Key Points• Most (87.6%) of residual atrial L-R shunts after Gore Cardioform septal occluder implant disappear by 12 months.• Residual leaks at implantation were more common in larger defects with smaller retro-aortic rims, and multiple fenestrations.• While most residual defects close in 12 months, we unfortunately do not yet have a clear idea why or which of the 13% do not close.The current report by Gordon et al. 1 describes the mid-term multi center results of secundum atrial septal defect closure with the Gore Cardioform septal occluder. The manuscript is very positive in its presentation to document the closure of residual leaks in patients included in the Gore pivotal and continued access study for the Gore Cardioform septal occluder. Of the 370 total ASD closure patients included, 17.56% had a residual leak define by echocardiography at the time of implantation. A total of 87.6% of these disappeared by 12 months follow-up. Thus, in this group of 370 patients, the total closure rate at 12 months was 97.8%. They did note that the incidence of residual leaks at implantation were more significant in patients with larger defects, smaller retro-aortic rims, and with multiple fenestrations. These results are similar to the previous reviews for ASD device closure by a Prieto, 2 Grohmann, 3 and Jalal 4 which noted complete closure by ASO (Amplatz, St. Jude Medical, Inc., Saint Paul, MN) at 97.5%; Helex (W. L. Gore, Flagstaff, AZ) at 96.2%, and GSO (Europe) at 95.4%. In general, the mid-term results have been reported with standard transthoracic echocardiographic imaging. The authors discuss the greater use of transesophageal echocardiography in patients with residual leaks observed in this study but unfortunately there is no clear discussion of what type of echocardiographic study was used to clearly define the late results at 12 months, although, again, it would seem to have been transthoracic echocardiography (TTE).