Temperature-guided radiofrequency catheter ablation of closed-chest ventricular myocardium with a novel thermistor-tipped catheter

Abstract

Successful lesion formation using radiofrequency energy requires adequate tissue heating. Temperature monitoring during ablation may thus improve the efficiency of radiofrequency catheter ablation. Each of five anesthetized, closed-chest adult mongrel dogs weighing 19 to 24 kg received a single pulsed ablation at four left ventricular and two right ventricular sites using a thermistor-tipped 2 mm electrode catheter. The maximum temperature at the electrode-tissue interface was preset at 90° C and current delivered for 40 seconds (method A) or at 70° C for 40 seconds (method B 1) or 80 seconds (method B 2). With method C, the temperature was set at 90° C for 20 seconds, after which the temperature setting was turned off and ablation continued until impedance increased or the temperature reached ≥ 100° C. The size of the resultant lesion was greater with method A than with methods B 1, B 2 or C (mean length × width × depth, 5.6 × 4.8 × 6.5 vs 4.1 × 4.0 × 5.1 vs 4.2 × 4.0 × 5.2 vs 5.0 × 4.3 × 5.7 mm, respectively; p < 0.01). There was no significant difference in lesion size between pulse durations of 40 seconds (group B 1) and 80 seconds (group B 2). Only two ablations, both in the anteroapical right ventricle, resulted in a marked rise in impedance without the temperature reaching ≥ 100° C. We conclude that temperature (and thus impedance) monitoring improves control and efficacy of lesion formation during radiofrequency catheter ablation.