CORRELATION OF TEMPERATURE AND PATHOPHYSIOLOGICAL EFFECT DURING RADIOFREQUENCY CATHETER ABLATION OF THE AV JUNCTION

Background Accelerated junctional rhythms have been observed before th e development of AV nodal block during radiofrequency (RF) catheter ab lation of the AV junction. However, the time course and temperatures r equired to induce an accelerated junctional rhythm and AV nodal block during this procedure have not yet been characterized. Methods and Res ults Nineteen patients underwent RF ablation of the AV junction with a thermistor ablation catheter. RF energy was initially delivered at 10 W for 9 seconds and then increased by 5-W increments for 9 seconds at each power level up to a maximum power of 50 W. If a junctional rhyth m was observed during the power titration, a 30- to 60-second RF appli cation was then delivered at the same power level. The power was then further increased to a maximum of 50 W if AV nodal block was not obser ved after 20 seconds of RF delivery. The procedure was successful in a ll 19 patients. A median of one RF application (range, one to eight ap plications) was required to produce permanent AV nodal block. An accel erated junctional rhythm was observed during 89% of successful attempt s versus 70% of unsuccessful deliveries (P=NS). The median time to ons et of the junctional rhythm was significantly shorter during successfu l compared with unsuccessful applications (1.8 versus 7.7 seconds, res pectively; P<.001). Similarly, the mean time to appearance of AV nodal block was significantly shorter during successful compared with unsuc cessful attempts (19.6+/-9.4 versus 36.8+/-19.0 seconds, respectively; P<.01). The catheter tip temperatures associated with the development of an accelerated junctional rhythm were significantly lower than tho se associated with the appearance of AV nodal block (51+/-4 degrees C versus 58+/-6 degrees C, respectively; P<.001). Mean temperatures in t he range of 60+/-7 degrees C were required to produce permanent AV nod al block. Conclusions The development of an accelerated junctional rhy thm within 5 seconds and the appearance of AV nodal block within 30 se conds of RF onset were both highly characteristic of successful target sites during RF ablation of the AV junction. The accelerated junction al rhythm and AV nodal block were both highly temperature dependent. T he temperatures associated with the onset of AV nodal block were signi ficantly higher than the temperatures resulting in an accelerated junc tional rhythm.