An implantable medical interventional device (10) is responsive to detection of any of a plurality of cardiac dysrhythmias in a human patient by performing an appropriate therapy including cardiac pacing, cardioversion or defibrillation according to the nature of the detected dysrhythmia. The device includes a first sensor means (13, 21) for detecting any of the plurality of cardiac dysrhythmias, and a generator (15, 20) for developing pulses and shocks for delivery to the patient's heart according to whether a detected dysrhythmia is bradycardia or a relatively slow pathologic tachycardia on the one hand, or a relatively fast tachycardia or fibrillation on the other hand. An optimizer (22, 24) in the device seeks to maintain at all times a substantial match of the patient's heart rate to the normal rate for a healthy person under like conditions of physical exercise, including relatively minor activity, and rest experienced by the patient. The optimizer includes a second sensor (30) to detect when the patient is engaged in physical exercise or rest as imposing different hemodynamic demands on the patient's cardiovascular system, and to produce a signal representative of the then-current hemodynamic demand. A signal processor (31) of the device enhances the signal to distinguish components thereof representing true physical exercise by the patient and the extent of such exercise from components of the signal constituting false indications of activity by the patient. The enhanced signal is applied to the generator (15) to develop pulses for delivery to the patient's heart to vary the heart rate to conform to the then-current hemodynamic demand on the patient attributable to the conditions of physical exercise or rest. In that way, the device focuses on correction of cardiac pacing problems before they become sufficiently aggravated to require more aggressive cardioversion and defibrillation therapies.