Arco Medical Products Company

Robert A Walters

Steve Andrew Kolenik

Russell E Hirtz

William L Johnson

Gary W Bivins

An implantable pacemaker having circuit means for indicating, by pulse width modulation of the delivered pacing pulses, the programmable control states which control the selected pacemaker operating perameters. The circuitry includes a parallel to serial shift register adapted to receive the control states from a pacer circuit and to generate a serial multiple bit word when the pacemaker is switched to a magnetic mode. The shift register is clocked by stimulus timing signals, and the multiple bit word drives a one shot generator, the output of which is combined with the timing pulses to produce pulse width modulated pacing pulses.

Pacemaker with circuit for pulse width modulating stimulus pulses in

A programmable digital atrio-ventricular pacer is provided whereby a single programming circuit is utilized for providing program control signals for control of separate ventricular and atrial pacing circuits. The atrial stimulus circuitry is controlled by a multiple bit control signal to cause derivation of atrial timing signals from the same clock signal as used for deriving ventricular stimulus pulses. A programmable digital multiplier is employed in combination with a counter to set the atrial escape interval independent of the timing of the ventricular stimulus pulses.

Programmable atrio-ventricular pacer

A circuit for indicating at a remote location the control states of a fully implantable heart pacer includes a parallel to serial converter which receives the control states from a register which controls the parameters of the associated pacer. When the pacer is switched to an asynchronous or to a magnetic mode, the data is shifted through the parallel to serial converter. A delay is added between pulses when a particular logic state appears, and no delay is added if the complement of that logic state appears. The parameters can therefore be determined externally by observing the successive periods between stimulation pulses in the asynchronous or magnetic mode of the pacer.

Circuit for determining the parameter control states of an implanted

A programmable implantable pacer is provided for performing the dual functions of demand pacing as well as standby tachycardia breakup. A command parameter control is used for programmably controlling parameters of the pacer operation as well as of the tachycardia recognition and response to same. Upon recognition of tachycardia, a series of stimulus pulses of predetermined rate and number are delivered, the tachycardia breakup pulses being generated and delivered through an output circuit utilized commonly with the demand pacer circuitry.

Programmable tachycardia pacer

A heart pacer employing a digital parameter controlling circuit is controlled by data received from an external source, the data preferably being in the form of magnetic pulses of width corresponding to the desired logic state of the parameter controlling signal. The externally transmitted signal which is received by the pacer comprises both parameter data for controlling selected pacer parameter operation and access data which is processed by the pacer for determining whether the parameter data is accepted for control purposes. The access and parameter data components of the externally generated signal are intermixed so that when receipt of the signal is enabled by the pacer, proper receipt of the parameter data is also ensured.

Method and means for receiving parameter control data in an implantable

A digital cardiac pacer has an asynchronous interval counter to count clock pulses to establish a stimulation interval at the end of which it produces a pulse for initiating a stimulation pulse. A control counter to which amplified naturally occurring heat pulses or stimulation pulses are applied controls the delivery of a resetting pulse to the asynchronous interval counter to reinitiate its count. If the stimulation, heart, or an interference pulse is detected during the count of a 'refractory period,' the control counter is reset and the refractory period is extended. If another stimulation, heart, or interference, pulse is detected during the extended refractory period, no resetting pulse is delivered, and the asynchronous interval counter continues its normal count. If during the period of time following the extended refractory period a stimulation, heart, or interference pulse is received, the control counter produces a resetting pulse to reset the asynchronous interval counter. A delay circuit between the control and asynchronous counters causes the stimulation interval to be shortened during the reception of interference pulses.

Digital cardiac pacer

An implantable cardiac pacer is instructable to vary the stimulation pulse interval, the stimulation pulse width, the stimulation pulse amplitude, the pacer sensitivity, the refractory period and the mode (demand or asynchronous). A master parameter control circuit is provided to vary selected parameters of the heart pacer in accordance with an externally applied control signal. An external control unit produces two sequential series of pulses, the first series being an access comprising at least one digital '0' state which must be detected by an access code detecting circuit within the master parameter control before the following parameter code will be accepted to vary the pacer parameters. The parameter code, generated subsequently to the access code, determines the selected set of pacer parameters, and can be selected from external controls upon the external control unit. The master parameter control circuit includes means for recognizing the access code to enable the master parameter control circuit to only thereafter accept the selected parameter code. The entire parameter code must then be entirely received prior to changing the pacer parameters.

Implantable digital cardiac pacer having externally selectible operating

A cardiac pacer includes means connected to electrodes adapted to be connected to a patient's heart for detecting and amplifying naturally occurring heart pulses. First and second counters are provided to receive periodic pulses from a clock pulse generator to time a refractory period and a stimulation pulse period, respectively. A rate limiting circuit limits the stimulation pulse rate to a predetermined rate, above which, the pacer is precluded from producing stimulation pulses. A test circuit is selectively connectable to produce a visual indication of the production of a stimulation pulse.

Cardiac pacer with rate limiting means

A circuit for measuring the sensitivity of a cardiac pacer includes a generator for producing a signal which varies as a function of the sine.sup.2 of a predetermined frequency. The signal is generated by an intermediate step of generating a waveform having the value of 1/2 [1-COS(.theta./2)]. The waveform is applied to an input of a cardiac pacer, and the amplitude varied in a measurable manner. The output of the cardiac pacer is observed in response to the signals applied to its input, and the amplitude of the voltage waveform which just inhibits the operation of the pacer is directly read from the amplitude varying control.

Circuit for measuring the sensitivity of a cardiac pacer

A circuit for measuring the refractory period of a heart pacer includes first, second and third monostable multivibrators. The first monostable multivibrator is reset by the reception of a pacer stimulation pulse to produce a state change for a time period longer than the stimulation pulse interval of the pacer. The second monostable multivibrator is triggered by the trailing edge of the stimulation pulse, and has a variable time constant to produce a state change for a controlled period of time. The third monostable multivibrator applies a pulse to the pacer at the conclusion of the state change of the second monostable multivibrator. A counter is provided which counts the stimulation pulses produced by the pacer, and is connected to a resistive time constant circuit, to add additional time controlling resistors into the time constant circuit of the second monostable multivibrator. A latch circuit discontinues the advancement of the counter after the first monostable multivibrator state change is reached, and a pulse width monitor indicates the time width of the state change of the second monostable multivibrator to thereby indicate the refractory period of the pacer.

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Pittsburgh, PA, United States of America

Robert A Walters