[Ablation or modification of slow pathway in AV nodal reentrant tachycardia and electrophysiological changes].

INTRODUCTION: The endpoint of successful treatment of slow pathway ablation is elimination of AV nodal reentrant tachycardia (AVNRT). However, the mechanism of elimination is not well understood and is controversial if complete elimination or persistent dual AV nodal physiology is associated with a higher success, recurrence and/or complications rate. OBJECTIVES: The purpose was to examine the results after slow pathway ablation in AVNRT and changes in AV nodal conduction in patients with and without loss of dual AV nodal physiology. METHODS AND RESULTS: The study included 106 patients (age 47 +/- 17 years). In 64% with elimination of inducible AVNRT still had dual AV nodal physiology (group I) and absent in 36%, group II). Both, anterograde fast pathway and slow pathway effective refractory period (ERP) showed a tendency to decrease but without statistical significance: 340 +/- 39 ms to 329 +/- 45 ms, 290 +/- 16 to 279 +/- 43 ms respectively, p = NS. In group II, anterograde fast pathway ERP decreased significantly 328 +/- 83 ms to 282 +/- 75 ms, p < 0.001. Anterograde Wenckebach cycle length increased in both groups: 360 +/- 65 to 375 +/- 61 ms, p < 0.05 group I, and 351 +/- 20 to 381 +/- 14 ms, p < 0.001 group II. CONCLUSIONS: Ablation procedures of the AV node slow pathways that eliminate AVNRT modify the AV node electrophysiologic conduction properties. These modifications are more important in patients with complete elimination of dual AV nodal physiology; nonetheless, in a high rate of patients the elimination is incomplete but without reinduction of clinical tachycardia. It has been suggested that elimination of the AVNRT despite the persistence of dual AV nodal physiology is due to the presence of more than one AV node slow pathway with different electrophysiological properties.