Risk factors for QRS prolongation after repaired tetralogy of Fallot

Repaired tetralogy of Fallot is usually conducive to a normal and unrestricted lifestyle. However, occasionally, late sudden death occurs due to ventricular tachycardia. This is thought to be due to a combination of factors, including both left and right ventricular dilation, which may be associated with valvular incompetence and residual right ventricular outflow tract obstruction. Several studies have shown that QRS duration > 180 ms is a predictor for life-threatening ventricular arrhythmias.

We recalled our tetralogy population (n = 57) to identify risk factors for prolonged QRS duration on the resting ECG. Factors examined included history, demographics, symptoms, surgery, chest X-ray, ECG and echocardiography. Extensive analysis found only a significant positive correlation between QRS duration and degree of residual right ventricular outflow tract obstruction.

Our study suggests that residual right ventricular outflow tract gradients may be a very significant contributor to QRS prolongation. It will be interesting to see if future studies of larger cohorts confirm this finding.