The most likely answer in this case is D, but the correct answer is B. Because of diagnostic uncertainty, this man underwent urgent cardiac catheterization. Angiography revealed 80% occlusion of the left main coronary artery resulting from the false lumen created by an ascending aortic dissection. An immediate transesophageal echocardiogram showed mild aortic insufficiency, a left ventricular ejection fraction of 40%, and diffuse anterior hypokinesis. The patient underwent emergency surgery to repair both aortic dissection and the aortic valve, and to perform bypass grafting to the left main coronary artery.