1-3% of all children undergoing surgery for congenital heart disease develop complete atrioventricular (AV) block. Our study included 49 patients after correction of TOF. 26 patients had right bundle branch block (RBBB) and 23 patients had permanent ventricular pacing for post operative complete heart block. We used different echocardiography modalities to assess cardiac systolic and diastolic function and electromechanical dyssynchrony. We found that global longitudinal strain of left ventricle (LV) was significantly low in paced corrected TOF however it was not significantly affected by increasing duration after surgical repair and systolic function of the right ventricle (RV) was improving by ventricular pacing. In both groups, the LV diastolic function indices were not significantly different but RV diastolic function was more affected in paced patients. Although patients with ventricular pacing had significantly greater interventricular mechanical dyssynchrony and LV lateral wall dyssynchrony but they had better clinical status and lower incidence of heart failure than unpaced corrected TOF. We recommend endocardial single-lead RV pacing for complete AV block in post operative TOF as it is associated with better clinical status , improving RV systolic function, preservation of LV systolic and diastolic function and prevention of prolongation of QRS duration with increasing the duration after surgical repair.