Left ventricular septal convexity in differentiating hypertrophic cardiomyopathy from hypertensive heart disease – cardiac MRI study

Subjects with hypertrophic cardiomyopathy (HCM) and hypertensive heart disease (HHD) have left ventricular hypertrophy (LVH). It is a common clinical problem to distinguish HCM from HHD. Septal convexity (SC) into the left ventricle is increased in subjects with hypertrophic cardiomyopathy (HCM)-causing mutations with and without LVH.Our objective was to study if SC by cardiac magnetic resonance (CMR) differentiates between HCM and HHD.We measured SC in 29 subjects with hypertension and LVH (left ventricular maximal wall thickness (LVMWT) ≥13 mm), in 49 subjects with HCM (LVMWT ≥13 mm) caused by the D175N mutation in the alpha-tropomyosin (TPM1) or the Q1061X mutation in the myosin binding protein C (MYBPC3) genes, and in 20 healthy controls with no LVH. SC into the LV was measured in end-diastolic 4-chamber images as the maximal distance between LV septal endocardial border and a line connecting septal mid-wall points at the level of tricuspid valve insertion and at the level of apical right ventricular insertion on the LV.Subjects with HCM had significantly increased septal convexity compared to subjects with HHD both in non-indexed and in BSA-indexed measurements (10.7±4.0 mm vs 4.9±2.7 mm, P\lt;0.001 and 5.5±2.1 mm/m2 vs 2.4±1.3 mm/m2, P\lt;0.001). To differentiate between HCM and HHD, septal convexity cutoff value of 7.85 mm performed best with sensitivity of 77\0\indexed SC cutoff value of 3.68 mm differentiated between HCM and HHD with sensitivity of 81\6\ Private grant(s) and/or Sponsorship. Main funding source(s): Finnish Foundation of Cardiovascular Research, the special governmental subsidy for health sciences research of the University Hospital of Kuopio