Abstract: A method and apparatus for treating fibrillation, particularly atrial fibrillation. In response to detection of fibrillation, a series of low energy pulse bursts is delivered, separated by defined inter-burst intervals, and including bursts unsynchronized to heart depolarizations. Detection of termination of fibrillation during inter-burst intervals results in cancellation of further pulse bursts to prevent reinduction of fibrillation.

Abstract: A method and apparatus for treating atrial tachyarrhythmias, particularly atrial fibrillation. High energy pulses are delivered between electrodes located in the right atrium/SVC, the right ventricle and the coronary sinus/great vein, with the right ventricular and coronary sinus/great vein electrodes connected in common. Optionally a subcutaneous electrode, preferably located in the left pectoral area may also be employed, coupled in common to the right atrial/SVC electrode.

Abstract: A device for controlling the duration of A-V conduction intervals ia a patient's heart. Stimulation of the AV nodal fat pad is employed to maintain the durations of the A-V conduction intervals within a desired interval range, which may vary as a function of sensed heart rate or other physiologic parameter. AV nodal fat pad stimulation may also be triggered in response to defined heart rhythms such as a rapid rate or the occurrence of PVC's, to terminate or prevent induction of arrhythmias.

Abstract: A defibrillation pulse generator and lead system particularly adapted to allow for implant in a single incision and subcutaneous pocket. The electrode system consists of a right ventricular electrode and a combined, subcutaneously implanted pulse generator housing and flexible periprerally extending electrode. The flexible electrode extends in a generally co-planar relation with respect to the major surfaces of the device housing and may comprise a plurality of electrode segments electrically connected in common with the device housing and distributed over a flexible electrode pad.

Abstract: A device for controlling the duration of A-V conduction intervals in a patient's heart. Stimulation of the AV nodal fat pad is employed to maintain the durations of the A-V conduction intervals within a desired interval range, which may vary as a function of sensed heart rate or other physiologic parameter. AV nodal fat pad stimulation may also be triggered in response to defined heart rhythms such as a rapid rate or the occurrence of PVC's, to terminate or prevent induction of arrhythmias.

Abstract: A stimulator for applying stimulus pulses to the AV nodal fat pad in response to sensed atrial rate exceeding a predetermined rate, in order to reduce the ventricular rate. The device also includes a cardiac pacemaker which serves to pace the ventricle in the event that the ventricular rate is lowered below a pacing rate, and provides for feedback control of the stimulus parameters applied to the AV nodal fat pad, as a function of the determined effect of the stimulus pulses on the ventricular rate.

Abstract: A defibrillation lead provided with an elongated defibrillation electrode and a bipolar electrode pair for cardiac pacing and sensing. The cardiac pacing and sensing electrodes comprise an extendable helical electrode and a ring or ring tip electrode located on or adjacent the distal end of the lead body. Inter-electrode separation for pacing and sensing is provided by means of insulation applied to the helical electrode, leaving only the tip portion exposed. The overall configuration of the lead allows the defibrillation electrode to be located very close to the distal end of the lead body, while preserving the ability to employ a bipolar electrode pair for cardiac pacing and sensing.

Abstract: A combined pacing and cardioversion lead system with internal electrical switching components for unipolar or bipolar sensing of electrograms, pacing at normal pacing voltages and cardioversion or defibrillation. In bipolar embodiments, an indifferent electrode, closely spaced to a sensing and pacing electrode, is coupled in common through the integral switching circuitry to a large surface area cardioversion electrode. In these embodiments, pacing and sensing is accomplished through a pair of conductors extending through the lead system to the closely spaced active and indifferent electrode pair. When cardioversion energy is applied to the indifferent electrode, the cardioversion energy is also directed to the cardioversion electrode through operation of the switching circuitry in response to the magnitude of the applied cardioversion pulse. In unipolar embodiments, a distal sensing and pacing electrode is coupled through integral switching circuitry to a large surface area cardioversion electrode.

Abstract: A method and apparatus for providing an enhanced capability of detecting and gathering electrical cardiac signals via an array of relatively closely spaced subcutaneous electrodes (located on the body of an implanted device) which may be employed with suitable switching circuits, signal processors, and memory to process the electrical cardiac signals between any selected pair or pairs of the electrode array in order to provide a leadless, orientation insensitive means for receiving the electrical signal from the heart.

Abstract: An implantable cardioverter including two electrodes for sensing depolarizations of a chamber of a patient's heart, one electrode providing a near field signal, one electrode providing a far field signal. The device defines a desired cardioversion pulse delivery time as a first time interval following the onset of the far field signal. The device measures a second time interval between the onset of the far field signal and the detection of the near field signal, and delivers the cardioversion pulse synchronized to the detection of the near field signal, using the first and second time intervals to define a synchronization interval following detection of the near field electrogram.

Abstract: A method and apparatus for performing dual chamber cardiac pacing and sensing with a single pace/sense electrode situated in the coronary sinus or deep cardiac vein of a patient's heart. The pace/sense electrode is disposed at the end of a transvenous lead which extends from an implanted pacemaker, through the patient's right atrium, the patient's coronary sinus, and into the deep cardiac vein. Electrical cardiac signals received by the pace/sense electrode are applied to the inputs of two sense amplifiers, with one the sense amplifiers having a lower sensitivity threshold and the other having a higher sensitivity threshold. Electrical cardiac signals which exceed the lower sensitivity threshold but not the higher sensitivity threshold are interpreted as corresponding to atrial events, while electrical cardiac signals which exceed both the lower and higher sensitivity thresholds are interpreted as corresponding to ventricular events.

Abstract: A method for discrimination between ventricular and supraventricular tachycardia and an apparatus for performing the method. In response to the detection of the occurrence of an tachycardia, stimulus pulses are delivered to one or both of the SA and AV nodal fat pads. The response of the heart rhythm to these stimulus pulses is monitored. Depending upon the change or lack of change in the heart rhythm, a diagnosis is made as to the origin of the tachycardia.

Abstract: An expandable electrode for location within a blood vessel or other tubular organ. The electrode takes the form of a hollow, tubular metal structure, expanded into contact with the inner walls of the tubular structure in which the electrode is to be located. Expansion of the electrode may take place by means of plastic deformation of the electrode, or the electrode may be fabricated such that it resiliently expands. The electrode is particularly adapted for location within arteries and veins, and in particular for use in the coronary sinus and great vein of the human heart.

Abstract: A cardioverter/pacemaker which provides improved accuracy of the timing of a cardioversion pulse relative to a cardiac depolarization. After detection of a tachyarrhythmia, the device overdrives the tachyarrhythmia with a series of high rate pacing pulses. Delivery of the cardioversion pulse is timed from the last in the series of pacing pulses. In some embodiments, detection of reliable capture by the pacing pulses is a prerequisite to cardioversion synchronized from the pacing pulses.

Abstract: An expandable electrode for location within a blood vessel or other tubular organ. The electrode takes the form of a hollow, tubular metal structure, expanded into contact with the inner walls of the tubular structure in which the electrode is to be located. Expansion of the electrode may take place by means of plastic deformation of the electrode, or the electrode may be fabricated such that it resiliently expands. The electrode is particularly adapted for location within arteries and veins, and in particular for use in the coronary sinus and great vein of the human heart.

Abstract: A method of cardioverting the atrium of a human heart, comprising insertion of first and second elongated electrodes tranvenously into the heart and associated vessels. One electrode is preferably located in the coronary sinus and great vein of the heart. The other electrode is preferably located in the vicinity of the atrium of the heart, spaced from the electrode located in the coronary sinus. In response to detection of fibrillation or in response to manual triggering, a defibrillation pulse is applied between the first and second electrodes to effect atrial cardioversion.

Abstract: An implantable transvenous defibrillation/cardioversion lead. The lead extends from a proximal end carrying electrical connectors to a bifurcated distal end. Distal to the bifurcation are a first, generally straight leg and a second, curved leg. In use, the distal end of the first, generally straight leg is located in the apex of the right ventricle and the distal end of the second, generally curved leg is located in the outflow tract from the right ventricle, with the point of bifurcation located approximately adjacent the tricuspid valve. Elongated coil electrodes are provided extending along the straight and curved legs, distal to the point of bifurcation of lead. The lead may be used in conjunction with a subcutaneous or othe additional defibrillation/cardioversion electrode.

Abstract: An automatic fibrillator for inclusion in an implantable defibrillator. Fibrillation induction takes place while the patient's heart is beating at a known rate, and the fibrillation inducing pulse is delivered at a time based on the expected or measured natural refractory period of the patient's heart, at the heart rate in effect during fibrillation induction. In its preferred embodiment, fibrillation induction takes place during overdrive pacing, and the timing of the pulse takes place using an overdrive pacing pulse as a time reference. The period between the pacing pulse and the fibrillation inducing pulse may be determined as a function of actual measurement of the patient's refractory period, either directory, or by means of measurement of the Q-T interval of the patient's heart.

Abstract: A method and apparatus for sensing in vivo blood pressure proportional to the left ventricular pressure for detecting ventricular tachyarrhythmias or the cardiovascular status in congestive heart failure, and/or for adjusting the rate of a pacemaker. A lead with a pressure sensor near its distal end is placed transvenously through the coronary sinus and located in the coronary vein. When in place, a bulge or an inflatable balloon proximal to the pressure sensor may be used to acutely occlude the coronary vein until the sensor fibroses in. The balloon may be reinflated prior to pressure measurements. The pressure that is sensed in that location is proportional to the left ventricular pressure. Values representing the left ventricular pulse, systolic and diastolic pressures, as well as the differentiated rate of change (i.e., dP/dt), gross rate of change (.DELTA.P/.DELTA.

Abstract: A non-invasive electrical stimulator for pacing the heart. The stimulator generates a ramped current waveform which reduces muscle stimulation and pain associated with external stimulation of the heart.