Rate adaptive pacemaker apparatus and method

Claim 2

Demand pacer apparatus for pacing a patient, having stimulus means for delivering stimulus pulses, sensing means for sensing natural heartbeats, and inhibiting means for inhibiting delivery of stimulus pulses when natural heartbeats are sensed, comprising: QT means for sensing the QT interval of a pacer cycle; rate means for modifying the rate of delivery of stimulus pulses by said stimulus means as a sensitivity function of said sensed QT interval; and further comprising patient history means for accumulating patient history data over a plurality of pacer cycles, and sensitivity control means automatically operative following cessation of inhibited operation for controlling said sensitivity function in accordance with said accumulated patient history data.

Claim 3

The demand pacer apparatus as described in claim 1, wherein said patient history means comprises means for processing said sensed natural heartbeats to obtain the patient's natural rate, and wherein said sensitivity control means further comprises means for changing said sensitivity function only when the pacing rate differs from said obtained natural rate by more than a predetermined limit.

Claim 4

The apparatus as described in claim 2, wherein said rate means comprises means for decreasing said pacing interval at a predetermined rate following sensing of a natural heartbeat, whereby said pacer rate rises so that a stimulus pulse is delivered after one or more naturally occurring heartbeats and said QT interval is again measured.

Claim 5

Demand pacer apparatus having stimulus means for delivering stimulus pulses, sensing means for sensing natural heartbeats, and inhibiting means for inhibiting delivery of stimulus pulses when natural heartbeats are sensed, comprising: QT means for sensing the QT interval following each delivered stimulus; rate means for modifying the pacing interval of said stimulus means as a correlation function of said sensed QT intervals; overdrive means for decreasing the escape interval of said stimulus means whenever inhibited operation occurs so as to overdrive the natural rate and deliver a stimulus pulse, whereby the QT interval can be sensed and said rate means can modify the pacing interval in accordance with at least one sensed Q-T interval; and pacing interval increasing means for increasing the pacing interval by a predetermined amount d following each delivered stimulus pulse.

Claim 6

Demand pacer apparatus having stimulus means for delivering stimulus pulses, sensing means for sensing natural heartbeats, and inhibiting means for inhibiting delivery of stimulus pulses when natural heartbeats are sensed, comprising: QT means for sensing the QT interval following each delivered stimulus; rate means for modifying the pacing interval of said stimulus means as a correlation function of said sensed QT intervals; overdrive means for decreasing the escape interval of said stimulus means whenever inhibited operation occurs so as to overdrive the natural rate and deliver a stimulus pulse, whereby the QT interval can be sensed and said rate means can modify the pacing interval in accordance with at least one sensed Q-T interval; and pacing interval increasing means for increasing the pacing interval by a predetermined amount d following each delivered stimulus pulse.

Claim 7

The demand pacer apparatus as described in claim 4, wherein said overdrive means further comprises means for decreasing said escape interval following each sensed natural heartbeat until a stimulus is delivered.

Claim 8

The demand pacer apparatus as described in claim 4, wherein said overdrive means further comprises means for detecting when a plurality of consecutive natural heartbeats has been sensed and means for delivering an early stimulus only when said plurality has been sensed.

Claim 9

Demand pacer apparatus having stimulus means for delivering stimulus pulses to a patient and inhibiting means for sensing natural heartbeats and inhibiting delivery of stimulus pulses from said stimulus means when natural heartbeats are sensed, comprising rate means for sensing at least one variable of said patient and for modifying the pacing rate of said stimulus means during delivery of stimulus pulses as a function of said sensed variable, comparison means operative whenever one or more stimulus pulses are delivered by said stimulus means following inhibited operation of said pacer for comparing said modified pacing rate and the rate of natural heartbeats during said inhibited operation, and adjusting means for adjusting said function in accordance with said comparison.

Claim 10

Demand pacer apparatus having stimulus means for delivering stimulus pulses to a patient and inhibiting means for sensing natural heartbeats and inhibiting delivery of stimulus pulses from said stimulus means when natural heartbeats are sensed, comprising rate means for sensing at least one variable of said patient and for modifying the pacing rate of said stimulus means during delivery of stimulus pulses as a function of said sensed variable, comparison means operative whenever one or more stimulus pulses are delivered by said stimulus means following inhibited operation of said pacer for comparing said modified pacing rate and the rate of natural heartbeats during said inhibited operation, and adjusting means for adjusting said function in accordance with said comparison.

Claim 11

The demand pacer apparatus as described in claim 7, wherein said variable is the Q-T interval of said patient and said function is the correlation of pacing rate and Q-T interval.

Claim 12

The demand pacer apparatus as described in claim 8, wherein said comparison means comprises means for making said comparison during the pacing cycle following the first delivered stimulus after inhibited operation.