Myocardial remodeling in obstructive hypertrophic cardiomyopathy patients treated with mavacamten

Abstract Introduction Mavacamten, a cardiac myosin inhibitor, effectively reduces left ventricular outflow tract (LVOT) gradients by lowering myocardial contractility and is approved for the treatment of obstructive hypertrophic cardiomyopathy (oHCM). Aim To evaluate the impact of mavacamten treatment on myocardial structural remodeling and ventricular functional parameters assessed by cardiac magnetic resonance (CMR). Methods We performed a prospective, multicenter, observational study including patients with oHCM who initiated mavacamten therapy and underwent CMR imaging at baseline and after six months of treatment. CMR parameters were collected, including: left and right ventricular index volumes and ejection fraction, stroke volume index (SVi), indexed LV mass (iLV mass), maximum wall thickness (MWT), native T1 mapping, LV late gadolinium enhancement (LV LGE) percentage, and myocardial deformation assessed by ventricular feature tracking strain (longitudinal, circumferential, and radial). Changes in CMR measurements between baseline and follow-up (FU) were analysed using paired t-tests. In addition, strain parameters were compared between patients who experienced a significant reduction in LVEF (>10%) and the remaining patients using independent t-tests. Results 27 patients were included, with a median age of 67.0 [IQR 58 – 75],; 44.4% male. During FU, one patient permanently discontinued mavacamten due to a significant decline in LVEF. Regarding CMR parameters (Table 1), no statistically significant differences were observed regarding LVEDVi, RVEDVi and LV LGE percentage. There were significant increases in LVESVi and RVESVi and a significant decrease was observed in SVi, iLV mass, MWT, right and left ventricular ejection fractions and native T1 mapping values. Patients who experienced a significant reduction in LVEF at FU showed a consistent decline across all three strain categories - longitudinal circumferential, and radial. In contrast, patients without a significant reduction in LVEF showed a slight improvement in these strain parameters over follow-up. Conclusion In our cohort, treatment with mavacamten was associated with a reduction in LV mass, MWT and native T1 mapping values. Mild reduction in LVEF at 6-month FU was noted without impairment in ventricular strain. However, among patients with significant decline in LVEF, a parallel deterioration in all types of ventricular strain was observed.CMR parametersFor image description, please refer to the figure legend and surrounding text.Strain comparisonFor image description, please refer to the figure legend and surrounding text.