Temperature-based, rate-modulated cardiac therapy apparatus and method

Abstract

A temperature-based, rate-modulated cardiac pacemaker having means for variably controlling the stimulation rate of the heart according to multiple temperature characteristics of the blood referenced to multiple moving baseline temperatures. A target rate is periodically calculated by obtaining a weighted sum of the following rate components: (1) the magnitude of a decrease in temperature below resting temperature, a first moving baseline, (2) the magnitude of an increase in temperature above a local minimum temperature, a second moving baseline, (3) the magnitude of an increase in the resting baseline above a daily minimum temperature, a third moving baseline, and (4) the absolute value of the rate of change of temperature. The resting temperature is preferably calculated over a longer interval than the local minimum temperature but a much shorter interval than the daily minimum temperature. A positive rate of change of temperature is distinguished from a negative rate of change of temperature and is used differently in the calculation of target rate. The target rate is not directly applied as the new pacing rate but is instead averaged with the previous rate in order to provide smoother transitions between pacing rates. An intermediate rate limit is included in addition to lower and upper rate limits, and rank filtering is employed in the determination of rate components.