Abdominal Aortic Aneurysms
A. Darrell Tackett, MD, FACS

Abdominal aortic aneurysms (AAA) affect 1-5% of the general population and increase in incidence with age. Over the past 30 years with the increased elderly population at risk, the prevalence has increased 300%. Rupture, the most deadly complication of AAA, is responsible for an estimated 15,000 deaths annually.

Operative mortality for elective aneurysm repair has decreased from an average of 10-15% in the early 1950’s to an average of 3.5% in recent reviews. This number compares favorable to an estimated 75-90% mortality for ruptured AAA. There remains some controversy relative to the indications for repair of small AAA’s (less than 5 cm in diameter) and the point at which older patients with multiple comorbid diseases should be subjected to the rigors of aneurysm repair. The estimated annual risks of rupture of AAA’s less than 5 cm in diameter is 3.3%. The risk of rupture in AAA’s larger than 5 cm is 9 to 12% and in AAA’s larger than 7 cm in diameter is greater than 25% for each year of follow-up. Comparison of operative mortality statistics for elective aneurysm repair and the relative risks of rupture based on aneurysm diameter would seem to mandate consideration of elective repair in all patients with aneurysms 5 cm or greater in diameter. At institutions with extensive experience in aortic surgery, good risk patients with AAA’s of 4 cm or greater in diameter are considered candidates for repair.

In addition to aneurysm size, multiple host factors must be considered in the decision to recommend elective aneurysm repair. Chronologic age becomes a significant factor only in the 9th decade. However, multiple cardiac, pulmonary and renal problems can dramatically change the predicted operative mortality. Figure 2 illustrates the contribution of various comorbid disease to the estimated operative mortality for elective repair of AAA.

In summary, non-operative management of AAA exposes many patients to excessive rates of rupture and mortality. Advances in surgical, anesthetic, and critical care management have enabled more patients to undergo successful operative repair. Decisions regarding appropriate surgical management should be based on the inherent risk of rupture, technical aspects of AAA anatomy and multiple patient factors. Each factor must be considered on an individual basis by a physician experience in aortic surgery.

References: Bodily. Am J Surg 1983:146:280-82 Weatherford. Ann Vas Surg 1997;11:54-61 Nehler. Sem Vasc Surg 1995:8:108-14 Hollier. J Vasc Surg 1992;15;1046-56