Hyperthermia Influences the Effects of Sodium Channel Blocking Drugs in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Introduction
Fever can increase the susceptibility to supraventricular and ventricular arrhythmias, in which sodium channel dysfunction has been implicated. Whether fever influences the efficacy of sodium channel blocking drugs is unknown. The current study was designed to investigate the temperature dependent effects of distinct sodium channel blocking drugs on the sodium currents in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).
Methods and Results
hiPSC-CMs were generated from human skin fibroblasts of a healthy donor. The peak and late sodium currents (INa), steady-state activation, inactivation and recovery from inactivation of INa in hiPSC-CMs were analyzed using the whole-cell patch clamp technique. The effects of different concentrations of the antiarrhythmic drugs flecainide, lidocaine, ajmaline and the antianginal drug ranolazine on INa were tested at 36°C and 40°C. Increasing the temperature of the bath solution from 36°C to 40°C enhanced the inhibition of peak INa but reduced the inhibition of late INa by flecainide and lidocaine. By contrast, increasing the temperature reduced the effect of ajmaline and ranolazine on the peak INa but not late INa. None of the tested drugs showed temperature-dependent effects on the steady-state activation and inactivation as well as on the recovery from inactivation of INa in hiPSC-CMs.
Conclusions
Temperature variation from the physiological to the febrile range apparently influences the effects of sodium channel blockers on the sodium currents. This may influence their antiarrhythmic efficacy in patients suffering from fever.