Abstract 13075: Histopathological Analysis of Two Major Ascending Aortopathies: Implication of Vasa Vasorum Degeneration in Their Pathogenesis

Abstract

Introduction: Aortic medial weakness is a major predisposing factor in the development of aortic dissection or aortic aneurysm. Impaired vasa vasorum (VV) or venous vasa vasorum (VVV) function may induce hypoxia and malnutrition, possibly resulting in aortic medial weakness. Hypothesis: We hypothesized that the start of ascending aortopathy could be identified by histopathological analysis. Methods: We retrospectively evaluated 69 consecutive patients (28 men, 41 women; mean age 68.2 ± 12.1 years) who underwent ascending aortic repair from 2008 to 2015. The patients were divided into group AD (type A aortic dissection, n=47 ) and group AA (ascending aortic aneurysm, n=22). We evaluated patient characteristics and graded VV/VVV degeneration of the adventitia (none = 0, trivial = 0.5, mild = 1, moderate = 1.5, severe = 2) regarding elastoma formation, smooth muscle cell proliferation, myomatous change, and sclerosis. Results: There were no significant differences between the two groups regarding age, sex, body surface area, history of hypertension, or diameter of the ascending aorta before surgery. Four patients in group AD had gene-related aortic dissection (Marfan syndrome, three patients; bicuspid aortic valve, one patient). Nine patients in group AA had a bicuspid aortic valve. There were significant differences between the two groups in regard to smooth muscle cell proliferation [VV (group AD: 1.40 ± 0.49 points; group AA: 0.98 ± 0.19 points; p<0.001); VVV (group AD: 1.40 ± 0.55 points, group AA: 1.04 ± 0.51 points, p=0.013] and total degeneration score (VV: group AD: 3.17 ± 1.42 points, group AA: 2.39 ± 1.41 points, p=0.036). There were no significant differences between the two groups regarding myomatous change or sclerosis. Conclusions: Degeneration of the VV and, especially, smooth muscle cell proliferation of the VV and VVV appear to be responsible for aortic dissection. Elucidation of the smooth muscle degeneration pathway may lead to identifying the turning point at which aortic wall weakness induces dissection or enlargement.