1,253,928. Heart assist pump. UNITED STATES ENERGY COMMISSION. 8 Dec., 1969 [24 Dec., 1968], No. 59769/69. Heading A5R. [Also in Division F1] A heart assist pump for either implanted or external application in series with the heart and aorta, comprises a main body 14, and inlet and outlet tubes 12, 16, preferably constructed from polyurethane, and a pair of flexible walls 28, 32 attached to a piston head 34 dividing the body 14 into two chambers 24, 26 and connected to a controlling means by a rod 36 for synchronising the pump with the heart. A left ventricle pulse forces blood to flow along tube 12 through check valve 38 into chamber 24. The pressure compresses a bellows 78 connected by a fluid line 22 to a second bellows 76, which expands moving rod 82 upwards. Rod 82 is linked by a pin 84 to a rod 86 linked by pins 74 and 56 to rods 72, 36 respectively. The rod 86 lifts rod 72 and spool valve 58, allowing a fluid under pressure to pass from a manifold 73, through ports 64, 68 into the chamber above a control piston 52 mounted on the rod 36. The pressure increases and the control piston 52 is forced downwardly against a biassing spring 54 in a cylinder 48 and so forces the piston 34 and walls 28, 32 down, closing valve 44 and forcing blood from chamber 26 through valve 42. At the end of the left ventricle pulse, the pressure in chamber 24 drops, allowing bellows 78 to expand, which operates the spool valve 58 to allow the fluid in the chamber above the piston 52 to vent through ports 68, 66 to return the pistons 52, 34 to their starting positions. Valve 38 closes and blood is forced from chamber 24 to chamber 26 through the open valve 44.