Patent ID: 7142920

Claim:
A cardiac rhythm management 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 exertion level sensor interfaced to the controller for measuring a physiological parameter related to metabolic demand; and, wherein the controller is programmed to: record a plurality of a patient's actual intrinsic heart rates along with corresponding measured exertion levels over a period of time; associate the actual heart rates with predicted heart rates for the corresponding measured exertion levels as calculated in accordance with a physiological model; calculate a parameter reflecting the variability between the actual heart rates and the predicted heart rates; compare the variability between the actual and predicted heart rates with a precomputed baseline variability; and, determine that a change in chronotropic status has occurred if the variability between the actual and predicted heart rates exceeds the baseline variability by a specified threshold.