Medical Journal of The Islamic Republic of Iran (MJIRI)

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This study was conducted to assess the incidence of abnormalities of ventricular depolarization (late potentials) in children with sinus rhythm after open heart surgery and their relation to spontaneous ventricular tachycardia. Open heart surgery, particularly operations involving ventriculotomy, may predispose patients to the development of ventricular tachycardia (VT) or ventricular fibrillation (VF). Previous studies on children with right bundle branch block (RBBB) have shown that late potentials may be a risk factor for developing VT or VF following open heart surgery. After corrective surgery for congenital heart defects, scars may create fractionation and delay of the electrical signals in the heart muscle, providing a substrate for arrhythmias and sudden cardiac death. To find normal values of signal averaged EKG (SA-EKG) indices in children and their changes following open heart surgery, we studied 20 normal children and 20 children with congenital heart disease (CHD) following total correction of heart defects without ventriculotomy. All patients were in normal sinus rhythm and did not have RBBB. The mean age was 8.8±2.6 years for the control group and K 1±2.1 years for the operated patients. SA -EKG was performed for the operated group on the day before and on the 2nd and 4th days after operation. Noise level was less than 1 microvolt. The SA-EKG parameter values were as follows: control group: filtered QRS-duration 40Hz (F. QRS-d), 84.2±9.5 ms high frequency low amplitude signals (HFLA) , 18.9±9.5 ms rootmean square 40 (RMS 40), 181.0±89.4 µv patients: F.QRS-d, 97.2±19.3*, 116.4±21.2* and 122.2±220.4before operation, 2nd day post-op and 4th day post-op, respectively HFLA, 205±22.3, 8.9±7.0*, and 15.4±16.4ms,respectively RMS40, 146.4±11O.9,92.1±65.9,and 112.8±60.3, respectively. Values marked with an asterisk are statistically significant. Except for a significant difference between the QRS duration of normal children and pre-op values of operated patients (p<0.05), there was no remarkable difference between the SA-EKG values pre- and postoperatively. This study in which there was no RBBB, contrary to previous studies, shows that SA-EKG indices are not a predictive value for VT or VF postoperatively. Increased thickness of the ventricular myocardium may be a reason for the increased QRS duration before operation.

Keywords: Late potentials, Ventricular arrhythmias, Operated congenital heart defect in children, Signal-averaged electrocardiography.

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