Background: Actual in vivo tissue temperatures and the safety profile during highpower short-duration (HPSD) ablation of atrial fibrillation have not been clarified. Methods:We conducted an animal study in which, after a right thoracotomy, we implanted 6-8 thermocouples epicardially in the superior vena cava, right pulmonary vein, and esophagus close to the inferior vena cava. We recorded tissue temperatures during a 50 W-HPSD ablation and 30 W-standard ablation targeting an ablation index (AI) of 400 (5-15 g contact force).Results: Maximum tissue temperatures reached with HSPD ablation were significantly higher than that reached with standard ablation (62.7 ± 12.5 vs. 52.7 ± 11.4°C, p = 0.033) and correlated inversely with the distance between the catheter tip and thermocouple, regardless of the power settings (HPSD: r = −0.71; standard: r = −0.64). Achievement of lethal temperatures (≥50°C) was within 7.6 ± 3.6 and 12.1 ± 4.1 s after HPSD and standard ablation, respectively (p = 0.003), and was best predicted at cutoff points of 5.2 and 4.4 mm, respectively. All HPSD ablation lesions were transmural, but 19.2% of the standard ablation lesions were not (p = 0.011). There was no difference between HPSD and standard ablation regarding the esophageal injury rate (30% vs. 33.3%, p > 0.99), with the injury appearing to be related to the short distance from the catheter tip.Conclusions: Actual tissue temperatures reached with AI-guided HPSD ablation appeared to be higher with a greater distance between the catheter tip and target tissue than those with standard ablation. HPSD ablation for <7 s may help prevent collateral tissue injury when ablating within a close distance.

Introduction Neither the actual in vivo tissue temperatures reached with 90 W/4 s‐very high‐power short‐duration (vHPSD) ablation for atrial fibrillation nor the safety and efficacy profile have been fully elucidated. Methods We conducted a porcine study (n = 15) in which, after right thoracotomy, we implanted 6–8 thermocouples epicardially in the superior vena cava, right pulmonary vein, and esophagus close to the inferior vena cava. We compared tissue temperatures close to a QDOT MICRO catheter, between during 90 W/4 s‐vHPSD ablation during ablation index (AI: target 400)‐guided 50 W‐HPSD ablation, both targeting a contact force of 8–15 g. Results Maximum tissue temperature reached during 90 W/4 s‐vHPSD ablation did not differ significantly from that during 50 W‐HPSD ablation (49.2 ± 8.4°C vs. 50.0 ± 12.1°C; p = .69) and correlated inversely with distance between the catheter tip and the thermocouple, regardless of the power settings (r = −0.52 and r = −0.37). Lethal temperature (≥50°C) was best predicted at a catheter tip‐to‐thermocouple distance cut‐point of 3.13 and 4.27 mm, respectively. All lesions produced by 90 W/4 s‐vHPSD or 50 W‐HPSD ablation were transmural. Although there was no difference in the esophageal injury rate (50% vs. 66%, p = .80), the thermal lesion was significantly shallower with 90 W/4 s‐vHPSD ablation than with 50W‐HPSD ablation (381.3 ± 127.3 vs. 820.0 ± 426.1 μm from the esophageal adventitia; p = .039). Conclusion Actual tissue temperatures reached with 90 W/4 s‐vHPSD ablation appear similar to those with AI‐guided 50 W‐HPSD ablation, with the distance between the catheter tip and target tissue being shorter for the former. Although both ablation settings may create transmural lesions in thin atrial tissues, any resulting esophageal thermal lesions appear shallower with 90 W/4 s‐vHPSD ablation.

Background Neither the actual in vivo tissue temperatures reached with lesion size index (LSI)‐guided high‐power short‐duration (HPSD) ablation for atrial fibrillation nor the safety profile has been elucidated. Methods We conducted a porcine study (n = 7) in which, after right thoracotomy, we implanted 6–8 thermocouples epicardially in the superior vena cava, right pulmonary vein, and esophagus close to the inferior vena cava. We compared tissue temperatures reached during 50 W‐HPSD ablation with those reached during standard (30 W) ablation, both targeting an LSI of 5.0 (5–15 g contact force). Results Tmax (maximum tissue temperature when the thermocouple was located ≤5 mm from the catheter tip) reached during HPSD ablation was modestly higher than that reached during standard ablation (58.0 ± 10.1°C vs. 53.6 ± 9.2°C; p = .14) and peak tissue temperature correlated inversely with the distance between the catheter tip and the thermocouple, regardless of the power settings (HPSD: r = −0.63; standard: r = −0.66). Lethal temperature (≥50°C) reached 6.3 ± 1.8 s and 16.9 ± 16.1 s after the start of HPSD and standard ablation, respectively (p = .002), and it was best predicted at a catheter tip‐to‐thermocouple distance cut point of 2.8 and 5.3 mm, respectively. All lesions produced by HPSD ablation and by standard ablation were transmural. There was no difference between HPSD ablation and standard ablation in the esophageal injury rate (70% vs. 75%, p = .81), but the maximum distance from the esophageal adventitia to the injury site tended to be shorter (0.94 ± 0.29 mm vs. 1.40 ± 0.57 mm, respectively; p = .09). Conclusions Actual tissue temperatures reached with LSI‐guided HPSD ablation appear to be modestly higher, with a shorter distance between the catheter tip and thermocouple achieving lethal temperature, than those reached with standard ablation. HPSD ablation lasting <6 s may help minimize lethal thermal injury to the esophagus lying at a close distance.