A left-ventricular assist device (LVAD) has a generally ellipsoidal capsule fitted into a patients ventricle, formed of a cage or frame of shape-memory wire which can be twisted open and shut to expand and collapse a thin membrane, to inflate with the incoming blood during diastole and to contract and squeeze out the blood during systole. A catheter extends from outside the patients body through a major blood vessel and the patients aortal valve into the left ventricle. The catheter has an external sheath, an outer tubular shaft onto which proximal ends of the shape-retaining wires are affixed, and a middle shaft extending through the hollow core of the outer shaft and which is affixed to a central shaft of the capsule. A control console has mechanical geared drives coupled to the outer and middle catheter shafts within the catheter. A sensor arrangement synchs action of the LVAD with systole and diastole of the patients heart.