Background:Selecting the device size using a sizing balloon could oversize the ostium secundum atrial septal defect (OSASD) with floppy margins and at times may lead to complications. Identifying the firm margins using trans-esophageal echocardiography (TEE) and selecting appropriate-sized device optimizes ASD device closure. This retrospective study was undertaken to document the safety and feasibility of device closure without balloon sizing the defect.Methods:Sixty-one consecutive patients who underwent trans-catheter closure of OSASD guided by balloon sizing of the defect and intra procedural fluoroscopy (group I) and 67 consecutive patients in whom TEE was used for defect sizing and as intraprocedural imaging during device deployment (group II) were compared. The procedural success rate, device characteristics, and complications were compared between the two groups.Results:The procedure was successful in 79.7 % patients. The success rate in group II (60 of 67, 89.6%) was significantly higher than in group I (41 of 61, 67.2 %) (P = 0.002). Mean upsizing of ASD device was significantly lower in group II (P < 0.001). TEE also provided better success rate with smaller device in subjects with large ASD (>25 mm) and in those who were younger than 14 years of age. There were four cases of device embolization (two in each group); of which one died in group II despite successful surgical retrieval.Conclusion:Balloon sizing may not be essential for successful ASD device closure. TEE-guided sizing of ASD and device deployment provides better success rate with relatively smaller sized device.