Prevention of cerebral thromboembolism by oral anticoagulation with dabigatran after pulmonary vein isolation for atrial fibrillation: the ODIn-AF trial

BACKGROUND AND OBJECTIVES

Long-term oral anticoagulation (OAC) following successful catheter ablation of atrial fibrillation (AF) remains controversial. Prospective data are missing. The ODIn-AF study aimed to evaluate the effect of OAC on the incidence of silent cerebral embolic events and clinically relevant cardioembolic events in patients at intermediate to high risk for embolic events, free from AF after pulmonary vein isolation (PVI).

METHODS

This prospective, randomized, multicenter, open-label, blinded endpoint interventional trial enrolled patients who were scheduled for PVI to treat paroxysmal or persistent AF. Six months after PVI, AF-free patients were randomized to receive either continued OAC with dabigatran or no OAC. The primary endpoint was the incidence of new silent micro- and macro-embolic lesions detected on brain MRI at 12 months of follow-up compared to baseline. Safety analysis included bleedings, clinically evident cardioembolic, and serious adverse events (SAE).

RESULTS

Between 2015 and 2021, 200 patients were randomized into 2 study arms (on OAC: n = 99, off OAC: n = 101). There was no significant difference in the occurrence of new cerebral microlesions between the on OAC and off OAC arm [2 (2%) versus 0 (0%); P = 0.1517] after 12 months. MRI showed no new macro-embolic lesion, no clinical apparent strokes were present in both groups. SAE were more frequent in the OAC arm [on OAC n = 34 (31.8%), off OAC n = 18 (19.4%); P = 0.0460]; bleedings did not differ.

CONCLUSION

Discontinuation of OAC after successful PVI was not found to be associated with an elevated risk of cerebral embolic events compared with continued OAC after a follow-up of 12 months.

Recommender system for ablation lines to treat complex atrial tachycardia

BACKGROUND AND OBJECTIVE

Planning the optimal ablation strategy for the treatment of complex atrial tachycardia (CAT) is a time consuming task and is error-prone. Recently, directed network mapping, a technology based on graph theory, proved to efficiently identify CAT based solely on data of clinical interventions. Briefly, a directed network was used to model the atrial electrical propagation and reentrant activities were identified by looking for closed-loop paths in the network. In this study, we propose a recommender system, built as an optimization problem, able to suggest the optimal ablation strategy for the treatment of CAT.

METHODS

The optimization problem modeled the optimal ablation strategy as that one interrupting all reentrant mechanisms while minimizing the ablated atrial surface. The problem was designed on top of directed network mapping. Considering the exponential complexity of finding the optimal solution of the problem, we introduced a heuristic algorithm with polynomial complexity. The proposed algorithm was applied to the data of i) 6 simulated scenarios including both left and right atrial flutter; and ii) 10 subjects that underwent a clinical routine.

RESULTS

The recommender system suggested the optimal strategy in 4 out of 6 simulated scenarios. On clinical data, the recommended ablation lines were found satisfactory on 67% of the cases according to the clinician's opinion, while they were correctly located in 89%. The algorithm made use of only data collected during mapping and was able to process them nearly real-time.

CONCLUSIONS

The first recommender system for the identification of the optimal ablation lines for CAT, based solely on the data collected during the intervention, is presented. The study may open up interesting scenarios for the application of graph theory for the treatment of CAT.

Acute procedural efficacy and safety of a novel cryoballoon for the treatment of paroxysmal atrial fibrillation: Results from the POLAR ICE study

INTRODUCTION

Pulmonary vein isolation (PVI) is well established as a primary treatment for atrial fibrillation (AF). The POLAR ICE study was designed to collect prospective real world data on the safety and effectiveness of the POLARx^TM cryoballoon for PVI to treat paroxysmal AF.

METHODS

POLAR ICE, a prospective, non-randomized, multicenter (international) registry (NCT04250714), enrolled 399 patients across 19 European centers. Procedural characteristics, such as time to isolation, cryoablations per pulmonary vein (PV), balloon nadir temperature, and occlusion grade were recorded. PVI was confirmed with entrance block testing.

RESULTS

Data on 372 de novo PVI procedures (n = 2190 ablations) were collected. Complete PVI was achieved in 96.8% of PVs. Procedure and fluoroscopy times were 68.2 ± 24.6 and 15.6 ± 9.6 min, respectively. Left atrial dwell time was 46.6 ± 18.3 min. Grade 3 or 4 occlusion was achieved in 98.2% of PVs reported and 71.2% of PVs isolation required only a single cryoablation. Of 2190 cryoapplications, 83% had a duration of at least 120 s; nadir temperature of these ablations averaged -56.3 ± 6.5°C. There were 6 phrenic nerve palsy events, 2 of which resolved within 3 months of the procedure.

CONCLUSION

This real-world usage data on a novel cryoballoon suggests this device is effective, safe, and relatively fast in centers with cryoballoon experience. These data are comparable to prior POLARx reports and in keeping with reported data on other cryoballoons. Future studies should examine the long-term outcomes and the relationship between biophysical parameters and outcomes for this novel cryoballoon.

In Silico Study of Local Electrical Impedance Measurements in the Atria - Towards Understanding and Quantifying Dependencies in Human

BACKGROUND

Electrical impedance measurements have become an accepted tool for monitoring intracardiac radio frequency ablation. Recently, the long-established generator impedance was joined by novel local impedance measurement capabilities with all electrical circuit terminals being accommodated within the catheter.

OBJECTIVE

This work aims at in silico quantification of distinct influencing factors that have remained challenges due to the lack of ground truth knowledge and the superposition of effects in clinical settings.

METHODS

We introduced a highly detailed in silico model of two local impedance enabled catheters, namely IntellaNav MiFi™ OI and IntellaNav Stablepoint™, embedded in a series of clinically relevant environments. Assigning material and frequency specific conductivities and subsequently calculating the spread of the electrical field with the finite element method yielded in silico local impedances. The in silico model was validated by comparison to in vitro measurements of standardized sodium chloride solutions. We then investigated the effect of the withdrawal of the catheter into the transseptal sheath, catheter-tissue interaction, insertion of the catheter into pulmonary veins, and catheter irrigation.

RESULTS

All simulated setups were in line with in vitro experiments and in human measurements and gave detailed insight into determinants of local impedance changes as well as the relation between values measured with two different devices.

CONCLUSION

The in silico environment proved to be capable of resembling clinical scenarios and quantifying local impedance changes.

SIGNIFICANCE

The tool can assists the interpretation of measurements in humans and has the potential to support future catheter development.

Bipolar ablation of therapy-refractory ventricular arrhythmias: application of a dedicated approach

AIMS

Bipolar radiofrequency ablation (B-RFA) has been reported as a bail-out strategy for the treatment of therapy refractory ventricular arrhythmias (VA). Currently, existing setups have not been standardized for B-RFA, while the impact of conventional B-RFA approaches on lesion formation remains unclear.

METHODS AND RESULTS

(i) In a multicentre observational study, patients undergoing B-RFA for previously therapy-refractory VA using a dedicated B-RFA setup were retrospectively analysed. (ii) Additionally, in an ex vivo model lesion formation during B-RFA was evaluated using porcine hearts. In a total of 26 procedures (24 patients), acute success was achieved in all 14 ventricular tachycardia (VT) procedures and 7/12 procedures with premature ventricular contractions (PVC), with major complications occurring in 1 procedure (atrioventricular block). During a median follow-up of 211 days in 21 patients, 6/11 patients (VT) and 5/10 patients (PVC) remained arrhythmia-free. Lesion formation in the ex vivo model during energy titration from 30 to 50 W led to similar lesion volumes compared with initial high-power 50 W B-RFA. Lesion size significantly increased when combining sequential unipolar and B-RFA (1429 mm3 vs. titration 501 mm3 vs. B-RFA 50 W 423 mm3, P < 0.001), an approach used in overall 58% of procedures and more frequently applied in procedures without VA recurrence (92% vs. 36%, P = 0.009). Adipose tissue severely limited lesion formation during B-RFA.

CONCLUSION

Using a dedicated device for B-RFA for therapy-refractory VA appears feasible and safe. While some patients need repeat ablation, success rates were encouraging. Sequential unipolar and B-RFA may be favourable for lesion formation.

Impact of contact force on local impedance measurements in different atrial locations

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860974

Regions with pathologically altered substrate have been identified as potentially responsible for atrial fibrillation and atrial flutter maintenance. Also, real time feedback on lesion formation especially in those critical areas is a challenge. The LOCALIZE trial has shown significant value of the usage of the local impedance (LI) drop as a real time indicator during ablation for durable lesion formation. In these procedures, a decrease of 10-20% of the initial LI value is used as a marker of successful ablation. Also known is the fact that low electrode-tissue contact force is associated with ineffective lesion formation, whereas a high value can lead to an increased risk of steam pop. The IntellaNavSTABLEPOINT catheter offers both, LI and contact force, as a novel combined technique to characterize the process of lesion formation. Additionally, LI values are expected to distinguish between healthy and scar tissue independently from the atrial rhythm, which can improve the understanding of underlying substrate, even more, when corrected for an eventual lack of contact by combining it with contact force.

This study aims to: (1) evaluate the relationship between contact force and LI; (2) characterise the contact force during local impedance mapping depending on the wall region of the left atrium (LA).

Patients undergoing LA ablation with the STABLEPOINT catheter were included in this analysis. Contact force and LI data were recorded in four different healthy anatomical points in the LA, two in the anterior wall, and two in the posterior wall, using manually controlled contact force values between 0 g and the saturation point (70 g). When possible, additional points in scar regions were recorded. Data were exported and processed to correlate each LI measurement with the corresponding contact force. Due to the susceptibility of raw LI recordings to oscillations, moving average approach was considered. The clinical cohort comprised ten patients with a mean age of 61 years, one female. De-Novo ablations as well as redo procedures were included. Measurements at different contact force values yielded a non-linear relationship between contact force and LI. Median value of the difference between the moving average LI measurement and the LI bloodpool value were calculated at the anterior and posterior walls of the LA at contact force values from 5 to 40 g (5 g step size). Comparing the LI values at each segment, measurements differ significantly (Mann-Whitney U-test for unpaired samples) between the anterior and the posterior wall of the LA, with an ascending trend. Scar points showed a globally lower curve.

Results from this preliminary study showed that LI and contact force are non-linearly dependent and it differs between anterior and posterior atrial walls, as well as between healthy and pathological substrate. Further investigations in a larger clinical cohort will analyse the LI variability to set an optimal contact force technique during LI mapping.

Biophysical parameters and time to isolation of pulmonary veins with a novel cryoballoon: results of POLAR ICE study

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Boston Scientific

Introduction

Low nadir temperatures and long thaw times with cryoballoon ablation are associated with successful pulmonary vein isolation (PVI). Recently, a system that maintains uniform pressure and size has been introduced to improve catheter stability during cryoballoon ablation. The present results examine the relationship between cryoballoon time to isolation (TTI) and other biophysical parameters; time to -40ºC (TT-40), nadir temperature, time to thaw (TT0), and first pass isolation success in patients with paroxysmal AF (PAF).

Methods

POLAR ICE, a prospective, non-randomized, multicenter (international) registry (NCT04250714), enrolled 400 patients across 19 centers, between Aug 2020 and May 2021. This study included any patients indicated for treatment of PAF with the POLARx cryoablation system. Cryodosing regimen was left to the operator and not specified by study protocol. Procedural characteristics, such as time to isolation (TTI), cryoablations per pulmonary vein, nadir temperature, and occlusion grade were recorded. PVI was confirmed via entrance block. Biophysical parameters for ablations longer than 120s were evaluated.

Results

Data on 389 PVI procedures (n=2303 ablations) were collected. Of those ablations, 1914 (83%) had a duration of at least 120s and were included in this analysis. Isolation was attempted using the CB alone. TTI was reported in 1335 ablations with the majority (64%) occurring within 60s. Biophysical parameters and single shot success rates were examined based on TTI. Ablations with TTI&lt;60s had significantly faster TT-40 (30.6±7.4s), lower nadir temperatures (-58.3±5.8ºC), longer thaw times (21.1±6.7s), and a greater proportion of grade 4 occlusions (88%) than longer TTIs or ablation with no TTI reported (Table 1). In TTIs&lt;60s single shot success was 95%, significantly greater than TT≥60s, or No TTI. Procedure-related complications included: phrenic nerve palsy (0.5%), tamponade (0.5%), AV block (0.3%), stroke (0.3%), and transient ischemic attack (0.3%).

Conclusions

These data suggest a correlation between cryoballoon biophysical parameters and single shot success. Good occlusion likely drives faster freeze and lower nadir temperatures, resulting in longer thaw times with this novel cryoballoon. Future research should examine the relationship between these parameters to drive optimization of cryoablation techniques and provide guidance toward improved workflow.

Acute procedural characteristics, efficacy, and safety of a novel cryoballoon for the treatment of paroxysmal atrial fibrillation: Results from the POLAR-ICE study

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Boston Scientific

Background/Introduction

Pulmonary vein isolation (PVI) using a cryoballoon is well-established for the treatment of paroxysmal atrial fibrillation (PAF). Initial experience with a novel cryoballoon (CB) with a stable low balloon pressure (POLARx, Boston Scientific) has demonstrated acute procedural safety and efficacy in de novo PVI procedures in patients with paroxysmal AF. However, to date, there is limited multicenter data on real world acute outcomes and procedural characteristics with this novel cryoballoon.

Purpose

The purpose of POLAR ICE was to provide real-world data on the acute and chronic outcomes of cryoballoon ablation with POLARx for the treatment of PAF. Here we report on the initial acute outcomes up to 3 months including procedural efficacy, safety, and biophysical parameters.

Methods

POLAR ICE, a prospective, non-randomized, multicenter (international) registry (NCT04250714), enrolled 400 patients across 19 centers, between Aug 2020 and May 2021. This study included any patients indicated for treatment of PAF with the POLARx cryoablation system. The study protocol did not mandate any specific cryodosing regimen, this was left to the operator. Procedural characteristics, such as time to isolation (TTI), cryoablations per pulmonary vein, balloon nadir temperature, and occlusion grade were recorded. PVI was confirmed with entrance block testing.

Results

Complete PVI was achieved in 96.1% of PVs (1437/1496). Procedure and fluoroscopy times were 69.0±25.2 min and 15.8±10.0 min, respectively. Left atrial dwell time was 47.3±18.8 min. The cryoablation characteristics by vein are shown in the Table 1. An average of 4.9±1.8 ablations were performed per patient (1.3±0.7 per vein). Grade 3 or 4 occlusion was achieved in 98.1% of PVs reported. Electrical isolation was achieved with an average TTI of 50±33.8s and in 81.4% of PVs isolation required only a single cryoablation. Nadir temperatures across all pulmonary veins averaged -56.3± 6.5C. Time to -40C was 32.9±11s and Time to Thaw (0C) was 19.5±6.7s across all veins. PVI was performed on atypical anatomies (12 LCPV, 7 RMPV, & 3 RCPV) in 19 pts. Serious adverse events included phrenic nerve palsy (0.5%), tamponade (0.5%), AV block (0.3%), stroke (0.3%), and transient ischemic attack (0.3%).

Conclusions

Real world usage data on the novel CB suggests that this device is safe and effective, with a PV isolation success rate of 96.2% and 81.4% of PVs isolated with a single cryoablation. These data are in keeping with reports on other cryoballon systems and have markedly shorter procedure times than have been previously reported on this cryoballon.

Ablation of Left Atrial Tachycardia following Catheter Ablation of Atrial Fibrillation: 12-Month Success Rates

The treatment of atrial tachycardia following catheter ablation of atrial fibrillation is often challenging. Electrophysiological studies using high-resolution 3D mapping systems have contributed significantly to their understanding, and new ablation approaches have shown high rates of acute terminations with low recurrences for the clinical AT. However, patient populations are very heterogeneous, and long-term data of the freedom from any atrial tachycardia or any arrhythmia are still sparse. To evaluate long-term success, a unified patient population and predefined ablation strategies are preferred. In this study, we present 12-month success and mean 30 month follow-up data of catheter ablation of left atrial tachycardia. All 35 patients had a history of pulmonary vein isolation (PVI), 71% of which had a previous substrate modification. A total of 54 ATs, with a mean cycle length 297 ± 86 ms, 31 macro-reentries, and 4 localized reentries, were targeted. The ablation strategy to be used was given by the study protocol, depending on the type of reentry and the number of critical isthmuses. All available ablation strategies were included: standard (anatomical) lines, individual lines, critical isthmuses, and focal ablation. All ATs were terminated by ablation. A total of 91% terminated upon the first ablation strategy. Freedom from any AT after 12 months was 82%, and from any arrhythmia, it was 77%. The multi-procedure success after 30 months was 65% for any AT and 55% for any arrhythmia. In conclusion, individual ablation strategies based on the reentry mechanism and the number of critical isthmuses seems promising and demonstrates a high long-term clinical success. Tachycardia comprising a single critical isthmus can be ablated by critical isthmus ablation only. These patients present with the highest 12-month and long-term success rates.

Local Electrical Impedance Mapping of the Atria: Conclusions on Substrate Properties and Confounding Factors

The treatment of atrial fibrillation and other cardiac arrhythmias as a major cause of cardiovascular hospitalization has remained a challenge predominantly for patients with severely remodeled substrate. Individualized ablation strategies are extremely important both for pulmonary vein isolation and subsequent ablations. Current approaches to identifying arrhythmogenic regions rely on electrogram-based features such as activation time and voltage. Novel technologies now enable clinical assessment of the local impedance as tissue property. Previous studies demonstrated its use for ablation monitoring and indicated its potential to differentiate healthy substrate, scar, and pathological tissue. This study investigates the potential of local electrical impedance-based substrate mapping of the atria for human in-vivo data. The presented pipeline for impedance mapping particularly contains options for dealing with undesirable effects originating from cardiac motion, catheter motion, or proximity to other intracardiac devices. Bloodpool impedance was automatically determined as a patient-specific reference. Full-chamber, left atrial impedance maps were drawn up from interpolating the measured impedances to the atrial endocardium. Finally, the origin and magnitude of oscillations of the raw impedance recording were probed into. The most dominant reason for exclusion of impedance samples was the loss of endocardial contact. With median elevations above the bloodpool impedance between 29 and 46 Ω, the impedance within the pulmonary veins significantly exceeded the remaining atrial walls presenting median elevations above the bloodpool impedance between 16 and 20 Ω. Previous ablation lesions were distinguished from their surroundings by a significant drop in local impedance while the corresponding regions did not differ for the control group. The raw impedance was found to oscillate with median amplitudes between 6 and 17 Ω depending on the patient. Oscillations were traced back to an interplay of atrial, ventricular, and respiratory motion. In summary, local impedance measurements demonstrated their capability to distinguish pathological atrial tissue from physiological substrate. Methods to limit the influence of confounding factors that still hinder impedance mapping were presented. Measurements at different frequencies or the combination of multiple electrodes could lead to further improvement. The presented examples indicate that electrogram- and impedance-based substrate mapping have the potential to complement each other toward better patient outcomes in future.

Hybrid machine learning to localize atrial flutter substrates using the surface 12-lead electrocardiogram

Aims

Atrial flutter (AFlut) is a common re-entrant atrial tachycardia driven by self-sustainable mechanisms that cause excitations to propagate along pathways different from sinus rhythm. Intra-cardiac electrophysiological mapping and catheter ablation are often performed without detailed prior knowledge of the mechanism perpetuating AFlut, likely prolonging the procedure time of these invasive interventions. We sought to discriminate the AFlut location [cavotricuspid isthmus-dependent (CTI), peri-mitral, and other left atrium (LA) AFlut classes] with a machine learning-based algorithm using only the non-invasive signals from the 12-lead electrocardiogram (ECG).

Methods and results

Hybrid 12-lead ECG dataset of 1769 signals was used (1424 in silico ECGs, and 345 clinical ECGs from 115 patients—three different ECG segments over time were extracted from each patient corresponding to single AFlut cycles). Seventy-seven features were extracted. A decision tree classifier with a hold-out classification approach was trained, validated, and tested on the dataset randomly split after selecting the most informative features. The clinical test set comprised 38 patients (114 clinical ECGs). The classifier yielded 76.3% accuracy on the clinical test set with a sensitivity of 89.7%, 75.0%, and 64.1% and a positive predictive value of 71.4%, 75.0%, and 86.2% for CTI, peri-mitral, and other LA class, respectively. Considering majority vote of the three segments taken from each patient, the CTI class was correctly classified at 92%.

Conclusion

Our results show that a machine learning classifier relying only on non-invasive signals can potentially identify the location of AFlut mechanisms. This method could aid in planning and tailoring patient-specific AFlut treatments.

Atrial Flutter Mechanism Detection Using Directed Network Mapping

Atrial flutter (AFL) is a common atrial arrhythmia typically characterized by electrical activity propagating around specific anatomical regions. It is usually treated with catheter ablation. However, the identification of rotational activities is not straightforward, and requires an intense effort during the first phase of the electrophysiological (EP) study, i.e., the mapping phase, in which an anatomical 3D model is built and electrograms (EGMs) are recorded. In this study, we modeled the electrical propagation pattern of AFL (measured during mapping) using network theory (NT), a well-known field of research from the computer science domain. The main advantage of NT is the large number of available algorithms that can efficiently analyze the network. Using directed network mapping, we employed a cycle-finding algorithm to detect all cycles in the network, resembling the main propagation pattern of AFL. The method was tested on two subjects in sinus rhythm, six in an experimental model of in-silico simulations, and 10 subjects diagnosed with AFL who underwent a catheter ablation. The algorithm correctly detected the electrical propagation of both sinus rhythm cases and in-silico simulations. Regarding the AFL cases, arrhythmia mechanisms were either totally or partially identified in most of the cases (8 out of 10), i.e., cycles around the mitral valve, tricuspid valve and figure-of-eight reentries. The other two cases presented a poor mapping quality or a major complexity related to previous ablations, large areas of fibrotic tissue, etc. Directed network mapping represents an innovative tool that showed promising results in identifying AFL mechanisms in an automatic fashion. Further investigations are needed to assess the reliability of the method in different clinical scenarios.

Quantitative assessment of ventricular far field removal techniques for clinical unipolar electrograms

The incidence of atrial tachycardia steadily increases in industrial nations. During invasive electrophysiological studies, a catheter measures electrograms within the atrium to assist detailed diagnosis and treatment planning. With unipolar and bipolar electrograms, two different acquisition modes are clinically available. Unipolar electrograms have several advantages over bipolar electrograms. However, unipolar electrograms are more affected by noise and the ventricular far field. Therefore, only bipolar electrograms are typically used in clinical settings. A recently published ventricular far field removal technique models the ventricular far field by a set of dipoles and yielded promising results in a simulation study. However, the method lacks quantitative clinical validation. Therefore, we adapted the technique to clinical needs and applied it to data sets of two patients using four different lengths of the removal window. Results were compared quantitatively by a tailored residual error measure. The used method resulted in a median reduction of the ventricular far field by approximately 89% using a removal window of optimal length for both patients. The results showed that the dipole method provides an alternative to other VFF removal techniques in clinical practice because it can reveal AA originally hidden by VFF without leading to a prolongation of the electrophysiological study.

Cycle length statistics during human atrial fibrillation reveal refractory properties of the underlying substrate: a combined in silico and clinical test of concept study

AIMS

The treatment of atrial fibrillation beyond pulmonary vein isolation has remained an unsolved challenge. Targeting regions identified by different substrate mapping approaches for ablation resulted in ambiguous outcomes. With the effective refractory period being a fundamental prerequisite for the maintenance of fibrillatory conduction, this study aims at estimating the effective refractory period with clinically available measurements.

METHODS AND RESULTS

A set of 240 simulations in a spherical model of the left atrium with varying model initialization, combination of cellular refractory properties, and size of a region of lowered effective refractory period was implemented to analyse the capabilities and limitations of cycle length mapping. The minimum observed cycle length and the 25% quantile were compared to the underlying effective refractory period. The density of phase singularities was used as a measure for the complexity of the excitation pattern. Finally, we employed the method in a clinical test of concept including five patients. Areas of lowered effective refractory period could be distinguished from their surroundings in simulated scenarios with successfully induced multi-wavelet re-entry. Larger areas and higher gradients in effective refractory period as well as complex activation patterns favour the method. The 25% quantile of cycle lengths in patients with persistent atrial fibrillation was found to range from 85 to 190 ms.

CONCLUSION

Cycle length mapping is capable of highlighting regions of pathologic refractory properties. In combination with complementary substrate mapping approaches, the method fosters confidence to enhance the treatment of atrial fibrillation beyond pulmonary vein isolation particularly in patients with complex activation patterns.

Local catheter impedance drop during pulmonary vein isolation predicts acute conduction block in patients with paroxysmal atrial fibrillation: initial results of the LOCALIZE clinical trial

Aims

Radiofrequency ablation creates irreversible cardiac damage through resistive heating and this temperature change results in a generator impedance drop. Evaluation of a novel local impedance (LI) technology measured exclusively at the tip of the ablation catheter found that larger LI drops were indicative of more effective lesion formation. We aimed to evaluate whether LI drop is associated with conduction block in patients with paroxysmal atrial fibrillation (AF) undergoing pulmonary vein isolation (PVI).

Methods and results

Sixty patients underwent LI-blinded de novo PVI using a point-by-point ablation workflow. Pulmonary vein rings were divided into 16 anatomical segments. After a 20-min waiting period, gaps were identified on electroanatomic maps. Median LI drop within segments with inter-lesion distance ≤6 mm was calculated offline. The diagnostic accuracy of LI drop for predicting segment block was assessed using receiver operating characteristic analysis.

For segments with inter-lesion distance ≤6 mm, acutely blocked segments had a significantly larger LI drop [19.8 (14.1–27.1) Ω] compared with segments with gaps [10.6 (7.8–14.7) Ω, P < 0.001). In view of left atrial wall thickness differences, the association between LI drop and block was further evaluated for anterior/roof and posterior/inferior segments. The optimal LI cut-off value for anterior/roof segments was 16.1 Ω (positive predictive value for block: 96.3%) and for posterior/inferior segments was 12.3 Ω (positive predictive value for block: 98.1%) where inter-lesion distances were ≤6 mm.

Conclusion

The magnitude of LI drop was predictive of acute PVI segment conduction block in patients with paroxysmal AF. The thinner posterior wall required smaller LI drops for block compared with the thicker anterior wall.

Using Machine Learning to Characterize Atrial Fibrotic Substrate From Intracardiac Signals With a Hybrid in silico and in vivo Dataset

In patients with atrial fibrillation, intracardiac electrogram signal amplitude is known to decrease with increased structural tissue remodeling, referred to as fibrosis. In addition to the isolation of the pulmonary veins, fibrotic sites are considered a suitable target for catheter ablation. However, it remains an open challenge to find fibrotic areas and to differentiate their density and transmurality. This study aims to identify the volume fraction and transmurality of fibrosis in the atrial substrate. Simulated cardiac electrograms, combined with a generalized model of clinical noise, reproduce clinically measured signals. Our hybrid dataset approach combines in silico and clinical electrograms to train a decision tree classifier to characterize the fibrotic atrial substrate. This approach captures different in vivo dynamics of the electrical propagation reflected on healthy electrogram morphology and synergistically combines it with synthetic fibrotic electrograms from in silico experiments. The machine learning algorithm was tested on five patients and compared against clinical voltage maps as a proof of concept, distinguishing non-fibrotic from fibrotic tissue and characterizing the patient's fibrotic tissue in terms of density and transmurality. The proposed approach can be used to overcome a single voltage cut-off value to identify fibrotic tissue and guide ablation targeting fibrotic areas.

CVAR-Seg: An Automated Signal Segmentation Pipeline for Conduction Velocity and Amplitude Restitution

BACKGROUND

Rate-varying S1S2 stimulation protocols can be used for restitution studies to characterize atrial substrate, ionic remodeling, and atrial fibrillation risk. Clinical restitution studies with numerous patients create large amounts of these data. Thus, an automated pipeline to evaluate clinically acquired S1S2 stimulation protocol data necessitates consistent, robust, reproducible, and precise evaluation of local activation times, electrogram amplitude, and conduction velocity. Here, we present the CVAR-Seg pipeline, developed focusing on three challenges: (i) No previous knowledge of the stimulation parameters is available, thus, arbitrary protocols are supported. (ii) The pipeline remains robust under different noise conditions. (iii) The pipeline supports segmentation of atrial activities in close temporal proximity to the stimulation artifact, which is challenging due to larger amplitude and slope of the stimulus compared to the atrial activity.

METHODS AND RESULTS

The S1 basic cycle length was estimated by time interval detection. Stimulation time windows were segmented by detecting synchronous peaks in different channels surpassing an amplitude threshold and identifying time intervals between detected stimuli. Elimination of the stimulation artifact by a matched filter allowed detection of local activation times in temporal proximity. A non-linear signal energy operator was used to segment periods of atrial activity. Geodesic and Euclidean inter electrode distances allowed approximation of conduction velocity. The automatic segmentation performance of the CVAR-Seg pipeline was evaluated on 37 synthetic datasets with decreasing signal-to-noise ratios. Noise was modeled by reconstructing the frequency spectrum of clinical noise. The pipeline retained a median local activation time error below a single sample (1 ms) for signal-to-noise ratios as low as 0 dB representing a high clinical noise level. As a proof of concept, the pipeline was tested on a CARTO case of a paroxysmal atrial fibrillation patient and yielded plausible restitution curves for conduction speed and amplitude.

CONCLUSION

The proposed openly available CVAR-Seg pipeline promises fast, fully automated, robust, and accurate evaluations of atrial signals even with low signal-to-noise ratios. This is achieved by solving the proximity problem of stimulation and atrial activity to enable standardized evaluation without introducing human bias for large data sets.

Final results from the EU focal impulse and rotor modulation (E-FIRM) registry

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Abbott

Background

The exact pathophysiology of how pulmonary vein (PV) triggers initiate or maintain episodes of atrial fibrillation (AF) has been elusive. Catheter ablation at relatively circumscribed areas of rapidly spinning rotors or very rapid focal impulse formation can significantly affect AF. Targeted ablation of these sources using Focal Impulse and Rotor Modulation (FIRM™) shows promise.

Purpose

To assess the safety and effectiveness of FIRM-guided procedures for the treatment of any type of symptomatic atrial fibrillation (AF).

Methods

Two hundred and ninety-nine subjects were enrolled in the E-FIRM Registry at 9 clinical sites in Germany and the Netherlands. Subjects were eligible if they had reported incidence of at least 2 documented episodes of symptomatic AF during the preceding 3 months and had failed at least Class I or III anti-arrhythmia drug. Data was collected at enrollment/baseline, procedure, and at 3-, 6-, and 12-month follow-up visits.

Results

A majority (59.5%, 178/299) had a history of previous ablation, 81.1% (133/164) in the left side, with an average of 1.5 ± 0.8 [range 0, 5] prior ablations. The primary safety endpoint was defined as freedom from procedure related Serious Adverse Events (SAEs) through 7-days and at 12-months. At 7-days, freedom from procedure related SAEs was 94.8% (257/271). At 12-months, freedom from procedure related SAEs was 84.4% (184/218). There were no deaths. Acute effectiveness success, defined as the elimination of all identified rotors, occurred in 64.0% (165/258) of treated patients. All patients for which data was reported had at least 1 rotor identified. The most common regions to find rotors were the lateral wall of the right atrium, the anterior/septal wall of the left atrium, and the posterior inferior region of the left atrium. 75.2% (194/258) of patients had at least one rotor identified in the right atrium, and 84.1% (217/258) of patients had at least one rotor identified in the left atrium. Success was defined as two sequential endpoints: single procedure freedom from AF recurrence at 3-months and single procedure freedom from AF recurrence. At 12-months, success was achieved in 46.4% (13/28) Paroxysmal, 42.9% (87/203) Persistent, and 0% (0/9) Long Standing AF subjects. Conclusions: Since acute success was reported as being achieved in only ∼2/3 of the treated subjects, it is possible that the full potential benefit of the FIRM-guided ablation was hidden in this evaluation of the full cohort. Considering the previous ablation and disease history of subjects, a single-procedure success rate at 12-months over 40% was considered a positive result. Based on these results, FIRM-guided RF ablation in conjunction with conventional RF ablation practices is both a safe and effective treatment strategy for patients with symptomatic AF.

Machine learning enables noninvasive prediction of atrial fibrillation driver location and acute pulmonary vein ablation success using the 12-lead ECG

BACKGROUND

Atrial fibrillation (AF) is the most common supraventricular arrhythmia, characterized by disorganized atrial electrical activity, maintained by localized arrhythmogenic atrial drivers. Pulmonary vein isolation (PVI) allows to exclude PV-related drivers. However, PVI is less effective in patients with additional extra-PV arrhythmogenic drivers.

OBJECTIVES

To discriminate whether AF drivers are located near the PVs vs extra-PV regions using the noninvasive 12-lead electrocardiogram (ECG) in a computational and clinical framework, and to computationally predict the acute success of PVI in these cohorts of data.

METHODS

AF drivers were induced in 2 computerized atrial models and combined with 8 torso models, resulting in 1128 12-lead ECGs (80 ECGs with AF drivers located in the PVs and 1048 in extra-PV areas). A total of 103 features were extracted from the signals. Binary decision tree classifier was trained on the simulated data and evaluated using hold-out cross-validation. The PVs were subsequently isolated in the models to assess PVI success. Finally, the classifier was tested on a clinical dataset (46 patients: 23 PV-dependent AF and 23 with additional extra-PV sources).

RESULTS

The classifier yielded 82.6% specificity and 73.9% sensitivity for detecting PV drivers on the clinical data. Consistency analysis on the 46 patients resulted in 93.5% results match. Applying PVI on the simulated AF cases terminated AF in 100% of the cases in the PV class.

CONCLUSION

Machine learning-based classification of 12-lead-ECG allows discrimination between patients with PV drivers vs those with extra-PV drivers of AF. The novel algorithm may aid to identify patients with high acute success rates to PVI.

Non-Invasive Characterization of Atrial Flutter Mechanisms Using Recurrence Quantification Analysis on the ECG: A Computational Study

OBJECTIVE

Atrial flutter (AFl) is a common arrhythmia that can be categorized according to different self-sustained electrophysiological mechanisms. The non-invasive discrimination of such mechanisms would greatly benefit ablative methods for AFl therapy as the driving mechanisms would be described prior to the invasive procedure, helping to guide ablation. In the present work, we sought to implement recurrence quantification analysis (RQA) on 12-lead ECG signals from a computational framework to discriminate different electrophysiological mechanisms sustaining AFl.

METHODS

20 different AFl mechanisms were generated in 8 atrial models and were propagated into 8 torso models via forward solution, resulting in 1,256 sets of 12-lead ECG signals. Principal component analysis was applied on the 12-lead ECGs, and six RQA-based features were extracted from the most significant principal component scores in two different approaches: individual component RQA and spatial reduced RQA.

RESULTS

In both approaches, RQA-based features were significantly sensitive to the dynamic structures underlying different AFl mechanisms. Hit rate as high as 67.7% was achieved when discriminating the 20 AFl mechanisms. RQA-based features estimated for a clinical sample suggested high agreement with the results found in the computational framework.

CONCLUSION

RQA has been shown an effective method to distinguish different AFl electrophysiological mechanisms in a non-invasive computational framework. A clinical 12-lead ECG used as proof of concept showed the value of both the simulations and the methods.

SIGNIFICANCE

The non-invasive discrimination of AFl mechanisms helps to delineate the ablation strategy, reducing time and resources required to conduct invasive cardiac mapping and ablation procedures.

Comparison of procedural efficacy and biophysical parameters between two competing cryoballoon technologies for pulmonary vein isolation: Insights from an initial multicenter experience

Introduction

Recently a novel cryoballoon system (POLARx, Boston Scientific) became available for the treatment of atrial fibrillation. This cryoballoon is comparable with Arctic Front Advance Pro (AFA‐Pro, Medtronic), however, it maintains a constant balloon pressure. We compared the procedural efficacy and biophysical characteristics of both systems.

Methods

One hundred and ten consecutive patients who underwent first‐time cryoballoon ablation (POLARx: n = 57; AFA‐Pro: n = 53) were included in this prospective cohort study.

Results

Acute isolation was achieved in 99.8% of all pulmonary veins (POLARx: 99.5% vs. AFA‐Pro: 100%, p = 1.00). Total procedure time (81 vs. 67 min, p < .001) and balloon in body time (51 vs. 35 min, p < .001) were longer with POLARx. After a learning curve, these times were similar. Cryoablation with POLARx was associated with shorter time to balloon temperature −30°C (27 vs. 31 s, p < .001) and −40°C (32 vs. 54 s, p < .001), lower balloon nadir temperature (−55°C vs. −47°C, p < .001), and longer thawing time till 0°C (16 vs. 9 s, p < .001). There were no differences in time‐to‐isolation (TTI; POLARx: 45 s vs. AFA‐Pro 43 s, p = .441), however, POLARx was associated with a lower balloon temperature at TTI (−46°C vs. −37°C, p < .001). Factors associated with acute isolation differed between groups. The incidence of phrenic nerve palsy was comparable (POLARx: 3.5% vs. AFA‐Pro: 3.7%).

Conclusion

The novel cryoballoon is comparable to AFA‐Pro and requires only a short learning curve to get used to the slightly different handling. It was associated with faster cooling rates and lower balloon temperatures but TTI was similar to AFA‐Pro.

[Careers in cardiac electrophysiology]

Cardiac electrophysiology has developed into a broad, exciting, and challenging subdiscipline of modern cardiology. The professional opportunities available to electrophysiologists are diverse and offer a wide variety of career goals. The aim of this article is to show young cardiologists what different career paths can look like if they opt for electrophysiology today. Personal testimonials from five experienced electrophysiologists on their own career paths show decisions, support, obstacles, and destinations of these paths to practice or university professorship. This article aims to support young cardiologists who are considering specialization in electrophysiology during their career planning.

664Local catheter impedance drop during pulmonary vein isolation predicts conduction block in patients with paroxysmal atrial fibrillation: initial results of the LOCALIZE clinical trial

Funding Acknowledgements

Boston Scientific

Background

Radiofrequency (RF) catheter ablation for pulmonary vein isolation (PVI) requires resistively heating cardiac tissue to create conduction block. Creation of an RF lesion results in an impedance drop and the magnitude of this drop depends on the temperature and amount of myocardium being heated. Pre-clinical and clinical evaluation of an advanced local impedance (LI) metric found that greater LI drops were indicative of more effective lesion formation.

Purpose

To evaluate whether LI drop is associated with conduction block after first pass encirclement of the PVs in patients with paroxysmal AF.

Methods

LOCALIZE is an ongoing, single-arm, multi-center clinical trial (clinicaltrials.gov NCT03232645). LOCALIZE consists of an index PVI procedure (results presented here) and a 3-month follow-up mapping procedure. In the index procedure, electroanatomical maps of the left atrium were created and ipsilateral PVs were divided into 8 anatomical segments (n = 16 per patient). PVI was performed using point-by-point ablation with blinding of operators to LI. Following initial encirclement and a 20-minute wait period, coronary sinus-paced electroanatomical maps were created to identify gaps within anatomical segments. Gaps were annotated on the map and subsequently ablated. Mean LI drop within each segment was calculated offline as an estimate of regional RF energy delivery (Figure - Left). The diagnostic accuracy of LI drop for predicting segment block was assessed using receiver operating characteristic (ROC) analysis in segments with inter-lesion spacing ≤6mm.

Results

Forty-seven patients with paroxysmal AF underwent PVI at 5 centers (age 62 ± 11 years, male 55.3%). All patients left the index procedure with all PVs isolated. When blinded to LI (n = 3,064 ablations), median baseline LI was 106 (IQR: 97-115) Ω and median LI drop was 18.4 (12.7-24.9) Ω. After first pass encirclement, blocked segments had a significantly larger LI drop (20.2 [14.6-26.0] Ω) than segments with gaps (10.6 [6.9-15.1] Ω, p &lt; 0.01, Figure - Right). The association between LI drop and block was further evaluated along anatomical anterior/posterior wall thickness differences. Anterior block segments were found to have significantly larger LI drops (21.0 [15.9-27.2] Ω) than posterior block segments (16.6 [12.7-23.7] Ω, p &lt; 0.01). ROC analysis of segments with inter-lesion spacing ≤6mm identified optimal LI cut-off values of 16Ω in anterior segments and 11Ω posteriorly, which had positive predictive values for conduction block of 95.6% and 96.7%, respectively.

Conclusions

The magnitude of LI drop is predictive of acute PVI segment conduction block in patients with paroxysmal AF. The thinner posterior wall required smaller LI drops for block compared to the thicker anterior wall. With inter-lesion spacing of ≤6mm, reaching a LI drop of ≥16Ω anteriorly and ≥11Ω posteriorly was highly predictive of acute segment block in de novo PVI.

Abstract Figure. Local impedance drop in de novo PVI

Sex-specific efficacy and safety of cryoballoon versus radiofrequency ablation for atrial fibrillation: An individual patient data meta-analysis

BACKGROUND

Atrial fibrillation (AF) is a growing health burden, and pulmonary vein isolation (PVI) using cryoballoon (CB) or radiofrequency (RF) represents an attractive therapeutic option. Sex-specific differences in the epidemiology, pathophysiology, and clinical presentation of AF and PVI are recognized.

OBJECTIVE

We aimed at comparing the efficacy, safety, and procedural characteristics of CB and RF in women and men undergoing a first PVI procedure.

METHODS

We searched for randomized controlled trials and prospective observational studies comparing CB and RF ablation with at least 1 year of follow-up. After merging individual patient data from 18 data sets, we investigated the sex-specific (procedure failure defined as recurrence of atrial arrhythmia, reablation, and reinitiation of antiarrhythmic medication), safety (periprocedural complications), and procedural characteristics of CB vs RF using Kaplan-Meier and multilevel models.

RESULTS

From the 18 studies, 4840 men and 1979 women were analyzed. An analysis stratified by sex correcting for several covariates showed a better efficacy of CB in men (hazard ratio for recurrence 0.88; 95% confidence interval 0.78-0.98, P = .02) but not in women (hazard ratio 0.98; 95% confidence interval 0.83-1.16; P = .82). For women and men, the energy source had no influence on the occurrence of at least 1 complication. For both sexes, the procedure time was significantly shorter with CB (-22.5 minutes for women and -27.1 minutes for men).

CONCLUSION

CB is associated with less long-term failures in men. A better understanding of AF-causal sex-specific mechanisms and refinements in CB technologies could lead to higher success rates in women.

Impact of Dialysis on the Prognosis of Patients Undergoing Transcatheter Aortic Valve Implantation

End-stage renal disease (ESRD) affects approximately 2% to 4% of patients with severe aortic stenosis. It is because these patients have been excluded from clinical trials, the impact of transcatheter aortic valve implantation (TAVI) in this patient group has not been thoroughly investigated. Between April 2008 and March 2015, 2,000 patients (dialysis group, n = 56 [2.8%]) were consecutively enrolled when diagnosed with severe aortic stenosis and eligible to undergo TAVI. Procedural and longer-term outcomes were analyzed and adjusted for differences in baseline characteristics. Patients on dialysis had a higher periprocedural mortality (10.7% vs 1.7%; adjusted odds ratio [adjOR] 5.65, 95% confidence interval [CI] 1.91 to 16.67; p = 0.002) and a lower Valve Academic Research Consortium (VARC)-II (VARC) defined device success (adjOR 0.34, 95% CI 0.15 to 0.79; p = 0.012). At 30 days, there was an increased rate of all-cause mortality (21.4 vs 4.8%; adjOR 4.90, 95% CI 1.96 to 12.26; p = 0.001), cardiovascular (adjOR 3.67, 95% CI 1.43 to 9.41; p = 0.007) and noncardiovascular mortality (adjOR 6.28, 95% CI 1.36 to 9.41; p = 0.019), myocardial infarction (adjOR 9.39, 95% CI 1.84 to 48.03; p = 0.007), bleeding (adjOR 2.48, 95% CI 1.06 to 5.83; p = 0.036) as well as the VARC-II defined early safety combined end point (adjOR 2.97, 95% CI 1.28 to 6.90; p = 0.012) associated with dialysis. Dialysis was associated with poor survival at one (57.1% vs 84.2%) and 3 years (26.8% vs 66.9%) with or without the consideration of the first 72 hours (p <0.001; adjusted p <0.001). Although, in the multivariable regression analysis, reduced ejection fraction, peripheral arterial disease, pulmonary hypertension (PH), frailty and dialysis were associated with 1-year mortality, only PH (>60 mm Hg) remained significant in an analysis restricted to the dialysis patients (adjusted hazard ratio 2.68; 95% CI 1.18 to 5.88; p = 0.018). PH had a sensitivity of 45.8%, a specificity of 81.3%, and a positive predictive value of 64.7%. In conclusion, dialysis is an independent predictor of mortality in patients who underwent TAVI. Long-term mortality in dialysis patients appears to be largely determined by the kidney disease and/or dialysis itself whereas VARC-II defined complications are largely unaffected. An increased short-term mortality still calls for (pre-) procedural optimization.

Patient-Specific Identification of Atrial Flutter Vulnerability-A Computational Approach to Reveal Latent Reentry Pathways

Atypical atrial flutter (AFlut) is a reentrant arrhythmia which patients frequently develop after ablation for atrial fibrillation (AF). Indeed, substrate modifications during AF ablation can increase the likelihood to develop AFlut and it is clinically not feasible to reliably and sensitively test if a patient is vulnerable to AFlut. Here, we present a novel method based on personalized computational models to identify pathways along which AFlut can be sustained in an individual patient. We build a personalized model of atrial excitation propagation considering the anatomy as well as the spatial distribution of anisotropic conduction velocity and repolarization characteristics based on a combination of a priori knowledge on the population level and information derived from measurements performed in the individual patient. The fast marching scheme is employed to compute activation times for stimuli from all parts of the atria. Potential flutter pathways are then identified by tracing loops from wave front collision sites and constricting them using a geometric snake approach under consideration of the heterogeneous wavelength condition. In this way, all pathways along which AFlut can be sustained are identified. Flutter pathways can be instantiated by using an eikonal-diffusion phase extrapolation approach and a dynamic multifront fast marching simulation. In these dynamic simulations, the initial pattern eventually turns into the one driven by the dominant pathway, which is the only pathway that can be observed clinically. We assessed the sensitivity of the flutter pathway maps with respect to conduction velocity and its anisotropy. Moreover, we demonstrate the application of tailored models considering disease-specific repolarization properties (healthy, AF-remodeled, potassium channel mutations) as well as applicabiltiy on a clinical dataset. Finally, we tested how AFlut vulnerability of these substrates is modulated by exemplary antiarrhythmic drugs (amiodarone, dronedarone). Our novel method allows to assess the vulnerability of an individual patient to develop AFlut based on the personal anatomical, electrophysiological, and pharmacological characteristics. In contrast to clinical electrophysiological studies, our computational approach provides the means to identify all possible AFlut pathways and not just the currently dominant one. This allows to consider all relevant AFlut pathways when tailoring clinical ablation therapy in order to reduce the development and recurrence of AFlut.

Spatio-temporal Analysis of Multichannel Atrial Electrograms Based on a Concept of Active Areas

Atrial tachycardia and atrial flutter are frequent arrhythmia that occur spontaneously and after ablation of atrial fibrillation. Depolarization waves that differ significantly from sinus rhythm propagate across the atria with high frequency (typically 140 to 220 beats per minute). A detailed and personalized analysis of the spread of depolarization is imperative for a successful ablation therapy. Thus, catheters with several electrodes are employed to measure multichannel electrograms inside the atria. Here we propose a new concept for spatio-temporal analysis of multichannel electrograms during atrial tachycardia and atrial flutter. It is based on the calculation of simultaneously active areas. The method allows to identify atrial tachycardia and to automatically distinguish between subtypes of focal activity, micro-reentry and macro-reentry.

Evolution of transcatheter aortic valve implantation over 7 years: results of a prospective single-centre registry of 2000 patients in a large municipal hospital (TAVIK Registry)

OBJECTIVES

Use of transcatheter aortic valve implantation (TAVI) to treat severe aortic stenosis (AS) has gained popularity, accompanied by an evolution of patient and clinical factors. We aimed to characterise changes and evaluate their impact on outcomes.

SETTING

In this single-centre, German TAVIK registry patients undergoing TAVI between 2008 and 2015 were documented prospectively.

PARTICIPANTS/INTERVENTIONS

2000 consecutive patients with AS undergoing TAVI were divided in four cohorts. 500 patients underwent TAVI in each of the following time bins: April 2008 to July 2010 (cohort I), July 2010 to April 2013 (cohort II), April 2012 to October 2013 (cohort III) and October 2013 to March 2015 (cohort IV).

RESULTS

The mean age was 81.8 years, without significant variation across cohorts. Compared with cohort I, prior MI (5.4%vs11.0%; p<0.001) and New York Heart Association class IV (10.0%vs3.6%; p<0.001) were less common in cohort IV. Across cohorts, there was a fall in EuroSCORE (24.3%-18.7%), frailty (48.4%-17.0%) and use of transapical access (43.6%-29.0%), while transfemoral access increased (56.4%-71.0%; p<0.001 for each). Periprocedurally, there was a fall in moderate/severe aortic regurgitation (3.2%-0.0%) and rate of unplanned cardiopulmonary bypass (4.0%-1.0%; both p<0.001). A similar trend applied to 30-day rate of major vascular complications (5.2%-1.8%; p=0.006), life-threatening bleeding (7.0%-3.0%; p<0.001) and cardiovascular mortality (4.4%-1.8%; p=0.020). One-year post-TAVI, mortality and stroke rates did not differ.

CONCLUSIONS

Evolution of TAVI between 2008 and 2015 saw a trend towards its usage in lower risk patients and rapid progression towards improved safety. Evaluation and refinement should now continue to further lessen stroke and pacemaker rates.

High-density Mapping Reveals Short-term Reversibility of Atrial Ablation Lesions

Cardiac arrhythmias such as atrial fibrillation occur frequently in industrialized countries. Radiofrequency ablation (RFA) is a standard treatment if drug therapy fails. This minimally invasive surgery aims at stabilizing the heart rhythm on a permanent basis. However, the procedure commonly needs to be repeated because of the high recurrence rate of arrhythmias. Non-transmural lesions as well as gaps within linear lesions are among the main problems during the RFA. The assessment of lesion formation is not adequate in state of the art procedures. Therefore, the aim of this study is to investigate the short-term reversibility of lesions using human electrograms recorded by a high-density mapping system during an electrophysiological study (EPS). A predefined measurement protocol was executed during the EPS in order to create three ablation points in the left atrium. Subsequently, after preprocessing the recorded signals, electrogram (EGM) paths were formed along the endocardial surface of the atrium. By analyzing changes of peak to peak amplitudes of unipolar EGMs before and after ablation, it was possible to distinguish lesion area and healthy myocardium. The peak to peak amplitudes of the EGMs decreased by 40-61% after 30 seconds of ablation. Furthermore, we analyzed the morphological changes of EGMs surrounding the lesion. High-density mapping data showed that not only the tissue, which had direct contact with the catheter tip during the RFA, but also the surrounding tissue was affected. This was demonstrated by low peak to peak amplitudes in large areas with a width of 14 mm around the center of the ablation lesion. After right pulmonary vein isolation, high-density mapping was repeated on the previous lesions. The outer region of RFA-treated tissue appears to recover as opposed to the central core of the ablation point. This observation suggests that the meaningfulness of an immediate remap after ablation during an EPS may lead the physician to false conclusions

Two-Year Outcomes of Transcatheter Compared With Surgical Aortic Valve Replacement in "Minimal-Risk" Patients Lacking EuroSCORE Co-morbidities (from the TAVIK Registry)

We aimed to compare the outcomes of transcatheter aortic valve implantation (TAVI) with surgical aortic valve replacement (SAVR) in an elderly but nonfrail, minimally co-morbid population. Although data comparing these 2 procedures in intermediate- and low-risk patients are mounting, no distinction has been made between co-morbidity and age/gender as driving forces for surgical risk. Patients undergoing isolated TAVI or SAVR between May 2008 and March 2015 were documented. Data for 225 patients (TAVI 132, SAVR 93) aged ≥75 and <86 years and fulfilling minimal-risk criteria were analyzed. Patients who underwent TAVI were older (80.7 vs 77.4 years, p <0.0001) and had a higher mean Society of Thoracic Surgeons score (2.16% vs 1.72%, p <0.0001). Mild prosthetic valve regurgitation (odds ratio [OR] 4.9, 95% confidence interval [CI] 3.34 to 7.20) was more likely after TAVI, as were renal complications (predominantly stage I acute kidney injury; OR 2.86, 95% CI 1.79 to 4.55) and new pacemaker implantation (OR 3.33, 95% CI 1.76 to 6.26) at 30 days; however, life-threatening bleeding (OR 0.58, 95% CI 0.36 to 0.93) and reintervention for bleeding (OR 0.03, 95% CI 0.01 to 0.13) were less likely. Survival was comparable between groups at 30 days (99.2% vs 100%, p = 1.0) and 1 year (96.2% vs 96.8%, OR 0.85, 95% CI 0.20 to 3.63, p = 0.823), but it was poorer for patients who underwent TAVI at 2 years (OR 0.31, 95% CI 0.16 to 0.61). In conclusion, the short-term outcomes of TAVI in elderly, low-risk, minimally co-morbid patients appear to be similar to those of SAVR, with access-specific complications. Although these results point toward the potential for more liberal use of TAVI in minimal-risk patients, poorer midterm survival remains a concern, requiring further exploration.

Periprocedural anticoagulation during left atrial ablation: interrupted and uninterrupted vitamin K-antagonists or uninterrupted novel anticoagulants

Background

There is a lack of data on anticoagulation requirements during ablation of atrial fibrillation (AF). This study compares different oral anticoagulation (OAC) strategies to evaluate risk of bleeding and thromboembolic complications.

Methods

We conducted a single-centre study in patients undergoing left atrial ablation of AF. Three groups were defined: 1) bridging: interrupted vitamin-K-antagonists (VKA), INR ≤2, and bridging with heparin; 2) VKA: uninterrupted VKA and INR of > 2; 3) DOAC: uninterrupted direct oral anticoagulants. Bleeding complications, thromboembolic events and peri-procedural heparin doses were assessed.

Results

In total, 780 patients were documented. At 48 h, major complications were more common in the bridging group compared to uninterrupted VKA and DOAC groups (OR: 3.42, 95% CI: 1.29–9.10 and OR: 3.01, 95% CI: 1.19–7.61), largely driven by differences in major pericardial effusion (OR: 4.86, 95% CI: 1.56–15.99 and OR: 4.466, 95% CI, 1.52–13.67) and major vascular events (OR: 2.92, 95% CI: 0.58–14.67 and OR: 9.72, 95% CI: 1.00–94.43). Uninterrupted VKAs and DOACs resulted in similar odds of major complications (overall OR: 1.14, 95% CI: 0.44–2.92), including cerebrovascular events (OR: 1.21, 95% CI: 0.27–5.45). However, whereas only TIAs were observed in DOAC and bridging groups, strokes also occurred in the VKA group. Rates of minor complications (pericardial effusion, vascular complications, gastrointestinal hemorrhage) and major/minor groin hemorrhage were similar across groups.

Conclusion

Our dataset illustrates that uninterrupted VKA and DOAC have a better risk-benefit profile than VKA bridging. Bridging was associated with a 4.5× increased risk of complications and should be avoided, if possible.

Cryoballoon vs. radiofrequency ablation for paroxysmal atrial fibrillation: an updated meta-analysis of randomized and observational studies

Aims

Radiofrequency (RF) ablation represents a standard of care for pulmonary vein isolation in patients with drug-refractory paroxysmal atrial fibrillation (AF). In this setting, cryoballoon (CB) ablation has emerged as alternative therapy. However, the efficacy and safety of CB vs. RF ablation in patients with paroxysmal AF remain a matter of debate.

Methods and results

We searched electronic scientific databases for studies of CB vs. RF ablation in patients with paroxysmal AF. Aggregate data were pooled to perform a meta-analysis. The primary efficacy and safety outcomes were the recurrence of any atrial arrhythmia and procedure-related complications, respectively. A total of 6473 participants from 10 studies (CB, n = 2232 vs. RF, n = 4241) were studied. After a median follow-up of 16 months, the risk of any atrial arrhythmia recurrence (risk ratio, RR 95% confidence interval [95% CI] = 1.01 [0.90-1.14], P = 0.83) and procedure-related complications (RR [95% CI] = 0.92 [0.66-1.28], P = 0.61) were comparable between CB vs. RF ablation. Cryoballoon ablation led to a higher risk of persistent phrenic nerve palsy (RR [95% CI] = 13.60 [3.87-47.81], P < 0.01) and a lower risk of cardiac tamponade (RR [95% CI] = 0.48 [0.25-0.89], P = 0.02) compared with RF ablation. There was a trend of statistically significant interaction between the type of CB and the duration of ablation (P for interaction = 0.09).

Conclusion

In patients with paroxysmal AF, ablation therapy with CB is associated with efficacy and safety comparable to that of RF. Second-generation CB catheters seem to reduce procedure duration. Further studies are warranted to disclose the impact of second-generation CB catheters compared with RF for ablation of paroxysmal AF.

Transcatheter aortic valve implantation in patients with a reduced left ventricular ejection fraction: a single-centre experience in 2000 patients (TAVIK Registry)

BACKGROUND

Previous studies into the effect of a reduced left ventricular ejection fraction (EF) on the short- and long-term prognosis of patients undergoing transcatheter aortic valve implantation (TAVI) have reported conflicting findings. We analysed data from the Karlsruhe TAVI registry with the aim of addressing this question.

METHODS AND RESULTS

Patients with aortic stenosis undergoing TAVI were divided into sub-groups according to EF: severely reduced (<30%; n = 109), reduced (≥30 and ≤40%; n = 201), and mid-range/preserved (>40%; n = 1690). VARC complications at 30 days for the population with severely reduced EF did not differ in comparison to the patients with mid-range/preserved EF. Patients with severely reduced EF had a significantly lower survival at 48 h (91.7 vs. 99.0%; p < 0.001), at 30 days (84.4 vs. 95.8%; p < 0.001) and at 1 year (66.1 vs. 85.0%, p < 0.001) compared to those with mid-range/preserved EF. The risk of death increased with age, peripheral arterial disease, poor self-care and chronic renal failure in patients with severely reduced EF.

CONCLUSIONS

Mortality post-TAVI was higher for patients with a reduced EF, although the excess comorbidity burden likely contributed to this. A reduced EF should not be considered a contraindication for TAVI per se, but the additional presence of comorbidity indicates increased risk for these patients.

Cryoballoon vs. open irrigated radiofrequency ablation for paroxysmal atrial fibrillation: long-term FreezeAF outcomes

Background

Effective treatment of paroxysmal atrial fibrillation (AF) is essential for reducing the risk of stroke and heart failure. Cryoballoon (CB) ablation has been developed as an alternative to the use of radiofrequency (RF) energy for electrical isolation of the pulmonary veins. Herein, we provide long-term data regarding the efficacy of CB ablation in comparison to RF.

Methods

FreezeAF was a randomised non-inferiority study comparing CB ablation with RF ablation for the treatment of patients with drug-refractory paroxysmal AF. Procedural success for the long-term follow-up (30 months) was defined as freedom from AF with an absence of persistent complications.

Results

Of the 315 patients that were randomised and received catheter ablation, 292 (92.7%) completed the 30-month follow-up (147 in the RF group and 145 in the CB group). The baseline characteristics of the RF and CB groups were similar. Single-procedure success was achieved by 40% of patients in the RF group and 42% of the CB group (p < 0.001 for non-inferiority). When including re-do procedures in the analysis, the multiple procedure success rate was 72% in the RF group and 76% in the CB group.

Conclusion

The data provide long-term evidence that CB ablation is non-inferior to RF ablation, with high proportions of patients reporting freedom from AF 30 months after the index procedure.

Trial registration

ClinicalTrials.gov Identifier: NCT00774566; first registered October 16, 2008; first patient included October 20, 2008.

Fuzzy decision tree to classify complex fractionated atrial electrograms

Catheter ablation has emerged as an effective treatment strategy for atrial fibrillation (AF) in recent years. During AF, complex fractionated atrial electrograms (CFAE) can be recorded and are known to be a potential target for ablation. Automatic algorithms have been developed to simplify CFAE detection, but they are often based on a single descriptor or a set of descriptors in combination with sharp decision classifiers. However, these methods do not reflect the progressive transition between CFAE classes. The aim of this study was to develop an automatic classification algorithm, which combines the information of a complete set of descriptors and allows for progressive and transparent decisions. We designed a method to automatically analyze CFAE based on a set of descriptors representing various aspects, such as shape, amplitude and temporal characteristics. A fuzzy decision tree (FDT) was trained and evaluated on 429 predefined electrograms. CFAE were classified into four subgroups with a correct rate of 81±3%. Electrograms with continuous activity were detected with a correct rate of 100%. In addition, a percentage of certainty is given for each electrogram to enable a comprehensive and transparent decision. The proposed FDT is able to classify CFAE with respect to their progressive transition and may allow objective and reproducible CFAE interpretation for clinical use.

P wave detection and delineation in the ECG based on the phase free stationary wavelet transform and using intracardiac atrial electrograms as reference

Robust and exact automatic P wave detection and delineation in the electrocardiogram (ECG) is still an interesting but challenging research topic. The early prognosis of cardiac afflictions such as atrial fibrillation and the response of a patient to a given treatment is believed to improve if the P wave is carefully analyzed during sinus rhythm. Manual annotation of the signals is a tedious and subjective task. Its correctness depends on the experience of the annotator, quality of the signal, and ECG lead. In this work, we present a wavelet-based algorithm to detect and delineate P waves in individual ECG leads. We evaluated a large group of commonly used wavelets and frequency bands (wavelet levels) and introduced a special phase free wavelet transformation. The local extrema of the transformed signals are directly related to the delineating points of the P wave. First, the algorithm was studied using synthetic signals. Then, the optimal parameter configuration was found using intracardiac electrograms and surface ECGs measured simultaneously. The reverse biorthogonal wavelet 3.3 was found to be optimal for this application. In the end, the method was validated using the QT database from PhysioNet. We showed that the algorithm works more accurately and more robustly than other methods presented in literature. The validation study delivered an average delineation error of the P wave onset of -0.32±12.41 ms when compared to manual annotations. In conclusion, the algorithm is suitable for handling varying P wave shapes and low signal-to-noise ratios.

[Atrial fibrillation: rate or rhythm control?]

In the face of current demographic developments the incidence of atrial fibrillation is increasing. Depending on comorbidities, structural heart disease and patient choice different treatment strategies can be followed. Learn about the aspects that are important in choosing a tailored, evidence-based treatment of atrial fibrillation for your patient.

Automatic detection and mapping of double potentials in intracardiac electrograms

Catheter ablation has become a very efficient strategy to terminate sustained cardiac arrhythmias like atrial flutter (AFlut). Identification of the optimal ablation spot, however, often proves difficult when scar from previous ablations is present. Although the application of electro-anatomical mapping systems allows to record thousands of intracardiac electrograms (EGMs) from each atrium, state-of-the-art techniques provide limited options for automatic signal processing. Goal of the presented research was the development of an algorithm to detect EGMs that present double potentials (DPs), as these often indicate functional or anatomical lines of block for cardiac excitation. Using an annotated database, we developed several features based on the morphological descriptors of DPs. These were used to train a binary decision tree which was able to detect DPs with a correct rate of over 90%.