Objective: To determine the correlation between various electrocardiographic characteristics and presence of hemodynamically significant secundum ASD.

Method: Retrospective study looking at pre-closure electrocardiograms of 84 consecutive echocardiographically proven secundum ASD patients who attended our clinic from 2005 till 2008.ECG features of Right Bundle Branch Block(RBBB), right axis deviation(RAD) and prolongation of PR interval were assessed. Pre-closure echocardiograms were evaluated for ASD size, right ventricular and right atrial dilatation.

Results: Of all the 84 consecutive echocardiographically proven secundum ASD patients (mean age of 40.2±15.9 years, 65% female), electrocardiographic features of incomplete RBBB, complete RBBB and RAD were observed in 69 %,11% and 58% respectively(Table 1).RBBB appeared to be the only statistically significant electrocardiographic characteristic in predicting hemodynamically significant secundum ASD (P value <0.0001), with sensitivity, specificity, positive predictive value and negative predictive value of 90%, 63%,91% and 59% respectively. Both RAD and PR interval prolongation showed high positive predictive value, but poor sensitivity and specificity in predicting hemodynamically significant ASD (Table 2,3).

Conclusions: The presence of RBBB pattern in our study population predicted 91% of all the moderate to large secundum ASD defects with RV dilatation, who required closure of ASD. However, the absence of RBBB could not be utilized to exclude the presence of significant ASD and RV dilatation