[Influence of age and body surface on the signal averaged high amplification ECG after complete repair of tetralogy of Fallot].

The aim of this study was to assess the influence of age and body surface area on the signal averaged ECG after complete repair of Tetralogy of Fallot. Fifty eight patients operated for Tetralogy of Fallot in whom the postoperative ECG showed right bundle branch block without any significant arrhythmia on Holter monitoring or exercise stress testing underwent signal averaged electrocardiography. A very significant relationship was observed between age and body surface area and the duration of the filtered QRS (r = 0.45, p = 0.0004 and r = 0.49, p = 0.00009 respectively) or the average voltage of the last 40 milliseconds (r = -0.49, p less than 0.03 and r = -0.31, p less than 0.02 respectively). Therefore, signal averaged ECG in patients operated for Tetralogy of Fallot varies with age and morphology. An adjustment of the parameters of the signal averaged ECG with respect to clinical characteristics is necessary before assessing the value of this technique for identifying patients at risk of developing ventricular arrhythmias.