Target temperatures of 48 degrees C versus 60 degrees C during slow pathway ablation: A randomized comparison

Slow Pathway Ablation. Introduction: The relationship between temperature a t the electrode-tissue interface and the toss of AV and ventriculoatrial (V A) conduction is not established, and the optimal target temperature for th e slow pathway approach to radiofrequency ablation of AV nodal reentrant ta chycardia (AVNRT) is unknown. Therefore, the purpose of this study was to c ompare target temperatures of 48 degrees C and 60 degrees C during the slow pathway approach to ablation of AVNRT. Methods and Results: The study included 138 patients undergoing ablation fo r AVNRT. Patients undergoing slow pathway ablation using closed-loop temper ature monitoring mere randomly assigned to a target temperature of either 4 8 degrees C or 60 degrees C. The primary success rates were 76% in the pati ents assigned to 48 degrees C and 100% in the patients assigned to 60 degre es C (P < 0.01). The ablation procedure duration (33 +/- 31 min vs 26 +/- 2 8 min; P = 0.2), fluoroscopic time (25 +/- 15 min vs 24 +/- 16 min; P = 0.5 ), and mean number of applications (9.3 +/- 6.5 vs 7.8 +/- 8.1; P = 0.3) we re similar in patients assigned to 48 degrees and 60 degrees C, respectivel y. The mean temperature (46.1 degrees +/- 24.8 degrees C vs 48.7 degrees +/ - 3.2 degrees C; P < 0.01), the temperature associated with junctional ecto py (48.1 degrees +/- 2.0 degrees C vs 53.5 degrees +/- 3.5 degrees C, P < 0 .0001), and the frequency of VA block during junctional ectopy (24.6% vs 37 .2%; P < 0.0001) were less in the patients assigned to 48 degrees C compare d to 60 degrees C. The frequency of transient or permanent AV block was sim ilar in each group (2.8% vs 3.6%; P = 0.2). In the 60 degrees C group, only 12% of applications achieved an electrode temperature of 60 degrees C. Dur ing follow-up of 9.9 +/- 4.2 months, there was one recurrence of AVNRT in t he 48 degrees C group and none in the 60 degrees C group. Conclusions: Compared to 48 degrees C, a target temperature of 60 degrees C during radiofrequency slow pathway ablation is associated with a higher pr imary success rate and a higher incidence of VA block during junctional ect opy induced by the radiofrequency energy. AV block is not more common with the higher target temperature, but only if VA conduction is aggressively mo nitored during applications of radiofrequency energy.