Hemodynamic characteristics of a mixed flow pump prototype: progress report of in vitro and acute animal experiments

A new dual-inlet mixed-flow blood pump was designed and tested in our laboratory. The objective of the present study was to analyze hemodynamic characteristics of the pump prototype in vitro and during acute in vivo experiments. The mixed-flow pump was first tested in vitro and then implanted in 11 pigs and 3 calves. The left ventricular apex was cannulated with the pump and an outflow graft was anastomosed to the descending thoracic aorta. Flow and pressure probes were also implanted. Animals were killed 3 to 12 hours after surgery. In 11 pigs, pump outflow averaged 3.8 +/- 0.4, 4.5 +/- 0.4, 5.2 +/- 0.8, 5.9 +/- 0.3, and 6.5 l/min at 8,000, 9,000, 10,000, 11,000, and 12,000 pump speed in rpm. Differential pressure at the pump averaged 45 +/- 6, 54 +/- 8, 68 +/- 16, 70 +/- 12, and 85 +/- 7 mm Hg at 8,000, 9,000, 10,000, 11,000 and 12,000 rpm. Mean aortic pressure averaged 64 +/- 15 mm Hg throughout the procedures. In 3 calves, mean aortic pressure and left ventricular pressure remained stable during 4, 6, and 9 hours of support at 9,500, 10,000, 10,500, 11,000, and 11,500 rpm. The hemodynamic performance of our mixed-flow pump appears satisfactory during short-term support in animals. It supports similarly to axial-flow blood pumps in clinical trials. Based on these findings, an ameliorated design of this mixed-flow pump running at smaller rotational speed against a similar pressure head is under way.