Multi-modal diagnostic agreement and accuracy of bicuspid aortic valve classification

Introduction Bicuspid aortic valves (BAV) present in a variety of valvular morphotypes. A new International Consensus Classification and Nomenclature [1] was recently introduced, including 3 types of BAV: (i) the 3-sinus fused type, further divided into right-left (RL), right-non-coronary (RN) and left-non-coronary (LN) cusp fusion phenotypes, (ii) the 2-sinus type, including latero-lateral (LL) and antero-posterior (AP) phenotypes, and (iii) the partial-fusion (forme fruste) type. This classification establishes unified criteria to differentiate BAV phenotypes, enabling better prognostic and therapeutic evaluation and improving the understanding of disease progression, genetics, and clinical outcomes. Purpose To describe the prevalence of BAV morphotypes according to this new classification and evaluate the inter-observer agreement and diagnostic accuracy on computed tomography (CT) and echocardiography. Methods This is a secondary analysis of patients with BAV enrolled in a randomized clinical trial where transthoracic echocardiography (TTE) and contrast-enhanced CT were acquired [2]. Two blinded observers characterised the BAV type according to the number of Valsalva sinuses by CT, which was followed, in case of disagreement, by discussion and consensus. Two observers further characterized the number of sinuses, the fusion phenotypes and the presence of partial fusion in TTE images. Results One-hundred forty-six patients from 9 centers were included in this analysis: they were mostly middle-aged (median and inter-quartile age 45 [38-53] years) men (81%). Nineteen patients (13%) presented two-sinus BAV. On CT, inter-observer agreement on the presence of 2 vs 3-sinus BAV was 92.5%. As compared with CT-based consensus, the diagnostic accuracy of 2 vs 3-sinus BAV on TTE was 88.4%: the errors being mostly missing 2-sinus BAV (over 17 misclassifications, 16 (94%) where due to missing 2-sinus BAV), resulting in a low sensitivity, as only 16% of 2-sinus BAV were correctly identified. Notably, both observers missed the same 16 2-sinus BAV on echocardiography, meaning that the inter-observer agreement on this classification was 100%. The inter-observer agreement of 3-sinus fusion types on TTE was 93%, with disagreement mainly due to different classification between RL and RN fusions (7 over 10 disagreements, 70%). The inter-observer agreement of partial fusion on TTE was 96.6%, with only 5 patients classified differently by the two blinded observers. Conclusions The inter-observer agreement in the application of the new International Consensus Classification and Nomenclature for BAV by echocardiography is high. As a substantial number of 2-sinus BAV may be missed by echocardiography, multi-modal imaging should be considered when distinguishing 2 and 3-sinus BAV holds clinical relevance for decision-making. Future studies should confirm whether these variants exhibit significant differences in the progression of valvular or aortic disease.