Abstract: AIM: To evaluate the effects of an acute atrial stretch on atrial pressure and the effective refractory period of atrium (ERPA) in humans. METHODS: Thirty-two patients without structural heart diseases who were treated with catheter radiofrequency ablation due to paroxysmal supraventricular tachycardia were enrolled for this study. Atrial pressure and ERPA at high right atrium (HRA) and distal coronary sinus (CSd) were evaluated during sinus rhythm, rapid atrial pacing (AP) at high right atrium (HRA), rapid ventricular pacing (RVP) at right ventricular apex (RVA), simultaneous AV, pacing at HRA+RVA (SAVPHRA+RVA) and simultaneous AV pacing at CSd+RVA (SAVPCSd+RVA) at a cycle length of 400 msec. RESULTS: Compared with those during sinus rhythm, no significant changes were observed in the mean right atrial pressure during AP ［(9±4) vs. (7±3) cmH2O, 1 cmH2O=0.098 kPa］ but the mean right atrial pressure increased significantly during RVP, SAVPHRA+RVA and SAVPCSd+RVA ［(14±4), (13±4), (15±4) cmH2O, P<0.01］ with no significant difference among the three. The ERPA shortened significantly using different pacing modes compared with that during sinus rhythm. ERPHRA further shortened during SAVPHRA+RVA ［(24±14) vs. (15±11)/(13±9) msec, P<0.05］ and ERPCSd further shortened during SAVPCSd+RVA ［(23±15) vs. (15±12)/(14±11) msec, P<0.05］ compared with those during AP and RVP. CONCLUSION: Both VP and SAVP increase atrial pressure. Simple RVP is a good alternative to SAVP in the study of atrial mechanoelectrical feedback (MEF). Different pacing modes all lead to the shortening of ERPA at HRA and CSd.