Patent ID: 7269458

Claim:
A cardiac device, comprising: one or more sensing channels for generating intra-cardiac electrogram signals; a controller for detecting intrinsic cardiac activity and measuring an intrinsic heart rate from the electrogram signals; an activity level sensor interfaced to the controller for measuring a parameter related to a patient's level of physical activity; wherein the controller is programmed to construct a historical record of activity level versus heart rate, referred to as a heart rate response profile; wherein the controller is programmed to compute a heart rate response slope from the heart rate response profile, defined as the ratio of an incremental change in intrinsic rate to an incremental change in measured activity level; wherein the controller is programmed to collect periodic maximum heart rates over time and derive a maximum intrinsic heart rate parameter therefrom indicative of the maximum heart rate the patient is able to attain; a pacing channel for pacing a cardiac chamber, wherein the controller is programmed to control the delivery of pacing pulses in accordance with a programmed mode; and, wherein the controller is programmed to switch to a rate-adaptive pacing mode if both the heart rate response slope and maximum intrinsic heart rate parameters have decreased below respective predefined limit values.