Acute deoxygenation during M-TEER: a note of caution

Aims Right-to-left (R-L) shunting through an iatrogenic atrial septal defect (iASD) after mitral transcatheter edge-to-edge repair (M-TEER) is a rare but potentially life-threatening complication. We aimed to identify factors associated with clinically relevant R-L shunting requiring emergency iASD closure. Methods and results We retrospectively analysed 444 consecutive patients undergoing successful M-TEER between 2017 and 2026. Clinical, echocardiographic, and invasive haemodynamic parameters were compared between patients requiring emergency iASD closure and the remaining cohort. Six patients (1.3%) required emergency iASD closure due to R-L shunting and acute deoxygenation. All presented with severe tricuspid regurgitation, RV dilatation, and impaired RV function. Following M-TEER, right atrial pressure exceeded left atrial pressure in five patients. Compared with controls, affected patients demonstrated reduced tricuspid annular plane systolic excursion (15 ± 2 vs. 19 ± 4 mm), fractional area change (FAC) (27 ± 5% vs. 43 ± 6%), and RV free wall strain (−13 ± 2% vs. −22 ± 5%). Echocardiography underestimated invasively measured systolic pulmonary artery pressure (25.8 vs. 40.3 mmHg; P = 0.035). Oxygen saturation decreased by 3-8%, with one patient developing cardiogenic shock. Conclusion Severe tricuspid regurgitation, RV dysfunction, and elevated right atrial pressure may identify patients at risk for clinically relevant R-L shunting after M-TEER. Comprehensive RV assessment, including FAC and strain, combined with invasive hemodynamic evaluation, may improve risk stratification and facilitate timely iASD closure.