Abstract: A heart actuator device for use in heart assist apparatus, which device includes a paddle-like main body. The main body has a heart compressing wall, which in use is adapted to be affixed to at least a region of heart, and a distal wall, which in use is adapted to be distal that region of the heart. The heart compressing wall is movable in a direction relatively away from the distal wall, so as, in use to compress at least that region of the heart thereby assisting movement of the heart wall.

Abstract: A method and system measure the instantaneous volume of blood contained within a chamber of a heart, irrespective of its shape, whereby stroke volume and cardiac output volume can be continuously monitored and feedback to a non-blood contacting cardiac assist device. In a preferred form the device uses the distances between the sensors which are implanted in a biomaterial that integrates with a heart surface to determine changes in heart volume. Sonomicrometry crystal measurements are disclosed as a preferred mode of obtaining distance readings. A computer readable medium carries instructions to convert data from dimension sensors into sensor positions within a predetermined coordinate system. Ventricular volume is based on the sensor positions.