[Importance of endocardial ECG for successful AV-node modulation in patients with AV-node reentry tachycardia]

In 49 patients undergoing slow pathway (SP) ablation for AV nodal reentrant 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 analyzed with respect to the following parameters: 1) ratio of local atrial (A) to local ventricular (V) electrogram amplitude (A/V-ratio), 2) presence 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, A/V-ratio > or = 0.25; group 2: FAA/SPP or A/V-ratio < 0.25; group 3: FAA/SPP and A/V-ratio < 0.25.

In all patients SP ablation was successful after 4.6 +/- 4.4 applications. Successful ablation sites had a significantly smaller A/V-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 different (72.3 +/- 2.14 vs. 71 +/- 1.35 ms, p = n. s.).

1) In SP ablation of AVNRT the local A/V-ratio is significantly smaller in successful compared to non-successful ablation sites. 2) Local A electrogram 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 with ablation success.