Self-calibration system for capture verification in pacing devices

Abstract

A cardiac pacing and sensing system includes a body implantable unit for generating tissue stimulation pulses and manipulating information based on sensed signals, and a catheter for transmitting pulses from the unit to a pacing electrode adjacent myocardial tissue. The unit incorporates circuitry for generating response values, one associated with each stimulation pulse, based on a predetermined characteristic or parameter of the signals evoked by the pulses. To evaluate the efficacy of the parameter in distinguishing capture versus non-capture, the stimulation pulses are generated according to a protocol of high energy pulses guaranteed to effect capture interspersed with low energy pulses guaranteed not to effect capture. Data, accumulated and sorted into separate 'capture' and 'non-capture' sets, provides respective capture and non-capture composite values. The ratio of the composite values is compared to a predetermined threshold, to generate an indication either accepting or rejecting the chosen parameter. A parameter, once accepted, can be employed in a self-test that either increments or decrements stimulation of signals to evaluate the capture threshold. Optionally, two or more designated parameters can be screened simultaneously and compared, with the most favorable ratio then being compared to the threshold.