In vivo tissue temperature during lesion size index-guided 50W ablation versus 30W ablation: A porcine study

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.

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).

T_max  (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).

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.