Comparison of In Vivo Tissue Temperature Profile and Lesion Geometry for Radiofrequency Ablation With a Saline-Irrigated Electrode Versus Temperature Control in a Canine Thigh Muscle Preparation

Background It is thought that only a thin layer of tissue adjacent to the electrode is heated directly by electrical current (resistive heating) during radiofrequency ablation. Most of the thermal injury is thought to result from conduction of heat from the surface layer. The purpose of this study was to determine whether lesion depth could be increased by producing direct resistive heating deeper in the tissue with higher radiofrequency power, allowed by cooling the ablation electrode with saline irrigation to prevent the rise in impedance that occurs when the electrode-tissue interface temperature reaches 100°C. Methods and Results In 11 anesthetized dogs, the thigh muscle was exposed and bathed with heparinized canine blood (36°C to 37°C). A 7F catheter, with a central lumen, a 5-mm tip electrode with six irrigation holes, and an internal thermistor, was positioned perpendicular to the thigh muscle and held at a constant contact weight of 10 g. Radiofrequency current was delivered to 145 sites (1) at h...