AbstractObjectivesThe aim of this study is to evaluate our clinical experience using an Amplatzer septal occluder for catheter closure of a secundum atrial septal defect under transthoracic echocardiography guidance without general anaesthesia.MethodsPatients eligible for transcatheter atrial septal defect closure were selected using transthoracic echocardiography. The largest defect diameter measured in different views was selected as the reference diameter. All procedures were performed under conscious sedation with fluoroscopic and transthoracic echocardiographic guidance.ResultsBetween November, 2006 and December, 2009 a secundum-type atrial septal defect was closed with the Amplatzer septal occluder in 40 patients with transthoracic echocardiographic guidance. The mean age and weight were 7.9 years and 26.9 kilograms, respectively. The mean atrial septal defect diameter was 11.4 millimetres, total septal diameter was 38.5 millimetres, and the mean device diameter and the difference between device and atrial septal defect diameter were 12.6 and 1.2 millimetres, respectively. There were no major complications. The mean follow-up time was 14.8 months.ConclusionIn selected cases, in which the defects are small and the rims are adequate and transthoracic echocardiography provides high image quality, transthoracic echocardiography can be substituted with transoesophageal echocardiography. The ratio of defect size to total septal diameter can be used as a guide for patient selection; those that have a value of 0.33 or greater can be considered eligible for closure with transthoracic echocardiography. However, transthoracic echocardiography should not be used when there are large or multiple defects, or the rims are thin and soft and the image resolution is inadequate.