An HCN channel blocker; blocks If in HEK293 cells expressing mouse HCN1, human HCN2, and human HCN4 (EC50s = 4.5, 4.52, and 4.28 μM, respectively); reduces heart rate, incidence of ventricular tachycardia and ventricular fibrillation, and arrhythmic mortality in a rat model of myocardial infarction at 10 mg/kg