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In Vivo Tissue Temperatures During Lesion Size-Guided 50W Ablation Versus 30W Ablation: A porcine study.

BACKGROUND
Neither the actual in vivo tissue temperatures reached with lesion size index (LSI)-guided high-power short-duration (HPSD) ablation for atrial fibrillation (AF) nor the safety profile have been elucidated.


METHODS
We conducted a porcine study 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 50W-HPSD ablation with those reached during standard (30W) ablation, both targeting a lesion size index (LSI) of 5.0 (5-15 g contact force).


RESULTS
Maximum tissue temperature reached during HPSD ablation was significantly higher than that reached during standard ablation (58.8±12.5°C vs 54.2±11.4ºC; P=0.033) and correlated inversely with distance between the catheter tip and the thermocouple, regardless of the power settings (HPSD: r=-0.66; standard: r=-0.63). Lethal temperature (≥50°C) was reached 6.3±1.8 seconds and 16.9±16.1 seconds after the start of HPSD and standard ablation, respectively (P=0.002), and it was best predicted at a catheter tip-to-thermocouple distance cut-point of 2.8 mm 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 (30% vs 33.3%, P>0.99), 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=0.09).


CONCLUSIONS
Actual tissue temperatures reached with LSI-guided HPSD ablation appear to be higher, with shorter distance between the catheter tip and thermocouple achieving lethal temperature, than those reached with standard ablation. HPSD ablation lasting <6 seconds may help minimize lethal thermal injury to the esophagus lying at close distance. This article is protected by copyright. All rights reserved.