Fibrosis and wall thickness affect ventricular repolarization dynamics in hypertrophic cardiomyopathy

Background Hypertrophic cardiomyopathy (HCM) is characterized by ventricular repolarization abnormalities and risk of ventricular arrhythmias. Our aim was to study the association between the phenotype and ventricular repolarization dynamics in HCM patients. Methods HCM patients with either the MYBPC3‐Q1061X or TPM1‐D175N mutation (n = 46) and control subjects without mutation and hypertrophy (n = 35) were studied with 24‐hr ambulatory ECG recordings by measuring time intervals of rate‐adapted QT (QTe), maximal QT, and T‐wave apex to wave end (TPE) intervals and the QTe/RR slope. Findings were correlated to specified echocardiographic and cardiac magnetic resonance imaging (CMRI) findings. Results Rate‐adapted QTe interval was progressively longer in HCM patients with decreasing heart rates compared to control subjects (p = 0.020). The degree of hypertrophy correlated with measured QTe values. HCM patients with maximal wall thickness higher than the mean (20.6 mm) had longer maximum QTe and median TPE intervals compared to control subjects and HCM patients with milder hypertrophy (p