Development of the Marseilles pulsatile rotary blood pump for permanent implantable left ventricular assistance.

We have developed a low-speed, double-lobed hypocycloidal pump that furnishes a pulsatile flow without valves. The pump is coupled to a specially designed electric motor. The motor/pump unit is totally implantable and has been extensively tested in vitro and in vivo in animals. Because this pump is volumetric, it is necessary to control speed precisely to avoid overpumping. Our control system, which is based on analysis of the motor current wave form, can detect and prevent negative pressures before they occur. The physical properties and hemocompatibility of several construction materials have been studied to determine their suitability for clinical use. These materials include a graphite substrate, titanium nitrate surface coating, boric carbon, and amorphous diamond. The pumps currently being tested are made of titanium, but clinical versions will be made of composite materials selected from this preliminary study. In vivo testing of this pump confirmed its good hemodynamic performance, low hemolysis rate, and biocompatibility (i.e., low heat, noise, and vibration levels). Animal experiments were terminated after 15 days because of mechanical failure related to the accumulation of blood components on moving parts. A new pump in which the mechanism is completely sealed from the blood flow has been designed and will soon be tested. If this sealed design is effective, the pump should be ready for use as a permanent implantable ventricular assistance device.