Inhibited demand pacer with a two-rate pulse generator

Claim 2

An inhibited demand pacer comprising means for generating stimulating pulses suitable for stimulating heartbeats, means for monitoring natural heartbeats by detecting electrical impulses, and means for inhibiting the generating means during detection of electrical impulses above a first threshold frequency and below a second threshold frequency including means establishing said first and second threshold frequencies, said generating means, in the absence of detection of electrical impulses at frequencies higher than the first threshold frequency, generating stimulating pulses at a first, normal stimulating frequency, and, in response to detection by the monitoring means of electrical impulses above the second threshold frequency, generating stimulating pulses at a second, stimulating frequency higher than the first, normal stimulating frequency.

Claim 3

A pacer according to claim 1 in which the monitoring means includes an amplifier for passing a selected frequency bandwidth of the natural heartbeat electrical waveform, and a trigger circuit connected to said amplifier for triggering the inhibiting means in response to detection of a predetermined feature of the heartbeat waveform.

Claim 4

A pacer according to claim 1 in which the generating means includes an oscillator having periodic cycle at the end of which a stimulating pulse is generated, and in which the inhibiting means includes means for resetting the oscillator back to the commencement of its said periodic cycle to prevent the generation of a stimulating pulse.

Claim 5

A pacer according to claim 3 in which the inhibiting means includes a monostable multivibrator connected to be triggered from its quiescent state to its on state by the detection of an electrical impulse by the monitoring means, the output of the multivibrator being fed to the resetting means to operate the resetting means upon switching of the multivibrator from one state to another.

Claim 6

A pacer according to claim 4 in which the construction and period of the multivibrator is such that the detection of electrical impulses by the monitoring means above the second frequency threshold maintains the multivibrator in its on state to suspend operation of the resetting means.

Claim 7

A pacer according to claim 5 in which the inhibiting means includes means responsive to the multivibrator being maintained in the on state longer than a predetermined time interval, and operative upon occurrence of such a state to feed to the generating means a frequency shift signal causing the generating means to generate stimulating pulses at the said higher stimulating frequency.

Claim 8

An inhibited demand pacer comprising means for generating stimulating pulses suitable for stimulating heartbeats, including an oscillator having a periodic cycle at the end of which a stimulating pulse is generated two capacitive elements means for transferring charge into or out of the capacitive elements at a substantially constant rate, two additional means connected to transfer substantially instantaneously charge out of or into the capacitive elements depending upon the sense of transfer provided by the said transferring means, and means for isolating one of the capacitive elements, one of the additional means being arranged to conduct when the charge across it reaches a predetermined level and by such conduction to cause the generation of a stimulating pulse, and the other additional means being connected to receive the output of the resetting means and being arranged to conduct on receipt of a signal froM the resetting means, the means for isolating one of the capacitors operating during detection by the monitoring means means for monitoring natural heartbeats by detecting electrical impulses, and means for inhibiting the generating means during detection of electrical impulses above a first threshold frequency and below a second threshold frequency, including means for establishing said first and second threshold frequencies and means for resetting the oscillator back to the commencement of its periodic cycle to prevent the generation of a stimulating pulse.

Claim 9

An inhibited demand pacer comprising means for generating stimulating pulses suitable for stimulating heartbeats, including an oscillator having a periodic cycle at the end of which a stimulating pulse is generated two capacitive elements means for transferring charge into or out of the capacitive elements at a substantially constant rate, two additional means connected to transfer substantially instantaneously charge out of or into the capacitive elements depending upon the sense of transfer provided by the said transferring means, and means for isolating one of the capacitive elements, one of the additional means being arranged to conduct when the charge across it reaches a predetermined level and by such conduction to cause the generation of a stimulating pulse, and the other additional means being connected to receive the output of the resetting means and being arranged to conduct on receipt of a signal froM the resetting means, the means for isolating one of the capacitors operating during detection by the monitoring means means for monitoring natural heartbeats by detecting electrical impulses, and means for inhibiting the generating means during detection of electrical impulses above a first threshold frequency and below a second threshold frequency, including means for establishing said first and second threshold frequencies and means for resetting the oscillator back to the commencement of its periodic cycle to prevent the generation of a stimulating pulse.

Claim 10

A pacer according to claim 1 in which the first threshold frequency is a frequency in the range 55 to 75 pulses per minute.

Claim 11

A pacer according to claim 1 in which the second threshold frequency is a frequency in the range 200 to 400 pulses per minute.

Claim 12

A pacer according to claim 1 in which the said normal stimulating frequency is a frequency in the range 65 to 75 pulses per minute.

Claim 13

A pacer according to claim 1 in which the said higher stimulating frequency is a frequency in the range 95 to 110 pulses per minute.

Claim 14

A pacer according to claim 1 in which the second threshold frequency is 300 pulses per minute, the normal stimulating frequency is 70 pulses per minute and the higher stimulating frequency is 100 pulses per minute.

Claim 15

A pacer according to claim 1 in which the first threshold frequency is equal to the normal stimulating frequency.

Claim 16

An inhibited demand pacer comprising: means for generating stimulating pulses at a first normal stimulating frequency and at a second higher stimulating frequency suitable for stimulating heartbeats, means for monitoring natural heartbeats by detecting electrical impulses, inhibiting means responsive to said monitoring means for inhibiting said generating means during detection of electrical impulses above a first threshold frequency and below a second threshold frequency, and for supplying a control signal to said generating means in response to detection by said monitoring means of electrical impulses above said second threshold frequency, said generating means being operative in response to said control signal to generate stimulating pulses at a second stimulating frequency higher than said first, normal stimulating frequency, said inhibiting means including means for establishing said first and second threshold frequencies.

Claim 17

An inhibited demand pacer comprising: means for generating stimulating pulses at a first normal stimulating frequency and at a second higher stimulating frequency suitable for stimulating heartbeats, means for monitoring natural heartbeats by detecting electrical impulses, inhibiting means responsive to said monitoring means for inhibiting said generating means during detection of electrical impulses above a first threshold frequency and below a second threshold frequency, and for supplying a control signal to said generating means in response to detection by said monitoring means of electrical impulses above said second threshold frequency, said generating means being operative in response to said control signal to generate stimulating pulses at a second stimulating frequency higher than said first, normal stimulating frequency, said inhibiting means including means for establishing said first and second threshold frequencies.

Claim 18

A pacer according to claim 14, in which the monitoring means includes an amplifier for passing a selected frequency bandwidth of the natural heartbeat electrical waveform, and a trigger circuit responsive to said amplifier for triggering the inhibiting means in response to detection of a predetermined feature of the heartbeat waveform.

Claim 19

A pacer according to claim 14, in which the generating means includes two capacitive elements, charge transferring means for transferring charge into or out of the capacitive elements at a substantially constant rate, first and second devices connected to transfer substantially instantaneously charge out of or in to the capacitive elements depending upon the sense of transfer provided by said charge transferring means, means for isolating one of the capacitive elements, pulse generating means responsive to said first device and arranged to generate a stimulating pulse when said first device conducts, said first device being arranged to conduct when the voltage across it reaches a predetermined level, and said second device being connected to receive the output of the resetting means, said means for isolating one of said capacitors being arranged responsive to the monitoring means to operate during detection by the monitoring means of impulses above said second threshold frequency.