Novel simultaneous assessment of contact force and local impedance for radiofrequency catheter ablation guidance

Funding Acknowledgements Type of funding sources: None. Background Contact force (CF) and local impedance (LI) have been separately established for radiofrequency (RF) catheter ablation guidance, enabling estimation of mechanical catheter stability and underlying electrical tissue substrate properties, respectively. However, simultaneous investigation for evaluation of combined electromechanical coupling during RF energy delivery has not been conducted in-human. Purpose Evaluation of the relationship of CF to LI during catheter-based RF atrial fibrillation / tachycardia ablation. Methods In this explorative study, patients presenting with recurrent atrial fibrillation and/or atrial tachycardia for ablation after previous index AF ablation were enrolled. A novel open-irrigated single-tip ablation catheter capable of continuously assessing CF and LI was used after initial high-density mapping. Baseline LI, CF and local bipolar voltage were assessed for each ablation site, with subsequent analysis of mean CF and the force-time integral (FTI) during ablation as well as the maximum LI drop (ΔLI), reflecting acute lesion formation during RF delivery. Results In 11 patients [n = 5 female, mean age 66 ± 11 years, median previous procedures n = 2 (interquartile range 1-2)], overall 364 RF energy deliveries were analysed after exclusion of lesions indicating catheter instability or lesions with a RF-duration <10 s. Acute procedural success was reached in all patients, with no periprocedural complications observed. CF showed a weak correlation to baseline LI during linear regression analysis (r = 0.29, p < 0.001). Baseline LI as well as ΔLI were higher in regions of high (>0.5 mV) vs intermediate (0.1–0.5 mV) or low (<0.1 mV) voltage (baseline LI: p < 0.001, ΔLI: p = 0.04). The ΔLI was more strongly related to baseline LI (r = 0.38, p < 0.001) compared to mean CF / FTI during ablation (r = 0.16, p = 0.003 / r = 0.15, p = 0.008). However, a CF ≥5 g and FTI ≥400 gs were associated with increased ΔLI compared to CF levels <5 g / FTI <400 gs (CF: p = 0.006, FTI: p = 0.008, Figure 1). Ablation sites in the right atrium displayed higher ΔLI when applying sufficient mean CF levels ≥5 g compared to the left atrium (22 (16-30) vs 16 (13-22) Ω, p = 0.008). Sufficient lesion formation was previously observed to be accomplished at a ΔLI ≥20 Ω, which was predicted best by baseline LI [odds ratio 1.07 (confidence interval 1.05-1.09), p < 0.001)] compared with CF [1.01 (0.97-1.05), p = 0.636], FTI [1.002 (1.00-1.003), p = 0.02] and local voltage [1.064 (0.76–1.4), p = 0.38]. Conclusion Simultaneous monitoring of LI and CF enables real-time analysis of (1) local catheter stability by pertaining CF levels beyond 5 g while concomitantly (2) characterising underlying substrate using the baseline LI and (3) estimating the effect of applied RF energy on lesion formation by assessing the ΔLI. This may enhance intra-procedural evaluation of effective RF delivery for tailored ablation procedures. Abstract Figure. CF and LI assessment during RF ablation

Choice of Steerable Sheath Impacts Contact Force Stability During Pulmonary Vein Isolation

Purpose: A stable contact force (CF) is correlated with more effective radiofrequency ablation (RFA) lesions and long-term procedural outcomes. Efforts to improve catheter stability include jet ventilation, pacing, steerable sheaths, and CF sensing ablation catheters. This study compares CF stability and effective RF lesions between two commercially available steerable sheaths. Methods: Thirty patients underwent first time RFA at a single center using the Agilis NxT or SureFlex Steerable Sheath. High power short duration RFA was utilized targeting a 10Ω drop. Sheath performance was assessed for the entire procedure and around each pulmonary vein (PV) in terms of mean CF, CF variability, RF time per lesion, and inefficient contact lesions (defined as lesions with CF < 5g for at least 10% of the RF delivery time). Results: Operator-targeted mean CF was achieved using both sheaths; however, overall CF variability was 12.8% lower using the SureFlex sheath (p = 0.08). CF variability was generally 16% greater in the right PVs than the left PVs (p = 0.001), but trended lower with the SureFlex sheath. There were 8% more inefficient contact lesions using Agilis as compared to SureFlex (p = 0.035), especially in the right inferior PV (p = 0.009). RF time per lesion was on average 12% (1.4s) shorter using SureFlex than Agilis (p < 0.05). Conclusion: Choice of steerable sheath may affect catheter stability and potential lesion quality, especially in the right PVs.

Abstract 15503: Biophysical Indicators of Acute Pulmonary Vein Isolation With a Novel Cryoballoon

Introduction: Low nadir temperature (N T ) and long thaw times with cryoballoon ablation are associated with successful PVI. Recently, a cryo-system was designed to improve catheter stability during ablation via a balloon (CB, POLARx™, Boston Scientific) that maintains uniform pressure and size. The purpose of this study was to evaluate whether the CB biophysical parameters, including time to -40 o C (TT40), N T , time to thaw (iTT0), and time to 15 o C (iTT15), are associated with acute PVI success in paroxysmal AF patients. Methods: Ablation was delivered for 180s if isolation was achieved in ≤ 60s or 240s if isolation occurred after 60s. PVI was confirmed via entrance and exit block. Biophysical parameters were evaluated for 3 groups: block with 180s ablation, block with 240s ablation, and for unsuccessful initial treatments (gap veins). The diagnostic accuracy for predicting PVI was assessed using area under (AUC) the receiver operator characteristic (ROC) curve for ablations > 120s. Results: Forty-six consecutive de novo PVI procedures at 4 centers were analyzed (n=234 ablations). All PVs were isolated using the CB alone, with the vast majority within 60s. During freeze, TT40 and N T were significantly shorter and colder for isolated veins compared to gap veins (Table). During thaw, iTT0 and iTT15 were significantly longer for isolated veins compared to gap veins (Table). ROC analysis found iTT15 had the highest diagnostic accuracy for isolation (AUC: 0.85) followed by N T (AUC: 0.81), iTT0 (AUC: 0.77), and TT40 (AUC: 0.72). Optimal cutoff values for iTT15 and N T were 33.5s and -48 o C, which had positive predictive values for acute block of 96.6% and 93.5%. Conclusions: When using the novel CB, ablations reaching < -48 o C and having thaw times to 15 o C > 33.5s were predictive of acute block in PVI, providing guidance toward improved workflow and potential reduction in procedural time.

Abstract 16542: Hypotension and Pericardial Effusion Associated With High Frequency Jet Ventilation

Introduction: High frequency jet ventilation (HFJV) is used to increase catheter stability and improve outcomes during pulmonary vein isolation (PVI) [1,2,4]. In studies, hemodynamic intolerance of HFJV was rare. [1,3]. Hypothesis: HFJV during PVI is well tolerated and vasopressor-resistant hypotension requiring return to conventional ventilation is rare. Methods: Retrospective observational analysis of hemodynamic, blood gas, and echocardiographic data of PVIs performed with HFJV by 2 operators (PT, JW) at our institution between February 2019 and June 2020. Results: Among 193 PVIs, 8 cases (4%) of rapid onset hypotension associated with HFJV were found (Table). In 7 of 8 cases, persistent hypotension and abnormal gas exchange required conversion to conventional ventilation and a new, small pericardial effusion without tamponade was noted just after HFJV initiation. In these cases, initiation of HFJV was associated with a decrease in systolic function. Both the hemodynamic changes and effusion resolved completely within minutes of stopping HFJV. Four of 8 patients were rechallenged with HFJV, and had recurrent hypotension and effusion which resolved immediately after return to conventional ventilation. Conclusions: HFJV-associated rapid onset hypotension, often accompanied by transient pericardial effusion, is more common than previously reported, and resolves with cessation of HFJV. The mechanism of these changes may occur via CO2 levels and warrants further study.

1244Feasibility, safety and efficacy of tailoring ablation index to left atrial wall thickness (lawt) during atrial fibrillation ablation. The Ablate By-LAW Study

Funding Acknowledgements Dr Teres was funded by Swiss Heartrhythm Foundation Introduction Circumferential pulmonary vein isolation (PVI) has become a mainstay in the treatment of atrial fibrillation (AF). The utility of ablation index (AI) to dose radiofrequency delivery for the reduction of AF recurrences has already been proven with a target AI ≥ 400 at the posterior wall and ≥550 at the anterior Wall. Nevertheless, the left atrial wall is a thin, heterogeneous structure with an important inter and intra-patient variability of LAWT. Objective To determine if adapting AI to atrial wall thickness (AWT) is feasible, effective and safe during AF ablation. Methods Single-Center study that included 80 consecutive patients referred for a first paroxysmal AF ablation that was performed with a single catheter approach with the intention to reduce vascular access complication rate. All patients had a MDCT prior to the ablation procedure. LAWT maps were semi-automatically computed from the MDCT as the local distance between the LA endo and epicardium. All procedures were performed under general anesthesia with a high-rate low-volume ventilation protocol for obtaining higher catheter stability. The transeptal puncture was TEE-guided. During the procedure, the WT map was fused with the LA anatomy using CARTO-merge. LAWT was categorized into 1mm-layers and the AI was titrated to the local atrial WT as follows: Thickness &lt; 1 mm (red): 300; 1-2 mm (yellow): 350; 2-3 mm (green): 400; 3-4 mm (blue): 450; &gt; 4 mm (purple): 450 (Figure). Maximal inter-lesion distance was set at 6 mm. VisiTag settings were: catheter position stability: minimum time 3 s, maximum range 4 mm; force over time: 25%, minimum force 3 g; lesion tag size: 3 mm. Respiration training was not possible due to the high catheter stability. The circumferential ablation line was designed in a personalized fashion to avoid thicker regions. Results 80 patients [41 (51,2 %) male, age 60± 11 years] were included. Mean LVEF was 59 ± 5 %, Mean LA diameter 39,1 ± 5,8 mm, Mean LAWT was 1.36 ± 0.63 mm. Mean AI was 352 ± 36 on the RPVs and 356 ± 36 on the LPVs. Procedure time was 60,0 min (IQR 51-70). Fluoroscopy time was 58,5 s (35-97,5). First pass isolation was obtained in 72 (90%) of the RPVs and 75 (93,8%) of the LPVs. Conclusions the present study, assessing a novel, personalized protocol for radiofrequency titration during atrial fibrillation ablation, shows a high rate of first pass isolation with a lower need for RF energy delivery and lower procedure requirements, as compared to previous PV ablation protocols. Further studies are needed to evaluate the long-term results of this approach. Abstract Figure. LAWT-map Visitag points with tailored AI