CA2031854A1 - Apparatus and method for antitachycardia pacing in dual chamber arrhythmia control system - Google Patents
Apparatus and method for antitachycardia pacing in dual chamber arrhythmia control systemInfo
- Publication number
- CA2031854A1 CA2031854A1 CA002031854A CA2031854A CA2031854A1 CA 2031854 A1 CA2031854 A1 CA 2031854A1 CA 002031854 A CA002031854 A CA 002031854A CA 2031854 A CA2031854 A CA 2031854A CA 2031854 A1 CA2031854 A1 CA 2031854A1
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- Canada
- Prior art keywords
- dual chamber
- pacing
- antitachycardia
- tachycardia
- interval
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
- A61N1/362—Heart stimulators
- A61N1/3621—Heart stimulators for treating or preventing abnormally high heart rate
- A61N1/3622—Heart stimulators for treating or preventing abnormally high heart rate comprising two or more electrodes co-operating with different heart regions
Abstract
ABSTRACT
Apparatus and method of antitachycardia pacing in a dual chamber pacing device including means for or steps of detecting the presence of a tachycardia, measuring the tachycardia cycle length, determining a VA interval value less than or equal to the tachycardia cycle length, determining an initial value of the AV delay interval, delivering pulses to the ventricle and to the atrium until the expiration of N VA intervals and N AV intervals thereby completing a first train of pulses, delivering a series of M trains of pulses similar to said first train of pulses, and varying the AV delay interval value from the initial value at least once prior to the completion of the series of M trains of pulses.
Monitoring of intrinsic QRS complexes between pulse trains is performed. If the tachyarrhythmia is deemed to be accelerating, one of cardioversion of defibrillation may be applied.
Apparatus and method of antitachycardia pacing in a dual chamber pacing device including means for or steps of detecting the presence of a tachycardia, measuring the tachycardia cycle length, determining a VA interval value less than or equal to the tachycardia cycle length, determining an initial value of the AV delay interval, delivering pulses to the ventricle and to the atrium until the expiration of N VA intervals and N AV intervals thereby completing a first train of pulses, delivering a series of M trains of pulses similar to said first train of pulses, and varying the AV delay interval value from the initial value at least once prior to the completion of the series of M trains of pulses.
Monitoring of intrinsic QRS complexes between pulse trains is performed. If the tachyarrhythmia is deemed to be accelerating, one of cardioversion of defibrillation may be applied.
Description
-1- 2031~
APPAR~TUS AND METHOD FOR ANTITACHYCARDIA
PACING IN DUAL CHAMBER ARRHYTHMIA CONTROL SYSTEM
TECHNICAL FIELD
This invention relates to implantable medi-cal devices which monitor the cardiac state of a pa-tient by sensing the patient's intrinsic rhythm, atri-al and ventricular tachycardia, atrial and ventricular fibrillation/flutter and which deliver therapy in the form of electrical energy to cardiac tissue in both chambers of the heart in an attempt to revert tachy-cardia and restore a normal sinus rhythm. More par-ticularly, the invention relates to an apparatus and method for antitachycardia pacing (ATP) in a dual chamber arrhythmia control system. Although the in-vention may be incorporated in an antitachycardia pacing de~ice alone, it is described herein as operat-ing in a combined implantable antitachycardia pacing, bradycardia pacing, defibrillating or cardioverting arrhythmia control system.
As used herein, the term tachycardia refers to any fast abnormal rhythm of the heart which may be amenable to treatment by electrical discharges and specifically includes sinus ~achycardia, supraventric-ular tachycardia (SVT), atrial tachycardia, (AT), atrial fibrillation and flutter (AF), ventricular tachycardia (VT), ventricular flutter and ventricular fibrillation (VF).
PRIOR ART
United States Patent No. 3,857,398 to Rubin describes a combined pacer/defibrillator. This device `!
either performs a bradycardia pacing or a defibrilla-tion function depending on the detection of a VT/VF.
If a VT/VF is detected, the device is switched to the .
- : . :' . .
: - , .- , . . . .
APPAR~TUS AND METHOD FOR ANTITACHYCARDIA
PACING IN DUAL CHAMBER ARRHYTHMIA CONTROL SYSTEM
TECHNICAL FIELD
This invention relates to implantable medi-cal devices which monitor the cardiac state of a pa-tient by sensing the patient's intrinsic rhythm, atri-al and ventricular tachycardia, atrial and ventricular fibrillation/flutter and which deliver therapy in the form of electrical energy to cardiac tissue in both chambers of the heart in an attempt to revert tachy-cardia and restore a normal sinus rhythm. More par-ticularly, the invention relates to an apparatus and method for antitachycardia pacing (ATP) in a dual chamber arrhythmia control system. Although the in-vention may be incorporated in an antitachycardia pacing de~ice alone, it is described herein as operat-ing in a combined implantable antitachycardia pacing, bradycardia pacing, defibrillating or cardioverting arrhythmia control system.
As used herein, the term tachycardia refers to any fast abnormal rhythm of the heart which may be amenable to treatment by electrical discharges and specifically includes sinus ~achycardia, supraventric-ular tachycardia (SVT), atrial tachycardia, (AT), atrial fibrillation and flutter (AF), ventricular tachycardia (VT), ventricular flutter and ventricular fibrillation (VF).
PRIOR ART
United States Patent No. 3,857,398 to Rubin describes a combined pacer/defibrillator. This device `!
either performs a bradycardia pacing or a defibrilla-tion function depending on the detection of a VT/VF.
If a VT/VF is detected, the device is switched to the .
- : . :' . .
: - , .- , . . . .
-2- 20318~
defibrillating mode. After a period of time to charge the capacitor, a defibrillation shock is delivered to the patient.
Improvements on this device were contained in a multiprogrammable, telemetric, implantable defi-brillator which is disclosed in copending Patent Ap-plication Serial No. 239,624 entitled "Reconfirmation Prior to Shock in Implantable Defibrillator". The device contains a bradycardia support system as well as a high energy shock system to revert ventricular tachycardias to normal sinus rhythm. On reconfirma-tion of the presence of a tachycardia, a shoc~ is delivered to the patient at a predetermined time or when the desired energy level is reached.
As cardioversion or defibrillation shocks can be very unpleasant to a patient, especially when delivered frequently, it became necessary therefore to provide a device which included antitachycardia pacing therapy along with bradycardia support pacing therapy and defibrillation or cardioversion therapy, so that the implanted device could automatically provide the necessary therapy from a range of therapies offered by the device. Hence a further development in the field of combined implantable devices is described in co-pending United States patent application No. 187,787, to Grevis and Gilli, filed April 29, 1988, and enti-tled "Apparatus and Method for Controlling Multiple Sensitivities in Arrhythmia Control Systems Including Post Therapy Pacing Delay", assigned to the assignee of the present invention. This device is a microcom-puter based arrhythmia control system which is pro-grammable by means of a telemetric link. The device provides single chamber bradycardia support pacing, antitachycardia pacing, and cardioversion or defibril-lation shocks for restoring normal sinus rhythm to a - . .
20318~4 patient.
Additionally, various specific developments have been made in the field of tachycardia control pacers. Tachycardia is a condition in which the heart beats very rapidly; with a ventricular rate higher than 100 bpm and typically above 150 bpm and an atrial rate as high as 400bpm. There are several different pacing modalities which have been suggested for the termination of tachycardia. The underlying principle in all of them is that if a pacer stimulates the heart at least once shortly after a heartbeat, before the next naturally occurring heartbeat at the rapid rate, the heart may successfully revert to normal sinus rhythm. Tachycardia is often the result of electrical feedback within the heart. A natural beat results in the feedback of an electrical stimulus which prema-turely triggers another beat. By interposing a stimu-lated heartbeat, the stability of the feedback loop is disrupted.
In United States Patent 3,942,534 to Spurrell et al. there is disclosed a pacer which, following detection of a tachycardia, generates an atrial (or ventricular) stimulus after a delay inter-val. If that stimulus is not successful in terminat- -ing the ccndition, then another stimulus is generated after another premature heartbeat following a slightly different delay. The device constantly adjusts the delay interval by scanning through a predetermined delay range. Stimulation ceases as soon as the heart is restored to sinus rhythm. If successful reversion is not achieved durinq one complete scan, then the cycle is repeated. The device further provides a second stimulus following the first, both stimuli occurring within the tachycardia cycle, i.e. before the next naturally occurring rapid beat. The time 2~3~8~
period between a heartbeat and the first stimulus is known as the initial delay, while the time period between the first stimulus and the second stimulus is known as the coupled interval. In this device, once the coupled interval is set by a physician it is fixed, and therefore the second stimulus always occurs a predetermined time after the first stimulus, no matter when the first stimulus occurs after the last heartbeat or how fast is the rate of the tachycardia.
In United States Patent 4,390,021 to Spurrell et al. there is disclosed a pacer for con-trolling tachycardia in which the coupled interval, as well as the initial delay, is scanned. The time pa-rameters which are successful in terminating the tachycardia are stored so that upon confirmation of another tachycardia event, the previously successful time parameters are the first ones to be tried. The device also allows tachycardia to be induced by the physician to aLlow for programming of the initial delay and the coupled interval parameters.
United States Patent 4,398,536 to Nappholz et al. discloses a scanning burst tachycardia control pacer. Following each tachycardia confirmation, a burst of a programmed number of stimulating atrial (or ventricular) pulses is generated. The rates of the bursts increase from cycle to cycle whereby following each tachycardia confirmation, a pulse burst at a different rate is generated. The rate of a burst which is successful in terminating tachycardia is stored, and following the next tachycardia confirma-tion, the stored rate is used for the first burst which is generated.
In United States Patent 4,406,287 to Nappholz et al. there is disclosed a variable length scanning burst tachycardia control pacer. The physi-cian programs the maximum number of pulses in a hurst.
The number of pulses in a burst is scanned, and the number which is successful in terminating tachycardia is registered so that it is available for first use when a new tachycardia episode is confirmed. Succes-sive bursts, all at the same rate, have different numbers of pulses, the pulse number scanning being in the upward direction. If all bursts are unsuccessful, a new rate is tried and the number scanning begins over again. Thus all combinations of rates and pulse numbers are tried, with the successful combination being used first following the next tachycardia con-firmation.
United States Patent 4,408,606 to Spurrell et al. discloses a rate related tachycardia control pacer. Following tachycardia confirmation, a burst of at least three stimulating pulses is generated. The time intervals between successive pulses decrease by a fixed decrement; hence the rate of the pulses in-creases during each cycle oP operation. The first pulse is generated following the last heartbeat which is used to confirm tachycardia at a time which is dependent on the tachycardia rate. The time delay between the last heartbeat and the first pulse in the burst is equal to the time interval between the last two heartbeats less the fixed decrement which charac-terizes successive time intervals between stimulating pulses.
Dual chamber heart pacers have been devel-oped in order to generate sequential atrial and ven-tricular pacing pulses which closely match the physio-logical requirements of the patient. A conventional dual chamber heart pacer as disclosed in United States Patent No. 4,429,697 to Nappholz et al. includes atri-al beat sensing and pulse generating circuits along 203~ 8~
with ventricular beat sensing and pulse generating circuits. It is known that the detection of a ven-tricular beat or the generation of a ventricular pac-ing pulse initiates the timing of an interval ~nown as the V~ delay. If an atrial beat is not sensed prior to expiration of the VA delay interval, then an atrial pacing pulse is generated. Following the generation of an atrial pacing pulse, or a sensed atrial beat, an interval known as the AV delay is timed. If a ven-tricular beat is not sensed prior to the expiration of the AV delay interval, then a ventricular pacing pulse is generated. With the generation of a ventricular pacing pulse, or the sensing of a ventricular beat, the VA delay timing starts again. This patent de-scribes how the VA delay timing interval may be di-vided into three parts; the atrial refractory period, the Wenckeback timing window, and the P-wave synchrony timing window. It outlines the importance of control-ling the ventricular rate in comparison with the atri-al rate in order to maintain synchrony between the atrium and the ventricle. The patent does not however address the issue of antitachycardia pacing therapy.
Prior art single chamber antitachycardia pacing devices which provide antitachycardia pacing bursts to either the atrium or the ventricle, have shortcomings in that they lack the required synchrony between the atrium and the ventricle, which reduces the percentage of successful reversions. Especially in the case of ventricular antitachycardia pacing, although the pacing may revert an arrhythmia, at the same time however, it increases the risk of adversely affecting the patient by means of a decrease in arte-rial pressure due to the rapid pacing. As a result of the haemodynamic compromise or lowered haemodynamic status of the myocardium during the arrhythmia and _7_ 20318~
pacing, there is a high risk of a ventricular tachy-cardia accelerating to a faster ventricular tachycar-dia and even to a ventricular fibrillation. This has been shown in an article by Fisher et al. entitled "Termination of Ventricular Tachycardia with Burst or Rapid Ventricular Pacing", American Journal of Cardi-ology, Vol. 41 (January, 1978), page 96. Not only does this present a potentially hazardous situation to the patient, but it also makes it more difficult for the device to revert the patient. Reversion would necessarily demand more energy of the device and per-haps even cardioversion or defibrillation therapy which is not available in many pacing devices. Fur-thermore, prior art devices are very limited in the provision of individualized therapy to the patient by patient dependent parameters such as the AV delay.
Many antitachycardia pacing therapy devices at present include defibrillation support within the device in order to provide adequate safety to a pa-tient. It is highly advantageous to prevent the de-velopment of VT's or atrial fibrillations or to termi-nate them quickly if they appear, rather than allowing the arrhythmia to develop to such an extent that a defibrillation shock is necessary.
DISCLOSURE OF THE INVENTION
It is an object of the invention to provide antitachycardia pacing therapy in an automatic im-plantable device with an improvement in patient safety by ensuring that the patient maintains an improved haemodynamic status during application of the anti-tachycardia pacing therapy as compared to prior de-vices.
It is a further object of the invention to provide synchrony between the atrium and the ventricle -8- 20~
during antitachycardia pacing therapy so that the arterial pressure is either maintained or increased during the therapy.
It is a further object of the invention to increase the opportunities for antitachycardia pacing therapy by means of a reliable low risk energy saving therapy with a higher chance of faster and more suc-cessful reversion.
It is a further object of the invention to reduce the number or the necessity of defibrillation shocks given to a patient by preventing the develop-ment of VT's and AF's in a patient by means of a more effective dual chamber antitachycardia pacing algo-rithm.
It is a further object of the invention to provide a means during the application of dual chamber antitachycardia pacing therapy for the detection of inherent QRS complexes and a further means for provid-ing cardioversion or defibrillation therapy if the detected QRS complexes meet programmed x/y and tachy-cardia cycle length criteria, in order to detect acceleration to VF's or fast VT's.
It is a further object of the invention to individualize the antitachycardia pacing therapy to each patient in an automatic implantable dual chamber arrhythmia control system by means of programming parameters such as the AV delay as a percentage of the tachycardia cycle length.
According to the invention, there is pro-vided a dual chamber antitachycardia pacing device for the reversion of tachycardias comprising: means for detecting tachycardia, means for measuring cycle length of said tachycardia, means for determining a VA
inter~al value less than or equal to the tachycardia cycle length, means for determining an initial value : . ' .
, .
2~3~
_9_ AV delay interval, pulse generating means responsive to said tachycardia detecting means for generating heart stimulating pulses to the atrium and to the ventricle, said pulse generating means including means for delivering a series of M pulse trains with each train consisting of a total of 2N pacing pulses deliv-ered in an alternating sequence to the ventricle and to the atrium, the timing of said delivered pulses being in accordance with the values of the VA interval and the AV interval whereby each train comprises the delivery of a pacing pulse to the atrium at the expi-ration of each of N VA delay intervals and a pacing pulse to the ventricle at the expiration of each of N
AV delay intervals, and means for varying the AV delay interval from the initial value at least once prior to completion of the series of M pulse trains. The appa-ratus may also include confirmation means for confirm-ing the presence of the tachycardia prior to enabling the pulse generating means. In this case the pulse generating means is responsive to the confirmation means.
Also in accordance with the invention, the device may include means for sensing inherent QRS
complexes during the time between delivery of the pacing pulse trains, means for determining an acceler-ation cycle length value less than the tachycardia cycle length, means for measuring cycle length of the sensed QRS complexes, and means for delivering at least one of cardioversion and defibrillation when a number of cycle lengths of the sensed QRS complexes are less than the acceleration detection cycle length.
According to the invention, there is further provided a method of antitachycardia pacing in a dual chamber pacing device comprising the steps of: de-tecting the presence of a tachycardia, measuring the ~ . .
~3~8a4 tachycardia cycle length, determining a VA interval value less than or equal to the tachycardia cycle length, determining an initial value of the AV delay interval, delivering a pulse to the ventricle, deliv-ering a pulse to the atrium at the expiration of the determined VA interval value, delivering a pulse to the ventricle at the expiration of the AV interval value, repeating pulse delivery to the atrium and the ventricle until the expiration of N VA intervals and N
AV intervals thereby completing a first train of pul-ses, delivering a series of M trains of pulses similar to said first train of pulses, varying the AV delay -interval value from the programmed initial value at least once prior to the completion of the series of M
trains of pulses. The method may also include the step of confirming the presence of tachycardia prior to delivery of the antitachycardia pacing pulses.
The method of the invention may also include the steps of sensing inherent QRS complexes during the time between the delivery of the trains of pacing pulses, determining an acceleration detection cycle length value less than the tachycardia cycle length, measuring cycle lengths of the sensed QRS complexes, and delivering at least one of cardioversion and defi-brillation when a number of the cycle lengths of the sensed QRS complexes are less than the acceleration detection cycle length.
BRIEF DESC~IPTION OF THE DRAWINGS
Further objects, features and advantages of the invention will become apparent upon consideration of the following detailed description in conjunction with the drawings in which:
FIG. 1 is a block diagram of a dual chamber arrhythmia control system (ACS);
. , ' :
' :
' '' '; ,' ~' ' ' " ' ' ' 2 ~3 18 ~ ~ -FIG. 2 is a block diagram of the pacemaker of FIG. l;
FIG. 3 is a block diagram of the micropro-cessor of FIG.;
FIG. 4 illustrates an embodiment of the antitachycardia pacing algorithm according to the invention;
FIG. 5 illustrates a further embodiment of the dual chamber antitachycardia pacing algorithm according to the invention incorporating overdrive antitachycardia pacing; and FIG. 6 is a flow chart for detection of acceleration to VF/fast VT during dual chamber anti-tachycardia pacing therapy.
Best Mode for Carrvinq Out the Invention Referring to FIG. 1, there is depicted a block diagram of an arrhythmia control system 1.
System 1 is designed to be implantable in a patient and includes a pulse module 10 and appropriate leads for connecting module 10 to a patient's heart 11.
More particularly, system l will generally include an atrial cardiac lead 12 extending to the atrium of the patient's heart for the administration of therapy to the atrium and a ventricular cardiac lead 13 extending to the ventricle of the patient's heart for the ad-ministration of therapy to the ventricle. System 1 generally also includes a pacemaker 17 for the detec-tion of analog signals representing cardiac electrical activity and for the delivery of pacing pulses to the heart; a microprocessor 19 which, in response to vari-ous inputs received from the pacemaker 17 as well as from a defibrillator 16, performs various operations so as to generate different control and data outputs to both pacemaker 17 and defibrillator 16; and a power .
.
-12- 203~
supply 18 for the provision of a reliable voltage level to pacemaker 17, microprocessor 19 and defibril-lator 16 by suitable electrical conductors (not shown). Defibrillator 16 produces a high voltage to charge its capacitors and then discharges them in response to control signals from microprocessor l9. A
defibrillator electrode lead 14 transfers the energy of a defibrillator shock 15 from the implanted pulse module 10 to the heart 11.
~ icroprocessor 19 is connected to a RAM/ROM
unit 121 by an address and data bus 122. An end-of--life (EOL) signal line 124 is used to provide, to microprocessor 19, a logic signal indicative of the approach of battery failure in power supply 18.
As more fully described below, microproces-sor 19 and pacemaker 17 are connected by a communica-tion bus 42, an atrial sense line 45, an atrial pace control line 46, an atrial sensitivity control bus 43, an atrial pace energy control bus 44, a ventricular sense line 49, a ventricular pace control line 50, a ventricular sensitivity control bus 47, and a ventric-ular pace energy control bus 48. As also more fully described below, microprocessor 19 is connected to defibrillator 16 by a charged voltage level line 61, a charge control bus 60, a shock control bus 59, and a dump control bus 58.
Referring to FIG. 2, pacemaker 17 comprises circuitry for atrial pacing 24, ventricular pacing 34, atrial sensing 2S, ventricular sensing 35, and teleme-try 30. In addition, pacemaker 17 includes a control block 39 which includes an interface to microprocessor lg -In operation, sensing circuits 25 and 35detect respective atrial and ventricular analog sig-nals 23 and 33 from the heart 11 and convert ~he de--13- 20318~4 tected signals to digital signals. In addition, the sensing circuits 25 and 35 receive an input atrial sense control 27 and an input ventricular sense con-trol 37, respectively, from the control block 39 which determines the sensitivity applied to the detection circuit. As more fully described below, a change in this sensitivity will affect the voltage deviation re-quired at the sensing electrode for a sense to be registered. The operation of the logic which changes the sensitivity is described in greater detail in copending ~nited States Patent Application Serial No.
187,797 of Richard Grevis and Norma Louise Gilli, filed April 29, 1988, entitled "Apparatus And Method For Controlling Multiple Sensitivities In Arrhythmia Control System Including Post Therapy Pacing Delay,"
which is assigned to the assignee of the present in-vention and is incorporated herein by reference.
Atrial pacing circuit 24 receives from con-trol block 3g via an atrial pacing control bus 28 an atrial pace control input and an atrial pacing energy control input. Similarly, ventricular pacing circuit 34 receives from control block 39, via a ventricular pacing control bus 38, a ventricular pace control input and a ventricular pacing energy control input.
The atrial and ventricular pace control inputs deter-mine the respective types of atrial and ventricular pacing to occur, while the atrial and ventricular pacing energy control inputs determine the respective magnitudes of the pulse energy. The operation of the logic which changes the pulse energy is described in greater detail in United States Patent No. 4,869,252 of Norma Louise Gilli, issued September 26, 1989, entitled "Apparatus And Method For Controlling Pulse Energy In Antitachyarrhythmia And Bradycardia Pacing Devices," which is assigned to the assignee of the -14- 2~318~
present invention and is incorporated herein by refer-ence.
Telemetry circuit 30 provides a bidirec-tional link between control block 39 of pacemaker 17 and an external device such as a programmer. It al-lows data such as the operating parameters to be read from or altered in the implanted module 10.
Referring to FIG. 3, microprocessor 19 com-prises two 16-bit timers 51 and 52, CPU 53, vectored interrupts block 54, ROM 55, RAM 56, external memory 57, ports 41 and an internal communications bus 40.
~AM 56 acts as a scratch pad and active memory during execution of the various programs stored in ROM 55 and used by microprocessor 19. These programs include system supervisory programs, detection algorithms for detecting and confirming various arrhythmias, and programming for implementing the logic flow diagram of FIG. 6, as well as storage programs for storing, in external memory 57, data concerning the functioning of module 10 and the electrogram provided by ventricular cardiac lead 13 (FIG. 1). Timers 51 and 52, and asso-ciated control software, implement some timing func-tions required by microprocessor 19 without resort entirely to software, thus reducing computational loads on and power dissipation by CPU 53.
Signals received from telemetry circuit 30 permit an external programmer (not shown) to change the operating parameters of pacemaker 17 by supplying appropriate signals to control block 39. Communica-tions bus 42 serves to provide signals indicative of such control to microprocessor 19. Thus, it is also possible for an external programmer to control opera-tion of defibrillator 16 by means of signals provided to microprocessor 19.
Appropriate telemetry commands may cause 203~
telemetry circuit 30 to transmit data to the external programmer. Data stored is read out, by microproces-sor 19, on to communications bus 42, through control block 39 in pacemaker 17, and into telemetry circuit 30 for transmission to the external programmer by a transmittex in telemetry circuit 30.
Microprocessor 19 receives various status and/or control inputs from pacemaker 17 and defi~ril-lator 16, such as the sense signals on sense lines 45 and 45. It performs operations, such as arrhythmia detection, and produces outputs, such as the atrial pace control on line 46 and the ventricular pace con-trol on line 50, which determine the type of pacing that is to take place. Other control outputs gener-ated by microprocessor 19 includa the atrial and ven-tricular pacing energy controls on lines 44 and 48, respectively, which determine the magnitude of the pulse energy, the shock control on line 59 which sig-nals that a shock is to be delivered to the patient, the dump control on bus 58 which indicates that a shock is to be dumped at an internal load within the defibrillator, the charge control on bus 60 which determines the voltage level of the shock to be deliv-ered, and the atrial and ventricular sensitivity con-trols on buses 43 and 47, respectively, which deter-mine the sensitivity settings of the sensing circuits.
Charge voltage level line 61 provides a digital signal representative of charge voltage from an analog-to-digital converter within defibrillator 16, thus pro-viding a feedback loop which assures that a shock of proper energy level is delivered by defibrillator 16.
Referring to FIG. 4, there is depicted in illustrative format one embodiment of the antitachy-cardia pacing algorithm ac~ording to the invention. A
series of M (M = 4) pacing trains (a pacing train is a 2~3~54 series of pacing spikes controllably delivered in rapid succession ) are delivered. For train 1, the programmed initial AV delay (the atrial to ventricular delay) interval is lOms. During a ventricular tachy-cardia the atrium and the ventricle are often in dis-sociation, therefore it is preferable for the dual chamber antitachycardia pacing to begin with a very short AV delay interval in order to re-establish asso-ciation or synchrony as soon as possible between both chambers of the heart. The tachycardia cycle length (TCL) is 300ms. The VA delay interval (the ventricu-lar to atrial interval) is calculated as a program-mable percentage of the TCL for the purpose of adapt-ing to the varying cycle lengths of tachycardias, and has been programmed to seventy percent of the TCL
(300ms) in this embodiment, thereby establishing the calculated V~ delay interval as 210ms. In this em-bodiment, the percentage of the TCL is taken as an average over the four previous sensed intervals, and remains fixed at this value (210 ms) during the course of the therapy. For train 1, N = 4, so that at the expiration of each of the 4 VA delay intervals of 210ms, an atrial pulse is delivered and at the expira-tion of each of the four AV delay intervals of lOms a pulse is delivered to the ventricle, so that there are a total of N pairs of pulses (or 2N = 8 pulses) deliv-ered during train 1.
In train 2 of FIG. 4, the AV delay interval has been programmed to increment in value from the low initial value of lOms in train 1 to the new value of 50ms. The variation of the AV delay interval is exe-cuted by computer software by standard methods known to those skilled in the art. In the same manner in trains 3 and 4 of FIG. 4, the AV delay interval in-creases at the end of trains 2 and 3 to the increased -17- 20318~j4 values of lOOms and 150ms, respectively. In trains 2, 3, and 4, N = 4, as in train 1, thereby delivering N
defibrillating mode. After a period of time to charge the capacitor, a defibrillation shock is delivered to the patient.
Improvements on this device were contained in a multiprogrammable, telemetric, implantable defi-brillator which is disclosed in copending Patent Ap-plication Serial No. 239,624 entitled "Reconfirmation Prior to Shock in Implantable Defibrillator". The device contains a bradycardia support system as well as a high energy shock system to revert ventricular tachycardias to normal sinus rhythm. On reconfirma-tion of the presence of a tachycardia, a shoc~ is delivered to the patient at a predetermined time or when the desired energy level is reached.
As cardioversion or defibrillation shocks can be very unpleasant to a patient, especially when delivered frequently, it became necessary therefore to provide a device which included antitachycardia pacing therapy along with bradycardia support pacing therapy and defibrillation or cardioversion therapy, so that the implanted device could automatically provide the necessary therapy from a range of therapies offered by the device. Hence a further development in the field of combined implantable devices is described in co-pending United States patent application No. 187,787, to Grevis and Gilli, filed April 29, 1988, and enti-tled "Apparatus and Method for Controlling Multiple Sensitivities in Arrhythmia Control Systems Including Post Therapy Pacing Delay", assigned to the assignee of the present invention. This device is a microcom-puter based arrhythmia control system which is pro-grammable by means of a telemetric link. The device provides single chamber bradycardia support pacing, antitachycardia pacing, and cardioversion or defibril-lation shocks for restoring normal sinus rhythm to a - . .
20318~4 patient.
Additionally, various specific developments have been made in the field of tachycardia control pacers. Tachycardia is a condition in which the heart beats very rapidly; with a ventricular rate higher than 100 bpm and typically above 150 bpm and an atrial rate as high as 400bpm. There are several different pacing modalities which have been suggested for the termination of tachycardia. The underlying principle in all of them is that if a pacer stimulates the heart at least once shortly after a heartbeat, before the next naturally occurring heartbeat at the rapid rate, the heart may successfully revert to normal sinus rhythm. Tachycardia is often the result of electrical feedback within the heart. A natural beat results in the feedback of an electrical stimulus which prema-turely triggers another beat. By interposing a stimu-lated heartbeat, the stability of the feedback loop is disrupted.
In United States Patent 3,942,534 to Spurrell et al. there is disclosed a pacer which, following detection of a tachycardia, generates an atrial (or ventricular) stimulus after a delay inter-val. If that stimulus is not successful in terminat- -ing the ccndition, then another stimulus is generated after another premature heartbeat following a slightly different delay. The device constantly adjusts the delay interval by scanning through a predetermined delay range. Stimulation ceases as soon as the heart is restored to sinus rhythm. If successful reversion is not achieved durinq one complete scan, then the cycle is repeated. The device further provides a second stimulus following the first, both stimuli occurring within the tachycardia cycle, i.e. before the next naturally occurring rapid beat. The time 2~3~8~
period between a heartbeat and the first stimulus is known as the initial delay, while the time period between the first stimulus and the second stimulus is known as the coupled interval. In this device, once the coupled interval is set by a physician it is fixed, and therefore the second stimulus always occurs a predetermined time after the first stimulus, no matter when the first stimulus occurs after the last heartbeat or how fast is the rate of the tachycardia.
In United States Patent 4,390,021 to Spurrell et al. there is disclosed a pacer for con-trolling tachycardia in which the coupled interval, as well as the initial delay, is scanned. The time pa-rameters which are successful in terminating the tachycardia are stored so that upon confirmation of another tachycardia event, the previously successful time parameters are the first ones to be tried. The device also allows tachycardia to be induced by the physician to aLlow for programming of the initial delay and the coupled interval parameters.
United States Patent 4,398,536 to Nappholz et al. discloses a scanning burst tachycardia control pacer. Following each tachycardia confirmation, a burst of a programmed number of stimulating atrial (or ventricular) pulses is generated. The rates of the bursts increase from cycle to cycle whereby following each tachycardia confirmation, a pulse burst at a different rate is generated. The rate of a burst which is successful in terminating tachycardia is stored, and following the next tachycardia confirma-tion, the stored rate is used for the first burst which is generated.
In United States Patent 4,406,287 to Nappholz et al. there is disclosed a variable length scanning burst tachycardia control pacer. The physi-cian programs the maximum number of pulses in a hurst.
The number of pulses in a burst is scanned, and the number which is successful in terminating tachycardia is registered so that it is available for first use when a new tachycardia episode is confirmed. Succes-sive bursts, all at the same rate, have different numbers of pulses, the pulse number scanning being in the upward direction. If all bursts are unsuccessful, a new rate is tried and the number scanning begins over again. Thus all combinations of rates and pulse numbers are tried, with the successful combination being used first following the next tachycardia con-firmation.
United States Patent 4,408,606 to Spurrell et al. discloses a rate related tachycardia control pacer. Following tachycardia confirmation, a burst of at least three stimulating pulses is generated. The time intervals between successive pulses decrease by a fixed decrement; hence the rate of the pulses in-creases during each cycle oP operation. The first pulse is generated following the last heartbeat which is used to confirm tachycardia at a time which is dependent on the tachycardia rate. The time delay between the last heartbeat and the first pulse in the burst is equal to the time interval between the last two heartbeats less the fixed decrement which charac-terizes successive time intervals between stimulating pulses.
Dual chamber heart pacers have been devel-oped in order to generate sequential atrial and ven-tricular pacing pulses which closely match the physio-logical requirements of the patient. A conventional dual chamber heart pacer as disclosed in United States Patent No. 4,429,697 to Nappholz et al. includes atri-al beat sensing and pulse generating circuits along 203~ 8~
with ventricular beat sensing and pulse generating circuits. It is known that the detection of a ven-tricular beat or the generation of a ventricular pac-ing pulse initiates the timing of an interval ~nown as the V~ delay. If an atrial beat is not sensed prior to expiration of the VA delay interval, then an atrial pacing pulse is generated. Following the generation of an atrial pacing pulse, or a sensed atrial beat, an interval known as the AV delay is timed. If a ven-tricular beat is not sensed prior to the expiration of the AV delay interval, then a ventricular pacing pulse is generated. With the generation of a ventricular pacing pulse, or the sensing of a ventricular beat, the VA delay timing starts again. This patent de-scribes how the VA delay timing interval may be di-vided into three parts; the atrial refractory period, the Wenckeback timing window, and the P-wave synchrony timing window. It outlines the importance of control-ling the ventricular rate in comparison with the atri-al rate in order to maintain synchrony between the atrium and the ventricle. The patent does not however address the issue of antitachycardia pacing therapy.
Prior art single chamber antitachycardia pacing devices which provide antitachycardia pacing bursts to either the atrium or the ventricle, have shortcomings in that they lack the required synchrony between the atrium and the ventricle, which reduces the percentage of successful reversions. Especially in the case of ventricular antitachycardia pacing, although the pacing may revert an arrhythmia, at the same time however, it increases the risk of adversely affecting the patient by means of a decrease in arte-rial pressure due to the rapid pacing. As a result of the haemodynamic compromise or lowered haemodynamic status of the myocardium during the arrhythmia and _7_ 20318~
pacing, there is a high risk of a ventricular tachy-cardia accelerating to a faster ventricular tachycar-dia and even to a ventricular fibrillation. This has been shown in an article by Fisher et al. entitled "Termination of Ventricular Tachycardia with Burst or Rapid Ventricular Pacing", American Journal of Cardi-ology, Vol. 41 (January, 1978), page 96. Not only does this present a potentially hazardous situation to the patient, but it also makes it more difficult for the device to revert the patient. Reversion would necessarily demand more energy of the device and per-haps even cardioversion or defibrillation therapy which is not available in many pacing devices. Fur-thermore, prior art devices are very limited in the provision of individualized therapy to the patient by patient dependent parameters such as the AV delay.
Many antitachycardia pacing therapy devices at present include defibrillation support within the device in order to provide adequate safety to a pa-tient. It is highly advantageous to prevent the de-velopment of VT's or atrial fibrillations or to termi-nate them quickly if they appear, rather than allowing the arrhythmia to develop to such an extent that a defibrillation shock is necessary.
DISCLOSURE OF THE INVENTION
It is an object of the invention to provide antitachycardia pacing therapy in an automatic im-plantable device with an improvement in patient safety by ensuring that the patient maintains an improved haemodynamic status during application of the anti-tachycardia pacing therapy as compared to prior de-vices.
It is a further object of the invention to provide synchrony between the atrium and the ventricle -8- 20~
during antitachycardia pacing therapy so that the arterial pressure is either maintained or increased during the therapy.
It is a further object of the invention to increase the opportunities for antitachycardia pacing therapy by means of a reliable low risk energy saving therapy with a higher chance of faster and more suc-cessful reversion.
It is a further object of the invention to reduce the number or the necessity of defibrillation shocks given to a patient by preventing the develop-ment of VT's and AF's in a patient by means of a more effective dual chamber antitachycardia pacing algo-rithm.
It is a further object of the invention to provide a means during the application of dual chamber antitachycardia pacing therapy for the detection of inherent QRS complexes and a further means for provid-ing cardioversion or defibrillation therapy if the detected QRS complexes meet programmed x/y and tachy-cardia cycle length criteria, in order to detect acceleration to VF's or fast VT's.
It is a further object of the invention to individualize the antitachycardia pacing therapy to each patient in an automatic implantable dual chamber arrhythmia control system by means of programming parameters such as the AV delay as a percentage of the tachycardia cycle length.
According to the invention, there is pro-vided a dual chamber antitachycardia pacing device for the reversion of tachycardias comprising: means for detecting tachycardia, means for measuring cycle length of said tachycardia, means for determining a VA
inter~al value less than or equal to the tachycardia cycle length, means for determining an initial value : . ' .
, .
2~3~
_9_ AV delay interval, pulse generating means responsive to said tachycardia detecting means for generating heart stimulating pulses to the atrium and to the ventricle, said pulse generating means including means for delivering a series of M pulse trains with each train consisting of a total of 2N pacing pulses deliv-ered in an alternating sequence to the ventricle and to the atrium, the timing of said delivered pulses being in accordance with the values of the VA interval and the AV interval whereby each train comprises the delivery of a pacing pulse to the atrium at the expi-ration of each of N VA delay intervals and a pacing pulse to the ventricle at the expiration of each of N
AV delay intervals, and means for varying the AV delay interval from the initial value at least once prior to completion of the series of M pulse trains. The appa-ratus may also include confirmation means for confirm-ing the presence of the tachycardia prior to enabling the pulse generating means. In this case the pulse generating means is responsive to the confirmation means.
Also in accordance with the invention, the device may include means for sensing inherent QRS
complexes during the time between delivery of the pacing pulse trains, means for determining an acceler-ation cycle length value less than the tachycardia cycle length, means for measuring cycle length of the sensed QRS complexes, and means for delivering at least one of cardioversion and defibrillation when a number of cycle lengths of the sensed QRS complexes are less than the acceleration detection cycle length.
According to the invention, there is further provided a method of antitachycardia pacing in a dual chamber pacing device comprising the steps of: de-tecting the presence of a tachycardia, measuring the ~ . .
~3~8a4 tachycardia cycle length, determining a VA interval value less than or equal to the tachycardia cycle length, determining an initial value of the AV delay interval, delivering a pulse to the ventricle, deliv-ering a pulse to the atrium at the expiration of the determined VA interval value, delivering a pulse to the ventricle at the expiration of the AV interval value, repeating pulse delivery to the atrium and the ventricle until the expiration of N VA intervals and N
AV intervals thereby completing a first train of pul-ses, delivering a series of M trains of pulses similar to said first train of pulses, varying the AV delay -interval value from the programmed initial value at least once prior to the completion of the series of M
trains of pulses. The method may also include the step of confirming the presence of tachycardia prior to delivery of the antitachycardia pacing pulses.
The method of the invention may also include the steps of sensing inherent QRS complexes during the time between the delivery of the trains of pacing pulses, determining an acceleration detection cycle length value less than the tachycardia cycle length, measuring cycle lengths of the sensed QRS complexes, and delivering at least one of cardioversion and defi-brillation when a number of the cycle lengths of the sensed QRS complexes are less than the acceleration detection cycle length.
BRIEF DESC~IPTION OF THE DRAWINGS
Further objects, features and advantages of the invention will become apparent upon consideration of the following detailed description in conjunction with the drawings in which:
FIG. 1 is a block diagram of a dual chamber arrhythmia control system (ACS);
. , ' :
' :
' '' '; ,' ~' ' ' " ' ' ' 2 ~3 18 ~ ~ -FIG. 2 is a block diagram of the pacemaker of FIG. l;
FIG. 3 is a block diagram of the micropro-cessor of FIG.;
FIG. 4 illustrates an embodiment of the antitachycardia pacing algorithm according to the invention;
FIG. 5 illustrates a further embodiment of the dual chamber antitachycardia pacing algorithm according to the invention incorporating overdrive antitachycardia pacing; and FIG. 6 is a flow chart for detection of acceleration to VF/fast VT during dual chamber anti-tachycardia pacing therapy.
Best Mode for Carrvinq Out the Invention Referring to FIG. 1, there is depicted a block diagram of an arrhythmia control system 1.
System 1 is designed to be implantable in a patient and includes a pulse module 10 and appropriate leads for connecting module 10 to a patient's heart 11.
More particularly, system l will generally include an atrial cardiac lead 12 extending to the atrium of the patient's heart for the administration of therapy to the atrium and a ventricular cardiac lead 13 extending to the ventricle of the patient's heart for the ad-ministration of therapy to the ventricle. System 1 generally also includes a pacemaker 17 for the detec-tion of analog signals representing cardiac electrical activity and for the delivery of pacing pulses to the heart; a microprocessor 19 which, in response to vari-ous inputs received from the pacemaker 17 as well as from a defibrillator 16, performs various operations so as to generate different control and data outputs to both pacemaker 17 and defibrillator 16; and a power .
.
-12- 203~
supply 18 for the provision of a reliable voltage level to pacemaker 17, microprocessor 19 and defibril-lator 16 by suitable electrical conductors (not shown). Defibrillator 16 produces a high voltage to charge its capacitors and then discharges them in response to control signals from microprocessor l9. A
defibrillator electrode lead 14 transfers the energy of a defibrillator shock 15 from the implanted pulse module 10 to the heart 11.
~ icroprocessor 19 is connected to a RAM/ROM
unit 121 by an address and data bus 122. An end-of--life (EOL) signal line 124 is used to provide, to microprocessor 19, a logic signal indicative of the approach of battery failure in power supply 18.
As more fully described below, microproces-sor 19 and pacemaker 17 are connected by a communica-tion bus 42, an atrial sense line 45, an atrial pace control line 46, an atrial sensitivity control bus 43, an atrial pace energy control bus 44, a ventricular sense line 49, a ventricular pace control line 50, a ventricular sensitivity control bus 47, and a ventric-ular pace energy control bus 48. As also more fully described below, microprocessor 19 is connected to defibrillator 16 by a charged voltage level line 61, a charge control bus 60, a shock control bus 59, and a dump control bus 58.
Referring to FIG. 2, pacemaker 17 comprises circuitry for atrial pacing 24, ventricular pacing 34, atrial sensing 2S, ventricular sensing 35, and teleme-try 30. In addition, pacemaker 17 includes a control block 39 which includes an interface to microprocessor lg -In operation, sensing circuits 25 and 35detect respective atrial and ventricular analog sig-nals 23 and 33 from the heart 11 and convert ~he de--13- 20318~4 tected signals to digital signals. In addition, the sensing circuits 25 and 35 receive an input atrial sense control 27 and an input ventricular sense con-trol 37, respectively, from the control block 39 which determines the sensitivity applied to the detection circuit. As more fully described below, a change in this sensitivity will affect the voltage deviation re-quired at the sensing electrode for a sense to be registered. The operation of the logic which changes the sensitivity is described in greater detail in copending ~nited States Patent Application Serial No.
187,797 of Richard Grevis and Norma Louise Gilli, filed April 29, 1988, entitled "Apparatus And Method For Controlling Multiple Sensitivities In Arrhythmia Control System Including Post Therapy Pacing Delay,"
which is assigned to the assignee of the present in-vention and is incorporated herein by reference.
Atrial pacing circuit 24 receives from con-trol block 3g via an atrial pacing control bus 28 an atrial pace control input and an atrial pacing energy control input. Similarly, ventricular pacing circuit 34 receives from control block 39, via a ventricular pacing control bus 38, a ventricular pace control input and a ventricular pacing energy control input.
The atrial and ventricular pace control inputs deter-mine the respective types of atrial and ventricular pacing to occur, while the atrial and ventricular pacing energy control inputs determine the respective magnitudes of the pulse energy. The operation of the logic which changes the pulse energy is described in greater detail in United States Patent No. 4,869,252 of Norma Louise Gilli, issued September 26, 1989, entitled "Apparatus And Method For Controlling Pulse Energy In Antitachyarrhythmia And Bradycardia Pacing Devices," which is assigned to the assignee of the -14- 2~318~
present invention and is incorporated herein by refer-ence.
Telemetry circuit 30 provides a bidirec-tional link between control block 39 of pacemaker 17 and an external device such as a programmer. It al-lows data such as the operating parameters to be read from or altered in the implanted module 10.
Referring to FIG. 3, microprocessor 19 com-prises two 16-bit timers 51 and 52, CPU 53, vectored interrupts block 54, ROM 55, RAM 56, external memory 57, ports 41 and an internal communications bus 40.
~AM 56 acts as a scratch pad and active memory during execution of the various programs stored in ROM 55 and used by microprocessor 19. These programs include system supervisory programs, detection algorithms for detecting and confirming various arrhythmias, and programming for implementing the logic flow diagram of FIG. 6, as well as storage programs for storing, in external memory 57, data concerning the functioning of module 10 and the electrogram provided by ventricular cardiac lead 13 (FIG. 1). Timers 51 and 52, and asso-ciated control software, implement some timing func-tions required by microprocessor 19 without resort entirely to software, thus reducing computational loads on and power dissipation by CPU 53.
Signals received from telemetry circuit 30 permit an external programmer (not shown) to change the operating parameters of pacemaker 17 by supplying appropriate signals to control block 39. Communica-tions bus 42 serves to provide signals indicative of such control to microprocessor 19. Thus, it is also possible for an external programmer to control opera-tion of defibrillator 16 by means of signals provided to microprocessor 19.
Appropriate telemetry commands may cause 203~
telemetry circuit 30 to transmit data to the external programmer. Data stored is read out, by microproces-sor 19, on to communications bus 42, through control block 39 in pacemaker 17, and into telemetry circuit 30 for transmission to the external programmer by a transmittex in telemetry circuit 30.
Microprocessor 19 receives various status and/or control inputs from pacemaker 17 and defi~ril-lator 16, such as the sense signals on sense lines 45 and 45. It performs operations, such as arrhythmia detection, and produces outputs, such as the atrial pace control on line 46 and the ventricular pace con-trol on line 50, which determine the type of pacing that is to take place. Other control outputs gener-ated by microprocessor 19 includa the atrial and ven-tricular pacing energy controls on lines 44 and 48, respectively, which determine the magnitude of the pulse energy, the shock control on line 59 which sig-nals that a shock is to be delivered to the patient, the dump control on bus 58 which indicates that a shock is to be dumped at an internal load within the defibrillator, the charge control on bus 60 which determines the voltage level of the shock to be deliv-ered, and the atrial and ventricular sensitivity con-trols on buses 43 and 47, respectively, which deter-mine the sensitivity settings of the sensing circuits.
Charge voltage level line 61 provides a digital signal representative of charge voltage from an analog-to-digital converter within defibrillator 16, thus pro-viding a feedback loop which assures that a shock of proper energy level is delivered by defibrillator 16.
Referring to FIG. 4, there is depicted in illustrative format one embodiment of the antitachy-cardia pacing algorithm ac~ording to the invention. A
series of M (M = 4) pacing trains (a pacing train is a 2~3~54 series of pacing spikes controllably delivered in rapid succession ) are delivered. For train 1, the programmed initial AV delay (the atrial to ventricular delay) interval is lOms. During a ventricular tachy-cardia the atrium and the ventricle are often in dis-sociation, therefore it is preferable for the dual chamber antitachycardia pacing to begin with a very short AV delay interval in order to re-establish asso-ciation or synchrony as soon as possible between both chambers of the heart. The tachycardia cycle length (TCL) is 300ms. The VA delay interval (the ventricu-lar to atrial interval) is calculated as a program-mable percentage of the TCL for the purpose of adapt-ing to the varying cycle lengths of tachycardias, and has been programmed to seventy percent of the TCL
(300ms) in this embodiment, thereby establishing the calculated V~ delay interval as 210ms. In this em-bodiment, the percentage of the TCL is taken as an average over the four previous sensed intervals, and remains fixed at this value (210 ms) during the course of the therapy. For train 1, N = 4, so that at the expiration of each of the 4 VA delay intervals of 210ms, an atrial pulse is delivered and at the expira-tion of each of the four AV delay intervals of lOms a pulse is delivered to the ventricle, so that there are a total of N pairs of pulses (or 2N = 8 pulses) deliv-ered during train 1.
In train 2 of FIG. 4, the AV delay interval has been programmed to increment in value from the low initial value of lOms in train 1 to the new value of 50ms. The variation of the AV delay interval is exe-cuted by computer software by standard methods known to those skilled in the art. In the same manner in trains 3 and 4 of FIG. 4, the AV delay interval in-creases at the end of trains 2 and 3 to the increased -17- 20318~j4 values of lOOms and 150ms, respectively. In trains 2, 3, and 4, N = 4, as in train 1, thereby delivering N
(4) pairs of pacing pulses in each train. In this particular embodiment of the invention, the value of N
is equal in all of the trains. However, N is a pro-grammable parameter and may be programmed by the phy-sician to suit the needs of a particular patient.
Furthermore, N may have differing values for different trains in alternate embodiments of the invention.
As shown in FIG. 4, the AV delay interval increments from lOms in train 1 to 150ms in train 4.
This parameter is also programmable and is patient dependent. The AV delay may increment at the end of each train as in the preferred embodiment. However, the variation in the AV delay is not necessarily lim-ited to steady increments. It may include any combi-nation of increases, plateaus and decreases in its value. Although it is preferable to include the vari-ations at the end of each train, these may be executed at any time within a train and still fall within the scope of the invention.
Preferably, the initial value AV delay in-terval is less than or equal to 60 ms.
The VA delay interval in the preferred em-bodiment is programmed as a percentage of the TCL
(70%). ~lthough the invention does not limit the VA
delay interval to a particular range, it has been found that the best results occur when it lies within the range of thirty percent to one hundred percent of the TCL. Furthermore, its value is not necessarily fixed during the antitachycardia therapy, but may vary and still remain within the scope of the invention.
If it is programmed to vary, the initial value is a percentage of the TCL; for example a percentage of the average cycle length of the last four intervals of the -18- 2031 ~3~
detected tachycardia. For instance, the VA delay interval may include various combinations of increas-ing, decreasing, or remaining at a fixed value. Any programmed variations may occur at the end of trains or even within trains, or may even be a function of AV
delay interval variations.
In FIG. 4 the number of trains M is 4, and is also a patient dependent physician programmable parameter. At the completion of the M trains of anti-tachycardia pacing, the combined defibrillator pacing device returns to its normal operating mode including the options of normal dual chamber (DDD) pacing or defibrillation shocks, if necessary. Furthermore, the device may provide bradycardia support pacing, if required, which may include either single chamber or dual chamber bradycardia support pacing.
In FIG. 5 there is shown another embodiment of the dual chamber antitachycardia pacing algorithm.
The TCL is measured at 300ms. The VA interval is programmed to be eighty percent of the TCL, and there-fore assumes the value of 240ms.
The AV delay is programmed to increment in value over 4 trains, and assumes the values of lOms (train 1), 50 ms (train 2), lOOms ttrain 3), and 168ms (train 4). In this embodiment, the value of N varies from N = 4 in train 1, to N = 5 in train 2, and then to N = 6 in trains 3 and 4. The average sinus inter-val is measured prior to a tachycardia and is shown as the previous sinus interval or SI. In this example SI
= 850ms. The AV delay for the previous sinus interval is measured also, and is known as SI AV, and is 210ms in this example. The value of AV delay in train 4 is programmed to be eighty percent of 5I AV, which is eighty percent of 210ms, or 168ms. The reason for including this value in train 4 is that following the .
, -19- 203~3~
final train, the device implements overdrive antit-achycardia pacing at intervals of eighty percent of the intervals of SI in order to "ramp down" prior to the resumption of normal pacing. In this example eighty percent of SI is equal to eighty percent of 850ms or 680ms. This becomes the R-R interval for the overdrive pacing~ The value of VA is set equal to the R-R interval minus the AV delay for the overdrive pac-ing, i.e. VA = 680ms - 168ms = 512ms. The time peri-od for the overdrive pacing is programmable, and in this example it continues for five minutes prior to returning to normal pacing mode.
FIG. 6 is a flowchart for the detection of acceleration to a VF or a fast VT during the applica-tion of the dual chamber antitachycardia pacing thera-py. At 61, normal operating mode is shown and upon the detection of tachycardia and its subsequent confirma-tion (the details of this are not shown on the flow chart), the dual chamber ATP therapy is applied at 62.
It is important, as a safety mechanism for the patient, during the application of any antitachycardia therapy, to prevent acceleration of VT to faster VT or to VF. QRS detection is switched on at 63 during the ATP therapy to detect inherent QRS complexes which may occur either during the VA interval or during the AV
delay. A decision is made at 64 on the basis of whether QRS complexes are detected. If no QRS com-plexes are detected (65), control passes to timeout 77. If time is out (79), i.e. if the programmed time for the dual chamber ATP therapy has expired, then control passes to 76, the end of ATP therapy, and normal operating mode is resumed at 61. If at 77 the time has not expired (78), QRS detection at 63 is again commenced.
If there is detection of QRS complexes at ' 2~3~ 4 66, the next step is 67, where x/y detection is ap-plied to determine whether the ~RS complexes are regu-lar or whether they are just isolated intrinsic beats.
An example of x/y detection, in this embodiment, is 3/4 detection. The acceleration detection window is programmable to an interval less than the detected tachycardia cycle length by an amount delta (300ms in the examples of FIG. 4 and FIG. 5). Delta is program-mable, and may be an absolute value or a percentage of the TCL. If delta is programmed to 75ms, then 300ms -75ms = 225ms. Thus, the acceleration detection window becomes 225ms. The acceleration detection interval is considered sufficient to detect an acceleration of an existing tachycardia. The 3/4 detection means that if any three out of the last four intervals are less than the acceleration detection window (225ms), then the x/y detection criteria are satisfied.
At 68, a decision is made to determine if the 3/4 detection criterion applies to the QRS com-plexes. If the 3/4 detection criterion is not met (69), control passes back to timeout at 77. If the time for therapy has not expired (78), it passes back to QRS detection at 63 and then either bac~ to timeout 77 if no QRS complexes are detected at this time, or back to the application of x/y detection at 67 if QRS
complexes are detected.
If at 70, the 3/4 detection criterion has been met, cardioversion or defibrillation therapy is applied at 74. It has been found safer and more ef-fective to use this acceleration detection combined with cardioversion or defibrillation therapy as shown in Fig. 6 than to wait until the end of ATP therapy and face the possibility of a degeneration to a very fast VT or a VF. After cardioversion or defibrilla-tion therapy at 75, the device returns to its normal ~ .
' ~ , , ,. '' . '~ : ~ :
-21- 2~3~
mode of operation at 61.
Although the invention has been described with reference to a particular embodiment, it is to be understood that this embodiment is merely illustrative of the application of the principles of the invention.
Hence numerous modifications may be made therein and other arrangements may be devised without departing from the spirit and scope of the invention.
is equal in all of the trains. However, N is a pro-grammable parameter and may be programmed by the phy-sician to suit the needs of a particular patient.
Furthermore, N may have differing values for different trains in alternate embodiments of the invention.
As shown in FIG. 4, the AV delay interval increments from lOms in train 1 to 150ms in train 4.
This parameter is also programmable and is patient dependent. The AV delay may increment at the end of each train as in the preferred embodiment. However, the variation in the AV delay is not necessarily lim-ited to steady increments. It may include any combi-nation of increases, plateaus and decreases in its value. Although it is preferable to include the vari-ations at the end of each train, these may be executed at any time within a train and still fall within the scope of the invention.
Preferably, the initial value AV delay in-terval is less than or equal to 60 ms.
The VA delay interval in the preferred em-bodiment is programmed as a percentage of the TCL
(70%). ~lthough the invention does not limit the VA
delay interval to a particular range, it has been found that the best results occur when it lies within the range of thirty percent to one hundred percent of the TCL. Furthermore, its value is not necessarily fixed during the antitachycardia therapy, but may vary and still remain within the scope of the invention.
If it is programmed to vary, the initial value is a percentage of the TCL; for example a percentage of the average cycle length of the last four intervals of the -18- 2031 ~3~
detected tachycardia. For instance, the VA delay interval may include various combinations of increas-ing, decreasing, or remaining at a fixed value. Any programmed variations may occur at the end of trains or even within trains, or may even be a function of AV
delay interval variations.
In FIG. 4 the number of trains M is 4, and is also a patient dependent physician programmable parameter. At the completion of the M trains of anti-tachycardia pacing, the combined defibrillator pacing device returns to its normal operating mode including the options of normal dual chamber (DDD) pacing or defibrillation shocks, if necessary. Furthermore, the device may provide bradycardia support pacing, if required, which may include either single chamber or dual chamber bradycardia support pacing.
In FIG. 5 there is shown another embodiment of the dual chamber antitachycardia pacing algorithm.
The TCL is measured at 300ms. The VA interval is programmed to be eighty percent of the TCL, and there-fore assumes the value of 240ms.
The AV delay is programmed to increment in value over 4 trains, and assumes the values of lOms (train 1), 50 ms (train 2), lOOms ttrain 3), and 168ms (train 4). In this embodiment, the value of N varies from N = 4 in train 1, to N = 5 in train 2, and then to N = 6 in trains 3 and 4. The average sinus inter-val is measured prior to a tachycardia and is shown as the previous sinus interval or SI. In this example SI
= 850ms. The AV delay for the previous sinus interval is measured also, and is known as SI AV, and is 210ms in this example. The value of AV delay in train 4 is programmed to be eighty percent of 5I AV, which is eighty percent of 210ms, or 168ms. The reason for including this value in train 4 is that following the .
, -19- 203~3~
final train, the device implements overdrive antit-achycardia pacing at intervals of eighty percent of the intervals of SI in order to "ramp down" prior to the resumption of normal pacing. In this example eighty percent of SI is equal to eighty percent of 850ms or 680ms. This becomes the R-R interval for the overdrive pacing~ The value of VA is set equal to the R-R interval minus the AV delay for the overdrive pac-ing, i.e. VA = 680ms - 168ms = 512ms. The time peri-od for the overdrive pacing is programmable, and in this example it continues for five minutes prior to returning to normal pacing mode.
FIG. 6 is a flowchart for the detection of acceleration to a VF or a fast VT during the applica-tion of the dual chamber antitachycardia pacing thera-py. At 61, normal operating mode is shown and upon the detection of tachycardia and its subsequent confirma-tion (the details of this are not shown on the flow chart), the dual chamber ATP therapy is applied at 62.
It is important, as a safety mechanism for the patient, during the application of any antitachycardia therapy, to prevent acceleration of VT to faster VT or to VF. QRS detection is switched on at 63 during the ATP therapy to detect inherent QRS complexes which may occur either during the VA interval or during the AV
delay. A decision is made at 64 on the basis of whether QRS complexes are detected. If no QRS com-plexes are detected (65), control passes to timeout 77. If time is out (79), i.e. if the programmed time for the dual chamber ATP therapy has expired, then control passes to 76, the end of ATP therapy, and normal operating mode is resumed at 61. If at 77 the time has not expired (78), QRS detection at 63 is again commenced.
If there is detection of QRS complexes at ' 2~3~ 4 66, the next step is 67, where x/y detection is ap-plied to determine whether the ~RS complexes are regu-lar or whether they are just isolated intrinsic beats.
An example of x/y detection, in this embodiment, is 3/4 detection. The acceleration detection window is programmable to an interval less than the detected tachycardia cycle length by an amount delta (300ms in the examples of FIG. 4 and FIG. 5). Delta is program-mable, and may be an absolute value or a percentage of the TCL. If delta is programmed to 75ms, then 300ms -75ms = 225ms. Thus, the acceleration detection window becomes 225ms. The acceleration detection interval is considered sufficient to detect an acceleration of an existing tachycardia. The 3/4 detection means that if any three out of the last four intervals are less than the acceleration detection window (225ms), then the x/y detection criteria are satisfied.
At 68, a decision is made to determine if the 3/4 detection criterion applies to the QRS com-plexes. If the 3/4 detection criterion is not met (69), control passes back to timeout at 77. If the time for therapy has not expired (78), it passes back to QRS detection at 63 and then either bac~ to timeout 77 if no QRS complexes are detected at this time, or back to the application of x/y detection at 67 if QRS
complexes are detected.
If at 70, the 3/4 detection criterion has been met, cardioversion or defibrillation therapy is applied at 74. It has been found safer and more ef-fective to use this acceleration detection combined with cardioversion or defibrillation therapy as shown in Fig. 6 than to wait until the end of ATP therapy and face the possibility of a degeneration to a very fast VT or a VF. After cardioversion or defibrilla-tion therapy at 75, the device returns to its normal ~ .
' ~ , , ,. '' . '~ : ~ :
-21- 2~3~
mode of operation at 61.
Although the invention has been described with reference to a particular embodiment, it is to be understood that this embodiment is merely illustrative of the application of the principles of the invention.
Hence numerous modifications may be made therein and other arrangements may be devised without departing from the spirit and scope of the invention.
Claims (48)
1. A dual chamber antitachycardia pacing device for the reversion of tachycardias in a heart comprising: means for detecting tachycardia, means for measuring cycle length of said tachycardia, means for determining a VA interval value less than or equal to the tachycardia cycle length, means for determining an initial value AV delay interval, pulse generating means responsive to said tachycardia detecting means for generating heart stimulating pulses for the atrium and for the ventricle, said pulse generating means in-cluding means for delivering a series of M pulse trains with each train consisting of a total of 2N
pacing pulses delivered in an alternating sequence to the ventricle and to the atrium, so that timing of said delivered pulses is in accordance with the values of the VA interval and the AV interval, whereby each train comprises the delivery of a pacing pulse to the atrium at the expiration of each of N VA delay inter-vals and a pacing pulse to the ventricle at the expi-ration of each of N AV delay intervals, and means for varying said AV delay interval from said programmed initial value at least once prior to completion of said series of M pulse trains.
pacing pulses delivered in an alternating sequence to the ventricle and to the atrium, so that timing of said delivered pulses is in accordance with the values of the VA interval and the AV interval, whereby each train comprises the delivery of a pacing pulse to the atrium at the expiration of each of N VA delay inter-vals and a pacing pulse to the ventricle at the expi-ration of each of N AV delay intervals, and means for varying said AV delay interval from said programmed initial value at least once prior to completion of said series of M pulse trains.
2. A dual chamber antitachycardia pacing device according to claim 1 further comprising means for confirming the presence of a tachycardia, wherein said pulse generating means is responsive to said confirming means.
3. A dual chamber antitachycardia pacing device according to claim 1 wherein said determined VA
interval is a percentage of the tachycardia cycle length.
interval is a percentage of the tachycardia cycle length.
4. The dual chamber antitachycardia pacing device according to claim 3 wherein said percentage of the tachycardia cycle length is in the range of thirty to one hundred percent.
5. A dual chamber antitachycardia pacing device according to claim 1 further comprising means for incrementing said initial value AV delay interval at least once prior to said completion of said series of pulse trains to a final value AV delay interval.
6. A dual chamber antitachycardia pacing device according to claim 5 further comprising means for storing an average AV delay during previous sinus rhythm, wherein said final value AV delay interval is a function of and equal to or less than one hundred percent of the previous stored average AV delay during sinus rhythm.
7. A dual chamber antitachycardia pacing device according to claim 1 including means for pro-viding dual chamber overdrive pacing at the completion of said M trains of pulses.
8. A dual chamber antitachycardia pacing device according to claim 7 further comprising means for programming a duration of said dual chamber overdrive pacing.
9. A dual chamber antitachycardia pacing device according to claim 7 further comprising means for storing an average AV delay during previous sinus rhythm, wherein said overdrive pacing includes an AV
delay interval which is a function of and less than or equal to one hundred percent of the previous stored average AV delay during sinus rhythm.
delay interval which is a function of and less than or equal to one hundred percent of the previous stored average AV delay during sinus rhythm.
10. A dual chamber antitachycardia pacing device according to claim 7 further comprising means for storing an average AV delay during previous sinus rhythm, wherein said dual chamber overdrive pacing includes a VA interval which is a function of and less than or equal to one hundred percent of the previous stored average VA delay interval during sinus rhythm.
11. A dual chamber antitachycardia pacing device according to claim 1 wherein said determined VA
interval remains fixed during said series of M trains.
interval remains fixed during said series of M trains.
12. A dual chamber antitachycardia pacing device according to claim 1 further comprising means for varying said determined VA interval during the series of M trains.
13. A dual chamber antitachycardia pacing device according to claim 1 wherein said initial value AV delay interval is less than 2Oms.
14. A dual chamber antitachycardia pacing device according to claim 1 wherein said initial value AV delay interval is less than or equal to 60ms.
15. A dual chamber antitachycardia pacing device according to claim 1 wherein N is fixed during said series of M trains.
16. A dual chamber antitachycardia pacing device according to claim 1 further comprising means for varying N during said series of M trains.
17. A dual chamber antitachycardia pacing device according to claim 16 wherein N is between 1 and 10.
18. A dual chamber antitachycardia pacing device according to claim 15 wherein N is between 1 and 10.
19. A dual chamber antitachycardia pacing device according to claim 1 wherein M is between 1 and 100 .
20. A dual chamber antitachycardia pacing device according to claim 1 in combination with an implantable pacemaker cardioverter/defibrillator device.
21. A dual chamber antitachycardia pacing device according to claim 20 wherein said pacemaker includes at least one of single chamber and dual chamber bradycardia pacing.
22. A dual chamber antitachycardia pacing device according to claim 1 wherein said device includes means for sensing inherent QRS complexes during delivery of said trains of pacing pulses, means for determining an acceleration detection cycle length value less than said tachycardia cycle length, means for measuring the cycle lengths of said sensed QRS
complexes, and means for delivering at least one of cardioversion and defibrillation therapy when a programmed number of said cycle lengths of said sensed QRS complexes are less than said acceleration detection cycle length.
complexes, and means for delivering at least one of cardioversion and defibrillation therapy when a programmed number of said cycle lengths of said sensed QRS complexes are less than said acceleration detection cycle length.
23. The dual chamber antitachycardia pacing device according to claim 1 wherein said means for determining an initial value AV delay interval includes programming means for programming said interval.
24. A method of antitachycardia pacing in a dual chamber pacing device comprising the steps of:
detecting a tachycardia, measuring cycle length of the tachycardia, determining a VA interval value less than or equal to the tachycardia cycle length, determining an initial value of the AV delay interval, delivering a pulse to the ventricle, delivering a pulse to the atrium at the expiration of said determined VA interval value, delivering a pulse to the ventricle at the expiration of said AV interval value, repeating pulse delivery to the atrium and the ventricle until the expiration of N VA intervals and N AV intervals thereby completing a first train of pulses, delivering a series of M trains of pulses similar to said first train of pulses, varying said AV delay interval value from the initial value at least once prior to the completion of said series of M trains of pulses.
detecting a tachycardia, measuring cycle length of the tachycardia, determining a VA interval value less than or equal to the tachycardia cycle length, determining an initial value of the AV delay interval, delivering a pulse to the ventricle, delivering a pulse to the atrium at the expiration of said determined VA interval value, delivering a pulse to the ventricle at the expiration of said AV interval value, repeating pulse delivery to the atrium and the ventricle until the expiration of N VA intervals and N AV intervals thereby completing a first train of pulses, delivering a series of M trains of pulses similar to said first train of pulses, varying said AV delay interval value from the initial value at least once prior to the completion of said series of M trains of pulses.
25. The method of antitachycardia pacing in a dual chamber pacing device according to claim 24 further comprising the step of confirming the presence of tachycardia prior to commencing antitachycardia pacing.
26. The method of antitachycardia pacing in a dual chamber pacing device according to claim 24 wherein said initial value of the AV delay interval is determined by programming.
27. The method of antitachycardia pacing in a dual chamber pacing device according to claim 24 wherein said determined VA interval is a percentage of the tachycardia cycle length.
28. The method of antitachycardia pacing in a dual chamber pacing device according to claim 27 wherein said percentage is in the range of fifty to one hundred percent.
29. A method of antitachycardia pacing in a dual chamber pacing device according to claim 24 wherein said initial value AV delay interval is incremented at least once prior to said completion of trains to a final value AV delay interval.
30. A method of antitachycardia pacing in a dual chamber pacing device according to claim 29 further comprising the step of storing a previous average AV delay interval during sinus rhythm, wherein said final value AV delay interval is a function of and less than or equal to one hundred percent of the previous stored average AV delay during sinus rhythm.
31. A method of antitachycardia pacing in a dual chamber pacing device according to claim 29 further comprising the step of providing dual chamber overdrive pacing at the completion of said M trains of pulses.
32. A method of antitachycardia pacing in a dual chamber pacing device according to claim 31 further comprising the step of programming a duration of said dual chamber overdrive pacing.
33. A method of antitachycardia pacing in a dual chamber pacing device according to claim 31 further comprising the step of storing a previous average AV delay interval during sinus rhythm wherein said dual chamber overdrive pacing includes an AV
delay interval which is a function of and less than or equal to one hundred percent of the previous stored average AV delay during sinus rhythm.
delay interval which is a function of and less than or equal to one hundred percent of the previous stored average AV delay during sinus rhythm.
34. A method of antitachycardia pacing in a dual chamber pacing device according to claim 31 further comprising the step of storing a previous average AV delay interval during sinus rhythm wherein said dual chamber overdrive pacing includes a VA
interval which is a function of and less than or equal to one hundred percent of the previous stored average VA delay interval during sinus rhythm.
interval which is a function of and less than or equal to one hundred percent of the previous stored average VA delay interval during sinus rhythm.
35. A method of antitachycardia pacing in a dual chamber pacing device according to claim 24 wherein said determined VA interval remains fixed during said series of M trains.
36. A method of antitachycardia pacing in a dual chamber pacing device according to claim 24 further comprising varying said VA interval during said series of M trains.
37. A method of antitachycardia pacing in a dual chamber pacing device according to claim 24 wherein said initial value AV delay interval is less than 2Oms.
38. A method of antitachycardia pacing in a dual chamber pacing device according to claim 24 wherein said initial value AV delay interval is less than or equal to 60ms.
39. A method of antitachycardia pacing in a dual chamber pacing device according to claim 24 wherein N is fixed during said series of M trains.
40. A method of antitachycardia pacing in a dual chamber pacing device according to claim 24 further comprising varying N during said series of M
trains.
trains.
41. A method of antitachycardia pacing in a dual chamber pacing device according to claim 40 wherein N is between 1 and 10.
42. A method of antitachycardia pacing in a dual chamber pacing device according to claim 39 wherein N is between 1 and 10.
43. A method of antitachycardia pacing in a dual chamber pacing device according to claim 24 wherein M is between 1 and 100.
44. A method of antitachycardia pacing in a dual chamber pacing device according to claim 24 further comprising performing at least one of cardioversion and defibrillation.
45. A method of antitachycardia pacing in a dual chamber antitachycardia pacing device according to claim 44 further comprising providing at least one of single chamber or dual chamber bradycardia pacing.
46. A method of antitachycardia pacing in a dual chamber antitachycardia pacing device according to claim 44 further comprising the steps of sensing inherent QRS complexes during the delivery of said trains of pacing pulses, determining an acceleration detection cycle length value less than said tachycardia cycle length, measuring cycle lengths of said sensed QRS complexes, and delivering at least one of cardioversion and defibrillation therapy when a programmed number of said cycle lengths of said sensed QRS complexes are less than said acceleration detection cycle length.
47. A dual chamber antitachycardia pacing device for the reversion of tachycardias comprising:
means for detecting tachycardia, means for measuring cycle length of said tachycardia, pulse generating means responsive to said tachycardia detecting means for generating heart stimulating pulses for the atrium and for the ventricle, said pulse generating means in-cluding means for delivering a series of pacing pulse trains, means for sensing inherent QRS complexes during delivery of said trains of pacing pulses, means for determining an acceleration detection cycle length value less than said tachycardia cycle length, means for measuring cycle lengths of said sensed QRS
complexes, and means for delivering at least one of cardioversion and defibrillation therapy when a number of said cycle lengths of said sensed QRS complexes are less than said acceleration detection cycle length.
means for detecting tachycardia, means for measuring cycle length of said tachycardia, pulse generating means responsive to said tachycardia detecting means for generating heart stimulating pulses for the atrium and for the ventricle, said pulse generating means in-cluding means for delivering a series of pacing pulse trains, means for sensing inherent QRS complexes during delivery of said trains of pacing pulses, means for determining an acceleration detection cycle length value less than said tachycardia cycle length, means for measuring cycle lengths of said sensed QRS
complexes, and means for delivering at least one of cardioversion and defibrillation therapy when a number of said cycle lengths of said sensed QRS complexes are less than said acceleration detection cycle length.
48. A method of antitachycardia pacing in a dual chamber pacing device comprising the steps of:
detecting a tachycardia, measuring cycle length of the tachycardia, delivering trains of antitachycardia pacing pulses to the atrium and to the ventricle, sensing inherent QRS complexes during the delivery of said trains of pacing pulses, determining an acceleration detection cycle length value less than said tachycardia cycle length, measuring cycle lengths of said sensed QRS complexes, and delivering at least one of cardioversion and defibrillation therapy when a number of said cycle lengths of said sensed QRS
complexes are less than said acceleration detection cycle length.
detecting a tachycardia, measuring cycle length of the tachycardia, delivering trains of antitachycardia pacing pulses to the atrium and to the ventricle, sensing inherent QRS complexes during the delivery of said trains of pacing pulses, determining an acceleration detection cycle length value less than said tachycardia cycle length, measuring cycle lengths of said sensed QRS complexes, and delivering at least one of cardioversion and defibrillation therapy when a number of said cycle lengths of said sensed QRS
complexes are less than said acceleration detection cycle length.
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|---|---|---|---|
| US462,499 | 1990-01-05 | ||
| US07/462,499 US4998974A (en) | 1990-01-05 | 1990-01-05 | Apparatus and method for antitachycardia pacing in dual chamber arrhythmia control system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2031854A1 true CA2031854A1 (en) | 1991-07-06 |
Family
ID=23836647
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002031854A Abandoned CA2031854A1 (en) | 1990-01-05 | 1990-12-10 | Apparatus and method for antitachycardia pacing in dual chamber arrhythmia control system |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4998974A (en) |
| EP (1) | EP0436517B1 (en) |
| JP (1) | JPH03242155A (en) |
| AU (1) | AU6824990A (en) |
| CA (1) | CA2031854A1 (en) |
| DE (1) | DE69127984T2 (en) |
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| EP2367596A1 (en) * | 2008-10-31 | 2011-09-28 | Medtronic, Inc. | Shunt-current reduction housing for an implantable therapy system |
| US8260412B2 (en) | 2008-10-31 | 2012-09-04 | Medtronic, Inc. | Implantable medical device crosstalk evaluation and mitigation |
| EP4282466A3 (en) | 2014-04-15 | 2024-01-31 | Cardiac Pacemakers, Inc. | Pacing device with autonomous anti-tachycardia pacing |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3857398A (en) * | 1971-12-13 | 1974-12-31 | L Rubin | Electrical cardiac defibrillator |
| GB1493353A (en) * | 1973-11-21 | 1977-11-30 | Devices Implants Ltd | Device for terminating tachycardia |
| US4108148A (en) * | 1976-11-03 | 1978-08-22 | Sheldon Thaler | Pacer with automatically variable A-V interval |
| DE3110014A1 (en) * | 1980-05-19 | 1982-03-25 | Telectronics Pty. Ltd., Lane Cove, New South Wales | EXTERNALLY RESETTABLE TACHYCARDY REGULATOR PACEMAKER |
| US4390021A (en) * | 1981-03-23 | 1983-06-28 | Telectronics Pty. Ltd. | Two pulse tachycardia control pacer |
| US4398536A (en) * | 1981-07-17 | 1983-08-16 | Telectronics Pty. Ltd. | Scanning burst tachycardia control pacer |
| US4406287A (en) * | 1981-07-17 | 1983-09-27 | Telectronics Pty. Ltd. | Variable length scanning burst tachycardia control pacer |
| DE3207006A1 (en) * | 1982-02-26 | 1983-09-08 | Siemens AG, 1000 Berlin und 8000 München | AV SEQUENTIAL HEART PACEMAKER |
| US4429697A (en) * | 1982-04-12 | 1984-02-07 | Telectronics Pty. Ltd. | Dual chamber heart pacer with improved ventricular rate control |
| DE3382604T2 (en) * | 1982-11-22 | 1993-01-07 | Intermedics Inc | HEART PACEMAKER. |
| FR2544988B1 (en) * | 1983-04-29 | 1986-10-10 | Ela Medical Sa | AURICULO-VENTRICULAR CARDIAC STIMULATOR |
| US4587970A (en) * | 1985-01-22 | 1986-05-13 | Telectronics N.V. | Tachycardia reversion pacer |
-
1990
- 1990-01-05 US US07/462,499 patent/US4998974A/en not_active Expired - Lifetime
- 1990-11-30 JP JP2336972A patent/JPH03242155A/en active Pending
- 1990-12-10 CA CA002031854A patent/CA2031854A1/en not_active Abandoned
- 1990-12-19 AU AU68249/90A patent/AU6824990A/en not_active Abandoned
-
1991
- 1991-01-07 EP EP91300085A patent/EP0436517B1/en not_active Expired - Lifetime
- 1991-01-07 DE DE69127984T patent/DE69127984T2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DE69127984T2 (en) | 1998-03-12 |
| US4998974A (en) | 1991-03-12 |
| EP0436517A3 (en) | 1992-12-30 |
| EP0436517A2 (en) | 1991-07-10 |
| EP0436517B1 (en) | 1997-10-22 |
| DE69127984D1 (en) | 1997-11-27 |
| JPH03242155A (en) | 1991-10-29 |
| AU6824990A (en) | 1991-07-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |