Natural history of thoracic aortic aneurysms: indications for surgery, and surgical versus nonsurgical risks.

BACKGROUND The natural history of thoracic aortic aneurysm is incompletely understood. Over the last 10 years, at Yale University we have maintained a large computerized database of patients with thoracic aortic aneurysms and dissections. Analysis of this database has permitted insight into fundamental issues of natural behavior of the aorta and development of criteria for surgical intervention. METHODS Specialized statistical methods were applied to the prospectively accumulated database of 1600 patients with thoracic aneurysm and dissection, which includes 3000 serial imaging studies and 3000 patient years of follow-up. RESULTS Growth rate: the aneurysmal thoracic aorta grows at an average rate of 0.10 cm per year (0.07 for ascending and 0.19 for descending). Critical sizes: hinge points for natural complications of aortic aneurysm (rupture or dissection) were found at 6.0 cm for the ascending aorta and 7.0 cm for the descending. By the time a patient achieved these critical dimensions the likelihood of rupture or dissection was 31% for the ascending and 43% for the descending aorta. Yearly event rates: a patient with an aorta that has reached 6 cm maximal diameter faces the following yearly rates of devastating adverse events: rupture (3.6%), dissection (3.7%), death (10.8%), rupture, dissection, or death (14.1%). Surgical risks: risk of death from aortic surgery for thoracic aortic aneurysm was 2.5% for the ascending and arch and 8% for the descending and thoracoabdominal aorta. Genetic analysis: family pedigrees confirm that 21% of probands with thoracic aortic aneurysm have first-order family members with arterial aneurysm. CONCLUSIONS In risk/benefit analysis the accumulated data strongly support a policy of preemptive surgical extirpation of the asymptomatic aneurysmal thoracic aorta to prevent rupture and dissection. We recommend intervention for the ascending aorta at 5.5 cm and for the descending aorta at 6.5 cm. For Marfan's disease or familial thoracic aortic aneurysm, we recommend earlier intervention at 5.0 cm for the ascending and 6.0 cm for the descending aorta. Symptomatic aneurysms must be resected regardless of size. Family members should be evaluated.