The efficacy of pulmonary vein antral isolation for patients with prolonged sinus pauses (PSP) on termination of atrial fibrillation has been reported. We studied the right atrial (RA) electrophysiologic and electroanatomic characteristics in such patients. Forty patients underwent electroanatomic mapping of the RA: 13 had PSP (group A), 13 had no PSP (group B), and 14 had paroxysmal supraventricular tachycardia (control group C). Group A had longer P-wave durations in lead II than did groups B and C (115.5 +/- 15.4 vs 99.5 +/- 10.9 vs 96.5 +/- 10.4 ms; P=0.001), and RA activation times (106.8 +/- 13.8 vs 99 +/- 8.7 vs 94.5 +/- 9.1 s; P=0.02). Group A's PP intervals were longer during adenosine triphosphate testing before ablation (4.6 +/- 2.3 vs 1.7 +/- 0.6 vs 1.5 +/- 1 s; P < 0.001) and after ablation (4.7 +/- 2.5 vs 2.2 +/- 1.4 vs 1.6 +/- 0.8 s; P < 0.001), and group A had more complex electrograms (11.4% +/- 5.4% vs 9.3% +/- 1.6% vs 5.8% +/- 1.6%; P < 0.001). Compared with group C, group A had significantly longer corrected sinus node recovery times at a 400-ms pacing cycle length after ablation, larger RA volumes (100.1 +/- 23.1 vs 83 +/- 22.1 mL; P=0.04), and lower conduction velocities in the high posterior (0.87 +/- 0.13 vs 1.02 +/- 0.21 mm/ms; P=0.02) and high lateral RA (0.89 +/- 0.2 vs 1.1 +/- 0.35 mm/ms; P=0.04). We found that patients with PSP upon termination of atrial fibrillation have RA electrophysiologic and electroanatomic abnormalities that warrant post-ablation monitoring.