Left ventricular septal convexity in differentiating hypertrophic cardiomyopathy from hypertensive heart disease – a cardiac magnetic resonance study

Both hypertrophic cardiomyopathy (HCM) and hypertensive heart disease (HHD) are characterized by left ventricular hypertrophy. Distinguishing HCM from HHD is a common clinical problem, particularly in subjects with moderate left ventricular maximal wall thickness (LVMWT) < 18 mm. Previously, we showed that cardiac magnetic resonance (CMR)-derived septal convexity (SC) into the left ventricle is increased in subjects with HCM-causing mutations with and without LVH. Our objective now was to determine whether CMR-derived SC differentiates HCM from HHD. We measured the maximal distance between the LV septal endocardial border and a line connecting the proximal and distal septal mid-wall points in 4-chamber images, in subjects with hypertension and LVH (n = 29), in subjects with HCM (n = 49), and in healthy controls (n = 20). Here, we show significantly increased SC in subjects with HCM compared to subjects with HHD both in non-indexed and in BSA-indexed measurements. Cutoff SC values of 7.9 mm and 3.7 mm/m2 in all HCM patients and SC values of 7.9 mm and 3.8 mm/m2 in HCM patients with LVMWT < 18 mm differentiated between HCM and HHD with good sensitivity and excellent specificity: SC cutoff value of 7.9 mm had a sensitivity of 77% and a specificity of 90% in all HCM patients, and 67% and 90% in HCM patients with LVMWT < 18 mm, respectively. Our study shows that measuring CMR-derived septal convexity is straightforward and enhances diagnostic performance, providing a novel technique to distinguish between HCM caused by sarcomere mutations and hypertension-induced LVH.