KCNN2 and atrial fibrillation: Complementary molecular, biophysical, and molecular methods were used and showed that (1) SK2 and SK3 channels are present in the porcine atria in both HC and in pigs with vernakalant-resistant AF, (2) AP14145 is a reasonably potent and selective inhibitor of the SK3 current, and (3) SK channel inhibition by AP14145 selectively prolongs the refractory period in porcine LA but not in the LV.