Role of catheter location on local impedance measurements and clinical outcome with the new direct sense technology in cardiac ablation procedures

Local impedance drop-guided versus lesion size index-guided pulmonary vein isolation

BACKGROUND

Local tissue impedance drop (LID) and lesion size index (LSI) technologies are valuable for predicting effective lesion formation. This study compares the acute and long-term efficacy of LID-guided versus LSI-guided pulmonary vein isolation (PVI) for atrial fibrillation treatment.

METHODS

We retrospectively analyzed two patient groups undergoing radiofrequency PVI. In the LID-guided group (n = 35), ablation was performed without contact force monitoring, stopping at the LID plateau (target LID 12 Ohm posterior, 16 Ohm anterior). In the LSI-guided group (n = 31), ablation used contact force information with target LSI (5 anterior, 4 posterior). Both groups utilized a power of 40 W anterior and 30 W posterior, with < 6 mm inter-lesion distance. Gap mapping and touch-up ablation were done if necessary.

RESULTS

PVI was achieved with a significantly shorter ablation time in the LSI-guided group (25 min [21;31] vs 30 [27;35], p = 0.035). PV gaps were more frequent in the LID-guided group (74% vs 42%, p = 0.016). Over 11.5 ± 2.9 months follow-up, arrhythmia recurrence was higher in the LID-guided group (34.3% vs 16.1%, p = 0.037). A redo procedure performed in 10 (28.6%) patients in the LID-guided group and 3 (9.7%) in the LSI-guided group showed chronic PV reconnections in 7 out of 10 (70%) and 2 out of 3 (67%) patients, respectively.

CONCLUSIONS

LSI-guided ablation results in shorter ablation time and fewer PV gaps compared to LID-guided ablation. Despite initial success, LID-guided ablation had higher arrhythmia recurrence and PV reconnections during long-term follow-up compared to LSI-guided ablation.

Catheter-tissue contact optimizes pulsed electric field ablation with a large area focal catheter

INTRODUCTION

Pulsed electric field (PEF) ablation relies on the intersection of a critical voltage gradient with tissue to cause cell death. Field-based lesion formation with PEF technologies may still depend on catheter-tissue contact (CTC). The purpose of this study was to assess the impact of CTC on PEF lesion formation with an investigational large area focal (LAF) catheter in a preclinical model.

METHODS

PEF ablation via a 10-spline LAF catheter was used to create discrete right ventricle (RV) lesions and atrial lesion sets in 10 swine (eight acute, two chronic). Local impedance (LI) was used to assess CTC. Lesions were assigned to three cohorts using LI above baseline: no tissue contact (NTC: ≤∆10 Ω, close proximity to tissue), low tissue contact (LTC: ∆11-29 Ω), and high tissue contact (HTC: ≥∆30 Ω). Acute animals were infused with triphenyl tetrazolium chloride (TTC) and killed ≥2 h post-treatment. Chronic animals were remapped 30 days post-index procedure and stained with infused TTC.

RESULTS

Mean (± SD) RV treatment sizes between LTC (n = 14) and HTC (n = 17) lesions were not significantly different (depth: 5.65 ± 1.96 vs. 5.68 ± 2.05 mm, p = .999; width: 15.68 ± 5.22 vs. 16.98 ± 4.45 mm, p = .737), while mean treatment size for NTC lesions (n = 6) was significantly smaller (1.67 ± 1.16 mm depth, 5.97 ± 4.48 mm width, p < .05). For atrial lesion sets, acute and chronic conduction block were achieved with both LTC (N = 7) and HTC (N = 6), and NTC resulted in gaps.

CONCLUSIONS

PEF ablation with a specialized LAF catheter in a swine model is dependent on CTC. LI as an indicator of CTC may aid in the creation of consistent transmural lesions in PEF ablation.

Impact of contact force on the lesion characteristics of very high-power short-duration ablation using a QDOT-MICRO catheter

Background

Lesion size is reported to become larger as contact force (CF) increases. However, this has not been systematically evaluated in temperature-guided very high-power short-duration (vHPSD) ablation, which was therefore the purpose of this study.

Methods

Radiofrequency applications (90 W/4 s, temperature-control mode) were performed in excised porcine myocardium with four different CFs of 5, 15, 25, and 35 g using QDOT-MICRO™ catheter. Ten lesions for each combination of settings were created, and lesion metrics and steam-pops were compared.

Results

A total of 320 lesions were analyzed. Lesion depth, surface area, and volume were smallest for CF of 5 g than for 15, 25, and 35 g (depth: 2.7 mm vs. 2.9 mm, 3.0 mm, 3.15 mm, p < .01; surface area: 38.4 mm2 vs. 41.8 mm2, 43.3 mm2, 41.5 mm2, p < .05; volume: 98.2 mm3 vs. 133.3 mm3, 129.4 mm3, 126.8 mm3, p < .01 for all pairs of groups compared to CF = 5 g). However, no significant differences were observed between CFs of 15-35 g. Average power was highest for CF of 5 g, followed by 15, 25, and 35 g (83.2 W vs. 82.1 W vs. 77.1 W vs. 66.1 W, p < .01 for all pairs), reflecting the higher incidence of temperature-guided power titration with greater CFs (5 g:8.8% vs. 15 g:52.5% vs. 25 g:77.5% vs. 35 g:91.2%, p < .01 for all pairs except for 25 g vs. 35 g). The incidence of steam-pops did not significantly differ between four groups (5 g:3.8% vs. 15 g:10% vs. 25 g:6.2% vs. 35 g:2.5%, not significant for all pairs).

Conclusions

For vHPSD ablation, lesion size does not become large once the CF reaches 15 g, and the risk of steam-pops may be mitigated through power titration even in high CFs.