Effect of Skin Electrode Location on Radiofrequency Ablation Lesions: An In Vivo and a Three‐Dimensional Finite Element Study

OBJECTIVES: To assess the effect of skin electrode location on radiofrequency (RF) ablation lesion dimensions and energy requirements. BACKGROUND: Little is known about the effects of skin electrode location on RF ablation lesion dimensions and efficiency. METHODS AND RESULTS: Temperature-controlled ablation at 60 degrees C for 60 seconds was performed in six sheep. Paired lesions were created in the lateral, anterior, posterior, and septal walls of both the ventricles. For group 1 lesions, the skin electrode was positioned directly opposite the catheter tip (optimal). For group 2 lesions, we used either the standard posterior location or an anterior location if the posterior skin electrode location was used for group 1. Group 1 lesions were 5.8+/-0.8 mm deep and 9.3+/-1.9 mm wide, compared with 4.6+/-1.0 mm deep and 7.7+/-1.9 mm wide group 2 lesions (P < or = 0.001). Group 1 lesion dimensions also had less variability. A finite element model was used to simulate temperature-controlled ablation and to study the effect of skin electrode locations on lesion dimensions, ablation efficiency, and blood heating. The optimal location was 1.6 times more efficient, and the volume of blood heated to > or = 90 degrees C was 0.005 mm3 for optimal versus 2.2 mm3 for the nonoptimal location. CONCLUSION: Optimal skin electrode placement: (1) creates deeper and larger lesions; (2) reduces lesion size variability; and (3) decreases blood heating.