Figure - available from: Journal of Interventional Cardiac Electrophysiology
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Panel A Linear association between LI drop and baseline LI. The size and color of the dots are proportional to RF time duration: shorter RF application times (smaller dots with color in the blue spectrum) are needed to achieve the target LI drop if the baseline LI is > 160 Ω. Panel B Probability density distribution of baseline LI across the 5 CF groups. The overlapping of the distributions indicates a non-significant statistical difference. Panel C Baseline LI boxplots in the 5 CF groups, with color stratification according to acute conduction block (orange) or conduction gap (blue). Panel D Baseline LI boxplots in the 6 Orientation angle groups showing no impact of catheter orientation angle on baseline LI
Source publication
Background
Local impedance (LI) drop predicts acute conduction block during pulmonary vein isolation (PVI). Whether the LI drop predicts also the achievement of left atrial posterior wall isolation (LAPWI) in persistent atrial fibrillation (PersAF) patients is unknown. We evaluated the efficacy and the safety of LI drop-guided LAPW ablation by usin...
Citations
... Impedance metrics have been useful clinical tools in monitoring resistive heating and predicting lesion transmurality for RF ablation [22][23][24] . When used in a clinical RF workflow, targeting a >20 LI drop effectively predicted lesion efficacy and durability 25,26 . For PEF ablation, LI is a useful way to measure CTC and confirm optimal catheter placement for lesion formation. ...
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 RV lesions and atrial lesion sets in 10 swine (8 acute, 2 chronic). Local impedance (LI) was used to assess CTC. Lesions were assigned to 3 cohorts using LI above baseline: No Tissue Contact (NTC: ≤∆10Ω, close proximity to tissue), Low Tissue Contact (LTC: ∆11-29Ω), and High Tissue Contact (HTC: ≥∆30Ω). Acute animals were infused with triphenyl tetrazolium chloride (TTC) and sacrificed ≥2hrs 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±1.96mm vs 5.68±2.05mm, p=0.999; width: 15.68±5.22mm vs 16.98±4.45mm, p=0.737) while mean treatment size for NTC lesions (n=6) was significantly smaller (1.67±1.16mm depth, 5.97±4.48mm width, p<0.05). 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.
... Pre-clinical and clinical evaluation of this metric has shown that LI outperforms generator impedance in characterizing tissue composition and predicting lesion formation [6,7]. Moreover, LI drop during ablation has proved to be an excellent predictor of chronic PVI segment conduction block in patients with paroxysmal atrial fibrillation (AF) [8], and its combination with CF information has been shown to effectively guide posterior wall isolation in patients with persistent AF [9]. However, nothing has been published on the usefulness of this variable in the context of PVC ablation. ...
... RF energy was applied in a point-by-point fashion in the power control mode at a fixed power of 50 W, while making sure that a minimum CF of 3 g was applied. On the basis of recent experiences with the Stablepoint™ catheter in the atrium [9,10], we aimed to achieve an LI drop of at least 30 Ω for each ablation lesion in the OT. If the target LI drop was not achieved, RF delivery was prolonged for up to a maximum of 50 s, according to physician discretion. ...
Background
Contact force (CF)-sensing catheters have not proved superior to standard catheters in the ablation of premature ventricular contractions (PVCs) from the right and left ventricular outflow tract (RVOT, LVOT). In this context, the utility of measuring local impedance (LI) is not known. We aimed to ascertain whether the use of a catheter combining LI and CF information was associated with superior outcomes in comparison with other catheter technologies.
Methods
We compared three groups of 40 propensity-matched patients with PVCs from the OTs, ablated by means of different catheter technologies: a CF-plus LI-featured catheter, an LI-featured catheter, and a standard irrigated catheter.
Results
The CF + LI group displayed a significantly lower risk of PVC recurrence than the standard ablation group (HR, 0.22; 95%CI, 0.07–0.71; p = 0.01). In the CF + LI group, LI drop and RF time were the only predictors of successful lesions (OR = 1.19, CI: 1.13–1.26, p < 0.001; OR = 1.06 CI: 1.01–1.07, p = 0.044, respectively). In the coronary cusps, unlike the RVOT/LVOT region, CF was not associated with LI drop (p = 0.48), and RF duration showed a linear relationship with LI drop (p < 0.001).
Conclusions
The use of ablation catheters that combine CF and LI information is associated with increased success in the RF ablation of PVCs from the OTs. LI drop is the most important predictor of effective lesions, but its behavior depends on the ablation site: in the coronary cusps, unlike the RVOT/LVOT region, longer RF application times are needed in order to achieve LI drops associated with successful outcomes.
Registry and registration no. of the study/trial
NCT03793998.
Introduction
The relationships between baseline tissue local impedance (LI), contact force (CF), atrial fibrosis, and atrial rhythm are uninvestigated in a clinical setting. We compared the relationship of LI and CF between atrial fibrillation (AF) and sinus rhythm (SR) accounting for the effects of atrial fibrosis as assessed by bipolar voltage and LI.
Methods
Patients undergoing persistent AF ablation were recruited. LI was recorded referenced to patient blood pool (LIr) and concurrent to changes in CF, with data collected at the same locations in AF and SR.
Results
Twenty patients were recruited. 109 locations were sampled obtaining 1903 data points (SR: 966, AF: 937). CF correlated strongly with LI (repeated measures correlation = 0.64). The relationship between CF and LIr was logarithmic. Rhythm and CF had a significant main (both p < .0005) and interaction effect ( p = .022) on tissue LI: AF demonstrated higher LIr values than SR for similar CF. Bipolar voltage had no effect on the relationship of CF to LIr in either rhythm. Assessing fibrosis using LIr showed an interaction effect with CF for LIr in SR and AF, (SR: p < .0005, AF: p = .01), with increased fibrosis showing lesser change in LIr per gram of CF.
Conclusions
CF and rhythm significantly affect the measured LIr of LA myocardium. Optimal catheter‐tissue coupling may be better achieved with higher levels of CF and in AF rather than SR. Atrial fibrosis, as assessed by LIr but not bipolar voltage, affected the CF–LI relationship.
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.
Background
The lesion size index (LSI) predicts radiofrequency (RF) ablation lesion size and is an established parameter for pulmonary vein isolation. However, the effectiveness and safety of LSI for cavotricuspid isthmus (CTI) linear ablation remain unclear.
Methods
This single-center retrospective study included 50 of patients (67 ± 10 years, 68% male) who underwent de novo CTI linear ablation between July 2020 and December 2020. The LSI target was set at 5.0 and 4.0 for the anterior 2/3 and posterior 1/3 segments, respectively. Acute procedural parameters of ablation were evaluated.
Results
Acute bidirectional CTI block was achieved in all patients with an RF application time of 4.0 min (3.1–5.0 min), RF application number of 15 ± 7, and length of CTI of 36.9 ± 9.3 mm. First-pass bidirectional conduction block of the CTI was achieved in 39/50 (78%) patients. No major complications were observed. The contact force (CF) per application was significantly lower in the gap tag group than in the non-gap tag group (7 g [7–8 g] vs. 10 g [7–12 g], P = 0.0284).
Conclusions
LSI-guided CTI linear ablation is an effective and safe treatment approach. CF affects gap formation, even when the target LSI is the same.
