Variable P-R interval pacemaker

Claim 2

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 a two input comparator circuit, a first input circuit coupled to one comparator input for maintaining that one input at a reference value and a second input circuit for providing a value to be compared with said reference value to the other input of said comparator circuit, said second input circuit including a variable value providing means for providing a value which increases at a first rate to said reference value from the time each atrial contraction is sensed and which decreases at a second rate from each time said reference value is reached until the next atrial contraction is sensed.

Claim 3

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.

Claim 4

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.

Claim 5

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.

Claim 6

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.

Claim 7

The invention according to claim 3 wherein said affecting means includes a two input comparator means having a reference voltage switchably applied to one input thereof and further having a capacitor coupled to the other input thereof, said capacitor being switchably charged and discharged to provide a voltage to said other input that is compared with said reference voltage; switch means for entering a first state in response to the sensing of an atrial contraction, said reference voltage being applied and said copacitor being charged during said first state, said comparator being coupled to said switch means to cause said switch means to enter a second state in response to said capacitor being charged to said reference voltage, said reference voltage not being applied and said capacitor discharging during said second state; and means for applying the voltage stored by said capacitor to said oscillator means during the time said switching means is in said first state to cause said oscillator means to provide a pulse when said capacitor becomes charged to said reference voltage.

Claim 8

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; and means for providing a voltage related to the voltage to which said first capacitive means has charged to charge said second capacitive means.

Claim 9

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; and means for providing a voltage related to the voltage to which said first capacitive means has charged to charge said second capacitive means.

Claim 10

The invention according to claim 5 wherein said relation between said voltage to which said first capacitive means is charged and the voltage applied by said last mentioned means to said second capacitive means is such that when said first capacitive means is charged to said first reference voltage, said second capacitive means will be charged to said second reference voltage.

Claim 11

The invention according to claim 6 wherein said first reference voltage equals or slightly exceeds said second reference voltage.

Claim 12

The invention according to claim 5: wherein said comparator means is a differential amplifier; and wherein said switching means is a transistor which is initially rendered conductive by a sensed signal on the atrium lead and maintained conductive by the output signal from one side of said differential amplifier.

Claim 13

The invention according to claim 5 wherein said circuit further comprises: means for sensing the occurrence of an electrical signal on said ventricle lead caused by a ventricular contraction of the heart and for providing a signal manifesting such signal sensing; means for providing said signal to said comparator means and said oscillator means, said comparator means and said oscillator means, said comparator means responding to said ventricle lead sensing means signal by providing a signal to said switching means to which said switching means responds by entering said second state, said oscillator means responding to said ventricle lead sensing means signal by said second capacitive means discharging.

Claim 14

The invention according to claim 9 wherein said means for sensing said atrial lead signals includes refractory means for preventing the sensing of a subsequent signal during a certain refractory time period; and wherein said means for sensing said ventricle lead signals includes means coupled to said means for sensing atrial lead signals to activite said refractory means to commence said refractory time.