[Three AV-nodal pathways in a patient with atypical AV-nodal reentry tachycardia].

In a female patient with paroxysmal AV nodal reentrant tachycardias the electrophysiological study revealed three AV nodal pathways. During atrial extrastimulation a sudden AH interval prolongation of more than 50 ms ("break" phenomenon) was observed twice at one basic cycle length. During ventricular extrastimulation a sudden prolongation of the AH interval of the anterograde AV nodal conduction of the induced echo beats was recorded. Three AV nodal pathways were thus present. The atypical form of AV nodal reentrant tachycardia was induced, showing a varying cycle length (290-340 ms). After radiofrequency catheter ablation of the fast conducting beta-pathway, another tachycardia was initiated, now showing a constant cycle length, using the two remaining, more slowly conducting alpha-pathways. One of these was eliminated in another ablation procedure.