Background Incomplete right bundle branch block (ICRBBB) is commonly associated with atrial septal defect (ASD),but lacks sufficient diagnostic test characteristics.An abnormal T wave is also often observed in ASD,with horizontal or inverted displacement of the proximal T wave limb in the right precordial leads,termed "defective T wave" (DTW).Methods We examined the diagnostic test characteristics of combining ICRBBB with DTVV as a new index to diagnose ASD.A total of 132 consecutive patients with ASD and 132 cases of age/gender-matched controls without ASD were enrolled.Results Sensitivities of DTW,ICRBBB,and both were 87.1％-87.9％.Specificities were 97.0％,96.2％,and 100％,respectively.Positive predictive values were 1.3％,1.1％,and 100.0％ respectively,while negative predictive values were 99.9％ for each.Conclusion Combining ICRBBB with DTW in electrocardiogram (ECG) as a new index significantly increased the specificity and positive predictive values while maintaining a high sensitivity in diagnosing ASD.