CHRONIC DISSECTION OF THE THORACIC AORTA - DIAGNOSIS, MANAGEMENT AND PROGNOSIS

Dissection of the thoracic aorta becomes chronic after the 14th day fo llowing the first signs of dissection. It may be ''primary'', that is to say diagnosed at the chronic stage, the acute stage having pased un diagnosed, or ''secondary'' because the dissection diagnosed in the ac ute 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. Mana gement consists in following up the outcome of the false lumen by succ essive examination every 6 to 9 months; in general, CT scan or magneti c resonance imaging are used for this follow-up ; transoesophageal ech ocardiography 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 th e operative risk is high should an acute complication occur with an im mediate threat to life. This indication should be maintained in sympto matic patients (signs of compression of a false aneurysm, painful reac tivation) after thorough preoperative preparations, given the poor pro gnosis of the natural history of chronic dissection of the thoracic ao rta irrespective of its site. In asymptomatic patients with aortic dia meters of more than 60 mm in the first segments of the aorta (ascendin g or transverse aorta), surgery provides better long-term survival rat es than medical management. In disease of the descending thoracic aort a, no difference in survival is observed between medical or surgical t reatment; the surgical indication should be more conservative, especia lly because of the high incidence of neurological complications (parap aresis-paraplegia) in the absence of peroperative medullary protection , which is always reproducible, effective and validated.