Medial Neovascularization: A Novel Mechanism of Aortic Dissection in a Hypertensive Population?

Background This study aimed to elucidate the impact of vasa vasorum on the natural progression of aortic dissection in patients with hypertension. Methods Full‐thickness ascending aortic walls from 43 participants (median age, 53 years; 32.6% women) were analyzed using pathological observation and shear stress measurement. Comparisons among hypertensive dissection (AD, n=23), hypertensive control (n=12), and nonhypertensive dissection (non–HT‐AD, n=8) groups were performed using Kruskal–Wallis and repeated‐measures ANOVA tests. Results Compared with the control group, a higher density of vasa vasorum was observed within the outer third of the tunica media (medial neovascularization [MN]) in the AD group (adjusted P =0.02). In the AD group, MN frequently coincided with the site of medial tearing, and the MN grade was higher than in the other 2 groups (overall: P =0.01; non–HT‐AD versus AD group: adjusted P =0.05; control versus AD group: adjusted P =0.05). Medial degeneration was observed in all of the groups. Compared with the non–HT‐AD group, the medial degeneration grade was even lower in the AD group (adjusted P =0.006). Multicenter fractures of elastic and collagen fibers were evident within the MN region in the AD group. Biomechanical testing revealed a significantly increasing translamellar discrepancy in stretch ranges inside the similar region ( P <0.001 for interaction; P column factor <0.001) in the AD group when compared with the control group. Conclusions MN and subsequent vasa vasorum rupture in the outer tunica media may represent an alternative initiating event in hypertension‐related aortic dissection, distinct from the classical intimal tear. However, the cross‐sectional nature of this study precludes definitive causal conclusions.