ANEURYSM OF THE ASCENDING AORTA MAY CAUSE ACUTE TYPE A AORTIC DISSECTION, and the primary aim of a prophylactic operation is avoidance of this life-threatening complication. Current guidelines recommend prophylactic replacement of the aneurysmal ascending aorta at a diameter of ≥5.5 cm. However, several reports have shown that nearly 50% of patients with an acute type A aortic dissection present with an aortic diameter <5.5 cm. It is controversial how to best respond to these observations. Because surgical advances have led to a reduction of early surgical mortality between 1% and 3%, many clinicians believe that surgery is warranted in smaller aortas. Given the frequency of a bicuspid aortic valve (BAV), such a strategy has health implications for this population.