AORTIC DISSECTION

Potentially life-threatening condition in which disruption or aortic intima allows dissection of blood into vessel wall; may involve ascending aorta (type II), descending aorta (type III), or both (type I). Alternative classification: Type A—dissection involves ascending aorta; type B—limited to transverse and/or descending aorta. Involvement of the ascending aorta is most lethal form. Variant acute aortic syndromes include intramural hematoma without an intimal flap, and penetrating atherosclerotic ulcer.



Etiology 

Ascending aortic dissection is associated with hypertension, cystic medial necrosis, Marfan and Ehlers-Danlos syndromes; descending dissections are commonly associated with atherosclerosis or hypertension. Incidence is increased in pts with coarctation of aorta, bicuspid aortic valve, and rarely in third trimester of pregnancy in otherwise normal women.

Symptoms 

Sudden onset of severe anterior or posterior chest pain, with “ripping” quality; maximal pain may travel if dissection propagates. Additional symptoms relate to obstruction of aortic branches (stroke, MI), dyspnea (acute aortic regurgitation), or symptoms of low cardiac output due to cardiac tamponade (dissection into pericardial sac).

Physical Examination 

Sinus tachycardia common; if cardiac tamponade develops, hypotension, pulsus paradoxus, and pericardial rub appear. Asymmetry of carotid or brachial pulses, aortic regurgitation, and neurologic abnormalities associated with interruption of carotid artery flow are possible findings.

Laboratory 

CXR: Widening of mediastinum; dissection can be confirmed by CT, MRI, or transesophageal echocardiography. Aortography is rarely required, as sensitivity of these noninvasive techniques is >90%.

Aortic Dissection TREATMENT

Reduce cardiac contractility and treat hypertension to maintain systolic bp between 100 and 120 mmHg using IV agents , e.g., sodium nitroprusside accompanied by a beta blocker (e.g., IV metoprolol, labetolol, or esmolol, aiming for heart rate of 60 beats per min), followed by oral therapy. If beta blocker contraindicated, consider IV verapamil or diltiazem . Avoid direct vasodilators (e.g., hydralazine) because they may increase shear stress. Ascending aortic dissection (type A) requires surgical repair emergently or, if pt can be stabilized with medications, semielectively. Descending aortic dissections are stabilized medically (maintain systolic bp between 110 and 120 mmHg) with oral antihypertensive agents (esp. beta blockers); surgical repair is not usually indicated unless continued pain or extension of dissection is observed (by serial MRI or CT performed every 6–12 months).