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

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.

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.

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.

Treating tricuspid regurgitation can restore interatrial pressure balance, reverse shunt direction, and potentially obviate the need for atrial septal defect closure.