An assembly of devices intended to assist a damaged or weakened heart (e.g., one affected by cardiogenic shock) to pump blood. It includes a electrically-powered external pump, an atrial or ventricular cannula to draw blood outside the body, a cannula to deliver the blood back to the aorta or pulmonary artery (depending on left or right ventricular assistance), and a unit that controls pump operation. It is typically intended to be used as a bridge to heart transplantation; it is not intended for cardiopulmonary bypass.