Abstract: An implantable atrial defibrillator includes at least one lead for sensing electrical activity of a heart, a synchronizing stage for providing a synchronizing signal upon detection of an R wave, a timer for timing time intervals between immediately successive R waves, and a cardiovertor for cardioverting the heart when a cardiac interval is greater than a determined minimum time interval and in timed relation to a synchronizing signal. The defibrillator further includes first and second R wave detection channels, the first R wave detection channel providing the synchronizing stage with specific R wave detection, and the second R wave detection channel providing the timer with sensitive R wave detection.

Abstract: An atrial defibrillator applies cardioverting electrical energy to the atria of a heart when in need of cardioversion. The atrial defibrillator includes an atrial fibrillation detector for determining if the atria of a heart are in need of cardioversion, and a therapy sequencer for performing a therapy sequence to apply cardioverting electrical energy to the atria when the atria are in need of cardioversion. The therapy sequence is terminated when the atrial fibrillation detector fails at least twice in succession to determine that the atria are in need of cardioversion. As a result, a greater atrial fibrillation detection sensitivity is employed for terminating a therapy sequence as is employed for initiating the therapy sequence.

Abstract: An atrial cardiovertor/defibrillator provides therapy to the atria corresponding to the type of atrial arrhythmia occurring in the atria of the heart. The atrial cardiovertor/defibrillator includes a memory for storing respective different criteria for each of different types of atrial arrhythmia, a sensor for sensing activity of at least one of the atria of the heart to provide an electrogram signal, and a cardiovertor for providing a corresponding therapy to the heart for each of the different types of atrial arrhythmia. The cardiovertor/defibrillator further includes an atrial arrhythmia detector responsive to the electrogram signal and the stored criteria for identifying one of the types of atrial arrhythmia to cause the cardiovertor to provide therapy to the heart corresponding to the identified atrial arrhythmia.

Abstract: An atrial defibrillator coordinates atrial cardioversion with ischemia detection. The defibrillator includes a plurality of sense amplifiers for sensing electrical activity of a heart. An ischemia detector is responsive to the sensed electrical activity of the heart for detecting ischemia of the heart. An atrial fibrillation detector is responsive to the sensed electrical activity of the heart for determining if the atria are in need of cardioversion, and a cardiovertor applies cardioverting electrical energy to the atria of the heart if the atria of the heart are in need of cardioversion and if the ischemia detector fails to detect ischemia of the heart.

Abstract: An atrial defibrillator applies cardioverting electrical energy to the atria of a human heart in need of cardioversion. The defibrillator includes an electrode pair and a sense amplifier associated with the atria of the heart for sensing electrical activity of the heart during a plurality of cardiac cycles to provide a cardiac signal. A detector is responsive to the cardiac signal for detecting cardiac events. During each cardiac cycle of the plurality of cardiac cycles, a time for counting is established wherein each time for counting has a total duration less than the duration of its corresponding cardiac cycle. A counter counts the cardiac events detected by the detector during the time for counting of the plurality of cardiac cycles to provide a cardiac event count. A comparator compares the cardiac event count to a predetermined cardiac event count.

Abstract: An implantable atrial defibrillator applies cardioverting electrical energy to the atria of a human heart in response to detection of an atrial fibrillation episode and stores selected data associated with the detected atrial fibrillation episode. The atrial defibrillator includes a cardiovertor which provides successive applications of cardioverting electrical energy to the atria of the heart until one of the pulses successfully cardioverts the atria. A memory system stores selected heart activity data in connection with the detected episode including heart activity data related to initial detection of the atrial fibrillation episode and heart activity data occurring from before and until after the application of the cardioverting electrical energy which successfully cardioverts the atria of the heart.

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 intravenous lead for use with a cardiac device for implantation in the coronary sinus or the coronary sinus and great cardiac vein of the heart provides positive fixation for the lead when implanted in the coronary sinus or the coronary sinus and great vein of the heart. The lead includes a lead body adapted to be fed into the coronary sinus and great 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 is a left-handed turned coiled section which provides superior positive fixation of the lead as compared to right-handed turned coiled sections for use in the coronary sinus and great cardiac vein.

Abstract: An implantable atrial defibrillator for applying cardioverting electrical energy to the atria of a human heart. The atrial defibrillator includes a first detector for sensing a depolarization activation wave at a first pair of locations of the heart and generating a first initiation signal and a second detector for sensing the depolarization activation wave between a second pair of locations of the heart and generating a second initiation signal. The atrial defibrillator also includes a timing circuit for timing the time between immediately successive depolarization activation waves of the heart in response to one of the first and the second initiation signals for commencing the timing. The atrial defibrillator also includes a cardioverting circuit 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 timer times a time greater than a predetermined time interval.

Abstract: An atrial defibrillator implantable beneath the skin of a patient includes an intervention sequencer for performing an intervention sequence. The intervention sequencer includes an atrial fibrillation detector for determining if atrial fibrillation is present in a patient's heart and a cardiovertor for applying cardioverting electrical energy to the atria of the patient's heart if the atrial fibrillation detector determines that atrial fibrillation is present. A sequence initiating stage includes a receiver for receiving a sequence command generated from external to the patient. The sequence initiating stage causes the intervention sequencer to perform the intervention sequence upon receipt of a sequence command.

Abstract: An implantable automatic atrial defibrillator powered by a depletable battery power source conserves battery power for extending the predicted life of the defibrillator by intermittently detecting for atrial fibrillation. The atrial defibrillator includes a real time clock which, at spaced apart predetermined times, causes heart activity data to be stored in a memory. Thereafter, a normally deactivated atrial fibrillation detector is activated for processing the stored data to detect for atrial fibrillation.

Abstract: An apparatus reliably detects a depolarization activation wave of the heart. The apparatus includes a sensor in electrical contact with the heart for sensing electrical activity of the heart and including an amplifier for amplifying the sensed electrical activity according to a variable gain and providing a signal corresponding to the depolarization activation wave. The apparatus further includes an output circuit coupled to the sensor for producing an electrical output corresponding to the depolarization activation wave sensed by the sensor when the signal exceeds a threshold. The apparatus still further includes a control circuit coupled to the sensor and the output circuit for varying at least one of the gain and the threshold to maintain a predetermined sense margin between the sensed electrical activity and the gain and the threshold.

Abstract: An implantable atrial defibrillator delays therapy intervention for a delay time period after initial detection of fibrillation to provide the atria with an opportunity to spontaneously revert to normal sinus rhythm before cardioversion is attempted. A timer times the delay time period responsive to the first initial detection of fibrillation by a fibrillation detector. After timer time-out, the fibrillation detector redetects for atrial fibrillation. If the atria are still in fibrillation, a cardiovertor cardioverts the atria. If the atria are not in fibrillation, cardioverting therapy is withheld.

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: A cardiac monitor which is fully implantable beneath the skin of a patient monitors heart rate variability of a human heart. The heart rate monitor includes at least one electrode which establishes electrical contact with the heart. During a heart monitoring period, time intervals between adjacent heart beats are determined for generating heart rate data. The heart rate data is stored in a memory which is accessed after the completion of the heart monitoring period for generating a heart rate variability factor. The heart rate variability factor is stored in memory for later transmission to a nonimplanted external receiver.

Abstract: A catheter insertable into a body provides for both sensing electrical activity of the heart at localized locations of the heart and defibrillating the heart when defibrillation is required. The catheter includes a plurality of connectors at the proximal end and a plurality of electrodes disposed along the catheter at the distal end. The plurality of electrodes includes a first plurality of electrodes and a second plurality of electrodes. The first plurality of electrodes are coupled together and to a given one of the plurality of connectors. Each of the second plurality of electrodes is coupled to a respective different one of the plurality of connectors. The first plurality of electrodes provide for defibrillating the heart and the second plurality of electrodes provide for sensing electrical activity of the heart at localized locations of the heart.

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: A post-surgical cardioverting system and method applies cardioverting electrical energy to the atria of the heart of a post-surgical heart patient. The system includes a first lead including a first elongated electrode having a proximal end and a distal end, a second lead including a second elongated electrode having a proximal end and a distal end, and sutures for releasably anchoring the distal ends of the first and second electrodes to the pericardium and disposing the first and second electrodes along the pericardium overlying the right and left atria respectively. A non-implantable cardiovertor is coupled to the first and second leads for applying the cardioverting electrical energy to the first and second electrodes. When cardioversion is no longer required, the first and second leads may be pulled out of the patient's chest.

Abstract: An implantable atrial defibrillator cardioverts the atria of a patient's heart and determines the quantity of cardioverting electrical energy required for cardioverting the atria of the patient. The atrial defibrillator includes a detector for detecting atrial activity of the heart and an atrial fibrillation detector for determining when the atria of the heart are in fibrillation. A delivery stage is selectively operable in a test mode for applying fibrillation inducing electrical energy to the atria when the atria are not in fibrillation for inducing fibrillation. When fibrillation is induced, the delivery stage repeatedly applies test cardioversion electrical energy to the atria until the atria are cardioverted. Thereafter, a value indicative of the quantity of the test cardioversion energy last applied to the atria is stored for future reference when the atrial defibrillator is in a normal operating mode.

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.