42. The correct answer is A. This patient has an aortic dissection (formerly called dissecting aneurysm), a potentially fatal condition that is too often confused clinically with myocardial infarction. The most important clinical clue is that the pain shifts with time. Noninvasive techniques, such as transesophageal echocardiography, CT, and MRI, are increasingly useful in making this diagnosis.
Aortic valve stenosis (choice B) would not be expected to produce severe chest pain of acute onset.
This patient's clinical history does not suggest either an atherosclerotic (choice C) or a syphilitic (choice E) aneurysm. Even if he had one of either of these types of aneurysms and it had begun to rupture, the distinctive feature of severe pain moving downward would probably not be present.
Myocardial infarction (choice D) is the major diagnosis most often confused with this patient's condition. The movement of the pain is the major clinical tip-off suggesting that this is not the correct answer.