Abstract: AIM The safety and efficacy of atrial septal defect(ASD) occluder(ASDO) made in China for transcatheter closure of ASD have investigated prospectively. We report the phenomenon of transient STsegmentelevation(TSTE) during transcatheter closure of ASD with ASDO made in China in this singlecentre study. METHODS A total of 35 consecutive patients in whom a septal defect occluder (Huayishengjie Inc., Beijing, China) was used to close a clinically significant ASD were included in our study.All procedures performed under basic or local anaesthesia with transthoracic echocardiographic guidance. Interatrial communications were assessed by transthoracic echocardiography(TTE) with reference to size, position in the interatrial septum, proximity to surrounding structures, and adequacy of septal rim. Device selection was based on and matched to the stretched diameter of the communication.Success defined as deployment of device in a stable position to occlude the interatrial communication without inducing functional abnormality or anatomical obstruction. Occlusion status determined by TTE during procedure and the follow up of the study at 3, 6, and 12 months. RESULTS In 2 of the 35 patients from our centre, a transient STsegmentelevation greater than 0.2 mV was recorded and angina pectoris occurred during the deployment of the device.The ECG changes and the symptoms started abruptly and lasted for (4.2±2.2) min. All the ECG changes occurred in lead II, III, and aVF.The association between the heart rate, blood pressure and the ECG changes was described. The bradycardia and hypotension were seen during STsegmentelevation in these two patients. The administration of intravenous nitroglycerin was performed, the symptoms and ECG changes didn’t recovered immediately. When the devices were retrieved by withdrawing it into the sheath by traction on the delivery wire, the symptoms were gradually eliminated and ECG changes recuperated immediately. No haemodynamic derangement or transient ECG changes occurred after the larger diameter devices were exchanged. During the followup of the study at 3, 6, and 12 months these two patients showed no further signs of myocardial ischemia and were free of episodes of angina pectoris. CONCLUSION The phenomenon of STsegment elevation during transcatheter closure of ASD may be caused by the mechanical effects of the larger diameter ASDO.