Clinicopathological study on penetrating atherosclerotic ulcers and aortic dissection: distinct pattern of development of initial event.

An intimal tear is responsible for the development of aortic dissection (AD). Plaque rupture is thought to progress to a penetrating atherosclerotic ulcer (PAU). However, the influences of mechanical stress and atherosclerosis on the intimal tear of AD and plaque rupture of PAU have not been fully understood. We enrolled 27 patients with AD [67.6 ± 11.2 years, female/male (F/M) 12/15] and 10 patients with PAU (71.0 ± 8.64 years, F/M 2/8) who underwent aortic reconstructive surgery in our hospital between 2007 and 2011. We analyzed the clinical data and morphological features of these patients and discuss the role of mechanical stress in the initial event. On clinical examination, hypertension was frequently observed in the patients of both the AD (77.8 %) and PAU groups (90.0 %), while hypercholesterolemia was significantly more prevalent in the PAU group (90.0 %) than in the AD (22.2 %) group. Most lesions of AD (96.3 %) were found in the ascending aorta up to the aortic arch, while those of PAU (90.0 %) were found in the descending and abdominal aortas. On pathological examination, the entrance tear was found in 21 (77.8 %) of the 27 patients with AD, and histologically comprised nonatherosclerotic intima and media. In contrast, the entrance tear was considered as plaque ulcer in 8 (80.0 %) of the 10 patients with PAU. The patients with PAU showed a significantly higher prevalence of soft plaque, complicated lesions, and medial fibrosis than those with AD, whereas patients with AD showed no complicated lesions and had a significantly higher prevalence of cystic medial necrosis than those with PAU. The present study suggests that less atherosclerosis and impairment of media could proceed to intimal tear formation in AD and that the disruption of the fibrous cap could cause the plaque ulcer of PAU.