It is well known that adults with previously operated tetralogy of Fallot can develop ventricular tachyarrhythmias and die suddenly. They are prone for ventricular tachycardia as well as atrial tachyarrhythmias like atrial flutter and fibrillation. Syncope may be a fore runner of sudden death in some individuals with operated tetralogy of Fallot and calls for evaluation. An annual incidence of 0.4 percent sudden death during the first twenty five years after surgery has been reported. Both the surgical scar as well as the dilatation of right ventricle and right atrium due to the pulmonary and tricuspid regurgitation are thought to have roles in arrhythmogenesis. Highest risk is in those with marked cardiomegaly (cardiothoracic ratio more than 60 percent), severe pulmonary and or tricuspid regurgitation, QRS duration on the electrocardiogram of more than 180 milliseconds, and a QT interval dispersion of more than 60 milliseconds
[Gatzoulis MA, Till JA, Somerville J, Redington AN. Mechanoelectrical interaction in tetralogy of Fallot: QRS prolongation relates to right ventricular size and predicts malignant ventricular arrhythmias and sudden death. Circulation 1995;92:231-7 and Gatzoulis MA, Till JA, Redington AN. Depolarization-repolarization inhomogeneity after repair of tetralogy of Fallot: the substrate for malignant ventricular tachycardia? Circulation 1997;95:401-4].
Surgical correction of pulmonary regurgitation with a valvular prosthesis and tricuspid regurgitation by annuloplasty may decrease the chance of atrial and ventricular arrhythmias. This is more likely if surgical repair is also accompanied by mapping and ablation of the reentry circuit of arrhythmia [Therrien J, Siu SC, Harris L, Dore A, Niwa K, Janousek J, et al. Impact of pulmonary valve. replacement on arrhythmia propensity late after repair of tetralogy of Fallot. Circulation 2001;103: 2489-94]