C16 PROPENSITY SCORE COMPARISON OF ELASTIN–BASED AND COLLAGEN–BASED MECHANICAL PROPERTIES OF AORTIC WALL IN BICUSPID VS TRICUSPID AORTIC VALVE PATIENTS UNDERGOING AORTIC SURGERY

Objective

Several studies addressed characteristics of aortic wall in patients with bicuspid aortic valve (BAV) compared to those with tricuspid aortic valve (TAV). Different patients population and lack of randomization were the main limitations in many of such studies, focused furthermore, only on ultimate properties (at rupture). In this study we compared mechanical properties in BAV and TAV patients undergoing aortic surgery using propensity score analysis to obtain two homogeneous groups of patients. We also focused on both elastin–based and collagen–based mechanical properties.

Methods

Among 87 overall patients undergoing surgery of ascending aorta, 26 were selected, following propensity score analysis, and divided in 2 groups according the type of native aortic valve (13 BAV and 13 TAV). Mechanical tests were completed following circumferential and longitudinal force application. 137 cumulative tests were accepted (93 from anterior aortic wall). Aortic wall strain (marker of elasticity) and aortic wall stress (marker of strength) were measured either in the Elastin–based (initial) distension and in the Collagen–based ultimate distension (until rupture).

Results

Cumulative comparison of specimens thickness confirmed that anterior aortic wall is thinner in BAV patients. Aortic wall thickness, however was not correlated to any of mechanical tests in Elastin–based or Collagen–based distensions. Aortic wall elasticity and strength (applying either longitudinal and circumferential force) were not different in BAV compared to TAV patients. Initial and ultimate elasticity were significantly correlated either applying circumferential and longitudinal force. Direct correlation between initial and ultimate strength, on other hands, was showed only in BAV patients when a longitudinal force was applied.

Conclusions

We clearly showed that, in dilated aorta, anterior wall is thinner in case of BAV compared to TAV. Our study, furthermore, confirms that mechanical properties of aortic wall in BAV patients are no impaired, compared to an homogeneous group of TAV patients, neither in initial or ultimate tests. Elastin–based and collagen–based aortic wall mechanical properties (under circumferential force) are directly correlated regardless BAV presence. Lack of correlation between initial and ultimate strenght in TAV patients, under a longitudinal force, needs further evaluation as it could be related to an increased frailty of aortic wall in such conditions.