Proactive esophageal cooling during laser cardiac ablation: A computer modeling study

BACKGROUND AND OBJECTIVES

Laser ablation is increasingly used to treat atrial fibrillation (AF). However, atrioesophageal injury remains a potentially serious complication. While proactive esophageal cooling (PEC) reduces esophageal injury during radiofrequency ablation, the effects of PEC during laser ablation have not previously been determined. We aimed to evaluate the protective effects of PEC during laser ablation of AF by means of a theoretical study based on computer modeling.

METHODS

Three-dimensional mathematical models were built for 20 different cases including a fragment of atrial wall (myocardium), epicardial fat (adipose tissue), connective tissue, and esophageal wall. The esophagus was considered with and without PEC. Laser-tissue interaction was modeled using Beer-Lambert's law, Pennes' Bioheat equation was used to compute the resultant heating, and the Arrhenius equation was used to estimate the fraction of tissue damage (FOD), assuming a threshold of 63% to assess induced necrosis. We modeled laser irradiation power of 8.5 W over 20 s. Thermal simulations extended up to 250 s to account for thermal latency.

RESULTS

PEC significantly altered the temperature distribution around the cooling device, resulting in lower temperatures (around 22°C less in the esophagus and 9°C in the atrial wall) compared to the case without PEC. This thermal reduction translated into the absence of transmural lesions in the esophagus. The esophagus was thermally damaged only in the cases without PEC and with a distance equal to or shorter than 3.5 mm between the esophagus and endocardium (inner boundary of the atrial wall). Furthermore, PEC demonstrated minimal impact on the lesion created across the atrial wall, either in terms of maximum temperature or FOD.

CONCLUSIONS

PEC reduces the potential for esophageal injury without degrading the intended cardiac lesions for a variety of different tissue thicknesses. Thermal latency may influence lesion formation during laser ablation and may play a part in any collateral damage.

Evaluation of linear lesion formation and thermodynamics by dragging ablation with the third-generation laser balloon

Background

The lesion formation properties of a motorized rotational delivery (RAPID) mode, third-generation laser balloon (LB3) ablation compared to point-by-point laser ablation in patients with atrial fibrillation remain unclear.

Objective

The purpose of this study was to assess lesion characteristics and thermodynamics in LB3 ablation with a RAPID mode in vitro model.

Methods

Chicken muscles were cauterized using LB3 in RAPID mode with 13 W and 15 W and 50% overlapped point-by-point fashion with 7 W/30 seconds, 8.5 W/20 seconds, 10 W/20 seconds, and 12 W/20 seconds. Lesion depth, width, and continuity were compared. Lesion continuity was classified by the visible gap degree categorized from 1 (perfect) to 3 (poor). Thermodynamics and maximum tissue temperatures were assessed under infrared thermographic monitoring. Fifteen and 5 lesions were evaluated per ablation protocol for measurement of lesion size and continuity and for thermographic assessment, respectively.

Results

Lesion depth and width were smaller in RAPID mode laser ablation than point-by-point laser ablation (P <.001). However, RAPID mode laser ablation revealed sufficient mean lesion depth of 5 mm or more. Lesion continuity was 1 (perfect) in all samples in RAPID mode laser ablation and point-by-point laser ablation (P = 1). Infrared thermographic observation demonstrated fast and gapless linear lesion formation with thermal stacking in RAPID mode laser ablation. Maximum tissue temperature was lower in RAPID mode laser ablation than point-by-point laser ablation (P <.001).

Conclusion

RAPID mode LB3 ablation could provide fast, gapless, and acceptable lesion formation with thermal stacking and moderate tissue temperature rise.

Laser balloon in pulmonary vein isolation for atrial fibrillation: current status and future prospects

INTRODUCTION

Visually guided laser balloon (LB) catheter has been an established modality dedicated for pulmonary vein (PV) isolation in patients with atrial fibrillation. The newly updated version of this novel device has technically evolved recent years.

AREAS COVERED

This review will summarize the contemporary technical evolution of LB catheter. Available efficacy outcomes and the historical change of ablation style will be evaluated. Furthermore, the future perspectives for clinical practice are discussed.

EXPERT COMMENTARY

The initial LB ablation system provided comparable clinical results in PV isolation with other technologies, but with a unique strategical concept enabling the direct visualization of the tissue to cauterize. With multigenerational development, the LB catheter has been equipped with more compliant balloon for favorable PV occlusion and a robotically motor driven continuous ablation mode (RAPID mode). These technical innovations changed the concept of the ablation strategy using LB catheter as 'point-by-point' into 'single-shot' fashion. The remaining tasks are further improvements such as equipping with real-time recording system of intracardiac electrogram, durable structured balloon and the instrument for visualizing the cauterization area in a 360-degree panoramic view, which includes potential possibilities to develop this novel device to the more optimal device for PV isolation.

Evaluation of different ablation strategies verifying the optimal overlap ratio in point-by-point laser balloon ablation for patients with atrial fibrillation

Background

Optimal overlap ratio remains unclear in point-by-point laser balloon (LB) ablation.

Objective

This study sought to determine the optimal overlap strategy with target energies on the acute and chronic outcomes in LB pulmonary vein (PV) isolation (PVI).

Methods

Consecutive 38 patients (148 PVs) with atrial fibrillation underwent the first-generation LB PVI with the following protocols based on the overlap ratios for each PV anterior/posterior wall: 50%/50% (13 patients [49 PVs], group A), 50%/25% (15 patients [60 PVs], group B), and 25%/25% (10 patients [39 PVs], group C). High energies (240–255 J: 12 W / 20 seconds, 8.5 W / 30 seconds), moderate energies (200–210 J: 10 W / 20 seconds, 7 W / 30 seconds), and low-to-moderate energies (low, 165–170 J: 5.5 W / 30 seconds, 8.5 W / 20 seconds) were targeted for left PV anterior walls, right PV anterior walls, and bilateral PV posterior walls, respectively. First-pass PVI, the other procedure-related data, and atrial tachyarrhythmia recurrences were analyzed.

Results

First-pass PVI rate per PV was higher in group A (94%) than in group B (88%) and group C (62%) (P < .001). All PVs were finally isolated. First-pass time, total LB PVI time, complications, and atrial tachyarrhythmia recurrences during a mean follow-up of 11 ± 5 months did not differ between the groups. A few residual gaps after first-pass LB ablations were found for PV anterior walls even in group A and group B.

Conclusion

Sufficiently overlapped LB ablation promises a high rate of first-pass PVI without adverse outcomes. High energy could be required for PV anterior walls.

Validation of lesion durability following pulmonary vein isolation using the new third-generation laser balloon catheter in patients with recurrent atrial fibrillation

BACKGROUND

The second- and third-generation endoscopic ablation systems (EAS2 and EAS3) have been launched in recent years. We aimed to assess the lesion durability as well as gap localization using the multigenerational novel technologies in patients with recurrent atrial fibrillation (AF).

METHODS

Consecutive patients who underwent second ablation for recurrent AF following the initial pulmonary vein isolation (PVI) with EAS2 or EAS3 were retrospectively investigated. The persistent durability of PVI, gap localization at the second procedure, and procedural/anatomical features of durable PVI were analyzed.

RESULTS

Among 225 patients treated with EAS3 (N = 125) and EAS2 (N = 100), 34 patients (EAS3: 13 patients, 50 PVs, EAS2: 21 patients, 82 PVs) underwent a second procedure because of recurrent AF mean 11.9 ± 9.3 months after the initial procedure. Persistent isolation of all four PVs was recorded in 6 (46.2%) patients in EAS3 group and 4 (19.1%) patients in EAS2 group (p = 0.130). Ninety-one out of 132 (68.9%) PVs were persistently isolated with a higher rate in EAS3 group (82.0% vs. EAS2 group: 61.0%, p = 0.0113). A total of 45 gaps were recorded in 41 PVs. Right superior PV (RSPV) was the predominantly common reconnected vein (15 gaps, 14 PVs) irrespective of generations (EAS3: 4 gaps in 3 PVs and EAS2: 12 gaps in 11 PVs). Logistic multivariate regression analysis revealed ablation without reduced energy dose (5.5-7 W) as an independent predictor of durable PVI [adjusted OR: 3.70, 95% CI (1.408-10.003)], p = 0.008].

CONCLUSION

The technical innovation resulted in a higher lesion durability in EAS3-guided PVI in patients with recurrent AF. The most common gap location was found at RSPV in successor EASs. Ablation without reduced energy was a predictor of durable PVI in successor EASs.

Effect of the Balloon Size on Lesion Formation During Visually Guided Laser Balloon Ablation in an In Vitro Model

BACKGROUND

It is unclear whether balloon size can influence lesion formation. The aim of this study was to evaluate the impact of balloon size on lesion formation during laser balloon procedures in an in vitro model.Methods and Results:Laser energy was applied to chicken muscle using a first generation laser balloon. Laser ablation was performed with 2 different balloon sizes (18 mm and 32 mm) using 2 different power settings (12 W/20 s and 8.5 W/20 s) on the chicken muscle. The lesion characteristics, including maximum lesion depth, maximum lesion diameter, surface diameter and depth at maximum diameter, were compared between the 18-mm and 32-mm balloon groups at 12 W/20 s and 8.5 W/20 s, respectively. We created 40 lesions using laser energy at 12 W/20 s and 80 lesions at 8.5 W/20 s. At both power settings, the maximum lesion depth and the depth at the maximum diameter were larger in the 18-mm than in the 32-mm balloon group. At both power settings, the maximum lesion diameter and the surface diameter were smaller in the 18-mm than in the 32-mm balloon group.

CONCLUSIONS

The balloon size could affect the lesion formation during laser balloon ablation. The lesion with the larger balloon size was wider and shallower than the lesion with the smaller balloon size.

Comparison of dragging ablation and point-by-point ablation with a laser balloon on linear lesion formation

INTRODUCTION

Lesion size and continuity in dragging laser balloon (LB) ablation, which may enable fast and durable pulmonary vein isolation for atrial fibrillation, are unknown. We evaluated the differences in size and continuity of linear lesions formed by dragging ablation and conventional point-by-point ablation using an LB in vitro model.

METHODS AND RESULTS

Chicken muscles were cauterized using the first-generation LB in dragging and point-by-point fashion. Dragging ablation was manually performed with different dragging speeds (0.5-2°/s) using an overlap ratio of the beginning and last site during one application at 12 W/20 s and 8.5 W/30 s. Point-by-point ablation was performed with 25% and 50% overlap ratios at six energy settings (5.5 W/30 s to 12 W/20 s). Lesion depth, width, and continuity were compared. Lesion continuity was assessed by the surface and deep visible gap degree categorized from 1 (perfect) to 3 (poor). Twenty lesions were evaluated for each ablation protocol. Lesion depth and width in dragging ablation at high power (12 W) were comparable with most measurements in point-by-point ablation. Lesion depth and width were smaller at faster-dragging speed and lower power (8.5 W) in dragging ablation. The surface visible gap degree was better in dragging ablation at all dragging speeds than a 25% overlapped point-by-point ablation (p < .001).

CONCLUSION

Dragging LB ablation at high power provides deep and continuous linear lesion formation comparable with that of point-by-point LB ablation. However, lesion depth and width depending on the dragging speed and power.