[Chronic dissection of the thoracic aorta. Diagnosis, management and prognosis].

Dissection of the thoracic aorta becomes chronic after the 14th day following the first signs of dissection. It may be "primary", that is to say diagnosed at the chronic stage, the acute stage having passed undiagnosed, or "secondary" because the dissection diagnosed in the acute period was treated medically or surgically. Its outcome depends on the evolution of the false lumen which may thrombose or remain patent and stable or increase in size and progress to a false aneurysm. Management consists in following up the outcome of the false lumen by successive examination every 6 to 9 months: in general, CT scan or magnetic resonance imaging are used for this follow-up; transoesophageal echocardiography is another possibility but, when repeated, is not always accepted by the patients. Antihypertensive therapy is essential as it improves long-term survival in all cases. Surgery is justified but the operative risk is high should an acute complication occur with an immediate threat to life. This indication should be maintained in symptomatic patients (signs of compression of a false aneurysm, painful reactivation) after thorough preoperative preparations, given the poor prognosis of the natural history of chronic dissection of the thoracic aorta irrespective of its site. In asymptomatic patients with aortic diameters of more than 60 mm in the first segments of the aorta (ascending or transverse aorta), surgery provides better long-term survival rates than medical management. In disease of the descending thoracic aorta, no difference in survival is observed between medical or surgical treatment: the surgical indication should be more conservative, especially because of the high incidence of neurological complications (paraparesis-paraplegia) in the absence of peroperative medullary protection, which is always reproducible, effective and validated.