Radiology Rounds

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Albany Medical Review - January 2002

A 74-year-old man with persistence of chest pain

Arthur Galoustian, MD

Answer: Presence of a double lumen with an intimal flap in the ascending aorta, confirmed the diagnosis of aortic dissection.

Diagnosis of aortic dissection by contrast computed tomography (CT) requires identification of two distinct lumens with a visible intimal flap. Various investigators place the sensitivity of contrast CT in diagnosing aortic dissection at 83-100 percent, and specificity of 90-100 percent. Disadvantages of contrast CT include limited sensitivity to identify: entry site of intimal flap, presence of aortic insufficiency, and detection of branch vessel or coronary artery involvement.

Diagnosis of "probable"aortic dissection by transesophageal echocardiography (TEE) requires identification of an undulating intimal flap which is not parallel to the motion of any other cardiac structure, in at least two views. Diagnosis of "definite" aortic dissection, additionally requires identification of site of entry, or doppler-flow phenomena in the false lumen or thrombus. Prospective blinded studies show sensitivity of 100 percent, but specificity of 68-77 percent. False positive tests are often a consequence of reverberating sclerotic aortic root or vessels. Use of TEE has the added advantage of showing involvement of the ostia of proximal coronary arteries. Disadvantages of use of TEE include limited sensitivity to identify thrombus formation or branch vessel involvement.

The criteria to diagnose an aortic dissection by magnetic resonance imaging (MRI) are same as those with contrast-enhanced CT. Most studies from the 1980Õs using lower field strength scanners, showed sensitivities of 96-100 percent and specificity of 100 percent. Modern more powerful scanners have sensitivities approaching 100 percent. Use of MRI imaging has the added advantage of not requiring IV contrast material. Disadvantages of use of MRI include: logistics of long scanning time for potentially unstable patients, can not safely be performed with pacemakers or certain types of metallic heart valves, and limited sensitivity to identify aortic insufficiency or coronary artery involvement.

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References

1. Goldman AP, Kotler MN, Scanlon MH, Ostrum BJ, Parameswaran R, Parry WR. The complementary role of magnetic resonance imaging, Doppler echocardiography, and computed tomography in the diagnosis of dissecting thoracic aneurysms. Am Heart J 1986;111:970-981.

2. Erbel R, Engberding R, Daniel W, et al. Echocardiography in diagnosis of aortic dissection. Lancet 1989;1:457-461.

3. Cigarroa JE, Isselbacher EM, DeSanctis RW, Eagle KA. Medical Progress: Diagnostic Imaging in the Evaluation of Suspected Aortic Dissection-- Old Standards and New Directions. New England J of Med 1993; 328:35-43.

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30.01.2002