Variable P-R interval pacemaker

In a cardiac pacemaker having means for providing an electrical stimulus to the ventricle after the sensing of an atrial contraction, the improvement comprising means responsive to the rate of atrial contractions for affecting the time between the sensing of an atrial contraction and the provision by said providing means of said electrical stimulus to the ventricle, said affecting means including differential amplifier means, reference voltage providing means coupled to one input of said differential amplifier means, energy storage means coupled to provide a voltage manifesting stored energy to the other input of said differential amplifier, switching means coupled to said reference voltage providing means and said energy stored means for being switched to a first state in response to the sensing of an atrial contraction, said reference voltage providing means responding to said first state of said switching means by providing a reference voltage to said one input of said differential amplifier, said energy storage means responding to said first state of said switch means by increasing the energy stored thereby at a first rate, said switching means remaining in said first state until said voltage provided by said energy storage means equals said reference at which time said switching means responds by switching to a second state, and energy storage means responding to said second state of said switching means by discharging energy at a second rate, which second rate is less than said first rate.

A cardiac pacemaker comprising means for providing an electrical stimulus to the ventricle after having sensed an atrial contraction;

• and
• means responsive to the rate of atrial contractions for affecting the time between the sensing of an atrial contraction and the provision by said providing means of said electrical stimulus to the ventricle;
• said electrical stimulus providing means including oscillator means having energy storage means which increasingly stores energy at a first rate until energy of a certain value has been stored, whereupon a pulse is provided and the energy stored by said energy storage means decrease to a reference value at a second rate, which second rate is much greater than said first rate;
• and
• wherein said affecting means is coupled to said energy storing means for causing the energy stored by said energy storing means to be at said certain value at a time dependent upon said rate of atrial contractions.

An atrial synchronous, ventricular inhibited pacemaker circuit for providing an electrical stimulus to a lead coupled to the ventricle of a heart at a time dependent on the rate of sensed electrical signal on a lead coupled to the atrium of said heart, each of which sensed signal manifests an atrial contraction, said circuit comprising:

• means for sensing said electrical signal on said lead coupled to said atrium;
• switch means coupled to said sensing means for entering a first state in response to said sensing means sensing said electrical signal on said lead coupled to said atrium;
• comparator means having a first input, a second input and an output, said output being coupled to said switching means to provide a signal to said switching means upon the voltage at said second input equaling the voltage at said first input, said switching means responding to said signal by entering a second state;
• means for providing a first reference voltage to said first comparator means input during the time said switching means is in said first state;
• first capacitive means coupled to said second comparator means input;
• means for providing a voltage to said first capacitive means while said switching means is in said first state to cause said first capacitive means to become charged, and thereby provide a voltage to said second comparator input;
• discharge path means responsive to said switching means being in said second state for switchably connecting a discharge path to said first capacitive means;
• oscillator means including second capacitive means which is charged to a second reference voltage over a given first time period and then discharged during a second time period, which is much less than said first time period;
• means for providing an electrical stimulus to said lead coupled to said ventricle upon sensing said second capacitive means has been charged to said second reference voltage;
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• means for providing a voltage related to the voltage to which said first capacitive means has charged to charge said second capacitive means.