TNNI3 and Ventricular arrhythmia: The therapeutic concentration of lapatinib significantly increased total peripheral vascular resistance, QT, QTc, monophasic action potential (MAP)90(sinus), MAP90(CL400), effective refractory period, and plasma concentration of cardiac troponin I (cTnI), suggesting that lapatinib prolonged the ventricular repolarization without inducing lethal ventricular arrhythmia.