KCNH2 and ventricular ectopy: We therefore conclude that: (1) XSN is a class I and III antiarrhythmic multicomponent medicine; (2) The dose-dependent and completely reversible effect of XSN indicate a low toxicity property of XSN; (3) The discoveries that XSN blocks hNav1.5 and hERG backed by the PAP suppression and prolongation of APD are the cellular electrophysiological mechanism that support the clinical therapeutic effect of XSN in treating PVC and tachyarrhythmia in patients.