A new hydraulic heart assist device.

For the right drive of a hydraulic biventricular assist device (HBVAD), a new lightweight magnet with a permanent magnetic armature was constructed. A miniature optically incremental position sensor was developed, which is an integral part of the control loop of the driving unit, and was incorporated in the armature. Mock circulation tests proved the stability of the drive and showed the expected sensitivity to the preload pressure. In vivo experiments in calves were carried out in order to test its haemodynamic efficiency on a beating and on a fibrillating heart, and to test the mutual interaction of the left and right hydraulic assist devices (LVAD, RVAD) via the vascular system. Both drives were controlled independently, operating in the volume-controlled mode. For the modelling of a heart disease, the heart was blocked by the administration of verapamil (Isoptin). It could be shown that the HBVAD is able to maintain the circulation. Various tests with the left and/or right drive active showed distinct unloading effects for the natural heart and proved the mutual interaction of both drives via the vascular system. An inherent feature of the hydraulic drive system is its ability to be triggered by a (weakly) beating heart. The preload sensitivity of the HBVAD was tested by the administration of adrenaline. Similar reactions of the drives resulted for a beating and for a fibrillating heart, showing the regulation characteristic according to Starling's law.