Figure 5: (a) Surface electrocardiogram during ventricular entrainment showing entrainment with concealed fusion. (b) Surface electrocardiogram-leads I, aVF, V1, V6 and intracardiac electrograms – RFD (mapping and ablation distal), RFP (mapping and ablation proximal), his bundle electrogram distal, his bundle electrogram proximal – showing post entrainment response