|Print Date:||May 25, 2013, 10:07 pm|
|Text||An aortic dissection is a longitudinal split in the media of the aortic wall resulting in an intimal tear that divides the aorta into true and false lumen. In approximately 13% of cases dissection is confined within the wall and no intimal tear is identified. A dissection moves distally, proximally, or in both directions as blood under high pressure enters the false chanel. The average patients are greater than 50 years old and may present with stroke, chest or back pain, renal failure, hypertension, mesenteric ischemia, lower extremity ischemia, or paraplegia.
Risk factors for aortic dissection inclued chronic hypertension, connective tissue disorders (e.g. Marfan syndrome, Ehlers Danlos syndrome), congenital aortic anomalies (e.g. bicuspisd aortic valve, coarctation, and turners syndrome), arteritis (e.g. Takasayu's arteritis, Giant cell arteritis), pregnancy and trauma.
There are two classification schemes:
A - Involves ascending aorta and usually begins with tear
just above the aortic valve
B - Involves the descending aorta and usually begins just
just distal to the origin of the left subclavian
I - Involves ascending and descending aorta
II - Confined to asceding aorta
III - Confined to descending aorta
Type A lesions most commonly undergo surgical therapy, with replacement of aortic valve when necessary. Medical treatment is the principal treatment modality for type B lesions.
CT accurately detects and stages dissection, however is limited in that it suboptimally evaluates the coronary arteries as well as aortic regurgitation. It also accurately detects thrombosed false channels, periaortic hematoma, and pericardial/pleural blood. Scans show intimal flap with two lumens. The true lumen often demonstrates more vivid enhancement than the false lumen. Noncontrast scans are used to detect wall hematomas which shows up as bright signal density. The primary role of CT is in triage of patients with equivocal findings and surveillance of chronic dissections. Other modalities used in the evaluation of dissections include chest radiographs, MRI, Transesophageal echocardiography, and angiography.
Helpful important radiologic information needed by the surgeon includes entry and reentry site of dissection, extent of dissection, involvement of aortic branches (e.g coronaries, great vessels off the arch, renal arteries etc.), existence of aortic insufficiency and evidence of rupture.
|References:||Valji, Karim. Vascular and Interventional Radiology.
W.B. Saunders Company: Philadelphia, 1999.
Weissleder, Ralph et al. Primer of Diagnostic Imaging,
2nd ed. Mosby: Philadelphia, 1997.
|Contributor||Hayden O Jack (National Capital Consortium)|
|Peer Reviewer||David S. Feigin, M.D. (Johns Hopkins Hospitals)|
|Record Number||: 2575|
|Location:||Cardiovascular (inc. Heart)|
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