RESUMO
PURPOSE--To describe the design of a ventricular assist device (VAD), its manufacturing and testing. METHODS--The VAD is pulsatile, with a free floating membrane, smooth internal surfaces, and pericardium valves. It comprises also a pneumatic driving unit capable of operating in the ®full to empty®, EKG synchronized or asynchronous modes. The system was tested ®in vitro® to assess its mechanical durability, hydrodynamic performance and hemolysis. ®In vivo® tests were performed in 22 sheep and 8 calves aiming at optimizing cannulas and implant techniques. In these experiments, hemolysis and the device's capacity of restoring to normal hemodynamic parameters during induced cardiac failure were evaluated. RESULTS--The device was worked 4,000 hours without failure in a mock circulatory loop. Hydrodynamic performance was satisfactory for adult circulatory support. In ®full to empty® mode it displayed a frequency mediated ®Starling like® performance. Optimum output was achieved with a systole duration of 40//of the cycle. ®In vitro® hemolysis index was 6.7 +/- 2.1. Hemolysis in animal experiments was clinically non significant. In calves under induced cardiac failure the VAD was able to normalize hemodynamic parameters within 120 minutes. CONCLUSION--This VAD is capable to circulatory assist for cardiogenic shock in conditions needed for an adult patient and the average time span anticipated for bridge to transplantation or post cardiotomy cardiogenic shock