BACKGROUND: Electrocardiographic (ECG) Selvester QRS score criteria with false indication of anteroseptal scarring consistent with myocardial infarction have been found in patients with ostium secundum atrial septal defect (OS-ASD). The objective of this study was to evaluate ECGs pre and post percutaneous transcatheter OS-ASD closure to test the hypothesis that the falsely positive criteria for anteroseptal scar decline 1 day post procedure. METHODS: Patients (n = 34, mean age 48 ± 17 years, 79% female) that underwent OS-ASD closure and had undergone pre procedure cardiac magnetic resonance imaging showing no left ventricular (LV) scarring were included in this study. ECGs pre and 1 day post procedure were assessed according to the QRS Selvester scoring system and compared. RESULTS: Mean Selvester score in anteroseptal regions pre procedure was 6.6 (0.0-6.8) % LV scar and decreased to 4.3 (0.0-6.0) % LV scar one day after the procedure (p = 0.01). Mean Selvester score in lateral regions pre procedure was 3.7 (0.0-3.0) %LV scar and decreased to 2.8 (0.0-0.0) % LV scar one day post procedure (p = 0.25). DISCUSSION: OS-ASD patients with falsely positive anteroseptal scar criteria by the Selvester QRS score pre procedure have a significant decrease in anteroseptal Selvester score 1 day post procedure. The falsely positive anteroseptal scar criteria did not completely resolve 1 day post procedure. Further studies are needed to investigate the relationship between ECG criteria for anteroseptal scar and right ventricular volume overload in late follow up.