Images # 1 and 2

Findings: Images #1 and 2 are post contrast enhanced axial CT images of the chest which demonstrates an intimal flap with enhancement of both the true and false lumen extending along the descending aorta, aortic arch, ascending aorta, as well as involving the aortic root. There is associated dilatation of the aortic root, which measures over 4 cm in greatest diameter.

Diagnosis: Stanford Type A aortic dissection.

Discussion: Acute aortic dissection is the most common emergency affecting the aorta, with a reported fatality rate of 36-72% within 48 hours. Without intervention, approximately 62-91% of patients will die within the first week. Aortic dissection consists of a tear in the intima with subsequent development of an intimal flap secondary to flowing blood dissecting along the intima. There are multiple predisposing conditions including hypertension (most common), connective tissue disorder, cystic medial necrosis, and Turner's syndrome. In addition, pregnancy and aortic stenosis have been described as being related. Aortic dissections are most commonly classified using the Stanford classification system. Stanford Type A is any dissection which involves the aorta proximal to the origin of the left subclavian artery, regardless of distal extent. Stanford Type B is a dissection which is confined to the descending aorta. This classification system is important because Type A dissections generally require surgical intervention while Type B dissections can often be treated medically. There are currently three imaging modalities in use for the diagnosis of acute aortic dissection, including spiral CT, MRI, and transesophageal echocardiography (TEE). The results of a recent study indicate that the accuracy of these imaging modalities demonstrate no statistically significant difference in the diagnosis of aortic dissection. The main disadvantage of MR imaging is its long examination time and impaired monitoring of vital signs. One potential disadvantage of T.E.E. is the difficulty in visualizing the distal ascending aorta secondary to the interposition of the trachea and left main stem bronchus.

References:

1. Sommer T. Aortic Dissection: A Comparative Study of Diagnosis
   With Spiral CT, Multiplanar Transesophageal Echocardiography, and MR
   Imaging. Radiology 1996;199:347-352.

2. Fisher ER. Acute Aortic Dissection: Typical and Atypical Imaging
   Features. Radiographics 1994;14:1263-1271.