Temperature-controlled radiofrequency catheter ablation of manifest accessory pathways

Objectives The primary objectives of this study were to assess the feasibility of temperature-controlled radiofrequency catheter ablation of left and right sided manifest accessory pathways in patients with Wolff-Parkinson-White syndrome and to gain more insights into biophysical aspects of temperature-controlled catheter ablation in humans. Background 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. Methods 38 consecutive patients (14 f, 24 m; aged 42 ± 12 years) with anterograde conducting accessory pathways (left sided: n=22; right sided: n=l6) underwent temperature-controlled radiofrequency ablation (HAT 200S, Dr Osypka, Germany). The electrode temperature was monitored via a thermistor embedded into a 4 mm catheter tip. Power output was adjusted automatically during energy delivery in a closed loop system (preselected temp.: 70·1 ± 5·8°C). Results Accessory pathway conduction was successfully abolished in all patients after the delivery of 2·3 ± 2·1 radiofrequency pulses (range: 1–9, median: 2). Interruption of the accessory pathway as evidenced by loss of preexcita tion occurred after 5·9 ± 5·4 s. At the time of the interruption of the accessory pathway the catheter tip temperature measured 54·2 ± 11· 2 ° C in patients with left and 44·9 ± 5·0° C in patients with right sided accessory pathways, respectively ( P <0·008). Higher temperature 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 catheter tip temperature was significantly higher during left compared to right sided applications after 5 (52· 1 ± 3· 1 °C vs 47· 2 ± 4· 3 ° C) and 10s (61· 5 ± 6· 2 ° C vs 52· 7 ± 4· 2° C) following initiation of the impulse ( P <0· 005). Power output and delivered energy did not differ significantly at the time of accessory pathway abolition. Peak values of delivered power (45· 1 ± 10· 9 W vs 41· 3 ± 10· 6W; P < 0· 05) and total delivered energy (2452 ± 1335 J vs 1392 ± 762 J; P <0· 02) were significantly higher in the group of right sided pathways compared to left sided applications. The peak temperature measured 77· 1 ± 13 °C during effec tive and 69· 9 ± 14 °C during ineffective energy applications ( P <0· 05). The time it took for the effect to appear was significantly longer in transiently effective pulses (10· 4 ± 7· 2 s) compared to permanently effective 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 applications. No procedure-related complications occurred. Conclusions Temperature-controlled radiofrequency ablation of manifest accessory pathways is highly effective and safe. The temperature response is faster and signficantly higher in left-sided energy applications compared to right-sided pulses. Peak temperature levels measured at the electrode tip are significantly higher during effective than ineffective pulses. Sudden rises in impedance are not com pletely prevented during temperature-controlled radiofrequency ablation of accessory pathway, although no procedure-related complications were noted in this patient cohort. (Eur Heart J 1996; 17: 445–452)