Abstract: An intravenous lead for use with a cardiac device implantable beneath the skin of a patient provides positive fixation for the lead when implanted in an artery or vein of the heart. The lead includes a lead body adapted to be fed into an artery or a vein of the heart of a patient and at least one electrode carried by the lead body and adapted to be coupled to the implantable cardiac device. The lead body includes a preformed section having a resiliently coiled configuration. The coiled section makes substantially continuous surface contact with inner wall surfaces of the artery or vein after the lead is implanted within the artery or vein for providing positive fixation of the lead.

Abstract: An implantable atrial defibrillator provides a pulse of defibrillating electrical energy to the atria of the heart in synchronism with sensed R waves in response to non-coincident sensing of an R wave at first and second areas of the heart. The defibrillating pulse is provided after a predetermined number of consecutive R waves are non-coincidently sensed to assure reliable synchronization. The atrial defibrillator is also operational in a marker mode wherein a number of synchronization marker pulses are delivered to the heart for detection on an externally generated electrocardiogram. The atrial fibrillation detector of the defibrillator is normally disabled and is activated when the sensed ventricular activity indicates a probability of atrial fibrillation to conserve a depletable power source.

Abstract: An implantable atrial defibrillator and method provides cardioverting electrical energy to the atria of a human heart in need of cardioversion. The atrial defibrillator includes a first detector for detecting R waves of the heart, a second detector for detecting T waves of the heart, and a third detector for detecting atrial activity of the heart. An atrial fibrillation detector is responsive to the third detector for determining when the atria of the heart are in need of cardioversion. A cardioverting stage applies the cardioverting electrical energy to the atria of the heart when the atria of the heart are in need of cardioversion, after the second detector detects a T wave, and in timed relation to an R wave detected by the first detector after the detected T wave is completed.

Abstract: An atrial defibrillator reliably detects a depolarization activation wave of the heart and delivers cardioverting electrical energy to the atria of the heart in synchronism with a detected depolarization activation wave. The atrial defibrillator includes a first sensor for producing a first electrical output having a duration substantially equal to the duration of the depolarization activation wave sensed between a first pair of spaced apart locations of the heart. The atrial defibrillator further includes a second sensor for producing a second electrical output having a duration substantially equal to the duration of the depolarization activation wave sensed between a second pair of spaced apart locations of the heart. The spacing between the second pair of locations is greater than the spacing between the first pair of locations.

Abstract: A telemetry system and method of monitoring cardiac activity or providing therapy to the heart for an implantable cardiac device. The system includes a receiver and a transmitter in an external programmer and a receiver section and transmitter section in the cardiac device. The receiver section and the transmitter section of the cardiac device generally remain in a de-energized state. The receiver section is energized at spaced apart time intervals to detect an initiation signal transmitted by the external programmer. If the initiation signal is detected, the receiver section and the transmitter section of the cardiac device are fully activated. The external programmer includes a signal strength indicating means for providing an indication of received signal strength which the user can use to position the receiver and transmitter in the external programmer for optimum received signal strength. An antenna is disposed in the header of the implanted device to facilitate communication at high speed.

Abstract: An implantable atrial defibrillator provides cardioverting electrical energy to the atria of a patient's heart in need of cardioversion and a precardioversion warning to the patient. The atrial defibrillator includes a detector for detecting atrial activity of the patient's heart, and an atrial fibrillation detector responsive to the atrial activity detector for determining when the atria of the patient's heart are in need of cardioversion. A cardioverter responsive to the atrial fibrillation detector, applies warning electrical energy to the atria of the patient's heart when the atria are in need of cardioversion and thereafter applies cardioverting electrical energy to the atria. The warning electrical energy is of insufficient quantity to intentionally cardiovert the atria but of sufficient quantity so as to be discernable by the patient.

Abstract: An implantable cardiac monitor is arranged for detecting both arrhythmias and ischemia of the human heart. The monitor includes subcutaneous electrodes for establishing electrical contact with the heart and a sense amplifier coupled to each electrode for generating an electrocardiogram of a heart beat sensed at each of the electrodes. The electrocardiograms are digitized and the digital samples thereof are stored in a memory. A microprocessor processes the digital samples of the electrocardiograms and generates characterizing data indicative of the physiology of the heart. The cardiac monitor includes telemetry to permit the cardiac data to be interrogated externally of the patient for obtaining the generated cardiac data indicative of arrhythmic and ischemic episodes.

Abstract: A pulse generator for use in a defibrillator provides cardioverting electrical energy to a heart through at least one lead having a pair of electrodes associated with the heart. Electrical energy is applied to the heart with a biphasic waveform having a first cardioverting phase and a second cardioverting phase. A crosspoint switch selectively couples a storage capacitor to the lead means. A master switch decouples the crosspoint switch from the storage capacitor while the crosspoint switch connections are changed between the first cardioverting phase and the second cardioverting phase. A control circuit provides independent control of the duration of both the first and second cardioverting phases.

Abstract: An implantable atrial defibrillator provides a pulse of defibrillating electrical energy to the atria of the heart in synchronism with sensed R waves in response to non-coincident sensing of an R wave at first and second areas of the heart. The defibrillating pulse is provided after a predetermined number of consecutive R waves are non-coincidently sensed to assure reliable synchronization. The atrial defibrillator is also operational in a marker mode wherein a number of synchronization marker pulses are delivered to the heart for detection on an externally generated electrocardiogram. The atrial fibrillation detector of the defibrillator is normally disabled and is activated when the sensed ventricular activity indicates a probability of atrial fibrillation to conserve a depletable power source. An endocardial lead is also described which ensures that the delivered atrial defibrillating electrical energy is substantially confined to the atria of the heart.

Abstract: An arrangement and method facilitates the implantation of an electrode of an endocardial or intravenous lead at an implantation site within the heart of a human. The arrangement includes a guide wire which is formed of flexible material and which may be fed along a predetermined path which includes the implantation site. The arrangement further includes a lead formed of flexible material which includes a proximal end, a distal end, and an electrode to be implanted. The lead further includes an integrally formed follower which slidingly engages the guide wire to permit the lead to be guided along the predetermined path until the electrode to be implanted resides at its implantation site. Thereafter, the guide wire is retracted along the predetermined path to cause the electrode to remain at its implantation site.

Abstract: An implantable atrial defibrillator provides a pulse of defibrillating electrical energy to the atria of the heart in synchronism with sensed R waves in response to non-coincident sensing of an R wave at first and second areas of the heart. The defibrillating pulse is provided after a predetermined number of consecutive R waves are non-coincidently sensed to assure reliable synchronization. The atrial defibrillator is also operational in a marker mode wherein a number of synchronization marker pulses are delivered to the heart for detection on an externally generated electrocardiogram. The atrial fibrillation detector of the defibrillator is normally disabled and is activated when the sensed ventricular activity indicates a probability of atrial fibrillation to conserve a depletable power source. An endocardial lead is also described which ensures that the delivered atrial defibrillating electrical energy is substantially confined to the atria of the heart.

Abstract: An implantable atrial defibrillator provides cardioverting electrical energy to the atria of a human heart in need of cardioversion. The atrial defibrillator includes a first detector for detecting atrial activity of the heart and an atrial fibrillation detector responsive to the first detector for determining when the atria of the heart are in need of cardioversion. The atrial defibrillator further includes a pacing output circuit responsive to the atrial fibrillation detector for pacing the ventricles of the heart at a pacing rate when the atria of the heart are in need of cardioversion and a cardioverter stage for applying the cardioverting electrical energy to the atria of the heart after the pacing output circuit has paced the ventricles for a predetermined number of cardiac cycles. The pacing output circuit stabilizes the cardiac rate of the heart prior to the application of the cardioverting electrical energy.

Abstract: An implantable atrial defibrillator provides a pulse of defibrillating electrical energy to the atria of the heart in synchronism with sensed R waves in response to non-coincident sensing of an R wave at first and second areas of the heart. The defibrillating pulse is provided after a predetermined number of consecutive R waves are non-coincidently sensed to assure reliable synchronization. The atrial defibrillator is also operational in a marker mode wherein a number of synchronization marker pulses are delivered to the heart for detection on an externally generated electrocardiogram. The atrial fibrillation detector of the defibrillator is normally disabled and is activated when the sensed ventricular activity indicates a probability of atrial fibrillation to conserve a depletable power source. An endocardial lead is also described which ensures that the delivered atrial defibrillating electrical energy is substantially confined to the atria of the heart.

Abstract: An implantable atrial defibrillator provides cardioverting electrical energy to the atria of a human heart in need of cardioversion. The atrial defibrillator includes a first detector for detecting ventricular activations of the heart, a second detector for detecting atrial activity of the heart, and an atrial fibrillation detector responsive to the second detector for determining when the atria of the heart are in need of cardioversion. The atrial defibrillator further includes a cardioverter for applying the cardioverting electrical energy to the atria of the heart when the atria of the heart are in need of cardioversion, and a timer delay stage responsive to the first detector for causing the cardioverter to apply the cardioverting electrical energy to the atria of the heart a predetermined delay time after the first detector detects one of the ventricular activations and before the T wave of the heart immediately following the one of the ventricular activations.

Abstract: An implantable atrial defibrillator applies cardioverting electrical energy to the atria of a human heart in need of cardioversion. The atrial defibrillator includes a first detector for sensing atrial activity of the heart, an atrial fibrillation detector responsive to the first detector for determining when the atria of the heart are in need of cardioversion and a second detector for detecting ventricular activations of the heart. The atrial defibrillator further includes a cardioverter for applying cardioverting electrical energy to the atria of the heart when the atria of the heart are in need of cardioversion and is responsive to the second detector for applying the cardioverting electrical energy to the atria of the heart in predetermined time relation to a detected ventricular activation. The detection of atrial activity of the heart is interrupted when a ventricular activation of the heart is detected by the second detector.

Abstract: An implantable atrial defibrillator applies cardioverting electrical energy to the atria of a human heart in need of cardioversion and thereafter gradually returns the cardiac rate of the heart to a normal cardiac rate. The atrial defibrillator includes a first detector for detecting atrial activity of the heart, and an atrial fibrillation detector, responsive to said first detector, for determining when the atria of the heart are in need of cardioversion. The atrial defibrillator further includes a cardioverter responsive to the atrial fibrillation detector for applying the cardioverting electrical energy to the atria of the heart when the atria are in need of cardioversion, and a pacing output for pacing the ventricles of the heart at a decreasing cardiac rate from a base rate to a final rate lower than the base rate after the atria of the heart are successfully cardioverted.

Abstract: A pulse generator for use in implantable atrial defibrillator provides cardiovertinq electrical energy to the atria of a heart through at least one lead having a pair of electrodes associated with the atria of the heart. The pulse generator includes a depletable, low voltage, power source such as a battery. A charging circuit coupled to the battery includes a flyback transformer for converting the battery voltage to low duty cycle pulsating high voltage electrical energy to store the high voltage electrical energy in a storage capacitor coupled to the charging circuit. A crosspoint switch selectively couples the storage capacitor to the electrodes for applying a portion of the stored electrical energy to the atria of the heart for cardioverting the atria of the heart.

Abstract: An implantable atrial defibrillator provides cardioverting electrical energy to the atria of a human heart in need of cardioversion. The atrial defibrillator includes a first detector for detecting ventricular activations of the heart, a second detector for detecting atrial activity of the heart, and an atrial fibrillation detector responsive to the second detector for determining when the atria of the heart are in need of cardioversion. The atrial defibrillator also includes a cardioverting stage for applying the cardioverting electrical energy to the atria of the heart when the atria of the heart are in need of cardioversion and when the time between immediately successive ventricular activations is greater than a preselected minimum time interval.

Abstract: An implantable device prevents tachyarrhythmias of a human heart which has arrhythmogenic tissue such as a myocardial infarction site. The device includes a plurality of electrodes configured for electrical contact with the heart and for placement in proximity to the arrhythmogenic tissue and a sensor including a single sensing electrode for sensing electrical activations of one chamber of the heart. A pulse generator coupled to the plurality of electrodes and responsive to the sensor provides the plurality of electrodes with an electrical pulse during each sensed electrical activation.

Abstract: An implantable device assists in the diagnosis of myocardial ischemia of a human heart and includes a plurality of electrodes and a like plurality of sense amplifiers for generating an electrogram for each of the electrodes. A digital to analog converter reads the voltage magnitudes of the electrogram ST segments which are then stored in a memory. An implantable receiver/transmitter is arranged to transmit the magnitudes of the electrogram ST segments to a nonimplanted external receiver.