A cardiac assist device including a sleeve configured to externally wrap around a native, intact heart; a motor, and a drive shaft that connects the motor to the sleeve, wherein, actuation of the motor and the drive shaft provides a synchronized assisting force to a pumping force of the native, intact whole heart, thereby helping contraction and expansion of the heart located within an internal volume defined by the sleeve. Some embodiments relate to a system for synchronizing the cardiac assist device with a heart including the cardiac assist device; a power supply connected to the motor; and an electrical connector-relay configured to receive electrical signals from the pacemaker and to generate actuating signals that are relayed to the motor and the drive shaft, wherein, during operation of the system in a subject, the heart is assisted in contracting synchronously with the pacemaker signal rhythm.