Current Concepts for the Pathogenesis of Abdominal Aortic Aneurysms

Abstract

Abdominal aortic aneurysms (AAAs) occur in approximately 2% of the elderly population. In 1988, 39,000 AAA repairs were performed in the United States for a total health cost of approximately $933 million ($23,931 per patient). 2,3AAAs are always associated with significant aortic atherosclerosis and because of this association have been classically described as random variants of atherosclerosis that occur at a weakened site in the arterial wall. The aneurysm is , thought to grow according to Laplace's law until eventually it ruptures. This description of AAAs is now being challenged by an increasing amount of data from recent clinical, genetic, and biochemical studies that suggest that aneurysmal pathogenesis is more likely related to an alteration in systemic connective tissue metabolism. CLINICAL OBSERVATIONSIf aneurysmal degeneration is considered to be a common manifestation of atherosclerosis, then distal aneurysms and aortic aneurysms should be commonplace in the patient with diffuse arterial disease. This, however, is not the case. It is unusual, if not rare, for a patient with superficial femoral artery disease, distal arterial disease, or aortoiliac obstructive disease to have distal arterial aneurysms. However, AAAs commonly occur along with peripheral aneurysms, and patients with peripheral aneurysms frequently have associated aneurysms at other locations. In a study of 1488 patients with AAAs, 4% of the patients had associated peripheral aneurysms, and multiple aneurysms occurred in 83% of patients who had at least one peripheral aneurysm.4 In patients with a common femoral artery aneurysm, 95% had a second aneurysm, 92% had an aortoiliac aneurysm, and 59% had bilateral femoral aneurysms. Among patients with popliteal artery aneurysms, 78% had a second aneurysm, 64% had an aortic aneurysm, and 47% had a popliteal artery aneurysm on the contralateral . side.' In one study of 100 consecutive femoral aneurysms,' all patients were men and 85% of these patients had an AAA.Inguinal herniation is significantly higher in patients with AAAs (26%) as compared to patients with aortic occlusive disease ( 15 % ) .6 In addition, patients with AAAs have more severe herniation in terms of direct hernias, bilateral hernias, recurrent hernias, and early onset, suggesting that a systemic connective tissue disorder causes weakening of both the abdominal wall and the aorta and results in formation of both hernia and AAA in the same patient.6 Tortuous carotid arteries are associated with AAAs in up to 44% of cases, whereas only at UNIV REGINA LIBRARY on June 4, 2016 pvs.sagepub.com Downloaded from