Abstract: An atrial tracking dual-chamber pacemaker and method of use for reducing the risk of initiating a pacer mediated tachycardia (PMT), and breaking such a PMT if once started. The pacemaker includes means for sensing a premature ventricular contraction (PVC). The pacemaker operates in a conventional manner unless a PVC is sensed. If a PVC is sensed, in accordance with one embodiment, an extended atrial refractory period is triggered in an attempt to block any retrograde atrial events resulting from the PVC. This is followed by an atrial alert time window. After a prescribed A-V delay subsequent to the timing out or other termination of the atrial alert time window, a ventricular stimulation pulse is generated, unless prior ventricular activity is sensed that inhibits such ventricular stimulation pulse.

Abstract: The present invention is an apparatus (1) for interpreting and displaying cardiac events of a heart connected to a cardiac pacing means (2) comprising a telemetry head (4), a first interpreting mean 6 with means connected to said telemetry head (4), a second interpreting means (12) with means connected to a plurality of ECG electrodes having paddles 8a at their digital end via electrical conduit (10), a control means (14) with means connected to said first and second interpreting means, (6) and (12) respectively, a multi-section memory means (16) with means connected to said control means (14), a D/A convertor (20) with means connected to said memory (16) a printing means (22) with means connected to said D/A convertor (20), logic means (24) with means connected to said memory means (16) and a display means (26) with means connected to said logic means (24).

Abstract: A programmable cardiac stimulator capable of stimulation in the DDX modality having a first sensing system (46) for sensing electrical activity in the atrium, a second sensing system (48) for sensing electrical activity in the ventricle, a pulse generator (24) connected to the first (46) and second (48) sensing system and responsive to electrical activity sensed by these systems (46, 48) for determining the timing for supplying electrical pulses to the atrium and ventricle, for this depolarization and a circuit with the pulse generator (24) for changing the stimulation modality from DDD to DVI when premature ventricular activity is sensed by the second sensing system (46) prior to sensing electrical activity by the first sensing system (48) during the pacer cycle.

Abstract: A cardiac stimulation apparatus capable of stimulation in the DDI modality having a first sensing system (46) for sensing electrical activity in the atrium, a second sensing system (48) for sensing electrical activity in the ventricle, a pulse generator logic (24) connected to the first (46) and second (48) sensing systems responsive to electrical activity sensed by the first (46) and second (48) sensing systems for determining the timing for supplying electrical pulses to the atrium and ventricle for their depolarization, a first circuit within the pulse generator logic (24) for preventing synchronization of timing within the pulse generator (24) for producing apparatus generated pulses to the ventricle when electrical activity is sensed in the atrium, a second circuit within the pulse generator logic (24) for inhibiting an apparatus generated pulse to the atrium when electrical activity is sensed resulting from natural depolarization of the atrium, and pulse generator logic timing means (32, 34, 44) for int

Abstract: A programmable cardiac tissue stimulator having a receiving coil and RF pulse width check/data separator (6) for receiving programming data, a communications State sequencer (8) for directing the sequence of command activities within the apparatus, command decode and address latch (12), memory (16, 18, 20, 22, 30, 40, 42) for storing the received programming data, pulse generator logic (24) for generating an output stimulation pulse according to a programmed stimulation scheme, a first timer (32), a second timer (34) and third timer (44) interactive with the pulse generator (24) and memory (16, 18, 20, 22, 30, 40, 42) for carrying out the timing functions of the pulse generator logic (24), a first sensor (46) for sensing electrical activity in the atrium, a second sensor (48) for sensing electrical activity in the ventricle, antitachycardia logic (50) for limiting the rate of natural stimulation of cardiac tissue, an output lead (54) to the atrium, an output lead (56) to the ventricle, and a control clock (28

Abstract: A battery monitoring means for an implantable tissue stimulator in which a signal related to the internal impedance of an implanted battery is telemetered to an external receiving means. More specifically, the implanted battery is loaded by a varible load until current flowing through the battery lowers its output voltage until it has a predetermined relationship with respect to a reference voltage. The current flowing through the battery to achieve the predetermined relationship is directly related to the internal impedance of the battery. A voltage related to the value of this current is then telemetered to the external receiving means. In a specific embodiment, the variable load is a field effect transistor (FET) connected as a source follower. The impedance of the FET is controlled by the output of an operational amplifier having as inputs the reference voltage and a voltage related to the output voltage of the battery.

Abstract: An apparatus and method for displaying and controlling parameters for a programmable living tissue stimulator system. Visual indicators corresponding to control parameters or signals for the tissue stimulator system are divided into a predetermined number of groups. One of these groups containing a parameter to be selected for the tissue stimulator system is selected, the selected group being identified by a visually identifiable indication. A parameter within that group is then selected for transmission to an implanted memory means which controls an implanted tissue stimulator. In a specific embodiment, a matrix of visual indicators consisting of R rows and S columns is provided, each visual indicator corresponding to a specific control signal. A means is provided whereby at least one visual indicator contained in a selected R row will blink on and off, the blinking indicators identifying control signals to be selected for the implanted memory means.

Abstract: A battery life extender for use in an implantable tissue stimulator. The tissue stimulator comprises a battery which powers a volatile memory, control circuits and a pulse output circuit all of which are connected in parallel across the battery. The invention provides a means for controlling current through the output circuit as a function of a difference voltage between the battery output voltage and a reference voltage. The reference voltage and battery voltage comprise inputs to a differential amplifier which in turn provides an output control voltage which controls a field-effect transistor (FET) connected in series with the output circuit and battery. As this control voltage rises, current through the field-effect transistor is reduced, thereby reducing the amplitude of the pulses from the output circuit and the current drain from the battery.

Abstract: A battery monitoring means for an implantable living tissue stimulator system in which various battery voltages are telemetered to an external receiving means, these voltages being related to the internal impedance of the implanted battery. More specifically, a battery loading circuit is provided which incorporates a switch means for loading the battery in accordance with a predetermined sequence. In a specific embodiment, first and second resistors are sequentially connected across the battery. The battery output voltage is telemetered to an external receiving means during this sequential connection. By knowing the values of the two resistors, the internal impedance of the battery can be calculated, this impedance being related to the remaining life of the implanted battery.

Abstract: A telemetry system for use in a living tissue stimulator system in which an externally located oscillator is controlled by impedance changes in an impedance reflecting circuit located in an implantable tissue stimulator. In a first embodiment the impedance reflecting circuit is an LC circuit thereby frequency modulating the externally located oscillator and in a second embodiment it is an LR circuit thereby amplitude modulating the externally located oscillator. More specifically, the externally located oscillator drives an LC circuit in which the inductor is positioned in magnetically coupled relationship to an inductor in the impedance reflecting circuit. The externally located oscillator is chosen so that its frequency and amplitude is partially determined by the impedance of the LC circuit and the magnetically coupled impedance reflecting circuit.