Abstract: A dual-chamber pacemaker provides DDI pacing with PVC-protected hysteresis and automatic AV interval adjustment. An extended hysteresis atrial escape interval (AEI.sub.H) is invoked in response to the occurrence of either an atrial paced event followed by a sensed R-wave (an AR event), or an atrial sensed event followed by a sensed R-wave (a PR event). The occurrence of a premature ventricular contraction (PVC) thus does not trigger AEI.sub.H. In one embodiment, AEI.sub.H is not invoked unless the sensed AR or PR interval exceeds a prescribed reference interval. In a further embodiment, the AV interval (AVI) associated with the DDI operation is automatically shortened following an atrial stimulation pulse (A-pulse) delivered upon the timing-out of the AEI.sub.H. The shortened AVI is maintained for a programmed number of cycles of DDI operation, after which a lengthened AVI is reestablished for one cycle.

Abstract: A rate-responsive heart stimulator with a variable stimulation interval contains a measurement device which generates a measurement signal corresponding to the volume of blood in a heart during the blood-filling phase (diastole) and a comparator which compares the measurement signal with a defined threshold value corresponding to a defined degree of blood filling. The comparator generates a control signal when the measurement signal reaches the threshold value, the control signal representing the time elapsing since the last stimulation pulse, and controlling the heart stimulator's stimulation interval.

Abstract: In a heart stimulator which delivers stimulation pulses to a heart when the heart's spontaneous rate drops below a defined basic rate, in order to reduce the period during which the heart stimulator emits stimulation pulses, the defined basic rate is slow. When the spontaneous heart rate drops below the defined basic rate, stimulation pulses are initially emitted at a faster stimulation rate, in relation to the basic rate, the stimulation rate then dropping toward the defined basic rate.

Abstract: A transesophageal defibrillating system includes a large area anterior patch electrode and a large area posterior patch electrode, as in some conventional exterior defibrillating systems. An esophageal probe has a pair of ring electrodes, one of which is carried at or near its distal end. The system is operatively arranged to supply defibrillation pulses between the large anterior patch electrode and either the distal electrode (carried by the probe) or the large posterior electrode, depending on which one of the latter two electrodes is connected or coupled by the clinician or paramedic to the defibrillating pulse source. The system includes a source of pacing pulses which may be supplied to the patient via the anterior patch electrode and at least one of the electrodes carried by the esophageal probe. The distal electrode is believed to be the more effective electrode to use for this purpose.

Abstract: The apparatus and method for screening and diagnosing trauma or disease in body tissues involves the use of DC biopotential sensing electrodes having DC offset potentials within an acceptable range and electrical characteristics which enhance the accuracy of the biopotential measurement. The apparatus checks the electrodes connected thereto prior to a measurement cycle and will not initiate the measurement cycle if improper electrodes are present. The electrodes may be formed to selectively pass only certain ions thereby enhancing the sensitivity of the electrodes.

Abstract: An improved hermetically-sealed automatic implantable cardioverter-defibrillator (AICD) or any other bioimplantable device which may be operated on a single rechargeable cell, or a dual power source system, the rechargeable component being recharged by magnetic induction. Included in the implantable devices are new lithium rechargeable chemistries designed to sense the state-of-charge or discharge of the battery; a battery charge controller specifically designed to recharge a lithium battery rapidly to less than 100% full charge, and preferably 90%, more preferably 80%, of full rated charge capacity; and charging means for multi-step charging. The batteries are based on lithium chemistries specially designed to yield higher currents than conventional primary lithium chemistries and to permit long-term performance despite sub-capacity recharging.

Abstract: An implantable cardiac defibrillation lead is provided in which surface modification and deposition techniques are utilized to provide improved electrical and mechanical characteristics. The surface of an electrode can thereby be matched to the heart tissue for biocompatibility while at the same time providing for the appropriate electrical and mechanical characteristics of the electrode material.

Abstract: A method and apparatus for processing data to be communicated between an implantable medical device and an external medical device to improve detectability of communication errors. An encoded block of data including message data and redundant data is processed by converting alternating data values of either the message data or the redundant data to respective complement data values. The altered block of data is communicated using relative pulse position modulation. The combination of alternating original and complement data with relative pulse position modulation (RPPM) takes advantage of the opposing adjacent errors characteristic of RPPM to decrease the probability of communication errors occurring in combinations that are undetectable by the decoding of the block of data.

Abstract: During a calibration phase, the representative characteristics of a parameter are determined, a reference value is deduced for determining pacing efficiency, and during a threshold search phase, the value of the capture threshold is determined as a function of pacing efficiency.

Abstract: A programmable output connector of an implantable cardioverter-defibrillator (ICD), or similar implantable medical device, allows each of a multiplicity of output terminals to be selectively connected to either a positive or a negative output bus of the ICD. The positive and negative output buses of the ICD, in turn, are switched to an output capacitor, or equivalent output circuit, of the ICD. An electrical charge stored on the output capacitor, or otherwise generated by the output circuit, is presented to the multiplicity of output terminals in accordance with a programmed polarity. The programmed polarity causes a selected one or group of the multiplicity of output terminals to be connected to the positive output bus, and a selected other or group of the multiplicity of output terminals to be connected to the negative output bus. Respective electrodes designed for contacting cardiac tissue may then be electrically connected to each one of the multiplicity of output terminals.

Abstract: The first embodiment of the present invention repositions the shunt thyristor used in the monophasic-waveform generator of the prior art so that it discharges the main capacitor through a series thyristor, thus increasing current through it briefly, rather than reducing current through it. The result of this arrangement is that the node between the series thyristor and the heart is pulled rapidly to a low voltage, causing the shunt switch to discharge the cardiac capacitance, as well as the main capacitance. The consequence is that discharging the cardiac capacitance requires a reversal of current in the heart, which enhances the heart-stimulating effect of the defibrillating waveform. The resulting true-voltage-pulse waveform has an efficacy approximating that of a biphasic waveform and is achieved with a circuit no more complex than that used to generate a monophasic waveform.

Abstract: An electrode arrangement has at least two coiled electrode conductors which are mechanically and electrically interconnected in a contact region. Within the contact region, the flights of the coiled conductors are engaged, such as by the flights of one conductor surrounding the flights of the other conductor, or the flights being intertwined, thereby producing the necessary mechanical and electrical connection by means of the spring force associated with the coiled structure of each conductor. The connection of the conductors thereby becomes simpler to assemble, and does not require crimping, and results in a more reliable and flexible connection area.

Abstract: A cardiac pacemaker with an analog telemetry system. A calibration circuit within the pacemaker is adapted to provide a reference signal of known character to the pacemaker's telemetry system. The reference signal is transmitted across the telemetry link as if it were an actual cardiac signal, and received by an external programmer. Since the reference signal has known, predetermined qualities, the programmer can automatically calibrate and scale the telemetry signal from the pacemaker, thereby increasing the accuracy of the telemetry channel. The increased accuracy is particular useful in assessing rejection of a transplanted heart, which is known to be associated with a 15% decline in the peak R-wave amplitude of the cardiac signal.

Abstract: A novel cardiac assist blood pump is disclosed. The blood pump comprises a pump chamber, a pressurizing chamber provided adjacent to the pump chamber, a rotor chamber provided adjacent to the pressurizing chamber and an impelled positioned in the pump chamber, said pump being characterized in that the rotation shaft of the impeller means is provided with a first seal member having a skirt portion which is made of an elastomeric material and extends downward to cover the clearance between the rotation shaft and the first rotation shaft hole provided between the pump chamber and the pressurizing chamber and a second seal member similar to the first one which covers the clearance between the rotation shaft and the second rotation shaft hole provided between the pressurizing chamber and the rotor chamber; and tile pressurizing liquid is forced into the pressurizing chamber.

Abstract: A low cost, limited-function implantable medical device. The device's synchronous circuits are driven by an ultra-slow master clock signal produced without utilization of a crystal oscillator. The device is non-invasively programmable by means of an externally applied programming magnet, which is detected by a solid state magnetic sensor (MAGFET) circuit in the implanted device. The MAGFET circuit is capable of discriminating between two polarity orientations of the programming magnet, so that one polarity is associated with increasing programmable parameters and the opposite polarity is associated with decreasing programmable parameters. Upon initial placement and detection of the programming magnet, the disclosed device performs a threshold margin test comprising three asynchronous stimulating pulses at the current pulse width and pulse amplitude settings.

Abstract: In a device for tissue stimulation, the stimulation energy is matched to the stimulation sensitivity of the tissue by altering the stimulation energy in steps upwardly until a tissue reaction is detected, or in steps downwardly until a tissue reaction fails to occur. In order to obtain a safety factor which is expressible in volts with the lowest possible current consumption, stimulation pulses are generated in the determination of the stimulation sensitivity having an amplitude at a voltage which is below the available voltage of a voltage source by a voltage value which corresponds to the safety factor, and the pulse duration is altered in the aforementioned steps. Stimulation subsequently takes place using the pulse duration found in this manner and at a pulse amplitude corresponding to the available voltage.

Abstract: Pulse shocks of high-frequency wave energy (e.g. RF, microwave, high-energy infra-red or laser electromagnetic wave energy or ultrasonic acoustic wave energy), rather than DC electric pulses, are employed to non-invasively produce force fields of an intensity sufficient to create transient pores in the plasma membranes of targeted cells, such as tumor cells or other diseased cells, through which either locally or systemically applied drug or chemotherapeutic agents can easily enter and be taken up by the targeted cells, even for (1) the cells of a deep-seated tumor, (2) non-localized metastasized tumor cells within a patient's body, or (3) cells (e.g., blood cells) temporarily removed to outside of a patient's body.

Abstract: A rate-response pacemaker includes a plurality of sensors that each sense a physiologic-related parameter suggestive of the physiological needs of a patient, and hence, indicative of the pacing rate at which the rate-responsive pacemaker should provide pacing pulses on demand. The pacemaker includes appropriate selection circuitry for selecting which of the sensor parameters, or weighted combinations thereof, should be used as the sensor indicated rate (SIR) signal to control the pacing rate of the pacemaker at any given time. The pacemaker also includes a memory circuit for selectively storing the sensor parameters from each of the plurality of sensors. The stored sensor parameters may thereafter be downloaded from the pacemaker memory and evaluated in non-real time with the various sensor parameters assuming different weighting (scaling) factors and different processing parameters (e.g.

Abstract: A medical electrode device has a flat, flexible and electrically insulating electrode carrier, on which at least one electrode conductor is arranged in a predetermined pattern, the conductor being partially exposed to define an electrode surface through which electrical energy is delivered in vivo to tissue adjacent the surface. The electrode carrier insulates the passive side of the electrode from surrounding tissue. The electrode surface defined by the conductor has a relatively broad extent, such as for defibrillating a heart. The electrode carrier has at least one opening therein extending through the predetermined pattern of the electrode conductor, so as to reduce the insulative effect and to increase the flexibility and resilience of the electrode carrier.

Abstract: A main energy delivery electrical circuit for use in an implantable cardioverter defibrillator device comprises a low power output primary defibrillator battery, a high power output intermediate power intensifying battery, a switch for permitting the intermediate power intensifying battery to rapidly charge a main energy delivery capacitor, and a main energy delivery capacitor. The main energy delivery capacitor is configured for discharging, in a first pulse, an electrical charge derived from the primary battery and for discharging certain subsequent pulses of electrical charge derived from the intermediate power intensifying battery. The circuit permits the implantable cardioverter defibrillator device to deliver multiple closely spaced defibrillation pulses to a heart.