Passive hysteresis circuit demand pacer

Claim 2

A pacer comprising electrode means for connection to a patient''s heart, pulsing means for applying a stimulating pulse to said electrode means, means for detecting a signal on said electrode means responsive to a beating of said patient''s heart, switch means having first and second terminals, means responsive to the detection of a beating action of said patient''s heart for causing the voltage at said first terminal to start rising continuously from an initial low lever, means for applying a reference potential to said second terminal, means responsive to the voltage at said first terminal exceeding the voltage at said second terminal by an amount sufficient to trigger said switch means for controlling the operation of said pulsing means, and passive reference potential changing means connected to said second terminal for alone decreasing said reference potential responsive to each triggering of said switch means and for continuously increasing said reference potential until a predetermined maximum value is reached in the absence of the triggering of said switch means.

Claim 3

A pacer in accordance with claim 1 wherein said reference potential applying means includes a potential source, voltage divider means connected across said potential source and having a tap thereon, and means for connecting said tap to said second terminal, and said passive reference potential changing means includes capacitor means coupled between said second terminal and one end of said voltage divider means.

Claim 4

A pacer in accordance with claim 2 wherein said voltage divider means and said passive reference potential changing means control said reference potential to vary between two extreme limits, and the magnitude of said capacitor means is selected to provide a time constant that requires at least two seconds for the reference potential to change from one extreme limit to the other in the presence of continuously generated stimulating pulses or the presence of continuously detected spontaneous beats of said patient''s heart.

Claim 5

A pacer in accordance with claim 1 wherein said passive reference potential changing means includes means for causing said reference potential to change from one extreme limit to the other in no less than two seconds in the presence of continuously generated stimulating pulses or in the presence of continuously detected spontaneous beats.

Claim 6

A pacer in accordance with claim 4 wherein said passive reference potential changing means includes means for causing said reference potential to change from one extreme limit to the other in no more than six seconds in the presence of continuouslY generated stimulating pulses or in the presence of continuously detected spontaneous beats.

Claim 7

A pacer comprising electrode means for connection to a patient''s heart, pulsing means for applying a stimulating pulse to said electrode means, means for detecting a beating of said patient''s heart, first and second terminals, means responsive to a beating action of said patient''s heart for causing the voltage at said first terminal to start changing continuously in the same direction from an initial level at one extreme toward a final level at another extreme, means for applying a reference potential to said second terminal, comparator means responsive to the voltages at said first and second terminals differing from each other by less than a predetermined amount for controlling the operation of said pulsing means, and passive means for alone changing in a first direction the reference potential of said second terminal responsive to each operation of said comparator means and for then continuously and gradually restoring in the direction opposite to said first direction said reference potential.

Claim 8

A pacer comprising electrode means for connection to a patient''s heart, pulsing means for applying a stimulating pulse to said electrode means, means for detecting a beating of said patient''s heart, first and second terminals, means responsive to a beating action of said patient''s heart for causing the voltage at said first terminal to start changing continuously in the same direction from an initial level at one extreme toward a final level at another extreme, means for applying a reference potential to said second terminal, comparator means responsive to the voltages at said first and second terminals differing from each other by less than a predetermined amount for controlling the operation of said pulsing means, and passive means for alone changing in a first direction the reference potential of said second terminal responsive to each operation of said comparator means and for then continuously and gradually restoring in the direction opposite to said first direction said reference potential.

Claim 9

A pacer in accordance with claim 6 wherein said reference potential applying means includes a potential source, voltage divider means connected across said potential source and having a tap thereon, and means for connecting siad tap to said second terminal, and said passive reference potential changing means includes capacitor means coupled between said second terminal and one end of said voltage divider means.

Claim 10

A pacer in accordance with claim 7 wherein the magnitude of said capacitor means is selected to provide a time constant that requires at least two seconds for said reference potential to be restored in the presence of continuously detected spontaneous beats of said patient''s heart.

Claim 11

A pacer in accordance with claim 6 wherein said passive reference potential varies between two limits and said reference potential changing means includes means for causing said reference potential to change from one limit to the other in no less than 2 seconds in the presence of continuously generated stimulating pulses or in the presence of continuously detected spontaneous beats.

Claim 12

A pacer in accordance with claim 9 wherein said passive reference potential changing means includes means for causing said reference potential to change from one extreme limit to the other in no more than six seconds in the presence of continuously generated stimulating pulses or in the presence of continuously detected spontaneous bests.

Claim 13

A pacer comprising electrode means for connection to a patient''s heart, pulsing means for generating a stimulating pulse on said electrode means, means for deriving a reference potential, means for deriving a timing potential which changes continuously in the same direction from an initial value starting with the occurrence of a beating action of said patient''s heart, means responsive to a predetermined difference between said timing and reference potentials for operating said pulsing means, and passive means operative alone when a stimulating pulse is generated on said electrode means for first controlling a change in said reference potential in one direction and then controlling a gradual and continuous change in it in the opposite direction.

Claim 14

A pacer comprising electrode means for connection to a patient''s heart, pulsing means for generating a stimulating pulse on said electrode means, means for deriving a reference potential, means for deriving a timing potential which changes continuously in the same direction from an initial value starting with the occurrence of a beating action of said patient''s heart, means responsive to a predetermined difference between said timing and reference potentials for operating said pulsing means, and passive means operative alone when a stimulating pulse is generated on said electrode means for first controlling a change in said reference potential in one direction and then controlling a gradual and continuous change in it in the opposite direction.

Claim 15

A pacer in accordance with claim 11 wherein said reference potential can vary between two extreme limits and said passive means controls a change in said reference potential from one extreme limit to the other extreme limit in no less than 2 seconds.

Claim 16

A pacer in accordance with claim 11 wherein said reference potential can vary between two extreme limits and said passive means controls a change in said reference potential from one extreme limit to the other extreme limit in no more than 6 seconds.

Claim 17

A demand pacer for stimulating the heart of a patient comprising terminal means for connection to said heart, heartbeat detection means connected to said termInal means for detecting the presence and absence of a spontaneous heartbeat within a first predetermined interval from the most previous heartbeat, pulse generating means responsive to the operation of said detection means detecting the absence of said spontaneous heartbeat for benerating a stimulation impulse on said terminal means, and passive-component gradual-interval-variation control means responsive to the operation of said pulse generating means for alone controlling each interval between successive stimulation impulses to be progressively less than the most previous interval but not to be less than a second predetermined interval and responsive to the operation of said detecting means detecting the presence of each successive said spontaneous heartbeat for alone controlling each interval between each successive said spontaneous heartbeat and the next stimulation impulse to be progressively more than the most previous interval but no greater than said first predetermined interval.

Claim 18

A demand pacer for stimulating the heart of a patient comprising terminal means for connection to said heart, heartbeat detection means connected to said termInal means for detecting the presence and absence of a spontaneous heartbeat within a first predetermined interval from the most previous heartbeat, pulse generating means responsive to the operation of said detection means detecting the absence of said spontaneous heartbeat for benerating a stimulation impulse on said terminal means, and passive-component gradual-interval-variation control means responsive to the operation of said pulse generating means for alone controlling each interval between successive stimulation impulses to be progressively less than the most previous interval but not to be less than a second predetermined interval and responsive to the operation of said detecting means detecting the presence of each successive said spontaneous heartbeat for alone controlling each interval between each successive said spontaneous heartbeat and the next stimulation impulse to be progressively more than the most previous interval but no greater than said first predetermined interval.