wave subsequent to the first ventricular pacing pulse occurs before the specified time.

9. The apparatus of claim 8 wherein the specified time for delivering the atrial defibrillation shock is less than 800 milliseconds.

10. The apparatus of claim 8 wherein the specified time for delivering the atrial defibrillation shock is greater than 500 milliseconds and less than 800 milliseconds.

11. The apparatus of claim 8 wherein the controller is configured to deliver the first ventricular pacing pulse preceded by one or more additional ventricular pacing pulses delivered after the sensed R wave at a rate greater than the measured intrinsic rate.

12. The apparatus of claim 8 wherein the first ventricular pacing pulse is delivered after the sensed R wave at a rate above an intrinsic ventricular rate.

Patent Citations (211)

Patent	Date	Inventor	Cited By
US3937226(A)	1976-02-01	Funke	Applicant
US4202340(A)	1980-05-01	Langer et al.	Applicant
USRE30387(E)	1980-08-01	Denniston, III et al.	Applicant
US4378020(A)	1983-03-01	Nappholz et al.	Applicant
US4407288(A)	1983-10-01	Langer et al.	Applicant
US4488561(A)	1984-12-01	Doring	Applicant
US4523593(A)	1985-06-01	Rueter	Applicant
US4548203(A)	1985-10-01	Tacker, Jr. et al.	Applicant
US4554922(A)	1985-11-01	Prystowsky et al.	Applicant
US4559946(A)	1985-12-01	Mower	Applicant
US4595009(A)	1986-06-01	Leinders	Applicant
US4637397(A)	1987-01-01	Jones et al.	Applicant
US4641656(A)	1987-02-01	Smits	Applicant
US4662382(A)	1987-05-01	Sluetz et al.	Applicant
US4665919(A)	1987-05-01	Mensink et al.	Applicant
US4693253(A)	1987-09-01	Adams	Applicant
US4708145(A)	1987-11-01	Tacker, Jr. et al.	Applicant
US4763646(A)	1988-08-01	Lekholm	Applicant
US4774952(A)	1988-10-01	Smits	Applicant
US4775950(A)	1988-10-01	Terada et al.	Applicant
US4787389(A)	1988-11-01	Tarjan	Applicant
US4788980(A)	1988-12-01	Mann et al.	Applicant
US4800883(A)	1989-01-01	Winstrom	Applicant
US4819643(A)	1989-04-01	Menken	Applicant
US4821723(A)	1989-04-01	Baker, Jr. et al.	Applicant
US4821724(A)	1989-04-01	Whigham et al.	Applicant
US4827932(A)	1989-05-01	Ideker et al.	Applicant
US4834100(A)	1989-05-01	Charms	Applicant
US4880004(A)	1989-11-01	Baker, Jr. et al.	Applicant
US4903700(A)	1990-02-01	Whigham et al.	Applicant
US4940054(A)	1990-07-01	Grevis et al.	Applicant
US4944300(A)	1990-07-01	Saksena	Applicant
US4949719(A)	1990-08-01	Pless et al.	Applicant
US4951667(A)	1990-08-01	Markowitz et al.	Applicant
US4967747(A)	1990-11-01	Carroll et al.	Applicant
US4972835(A)	1990-11-01	Carroll et al.	Applicant
US4984572(A)	1991-01-01	Cohen	Applicant
US4996984(A)	1991-03-01	Sweeney	Applicant
US5007422(A)	1991-04-01	Pless et al.	Applicant
US5018523(A)	1991-05-01	Bach, Jr. et al.	Applicant
US5042480(A)	1991-08-01	Hedin et al.	Applicant
US5048521(A)	1991-09-01	Pless et al.	Applicant
US5077667(A)	1991-12-01	Brown et al.	Applicant
US5085213(A)	1992-02-01	Cohen	Applicant
US5103819(A)	1992-04-01	Baker et al.	Applicant
US5111811(A)	1992-05-01	Smits	Applicant
US5111812(A)	1992-05-01	Swanson et al.	Applicant
US5117824(A)	1992-06-01	Keimel et al.	Applicant
US5154485(A)	1992-10-01	Fleishman	Applicant
US5161527(A)	1992-11-01	Nappholz et al.	Applicant
US5161528(A)	1992-11-01	Sweeney	Applicant
US5163428(A)	1992-11-01	Pless	Applicant
US5165403(A)	1992-11-01	Mehra	Applicant
US5178140(A)	1993-01-01	Ibrahim	Applicant
US5179945(A)	1993-01-01	Van Hofwegen et al.	Applicant
US5188105(A)	1993-02-01	Keimel	Applicant
US5193535(A)	1993-03-01	Bardy et al.	Applicant
US5193536(A)	1993-03-01	Mehra	Applicant
US5205283(A)	1993-04-01	Olson	Applicant
US5207219(A)	1993-05-01	Adams et al.	Examiner
US5265600(A)	1993-11-01	Adams et al.	Applicant
US5269300(A)	1993-12-01	Kelly et al.	Applicant
US5275621(A)	1994-01-01	Mehra	Applicant
US5277231(A)	1994-01-01	Dostalek	Applicant
US5282836(A)	1994-02-01	Kreyenhagen et al.	Applicant
US5282838(A)	1994-02-01	Hauser et al.	Applicant
US5285780(A)	1994-02-01	Tsuji et al.	Applicant
US5314448(A)	1994-05-01	Kroll et al.	Applicant
US5330508(A)	1994-07-01	Gunderson	Applicant
US5332400(A)	1994-07-01	Alferness	Examiner
US5339820(A)	1994-08-01	Henry et al.	Applicant
US5346506(A)	1994-09-01	Mower et al.	Applicant
US5350401(A)	1994-09-01	Levine	Applicant
US5354316(A)	1994-10-01	Keimel	Applicant
US5366485(A)	1994-11-01	Kroll et al.	Applicant
US5370124(A)	1994-12-01	Dissing et al.	Applicant
US5370667(A)	1994-12-01	Alt	Applicant
US5374282(A)	1994-12-01	Nichols et al.	Applicant
US5376103(A)	1994-12-01	Anderson et al.	Applicant
US5383907(A)	1995-01-01	Kroll	Applicant
US5395373(A)	1995-03-01	Ayers	Applicant
US5396902(A)	1995-03-01	Brennen et al.	Applicant
US5403355(A)	1995-04-01	Alt	Applicant
US5403356(A)	1995-04-01	Hill et al.	Applicant
US5411524(A)	1995-05-01	Rahul	Examiner
US5431682(A)	1995-07-01	Hedberg	Applicant
US5431685(A)	1995-07-01	Alt	Applicant
US5439006(A)	1995-08-01	Brennen et al.	Applicant
US5439483(A)	1995-08-01	Duong-Van	Applicant
US5441518(A)	1995-08-01	Adams et al.	Applicant
US5441521(A)	1995-08-01	Hedberg	Applicant
US5456706(A)	1995-10-01	Pless et al.	Applicant
US5458622(A)	1995-10-01	Alt	Applicant
US5464429(A)	1995-11-01	Hedberg et al.	Applicant
US5466245(A)	1995-11-01	Spinelli et al.	Applicant
US5476498(A)	1995-12-01	Ayers	Applicant
US5476499(A)	1995-12-01	Hirschberg	Applicant
US5480413(A)	1996-01-01	Greenhut et al.	Applicant
US5486198(A)	1996-01-01	Ayers et al.	Applicant
US5489293(A)	1996-02-01	Pless et al.	Applicant
US5500008(A)	1996-03-01	Fain	Applicant
US5507780(A)	1996-04-01	Finch	Applicant
US5522853(A)	1996-06-01	Kroll	Applicant
US5545182(A)	1996-08-01	Stotts et al.	Applicant
US5545204(A)	1996-08-01	Cammilli et al.	Applicant
US5549642(A)	1996-08-01	Min et al.	Applicant
US5554174(A)	1996-09-01	Causey, III	Applicant
US5560370(A)	1996-10-01	Verrier et al.	Applicant
US5562709(A)	1996-10-01	White	Applicant
US5584864(A)	1996-12-01	White	Applicant
US5591215(A)	1997-01-01	Greenhut et al.	Applicant
US5609613(A)	1997-03-01	Woodson et al.	Applicant
US5609621(A)	1997-03-01	Bonner	Applicant
US5617854(A)	1997-04-01	Munsif	Applicant
US5620468(A)	1997-04-01	Mongeon et al.	Applicant
US5620469(A)	1997-04-01	Kroll	Applicant
US5626136(A)	1997-05-01	Webster, Jr.	Applicant
US5628778(A)	1997-05-01	Kruse et al.	Applicant
US5662119(A)	1997-09-01	Brennen et al.	Applicant
US5662687(A)	1997-09-01	Hedberg et al.	Applicant
US5674250(A)	1997-10-01	de Coriolis et al.	Applicant
US5683431(A)	1997-11-01	Wang	Applicant
US5683445(A)	1997-11-01	Swoyer	Applicant
US5690686(A)	1997-11-01	Min et al.	Applicant
US5699014(A)	1997-12-01	Haefner et al.	Applicant
US5709215(A)	1998-01-01	Perttu et al.	Applicant
US5713924(A)	1998-02-01	Min et al.	Applicant
US5759202(A)	1998-06-01	Schroeppel	Applicant
US5772590(A)	1998-06-01	Webster, Jr.	Applicant
US5772693(A)	1998-06-01	Brownlee	Applicant
US5776164(A)	1998-07-01	Ripart	Examiner
US5778881(A)	1998-07-01	Sun et al.	Applicant
US5782239(A)	1998-07-01	Webster, Jr.	Applicant
US5782887(A)	1998-07-01	van Krieken et al.	Applicant
US5797967(A)	1998-08-01	KenKnight	Applicant
US5814081(A)	1998-09-01	Ayers et al.	Applicant
US5824031(A)	1998-10-01	Cookston et al.	Applicant
US5840079(A)	1998-11-01	Warman et al.	Applicant
US5843153(A)	1998-12-01	Johnston et al.	Applicant
US5849032(A)	1998-12-01	Van Venrooij	Applicant
US5853426(A)	1998-12-01	Shieh	Applicant
US5865838(A)	1999-02-01	Obel et al.	Applicant
US5868680(A)	1999-02-01	Steiner et al.	Applicant
US5873842(A)	1999-02-01	Brennen et al.	Applicant
US5893882(A)	1999-04-01	Peterson et al.	Applicant
US5902331(A)	1999-05-01	Bonner et al.	Applicant
US5922014(A)	1999-07-01	Warman et al.	Applicant
US5925073(A)	1999-07-01	Chastain et al.	Applicant
US5951471(A)	1999-09-01	de la Rama et al.	Applicant
US5955218(A)	1999-09-01	Crespi et al.	Applicant
US5964795(A)	1999-10-01	McVenes et al.	Applicant
US5968079(A)	1999-10-01	Warman et al.	Applicant
US5987354(A)	1999-11-01	Cooper et al.	Applicant
US5991657(A)	1999-11-01	Kim	Applicant
US5999850(A)	1999-12-01	Dawson et al.	Applicant
US5999854(A)	1999-12-01	Deno et al.	Applicant
US5999858(A)	1999-12-01	Sommer et al.	Applicant
US6006122(A)	1999-12-01	Smits	Applicant
US6006137(A)	1999-12-01	Williams	Applicant
US6021354(A)	2000-02-01	Warman et al.	Applicant
US6047210(A)	2000-04-01	Kim et al.	Examiner
US6055457(A)	2000-04-01	Bonner	Applicant
US6067471(A)	2000-05-01	Warren	Applicant
US6070104(A)	2000-05-01	Hine et al.	Applicant
US6076014(A)	2000-06-01	Alt	Applicant
US6081745(A)	2000-06-01	Mehra	Applicant
US6081746(A)	2000-06-01	Pendekanti et al.	Applicant
USRE36765(E)	2000-07-01	Mehra	Applicant
US6085116(A)	2000-07-01	Pendekanti et al.	Applicant
US6085119(A)	2000-07-01	Scheiner et al.	Applicant
US6091988(A)	2000-07-01	Warman et al.	Applicant
US6115628(A)	2000-09-01	Stadler et al.	Applicant
US6115630(A)	2000-09-01	Stadler et al.	Applicant
US6161037(A)	2000-12-01	Cohen	Applicant
US6246906(B1)	2001-06-01	Hsu et al.	Applicant
US6249699(B1)	2001-06-01	Kim	Applicant
US6256534(B1)	2001-07-01	Dahl	Applicant
US6272380(B1)	2001-08-01	Warman et al.	Applicant
US6275734(B1)	2001-08-01	McClure et al.	Applicant
US6280391(B1)	2001-08-01	Olson et al.	Applicant
US6430438(B1)	2002-08-01	Chen et al.	Applicant
US6430449(B1)	2002-08-01	Hsu et al.	Applicant
US6459932(B1)	2002-10-01	Mehra	Applicant
US6526317(B2)	2003-02-01	Hsu et al.	Applicant
US6556862(B2)	2003-04-01	Hsu et al.	Applicant
US6584350(B2)	2003-06-01	Kim et al.	Applicant
US6587720(B2)	2003-07-01	Hsu et al.	Applicant
US6721596(B1)	2004-04-01	Girouard et al.	Applicant
US20030004551(A1)	2003-01-01	Chen	Applicant
US20030199928(A1)	2003-10-01	Hsu et al.	Applicant
US20040015192(A1)	2004-01-01	Kim et al.	Applicant
EP347708	1989-12-01		Applicant
EP436517	1991-07-01		Applicant
EP467652	1992-01-01		Applicant
EP522693	1993-01-01		Applicant
EP550343	1993-07-01		Applicant
EP550344	1993-07-01		Applicant
EP588125	1993-09-01		Applicant
EP588124	1994-03-01		Applicant
EP594269	1994-04-01		Applicant
EP606688	1994-07-01		Applicant
EP770412	1997-05-01		Applicant
EP813886	1997-12-01		Applicant
FR2528708	1983-12-01		Applicant
WO-9302746	1993-02-01		Applicant
WO-9320888	1993-10-01		Applicant
WO-9528987	1995-11-01		Applicant
WO-9528988	1995-11-01		Applicant
WO-WO9701373	1997-01-01		Applicant
WO-9701373	1997-01-01		Applicant
WO-9848891	1998-11-01		Applicant

Non-Patent Literature (22)

Metrix Model 3020 Implantable Atrial Defibrillator, Physician's Manual, InControl. Inc., Redmond, WA,(1998),pp. 4-24-4-27.Applicant
“Blanking Circuit Diagram Illustrating a Circuit in the PRXII Defibrillator”, Cardiac Pacemakers, Inc., Reqt, Hybrid, Analog 530370 Rev 02,p. 32.Applicant
“Blanking Circuit Diagram Illustrating a Circuit in the VIGOR Pacemaker”, Sold by Cardiac Pacemakers Inc.,.Applicant
Allessie, M , et al., “Regional Control of Atrial Fibrillation by Rapid Pacing in Conscious Dogs”, Circulation, 84 (4), (Oct. 1991),pp. 1689-1697.Applicant
Ayers, Gregory M., et al., “Ventricular Proarrhythmic Effects of Ventricular Cycle Length and Shock Strength in a Sheep Model of Transvenous Atrial Defibrillation”, Circulation, 89 (1), (Jan. 1994),413-422.Applicant
Circulation, 85 (5), (May 1992),pp. 1865-1878.Applicant
Frazier, D.W., et al., “Stimulus-Induced Critical Point—Mechanism for Electrical Initiation of Reentry in Normal Canine Myocardium”, Journal of Clinical Investigation, 83, (Mar. 1989),pp. 1039-1052.Applicant
Greenhut, S. , et al., “Effectiveness of a Ventricular Rate Stabilization Algorithm During Atrial Fibrillation in Dogs”, Pace Abstract, Abstract No. 60,(1996), 1 p.Applicant
Hayes, D L., et al., “Pacemaker Timing Cycles”, In: Cardiac Pacing, Edited by Kenneth A. Ellenbogen, M.D., published by Blackwell Science,(1992),263-308.Applicant
Hsia, Peng W., et al., “Absolute Depolarization Vector Characteristics Associated with Successful Defibrillation: Evidence of a Vulnerable Period During Ventricular Fibrillation”, Circulation, 82 (4), Supplement III, Abstracts, Abstract No. 2933,(Oct. 1990),p. III-738.Applicant
Hsia, Peng W., et al., “Genesis of Slgmoidal Dose-Response Curve During Defibrillation by Random Shock: A Theoretical Model Based on Experimental Evidence for a Vulnerable Window During Ventricular Fibrillation”, Pace, 13, NASPE Young Investigator Awardee-1990,(Oct. 1990),pp. 1326-1342.Applicant
Hsia, Peng W., et al., “Improved Nonthoractomy Defibrillation Based on Ventricular Fibrillation Waveform Characteristics”, PACE, 18—NASPE Abstracts, Abstract No. 29,(Apr. 1995),p. 803.Applicant
Jones, Douglas L., et al., “Ventricular Fibrillation: The Importance of Being Coarse?”, Journal of Electrocardiology, 17 (4), (1984),pp. 393-399.Applicant
Kenknight, B H., et al., “Regional Capture of Fibrillating Ventricular Myocardium”, Circulation Research, 77 (4), (Oct. 1995),pp. 849-855.Applicant
Kuelz, Kathy W., et al., “Integration of Absolute Ventricular Fibrillation Voltage Correlates with Successful Defibrillation”, IEEE Transactions on Biomedical Engineering, 41 (8), (Aug. 1994), pp. 782-791.Applicant
Mower, Morton M., et al., “Synchronization of Low-Energy Pulses to Rapid Deflection Signals as a Possible Mechanism of Subthreshold Ventricular Defibrillation”, Abstracts of the 55th Scientific Sessions, Abstract No. 298,(1982),p. II-75.Applicant
Singer, Igor, et al., “The Automatic Implantable Cardioverter Defibrillator: T Wave Sensing in the Newest Generation”, PACE, 11, Part I, (Nov. 1988),pp. 1584-1591.Applicant
Tang, A S., et al., “Three-Dimensional Potential Gradient Fields Generated by Intracardiac Catheter and Cutaneous Patch Electrodes”, Circulation, 85 (5), (May 1992),pp. 1857-1864.Applicant
Thakor, N. V., et al., “Optimal QRS Detector”, Medical & Biological Engineering & Computing, 21, (May 1983),pp. 343-350.Applicant
Wharton, J M., et al., Cardiac Potential and Potential Gradient Fields Generated by Single, Combined, and Sequential Shocks During Ventricular.Applicant
Defibrillation, Circulation, 85 (4), (Apr. 1992),pp. 1510-1523.Applicant
Wittkampf, F.H.M., et al., “Rate Stabilization by Right Ventricular Pacing in Patients with Atrial Fibrillation”, Pace, vol. 9, Part II, (Nov.-Dec. 1986), 1147-1153.Applicant

Abstract