Abstract: A patient-implantable cardiac stimulation apparatus adapted to measure body impedance, derive at least one physiological parameter from the impedance measurement, sample a time sequence of the physiological parameter and transmit the sequence to an external monitoring device for display and analysis. The apparatus may also sense intracardiac electrograms while it is measuring body impedance and deriving the physiological parameter, in which case it formats and transmits a combined intracardiac electrogram and physiological signal to the monitoring device.

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: 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 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 implantable cardiac allograft rejection monitoring apparatus and method for measuring stimulated intracardiac electrogram potentials, performing processing and time based analysis of changes in the potential, and deriving from the time history of the analyzed signals allograft rejection control parameters. The apparatus communicates the allograft rejection control parameters to an external communicating device and may use the parameters to control the output of an implanted drug infusion pump.