AIM: To investigate the effect of hypoxia on persistent sodium current (I_Nap ) in single ventricular myocyte isolated from acute myocardial infarction (AMI) heart of rats and to study the mechanisms of cardiac arrhythmias that occur after AMI. METHODS: AMI model was induced by ligating the left anterior descending coronary artery in rats. The whole-cell patch clamp technique was used to record the current in epicardial myocytes in infarcted region from rats at 3 week after AMI. RESULTS: In normoxic conditions, the current density of I_ Nap in cardiomyocytes of fake operation (FO) and AMI hearts was 0.144?0.022 pA/pF (n=9), 0.121?0.013 pA/pF (n=9,P