摘要Background Percutaneous left atrial appendage occlusion (LAAO) requires puncture of the interatrial septum. The immediate hemodynamic effects of iatrogenic atrial septal defects (iASD) after LAAO have not been examined so far. We aimed at evaluat-ing these effects through invasive measurements of pressure and oxygen saturation. Moreover, we assessed the incidence of per-sistent iASD at three months. METHODS Forty-eight patients scheduled for percutaneous LAAO were prospectively included in the study. Pressure and oxygen saturation were measured (1) in the right atrium (RA) before transseptal puncture, (2) in the left atrium (LA) through the transseptal sheath after transseptal puncture, (3) in the LA after removal of introducer sheath, and (4) in the RA after removal of introducer sheath. Transesophageal echocardiography was performed at three months to detect iASD. RESULTS Pressure in the RA increased significantly after removing the introducer sheath (P = 0.034), whereas no difference was found in oxygen saturation in the RA (P = 0.623). Pressure measurement in the LA showed no significant difference after re-moving the introducer sheath (P = 0.718). Oxygen saturation in the LA also showed no significant difference (P = 0.129). Follow-up transesophageal echocardiogram at 3 months revealed a persistent iASD in 4 patients (8.5 ％). CONCLUSIONS Our study suggests that iASD after percutaneous LAAO does not result in significant shunts directly after the procedure, although a significant increase of mean right atrial pressure can be observed. Persistent iASDs after percutaneous LAAO seem to be relatively rare at three months.