Specific HDAC inhibitor reverses atrial fibrosis and diminishes atrial fibrillation vulnerability following electrical stimulation. Micro-RNAs (miR-1) are essential in normal electrophysiological conduction and their deletion is associated with a high rate of sudden death Overexpression of miR-208a is also associated with arrhythmia and heart death Increases in miR-133a leads to prolonged QT intervals. MicroRNAs miR-212, miR-17-92, miR-155, miR-181, and miR-181a have been associated with the regulation of heart rhythm through the regulation of ion channels, transporters, and cellular proteins. The gene discussed is HDAC9; the disease is Arrhythmia.