A dynamic model of radio frequency catheter ablation for the treatment of cardiac arrhythmias.

Abstract

Accurate knowledge of the spatial and temporal temperature distribution within the myocardium would be of value in predicting lesion size and shape during radio frequency (RF) catheter ablation. Finite difference solutions of the Laplace equation, which models power delivery by the RF catheter, and the Bioheat equation, which predicts temperature rise within the myocardium, were developed to accurately model lesion generation during RF ablation. This model included the effects of tissue and electrode heat conduction, tissue perfusion, and the convective losses within the heart chamber. Results indicated that the convective effects of blood flow within the heart chamber over the catheter were significant. More power could be applied before reaching 100°C when these convective cooling effects were included than without them. Electrodes of higher thermal conductivity were determined, by both numerical simulations and in vitro experiments, to promote more heat flux away from the electrode-tissue interface. Consequently, more power could be delivered resulting in larger lesions. The effects of tissue perfusion on intramyocardial temperatures and lesion size were investigated. Perfusion was found to decrease both of these compared to non-perfused tissue. This was particularly evident with longer energy delivery times. The power density model was used to characterize the power density relationship for both single and arrays of multiple catheter electrodes. The results from this model were used to design and implement a multipolar ablation technique. In vitro and in vivo experiments proved this technique was useful for generating longer, deeper lesions than traditional techniques and holds promise for treating atrial fibrillation and flutter. This technique may offer insight into the effects of thermal transfer properties on lesion formation. Furthermore, this model may be useful as a tool to design more effective catheters and energy delivery procedures to produce lesions of desired size and shape.