NATURAL-HISTORY OF DESCENDING AND THORACOABDOMINAL AORTIC-ANEURYSMS

Data on the natural history of descending and thoracoabdominal aneurys ms are limited to a few studies. They demonstrated that, independent f rom the different mechanisms of injury and degeneration affecting the structural integrity of the aortic wall, the biologic fate of all aneu rysms is progressive enlargement and rupture. Laminated thrombus and c alcification do not prevent this process. The natural history is marke dly influenced by size, location, symptoms, and etiology of thoracic a neurysms. They may develop symptoms related to mechanical compression of adjacent structures, but more frequently they are asymptomatic unti l rupture occurs. Usually, aortic rupture causes death by exsanguinati on and shock before bleeding can be controlled. Occasionally, rupture can be contained by the parietal pleura or occur towards the mediastin um, esophagus, pulmonary parenchyma, or bronchi. Untreated aneurysms w ill cause death in the majority of patients because of rupture. Recent data evaluating smaller and asymptomatic thoracic aneurysms with CT s can support nonoperative management and close follow-up of descending and thoracoabdominal aortic aneurysms only when the diameter is less t han 5 cm. Patients with Marfan syndrome may be operated upon with smal ler aneurysms. Independent of etiology, operative repair is the most e ffective means to alter the otherwise malignant course of descending a nd thoracoabdominal aortic aneurysms. The role of endovascular repair of these aneurysms remains to be established; however, it may represen t an alternative to treat thoracic aneurysmal disease in very high ris k patients.