Electronic capture detection for a pacer

Abstract From the Canadian patent

A pacemaker sense amplifier which includes active circuitry which establishes and attempts to maintain a constant field density between two electrodes effectively, clamping them together at substantially fixed relative electrical potential. The amount of current or power provided to the electrodes is monitored and forms the basis of detection of the passing cardiac depolarization wavefront. A timer is used to define a detection window after the generation of a pacing pulse. The occurrence of a detected depolarization within the detection window indicates that the pacing pulse has captured the heart.