Transcatheter closure of secundum atrial septal defects is well-established, but data on very large defects requiring 40–50 mm occluders remain limited. This multicenter retrospective study evaluated the safety and efficacy of percutaneous closure using large atrial septal occluders.

Patients undergoing atrial septal defect device closure with 40–50 mm occluders from June 2015 to May 2025 at two tertiary centres were analysed. Patients were grouped by device size: Group A (40–42 mm; n = 34) and Group B (44–50 mm; n = 28).

The cohort (n = 62) had a mean age of 42.07 years with female predominance (70.96%). Mean atrial septal defect size was 33.03 mm (thick-to-thick: 38.71 mm), with mean pulmonary artery pressure of 22.33 mmHg and left ventricular end-diastolic pressure of 12.59 mmHg. Aneurysmal septum with thin or deficient posteroinferior rim was common (77.4% and 19.4%, respectively). Procedural success was 93.5%. Device instability or residual flow led to surgical closure in three cases; one had intraprocedural embolisation. Procedural assistance (balloon/device, etc.) was needed in 93.5%. Fenestrated devices were used in four (6.5%) patients—due to severe pulmonary stenosis, diastolic dysfunction, or pulmonary hypertension. “Cobra” configuration and device bulkiness were noted in 9.7% and 6.5%, respectively. Arrhythmias occurred in 25.8%, mostly transient. One patient developed device-related endocarditis, and one late, unrelated death occurred due to intracranial haemorrhage. At a mean follow-up of 29.29 months, outcomes were satisfactory.

Transcatheter closure of large atrial septal defects with 40–50 mm devices is safe and effective with proper anatomical assessment, procedural planning, and vigilant follow-up in selected patients.