An apparatus comprises an implantable ventricular depolarization sensing circuit configured to provide a sensed ventricular depolarization signal, a timer circuit configured to provide a ventricular time interval between ventricular depolarizations, and a controller circuit communicatively coupled to the ventricular depolarization sensing circuit and the timer circuit. The controller circuit includes a ventricular tachycardia (VT) detection circuit configured to declare an episode of VT when a number of accelerated beats are detected, calculate a hysteresis VT detection threshold interval, and deem whether the episode of VT persists using the hysteresis VT detection threshold interval.