Effect of electrode contact on lesion growth during temperature controlled radiofrequency ablation

Radiofrequency (RF) energy is commonly used to ablate cardiac tachyarrhythmias. It has been shown that lesion growth reaches a steady state during temperature controlled radiofrequency ablation. However, it is unknown if the electrode-tissue contact has an effect on the time course of lesion growth. A three dimensional finite element model was used to simulate temperature controlled RF ablation and to study the effect of electrode penetration depth (EPD) on lesion growth with time. Three different EPDs were used to model catheter tip penetration into an irregular endocardial surface. RF application was simulated for 120s through a 4mm, 7Fr electrode with 1.25, 2.5, and 4mm EPDs (catheter positioned perpendicularly to the tissue surface). The results indicated that: 1) Lesion size reached steady state after approximate to 90s at all EPDs, 2) mean power decreased as EPD increased, 3) lesion depth was proportional to the electrode depth, 4) lesion width changed significantly as EPD increased from 1.25 to 2.5mm, and (5) impedance drop was greater for deeper EPD. To summarize, electrode penetration depth has a significant effect on lesion dimensions; however; the lesion growth reaches a steady state after approximately 90 seconds irrespective of the EPD.