The Biophysics of Passive Convective Cooling During Catheter Ablation with Gold versus Platinum Electrodes and Multielectrode Phased Radiofrequency Energy Delivery

INTRODUCTION: During radiofrequency (RF) catheter ablation, convective cooling of the ablated tissue by circulating blood allows higher power delivery and deeper penetration of volume heating without excess surface heating. The study aim was to characterize ablation lesions using electrode materials with differing thermal conductivities and magnitudes of passive convective cooling utilizing duty-cycled RF energy. METHODS AND RESULTS: RF ablations using a linear array of 4 3-mm platinum electrodes (n = 228) were compared to an array with gold electrodes (n = 244). RF was delivered using temperature feedback power control, in a blended bipolar:unipolar mode (2:1 and 4:1), to exposed porcine thigh muscle superfused with heparinized blood. For gold electrodes, lesion depths were 4.1 ± 0.8 mm in the 2:1 ablation mode and 3.7 ± 0.9 mm in the 4:1 ablation mode, versus 3.7 ± 1.0 mm and 3.3 ± 1.0 mm with platinum (P < 0.001 vs. gold, P = 0.004 platinum 2:1 vs. 4:1). More efficient passive cooling at all flow rates with gold versus platinum resulted in a lower mean electrode temperature and a higher proportion of ablations reaching maximum power before achieving target temperature. Therefore, the mean ablation power was higher with gold (6.5+2.1 vs. 5.5+2.3 W, P < 0.001), and lesion depth was greater (3.9+0.8 mm vs. 3.5+1.0 mm, P < 0.001) compared to platinum. CONCLUSIONS: Passive convective cooling during RF ablation is more efficient with gold compared to platinum electrodes, particularly when ablations are temperature limited. Using temperature feedback power control, deeper lesions can be reliably achieved with gold electrodes.