Electrophysiological and Contractile Effects of Disopyramide in Patients With Obstructive Hypertrophic Cardiomyopathy: a Translational Study

•In patients with HCM and symptomatic LVOT-obstruction, first treatment with disopyramide leads to a marked reduction of LVOT gradients, with a slight decrease of resting ejection fraction and a modest increase of corrected QT interval, highlighting high efficacy and safety.•In single cardiomyocytes and intact trabeculae from surgical samples of patients with obstructive HCM, in vitro treatment with 5 μmol/l disopyramide lowered force and Ca2+ transients while reducing action potential duration and the rate of arrhythmic afterdepolarizations.•These effects are mediated by the combined inhibition of peak and late Na+ currents, L-type Ca2+ current, delayed-rectifier K+ current, and ryanodine receptors.•In addition to the negative inotropic effect of disopyramide, in vitro results suggest additional antiarrhythmic actions.