125 DISEASES OF THE AORTA
Harrison’s Manual of Medicine
DISEASES OF THE AORTA
Other Abnormalities of the Aorta
Abnormal widening of the abdominal or thoracic aorta; in ascending aorta most commonly secondary to cystic medial necrosis or atherosclerosis; aneurysms of descending thoracic and abdominal aorta are primarily atherosclerotic.
HISTORY May be clinically silent, but thoracic aortic aneurysms often result in deep, diffuse chest pain, dysphagia, hoarseness, hemoptysis, dry cough; abdominal aneurysms result in abdominal pain or thromboemboli to the lower extremities.
PHYSICAL EXAMINATION Abdominal aneurysms are often palpable, most commonly in periumbilical area. Pts with ascending thoracic aneurysms may show features of the Marfan syndrome (HPIM-15, Chap. 351).
LABORATORY CXR: Enlarged aortic silhouette (thoracic aneurysm); confirm abdominal aneurysm by abdominal plain film (rim of calcification), ultrasound, CT scan, or MRI. Contrast aortography is often performed preoperatively. If clinically suspected, obtain serologic test for syphilis, especially if ascending thoracic aneurysm shows thin shell of calcification.
Control of hypertension (Chap. 124) is essential. Surgical resection of thoracic aortic aneurysms >6 cm in diameter (abdominal aortic aneurysms >5 cm), for persistent pain despite bp control, or for evidence of rapid expansion. In pts with the Marfan syndrome, thoracic aortic aneurysms >5 cm usually warrant repair.
AORTIC DISSECTION (Fig. 125-1)
FIGURE 125-1. Classification of aortic dissections. Stanford classification: Top panels illustrate type A dissections that involve the ascending aorta independent of site of tear and distal extension; type B dissections (bottom panels) involve transverse and/or descending aorta without involvement of the ascending aorta. DeBakey classification: Type I dissection involves ascending to descending aorta (top left); type II dissection is limited to ascending or transverse aorta, without descending aorta (top center + top right); type III dissection involves descending aorta only (bottom left). [From DC Miller, in RM Doroghazi, EE Slater (eds.) Aortic Dissection. New York, McGraw-Hill, 1983, with permission.]
Potentially life-threatening condition in which disruption of 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 descending aorta. Involvement of the ascending aorta is most lethal form.
ETIOLOGY Ascending aortic dissection associated with hypertension, cystic medial necrosis, the Marfan syndrome; descending dissections 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 common findings.
LABORATORY CXR: Widening of mediastinum; dissection can be confirmed by CT scan, MRI, or ultrasound (esp. transesophageal echocardiography). Aortography recommended if results of these imaging techniques are not definitive.
Reduce cardiac contractility and treat hypertension to maintain systolic bp between 100 and 120 mmHg using IV agents (Table 125-1), e.g., sodium nitroprusside accompanied by a beta blocker (aiming for heart rate of 60 beats per min), followed by oral therapy. If beta blocker contraindicated, consider IV verapamil or diltiazem (Table 115-3). Direct vasodilators (hydralazine, diazoxide) are contraindicated 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); immediate surgical repair is not necessary unless continued pain or extension of dissection is observed (serial MRI or CT scans).
Table 125-1 Treatment of Aortic Dissection
OTHER ABNORMALITIES OF THE AORTA
ATHEROSCLEROSIS OF ABDOMINAL AORTA Particularly common in presence of diabetes mellitus or cigarette smoking. Symptoms include intermittent claudication of the buttocks and thighs and impotence (Leriche syndrome); femoral and other distal pulses are absent. Diagnosis is established by noninvasive leg pressure measurements and Doppler velocity analysis, and confirmed by aortography. Aortic-femoral bypass surgery is required for symptomatic treatment.
TAKAYASU’S (“PULSELESS”) DISEASE Arteritis of aorta and major branches in young women. Anorexia, weight loss, fever, and night sweats occur. Localized symptoms relate to occlusion of aortic branches (cerebral ischemia, claudication, and loss of pulses in arms). ESR is increased; diagnosis confirmed by aortography. Glucocorticoid and immunosuppressive therapy may be beneficial, but mortality is high.
For a more detailed discussion, see Dzau VJ, Creager MA: Diseases of the Aorta, Chap. 247, p. 1430, in HPIM-15.