Systolic anterior motion of the anterior mitral valve leaflet begins in subclinical hypertrophic cardiomyopathy.

Anterior mitral valve leaflet (AMVL) elongation is detectable in overt and subclinical hypertrophic cardiomyopathy (HCM). We sought to investigate the dynamic motion of the aorto-mitral apparatus to understand the behaviour of the AMVL, and mechanisms of left ventricular outflow tract obstruction (LVOTO) predisposition in HCM. Cardiovascular magnetic resonance imaging (CMR) using 1.5 Tesla scanner was performed on 36 HCM sarcomere gene mutation carriers without left ventricular hypertrophy (G + LVH-), 31 HCM patients with preserved ejection fraction carrying a pathogenic sarcomere gene mutation (G + LVH+), and 53 age, sex and BSA-matched healthy volunteers.Dynamic excursion of the aorto-mitral apparatus was assessed semi-automatically on breath-held 3-chamber cine steady-state free precession images. Four pre-defined regions of interest (ROI) were tracked: ROIPMVL: hinge point of the posterior MVL; ROITRIG: intertrigonal mitral annulus; ROIAMVL: AMVL tip; ROIAAO: anterior aortic annulus. Compared to controls, normalized two-dimensional displacement-versus-time plots in G + LVH- revealed subtle but significant systolic anterior motion (SAM) of the AMVL (P < 0.0001) and reduced longitudinal excursion of ROIAAO (P = 0.014) and ROIPMVL (P = 0.048). In overt and subclinical HCM, excursion of the ROITRIG/AMVL/PMVL was positively associated with burden of LV fibrosis (p < 0.028). As expected, SAM was observed in G + LVH + together with reduced longitudinal excursion of ROITRIG (P = 0.049) and ROIAAO (P = 0.008). Dyskinesia of the aorto-mitral apparatus, including SAM of the elongated AMVL, is detectable in subclinical HCM, before the development of LVH or LA enlargement. These data have the potential to improve our understanding of early phenotype development and LVOTO-predisposition in HCM.

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© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.