The LV effective refractory period was reduced by Blonanserin hypokalemia both in guinea-pig and rabbit hearts, which may be attributed, at least in part, to hypokalemia effects on the recovery of Na + channels from inactivation. In support of this argument, the recurrence of excitability during the repolarization phase was found to occur at less negative membrane potentials in hypokalemic guinea-pig papillary muscle, and this effect was abolished by Na + channel blocker. Reduced effective refractory period, in association with prolonged interventricular conduction time, contributed to a decreased value of the excitation wavelength index in hypokalemic guinea-pig and rabbit hearts in the present study. This change may set a stage for tachyarrhythmia, because a reduced excitation wavelength allows re-entry within a smaller mass of cardiac tissue to be sustained. Consistently, the runs of torsade de pointes were inducible by programmed LV stimulation in 70�C80% of hypokalemic heart preparations used in this study. These changes translated to amplified spatial repolarization gradients, as indicated by the increased standard deviation of the mean repolarization time value determined at six epicardial recording sites. Enhanced variability in the distribution of repolarization time across the ventricular epicardium may set a stage for unidirectional conduction block and re-entry, thus contributing to proarrhythmic effects produced by hypokalemia. The red swamp crawfish, Procambarus clarkii, is a species of freshwater crawfish native to the Southern central United States and Northeastern Mexico, and has become one of the most widely introduced crawfish species in the world. This species was introduced from Japan to Nanjing, China, in 1929. Since the 1990s, P. Cevimeline hydrochloride hemihydrate clarkii have been farmed extensively as food source and have become one of the most economically important farmed species in China. Due to its high market demand and high economic value, crawfish aquaculture has developed rapidly in the past decades. Owing to the growing culture industry, a shortage of juvenile crawfish has become prevalent, leading to severe restriction in large-scale crawfish aquaculture.