Abstract

Introduction: Ascending aortic aneurysms (AA) are a common, though poorly understood medical condition. In the present study we aim to document the histologic changes in a large series of human ascending AA, and to correlate these changes with clinical variables. Methods: 111 ascending AA were excised at surgery at our institution over a 3 year period. Each aneurysm was received as a continuous ring of tissue. Sections were taken from the anterior, posterior, greater and lesser curvature of the aorta and graded in a semiquantitative fashion for the degree of elastin fragmentation, elastin loss, smooth muscle cell (SMC) loss, intimal changes and inflammation. Results: Mean patient age at surgery was 58.7+/-15.6 years. There were 70 males and 41 females, 12 patients had Marfan syndrome, 34 (30.6%) had a bicuspid aortic valve (BAV) while 71 (64.0%) had a tricuspid aortic valve (TAV). Inflammatory cells were present in 28 cases (25.2%) and were confined to the adventitia. No particular region of the aortic circumference was more severely affected, however a BAV was associated with significantly less intimal change and less fragmentation and loss of elastic tissue compared with patients with a TAV. Advanced age (>65 years), female gender and Marfan syndrome were all associated with more severe elastin degeneration and smooth muscle cell loss (p<0.05 for all). Conclusion: These results indicate a wide variation in the histological appearance in ascending AA depending on patient characteristics. These results suggest that the underlying aneurysm pathogenesis may also be highly variable and warrants further investigation.