Abstract: An implantable energy supply system having at least two cells is disclosed. The system may have a switch with a first state in which the cells are electrically connected to a load, and a second state in which each cell is electrically connected with its own charger. A measurer may be electrically connected to a cell to provide an indication of the charge on the cell.

Abstract: An optical sensor includes an optical source capable of being positioned on a tissue and emitting near infrared light into the tissue at a plurality of selected wavelengths, and a photodetector capable of detecting reflected light from the tissue. The photodetector being positioned on the tissue removed from the optical source but sufficiently close in proximity to the optical source to contact the same general tissue. The optical sensor further includes an oscillator coupled to the optical source and capable of activating the optical source to emit the near infrared light, and a modulator coupled to the oscillator and capable of controlling radio frequency modulation of the optical source to emit a radio frequency component that is used to measure the optical path length and absorbance of an analyte of interest within the tissue.

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: 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 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 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: A metabolic-demand pacemaker in which the standby rate is a function of minute volume. Electrodes are placed in a blood vessel in the vicinity of the patient's pleural cavity, a known current field is established in the blood, and the impedance in the field is measured. The impedance is a function of the pleural pressure which, in turn, is a function of the patient's minute volume. The system also includes a mechanism for calibrating the standby rate to equal the nominal standby rate for a minute volume which equals a long-term average value, with the standby rate being changed in accordance with the deviation of the minute volume from the long-term average value.