Purpose: The arrhythmogenic effect of stem cells transplantation (SCT) in an infarct myocardium is still unknown. We investigated arrhythmogenicity of SCT in rat cryo-infarct model. Materials and Methods: In rat cryo-infarct model, bone marrow mononuclear stem cells (MNSC, 1 × 107 cells) were transplanted into the infarct border zone (BZ) of the LV epicardium. We compared the optical mapping and inducibility of ventricular tachycardia/ fibrillation (VT/VF) among normal (n = 5), cryo-infarct (n = 6), and SCT rats (n = 6). Results: The VT/VF inducibility was higher in the cryo-infarct (47.2%, p = 0.001) and SCT groups (34.6%, p = 0.01) than in the normal group (12.8%). The induced VT/VF episodes persisted for more than 2 minutes in 4.3%, 26.4% and 17.3% in the normal, cryo-infarct and SCT group, respectively. In the SCT group, the action potential duration at 70% was shorter at the SCT site than the BZ during SR (75.2 ± 8.1 vs. 145.6 ± 4.4 ms, p = 0.001) and VT (78.2 ± 13.0 vs. 125.7 ± 21.0 ms, p = 0.001). Conduction block was observed at the SCT site and BZ during VT. However, no reentry or ectopic foci were observed around the SCT sites. Conclusion: The electrical conduction was improved by SCT without evidence of augmentation of arrhythmia in the rat cryo-infarct model.
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