Long ablation cycles result in increased depth of multi-electrode ablation lesions using pulsed radiofrequency energy

A RF controller that sequentially distributes RF energy to up to 4 electrodes in 5ms pulses was used to create linear lesions in vitro and in vivo. A quad-polar ablation catheter with four 4mm electrodes was used for the ablation of bovine myocardium in blood at 60 degrees C with 50W. The temperature, energy, and lesion shape were measured from ablations of 1, 2, 3, 4, and 5 minutes. Results were compared to 2 and 5-minute ablations performed in. vivo. All the lesions were continuous. In vitro, lesion depth increased with ablation cycle and was directly proportional to energy (R=0.89). Lesion length was approximately 28mm in all cases. In vivo 2 min vs. 5 min lesion depth was 3.5+/-0.7 vs. 4.8+/-0.7mm (p=0.01),with similar length (20+/-8 vs. 24+/-8mm) and temperature (46+/-5 vs. 47+/-4 degrees C). It can be concluded that lesion depth of ablations from multiple electrodes increases with increasing ablation duration.