The ascending aorta with bicuspid aortic valve: a phenotypic classification with potential prognostic significance

Abstract

Objectives: Different methods to classify the anatomical configurations of the aorta with bicuspid aortic valve (BAV) have been proposed. We aimed to test them in terms of descriptive power (i.e. capability to identify different clusters of patients with unique associations of anatomo-clinical features) and possible prognostic significance.

Methods: A consecutive echocardiographic series of 696 BAV patients (mean age 48 ± 16 years, male:female ratio 3:1) was analysed. Three possible schemes for classification of the patterns of aortic dimensions were compared. One defined the aortic shape as 'N' (ascending < sinuses > sinotubular junction (STJ)), 'A' (ascending > sinuses > STJ) or 'E' (sinotubular ≥ sinuses), the second as 'non-dilated', 'ascending phenotype' (dilated, with ascending > sinuses) or 'root phenotype' (dilated, with sinuses > ascending) and the third as normal, 'type I' (dilated only at the ascending tract), 'type II' (dilated at both ascending and sinus levels) or 'type III' (dilated only at the sinuses). We evaluated the correlation with valve morphotypes (right-left fusion, right-non-coronary fusion) and patient characteristics. In a smaller longitudinal study (n = 150), the occurrence of fast growth of the aorta (fifth quintile: ≥1 mm/year) during follow-up (5 ± 3 years) in the various phenotypes was assessed.

Results: The three classification methods proved meaningful in terms of association with valve morphotypes: significant associations were found between right-left-coronary BAV and the root phenotype (P < 0.001) and between the right-non-coronary BAV and the shapes A and E (P<0.001) as well as type I aortic configuration (P < 0.001). The aortic shape showed significant association with five of the other tested clinical variables, the phenotype and the type of dilatation with eight. In the longitudinal study, the root phenotype showed the most significant association with fast growth (>1 mm/year) of the ascending diameter (50% root phenotype patients; P = 0.005). The association with the N type was weaker (P = 0.055); no association was found with types from the other classification scheme (P = 0.42).

Conclusions: When tested on a large population, three previously suggested phenotypic classifications of the BAV aorta proved to categorize patients into significantly different clusters, but only the classification system distinguishing between ascending phenotype and root phenotype showed a potential prognostic value. Phenotypic class of the aorta could be a factor to integrate in future comprehensive models for risk stratification of BAV aortopathy.

Keywords: Aorta; Aortic dilatation; Bicuspid aortic valve; Classification; Echocardiography; Prognosis.