Association of left ventricular mass by 3D echocardiography with replacement fibrosis and arrhythmias in hypertrophic cardiomyopathy

Background: In hypertrophic cardiomyopathy (HCM), left ventricular (LV) mass has prognostic value, but is challenging to quantify by two-dimensional echocardiography(2DE) because geometric assumptions are violated in asymmetric LV hypertrophy. Three-dimensional echocardiography (3DE) enables volumetric quantification of LV mass without geometric assumptions.Objectives: This study aimed to: (1) compare the accuracy of 3DE- and 2DE-derived LV mass against cardiac magnetic resonance (CMR); (2) evaluate the association of3DE-derived LV mass with ventricular arrhythmias and extensive myocardial fibrosis on late gadolinium enhancement (LGE) CMR (≥15% of LV mass).Methods: We studied 174 HCM outpatients (56±17 years; 59% men) who underwent 2DE, 3DE, and CMR. Accuracy of 2DE and 3DE compared with CMR was assessed in77 patients in whom CMR was performed within 6 months of echocardiography.Results: In the accuracy subset, 3DE LV mass correlated more strongly with CMR than 2DE (r=0.85 vs. r=0.62, both p<0.001) and showed lower bias (3DE: 3 g/m2; 2DE: 66g/m2). In the full cohort, non-sustained ventricular tachycardia (NSVT) occurred in 54 patients (31%) and LGE ≥15% in 60 (34%). No major ventricular arrhythmias wererecorded. In multivariable models, 3DE LV mass was independently associated with NSVT and LGE ≥15% (odds ratio 1.04, 95% CI 1.01 – 1.07, p-value 0.004), whereas 2DE-derived LV mass was not. ROC analysis identified optimal 3DE LV mass thresholds of 84 g/m2 and 86 g/m2 for NSVT and LGE ≥15%.Conclusions: In HCM, 3DE LV mass is more accurate than 2DE and independently associated with NSVT and extensive myocardial fibrosis.