Aortic valve morphology rather than aortic valve function, aortic dilatation, and age interferes with ascending aortic structural and biomechanical properties

Abstract

Aortic valve (AV) malformation and AV malfunction have been linked to aortic wall degeneration. Studies concomitantly assessing AV morphology, AV function, age, ascending aortic dilatation, and aortic biomechanical properties are lacking. This exploratory study aims to close this gap. Surgical samples of the ascending aorta (n=102) were histologically assessed. Based on echocardiographic studies, the elastic modulus (slope stress-strain curve) was calculated. Patient characteristics were collected from the patient charts. Samples obtained during autopsy (n=10) served as reference for the microscopic analysis. The patient characteristics, structural aortic wall changes, and biomechanical wall properties were statistically explored using comparative analyses and a Spearman correlation matrix. Marked medial degeneration was found significantly earlier in life for unicuspid AV morphology compared to bicuspid and tricuspid AV. Significantly fewer lamellar units and thinner aortic walls were found in surgical samples compared to the reference group regardless of AV morphology, AV function, age, and aortic dilatation. Adventitial structural impairment was associated with stiffer aortic walls. Hints were found that AV morphology (rather than AV function, age, and presence/absence of aortic dilatation) affects structural and functional ascending aortic wall properties. Additionally, the observations suggest more advanced aortic degeneration in association with unicuspid AV, underpin the need for non-surgical control samples in surgical pathological studies, and highlight the importance of the adventitial layer for aortic biomechanics.