In summary, alteration of miR-221 and -222 expression can contribute to changed L-type Ca2+ channel density, GIRK1/4 density, and, perhaps, Kir2.1 density resulting in slower excitation propagation and possibly disturbed electromechanical coupling, prolonging the QT interval, and thereby making the heart more vulnerable to arrhythmias. Here, KCNJ2 is linked to cardiac arrhythmia.