Rate-responsive pacemaker having automatic sensor threshold with

Abstract

A programmable offset is added to an automatically generated baseline reference value to provide a Threshold value used by the rate-responsive sensor processing circuits of an implantable rate-responsive pacemaker to determine the significance of a sensor input signal. The rate-responsive pacemaker provides stimulation pulses on demand at a pacing rate determined by a sensed physiological parameter. The physiological parameter is sensed by a physiological sensor included within, or coupled to, the rate-responsive pacemaker. The physiological sensor generates a sensor input signal having a magnitude that varies as a function of the sensed physiological parameter. The invention provides a way for the rate-responsive pacemaker, when operating in an autothreshold mode, to automatically determine when the magnitude of the sensor input signal is sufficiently large to justify an increase in the pacing rate. A long-term running average of the sensor input signal is continuously maintained, and is used as a baseline threshold value. A programmable offset is added to the baseline reference value. Any sensor input signal that exceeds the baseline reference value plus the programmable offset is considered to be sufficiently large to effect an increase in the pacing rate.