Ion mechanism of isoproterenol on delayed afterdepolarization and triggered activity in the infarcted ventricle

Objectives This study aimed at investigating the cellular mechanism of isoproterenol (ISO) on delayed after depolarizations (DADs) and triggered activity (TA) of the noninfarcted myocardium in the myocardial infarcted rabbit model. Methods Rabbits with the left anterior descending coronary artery occlusion were prepared and recovered for 8 wk (healed myocardial infarction, HMI). Myocytes were isolated from regions of the noninfarcted left ventricular free wall. ISO was added to cellular surface by perfusion way. Action potentials and ion currents were recorded with whole-cell patch clamp. Results The results showed that treatment with ISO induced more DADs and TA events in HMI myocytes. Inward transient current (Iti) and ICa-L of myocytes treated with ISO were increased significantly compared with HMI cells, which contributed to DADs-related triggered arrhythmia. Conclusions The results suggested that more arrhythmia events of DADs and TA developed in myocytes with ISO treatment. The underlying mechanism was associated with the augment of Iti and calcium influxing.