THE IMPORTANCE OF PULSATILE AND NONPULSATILE FLOW IN THE DESIGN OF BLOOD PUMPS

The traditional approach of total artificial heart (TAH) and ventricul ar assist device (VAD) development has been the mimicking of the nativ e heart. Nonpulsatile flow using cardiopulmonary bypass has provided e vidence of short-term physiologic tolerances. The design of nonpulsati le TAHs and VADs has eliminated the need for valves, flexing diaphragm s, and large ventricular volumes. However, these devices require high efficiency power sources and reliable bearing seals or electromagnetic bearings while simultaneously attempting to avoid thromboemboli. The physiologic response to nonpulsatile flow is complex and variable. Whe n compared to a pulsatile device, a nonpulsatile TAH or VAD needs to p roduce increased flow and higher mean intravascular pressures to maint ain normal organ function. Despite its maintaining normal organ functi on, nonpulsatile flow does cause alterations in biochemical functions and organ specific blood now. The combination of bioengineering superi ority and the maintenance of physiologic homeostasis has directed futu re TAH and VAD research towards nonpulsatile systems.