AP14145 is an inhibitor for small conductance calcium-activated potassium channel , inhibits K Ca 2.2 channel and K Ca channel with IC 50 of 1.1 μM and 1.1 μM. AP14145 prolongs atrial effective refractory period (AERP) in rats, causes the conversion of atrial fibrillation to sinus rhythum in porcine left ventricular dysfunction models, and exhibits antiarrhythmic effect.