Synchronous pacemaker with upper rate stabilization and method of use

In a method of operation of a synchronous heart pacemaker, comprising the steps of:

• selectively detecting natural electrical heart signals;
• generating an artificial pacing stimulus in timed synchronism with the detected heart signal;
• and
• applying the generated pacing stimulus to the heart to elicit a responsive heart beat;
• the improvement for stabilizing the synchronous pacing rate at an average rate approaching but not exceeding the upper pacing rate comprising the steps of:
• inhibiting the generation of a subsequent pacing stimulus for a predetermined time interval corresponding to an upper pacing rate;
• and
• varying the time elapsed from the detection of electrical heart signals recurring at a rate exceeding the upper pacing rate and the synchronous generation of artificial pacing stimulus to include the predetermined time interval.

In a synchronous artificial cardiac pacemaker comprising pulse generator means operable to generate electrical pacing pulses applicable to the patient's heart to elicit a responsive heart beat in timed synchronism with a natural electrical heart signal detectable from the patient's heart at a synchronous rate extending between a lower, base pacing rate and an upper maximum pacing rate including timing circuit means controlling the generation of the pacing pulses at the lower, base pacing rate upon the failure of the pacemaker to detect such natural heart signals within a maximum time interval, the improvement comprising:

• upper rate limit circuit means for establishing the maximum pacing rate by inhibiting the generation of the pacing pulses for a predetermined minimum time interval following the generation of each such pacing pulse;
• means for varying the time elapsed from the detection of electrical heart signals recurring at a rate exceeding the maximum pacing rate and the synchronous generation of artificial pacing pulses to include the predetermined minimum time interval;
• and
• means for periodically interrupting the selective detection of natural electrical heart signals recurring at a rate exceeding the upper pacing rate so that the generation of a subsequent pacing pulse is in timed synchronism with the detected heart signal.

An atrial synchronous artificial cardiac pacemaker comprising:

• pulse generator means operable to generate electrical pacing pulses applicable to a patient's ventricle to elicit a responsive contraction of the heart in synchronism with a natural atrial electrical signal detectable from the patient's heart at a synchronous rate extending between a lower, base pacing rate and an upper maximum pacing rate;
• said pulse generator means including timing circuit means controlling the generation of the pacing pulses at the lower, base pacing rate upon the failure of the pacemaker to detect atrial or ventricular electrical signals within a maximum time interval, upper rate limit circuit means for establishing the maximum pacing rate by inhibiting the generation of the pacing pulses for a predetermined minimum time interval following the generation of each such pacing pulse;
• reset circuit means coupled to said timing circuit means and adapted to restart the maximum timing interval in response to atrial electrical signals, and trigger circuit means coupled to said pulse generator means and operable to trigger said pulse generator means into generating a pacing pulse independently of said timing circuit means;
• first and second electrodes coupled to said pulse generator means, said first electrode being adapted to be operatively connected to a patient's heart on or in the ventricle thereof to transmit the artificial pacing pulses to the patient's ventricle and to pick up natural ventricular electrical signals, said second electrode being adapted to be operatively connected to a patient's heart on or in the atrium thereof to pick up natural atrial electrical signals;
• first signal responsive means coupled to the first electrode and responsive to ventricular electrical signals picked up by the first electrode for producing a first signal;
• second signal responsive means coupled to the second electrode and responsive to atrial electrical signals picked up by the second electrode for producing a second signal;
• circuit means coupled to said first signal responsive means and said reset circuit means and responsive to the first signal to reset the timing circuit means to restart said maximum timing interval between pacing pulses;
• time delay circuit means coupled to said trigger circuit means and adapted to respond to each second signal for triggering said pulse generator means into generating a pacing pulse in synchronism, after an atrial-ventricular time delay, with the detection of the atrial electrical signal;
• and
• memory circuit means having input means coupled to said first and second signal responsive means and output means coupled to said time delay circuit means, said memory circuit means responsive to the second signal for maintaining the second signal at said time delay circuit for a time period exceeding the elapse of the predetermined time interval of said upper rate limit circuit means, whereby the pulse generator operates to produce a pacing pulse in synchronism with atrial electrical signals detected from the atrium but at an average rate not exceeding the maximum pacing rate.

An atrial synchronous cardiac pacemaker for pacing the ventricle portion of the heart at a rate in synchronism with the natural contraction of the atrium portion of the heart, but at a rate above a lower rate limit and below an upper rate limit, said pacemaker comprising:

• an oscillator responsive to a trigger signal for generating an electrical pulse signal adapted to be applied over a lead to the ventricle portion of the heart to elicit a responsive heart beat, said oscillator further being operable to generate said pulse signal upon the absence of any trigger signal for a designated time period, said oscillator including rate limit means for preventing said pulse signals from being generated at a rate exceeding an upper rate limit;
• sensing means responsive to the occurrence of a cardiac signal caused by the contraction of the atrium of the heart for providing a signal each time said atrium contracts, said sensing means further including means for inhibiting the response by said sensing means to an atrium contraction caused signal which occurs during a fixed time, less than said designated time, after the provision of each pulse signal;
• and
• memory means, which in response to said sensing means signal, provides said trigger signal to said oscillator until said pulse signal is generated, said memory means being reset each time a pulse signal is generated and set each time a sensing means signal is provided.