Segmental conduction block in a low-voltage area suppressed macro-reentrant ventricular tachycardia after surgical repair of tetralogy of Fallot.

Macro-reentrant ventricular tachycardia (VT) developed in a 20-year-old man, 17 years after surgical repair of tetralogy of Fallot. Activation mapping of the VT revealed its counterclockwise propagation around the right ventricle, and through a critical pathway between a transannular patch and the tricuspid annulus. This critical pathway was 6 cm long and contained myocardium with a normal amplitude, while the area of low voltage was limited adjacent to the transannular patch. A linear lesion was created by radiofrequency energy delivered only to the low voltage area. After ablation, the activation wavefront through the low voltage area was blocked, and VT became non-inducible.