Aortic Dissections
Definition
Aortic dissection is believed to begin with the formation of a tear in the aortic intima that directly exposes an underlying deseased medial layer to the pulse pressure of the intaluminal blood. The blood penetrates the diseases medial layer and cleaves the laminar plane of the media in two, thus dissecting the aortic wall. Driven by the persistent intraluminal pressure, the dissection process extends a variable length along the aortic wall, typically antegrade, but sometimes retrograde.** Source: Braunwald, E. Heart Disease, A Textbook of Cardiovascular Medicine, 5th Ed. W.B. Saunders Company, Philadelphia, 1980.
Pathology
Medial degeneration, deterioration of the medial collagen and elastin is thought to be the chief predisposing factor in most nontraumatic cases of aortic dissection. Patients with Marfan's syndrome have a high risk of developing aortic dissection.
Symptoms
The most common symptom is severe pain, typically of sudden onset. Diminution or absence of pulse may be symptomatic of aortic dissection. Anterior chest pain is indicative of dissection of the ascending aorta in 90% of all cases. Interscapular pain is indicative of a dissection of descending thoracic aorta (DeBakey type I or III). Presence of pain in the neck, throat, jaw, or face is usually associated with an ascending aorta, whereas the the presence of pain in the back, abdomen, or lower extremities is indicative of descending thoracic aorta.
Management
Patients who are suspected to have aortic dissection are considered a medical emergency. Hemodynamic monitoring, cardiac rhythm, and urine output become of vital importance. Surgery, often emergent, is generally required to correct the problem. Surgery would usually involve placing the patient on cardiopulmonary bypass, deep hyporthermia, and circulatory arrest. Dissected part of the aorta is then resected and a prosthetic graft is placed between the two ends of the aorta.
DeBakey Classification of Thoracic Aortic Dissections:
Type I:
Originates in the ascending aorta just above the aortic valve and extends into the descending aorta.
Type II:
Involves the ascending aorta only.
Type III:
Originates distal to the left subclavian artery and involves the descending aorta only.
Stanford Classification:
Type A:
All dissections involving the ascending aorta, regardless of the site of origin.
Type B:
All dissections not involving the ascending aorta.
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