The number of left atrial transcatheter procedures performed via a transseptal (TS) approach has grown exponentially over the last 2 decades.1 Persistent iatrogenic atrial septal defects (iASD) after structural TS interventions are not uncommon especially when larger TS sheaths are used (25%–50% with 22 Fr sheaths).2–5 The optimal management strategy of postprocedural iASD is currently unknown. In the absence of societal recommendations with regards to iASD, the decision to close iASD and the timing of the closure pose a clinical dilemma to the interventionalist caring for these patients. We present 2 cases of iASD after TS transcatheter mitral valve repair/implantation and discuss the challenges in the management of such patients. Two patients were seen in consultation by the Mayo Clinic structural heart service: Ms K: An 81-year-old female admitted with decompensated biventricular heart failure. She had hypertension, atrial fibrillation, systolic heart failure (left ventricular ejection fraction=42%), a permanent pacemaker, and a history of mitral valve replacement with a 33 mm St Jude EPIC prosthesis and tricuspid valve repair. On examination, she was a slender woman (5′0″, 49 kg). Heart rate was 72 bpm, blood pressure was 129/83 mm Hg, and oxygen saturation was 92% on room air. Auscultation revealed a prominent thrill at the apex radiating across her chest and a loud 6/6 apical holosystolic murmur. Jugular veins were distended, and rales were heard at both lung bases. Moderate peripheral pitting edema was also noted. Echocardiography showed a degenerative mitral prosthesis with a flail leaflet and severe mitral regurgitation (MR). It also showed severe right ventricular enlargement with moderately depressed right ventricular function. No thrombus or evidence of endocarditis was present. The heart team evaluation concluded that the patient was at high risk for redo mitral valve replacement (Society of Thoracic Surgeons [STS] score=10%). She then underwent …