Should We Operate on Aortic Aneurysms under 5 . 5 cm?

Abstract

As the North American population ages and screening programs for aortic dilatation are implemented, more individuals will be detected who have asymptomatic small aortic aneurysms. Declining elective operative mortality rates, compared with the fixed 50% operative mortality rate for ruptured aneurysms, have led surgeons to reconsider repair of small aneurysms. The rupture rate of small aortic aneurysms ( < 5 cm) has ranged from 0 to 7% over 5 years in recent studies. Risk factors for expansion of small aortic aneurysms include smoking, chronic obstructive pulmonary disease, systolic hypertension, and increased pulse pressure. Average growth rate of aneurysms less than 6 cm is approximately 0.4 cm/year, although pronounced increases in aneurysm size may occur unexpectedly in asymptomatic patients. There are three prospective randomized clinical trials designed by surgeons in North America and the United Kingdom to evaluate the management of 4- to 5.5-cm diameter abdominal aortic aneurysms. In general, rupture rates have been confirmed to be low, but inevitable enlargement of the aneurysm continues, leading to operation in as many as 50% of patients under surveillance by 3 years. Endovascular grafts now in clinical trial are not suitable for all aneurysms, but appear more adaptable to small aneurysms. We predict considerable interest in deployment of endografts for small abdominal aortic aneurysms (AAAs) after long-term studies have demonstrated safety We currently recommend operation for 4- to 5-cm diameter AAAs in properly selected patients with acceptable risk status under age 70, providing that the surgeon and hospital have demonstrated low morbidity and mortality rates. If endovascular repair proves to be durable and to have less mortality and morbidity than open repair, the threshold for intervention may be lowered further.