PRECLINICAL TRIALS OF THE VENTRASSIST ROTARY BLOOD PUMP IN SHEEP

Abstract

The VentrAssist implantable rotary blood pump (IRBP) is an electromagnetically driven centrifugal blood pump with a hydrodynamically suspended impeller which delivers flow of up to 8.5 l/min at 3000 rpm. In vivo studies in sheep were conducted to assess safety and performance for 90 days (n=8) and beyond. METHODS: A thoracotomy was used for sub-diaphragmatic pump placement, with inflow cannula connection to the left ventricular apex and outflow anastomosis to the descending aorta. There was no routine anticoagulation or antiplatelet therapy after surgery, nor prophylactic antibiotics following recovery. RESULTS: 10 sheep were supported for a total of 813 days (n=5 to 90 days; n=3 to between1–83 days; n=2 ongoing at >120 days). Mean pump flow ranged from 2.1 to 4.6 l/min for pumps run at 1900–2000 rpm and used 3.7 to 4.0 watts mean power. Early termination was related to post-surgical complications (n=1 at POD 1); inflow cannula infection (n=1 at POD 30) and electrical failure (n=1 at POD 83). Mean plasma free haemoglobin was 10.8, 14.4 and 16.3 mg/dl at POD 30, 60 and 90, respectively, in an animal model with red cells that are fragile in comparison with humans. There was no clinical evidence of device-related bleeding, haemolysis, renal or hepatic dysfunction. The pump electrical failure was due to degradation of electrical insulation following two cycles of gamma radiation. CONCLUSIONS: Following this successful PreClinical Trial, conditional approval for a 10 patient Pilot Trial of the VentrAssist IRBP has been received.