Tachycardia caused by an accessory nodoventricular tract: a clinico-pathologic correlation.

Paroxysmal tachycardia with widened QRS complexes was recorded in an eleven-year old boy who had suffered from brain damage, which had resulted from an episode of ventricular fibrillation. Atrial stimulation produced an increased AV conduction, sudden disappearance of the His bundle deflection and a complete left bundle branch block pattern. Tachycardias of this morphology were initiated by early atrial and ventricular premature beats. The findings suggested the presence of a macro re-entry circuit, utilizing a slow AV node- nodoventricular bypass tract as the anterograde limb and the His-Purkinje system--fast AV node as the retrograde limb. This supposition found further support by serial sectioning of the AV junctional area of the heart, which revealed a nodoventricular tract, which originated from the posterior extension of the compact part of the atrioventricular node and inserted into the crest of the ventricular septum.