Letter by Poullis and Warwick Regarding Article, “Paradoxical Low-Flow, Low-Gradient Severe Aortic Stenosis Despite Preserved Ejection Fraction Is Associated With Higher Afterload and Reduced Survival” To the Editor:

In their article, Hachicha et al1 raise a number of key points that merit further questioning. Despite the direct relevance of their findings to everyday clinical practice, it is our opinion that their use of the terms paradoxical low-flow and higher afterload may be flawed. The gradient across a stenotic valve can be estimated using the Bernoulli equation (4V2). The velocity across a stenosis equals flow divided by area of stenosis, ie, cardiac output divided by aortic valve area in aortic stenosis. Thus, the gradient for a given stenosis depends entirely upon the cardiac output. The term preserved ejection fraction indicates that the ejection fraction’s value is maintained above 50%. As demonstrated by the authors ’ data,1 however, the group with a normal flow and signifi-cantly higher gradient had significantly higher ejection fractions, cardiac outputs, and cardiac indices, so their hemodynamic finding