SMALL, LOW-COST IMPLANTABLE CENTRIFUGAL PUMP FOR SHORT-TERM CIRCULATORY ASSISTANCE

Background. In 1991, Allegheny General Hospital and Allegheny-Singer R esearch Institute purchased a centrifugal pump, then a 2-year-old tech nology, from Medtronic Bio-Medicus, as part of its research program fo r novel treatments of acute and chronic heart failure. During a 4-year development program, we then established and met goals of durability, performance, thromboresistance, and low cost. Methods. In vitro testi ng involved extensive hydraulic characterizations using Penn State moc k loops. Calorimetry was used to determine efficiency. Durability stud ies used heated (37 degrees C) seawater for 28 to 45 days. In vivo stu dies used 46 sheep to test performance and engineering changes and to determine myocardial oxygen consumption, thromboresistance, and long-t erm durability. A left atrium-to-aorta circuit was used in all. Result s. Hydraulic testing showed no preload sensitivity but moderate afterl oad sensitivity at all impeller speeds (2,000 to 6,000 rpm). The heat load was low, and overall efficiency was 13% to 15%. Bench durability studies showed no electrical malfunction of the stator or console with out degradation of the biomaterials used. Acute in vitro studies showe d a near-linear relationship of myocardial oxygen consumption and left ventricular stroke work, pump now, and pump speed. At speeds of 2 to 3 L/min (50% bypass), left ventricular stroke work and myocardial oxyg en consumption were decreased approximately 50%. Additionally, 5 anima ls have had implants for 28 to 154 days with no macroemboli or microem boli detected in any animal. Hematologic and biochemical studies becam e normal 3 to 7 days after implantation. Hemolysis was low at less tha n 10 mg/dL. Clinical costs of the device are estimated to be 80% less than those of currently available devices. Conclusions. We conclude th at an old technology has been made into new technology by application of sound engineering design principles, microchips, and new biomateria ls. Qualifying trials for a Food and Drug Agency investigational devic e exemption application are in progress.