Preclinical testing of the Levitronix Ultramag pediatric cardiac assist device in a lamb model

We evaluated the effects of the Levitronix UltraMag pediatric ventricular assist system on healthy animals during 29- to 90-day periods by assessing hemocompatibility and hepatic and renal functions while operating the device in a flow range suitable for pediatric patients. Nine lambs (weight, 15 to 24 kg) received the Levitronix UltraMag with an outflow cannula anastomosed to the descending aorta and an inflow cannula inserted into the left ventricular apex. Pump function data were collected at 1-hour intervals, and postoperative hematology and clinical chemistry tests were performed weekly throughout the study. Complete necropsy and histopathologic examinations were performed at study termination. Pump and circuit were thoroughly inspected for evidence of thrombi. All animals reached the scheduled endpoint of 29 to 90 days without device-related problems. Mean flow was maintained at 1.14 +/- 0.19 L/min. Hematologic values were within normal range in all animals except in one lamb that had a severe hemolytic reaction after cefazolin sodium administration. In all animals, serum glutamic-oxaloacetic transaminase and creatinine kinase levels increased after surgery but gradually returned to normal limits within 1 week. Postmortem examination of the explanted organs revealed small infarcted areas in five lamb kidneys, but renal function was unaffected. All other major organs were unremarkable. In one explanted pump (a 30-day study), a small thrombus was seen within the impeller blade. The other eight pumps were free of thrombus. The Levitronix UltraMag successfully operated in pediatric flow ranges without device-related adverse events.