Abstract: Objective:To investigate the effect of crochetage on R wave on identification of secundum atrial septal defect with right ventricular enlargement whether accompanied with pulmonary arterial hypertension at the same time.Methods:According to 3 inferior leads appeared with crochetage on R wave and the traditional electrocardiogram diagnostic standard for right ventricular enlargement,58 atrial septal defect cases with right ventricular enlargement also with pulmonary arterial hypertension(group A) and 74 atrial septal defect cases with right ventricular enlargement without pulmonary arterial hypertension(group B) were compared.Results:The emergence rate of 3 inferior leads appeared with crochetage on R wave in group A were higher than in group B(P＜0.01);but about the traditional electrocardiogram diagnostic standard for right ventricular enlargement,there were no statistical difference between the two groups(P＞0.05).Conclusions:Crochetage on R wave in inferior limb leads can not only be used as an independent electrocardiogram signs for diagnosing atrial septal defect,but also be used as a good index of identifing pediatric atrial septal defect with right ventricular enlargement also with pulmonary arterial hypertension at the same time.