Increased expression of EZH2 and H3K27me3 with enrichment in theScn5a promoter region after cardiac ischemia inhibits the promoteractivity of SCN5A, leading to decreased Nav1.5 expression and Na+channel activity, which underlie the development of cardiac arrhythmias.Application of the selective EZH2 inhibitor GSK126 significantly increasedNa+ channel activity in HL-1 cardiomyocytes. The gene discussed is SCN5A; the disease is cardiac arrhythmia.