cute aortic dissection has a poor prognosis without therapy. Since 1955, DeBakey et al have reported surgical treatment for aortic dissection and classified aortic dissections as 3 types. 1,2 Thereafter, a simpler categorization, the Stanford classification, was proposed in 1970. 3 The most proximal type dissection was subjected to surgery and the peripheral type dissection without severe complications was treated medically. In addition to the site of the aortic dissection, we are also able to detect the state of the false lumen. The thrombosed false lumen was detected by angiography in 1966 4 and by computed tomography (CT) scan in 1981. 5 Several investigators have reported that aortic dissection with thrombosed false lumen has a better prognosis than with open false lumen. However, the method of treating dissecting aorta with open or thrombosed lumen has not yet been clearly determined. The purpose of the present study is to evaluate the long-term prognosis of each type of aortic dissection undergoing medical treatment and to determine the factors that would indicate the most suitable treatment.We have previously reported the results of dissecting aorta with medical treatment. 6 The present study has more patients than in our previous report, and we can determine the condition of false lumen for diagnosing aortic dissection with thrombosed false lumen. MethodsThe subjects in the present study are 263 patients with Japanese Circulation Journal Vol.65, May 2001 aortic dissection medically treated only. They were selected from 541 patients admitted to the Internal Medicine Departments of Chiba University Hospital and 14 affiliated hospitals between 1973 and 1998. Aortic dissection was diagnosed based on the detection of 2 aortic lumens with blood flow or thrombus by enhanced CT, transesophageal echocardiography or autopsy. Patients with high blood pressure were administered antihypertensive drugs, and for a shock state dopamine or dobutamine was used. Although most patients with Marfan's syndrome were operated, there were 9 patients treated only medically. Patients who were found to have an aortic dissection at the chronic phase were excluded from the study. ClassificationAortic dissections are classified according to the site of dissection and the state of false lumen. In the present study, patients were classified into 4 groups: (i) Stanford type A dissection with open false lumen (AO group); (ii) Stanford type B dissection with open false lumen (BO group); (iii) Stanford type A dissection with thrombosed false lumen (AT group); and (iv) Stanford type B dissection with thrombosed false lumen (BT group). At first, the survival rate with medical treatment only was analyzed in each group. Second, the event-free rate was analyzed. Event was defined as death-related with dissection or re-dissection. Third, gender, age, maximum diameter of dissected aorta, and the presence of shock at onset were examined as factors related to the event. StatisticsThe survival rate and event-free rate were analyzed by the Kaplan-M...