Aortic dissection with the entrance tear in transverse aorta: analysis of 12 autopsy patients. Clinical and autopsy findings are described in 12 patients who had fatal aortic dissection with the entrance tear in the transverse aorta. The 12 patients represent 7% of 182 autopsies of spontaneous aortic dissection studied by us. The ages of the 12 patients at death ranged from 37 to 87 years (mean, 67 years). Eight were men; 8 had a history of systemic hypertension, and 10 had hearts of increased weight. Diagnosis of aortic dissection was made during life in only 4 of the 12 patients. All 12 patients died of rupture of the false channel within 2 weeks of onset of signs or symptoms compatible with dissection. The direction of aortic dissection from the entrance tear was entirely retrograde in 4 patients, entirely anterograde in 4 patients, and in both directions in 4 patients. Hemopericardium occurred in the first group, left hemothorax in the second group, and either in the last group. Of the 8 patients in whom the ascending aorta was involved, the retrograde dissection in each extended to the aortic root, 6 had pulmonary adventitial hemorrhage, and 4 had involvement of the arch arteries by dissection. In the 4 patients with strictly anterograde dissection, none had dissection in the arch arteries. Thus, tear in the transverse aorta causes a dissection that is usually fata, that often dissects retrogradely, and that may mimic dissection from a tear in ascending aorta. Aortic dissection from a tear in transverse aorta requires early operative intervention. 