Ascending aortic dilatation associated with bicuspid aortic valve: pathophysiology, molecular biology, and clinical implications.

Ascending aortic dilatation occurs more frequently and at a younger age in patients with bicuspid aortic valves (BAV) than it does in patients with normal trileaflet aortic valves (TAV). The clinical significance of the correlation between BAV and dilatation of the ascending aorta is based on 2 factors. First, BAV is the most common congenital cardiac abnormality, occurring in 0.46% to 1.37% of the population.1–4 Second, aortic dilatation has a propensity for dissection and rupture, making it a potentially lethal disease. Ascending aortic dilatation with BAV warrants frequent monitoring, with possible early prophylactic surgical intervention to prevent dissection or rupture. The purpose of this article is to review the etiology and natural history and to make suggestions regarding management of the disease on the basis of the limited data available. ### Differential for Etiology of Ascending Aortic Aneurysms Most ascending aortic aneurysms have unknown etiology and are classified as idiopathic.5 In contrast to aneurysms of the descending aorta, ascending aortic aneurysms are not commonly a result of atherosclerosis.6,7 Among heritable connective tissue disorders such as Marfan syndrome and Ehlers-Danlos syndrome, ascending aortic aneurysms are a clinical component of the syndrome. BAV disease, also a heritable disorder, is known to have an increased risk of ascending aortic aneurysm as well. Marfan syndrome and BAV aortic disease share common histopathological findings, including medial degeneration, increased matrix metalloproteinase (MMP) activity, and decreased fibrillin-1 in the aortic wall.8 ### Anatomic Boundaries of BAV Disease Development of a BAV is part of a larger spectrum of structural developmental abnormalities involving the great vessels. The aortic valve and ascending aorta share a common embryonic origin: they both develop from neural crest cells.9–12 The vascular smooth muscle cells (VSMCs) that undergo apoptosis in the media of the ascending aorta are of neural crest origin.13 The pulmonary trunk demonstrates histopathological changes similar to those of the …

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