Cardiac pacer and method providing means for periodically determining capture threshold and adjusting pulse output level accordingly
First Claim
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1. A cardiac pacer for stimulating contractions in a patient heart having a recurring refractory period of predetermined minimum duration, comprising:
- means for establishing a pacing period within the refractory period of the heart;
pacing pulse generating means for generating a series of pacing signals for application to the heart, said generating means having a first operating mode wherein each of said pacing signals comprises a single pulse occurring during said refractory period, and a second operating mode wherein each of said signals comprises a pair of pulses occuring during said pacing period, the energy level of said pulses in said first operating mode being dependent on an applied amplitude control signal;
means defining recurring test periods;
pacer control means for conditioning said pacing pulse generating means to said second operating mode during each of said test periods;
capture thereshold detection means responsive to contractions within the heart induced by paired pulses from said generating means during said second mode of operation thereof, periodically operable during each of said recurring test periods for automatically determining the minimum pacing pulse energy required during each of said test periods to reliably stimulate contractions in the patient heart; and
amplitude control means responsive to said capture threshold detection means for providing following each of said test periods an amplitude control signal to said pacing pulse generating means to cause said generating means to thereafter generate pacing pulses having an energy level related to said capture threshold.
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Abstract
A low-power cardiac pacer and method includes an automatic capture threshold determination system wherein the minimum pulse energy required to reliably stimulate contractions of a patient'"'"'s heart is periodically determined. The energy level of pacing pulses generated by the pacer is automatically set in accordance with the determined capture threshold level to reduce battery current drain and thereby extend the pacer'"'"'s useful life.
268 Citations
12 Claims
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1. A cardiac pacer for stimulating contractions in a patient heart having a recurring refractory period of predetermined minimum duration, comprising:
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means for establishing a pacing period within the refractory period of the heart; pacing pulse generating means for generating a series of pacing signals for application to the heart, said generating means having a first operating mode wherein each of said pacing signals comprises a single pulse occurring during said refractory period, and a second operating mode wherein each of said signals comprises a pair of pulses occuring during said pacing period, the energy level of said pulses in said first operating mode being dependent on an applied amplitude control signal; means defining recurring test periods; pacer control means for conditioning said pacing pulse generating means to said second operating mode during each of said test periods; capture thereshold detection means responsive to contractions within the heart induced by paired pulses from said generating means during said second mode of operation thereof, periodically operable during each of said recurring test periods for automatically determining the minimum pacing pulse energy required during each of said test periods to reliably stimulate contractions in the patient heart; and amplitude control means responsive to said capture threshold detection means for providing following each of said test periods an amplitude control signal to said pacing pulse generating means to cause said generating means to thereafter generate pacing pulses having an energy level related to said capture threshold. - View Dependent Claims (2, 6, 7)
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3. A cardiac pacer for stimulating contractions in a patient heart having a recurring refractory period of predetermined minimum duration, comprising:
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pacing pulse generating means for generating recurring pacing signals for application to the heart, said pacing means having a first operating mode wherein each signal comprises a single pulse, and a second operating mode wherein each signal comprises a pair of closely spaced pulses; means defining recurring test periods; pacer control means for conditioning said pacing pulse generating means to said second operating mode during said recurring test periods; capture threshold detection means responsive to contractions of the heart in response to said closely spaced pulses during each of said test periods for determining the capture threshold of the heart; and amplitude control means for causing said generating means to generate pacing pulses at an energy level related to said determined capture threshold during said first mode of operation. - View Dependent Claims (4, 5)
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8. A power-conservative method of pacing a patient heart comprising the steps of:
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defining first and second operating modes; generating recurring pacing signals for application to the heart wherein, said pacing signals each comprising a single pacing pulse in said first mode of operation, and a pair of closely spaced pulses in said second mode of operation; periodically analyzing contractions to the heart resulting from the closely spaced double pacing pulses in said second mode to determine the capture threshold of the heart; and maintaining the amplitude of said pacing pulses at an amplitude related to said capture threshold during said first mode of operation. - View Dependent Claims (9, 10, 11, 12)
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Specification