E. Intravenous labetalol (Normodyne, Trandate). Patients with thoracic aneurysms often present without symptoms. With dissecting aneurysms, however, the presenting symptom depends on the location of the aneurysm. Aneurysms can compress or distort nearby structures, resulting in branch vessel compression or embolization of peripheral arteries from a thrombus within the aneurysm. Leakage of the aneurysm will cause pain, and rupture can occur with catastrophic results, including severe pain, hypotension, shock, and death. Aneurysms in the ascending aorta may present with acute heart failure brought about by aortic regurgitation from aortic root dilatation and distortion of the annulus. Other presenting findings may include hoarseness, myocardial ischemia, paralysis of a hemidiaphragm, wheezing, coughing, hemoptysis, dyspnea, dysphagia, or superior vena cava syndrome. This diagnosis should be suspected in individuals in their sixties and seventies with the same risk factors as those for coronary artery disease, particularly smokers. A chest radiograph may show widening of the mediastinum, enlargement of the aortic knob, or tracheal displacement. Transesophageal echocardiography can be very useful when dissection is suspected. CT with intravenous contrast is very accurate for showing the size, extent of disease, pressure of leakage, and nearby pathology. Angiography is the preferred method for evaluation and is best for evaluation of branch vessel pathology. MR angiography provides noninvasive multiplanar image reconstruction, but does have limited availability and lower resolution than traditional contrast angiography. Acute dissection of the ascending aorta is a surgical emergency, but dissections confined to the descending aorta are managed medically unless the patient demonstrates progression or continued hemorrhage into the retroperitoneal space or pleura. Initial management should reduce the systolic blood pressure to 100-120 mm Hg or to the lowest level tolerated. The use of a β-blocker such as propranolol or labetalol to get the heart rate below 60 beats/min should be first-line therapy. If the systolic blood pressure remains over 100 mm Hg, intravenous nitroprusside should be added. Without prior beta-blocade, vasodilation from the nitroprusside will induce reflex activation of the sympathetic nervous system, causing increased ventricular contraction and increased shear stress on the aorta. For descending dissections, surgery is indicated only for complications such as occlusion of a major aortic branch, continued extension or expansion of the dissection, or rupture (which may be manifested by persistent or recurrent pain).