Abstract: A pacemaker which operates in an atrial synchronized modality when the sensed atrial rate is within a physiologic range and which paces at a sensor determined rate when the atrial rate is above or below the physiologic range.

Abstract: A muscle-powered pump to assist the natural heart is disclosed. The device comprises an oblate, spheroidal-shaped pumping chamber surrounded by innervated muscular tissue. The device may be coupled to the ventricle and descending aorta with valves and be stimulated in synchrony with the natural depolarization of the heart or the device may be inserted into the descending aorta and used as a counter pulsation device. In this application, the innervated muscle is stimulated after a brief delay from the natural cardiac depolarization.

Abstract: A method and apparatus for providing muscle stimulation in the field of Function Electrical Stimulation, particularly electrical stimulation to a muscle employed as a myocardial substitute. The Latissimus Dorsi muscular flap is divided into two parts to cover the surfaces of the heart and inserted into a thoracic cavity by means of a segmental resection of the second rib. After or before positioning the muscle in this fashion, first and second stimulating electrodes are threaded into the muscle at desired locations to effect contraction of the muscle around the heart upon application of electrical stimulating pulses between the two electrodes. Stimulating pulses having suitable parameters chosen to effect the desired functional contraction of the muscle are generated in synchrony with natural or stimulated heart contractions.

Abstract: Ventricular fibrillation and other tachyarrhythmias are controlled by delivery of two sequential impulses to two pairs of electrodes placed partially within or adjacent to the heart. One electrode pair is provided by an endocardial lead which includes a distal electrode adapted to reside in the apex of the right ventricle and a proximal electrode designed to lie in the superior vena cava. The second electrode pair comprises the distal electrode within the right ventricle and a further electrode lodged in or adjacent to the coronary sinus. The metal case of the implantable pulse generator which supplies pulses to the electrode pairs may be substituted for the coronary sinus electrode if the pulse generator is implanted above and to the left of the heart in the left pectoral region of the patient's body. Alternatively, a subcutaneous plate electrode may be substituted for the can, obviating the need for implanting the generator in the left pectoral region.

Abstract: A method of controlling cardiac ventricular fibrillation and other tachyarrhythmias. A catheter carrying a first and second electrode is located in the right ventricle such that the first electrode is located in the right ventricle and the second electrode is located in the superior vena cava. A third electrode is located either at the chest wall or at the abdominal cavity. The third electrode can be implanted subcutaneously in the left chest wall. It can also be located in the abdomen immediately beneath the diaphragm. It could also be implanted in the epigastric area overlying the superficial abdominal muscles and underneath the skin and fat. The second and third electrodes are sequentially paired and pulsed with the first electrode to control ventricular fibrillation and other tachyarrhythmias.

Abstract: A defibrillator/pacer having separate energy storage circuits for pacing and defibrillating. The pacing energy storage is charged from residual energy from the defibrillator source to permit high energy pacing after defibrillation. In operation, energy is transferred from the defibrillation energy storage source to the pacing energy storage source which is utilized to provide energy for pacing the heart after defibrillation.

Abstract: An implantable drug administration device can be non-invasively programmed to change both the dosage amount and the dosage interval. Verification of received dosage and interval commands is being achieved by means of an audio transducer which is attached to the device case. Application of a magnet or a programmer to the device inhibits drug delivery.

Abstract: A sense amplifier for a cardiac pacemaker which has an amplifier section with two feedback paths. One path contains small valued capacitors and clock activated switches to form a discrete time feedback path. The other path contains unclocked passive components to form a continuous time feedback path. The sense amplifier generates a detect signal in response to a depolarization of cardiac tissue.

Abstract: A pacemaker sense amplifier circuit exhibiting a very high common mode rejection ratio for detecting intracardiac electrogram signals is disclosed. The circuit includes a sampling capacitor which is differentially charged by the intracardiac signal. The voltage stored on the sampling capacitor is periodically applied to a high input impedance differential voltage amplifier which is referenced to the battery ground. The signal is smoothed and reconstructed by a bandpass filter, and is applied to a comparator to generate a logic level pulse indicative of the occurrence of a cardiac depolarization.

Abstract: An implantable medical device to deliver cardioverting energy to cardiac tissue in synchrony with detected ventricular depolarizations having a low power sensing and control circuitry and high power cardioversion circuitry, sharing a common lead and interface circuitry. The lead possesses a superior vena cava electrode and ring and tip electrodes intended to be placed in the ventricle. A sense amplifier is connected across the ring and tip electrode, and the cardioversion energy is delivered across the superior vena cava electrode and the ventricular electrodes. A circuit for protecting the low voltage sense amplifier circuits from high voltage cardioversion output pulses includes a triac which is electrically shorted across the ring and tip electrodes and the input terminals of the sense amplifier during the delivery of the stimulating pulse.

Abstract: A self-adapting demand pacemaker that recognizes the tachycardia from the intrinsic signals and initiates treatment in the following manner: First, the escape interval of the demand pacemaker is shortened to be identical to the cycle length of the tachycardia, then to overdrive the tachycardia the pacemaker escape interval is continuously shortened with each subsequent beat, for a predetermined number of beats, by a small programmable decrement. Thereafter, the escape interval is restored to its original value and protects against a potential bradycardia. It has to be emphasized that the pacemaker remains in demand mode all of the time; thus stimulation in a vulnerable zone is prevented and some of the hazards that accompany overdrive pacing are reduced.

Abstract: A data telemetry system for use with implanted medical devices for transmitting digital and analog data to a remote receiver by enabling different combinations of fixed and variable value current sources according to a telemetry logic code to energize a tank coil and produce a ringing type of variable frequency RF signal.

Abstract: A waveform detection system for use in a pacemaker for distinguishing normal beats from ectopic or abnormal beats for example, such as those involving ventricular tachycardia, ventricular flutter or fribrillation, premature ventricular beats, supraventricular tachycardia, retrograde conduction; and in dual chamber or atrial applications those involving atrial tachycardia and atrial flutter or fibrillation. The term "abnormal" is employed herein to mean all abnormal beats including those specified above. In the system of the illustrated embodiment a sense amplifier is employed for initiating a counter in response to a detected cardiac event and a voltage controlled oscillator is used for converting the instantaneous value of the applied waveform to a bit rate delivered to the counter. The morphology or shape of the physiological waveform is represented by a number present in the counter at the end of the counting cycle which allows for a therapy decision to be made.

Abstract: An implantable medical device to deliver cardioverting energy to cardiac tissue in synchrony with detected ventricular depolarizations having a DC-DC flyback converter. The primary coil of the converter is periodically coupled and decoupled to ground by a timing circuit to effect charging of a high voltage output capacitor from a low voltage source through the secondary coil. A supply voltage detector alters the time period of the timing circuit to regulate the amount of current drawn by the primary coil. As the low voltage power supply depletes, its impedance increases tending to prolong the charging time of the output capacitor. Further regulating circuitry alters the one-shot time period to avoid loading down the supply voltage which could affect operation of other circuits.

Abstract: A rate responsive pacer which paces the heart at a rate dependent on detected variations in the stroke volume of the heart.

Abstract: A method and apparatus embodied in a pacemaker for attenuating polarization currents or voltages at the output terminals of the pulse generator. A heart pacemaker typically possesses a source of supply voltage, an output capacitor, an output terminal adapted to be coupled to heart tissue. A voltage source is coupled to the output capacitor during a first time interval for charging the output capacitor to a certain voltage. The output capacitor is coupled to the output terminals during a second time interval to discharge its voltage into the heart tissue. A resistor is coupled across the output terminals for providing a current path for the discharging and recharging of the effective capacitance of the stimulated heart tissue. The resistor may be coupled across the output terminals only during the first time interval and not during the discharge of the output capacitor.

Abstract: A pacer subsystem for detecting the existence of tachyarrhythmia including means for measuring the average time interval between successive heart beats and for comparing a sample beat with both a percentage of this average, and with a preset time interval. If the sample beat period is less than both criteria, it is classified as a tachy beat. If the sample beat is longer than either time interval it is classified as a non-tachy beat. Sequences of tachy beats are used to initiate an appropriate therapeutic stimulation regime.

Abstract: Pressure and motion transducer, and cooperating circuitry for an implantable medical device is disclosed. The system includes a clock for the pulse excitation of a dynamic motion transducer and further includes circuitry for recovering the modulated signal from the transducer.

Abstract: An activity sensor mounted within the pacer detects the general activity level of the patient and alters the escape interval of the pacer between a preset minimum and maximum in response to the detected activity level of the patient.

Abstract: An improved telemetry transmission system for transmitting electrocardiographic information, indications of the occurrence of the pacing pulse and for transmitting digitially encoded information from an implanted pacemaker, an implanted drug dispensing device, or other implanted device, to a remote receiver. Digital data transmitted by the implanted system may include all programmed parameters as well as power source status and self test indications, or other programmed digital data such as the device serial number and lot number.