IMPORTANCE OF ENDOCARDIAL ELECTROGRAMS FO R THE SUCCESS OF RADIOFREQUENCY MODIFICATION OF THE ATRIOVENTRICULAR NODE IN PATIENTS WITH ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA

In 49 patients undergoing slow pathway (SP) ablation for AV nodal reen trant tachycardia (AVNRT) the local electrograms of successful and non -successful radiofrequency current applications taken from the mapping /ablation catheter in the posteroseptal space were retrospectively ana lyzed with respect to the following parameters: 1) ratio oflocal atria l (A) to local ventricular (V) electrogram amplitude (AN-ratio), 2) pr esence of fractionated atrial activity (FAA) or SP potential (SPP), 3) duration of local A electrogram. Ablation sites were classified in 3 groups: group I: no FAA/SPP, AN-ratio greater than or equal to 0.25; g roup 2: FAA/SPP or AN-ratio < 0.25; group 3: FAA/SPP and A/V-ratio < 0 .25. Results: In all patients SP ablation was successful after 4.6 +/- 4.4 applications. Successful ablation sites had a significantly small er AN-ratio than non-successful ones (0.2 +/- 0.04 vs. 0.44 +/- 0.06, p = 0.023). The local A electrogram duration was not significantly dif ferent (72.3 +/- 2.14 vs. 71 +/- 1.35 ms, p = n. s.). Conclusions: 1) In SP ablation of AVNRT the local AN-ratio is significantly smaller in successful compared to non-successful ablation sites. 2) Local A elec trogram duration does not correlate with ablation success. 3) A local A/V-ratio of < 0.25 and the presence of a SPP or FAA are correlated wi th ablation success.