Imaging-Based Phenotyping in Bicuspid Aortic Valve and Associated Aortopathy: A Retrospective Single-Center Study

Background and Objectives: Bicuspid aortic valve (BAV) is a common congenital cardiac abnormality frequently associated with aortopathy and progressive aortic dilatation. The 2021 International consensus statement introduced standardized phenotypic definitions for BAV and BAV-associated aortopathy. The aim of this study was to determine the distribution of BAV and BAV-associated aortopathy phenotypes according to the 2021 consensus statement and to assess statistical differences between imaging modalities (magnetic resonance imaging (MRI) and transthoracic echocardiography (TTE)) in aortic diameter measurements. Materials and Methods: This single-center retrospective study included 47 patients with BAV between 2014 and 2018. Aortic root and ascending aorta diameters were measured using MRI white-blood and black-blood sequences and TTE. BAV morphology and aortopathy phenotypes were classified according to the 2021 International consensus recommendations, and agreement between modalities was assessed using correlation and Bland–Altman analysis. Results: The study population had a mean age of 30 ± 11.05 years, with a male-to-female ratio of approximately 3.3:1. The fused BAV phenotype was the most prevalent (53.2%), followed by the partial-fusion (38.3%) and two-sinus (8.5%) phenotypes (p < 0.001). Aortopathy phenotypes assessed by MRI and TTE demonstrated similar distribution patterns, with the extended phenotype being the most frequent, followed by ascending and root phenotypes, with no significant difference between modalities (p = 0.74). Strong correlations were observed across all imaging techniques for both ascending aorta and aortic root measurements; however, small but statistically significant differences were identified between selected modality pairs—a mean difference of 1.59 mm between MRI black-blood and TTE ascending aorta diameters and 1.26 mm between MRI white-blood and TTE aortic root diameters. Conclusions: Multimodality imaging demonstrates strong agreement in the assessment of aortic diameters and yields comparable aortopathy phenotype distributions when applying the 2021 International Consensus Classification. Nevertheless, small systematic measurement differences between MRI and TTE may be clinically relevant in patients approaching diagnostic or therapeutic thresholds, highlighting the importance of consistent imaging methodology in longitudinal follow-up of BAV-associated aortopathy.