Genetics, patterns of hypertrophy and fibrosis on myocardial mechanics in hypertrophic cardiomyopathy

Abstract Funding Acknowledgements Type of funding sources: None. Background Asymmetrical hypertrophy, myocyte disarray and fibrosis due to genetic cause are underlying pathology of hypertrophic cardiomyopathy (HCM). However, their contribution to myocardial functional mechanics are not extensively evaluated yet. Purpose In this study, we sought to investigate effects of genetic mutation, patterns of ventricular hypertrophy and fibrosis on myocardial mechanics in HCM. Methods In 133 patients with HCM, chamber geometry, segmental late gadolinium enhancement (LGE), extracellular volume fraction (ECV) by cardiac magnetic resonance imaging (CMR), echo-derived diastolic function analyses and genetic test were performed. Left ventricular (LV) segmental and global longitudinal strain (LS), circumferential strain (CS), and rotation were measured by feature tracking analysis of CMR. Results Patients with sarcomere gene mutation (SM) had lower LV-CS (global and all three slices) along with higher prevalence of midwall type LGE, LGE amount and ECV. Despite global LS was not lower in SM, anteroseptal-LS was significantly impaired accompanying with higher septal wall thickness. To compensate impaired anteroseptal LS, basal endocardial rotation was paradoxically increased in SM. Augmented basal segmental was significantly related to obstructive HCM. In apical HCM, although apical segmental LS was significantly lower, higher apical rotation and preserved apical CS along with lower prevalence of SM. The E/e’ was significantly related to LV mass index, LGE extent but not with SM. Conclusion Circumferential myocardial function was significantly reduced in SM independent of fibrosis extent, suggesting primary phenotype. However, longitudinal fiber function was more related to hypertrophy regardless of SM. LV diastolic function was more related to LV mass, extent and degree of fibrosis including non-thickened myocardium regardless of SM.