Bicuspid Aortic Valve

> Everything should be kept as simple as possible, but no simpler. > > —Albert Einstein1Since its estimated first description >500 years ago by Leonardo da Vinci,2 the bicuspid aortic valve (BAV) has progressively built a reputation; initially, as a curious valvular phenotype with a tendency to develop obstruction and insufficiency. In more contemporary times, however, the BAV is recognized as underlying almost 50% of isolated severe aortic stenosis cases requiring surgery,3 and has been extensively associated with ominous outcomes such as bacterial endocarditis and aortic dissection.4 These associations, coupled with the high prevalence of BAV in humans,5 have prompted investigative efforts into the condition, which although insightful, have generated more questions than answers. This review describes our current knowledge of BAV, but, more importantly, it highlights knowledge gaps and areas where basic and clinical research is warranted. Our review has 2 sections. The first section outlines the multifaceted challenge of BAV, our current understanding of the condition, and barriers that may hamper the advancement of the science. The second section proposes a roadmap to discovery based on current imaging, molecular biology, and genetic tools, recognizing their advantages and limitations. A Condition Characterized by Variable Clinical PresentationThe clinical presentation and consequences of BAV in humans are exceedingly heterogeneous, with few clinical or molecular markers to predict associated complications.4,6 BAV can be diagnosed at any stage during a lifetime, from newborns7 to the elderly,8 and in the setting of variable clinical circumstances. Some are benign circumstances such as auscultatory abnormalities or incidental echocardiographic findings in otherwise healthy patients8; other circumstances are morbid, such as early severe aortic valve dysfunction, premature congestive heart failure, and thoracic aortic aneurysms (TAAs).8,9 Life-threatening circumstances include bacterial endocarditis and acute aortic dissection.8–11 These complications may present …