Introduction: Coronary sinus (CS) and biatrial pacing have been reported to be more effective than right atrial appendage (RAA) pacing for preventing atrial fibrillation (AF). However, the effects of atrial pacing on hemodynamics are still unknown. Methods and Results: Eleven patients with AF who underwent PV isolation were studied. Two quadripolar electrode catheters were placed in RAA and CS. After a transseptal approach, a thermodilution catheter was introduced into the left superior pulmonary vein (LSPV). The mean LSPV pressure was directly measured during pacing from the distal site of the CS (CS-d) and RAA, and simultaneous pacing from CS-d and RAA. The P wave duration during pacing from the RAA+CS-d was significantly shorter than that during pacing from the RAA (83 ± 16 vs. 121 ± 18 ms, P < 0.05). No significant difference in LSPV pressure was found among the three pacing configurations (RAA, CS-d, RAA+CS-d pacing; 16 ± 7, 16 ± 4, 17 ± 3 mmHg, respectively). Conclusions: LSPV pressure was not affected by CS-d, or biatrial pacing. Shortening of the P wave duration by biatrial pacing may contribute to the prevention of AF. The electrophysiological effects of pacing may play a more important role in preventing AF rather than the hemodynamic effects.