[Late outcome of operated acute aortic dissection: risk factors analyzed from autopsy findings]

Based on analysis of 35 autopsy cases of aortic dissection, risk factors related to late outcomes, especially to aortic rupture after operation, are discussed. Pathological findings related to the entry into a persistent distal false lumen (PDFL) after surgical repair of aortic dissection are: 1) unresected initial intimal tear; 2) a new intimal tear, mainly related to the surgical suture; 3) disrupted aortic branches, and 4) penetrating atherosclerotic aortic ulcers (PAU). These also are common pathological findings in ulcer-like projections and may cause re-dissection. After operation, the pseudoneointima develops and covers the PDFL during 1 to 2 months, becoming stable thereafter. In the remaining thrombosed-type of dissection after operation, the hematomas become completely organized only when they are small. Late rupture of an aneurysm in both thrombosed and non-thrombosed types of dissection may be caused by new dissection or by re-dissection from the sites of entry listed above. The PAU is an especially important factor related to the aging of patients after the operation. The findings of adventitial accumulations of macrophages, which are known to express matrix metalloproteinases, at the sites of rupture suggested that these enzymes also contribute to the rupture of chronic aortic dissection.