A cardiac assist device synchronization system includes a cardiac assist device and an acoustic or accelerometer sensor that provides a signal input to the cardiac assist device indicative of aortic valve closure. The cardiac assist device is coupled to a mammalian aorta and includes an inflatable chamber and a fluid pump. A fluid conduit is in communication between the chamber and the pump to provide for selective inflation of the chamber. A pump controller triggers the pump in counter-pulsation to a mammalian heart upstream from the aorta. A process for synchronizing a cardiac assist device in counter-pulsation with a left ventricle includes locating an acoustic or accelerometer sensor within a thoracic cavity of a mammal having the assist device coupled to the aorta of the mammal. Through the measurement of an acoustic or acceleration property of an aortic valve of the mammal, and the transmission of aortic valve closure measurement through a controller for the cardiac assist device, counter-pulsatile synchronization for the cardiac assist device is achieved.