A ventricular assist device incorporating a rotary pump (3) such as a rotary impeller pump implantable in fluid communication with a ventricle and an artery to assist blood flow from the ventricle to the artery. The device includes a pump drive circuit (6) supplying power to the pump, one or more sensors (10) for sensing one or more electrophysiological signals such as electrogram signals in and a signal processing circuit (23) connected to the sensors and to the pump drive circuit. The signal processing circuit is operative to detect the sensor signals and control power supplied to the pump from the pump drive circuit so that the pump runs in a normal sinus rhythm mode, with a varying speed synchronized with the cardiac cycle. When a bradycardia arrhythmia is detected, the pump drive circuit may also nm the pump in a sinus bradycardia mode or a heart block mode different from the normal sinus rhythm mode.
