SK channels and ventricular arrhythmias in heart failure.

Small-conductance Ca(2+)-activated K(+) (SK) currents are important in the repolarization of normal atrial (but not ventricular) cardiomyocytes. However, recent studies showed that the SK currents are upregulated in failing ventricular cardiomyocytes, along with increased SK channel protein expression and enhanced sensitivity to intracellular Ca(2+). The SK channel activation may be either anti-arrhythmic or pro-arrhythmic, depending on the underlying clinical situations. While the SK channel is a new target of anti-arrhythmic therapy, drug safety is still one of the major concerns.