Aortic medial elastic fiber loss in acute ascending aortic dissection.

The cause of acute aortic dissection continues to be debated. One school of thought suggests that underlying aortic medial cystic necrosis is the common denominator. The purpose of the present study was to determine if there was loss and, if so, how much loss of medial elastic fibers in the ascending aorta in patients with acute aortic dissection with the entrance tear in the ascending aorta. We examined operatively excised ascending aortas in 69 patients having acute dissection with tears in the ascending aorta. Patients with previous aortotomy, healed dissection, and connective tissue disorders were excluded. The 69 patients' ages ranged from 31 to 88 years (mean 56); 49 were men and 20 were women. Loss of aortic medial elastic fibers was graded as 0 (no loss), 1+ (trace), 2+ (mild), 3+ (moderate), and 4+ (full thickness loss). Of these 69 patients, 56 (82%) had 0 or 1+ elastic fiber loss; 13 patients (18%), 2+ to 4+ loss including 4 with 2+, 6 with 3+, and 2 with 4+. Nearly all patients (97%) had a history of systemic hypertension and/or had received antihypertensive drug therapy. In conclusion, most patients (82% in this study) having acute aortic dissection with entrance tears in the ascending aorta have normal numbers or only trace loss of aortic medial elastic fibers. Thus, underlying abnormal ascending aortic structure uncommonly precedes acute dissection.