Background Ventricular tachycardia (VT) and ventricular fibrillation are the main reasons causing sudden cardiac death.This study aimed to investigate the effects of nifekalant hydrochloride (NIF) on QT dispersion (QTd) in treating VT.Methods A total of 16 consecutive patients suffered sustained VT was included and then randomly divided into two groups according to the administration duration of NIF.In long-time group (group L), patients were injected with NIF continuously for at least 12 hours after a bolus dose.The patients in short-time group (group S) were injected with NIF just for 1 hour.Results There were 7 of all 10 episodes of VT which were terminated by NIF, including 4 episodes in group L were stopped over 1 hour after continuous infusion of NIF.One patient suffered from torsade de pointes.Electrocardiography analysis indicated that QTd was significantly decreased 12 hours after stopping of infusing NIF compared with that when VT stopped ((45.4±22.1) ms vs.(73.4±33.2) ms, P ＜0.01), and the corrected QTd (QTcd) decreased too ((47.8±22.9) ms vs.(78.3±36.5) ms, P ＜0.01 ).There was a positive correlation between the increase in QTd and dose of administrating NIF (P ＜0.01), so was QTcd (P ＜0.01).Conclusions More administration of NIF indicates higher terminating rate of VT and more QTd prolongation.However,the safety is acceptable if several important issues were noticed in using NIF, such as serum potassium concentration,stopping side-effect related agents, and carefully observing clinical responses.