Role of inward rectifier potassium current on drug therapy of atrial fibrillation

An S1-S2 stimulus protocol was used to test membrane threshold and subthreshold inactivation in relationship to prematurity and the conductance of IK1 (gk1). Results indicated that (1) required charge threshold for S2 was exponentially related to gk1 regardless of coupling interval both of normal and of fibrillation-induced cells; and (2) peak of sodium currents initiated by S2 was parabolically related to baseline gk1 with 70% maximum sodium currents occurring at 33% reduced gk1 in the fibrillation induced model cell only.