Department of Cardiology, Shaheed Beheshti University of Medical Sciences, Saadat Abad, Modarres General Hospital, Tehran, Iran


Background- A number of publications has shown a relation between increased QT dispersion and death from a cardiac cause. However, there are no published data on the value of QT interval dispersion after open-heart surgery in the pediatric age group.
Methods- Three electrocardiograms (pre-operation, on the day of operation and the second day post-operation) were obtained from 18 children (11 males, 7 females), three to 14years of age. Measurements were carried out from standard 12-lead ECGs recorded at a speed of 25 mmls at rest. The QT and preceding RR intervals of at least one sinus beat (range one to three) were measured in a range of nine to 12 leads, and the mean QT and RR intervals were calculated. The corrected QT interval was calculated by Bazetl's method (QTc = QT/√RR). QT intervals were measured from the onset of the QRS complex to the end of the T wave. Dispersion of the QT and QTc were defined by the difference between the maximum and minimum QT and QTc intervals occurring in any of the 12 leads.
Results-The mean QT dispersion in patients before surgery was 53±22ms, 72±31ms on the day of operation and 65±27 one day after operation, and mean QTc dispersion before surgery was 62±22ms, 95±27ms on the day of operation and 97±41ms on the day after operation. There was a significant increase in mean QT and QTc immediately after surgery (p<0.001). Although it decreased on the first day after surgery, it remained significantly high as compared to before surgery (p<0.02).
Conclusion- QT interval dispersion may increase after open-heart surgery, which may result in death following an arrhythmia. Open-heart surgery may have an independent role in the genesis of QT dispersion prolongation and should be considered as one of the mechanisms of arrhythmia after surgery.