There is provided a dual chamber pacemaker system and method for ventricular pacing to provide therapy for a patient with cardiomyopathy, this system being characterized by automatically adjusting the AV escape interval so that ventricular pace pulses are delivered at an AV delay which is optimized for HOCM and/or dialated cardiomyopathy therapy. The pacemaker system continually obtains and stores representations of a QRS wave characteristic such as duration, derived either directly from the QRS signal or from an FFRS signal, and compares duration data from one or more cycles to prior stored duration data. The system then adjusts the AV interval as a function of the duration comparison, and the direction of the last adjustment of AV escape interval. By this means, the AV escape interval is maintained at or just short of the onset of fusion, thereby automatically providing for optimally lengthened AV escape intervals consistent with full capture by the delivered ventricular pace pulse.