INFLUENCE OF STENOTIC VALVE GEOMETRY ON MEASURED PRESSURE-GRADIENTS AND VENTRICULAR WORK - THE RELATIONSHIP BETWEEN MORPHOLOGY AND FLOW

The physiologic impact of aortic valve stenosis is most directly refle cted by an increased workload placed on the ventricle. In the pediatri c population the morphology of aortic stenosis varies considerably. Fl uid dynamic principles suggest that different morphologies may require the ventricle to accelerate blood to different maximal velocities for constant cardiac outputs and valve areas, resulting in different vent ricular workloads. This study examined this important concept in in vi tro models designed to isolate the effect of valve geometry on distal velocity, pressure gradients, and proximal work. Four stenotic valve m orphologies were examined using a variable-voltage pump system. For co nstant orifice areas and flows, markedly different workloads were requ ired by the pump, and this difference was reflected in direct measurem ents of pressure gradient and Doppler predictions of gradient. These f undamental fluid dynamic studies isolate the relationship between flow , work, and stenotic valve morphology. Different orifice geometries af fect the value of the coefficient of contraction, which is reflected i n different maximum velocity values for stenosis with constant anatomi c areas and flows. The proximal pumping chamber must generate differen t levels of force to achieve these different velocities, and this vari ability is reflected in the clinically measured pressure gradient.