Aortic aneurysms with tricuspid aortic valve have more degeneration than unicuspid aortic valve aneurysms

The unicuspid aortic valve (UAV) is a rare cardiac malformation and is associated with the formation of ascending aortic aneurysms. To characterize its associated aortic wall changes, normal and aneurysmatic ascending aortic wall specimens were analysed, focusing on the potential mechanisms of aneurysm formation. Patients with tricuspid aortic valve (TAV) served as controls.

In a retrospective observational study, 74 specimens (dilated and non-dilated aortas; individuals with UAV and TAV) obtained intraoperatively were studied. Standard stains and immunohistochemical labelling of cleaved caspase-3, cluster of differentiation 31 and endothelial nitric oxide synthase (eNOS) were performed to assess the degree of apoptosis, distribution of eNOS within the aortic wall, smooth muscle cell (SMC) nuclei loss and mucoid extracellular matrix accumulation (MEMA).

Deeper ingrowth of vasa vasorum was found in dilated aortas. Interestingly, eNOS was expressed mostly in vasa vasorum. More apoptosis was seen in UAV aortas compared to TAV aortas (P < 0.001). Both UAV and TAV aortas were comparable regarding SMC nuclei loss (P = 0.419). In dilated compared to non-dilated aortas regardless valve morphology SMC nuclei loss was increased (P = 0.005) and more pronounced translamellar MEMA was present (P = 0.011). The highest grade of distribution (P = 0.043) and the highest severity (P = 0.005) regarding MEMA were seen in TAV dilated specimens compared to UAV dilated specimens.

Aneurysms with UAV show increased apoptosis, the role of which is unclear. Strikingly, more severe MEMA was found in TAV aneurysms compared to UAV aneurysms. Thus, UAV-associated aortic wall changes and resulting aneurysm may be less aggressive than aneurysms with TAV.