Reversible Right-to-Left Shunt After Mitral TEER Resolved by Tricuspid TEER.

BACKGROUND: Iatrogenic atrial septal defects are common after transseptal interventions and are usually clinically insignificant; however, under specific hemodynamic conditions, they may result in clinically relevant right-to-left shunting and hypoxemia. CASE SUMMARY: A 67-year-old woman with severe mitral and torrential tricuspid regurgitation underwent a combined transcatheter edge-to-edge repair (TEER) strategy. Shortly after successful mitral TEER, the patient developed acute hypoxemia (oxygen saturation decreased from 96% to 82%) during preparation for tricuspid intervention. Transesophageal echocardiography revealed a 0.7-cm iatrogenic atrial septal defect with predominant right-to-left shunting. Instead of defect closure, tricuspid TEER was performed, resulting in rapid improvement in oxygen saturation (to 95%) and reversal of shunt direction. DISCUSSION: Right-to-left shunting after mitral TEER may be driven by right-sided pressure overload and altered flow dynamics rather than the septal defect itself. CONCLUSIONS: Treating tricuspid regurgitation can restore interatrial pressure balance, reverse shunt direction, and potentially obviate the need for atrial septal defect closure.