KCNJ2 and atrial fibrillation: By way of further comparison, in our previous study of a KCNJ2 mutation associated with familial AF, both the Kir2.1 V93I mutation which increases outward IK1 and a simple linear increase in maximal conductance of IK1 were shown to flatten APD and ERP restitution curves [17], consistent with observations in the present study.