FLOW DEPENDENCE OF VALVE AREA IN AORTIC-STENOSIS - RELATION TO VALVE MORPHOLOGY

Objectives. We sought to develop an index of flow dependence of valve area in aortic valve (AoV) stenosis and to determine whether this inde x is related to structural characteristics of the diseased valve, Back ground. Many studies of AoV stenosis using Gorlin or continuity equati on methods have demonstrated flow dependence (an increase in valve are a with increased flow), Variation in flow dependence between patients despite similar flow rates remains unexplained, Methods. Dobutamine Do ppler echocardiography was used to calculate flow rate and valve area by the continuity equation in 27 patients with aortic stenosis, For ea ch patient the slope of the regression line of valve area to flow rate was determined (slope of flow dependence), Transesophageal echocardio graphy was used to evaluate features of valve morphology potentially r elated to the etiology of AoV stenosis and the mechanism of flow depen dence. Results. Mean slope of flow dependence mas 0.28 cm(2)/100 ml pe r s (range -0.06 to 0.53); flow dependence was significantly >0 in 21 patients and was lower for bicuspid valves (slope 0.21 cm(2)/100 ml pe r s) than for tricuspid valves with <10% commissural fusion (slope 0.3 5, p < 0.01), Off-center/ovoid orifices demonstrated the least flow de pendence (slope 0.19), whereas star-shaped orifices showed the most (s lope 0.36, p < 0.01). Greater flow dependence was related to a lower p ercentage of commissural fusion (r = -0.46, p = 0.02) as well as diffu se sclerosis, primarily involving the cusp bodies, rather than localiz ed sclerosis, with involvement of cusp margins, Conclusions. The slope of Row dependence of valve area in AoV stenosis differs markedly betw een patients, More flow dependence was associated with tricuspid valve s and the morphologic features characteristic of calcific AoV stenosis , whereas less how dependence was associated with bicuspid valves and the features of rheumatic disease. (C) 1998 by the American College of Cardiology.