Histological Patterns and Aortic Elasticity in Bicuspid vs. Tricuspid Aortopathy

Background: Bicuspid aortic valve (BAV) related aortopathy is known to significantly increase the rate of thoracic aortic aneurysms. Whether BAV or tricuspid aortic valve (TAV) aortopathy patients have a higher risk of dissection at the same diameter is the subject of current scientific discussions. Therefore, we compared histological changes of aortic tissue and aortic elasticity between BAV and TAV patients.

Methods: A total of 97 patients who underwent surgery for ascending aortic aneurysm at our center between 12/2020 and 12/2022 were included in the study. Aortic distensibility was studied using transthoracic echocardiography measuring the change of the aortic diameter between diastole and systole and adjusted by the blood pressure. In paraffin sections of intraoperatively excised aortic tissue samples, alterations were characterized according to international guidelines. Aortic distensibility and histological patterns were compared between BAV and TAV. To adjust for differences in baseline characteristics, comparisons were performed using logistic regression.

Results: Of the entire cohort, 29 patients (29.9%) had bicuspid aortopathy. There was no significant difference in the maximum aortic diameter (TAV 5.4 ± 1.1 cm, BAV: 5.3 ± 0.8 cm; p = 0.350) or aortic distensibility between the groups (TAV: 0.0028 ± 0.0035 mmHg-1, BAV: 0.0036 ± 0.0051 mmHg-1; p = 0.544). Histological samples of the TAV group showed a higher rate of calcific atherosclerosis (TAV: 31.3%; BAV: 6.9%, adjusted p = 0.027), and a higher rate of severe mucoid extracellular matrix accumulation (TAV: 46.4%; BAV: 10.3%, adjusted p = 0.005). Additionally, we could identify significantly higher rates of severe elastic fiber fragmentation (TAV: 65.7%; BAV: 24.1%, adjusted p = 0.001), severe elastic fiber thinning (TAV: 61.2%; BAV: 31.0%, adjusted p = 0.025) and extensive elastic fiber disorganization (TAV: 68.7%; BAV: 44.8%, adjusted p = 0.040) in TAV samples. Furthermore, a higher rate of severe smooth muscle cell loss (SMCL) (TAV: 52.2%; BAV: 20.7%, adjusted p = 0.022) and severe medial fibrosis was found in TAV patients (TAV: 53.7% vs. BAV: 20.7%, adjusted p = 0.008).

Conclusion: There was no significant difference in aortic distensibility between TAV and BAV aortopathy patients. However, despite no significant differences in diameter, we found significantly more severe histological changes in patients with TAV when compared to BAV aortopathy. Whether these histological changes translate into a higher dissection risk in TAV patients, needs to be evaluated in future prospective studies.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
13 February 2024