A 65-year-old man who has a long history of hypeension presents to the emergency depament with tearing chest pain that radiates to the back. An electrocardiogram is normal, as are cardiac enzymes. A "stat" chest radiograph demonstrates widening of the mediastinum. Which of the following is the most likely?

The clinical presentation of a dissecting aoic aneurysm mimics that of a myocardial infarction; however, electrocardiographic changes and increased concentration of cardiac enzymes are notably absent. The mediastinum is often widened by radiographic examination. Although there is an association with hypeension and disorders of connective tissue (e.g., Marfan syndrome and Ehlers-Danlos syndrome), there is no association with atherosclerosis. The presentation exemplified by this scenario is a true surgical emergency!