An artificial heart device for producing heart pumping action as part of a total artificial heart implant comprising a housing of elongate configuration enclosing a pumping volume of sufficient capacity to provide adequate blood flow within the living being. A deformable diaphragm structure is attached at its perimeter to an interior housing surface approximately at the largest perimeter of the pumping volume to form a deformable partition deviding the pumping volume into a blood chamber and a drive chamber. The diaphragm structure has a modified hemi-ellipsoidal configuration when fully extended, modification being represented by four sections of substantially equal quadrants formed by intersection of the diaphragm structure with two orthogonal planes oriented in parallel relationship with the vertical axis. The curvature of each medial section of each quadrant is reduced or flattened to form a medial section having a lower profile as compared to surrounding ellipsoidal curvature. This structure reduces occurrence of bi-axial folding and enhancing random folding activity within the diaphragm. Valve inlet and outlet means are coupled to the housing in communication with the blood flow chamber for attachment along with the circulatory system of a living being. Pumping means are provided for actuating alternating extension and collapse of the diaphragm structure with respect to the drive chamber to simulate pumping action of the natural heart.