Rate-Responsive Pacing Mimicking Ventricular Tachycardia.

: We describe 2 patients with rate-responsive permanent ventricular pacemakers who developed upper rate pacing while at rest. In one patient this occurred during chest physiotherapy and in the other as a result of muscle fasciculations. In both cases, the paced rhythm was misdiagnosed as ventricular tachycardia. Reprogramming of the pulse generators prevented further inappropriate rapid pacing.