Nature Versus Nurture in Bicuspid Aortic Valve Aortopathy

> There is no disease more conducive to clinical humility than aneurysm of the aorta.1 > > — William Osler Bicuspid aortic valve (BAV) is a common congenital cardiac malformation affecting 1 to 2% of the population with a predilection for males.2 Although patients with BAV often develop aortic aneurysms requiring surgical intervention,3,4 the formation of aortic aneurysms is variable and there are currently no good predictors of aneurysm formation. Although studies have shown that patients with BAV have genetically inherited aortic disorders that predispose them to aneurysm development,5,6 there is ongoing controversy concerning the degree to which altered hemodynamics (nurture) and genetics (nature) interact. The study by Mahadevia et al7 in this issue of Circulation provides important additional support for the argument that altered flow patterns attributable to abnormal valve architecture do indeed play a role in BAV aortopathy.Article see p 673Phase contrast MRI has been used to measure changes in blood velocity and flow with standard techniques measuring these parameters in 2 dimensions, or through plane. Four-dimensional (4D) MRI allows the speed and direction of aortic flow to be visualized and measured over time in all 3 dimensions, thereby providing not only informative images but an improved tool for the study of flow disturbances. One of the more active areas of research using 4D MRI has been in BAV aortopathy with the hope that understanding flow disturbances will give new insight into BAV-associated aneurysm formation.Prior studies8–10 using 4D MRI have demonstrated altered ascending aortic wall sheer stress (WSS) in patients with BAV and have suggested a mechanistic link between the alteration in aortic outflow caused by the fusion of BAV cusps and the development of ascending aortic aneurysms.8–13 However, these studies have focused …