SCN5A and cardiac arrhythmia: Cardiac sodium channels are mainly encoded by the SCN5A gene in human cardiomyocytes.[3] Previous studies indicated that H558R polymorphism of the SCN5A gene was associated with lone AF.[4] Similarly, mutations in the SCN5A gene have been reported to change the function of sodium channels, leading to a further reduction in sodium influx, shortening of action potential duration, and then arrhythmia.[5]