In vivo tissue temperatures during 90 W/4 sec‐very high power‐short‐duration (vHPSD) ablation versus ablation index‐guided 50 W‐HPSD ablation: A porcine study

Abstract

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.

Characteristics of tissue temperature during ablation with THERMOCOOL SMARTTOUCH SF versus TactiCath versus QDOT MICRO catheters (Qmode and Qmode+): An in vivo porcine study

“…Twenty-nine pigs were prepared for the study, as previously described. [5][6][7] After establishment of deep anesthesia, vascular access was obtained percutaneously, and the surface electrocardiogram and blood pressure were monitored.…”

“…Thermocouple implantation and recording methods were reported previously. [5][6][7] After right-sided thoracotomy, 6−8 Type T (copperconstantan) thermocouples (Physitemp Instruments; LLC) (time constant: 0.1 s; diameter 0.064 mm; accuracy: ±0.42°C) were implanted epicardial at the superior vena cava (SVC; 3.0 ± 0.0 thermocouples) along the phrenic nerve, at the right PV (RPV; 2.0 ± 0.0 thermocouples), and near the esophagus (2.4 ± 0.32 thermocouples) (Figure 1A). A radiopaque marker was attached to the tip of each thermocouple to aid in fluoroscopic localization.…”

“…All measurements were taken at a consistent point within the respiratory cycle. Our assessment included the following aspects [5][6][7] : (1) the relationship between maximum tissue temperature (T max ) and catheter tip-to-thermocouple distance at all sites, and (2) T max and time to reach a lethal tissue temperature ≥50°C, considered lethal due to tissue damage [9][10][11] (t−T ≥ 50°C), (3) time to T max (t−T max ), and…”

“…3 Several catheter options have been clinically introduced to facilitate HPSD and vHPSD procedures, including the THERMOCOOL SMARTTOUCH SF (STSF) (Biosense Webster), TactiCath ablation catheter, sensor enabled (TactiCath) (Abbott, Inc.), and QDOT MICRO (Biosense Webster) catheters. While HPSD and vHPSD ablation using various catheters have demonstrated relatively shallow lesions with acceptable clinical effectiveness and safety profiles, [4][5][6][7][8] differences in irrigation flow rate, energy control method, ablation indices, and catheter tip design may influence biophysics and lesion geometries. Nevertheless, the exact impact of these catheters on tissue remains to be fully understood.…”

“…Our prior in vivo animal studies involving STSF, TactiCath, and QDOT MICRO catheters have explored tissue temperatures in epicardial venoatrial tissues and collateral tissue damage. [5][6][7] In light of this background, comparing tissue temperature dynamics during 50 W HPSD guided by ablation indices and 90 W/4 s vHPSD ablation may yield valuable insights into achieving more effective and safer lesions with HPSD and vHPSD ablation settings across various catheters. Therefore, the primary objective of this study was to assess the differences in in-vivo tissue temperature dynamics and collateral damage, including phrenic nerve injury and esophageal injury, during 50 W HPSD ablation guided by ablation index (AI) using the STSF and QDOT MICRO catheters and by lesion size index (LSI) using the TactiCath catheter, as well as 90 W/4 s vHPSD ablation using the QDOT MICRO catheter.…”