An implantable electronic therapy device, having a therapy unit, a heart rate capturing unit, a contractility determination unit, and an evaluation and control unit. The therapy unit delivers an antitachycardiac therapy. The heart rate capturing unit determines a ventricular heart rate from an input signal, and the contractility determination unit generates from an input signal, a contraction signal reflecting a contractility of a ventricle. The evaluation and control unit is connected to the therapy unit, the heart rate capturing unit, and the contractility determination unit actuates the therapy unit to administer an antitachycardiac therapy when the heart rate capturing unit detects an increase in the heart rate above a specified threshold value and the contractility determination unit supplies a contraction signal which is not physiologically adequate for the increase in the heart rate.
