Epicardial Ablation Biophysics and Novel Radiofrequency Energy Delivery Techniques.

Important physiologic and anatomic differences exist between the epicardium and endocardium, particularly of the ventricles, and these differences affect ablation biophysics. Absence of passive convective effects conferred by circulating blood as well as the presence of epicardial fat and vessels and absence of intracavitary ridges and structures affect ablation lesion size when performing epicardial catheter-based ablation, whether using radiofrequency or cryothermal energy. Understanding differential effects in each environment is important in informing strategies to increase ablation lesion depth. When using actively cooled radiofrequency ablation, local impedance can be altered to selectively augment energy delivery.