Prospective use of Ablation Index targets improves clinical outcomes following ablation for atrial fibrillation

Ablation-index guided versus conventional contact-force guided ablation in pulmonary vein isolation - Systematic review and meta-analysis

Background

Contact-force sensing catheter is widely used for catheter ablation, however, it did not take account of radiofrequency power. Ablation index (AI) is a novel marker incorporating contact force-time-power, was shown to be reliable in predicting lesion size and depth for radiofrequency delivery. We aimed to assess the latest evidence on ablation index guided procedure versus conventional ablation procedure.

Methods

We performed a comprehensive search on topic that assesses ablation index guided procedure versus conventional procedures from inception up until February 2019 through PubMed, EuropePMC, EBSCOhost, Cochrane Central Database, and ClinicalTrials.gov.

Results

A total of 1727 subjects from five studies were included. 12 months’ incidence of AF/AT/AFL was lower in ablation index guided with an OR of 0.35 [0.17, 0.73], p = 0.005; I² 58%. Upon sensitivity analysis by removing a study, heterogeneity decreased to 0% with OR of 0.26 [0.15, 0.46], p < 0.001. First-pass isolation has a pooled OR of 11.29 [4.68, 27.20], p < 0.001; I² 58%. Pooled OR for acute pulmonary vein reconnection was 0.43 [0.29, 0.64], p < 0.001; I² 46%. AI group has a shorter fluoroscopy time of MD -1.62 [-2.62, −0.62] minutes, p = 0.001; I² 51% and total ablation time MD -9.96 [-17.16, −2.76] minutes, p < 0.001; I² 95%. Total procedural time and complication rate were similar.

Conclusion

Ablation index guided procedure resulted in a significantly lower incidence of AF/AT/AFL, shorter fluoroscopy time, and total ablation time. First-pass isolation was higher in AI group and acute PVR was lower in AI group. Ablation-index guided procedure has a similar safety profile to conventional ablation.

The modified ablation index: a novel determinant of acute pulmonary vein reconnections after pulmonary vein isolation

BACKGROUND

Although pulmonary vein isolation (PVI) guided by the ablation index (AI) has been well-developed, acute PV reconnections (PVRs) still occur. This study aimed to compare the prognostic performance of the modified AI and its optimal cut-off value for the prediction of acute PVRs to ensure durable PVI.

METHODS

Three-dimensional left atrium (LA) voltage maps created before an extensive encircling PVI in 64 patients with atrial fibrillation (AF) (45 men, 62 ± 10 years) were examined for an association between electrogram voltage amplitude recorded from the PV-LA junction and acute post-PVI PVRs (spontaneous PVRs and/or ATP-provoked dormant PV conduction).

RESULTS

Acute PVRs were observed in 22 patients (34%) and 33 (3%) of the 1012 PV segments. Acute PVRs were significantly associated with segments with higher bipolar voltage zones (3.23 ± 1.17 vs. 1.97 ± 1.20 mV, P < 0.0001), lower mean AI values (449 [428-450] vs. 460 [437-486], P = 0.05), and radiofrequency lesion gaps ≥ 6 mm (48 vs. 32%, P = 0.04), but not with contact force, force-time integral, or power. We created the modified AI calculated as AI/LA bipolar voltage, and found it to be significantly lower in areas with acute PVRs than in those without (152 [109-185] vs. 256 [176-413] AU/mV, P < 0.0001). Univariate analysis showed the prognostic performance of the modified AI, with an area under the curve of 0.801 (0.775-0.825), to be the highest of all the significant parameters.

CONCLUSIONS

Low values of the novel modified AI on the PV-encircling ablation line were strongly associated with acute PVRs.

Gains in Paroxysmal Atrial Fibrillation Ablation Using a Standardized Workflow to Optimize Contact Force Technologies

Background

Catheter ablation technology has evolved rapidly in recent years. There is a need to understand the impact of these advances on efficiency, safety, and effectiveness in real-world populations. The objective of this study was to evaluate a standardized workflow that integrates a contact force (CF) catheter and stability module in an attempt to optimize efficiency and clinical outcomes of paroxysmal atrial fibrillation (PAF) ablation, and to compare the outcomes of this workflow with existing ablation technologies at a high-volume center.

Methods

Consecutive ablations for PAF from July 2013 - June 2016 were included. Radiofrequency (RF) ablations were performed with the ThermocoolSF Catheter (SF) through April 2014, after which a change was made to the ThermocoolSmarttouchCatheter (ST)with a standardized workflow. Cryoballoon ablations (CA) were performed with theArctic FrontAdvancebetween July 2013 and March 2016. Systematic collection of 12-month effectiveness data began in July 2014. Prior to that time, only acute outcomes and reablations were captured.

Results

Procedural data for 32 SF, 232 ST, and 59 CA procedures for PAF were available. Mean procedure times were similar across SF and CA, and moderately shorter with ST (p=0.0201). Fluoroscopy times were substantially reduced with ST (p<0.0001). Complication rates were low and similar across all cohorts (p=0.4744), whereas reablation rates were lowest in the ST cohort (p=0.0194).

Conclusions

PAF ablation using integrated CF and catheter stability technology with a systematic ablation workflow maylead to improvements in both procedural efficiency and reablation rates, without compromising patient safety.

Lesion index: a novel guide in the path of successful pulmonary vein isolation

PURPOSE

Previous studies indicate force time integral (FTI) as a radiofrequency (RF) lesion quality marker, while not considering power supply. Tacticath™ Quartz catheter provides Lesion index (LSI), a lesion quality marker derived by contact force (CF), power supply, and RF time combined. Our aim is to assess LSI and FTI correlation and a LSI-related cutoff of atrial fibrillation (AF) recurrences 12 months after pulmonary vein isolation (PVI).

METHODS

We retrospectively enrolled 37 patients who underwent RF ablation using Tacticath™ Quartz catheter. AF recurrence rate was evaluated 3, 6, and 12 months after PVI procedure.

RESULTS

AF recurrence was detected in 32% of patients. FTI mean value was significantly lower in left superior pulmonary vein (LSPV: 256 ± 86 gs vs 329 ± 117 gs, p = 0.05) and right inferior pulmonary vein (RIPV: 253 ± 128 gs vs 394 ± 123 gs p = 0.006) in patients with AF recurrences; no significant differences were found in right superior pulmonary vein (RSPV) and left inferior pulmonary vein (LIPV). LSI instead was significantly higher for all veins in patients without AF recurrences: LSPV (5.2 ± 0.7 vs 4.6 ± 0.8, p = 0.03), LIPV (5.0 ± 0.8 vs 4.5 ± 0.6, p = 0.04), RSPV (5.5 ± 0.6 vs 5.1 ± 0.6, p = 0.05), and RIPV (5.5 ± 0.7 vs 4.7 ± 0.8, p = 0.006). Receiver operator characteristic curve suggests 5.3 as LSI overall cutoff value predicting freedom from disease at 1-year follow-up.

CONCLUSIONS

Our preliminary data suggest that a LSI mean value higher than 5.3 can be considered a good predictor of AF freedom at 1-year follow-up.

Ablation Index for Catheter Ablation of Atrial Fibrillation - Clinical Applicability and Comparison With Force-Time Integral

BACKGROUND

Key determinants for lesion formation in catheter ablation are contact force, radiofrequency (RF) power and time. The aim of this study was to evaluate the clinical applicability of ablation index (AI), a novel non-linear formula based on these components, and to compare AI with the conventional linear force-time interval (FTI) in pulmonary vein isolation (PVI). Methods and Results: Target AI ranges were defined for anatomical segments of the ipsilateral pulmonary veins. The operator was blinded to AI during PVI for the initial 11 patients (group A), and was unblinded for the remaining 23 patients (group B). We assessed (1) the clinical value of AI to avoid excessively high and low values with an operator blinded vs. non-blinded to AI; and (2) the relation of AI and FTI in predefined ranges. In group A, 235/564 lesions (41.7%) were in the predefined target range as compared with 1,171/1,412 lesions (82.9%) in group B (P<0.001). A given AI may correspond to a wide range of FTI, as reflected by a quartile coefficient of dispersion for AI of 0.11 vs. a quartile coefficient of dispersion for FTI of 0.36.

CONCLUSIONS

Incorporating RF current power, the non-linear AI provides more comprehensive information during PVI compared with FTI. Given that the FTI for a given AI varies widely, the value of FTI in clinical practice is questionable.

3D Mapping for PVI- Geometry, Image Integration and Incorporation of Contact Force Into Work Flow

Catheter ablation of atrial fibrillation has evolved enormously thanks to rapid improvement of modern mapping technologies, progress in catheter development and current possibilities for reduction of radiation exposure. Pulmonary vein isolation is thereby the cornerstone in this interventional treatment. Increased precision of catheter localization by modern three-dimensional mapping systems, faster and better processing of local electrograms and their immediate color-based visualization make it possible to treat even challenging arrhythmias very effectively. The commonly used three-dimensional mapping systems CARTO 3 (Biosense Webster, Irvine, Ca.) and Ensite Precision (St. Jude Medical, St. Paul, Min) differ in construction and principles of the underlying mapping technology. In this review article, we aim to emphasize the most important aspects of possibilities that make both systems so valuable for interventional treatment of atrial fibrillation. We present a modern workflow, that unites three-dimensional LA mapping with collecting relevant local information, image integration for refining the map and beneficial use of contact force based ablation approach.

Lesion modeling, characterization, and visualization for image-guided cardiac ablation therapy monitoring

In spite of significant efforts to improve image-guided ablation therapy, a large number of patients undergoing ablation therapy to treat cardiac arrhythmic conditions require repeat procedures. The delivery of insufficient thermal dose is a significant contributor to incomplete tissue ablation, in turn leading to the arrhythmia recurrence. Ongoing research efforts aim to better characterize and visualize RF delivery to monitor the induced tissue damage during therapy. Here, we propose a method that entails modeling and visualization of the lesions in real-time. The described image-based ablation model relies on classical heat transfer principles to estimate tissue temperature in response to the ablation parameters, tissue properties, and duration. The ablation lesion quality, geometry, and overall progression are quantified on a voxel-by-voxel basis according to each voxel's cumulative temperature and time exposure. The model was evaluated both numerically under different parameter conditions, as well as experimentally, using ex vivo bovine tissue samples undergoing ex vivo clinically relevant ablation protocols. The studies demonstrated less than 5°C difference between the model-predicted and experimentally measured end-ablation temperatures. The model predicted lesion patterns were within 0.5 to 1 mm from the observed lesion patterns, suggesting sufficiently accurate modeling of the ablation lesions. Lastly, our proposed method enables therapy delivery feedback with no significant workflow latency. This study suggests that the proposed technique provides reasonably accurate and sufficiently fast visualizations of the delivered ablation lesions.

Safety and feasibility of atrial fibrillation ablation using Amigo® system versus manual approach: A pilot study

BACKGROUND

The Amigo® Remote Catheter System is a relatively new robotic system for catheter navigation. This study compared feasibility and safety using Amigo (RCM) versus manual catheter manipulation (MCM) to treat paroxysmal atrial fibrillation (PAF). Contact force (CF) and force-time integral (FTI) values obtained during pulmonary vein isolation (PVI) ablation were compared.

METHODS

Forty patients were randomly selected for either RCM (20) or MCM (20). All were studied with the Thermocool® SmartTouch® force-sensing catheter (STc). Contact Force (CF), Force Time Integral (FTI) and procedure-related data, were measured/stored in the CARTO®3.

RESULTS

All cases achieved complete PVI without major complications. Mean CF was significantly higher in the RCM group (13.3 ± 7.7 g in RCM vs. 12.04 ± 7.42 g in MCM p < 0.001), as was overall mean FTI (425.6 gs ± 199.6 gs with RCM and 407.5 gs ± 288.0 gs in MCM (p = 0.007) and was more likely to fall into the optimal FTI range (400-1000) using RCM (66.1% versus 49.1%, p < 0.001). FTI was significantly more likely to fall within the optimal range in each PV, as was CF within its optimal range in the right PVs, but trended higher in the left PVs. Freedom from atrial tachyarrhythmia was 90.0% for the RCM and 70.0% for the MCM group (p = 0,12) at 540 days follow-up.

CONCLUSIONS

This pilot study suggests that use of the Amigo RCM system, with STc catheter, seems to be safe and effective for PVI ablation in paroxysmal AF patients. A not statistically significant favorable trend was observed for RCM in term of AF-free survival.

Technical Note: On Cardiac Ablation Lesion Visualization for Image-guided Therapy Monitoring

The delivery of insufficient thermal dose is a significant contributor to incomplete tissue ablation and leads to arrhythmia recurrence and a large number of patients requiring repeat procedures. In concert with ongoing research efforts aimed at better characterizing the RF energy delivery, here we propose a method that entails modeling and visualization of the lesions in real time. The described image-based ablation model relies on classical heat transfer principles to estimate tissue temperature in response to the ablation parameters, tissue properties, and duration. The ablation lesion quality, geometry, and overall progression is quantified on a voxel-by-voxel basis according to each voxel's cumulative temperature and time exposure. The model was evaluated both numerically under different parameter conditions, as well as experimentally, using ex vivo bovine tissue samples. This study suggests that the proposed technique provides reasonably accurate and sufficiently fast visualizations of the delivered ablation lesions.

Strategy and Outcome of Catheter Ablation for Persistent Atrial Fibrillation - Impact of Progress in the Mapping and Ablation Technologies

Pulmonary vein (PV) antrum isolation (PVAI) is effective in treating paroxysmal atrial fibrillation (AF) but is less so for persistent AF. A recent randomized study on the ablation strategies for persistent AF demonstrated that 2 common atrial substrate modifications, creation of linear lesions in the left atrium and ablation of complex fractionated electrogram sites, in addition to PVAI did not improve the outcome compared with stand-alone PVAI, suggesting the necessity of a more individualized, selective approach to persistent AF. There are emerging technologies, including high-resolution mapping with the use of multi-electrode catheter and auto mapping system and contact force (CF) guide ablation; the former allows rapid and accurate confirmation of the completeness of PVAI, and the latter enhances the achievement of durable ablation lesions more securely. Ablation for fibrotic area(s) has been proposed as a new approach for substrate modification, and high-resolution mapping is useful to define the area with low-voltage electrograms, a surrogate marker for atrial fibrosis. Ablation for non-PV triggers in addition to PVAI improves the outcome of persistent AF. Further, durable isolation of the left atrial posterior wall may reduce AF recurrence. These ablation strategies with concomitant use of the emerging technologies are strongly expected to enhance the effectiveness of catheter ablation for persistent AF.