Patent ID: 6963775

Claim:
A cardiac pacemaker, comprising: a plurality of sensing/pacing channels, each such channel comprising an electrode for disposing near a chamber of a heart, a pulse generator for outputting pacing pulses, and a sense amplifier for detecting sense signals; a controller for controlling the operation of the pulse generators in response to sensed events and lapsed time intervals and in accordance with a programmed pacing mode; an evoked response sensing channel comprising a sense amplifier for sensing an evoked response generated after a pacing pulse; a switching circuit for switching an input of the evoked potential sensing channel to a selected electrode of the sensing/pacing channels; wherein the controller is programmed to perform a capture verification test at a selected time to test a selected sensing/channel for presence or loss of capture, the capture verification test being performed by sensing whether an evoked response occurs during a capture detection window following the output of a pacing pulse; and, wherein the controller is programmed to determine a pacing threshold of a sensing/pacing channel at a selected time by: a) performing a capture verification test on the channel; b) raising or lowering a pacing pulse energy by a specified amount if capture was present or absent, respectively, during the preceding capture verification test; c) repeating the capture verification test with the raised or lowered pacing pulse energy; d) determining the pacing threshold as the unlowered pacing pulse energy if the pacing pulse energy was lowered at step b and a loss of capture occurred during the repeated capture verification test, or repeating steps b through d otherwise.