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 physiological event signal sensing system in a cardiac control or monitoring device for detecting spontaneous cardiac electrical events which may be obscured by continuous or burst EMI line frequency noise. The noise rejecting sensing system of this invention senses and samples cardiac signals which may include a noise component which is produced by power line interference in addition to a physiological signal component. The sampling frequency is selected to be an integer multiple of at least one common power line frequency. The system notch filters the cardiac signal to remove line frequency components, using either or both lowpass and highpass notch filtering coefficients, then limits the filtered output to the amplitude of the corresponding filter input to remove filter output signals caused by the sudden termination of line frequency noise which is characteristic of burst noise.

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 implantable device for the treatment of malfunctions of a patient's heart is disclosed. The device includes a first modality for sensing an electrical function in the patient's heart and providing a first signal representative of such electrical function, and a second modality for sensing an haemodynamic function in the patient's heart and providing a second signal representative of such haemodynamic function. The device is also provided with first circuitry that is primarily responsive to the signal from one of the sensing modalities for analyzing the state of the heart's function and providing any required electrical shock therapy to the heart. The device further includes second circuitry that is responsive to uncertainty in regard to the therapy to be provided by the first circuitry and is operative to change the responsiveness of the first circuitry to the signal provided by the other of the sensing modalities for controlling the therapy that is to be provided to the heart.

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 implantable device and method for providing anti-arrhythmia therapy to, and including arrhythmia in, a patient's inadequately functioning heart are disclosed. A pacemaker, defibrillator and microprocessor are utilized in conjuction with an electrode lead system adapted to be connected to the heart for providing the therapy and for inducing arrhythmia. Circuitry is employed in the pacemaker and defibrillator to generate respective trains of spaced pulses for delivery to corresponding portions of the electrode lead system, and a smoothing filter is provided in series with the trains of pulses to smooth each of the trains of pulses into discrete single pulse having a continuous waveform. The spacing, durations and polarities of the pulses in the trains are selectively variable so that the waveforms of the discrete single pulses can be selectively varied to provide diferent waveforms therein, in accordance with the needs of the patient and the programming of the device.

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 implantable device and method for treating cardiac arrhythmias in a patient's heart are disclosed. A source of antitachycardia pacing therapy and an electrode system including at least three electrodes for delivering the antitachycardia pacing therapy to the heart are provided. Circuitry and software for detecting a tachycardia having a site of focus in the heart and for determining the relative distances of the electrodes from the focus site are also provided. The three or more electrodes are connected to the source of antitachycardia pacing therapy based on the relative distances determined and in such a manner as to create a virtual electrode at the focus site upon delivery of the therapy to the heart.

Abstract: An implantable device for the treatment of malfunctions of a patient's heart is disclosed. The device employs defibrillation patch electrodes positioned on the outer surface of the heart generally outwardly of the left and right ventricles of the heart, in conjunction with a non-polarizing sub-threshold constant current or constant voltage signal and appropriate electronic signal sensing and processing circuitry, to determine changes in variations of the transcardiac impedance of a patient's heart, such changes being representative of corresponding changes in the level of haemodynamic compromise of the heart. Bradycardia support pacing therapy, antitachycardia pacing therapy, cardioversion therapy and defibrillation therapy, or no therapy, are selectively initiated by the device, depending on the level of haemodynamic compromise determined to be extent by the device.

Abstract: An implantable device for treating a malfunctioning heart is disclosed. The device includes a high voltage circuit having a tank capacitor for storing therein during a charging mode of operation thereof high voltage DC electrical energy and for delivering such energy to a malfunctioning heart in the form of an electrical shock during a discharging mode of operation thereof.

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 method and apparatus for treating tachycardias are disclosed which utilize tachycardia cycle lengths in connection with selecting the type of antitachycardia pacing to be used in such treatment. A range of tachycardia cycle lengths is selected for which antitachycardia pacing treatment is indicated. This range is divided into a plurality of sub-ranges of tachycardia cycle lengths, and corresponding storage locations are established for each of the tachycardia cycle length sub-ranges. Antitachycardia pacing parameters which have been successful in reverting previous tachycardias are stored in their corresponding storage locations, and subsequent tachycardias are treated using antitachycardia pacing parameters selected from storage locations that correspond to, or are closest to correspondence with, the storage locations corresponding to the tachycardias to be treated.

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.

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: An implantable, battery-operated cardioverting/defibrillating pacemaker device with the ability to sense and respond to haemodynamic compromise is described. The ventricular pressure (VP) and electrical activity of the heart are sensed via one or more transvenous or epicardial devices. The filtered peak-to-peak amplitude (VFPPA) and a peak pressure function (VPPF) based upon the right and/or left VP waveform(s) are derived. One of the VFPPA and VPPF, and electrically derived heart rate information, are used in the diagnosis of arrhythmic states. Bradycardia support pacing is initiated and terminated by reference to the VP signal, and the pacing pulse voltage used during bradycardia support pacing is optimized in order to extend battery life of the device. This is done by using the haemodynamic sensor to confirm the presence of an appropriate haemodynamic response to the delivery of bradycardia support pacing, and adjusting the pacing voltage to its lowest efficacious level.

Abstract: An arrhythmia control method and device are disclosed which monitor the cardiac state of a patient, utilize an arrhythmia recognition algorithm to detect and distinguish among bradycardia, sinus rhythm, supraventricular tachycardia and ventricular fibrillation, and deliver therapy in the form of electrical energy to cardiac tissue to revert selected arrhythmias and restore normal sinus rhythm. In its preferred form the device is an implantable combined dual chamber pacing and cardioverting device that is adapted to be electrically connected to the atrium and ventricle for sensing the atrial and ventricular waveforms and deliverying shock therapy thereto as required. The arrhythmia recognition algorithm utilizes the sensed atrial and ventricular waveform data for, among other things, distinguishing between ventricular tachycardia and supraventricular tachycardia.