Delayed-enhancement in hypertrophic cardiomyopathy is linked to a low coronary sinus flow independently from the left ventricular mass

Background: In Hypertrophic cardiomyopathy (HCM) fibrosis could be a consequence of disproportion between mass and coronary flow. Magnetic Resonance (MRI) allows to quantify fibrosis with delayed enhancement (DE) technique and to measure coronary sinus flow (CSF). Aim: to estimate the relation between coronary flow and mass in the development of fibrosis in HCM. Methods: Fifteen HCM patients (10 male, mean age 38 y) and 20 normal patients (11 male, mean age 35 y) underwent MRI examination. Left ventricular parameters were obtained with FIESTA images acquired in short axis views (30 phases, 8 mm slice thickness, no gap). CSF was measured by a Phase-velocity encoded images (venc 50 cm/sec) acquired orthogonal to the coronary sinus. DE images were acquired with IR GRE sequence with a TI to null myocardium in short axis views. Delayed hyper-enhanced (DHE) and mild-enhanced (MDE) regions were quantified. Results: CSF was not significantly higher in HCM patients (2.28±0.8 vs 2.41±1.3 ml), but the ratio CSF/mass was lower in HCM than in normal patients (12±4 vs 22±10x10-3 ml/grams, p<0.02). Ten HCM patients (66.6%) had a positive DE (DE-HCM), five patients (33.3%) showed a negative DE (No-DE-HCM). No differences were found in mass between DE-HCM and no-DE-HCM groups (189±33 vs 196±33 grams n.s.).CSF in DE-HCM group was lower than in No-DE-HCM (1.9±0.5 vs 3.1±0.6 ml, p<0.001). Yet, the ratio CSF/mass was lower in DE-HCM patients(11±4 vs 16±3x10-3 ml/gram, p<0.012). The extent of HDE and MDE significantly correlated with CSF and CSF/mass (fig. 1-2). Conclusions: in HCM a lower CSF per gram of mass than in normal patients was found. CSF was lower in HCM with positive DE than in those without, independently from the mass.The extent of HDE and MDE were inversely related to the coronary flow.