TEMPERATURE-CONTROLLED SLOW PATHWAY ABLATION FOR TREATMENT OF ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA USING A COMBINED ANATOMICAL AND ELECTROGRAM GUIDED STRATEGY

Aims Anatomical and electrogram-guided techniques have been used separ ately for slow pathway ablation in atrioventricular nodal reentrant ta chycardia. The aims of the present study were to analyse electrogram c haracteristics of target sites and biophysical parameters using a comb ined anatomical and electrogram-guided technique for temperature-contr olled radiofrequency catheter ablation of the slow pathway. Methods an d results Using a temperature-controlled (pre-selected 60 degrees C) c atheter system, 53 patients with atrioventricular nodal reentrant tach ycardia underwent slow pathway radiofrequency ablation. Mapping was st arted posteroseptally near the coronary sinus ostium and continued tow ards the midseptal area if needed. The longest and latest atrial elect rograms with an atrioventricular ratio of less than or equal to 0 . 5 were targeted. After a median of two pulses (mean 2 . 36+/-1 . 33), at rioventricular nodal reentrant tachycardia was rendered non-inducible in all patients without complications. Successful sites had longer atr ial electrograms (78 . 8+/-9 . 8 vs 67 . 6+/-13 . 3 ms, P<0 . 003) and larger ventricular electrogram amplitudes (92 . 4+/-51 . 2 vs 63 . 1/-28 . 8 mV, P<0 . 05) than the failed sites, but had a similar atriov entricular ratio, P-A interval and atrial electrogram amplitude. Overa ll, an atrial electrogram duration of greater than or equal to 70 ms w as associated with effective radiofrequency delivery, with 86% sensiti vity and 62% specificity. The achieved temperature maximum was 62 . 3/-9 . 8 degrees C at successful and 58 . 8+/-9 . 0 . C at unsuccessful sites (ns). There was no significant difference between successful an d unsuccessful applications with respect to power output, impedance an d total delivery energy. During a pre-discharge study, three patients with inducible atrioventricular nodal reentrant tachycardia underwent a repeat ablation. During 12 . 3+/-2 . 5 (6-15) months of follow-up, t hree others had a clinical recurrence of atrioventricular nodal reentr ant tachycardia. Conclusions The combined approach for slow pathway ab lation is highly effective, requiring a low number of radiofrequency p ulses. Long atrial activation time seems to be the most powerful predi ctor of success. Similar catheter tip temperature levels during succes sful and unsuccessful radiofrequency applications indicate that subopt imal selection of target sites rather than ineffective heating due to poor catheter tissue coupling is responsible for unsuccessful energy d elivery.