An implantable electromechanical ventricular assist system (VAS) intended for permanent human use was developed. It consisted of a conically shaped pumping chamber, a polyolefin (Hexsyn) rubber diaphragm attached to a pusherplate, and a compact actuator with a direct current brushless motor and a planetary rollerscrew. The outer diameter was 97 mm, and the total thickness was 70 mm. This design was chosen to give a stroke volume of 63 ml. The device weighs 620 g, with a total volume of 360 ml. The pump can provide 8 L/min flow against 120 mmHg afterload with a preload of 10 mmHg. The inner surface of the device, including the pumping chamber and diaphragm, was made biocompatible with a dry gelatin coating. To date, two subacute (2 and 6 day) calf studies have been conducted. The pump showed reasonable anatomic fit inside the left thorax, and the entire system functioned satisfactorily in both the fill-empty mode using the Hall effect sensor signals and the conventional fixed rate mode. There were no thromboembolic complications despite no anticoagulation therapy. The system now is being endurance tested > 10 weeks (9 million cycles). This VAS is compact, low noise, easy to control, and has excellent biocompatibility.
©1991 American Society of Artificial Internal Organs
