INTRODUCTION: Atrial pacing maps are often used as substitutes for sinus rhythm (SR) maps to expedite mapping procedures. However, the impact of this method on electrophysiological parameters has not been systematically examined. This study aimed to elucidate the advantages and limitations of atrial pacing maps. METHODS AND RESULTS: In 21 patients undergoing catheter ablation for atrial fibrillation, left atrial (LA) substrate maps using an HD-grid catheter were performed during SR, and pacing from the sinus-node region with cycle lengths (CLs) of 300 ms (SN-P300) and 600 ms (SN-P600). Mapping time, omnipolar voltage, peak-frequency of electrograms, and global LA activation time were compared among the three maps. The SR-map more frequently required automap-setting changes (p <
0.01), and one SR-map was not completed due to CL-fluctuation. Compared to SR, mapping time significantly decreased (833 [702-1097] seconds for SR vs. 615 [530-700] seconds for SN-P600 and 463 [404-542] seconds for SN-P300, p <
0.01). Mean voltage and peak-frequency of electrograms significantly decreased in SN-P600 and SN-P300 (mean voltage: 2.5 [2.1-3.2] mV for SR vs. 2.3 [2.1-2.8] mV for SN-P600 and 2.2 [2.0-2.7] mV for SN-P300, p <
0.01
mean peak-frequency: 308 [299-325] Hz for SR vs. 303 [288-314] Hz for SN-P600 and 281 [258-295] Hz for SN-P300, p <
0.01). The wavefront collision site shifted in 3/20 (15%) between SR and SN-P600, remaing within 30° along the mitral annulus, but this shift reached 9/20 (45%) between SR and SN-P300, including one patient showing a shift up to 60°. CONCLUSION: SN-P maps provide faster, higher-resolution substrate maps, but the amplitude and frequency of electrograms may be reduced as the CL shortens. Maps with SN-P600 may be acceptable, maintaining electrophysiological information in SR.