Flow dependence of the aortic valve area in patients with aortic stenosis: Assessment by application of the continuity equation

It has been argued that the aortic valve area (AVA) in patients with aortic stenosis increases with flow. Others, however, have attributed the apparent increase to flow dependence of the empiric constant in the Gorlin formula. We examined the changes in AVA during changes in transvalvular flow induced by dipyridamole infusion in 34 patients with aortic stenosis. Two-dimensional and Doppler echocardiography was used and AVA was calculated according to the continuity equation, which does not include empiric constants. Flow increased in 29, decreased in four, and was unchanged in one patient. There was a linear correlation between percent change in flow and percent change in AVA: δ AVA% = 1.1+δ flow% · 0.56 (r = 0.72; p < 0.001 ) In conclusion, AVA was found to be flow dependent. The magnitude of change in AVA observed by noninvasive recordings agrees with previous invasive studies according to the Gorlin formula.