Evaluation of myocardial structure and function in hypertrophic obstructive cardiomyopathy via cardiovascular magnetic resonance: regional distribution and sex differences.

Background: Although hypertrophy and fibrosis have been identified as contributors to mechanical dysfunction in patients with hypertrophic cardiomyopathy (HCM), their regional distribution and sex differences remain inadequately characterized in those with hypertrophic obstructive cardiomyopathy (HOCM). This study aimed to evaluate the determinants of myocardial strain deterioration across different regions and sexes of patients with HOCM through use of cardiovascular magnetic resonance feature tracking (CMR-FT) techniques.

Methods: This retrospective study included 102 patients with HOCM who underwent 3.0-T CMR. Global (G) and reginal left ventricular (LV) myocardial peak-strain parameters, including global longitudinal strain (GLS), global circumferential strain (GCS), and global radial strain (GRS), were derived via CMR-FT. Structural metrics including LV wall thickness (WT), hypertrophic distribution, late gadolinium enhancement percentage (LGE%), and extracellular volume fraction (ECV%) were comprehensively assessed. Bivariate correlation and multivariate linear regression analyses were performed to evaluate the independent associations and interaction effects of hypertrophic regions and sex on strain indices.

Results: Strain indices exhibited stronger correlations with hypertrophy as compared to fibrosis markers, with correlation coefficients of GLS, GCS, and GRS of -0.72, -0.58, and 0.55, respectively, while mean WT had stronger correlations than did LGE%, at -0.56, -0.55, and 0.51, respectively. Mean WT demonstrated the strongest correlation with GLS, outperforming max WT, hypertrophic segment count, and WT variation. Mean WT emerged as the strongest independent predictor of global strain (GLS: B=0.79; GCS: B=0.54; GRS: B=-1.38; all P values <0.001). ECV% was also independently associated with GLS (B=0.25) and GCS (B=0.16), while WT variation was associated with GCS (B=5.49) (all P values <0.05). Interaction analyses revealed significantly greater strain impairment in female patients and apical regions as WT increased (all P values <0.001).

Conclusions: Mean WT emerged as the most robust structural determinant of myocardial strain impairment in patients with HOCM, surpassing other hypertrophic characteristics and fibrosis surrogates. Notably, functional deterioration was most prominent in the apical regions and among female patients. These findings highlight the importance of incorporating sex-specific and region-specific hypertrophic patterns into individualized diagnostic and therapeutic strategies to improve clinical outcomes.