Atrial septal defect is the most common congenital disease encountered in adults. The ECG changes in ASD depend on the type of defect, degree of shunt severity, and presence of pulmonary hypertension. The most common type of ASD is the OS subtype, which typically demonstrates rSr′ or rsR′ QRS configuration in right precordial leads.1 This reflects right ventricular volume overload rather than a conduction delay. Prolongation of the PR-segment may be seen in 6% to 19% of patients, which rarely progresses to high-degree atrioventricular block. Right-axis deviation is commonly seen in OS-ASD, whereas left-axis deviation is rare but has been described in hereditary forms of ASD, such as Holt-Oram syndrome and ostium primum ASD.