We assessed the hypotheses that extension of aortic replacement would reduce the patency of the false lumen of the descending aorta and that postoperative patency of the false lumen would result in poor prognosis. One hundred and twenty-four consecutive patients underwent surgical repair for acute type A acute dissection on an emergency basis. Among the 124 patients, 89 patients had De Bakey type I dissection. Among the patients with De Bakey type I dissection, the false lumen of the descending aorta was preoperatively patent in 52 patients. Distal extent of aortic replacement was ascending aorta in 16 patients, hemiarch in 15 patients, partial arch in seven patients, and total arch in 11 patients. Patency of the false lumen was not influenced by distal extent of the aortic replacement. In a one-year follow-up, the maximum diameter of the descending aorta with patent false lumen had increased significantly than that with closed false lumen. Survival rates were 96% at one year and 67% at five years in the patients with patent false lumen and no mortality in the patients with closed false lumen. Patency of the false lumen was not influenced by extension of aortic replacement and associated with poor prognosis.