TEMPERATURE-CONTROLLED RADIOFREQUENCY CATHETER ABLATION OF MANIFEST ACCESSORY PATHWAYS

Objectives The primary objectives of this study were to assess the fea sibility of temperature-controlled radiofrequency catheter ablation of left and right sided manifest accessory pathways in patients with Wol ff-Parkinson-White syndrome and to gain more insights into biophysical aspects of temperature-controlled catheter ablation in humans. Backgr ound The electrode-tissue interface temperature and other biophysical parameters are among important variables determining the efficacy and safety of radiofrequency ablation of accessory pathways. Experimental studies have shown that radiofrequency-induced tissue necrosis can be accurately predicted by monitoring of catheter tip temperature. Method s 38 consecutive patients (14 f, 24 m; aged 42 +/- 12 years) with ante rograde conducting accessory pathways (left sided: n = 22; right sided : n = 16) underwent temperature-controlled radiofrequency ablation (HA T 200S, Dr Osypka, Germany). The electrode temperature was monitored v ia a thermistor embedded into a 4 mm catheter tip. Power output was ad justed automatically during energy delivery in a closed loop system (p reselected temp.: 70.1 +/- 5.8 degrees C).Results Accessory pathway co nduction was successfully abolished in all patients after the delivery of 2.3 +/- 2.1 radiofrequency pulses (range: 1-9, median: 2). Interru ption of the accessory pathway as evidenced by loss of preexcitation o ccurred after 5.9 +/- 5.4 s. At the time of the interruption of the ac cessory pathway the catheter tip temperature measured 54.2 +/- 11.2 de grees C in patients with left and 449 +/- 5.0 degrees C in patients wi th right sided accessory pathways, respectively (P<0.008). Higher temp erature levels during left sided applications did not shorten the time it took for the effect to appear (left sided accessory pathway: 7.5 /- 6.3 s, right sided accessory pathway: 3.7 +/- 2.9 s; ns). The cathe ter tip temperature was significantly higher during left compared to r ight sided applications after 5 (52.1 +/- 3.1 degrees C vs 47.2 +/- 4. 3 degrees C) and 10 s (61.5 +/- 6.2 degrees C vs 52.7 +/- 4.2 degrees C) following initiation of the impulse (P<0.005). Power output and del ivered energy did not differ significantly at the time of accessory pa thway abolition. Peak values of delivered power (45.1 +/- 10.9 W vs 41 .3 +/- 10.6 W; P < 0.05) and total delivered energy (2452 +/- 1335J vs 1392 +/- 762 J; P < 0.02) were significantly higher in the group of r ight sided pathways compared to left sided applications. The peak temp erature measured 77.1 +/- 13 degrees C during effective and 69.9 +/- 1 4 degrees C during ineffective energy applications (P < 0.05). The tim e it took for the effect to appear was significantly longer in transie ntly effective pulses (10.4 +/- 7.2s) compared to permanently effectiv e applications (5.9 +/- 5.4 s; P < 0.02). Despite temperature control, an abrupt rise in impedance was observed in 10 of 89 (11%) energy app lications. No procedure-related complications occurred. Conclusions Te mperature-controlled radiofrequency ablation of manifest accessory pat hways is highly effective and safe. The temperature response is faster and significantly higher in left-sided energy applications compared t o right-sided pulses. Peak temperature levels measured at the electrod e tip are significantly higher during effective than ineffective pulse s. Sudden rises in impedance are not completely prevented during tempe rature-controlled radiofrequency ablation of accessory pathway, althou gh no procedure-related complications were noted in this patient cohor t.