Chen et al. used patch clamps and electrocardiograms (ECG) data to assess the effect of the gain-of-function S140G mutation on the KCNQ1/KCNE1 and KCNQ1/KCNE2 currents and found that this mutation caused development of atrial fibrillation by reducing APD and ERP in atrial myocytes. Here, KCNQ1 is linked to atrial fibrillation.