SCN5A and cardiac arrhythmia: The evidence for chamber-specific differences in Na+ currents in the human heart have been also reported6,7.Many SCN5A variants have been reported to cause channelopathies that are responsible for cardiac arrhythmia and sudden death, including long QT syndrome8,9, Brugada syndrome10, conduction abnormalities11, atrial fibrillation12, and dilated cardiomyopathy13,14.