The natural history of thoracic aortic aneurysm disease: an overview

Relatively little is known of the natural history of thoracic aortic aneurysms (TAA). The limited data available suggests that survival is at best equivalent to that observed for abdominal aortic aneurysm (AAA), and probably significantly worse. Patients with an AAA > 6 cm diameter have a 5-year survival of 10%, with a cumulative risk of rupture over 10 years of 43%. Rupture is also responsible for death in 25% of patients with 4-7 cm AAA. Natural history studies of TAA report a 1- and 5-year survival of 39%-52% and 13%-19%, respectively, but many studies include data on acute type A dissection. Although most mortality in patients with TAA is related to aneurysm rupture, data on the relationship between aneurysm size and rupture risk remains scarce. TAA is a highly lethal condition warranting consideration of elective, prophylactic surgical repair. However, the timing of surgery is often a difficult clinical decision, particularly in asymptomatic patients or those with comorbid conditions. Surgery for TAA carries a significant mortality and potentially permanently crippling morbidity. A recommendation of surgery represents a balance, weighing estimates of TAA natural history and rupture risk against operative mortality and complication rate, while carefully considering the impact of important comorbid conditions, e.g., ischemic heart disease, obstructive pulmonary disease, and renal dysfunction. When to intervene is a critical question facing cardiovascular surgeons and is based upon an assessment of the risk of rupture. This risk is related to the site, aetiology, size, and expansion rate of the aneurysm.