Temperature-controlled radiofrequency catheter ablation of manifest accessory pathways

Abstract

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 = 16) 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 preexcitation 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 10 s (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 ± 10.6 W; 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 effective 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 significantly 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 completely prevented during temperature-controlled radiofrequency ablation of accessory pathway, although no procedure-related complications were noted in this patient cohort.