New functional concept of valvular mechanics in normal and diseased aortic valves.

The orifice area of the functioning aortic valve was measured roentgenographically and related to flow across the valve in 27 patients (12 with normal valves). The orifice area of normal valves was linearly related to stroke index and to left ventricular ejection rate. Less than half of the cross-sectional area of the valve was utilized in most patients during the resting state. A larger percentage of the anatomical crosssectional area was utilized during states of higher flow. Cinematographic studies of porcine valves in vitro showed a comparable flow-dependent orifice size. These results suggest the concept of a functional or physiologic cross-sectional area of the aortic valvular orifice. The anatomic cross-sectional area may be restricted without impingement upon the functional cross-sectional area in states in which flow across the valve is low.