In homogeneity of cardiac electro physiology is existed in both normal and diseased hearts, which would be exacerbated by electrical or structural remodeling. Slow heart rate or decreasing repolarization reserve of action potential can enhance transmural heterogeneity and promote arrhythmia generation. In this study, we used optical mapping technique to investigate how pacing rate changing and Ikr blocker, Dofetilide, influence the heterogeneity of action potential duration between rabbit right and left ventricle simultaneously. The results showed that slowing pacing rate might increase the heterogeneity of inter-ventricles and there were early after depolarization (EAD) happening in right ventricle and inducing trigged activity in left ventricle at BCL of 2000ms. 30 nmol/L Dofetilide could prolong the APD in both right and left ventricle markedly at BCL of 2000, 1000, and 500ms. However, the increment of APD in right ventricle was 226 ± 96ms, and in left ventricle was 213 ± 100ms at BCL of 1000 ms, which demonstrated that Dofetilide did not increase the heterogeneity between two ventricles significantly (P > 0.05). The results suggested Dofetilide inducing Torsades de points (Tdp) because of increasing transmural dispersion of repolarization (TDR), instead of increasing heterogeneity between right and left ventricle.