Comparison of In Vivo Tissue Temperature Profile and Lesion Geometry for Radiofrequency Ablation With High Power-Short Duration and Moderate Power-Moderate Duration: Effects of Thermal Latency and Contact Force on Lesion Formation.

Background - With short radiofrequency (RF) applications, tissue temperature continues to rise after RF-termination ("thermal latency"), which may result in lesion growth after RF-termination. The purpose was to compare in-vivo tissue temperature profile (thermal latency), lesion size and the incidence of steam pop and thrombus between RF-ablation with very-high-power-very-short-RF(90W/4s), high-power-short-RF(50W/10s) and moderate-power-moderate-RF(30W/30s) in a canine thigh muscle preparation and beating heart. Methods - In the thigh muscle preparation (5dogs), a 3.5mm ablation-electrode with 66 or 56 small irrigation holes (QDOT-Micro or ThermoCoolSmartTouch-SF, respectively) was held perpendicular or parallel to the muscle at 10 or 30g contact force (CF). Total of 120RFs were delivered at 90W/4s(QDOT-catheter), 50W/10s or 30W/30s(SF-catheter). Electrode temperature, electrode-tissue-interface temperature and tissue temperatures at 3mm and 7mm-depths were measured. In 6 closed-chest dogs, total of 72RFs were delivered in the ventricle at 90W/4s, 50W/10s or 30W/30s. Results - In the thigh muscle preparation, tissue temperatures and lesion size (depth, diameter and volume) were lowest/smallest for RFs at 90W/4s, followed by 50W/10s and greatest for 30W/30s. Thermal latency (Δtemperature and duration) was greatest for RFs at 90W/4s, followed by 50W/10s and smallest for 30W/30s (p<0.01). Effective tissue heating (area under curve≥50°C at 3mm-depth) was observed after RF-termination in 88.0±7.6% with 90W/4s, 57.7±14.6% with 50W/10s, and only 31.9±8.5% with 30W/30s (p<0.01). In beating hearts, lesion size was also smallest with 90W/4s and greatest with 30W/30s RFs. Increasing CF significantly increased lesion depth in all three groups. There was no significant difference in the incidence of steam pop or thrombus between three groups. Conclusions - Tissue temperatures and lesion size (depth, diameter and volume) were lowest/smallest for RF-applications at 90W/4s, followed by 50W/10s and greatest for 30W/30s. The greater thermal latency for 90W/4s RF-applications suggests that a significant portion of lesion is created after RF-termination due to conductive tissue heating.