Abstract: In an implanted pacemaker three basic pacing intervals are established: an A-V delay, a PVARP and an alert interval. These three intervals together define an atrial-to atrial interval which is preferably a function of a metabolic indicated rate. The PVARP and alert interval are adaptively adjusted to optimize the PVARP for the patient without affecting the atrial-to-atrial interval.

Abstract: A pacemaker is provided in which ventricular rate instability is detected and automatically corrected by gradually increasing the ventricular pacing rate. Once the ventricle is stabilized, its pacing rate is gradually decreased as much as possible without losing ventricular stability. Ventricular instability can be a result of an atrial tachyrhythmia such as atrial fibrillation. Therefore, if the pacemaker is a dual chamber pacemaker, its operation is switched to a single chamber pacing mode thereby decoupling the ventricular pacing signals from the atrial pacing signals and atrial triggered ventricular pacing is inhibited until the atrial fibrillation terminates.

Abstract: A dual chamber cardiac pacemaker is adapted to operate in a forced synchrony pacing mode. The pacemaker senses atrial heartbeats and determines whether the rate of sensed atrial heartbeats is pathological or physiological. For physiological atrial heartbeat rates, the pacemaker functions in an AV synchronous pacing mode. For pathological atrial rates, atrial heartbeats occur too frequently for safe AV synchronous pacing so the heart is paced in the forced synchrony mode. In the forced synchrony mode, the pacemaker, upon sensing a natural atrial heartbeat, waits a predetermined atrial protection interval, paces the atria with an atrial stimulation pulse, waits a physiologically appropriate AV delay interval, and then delivers a ventricular pacing pulse at a time which maintains a stable ventricular rate.

Abstract: A dual-chamber pacemaker for confirming pacemaker mediated tachycardia (PMT) after initial detection. The minimum V-V pacing interval is extended to be slightly longer than the interval of the sensed atrial rate. If the A-V Delay intervals in successive cycles remain constant, as opposed to progressively increasing in Wenckebach fashion, then PMT is confirmed.

Abstract: A leadless implantable cardiac arrhythmia alarm is disclosed which continuously assesses a patient's heart function to discriminate between normal and abnormal heart functioning and, upon detecting an abnormal condition, generates a patient-warning signal. The alarm is capable of sensing impedance measurements of heart, respiratory and patient motion and, from these measurements, generating an alarm signal when the measurements indicate the occurrence of a cardiac arrhythmia. Because it requires no external leads or feedthrough connectors, the hermetically-sealed patient alarm is minimally invasive and results in reduced trauma to a patient.

Abstract: A P-wave detector in a single chamber ventricular cardiac pacemaker, which is adapted to perform VDD pacing, senses natural atrial activity in the form of P-waves from a standard lead implanted in the ventricle of the heart. The P-wave detector is electrically coupled to a ventricular sensing lead and, although the electrode of the lead is implanted in the ventricle, circuitry within the pacemaker perceives intrinsic cardiac electrical activity arising from all parts of the heart. The P-wave detector is adapted to differentiate P-wave signals arising within the atrium from other cardiac and non-cardiac signals using template matching techniques in which an acquired signal is compared with a previously stored P-wave template.

Abstract: A rate-responsive pacemaker employing a rate control parameter of respiratory minute volume, derived over a unipolar lead. The pacemaker performs the minute volume measurement by periodically applying a measuring current between the lead and a reference point on the pacemaker case. This measuring current has frequency components in a range from approximately 10 kilohertz to 1000 megahertz. Application of this measuring current allows the pacemaker to detect the voltage which arises from the applied current and, from the detected voltage, to measure the patient's spatial impedance. Spatial impedance and minute volume vary as a function of the patient's pleural pressure. The pacemaker derives minute volume and rate-responsive pacing rate from the spatial impedance measurement.

Abstract: A metabolic demand rate-responsive cardiac stimulation apparatus and method are disclosed which employ multiple physiological rate control parameters, such as respiratory minute volume, patient motion and cardiac stroke volume. The parameters are derived using a single standard pacing lead or transducer. The apparatus and method perform each physiological measurement by periodically applying a measuring current between two points within the apparatus. This measuring current has frequency components in a range of from approximately 10 kilohertz to 1000 megahertz. Application of this measuring current allows the apparatus to detect the voltage which arises from the applied current and, from the detected voltage, to measure the patient's spatial impedance. For a particular measurement, the apparatus controls which physiological parameter is sensed by regulating the frequency content of the measuring current.

Abstract: A hemodynamic control apparatus and method for regulating blood flow within the cardiovascular system in a closed-loop control system using ultrasound measurement techniques to determine a hemodynamic status of the patient and to derive a control parameter for modulating the hemodynamics of the system using electrical or pharmaceutical therapy. This apparatus and method provides for the monitoring of heart contractility and blood flow output from the heart to control an implantable cardiac assist or therapy device to maintain cardiac output without invading the left heart or the arterial system of the patient.

Abstract: In an implantable antiarryhythmia pacemaker, an automatic cardiac arrhythmia detection and classification monitoring apparatus and method for measuring stimulated intracardiac electrogram potentials, deriving therefrom a paced depolarization integral (PDI), analyzing time-based changes in the PDI, detecting and classifying harmful cardiac rhythms while distinguishing harmful from benign tachycardias, and automatically establishing and initiating an appropriate therapy, if necessary, to revert the arrhythmia condition.

Abstract: An antitachycardia pacer and pacing method automatically monitors and supports a patient's hemodynamic status by measuring cardiac output using an ultrasonic sensor. By analyzing cardiac output, the pacer determines whether the heart is beating normally or under conditions of exercise, bradycardia, tachycardia, or fibrillation. If the heart is functioning normally or in bradycardia or exercise, the pacer supports the patient's hemodynamic status by electrically stimulating the heart. The pacer analyzes cardiac output information, detects and classifies abnormal rhythms of tachycardia and fibrillation on the basis of this analysis, and initiates an appropriate therapy accordingly.

Abstract: An apparatus adapted to be implanted in a patient for electrically stimulating the heart and analyzing the heart's stimulated response, and a method of operating the apparatus, are disclosed. The apparatus operates to reduce the stimulation polarization artifact that normally accompanies such stimulation, allowing accurate measurement of stimulated cardiac potentials. The apparatus is useful in such devices as cardiac pacemakers, tachycardia reversion devices, and defibrillators. Optimizing features are provided to allow the apparatus to function properly in noisy environments and with suboptimal leads. In addition, provision is included to make the apparatus capable of performing self-diagnosis for determining when accurate sensing is not possible.

Abstract: A rate-responsive dual-chamber antitachycardia pacer and pacing method which automatically diagnoses and supports a patient's hemodynamic status by measuring metabolic demand and sensing intracardiac electrograms to determine whether the heart is beating normally or under conditions of bradycardia, tachycardia, or fibrillation. The pacer supports the patient's metabolic demand by electrically stimulating the heart at a pacing rate driven either by the heart's sinus node or, alternatively, by the patient's metabolic demand (a metabolic demand indicator), as determined by a sensor. The pacer automatically selects between the indicated rates to determine the best pacing rate for appropriately satisfying metabolic demand at all times. The natural rate, driven by the sinus node, takes precedence over the metabolic indicator rate, provided the natural rate meets a standard determined by the metabolic demand indicator rate.

Abstract: A Doppler ultrasound transducer and interconnected high frequency signal processing circuit, adapted for operative coupling on a distal portion of an intravascular catheter, for ultrasonically sensing high frequency signals representative of blood flow within a patient's cardiovascular system, processing these high frequency signals into baseband audio signals, and communicating these audio signals to associated low frequency signal processing circuitry located in the proximal portion of the catheter by modulating the load current of a power supply within the high frequency circuit.

Abstract: A hemodynamic control apparatus and method for regulating blood flow within the cardiovascular system in a closed-loop control system using ultrasound measurement techniques to determine a hemodynamic sttus of the patient and to derive a control parameter for modulating the hemodynamics of the system using electrical or pharmaceutical therapy. This apparatus and method provides for the monitoring of cardiac myofibril motion to assess heart contractility and hemodynamic performance, and to control an implantable cardiac assist or therapy device. In this manner, the invention maintains the patient's hemodynamic status without invading the left heart or the arterial system of the patient.

Abstract: A hemodynamic control apparatus and method for regulating blood flow within the cardiovascular system in a closed-loop control system using ultrasound measurement techniques and intracardiac electrogram sensing to determine a hemodynamic status of the patient and to derive a control parameter for modulating the hemodynamics of the system using electrical or pharmaceutical therapy. This apparatus and method provides for the monitoring of heart contractility and blood flow volume in the circulatory system to control an implantable cardiac assist or therapy device to maintain the hemodynamic status of the patient without invading the left heart or the arterial system of the patient.

Abstract: An implanted programmable ambulatory electrocardiography (AECG) patient monitoring device that senses and analyzes electrocardiographic signals from at least one subcutaneous precordial sensor chronically and frequently to detect electrocardiogram and physiological signal characteristics predictive of malignant cardiac arrhythmias. The device includes telemetric capabilities to communicate a warning signal to an external device when such arrhythmias are predicted.

Abstract: A rate-responsive dual-chamber pacemaker and pacing method for supporting the heart with electrical stimulation at a pacing rate driven by the heart's sinus node or, alternatively, by a sensor adapted to determine the patient's metabolic demand (a metabolic demand indicator). The pacemaker automatically selects between the indicated rates to determine the best pacing rate for appropriately satisfying metabolic demand at all times. The natural rate, driven by the sinus node, takes precedence over the metabolic indicator rate provided the natural rate meets a standard determined by the metabolic demand indicator rate. The pacemaker upper rate response mechanism allows atrioventricular synchrony at natural sinus rates ranging from low rates to high exercise rates, even up to the programmed maximum rate, but maintains ventricular rate stability during pathological atrial tachycardias by reverting to pacing in a rate-responsive VVI mode.

Abstract: A pacemaker which generates a triphasic stimulus; the first and third phases are positive pulses, and the second is the negative stimulus. After-potentials are so low that reliable sensing of evoked signals are possible. The rapidity of the charge balancing is not affected by the stimulus amplitude because the relative amplitudes of the three phases are maintained independent of the stimulus amplitude.

Abstract: A rate-responsive pacemaker whose rate control parameter is minute volume derived over a bipolar lead. An algorithm based on averaged samples and zero crossings provides enhanced accuracy. Sustained exercise at high pacing rates is possible.