Atrial fibrillation increases thrombogenicity of LVAD therapy

BACKGROUND

This study investigates the hypothesis that presence of atrial fibrillation (AF) in LVAD patients increases thrombogenicity in the left ventricle (LV) and exacerbates stroke risk.

METHODS

Using an anatomical LV model implanted with an LVAD inflow cannula, we analyze thrombogenic risk and blood flow patterns in either AF or sinus rhythm (SR) using unsteady computational fluid dynamics (CFD). To analyze platelet activation and thrombogenesis in the LV, hundreds of thousands of platelets are individually tracked to quantify platelet residence time (RT) and shear stress accumulation history (SH).

RESULTS

The irregular and chaotic mitral inflow associated with AF results in markedly different intraventricular flow patterns, with profoundly negative impact on blood flow-induced stimuli experienced by platelets as they traverse the LV. Twice as many platelets accumulated very high SH in the LVAD + AF case, resulting in a 36% increase in thrombogenic potential score, relative to the LVAD + SR case.

CONCLUSIONS

This supports the hypothesis that AF results in unfavorable blood flow patterns in the LV adding to an increased stroke risk for LVAD + AF patients. Quantification of thrombogenic risk associated with AF for LVAD patients may help guide clinical decision-making on interventions to mitigate the increased risk of thromboembolic events.

Machine learning identifies esophageal luminal temperature patterns associated with thermal injury in catheter ablation for atrial fibrillation

INTRODUCTION

Luminal esophageal temperature (LET) monitoring during atrial fibrillation (AF) ablation is widely used to reduce the incidence of endoscopically detected esophageal lesion (EDEL). We sought to assess whether specific patterns of LET variation are associated with EDEL.

METHODS

A high-fidelity multisensor probe was used to record LET in AF patients undergoing radiofrequency ablation (RFA) or cryoballoon ablation (CBA). Explainable machine learning and SHapley Additive exPlanations (SHAP) analysis were used to predict EDEL and assess feature importance.

RESULTS

A total of 94 patients (38.3% persistent AF, 71.3% male, 72 RFA, and 22 CBA) were included. EDEL was detected in 11 patients (10 RFA and one CBA). In the RFA group, the highest LET recorded was similar between patients with and without EDEL (40.6 [40.1-41]°C vs. 40.2 [39.1-40.9]°C; p = .313), however, the rate of LET rise for the highest recorded peak was higher (0.08 [0.03-0.12]°C/s vs. 0.02 [0.01-0.05]°C/s; p = .033), and the area under the curve (AUC) for the highest peak was smaller (412.5 [206.8-634.1] vs. 588.6 [380.4-861.1]; p = .047) in patients who had EDEL. In case of CBA, the patient with EDEL had a faster LET decline (0.12 vs. 0.07 [0.02-0.14]°C/s), and a smaller AUC for the lowest trough (2491.3 vs. 2629.3 [1712.6-5283.2]). SHAP analysis revealed that a rate of LET change higher than 0.05°C/s and an AUC less than 600 were more predictive of EDEL in RFA.

CONCLUSION

The rate of LET change and AUC for the recorded temperature predicted EDEL, whereas absolute peak temperatures did not.

Esophageal luminal temperature monitoring using a multi-sensor probe lowers the risk of esophageal injury in cryo and radiofrequency catheter ablation for atrial fibrillation

BACKGROUND

Esophageal luminal temperature monitoring is a commonly used strategy to reduce esophageal thermal injury in catheter ablation for atrial fibrillation (AFib).

OBJECTIVES

We sought to compare the incidence of endoscopically detected esophageal lesions (EDEL) between two commonly used esophageal luminal temperature probes.

METHODS

Consecutive patients undergoing ablation with esophageal luminal temperature monitoring and upper endoscopy within 24 h after ablation were included.

RESULTS

Four hundred forty-five patients (64 ± 10 years, 44% female) were included. Esophageal temperature monitoring was done with a single-sensor probe in 213 (48%) and multi-sensor probe in 232 (52%). Cryoballoon (CB) ablation was performed in 118 (27%) and radiofrequency (RF) ablation in 327 (73%) of patients. EDEL was present in 94 (22.9%) of which 85 were mild, 8 were moderate, and 1 was severe, and none progressed to atrial-esophageal fistula. The use of the multi-sensor probe during CB ablation was associated with a reduction in EDEL compared to single sensor (6.8% vs 24.3%; P = 0.016). Similarly, in the RF ablation group, EDEL was present in 19.5% of the multi-sensor group vs 32.8% in the single-sensor group (P = 0.001). Logistic regression showed that multi-sensor probe use was associated with reduction in EDEL with an odds ratio of 0.23 in CB ablation (P = 0.024) and 0.44 for RF ablation (P = 0.001).

CONCLUSIONS

Esophageal luminal temperature monitoring during AFib ablation using a multi-sensor probe was associated with a significant reduction in EDEL compared to a single-sensor probe.

Comparing Inducibility of Re-Entrant Arrhythmia in Patient-Specific Computational Models to Clinical Atrial Fibrillation Phenotypes

BACKGROUND

Computational models of fibrosis-mediated, re-entrant left atrial (LA) arrhythmia can identify possible substrate for persistent atrial fibrillation (AF) ablation. Contemporary models use a 1-size-fits-all approach to represent electrophysiological properties, limiting agreement between simulations and patient outcomes.

OBJECTIVES

The goal of this study was to test the hypothesis that conduction velocity (ϴ) modulation in persistent AF models can improve simulation agreement with clinical arrhythmias.

METHODS

Patients with persistent AF (n = 37) underwent ablation and were followed up for ≥2 years to determine post-ablation outcomes: AF, atrial flutter (AFL), or no recurrence. Patient-specific LA models (n = 74) were constructed using pre-ablation and ≥90 days' post-ablation magnetic resonance imaging data. Simulated pacing gauged in silico arrhythmia inducibility due to AF-like rotors or AFL-like macro re-entrant tachycardias. A physiologically plausible range of ϴ values (±10 or 20% vs. baseline) was tested, and model/clinical agreement was assessed.

RESULTS

Fifteen (41%) patients had a recurrence with AF and 6 (16%) with AFL. Arrhythmia was induced in 1,078 of 5,550 simulations. Using baseline ϴ, model/clinical agreement was 46% (34 of 74 models), improving to 65% (48 of 74) when any possible ϴ value was used (McNemar's test, P = 0.014). ϴ modulation improved model/clinical agreement in both pre-ablation and post-ablation models. Pre-ablation model/clinical agreement was significantly greater for patients with extensive LA fibrosis (>17.2%) and an elevated body mass index (>32.0 kg/m2).

CONCLUSIONS

Simulations in persistent AF models show a 41% relative improvement in model/clinical agreement when ϴ is modulated. Patient-specific calibration of ϴ values could improve model/clinical agreement and model usefulness, especially in patients with higher body mass index or LA fibrosis burden. This could ultimately facilitate better personalized modeling, with immediate clinical implications.

Cryoballoon temperature parameters during cryoballoon ablation predict pulmonary vein reconnection and atrial fibrillation recurrence

BACKGROUND

Cryoballoon ablation (CBA) is an established approach for rhythm management of atrial fibrillation (AF). We sought to assess balloon temperature (BT) parameters as predictors of pulmonary vein (PV) reconnection within the index procedure and AF recurrence following CBA.

METHODS

BT was monitored in 119 AF patients undergoing CBA. PVs were assessed for reconnection during the procedure and patients were followed for arrhythmia recurrence.

RESULTS

PV reconnection was identified in 39 (8.3%) of 471 PVs. BT was significantly colder in the absence of PV reconnection (30 s: - 33.5 °C [- 36; - 30] vs - 29.5 °C [- 35; - 25.5], p = 0.001; 60 s: - 41 °C [- 44; - 37] vs - 36.5 °C [- 42; - 33.5], p < 0.001; nadir: - 47 °C [- 52; - 43] vs - 41.5 °C [- 47; - 38], p < 0.001). PV reconnection was associated with significantly longer time to reach - 15 °C and - 40 °C (14.5 s [11.5-18.5] vs 12 s [10-15.5], p = 0.023; and 75 s [40-95.5] vs 46 s [37-66.75], p = 0.005) and shorter rewarming time (5.75 s [4.75-8.5] vs 7 s [6-9], p = 0.012). ROC analysis of these procedural parameters had an AUC = 0.71 in predicting PV reconnection. AF recurrence occurred in 51 (42.8%) patients. Kaplan-Meier analysis showed better arrhythmia-free survival for patients in whom BT decreased below - 40 °C in all PVs and patients who had no early PV reconnections, compared to patients in whom BT below - 40 °C was not achieved in at least one PV (log rank = 6.3, p = 0.012) and patients who had PV reconnections (log rank = 4.1, p = 0.043).

CONCLUSIONS

Slower BT decline, warmer BT nadir, and faster rewarming time predict early PV reconnection. Absence of early PV reconnections and BT dropping below - 40 °C in all PVs during CBA are associated with lower rates of AF recurrence.

Explainable Machine Learning to Predict Anchored Reentry Substrate Created by Persistent Atrial Fibrillation Ablation in Computational Models

Background Postablation arrhythmia recurrence occurs in ~40% of patients with persistent atrial fibrillation. Fibrotic remodeling exacerbates arrhythmic activity in persistent atrial fibrillation and can play a key role in reentrant arrhythmia, but emergent interaction between nonconductive ablation-induced scar and native fibrosis (ie, residual fibrosis) is poorly understood. Methods and Results We conducted computational simulations in pre- and postablation left atrial models reconstructed from late gadolinium enhanced magnetic resonance imaging scans to test the hypothesis that ablation in patients with persistent atrial fibrillation creates new substrate conducive to recurrent arrhythmia mediated by anchored reentry. We trained a random forest machine learning classifier to accurately pinpoint specific nonconductive tissue regions (ie, areas of ablation-delivered scar or vein/valve boundaries) with the capacity to serve as substrate for anchored reentry-driven recurrent arrhythmia (area under the curve: 0.91±0.03). Our analysis suggests there is a distinctive nonconductive tissue pattern prone to serving as arrhythmogenic substrate in postablation models, defined by a specific size and proximity to residual fibrosis. Conclusions Overall, this suggests persistent atrial fibrillation ablation transforms substrate that favors functional reentry (ie, rotors meandering in excitable tissue) into an arrhythmogenic milieu more conducive to anchored reentry. Our work also indicates that explainable machine learning and computational simulations can be combined to effectively probe mechanisms of recurrent arrhythmia.

Personalized biomechanical insights in atrial fibrillation: opportunities & challenges

INTRODUCTION

Atrial fibrillation (AF) is an increasingly prevalent and significant worldwide health problem. Manifested as an irregular atrial electrophysiological activation, it is associated with many serious health complications. AF affects the biomechanical function of the heart as contraction follows the electrical activation, subsequently leading to reduced blood flow. The underlying mechanisms behind AF are not fully understood, but it is known that AF is highly correlated with the presence of atrial fibrosis, and with a manifold increase in risk of stroke.

AREAS COVERED

In this review, we focus on biomechanical aspects in atrial fibrillation, current and emerging use of clinical images, and personalized computational models. We also discuss how these can be used to provide patient-specific care.

EXPERT OPINION

Understanding the connection betweenatrial fibrillation and atrial remodeling might lead to valuable understanding of stroke and heart failure pathophysiology. Established and emerging imaging modalities can bring us closer to this understanding, especially with continued advancements in processing accuracy, reproducibility, and clinical relevance of the associated technologies. Computational models of cardiac electromechanics can be used to glean additional insights on the roles of AF and remodeling in heart function.

Positional obstructive sleep apnea in patients with atrial fibrillation

PURPOSE

Obstructive sleep apnea (OSA) is a common, potentially modifiable condition implicated in the pathogenesis of atrial fibrillation (AF). The presence and severity of OSA is largely sleep position-dependent, yet there is high variability in positional dependence among patients with OSA. We investigated the prevalence of positional OSA (POSA) and examined associated factors in patients with AF.

METHODS

We recruited an equal number of patients with and without AF who underwent diagnostic polysomnography. Patients included had ≥ 120 min of total sleep time with 30 min of sleep in both supine and lateral positions. POSA was defined as an overall apnea hypopnea index (AHI) ≥ 5/h, supine AHI (sAHI) ≥ 5/h, and sAHI greater than twice the non-supine AHI. POSA prevalence was compared in patients with and without AF adjusting for age, sex, OSA severity, and heart failure.

RESULTS

A total of patients (male: 56%, mean age 62 years) were included. POSA prevalence was similar between the two groups (46% vs. 39%; p = 0.33). Obesity and severe OSA (AHI ≥ 30/h) were associated with low likelihood of POSA (OR [CI] of 0.17 [0.09-0.32] and 0.28 [0.12-0.62]). In patients with AF, male sex was associated with a higher likelihood of POSA (OR [CI] of 3.16 [1.06-10.4]).

CONCLUSION

POSA is common, affecting more than half of patients with AF, but the prevalence was similar in those without AF. Obesity and more severe OSA are associated with lower odds of POSA. Positional therapy should be considered in patients with mild OSA and POSA.

Machine Learning and the Conundrum of Stroke Risk Prediction

Stroke is a leading cause of death worldwide. With escalating healthcare costs, early non-invasive stroke risk stratification is vital. The current paradigm of stroke risk assessment and mitigation is focused on clinical risk factors and comorbidities. Standard algorithms predict risk using regression-based statistical associations, which, while useful and easy to use, have moderate predictive accuracy. This review summarises recent efforts to deploy machine learning (ML) to predict stroke risk and enrich the understanding of the mechanisms underlying stroke. The surveyed body of literature includes studies comparing ML algorithms with conventional statistical models for predicting cardiovascular disease and, in particular, different stroke subtypes. Another avenue of research explored is ML as a means of enriching multiscale computational modelling, which holds great promise for revealing thrombogenesis mechanisms. Overall, ML offers a new approach to stroke risk stratification that accounts for subtle physiologic variants between patients, potentially leading to more reliable and personalised predictions than standard regression-based statistical associations.

Network meta-analysis and systematic review comparing efficacy and safety between very high power short duration, high power short duration, and conventional radiofrequency ablation of atrial fibrillation

BACKGROUND

High-power short-duration (HPSD) atrial fibrillation (AF) ablation with a power of 40-50 W was proved to be safe and effective. Very high-power short-duration (vHPSD) AF ablation is a novel method using >50 W to obtain more durable AF ablation. This study aimed to evaluate the efficacy and safety of vHPSD ablation compared with HPSD ablation and conventional power ablation.

METHODS

A literature search for studies that reported AF ablation outcomes, including short-term freedom from atrial arrhythmia, first-pass isolation (FPI) rate, procedure time, and major complications, was conducted utilizing MEDLINE, EMBASE, and Cochrane databases. All relevant studies were included in this analysis. A random-effects model of network meta-analysis and surface under cumulative ranking curve (SUCRA) were used to rank the treatment for all outcomes.

RESULTS

A total of 29 studies with 9721 patients were included in the analysis. According to the SUCRA analysis, HPSD ablation had the highest probability of maintaining sinus rhythm. Point estimation showed an odds ratio of 1.5 (95% confidence interval [CI]: 1.2-1.9) between HPSD ablation and conventional power ablation and an odds ratio of 1.3 (95% CI: 0.78-2.2) between vHPSD ablation and conventional power ablation. While the odds ratio of FPI between HPSD ablation and conventional power ablation was 3.6 (95% CI: 1.5-8.9), the odds ratio between vHPSD ablation and conventional power ablation was 2.2 (95% CI: 0.61-8.6). The procedure times of vHPSD and HPSD ablations were comparable and, therefore, shorter than that of conventional power ablation. Major complications were low in all techniques.

CONCLUSION

vHPSD ablation did not yield higher efficacy than HPSD ablation and conventional power ablation. With the safety concern, vHPSD ablation outcomes were comparable with those of other techniques.

Elevated fibrosis burden as assessed by MRI predicts cryoballoon ablation failure

INTRODUCTION

Late-gadolinium enhancement magnetic resonance (LGE-MRI) imaging is increasingly used in management of atrial fibrillation (AFib) patients. Here, we assess the usefulness of LGE-MRI-based fibrosis quantification to predict arrhythmia recurrence in patients undergoing cryoballoon ablation. Our secondary goal was to compare two widely used fibrosis quantification methods.

METHODS

In 102 AF patients undergoing LGE-MRI and cryoballoon ablation (mean age 62 years; 64% male; 59% paroxysmal AFib), atrial fibrosis was quantified using the pixel intensity histogram (PIH) and image intensity ratio (IIR) methods. PIH segmentations were completed by a third-party provider as part of the standard of care at our hospital; Image intensity ratio (IIR) segmentations of the same scans were carried out in our lab using a commercially available software package. Fibrosis burdens and spatial distributions for the two methods were compared. Patients were followed prospectively for recurrent arrhythmia following ablation.

RESULTS

Average PIH fibrosis was 15.6 ± 5.8% of the left atrial (LA) volume. Depending on threshold (IIRthr ), the average IIR fibrosis (% of LA wall surface area) ranged from 5.0 ± 7.2% (IIRthr  = 1.2) to 37.4 ± 10.9% (IIRthr  = 0.97). An IIRthr of 1.03 demonstrated the greatest agreement between the methods, but spatial overlap of fibrotic areas delineated by the two methods was modest (Sorenson Dice coefficient: 0.49). Fourty-two patients (41.2%) had recurrent arrhythmia. PIH fibrosis successfully predicted recurrence (HR 1.07; p = .02) over a follow-up period of 362 ± 149 days; regardless of IIRthr , IIR fibrosis did not predict recurrence.

CONCLUSIONS

PIH-based volumetric assessment of atrial fibrosis was modestly predictive of arrhythmia recurrence following cryoballoon ablation in this cohort. IIR-based fibrosis was not predictive of recurrence for any of the IIRthr values tested, and the overlap in designated areas of fibrosis between the PIH and IIR methods was modest. Caution must therefore be exercised when interpreting LA fibrosis from LGE-MRI, since the values and spatial pattern are methodology-dependent.

Effect of MRI-Guided Fibrosis Ablation vs Conventional Catheter Ablation on Atrial Arrhythmia Recurrence in Patients With Persistent Atrial Fibrillation: The DECAAF II Randomized Clinical Trial

Importance

Ablation of persistent atrial fibrillation (AF) remains a challenge. Left atrial fibrosis plays an important role in the pathophysiology of AF and has been associated with poor procedural outcomes.

Objective

To investigate the efficacy and adverse events of targeting atrial fibrosis detected on magnetic resonance imaging (MRI) in reducing atrial arrhythmia recurrence in persistent AF.

Design, Setting, and Participants

The Efficacy of Delayed Enhancement-MRI-Guided Fibrosis Ablation vs Conventional Catheter Ablation of Atrial Fibrillation trial was an investigator-initiated, multicenter, randomized clinical trial involving 44 academic and nonacademic centers in 10 countries. A total of 843 patients with symptomatic or asymptomatic persistent AF and undergoing AF ablation were enrolled from July 2016 to January 2020, with follow-up through February 19, 2021.

Interventions

Patients with persistent AF were randomly assigned to pulmonary vein isolation (PVI) plus MRI-guided atrial fibrosis ablation (421 patients) or PVI alone (422 patients). Delayed-enhancement MRI was performed in both groups before the ablation procedure to assess baseline atrial fibrosis and at 3 months postablation to assess for ablation scar.

Main Outcomes and Measures

The primary end point was time to first atrial arrhythmia recurrence after a 90-day blanking period postablation. The primary safety composite outcome was defined by the occurrence of 1 or more of the following events within 30 days postablation: stroke, PV stenosis, bleeding, heart failure, or death.

Results

Among 843 patients who were randomized (mean age 62.7 years; 178 [21.1%] women), 815 (96.9%) completed the 90-day blanking period and contributed to the efficacy analyses. There was no significant difference in atrial arrhythmia recurrence between groups (fibrosis-guided ablation plus PVI patients, 175 [43.0%] vs PVI-only patients, 188 [46.1%]; hazard ratio [HR], 0.95 [95% CI, 0.77-1.17]; P = .63). Patients in the fibrosis-guided ablation plus PVI group experienced a higher rate of safety outcomes (9 [2.2%] vs 0 in PVI group; P = .001). Six patients (1.5%) in the fibrosis-guided ablation plus PVI group had an ischemic stroke compared with none in PVI-only group. Two deaths occurred in the fibrosis-guided ablation plus PVI group, and the first one was possibly related to the procedure.

Conclusions and Relevance

Among patients with persistent AF, MRI-guided fibrosis ablation plus PVI, compared with PVI catheter ablation only, resulted in no significant difference in atrial arrhythmia recurrence. Findings do not support the use of MRI-guided fibrosis ablation for the treatment of persistent AF.

Trial Registration

ClinicalTrials.gov Identifier: NCT02529319.

Catheter Ablation for Atrial Fibrillation in the Elderly > 75 Years old: Systematic Review and Meta-Analysis

INTRODUCTION

Atrial fibrillation (AF) ablation is increasingly performed worldwide. As comfort with AF ablation increases, the procedure is increasingly used in patients that are older and in those with more comorbidities. However, it is not well established whether AF ablation in the elderly, especially those >75 years old, has comparable safety and efficacy to younger populations.

OBJECTIVE

To compare the efficacy and safety profiles in patients older than 75years undergoing AF ablation with younger patients.

METHODS

Databases from EMBASE, Medline, PubMed and Cochrane, were searched from inception through September 2021. Studies that compared the success rates in AF catheter ablation and all complications rates between patients who were older vs under 75 years were included. Effect estimates from the individual studies were extracted and combined using random effect, generic inverse variance method of DerSimonian and Laird.

RESULTS

Twenty-seven observational studies were included in the analysis consisting of 363,542 patients who underwent AF ablation. Comparing patients older than 75 years old to younger patients, there was no difference in the success of ablation rates between elderly and younger patients (pooled OR 0.85: 95% CI:0.69 - 1.05, p=0.131). On the other hand, AF ablation in the elderly was associated with higher complication rates (pooled OR 1.43: 95% CI:1.21 - 1.68, p<0.001) CONCLUSION: As AF ablation is expanded to elderly populations, our study found that AF ablation success rates were similar in both elderly and younger patients. However, older patients experience higher rates of complications that should be considered when offering the procedure and as a means to improve outcomes with future innovations. This article is protected by copyright. All rights reserved.

Epicardial adipose tissue is associated with left atrial volume and fibrosis in patients with atrial fibrillation

Background

Obesity is a risk factor for atrial fibrillation (AF) and strongly influences the response to treatment. Atrial fibrosis shows similar associations. Epicardial adipose tissue (EAT) may be a link between these associations. We sought to assess whether EAT is associated with body mass index (BMI), left atrial (LA) fibrosis and volume.

Methods

LA fibrosis and EAT were assessed using late gadolinium enhancement, and Dixon MRI sequences, respectively. We derived 3D models incorporating fibrosis and EAT, then measured the distance of fibrotic and non-fibrotic areas to the nearest EAT to assess spatial colocalization.

Results

One hundred and three AF patients (64% paroxysmal, 27% female) were analyzed. LA volume index was 54.9 (41.2, 69.7) mL/m², LA EAT index was 17.4 (12.7, 22.9) mL/m², and LA fibrosis was 17.1 (12.4, 23.1)%. LA EAT was significantly correlated with BMI (R = 0.557, p < 0.001); as well as with LA volume and LA fibrosis after BSA adjustment (R = 0.579 and R = 0.432, respectively, p < 0.001 for both). Multivariable analysis showed LA EAT to be independently associated with LA volume and fibrosis. 3D registration of fat and fibrosis around the LA showed no clear spatial overlap between EAT and fibrotic LA regions.

Conclusion

LA EAT is associated with obesity (BMI) as well as LA volume and fibrosis. Regions of LA EAT did not colocalize with fibrotic areas, suggesting a systemic or paracrine mechanism rather than EAT infiltration of fibrotic areas.

MRI-quantified left atrial epicardial adipose tissue predicts atrial fibrillation recurrence following catheter ablation

Background

Epicardial adipose tissue (EAT) plays a significant role in promoting atrial fibrillation (AF) due to its proinflammatory properties and anatomic proximity to the myocardium. We sought to assess whether left atrial (LA) EAT volume is associated with AF recurrence following catheter ablation.

Methods

EAT was assessed via the 3D MRI Dixon sequence in 101 patients undergoing AF ablation. Patients were followed for arrhythmia recurrence.

Results

During an average follow-up period of 1 year, post-ablation AF recurrence occurred in 31 (30.7%) patients. LA EAT index was higher in those with compared to without recurrence (20.7 [16.9, 30.4] vs. 13.7 [10.5, 20.1] mL/m², p < 0.001), and so was LA volume index (66 [52.6, 77.5] vs. 49.9 [37.7, 61.8] mL/m², p = 0.001). Cox regression analysis showed LA EAT (HR = 1.089; 95% CI: [1.049-1.131], p < 0.001) to be an independent predictor of post-ablation AF recurrence. The ROC curve for LA EAT index in the prediction of AF recurrence had an AUC of 0.77 (95% CI 0.68-0.86, p < 0.001) and showed an optimal cutoff value of 14.29 mL/m² to identify patients at risk of post-ablation AF recurrence. Integrating LA EAT with clinical risk factors improved prediction of AF recurrence (AUC increased from 0.65 to 0.79, DeLong test p = 0.044). Kaplan-Meier analysis for recurrence-free survival showed a significant difference between two groups of patients identified by the optimal LA EAT index cutoff of 14.29 mL/m² (log rank = 14.79; p < 0.001).

Conclusion

EAT quantified using cardiac MRI, a reproducible and widely accessible imaging parameter, is a strong and independent predictor of post-ablation AF recurrence.

Atrial Fibrosis, Ischaemic Stroke and Atrial Fibrillation

Atrial fibrosis is an important component of the arrhythmic substrate in AF. Evidence suggests that atrial fibrosis also plays a role in increasing the risk of stroke in patients with the arrhythmia. Patients with embolic stroke of undetermined source (ESUS), who are suspected to have AF but are rarely shown to have it, frequently demonstrate evidence of atrial fibrosis; measured using late-gadolinium enhancement MRI, this manifests as atrial remodelling encompassing structural, functional and electrical properties. In this review, the authors discuss the available evidence linking atrial disease, including fibrosis, with the risk of ischaemic stroke in AF, as well as in the ESUS population, in whom it has been linked to recurrent stroke and new-onset AF. They also discuss the implications of this association on future research that may elucidate the mechanism of stroke and stroke prevention strategies in the AF and ESUS populations.

Catheter ablation of atrial fibrillation results in significant QTc prolongation in the postoperative period

Background

The corrected QT interval (QTc) is a measure of ventricular repolarization time, and a prolonged QTc increases risk for malignant ventricular arrhythmias. Pulmonary vein isolation (PVI) may increase QTc but its effects have not been well studied.

Objective

Determine the incidence, risk factors, and outcomes of patients presenting for PVI in sinus and atrial fibrillation with postoperative QTc prolongation in a large cohort.

Methods

We performed a single-center retrospective study of consecutive atrial fibrillation ablations. QTc durations using Bazett correction were obtained from electrocardiograms at different postoperative intervals and compared to preoperative QTc. We studied clinical outcomes including clinically significant ventricular arrhythmia and death. A multivariable model was used to identify factors associated with clinically significant QTc prolongation, defined as ΔQTc ≥60 ms or new QTc duration ≥500 ms.

Results

A total of 352 PVIs were included in this study. We observed a statistically significant increase in mean QTc compared to baseline (446.3 ± 37.8 ms) on postoperative day (POD)0 (471.7 ± 38.2 ms, P < .001) and at POD1 (456.5 ± 35.0 ms, P < .001). There was no significant difference at 1 month (452.4 ± 33.5 ms, P = .39) and 3 months (447.3 ± 40.0 ms, P = .78). Sixty-six patients (19.2%) developed ΔQTc ≥60 ms or QTc ≥500 ms on POD0, with 4.1% persisting past 90 days. Female sex (odds ratio [OR] = 1.82, 95% confidence interval [CI] =1.01–3.29, P = .047) and history of coronary artery disease (OR = 2.16, 95% CI = 1.03–4.55, P = .042) were independently predictive of QTc prolongation ≥500 ms or ΔQTc ≥60 ms. There were no episodes of clinically significant ventricular arrhythmia or death attributable to arrhythmia.

Conclusion

QTc duration increased significantly immediately post-PVI and returned to baseline by 1 month. PVI did not provoke significant ventricular arrhythmias in our cohort.

Effect of DrOnedarone on atrial fibrosis progression and atrial fibrillation recurrence postablation: Design of the EDORA randomized clinical trial

Background

Atrial fibrillation (AF) recurrence after catheter ablation is associated with worse outcomes and quality of life. Left atrial (LA) structural remodeling provides the essential substrate for AF perpetuation. Baseline extent and the progression of LA fibrosis after ablation are strong predictors of postprocedural AF recurrence. Dronedarone is an antiarrhythmic drug proven to efficiently maintain sinus rhythm.

Objective

We sought to investigate the effect of the antiarrhythmic drug Dronedarone in decreasing LA fibrosis progression and AF recurrence after ablation of AF patients.

Methods

EDORA (NCT04704050) is a multicenter, prospective, randomized controlled clinical trial. Patients with persistent or paroxysmal AF undergoing AF ablation will be randomized into Dronedarone versus placebo/standard of care. The co‐primary outcomes are the recurrence of atrial arrhythmias (AA) within 13 months of follow‐up after ablation and the progression of left atrial fibrosis postablation. All patients will receive a late‐gadolinium enhancement magnetic resonance imaging at baseline, 3‐ and 12‐month follow‐up for the quantification of LA fibrosis and ablation‐related scarring. AA recurrence and burden will be assessed using a 30‐day ECG patch every 3 months with daily ECG recordings in between. Quality of life improvement is assessed using the AFEQT and AFSS questionnaires.

Conclusion

EDORA will be the first trial to assess the progression of LA structural remodeling after ablation and its association with Dronedarone treatment and ablation success in a randomized controlled fashion. The trial will provide insight into the pathophysiology of AF recurrence after ablation and may provide potential therapeutic targets to optimize procedural outcomes.

HRS White Paper on Clinical Utilization of Digital Health Technology

This collaborative statement from the Digital Health Committee of the Heart Rhythm Society provides everyday clinical scenarios in which wearables may be utilized by patients for cardiovascular health and arrhythmia management. We describe herein the spectrum of wearables that are commercially available for patients, and their benefits, shortcomings and areas for technological improvement. Although wearables for rhythm diagnosis and management have not been examined in large randomized clinical trials, undoubtedly the usage of wearables has quickly escalated in clinical practice. This document is the first of a planned series in which we will update information on wearables as they are revised and released to consumers.

Atrial fibrosis in embolic stroke of undetermined source: A multicenter study

BACKGROUND AND PURPOSE

Left atrial (LA) cardiac disease is a suspected cause of embolic stroke of undetermined source (ESUS). We tested the hypothesis that LA fibrosis, quantified using late-gadolinium-enhancement magnetic resonance imaging (LGE-MRI), predicts recurrent stroke or atrial fibrillation (AF) in patients with ESUS.

METHODS

We compared atrial fibrosis in healthy controls and patients with lacunar stroke, ESUS, and known AF with or without prior stroke. We followed patients with ESUS prospectively for the primary outcome of recurrent ischemic stroke, incident AF, or both.

RESULTS

We enrolled 203 patients from three centers: 103 patients without AF (35 healthy controls, 15 with lacunar strokes, 53 with ESUS) and 100 patients with AF (50 with and 50 without prior stroke). Patients with ESUS had significantly higher atrial fibrosis (15.0 ± 6.2%) compared to healthy controls (8.1 ± 7.9%; <0.0001) and compared to lacunar stroke patients (10.8 ± 8.4; p = 0.02), but had comparable fibrosis to patients with AF with (17.9 ± 11.4%) or without prior stroke (16.6 ± 9.2%; p = NS for both). Over a mean follow-up of 19 months, nine of 53 patients (16.9%) with ESUS experienced the combined primary outcome, which included six patients (11.3%) with recurrent ischemic stroke and five patients with incident AF (9.4%). Patients with ESUS with fibrosis ≥12% had a higher proportion of the combined outcome: 25.0% vs. 4.8%; p = 0.039.

CONCLUSIONS

Patients with ESUS demonstrate atrial fibrosis comparable to that seen in AF. Atrial fibrosis ≥12% was associated with recurrent stroke, incident AF or both. This subgroup of ESUS patients may benefit from anticoagulation for secondary prevention of ischemic stroke.

Computational modeling identifies embolic stroke of undetermined source patients with potential arrhythmic substrate

Cardiac magnetic resonance imaging (MRI) has revealed fibrosis in embolic stroke of undetermined source (ESUS) patients comparable to levels seen in atrial fibrillation (AFib). We used computational modeling to understand the absence of arrhythmia in ESUS despite the presence of putatively pro-arrhythmic fibrosis. MRI-based atrial models were reconstructed for 45 ESUS and 45 AFib patients. The fibrotic substrate's arrhythmogenic capacity in each patient was assessed computationally. Reentrant drivers were induced in 24/45 (53%) ESUS and 22/45 (49%) AFib models. Inducible models had more fibrosis (16.7 ± 5.45%) than non-inducible models (11.07 ± 3.61%; p<0.0001); however, inducible subsets of ESUS and AFib models had similar fibrosis levels (p=0.90), meaning that the intrinsic pro-arrhythmic substrate properties of fibrosis in ESUS and AFib are indistinguishable. This suggests that some ESUS patients have latent pre-clinical fibrotic substrate that could be a future source of arrhythmogenicity. Thus, our work prompts the hypothesis that ESUS patients with fibrotic atria are spared from AFib due to an absence of arrhythmia triggers.

Efficacy of LGE-MRI-guided fibrosis ablation versus conventional catheter ablation of atrial fibrillation: The DECAAF II trial: Study design

INTRODUCTION

Success rates of catheter ablation in persistent atrial fibrillation (AF) remain suboptimal. A better and more targeted ablation strategy is urgently needed to optimize outcomes of AF treatment. We sought to assess the safety and efficacy of targeting atrial fibrosis during ablation of persistent AF patients in improving procedural outcomes.

METHODS

The DECAAF II trial (ClinicalTrials. gov identifier number NCT02529319) is a prospective, randomized, multicenter trial of patients with persistent AF. Patients with persistent AF undergoing a first-time ablation procedure were randomized in a 1:1 fashion to receive conventional pulmonary vein isolation (PVI) ablation (Group 1) or PVI + fibrosis-guided ablation (Group 2). Left atrial fibrosis and ablation induced scarring were defined by late gadolinium enhancement magnetic resonance imaging at baseline and at 3-12 months postablation, respectively. The primary endpoint is the recurrence of atrial arrhythmia postablation, including atrial fibrillation, atrial flutter, or atrial tachycardia after the 90-day postablation blanking period. Patients were followed for a period of 12-18 months with a smartphone ECG Device (ECG Check Device, Cardiac Designs Inc.). With an anticipated enrollment of 900 patients, this study has an 80% power to detect a 26% reduction in the hazard ratio of the primary endpoint.

RESULTS AND CONCLUSION

The DECAAF II trial is the first prospective, randomized, multicenter trial of patients with persistent AF using imaging defined atrial fibrosis as a treatment target. The trial will help define an optimal approach to catheter ablation of persistent AF, further our understanding of influencers of ablation lesion formation, and refine selection criteria for ablation based on atrial myopathy burden.

Translational applications of computational modelling for patients with cardiac arrhythmias

Cardiac arrhythmia is associated with high morbidity, and its underlying mechanisms are poorly understood. Computational modelling and simulation approaches have the potential to improve standard-of-care therapy for these disorders, offering deeper understanding of complex disease processes and sophisticated translational tools for planning clinical procedures. This review provides a clinician-friendly summary of recent advancements in computational cardiology. Organ-scale models automatically generated from clinical-grade imaging data are used to custom tailor our understanding of arrhythmia drivers, estimate future arrhythmogenic risk and personalise treatment plans. Recent mechanistic insights derived from atrial and ventricular arrhythmia simulations are highlighted, and the potential avenues to patient care (eg, by revealing new antiarrhythmic drug targets) are covered. Computational approaches geared towards improving outcomes in resynchronisation therapy have used simulations to elucidate optimal patient selection and lead location. Technology to personalise catheter ablation procedures are also covered, specifically preliminary outcomes form early-stage or pilot clinical studies. To conclude, future developments in computational cardiology are discussed, including improving the representation of patient-specific fibre orientations and fibrotic remodelling characterisation and how these might improve understanding of arrhythmia mechanisms and provide transformative tools for patient-specific therapy.

Fibrosis, atrial fibrillation and stroke: clinical updates and emerging mechanistic models

The current paradigm of stroke risk assessment and mitigation in patients with atrial fibrillation (AF) is centred around clinical risk factors which, in the presence of AF, lead to thrombus formation. The mechanisms by which these clinical risk factors lead to thromboembolism, including any role played by atrial fibrosis, are not understood. In patients who had embolic stroke of undetermined source (ESUS), the problem is compounded by the absence of AF in a majority of patients despite long-term monitoring. Atrial fibrosis has emerged as a unifying mechanism that independently provides a substrate for arrhythmia and thrombus formation. Fibrosis-based computational models of AF initiation and maintenance promise to identify therapeutic targets in catheter ablation. In ESUS, fibrosis is also increasingly recognised as a major risk factor, but the underlying mechanism of this correlation is unclear. Simulations have uncovered potential vulnerability to arrhythmia induction in patients who had ESUS. Likewise, computational models of fluid dynamics representing blood flow in the left atrium and left atrium appendage have improved our understanding of thrombus formation, in particular left atrium appendage shapes and blood flow changes influenced by atrial remodelling. Multiscale modelling of blood flow dynamics based on structural fibrotic and morphological changes with associated cellular and tissue electrical remodelling leading to electromechanical abnormalities holds tremendous promise in providing a mechanistic understanding of the clinical problem of thromboembolisation. We present a review of clinical knowledge alongside computational modelling frameworks and conclude with a vision of a future paradigm integrating simulations in formulating personalised treatment plans for each patient.

Dynamic voltage threshold adjusted substrate modification technique for complex atypical atrial flutters with varying circuits

BACKGROUND

Atypical atrial flutter (AFL) is common in patients with postsurgical atrial scar, with macro- or microscopic channels in the scar acting as substrate for reentry. Heterogeneous atrial scarring can cause varying flutter circuits, which makes mapping and ablation challenging, and recurrences common.

AIM

We hypothesize that dynamically adjusting voltage thresholds can identify heterogeneous atrial scarring, which can then be effectively homogenized to eliminate atypical AFLs.

METHODS

We studied consecutive patients who presented to Electrophysiology laboratory for atypical AFL ablation with history of atriotomy and included the patients with multiple, varying flutter circuits during mapping in our study. We excluded patients with stable flutter circuit that was sustained and could be localized using traditional entrainment and activation mapping strategy. In the included patients, we performed detailed high-density voltage map of the atrium of interest. We adjusted voltage thresholds as needed to identify heterogeneity and channels in the scarred regions. A thorough scar homogenization was performed with irrigated smart-touch ablation catheter. Re-inducibility of tachycardia, and immediate and long-term outcomes were studied.

RESULTS

Of five studied cases, one was female; age 66 ± 10 years. All five had prior surgical substrate. All the patients had multiple flutter morphologies, which varied as we mapped the AFL. After scar homogenization, tachycardia was not inducible in any patient. No recurrence of flutter was noted during a mean follow-up duration of 450 ± 27 days.

CONCLUSION

High-density voltage mapping and homogenization of the scar can be an effective strategy in eliminating complex scar-mediated atypical AFL with multiple circuits.

Electrocardiographic left atrial abnormality in patients presenting with ischemic stroke

BACKGROUND

P wave indices represent electrocardiographic marker of left atrial pathology. We hypothesized that P wave would be more abnormal in patients presenting with ischemic stroke than a comparable group without ischemic stroke.

METHODS

We compared P wave terminal force in V1 (PTFV1) between patients admitted with ischemic stroke (case) and patients followed in cardiology clinic (control) at a single medical center. Using logistic regression models, we tested for an association between abnormal PTFV1 (> 4000 µV ms) and ischemic stroke. We also defined several optimal cut-off values of PTFV1 using a LOESS plot and estimated odds ratio of ischemic stroke when moving from one cut-point level to the next higher-level.

RESULTS

A total of 297 patients (case 147, control 150) were included. PTFV1 was higher in patients with vs. those without ischemic stroke (median 4620 vs 3994 µV ms; p=0.006). PTFV1 was similar between cardioembolic/cryptogenic and other stroke subtypes. In multivariable analyses adjusting for sex, obesity, age, and hypertension, the association between abnormal PTFV1 and ischemic stroke ceased to be significant (OR 1.53 [0.95, 2.50], p=0.083). Increase to the next cutoff level of PTFV1 (900, 2000, 3000, 4000, 5000, and 6000 µV ms) was associated with 18% increase in odds of having ischemic stroke (vs. no ischemic stroke) (OR 1.18 [1.02, 1.36], p=0.026).

CONCLUSION

Patients presenting with acute ischemic stroke are more likely to have abnormal PTFV1. These findings from a real-world clinical setting support the results of cohort studies that left atrial pathology manifested as abnormal PTFV1 is associated with ischemic stroke.

Survey of current perspectives on consumer-available digital health devices for detecting atrial fibrillation

BACKGROUND

Many digital health technologies capable of atrial fibrillation (AF) detection are directly available to patients. However, adaptation into clinical practice by heart rhythm healthcare practitioners (HCPs) is unclear.

OBJECTIVE

To examine HCP perspectives on use of commercial technologies for AF detection and management.

METHODS

We created an electronic survey for HCPs assessing practice demographics and perspectives on digital devices for AF detection and management. The survey was distributed electronically to all members of 3 heart rhythm professional societies.

RESULTS

We received 1601 responses out of 73,563 e-mails sent, with 43.6% from cardiac electrophysiologists, 12.8% from fellows, and 11.6% from advanced practice practitioners. Most respondents (62.3%) reported having recommended patient use of a digital device for AF detection. Those who did not had concerns about their accuracy (29.6%), clinical utility of results (22.8%), and integration into electronic health records (19.8%). Results from a 30-second single-lead electrocardiogram were sufficient for 42.7% of HCPs to recommend oral anticoagulation for patients at high risk for stroke. Respondents wanted more data comparing the accuracy of digital devices to conventional devices for AF monitoring (64.9%). A quarter (27.3%) of HCPs had no reservations recommending digital devices for AF detection, and most (53.4%) wanted guidelines from their professional societies providing guidance on their optimal use.

CONCLUSION

Many HCPs have already integrated digital devices into their clinical practice. However, HCPs reported facing challenges when using digital technologies for AF detection, and professional society recommendations on their use are needed.

Embolic stroke of undetermined source correlates to atrial fibrosis without atrial fibrillation

Objective

To examine the hypothesis that atrial fibrosis and associated atrial cardiopathy may be in the causal pathway of cardioembolic stroke independently of atrial fibrillation (AF) by comparing atrial fibrosis burden between patients with embolic stroke of undetermined source (ESUS), patients with AF, and healthy controls.

Methods

We used late-gadolinium-enhancement MRI to compare atrial fibrosis in 10 patients with ESUS against 10 controls (no stroke, no AF) and 10 patients with AF. Fibrosis was compared between groups, controlling for stroke risk factors.

Results

Mean age was 51 ± 15 years, and 43% of participants were female. Patients with ESUS had more atrial fibrosis than controls (16.8 ± 5.7% vs 10.6 ± 5.7%, p = 0.019) and similar fibrosis compared to patients with AF (17.8 ± 4.8%, p = 0.65). Odds ratios of ESUS per quartile of fibrosis were 3.22 (95% CI [CI] 1.11–9.32, p = 0.031, unadjusted) and 3.17 (95% CI 1.05–9.52, p = 0.041, CHA2DVASc score adjusted). Patients with >12% fibrosis had a higher percentage of ESUS (77.8% vs 27.3%, p = 0.02), and patients with >20% fibrosis had the highest proportion of ESUS (4 of 5).

Conclusions

Patients with ESUS exhibit similar atrial fibrosis compared to patients with AF and more fibrosis than healthy controls. Fibrosis is associated with ESUS after controlling for stroke risk factors, supporting the hypothesis that fibrosis is in the causal pathway of cardioembolic stroke independently of AF. Prospective studies are needed to assess the role of anticoagulation in primary and secondary stroke prevention in patients with high atrial fibrosis.