Atrial Rate Research Articles

Machine Learning‐Driven Identification of Distinct Persistent Atrial Fibrillation Phenotypes: A Cluster Analysis of DECAAF II

ABSTRACTIntroductionCatheter ablation of persistent atrial fibrillation yields sub‐optimal success rates partly due to the considerable heterogeneity within the patient population. Identifying distinct patient phenotypes based on post‐ablation prognosis could improve patient selection for additional therapies and optimize treatment strategies.MethodsWe studied all patients who underwent catheter ablation of persistent atrial fibrillation in the DECAAF II trial. Out of 44 participating centers, 25% were randomly chosen as a validation set. A Gradient Boosting Method determined essential features for arrhythmia recurrence prediction and the number of clusters was determined according to the average silhouette width. K‐medoids cluster analysis identified subgroups based on these features, and Kaplan–Meier curves were further compared among different clusters.ResultsAmong 815 patients, 570 served as a training set and 245 as a validation set. Using the training set, the GBM model achieved an AUC of 0.874. K‐medoids cluster analysis used LA volume, BMI, baseline fibrosis, and age, resulting in two clusters. Cluster 1 patients were older, had higher baseline fibrosis, higher BMI, and greater LA volume compared to Cluster 2. Atrial arrhythmia recurrence rates were significantly higher in Cluster 1 (51.7% vs. 35.0%, p = 0.0002), and survival analysis showed a significant difference in primary recurrence outcomes (HR = 1.71, p < 0.0001). The validation set confirmed these findings.ConclusionUtilizing machine learning, we identified a high‐risk cluster for procedural failure in catheter ablation of persistent atrial fibrillation within the DECAAF II trial population. The primary differentiating factors of this high‐risk cluster include older age, high left atrial fibrosis, elevated BMI, and increased left atrial volume.

Pulsed Field Ablation Using Focal Contact Force-Sensing Catheters for Treatment of Atrial Fibrillation: 1-Year Outcomes of the ECLIPSE AF Study.

Pulsed field ablation (PFA) is a promising treatment for atrial fibrillation. We report 1-year freedom from atrial arrhythmia outcomes using monopolar PFA delivered through 3 commercial, contact force-sensing focal catheters. ECLIPSE AF (NCT04523545) was a prospective, single-arm, multicenter study evaluating acute and chronic safety and performance using the CENTAURI system to deliver focal PFA with TactiCath SE, StablePoint, and ThermoCool ST. Patients with paroxysmal or persistent atrial fibrillation underwent pulmonary vein (PV) isolation under deep sedation or general anesthesia and returned for remapping at 90 days to evaluate chronic durability. Freedom from atrial arrhythmia was evaluated continuously through 12 months using standard rhythm monitoring for symptomatic episodes and 24-hour Holter at 6 and 12 months. Eighty-two patients (74% male, 51.2% paroxysmal, and 58.5% deep sedation) were treated. PV isolation was achieved in 100% of targeted veins (322/322) with first-pass isolation in 92.2% (297/322). There were 4 primary safety events in 4 patients (4.9%, 4/82); 1 nonembolic stroke due to exacerbated cardiac tamponade secondary to catheter perforation and 3 hemorrhagic vascular access complications. There were no incidences of adverse event fistula, diaphragmatic paralysis, MI, pericarditis, thromboembolism, PV stenosis, transient ischemic attack, or death. Eighty patients (98%) underwent remapping. Optimized PFA cohorts 3, 4, and 5 showed per-patient isolation rates of 60%, 73%, and 81% and per-PV isolation rates of 84%, 90%, and 92%, respectively. One-year freedom from atrial arrhythmia was 80.2% (95% CI, 69.7%-87.4%) for the entire patient sample, including 41 patients who underwent repeat focal PFA with the CENTAURI system at remapping. This study demonstrated that optimization of focal PFA with 3 contact force-sensing, solid-tip ablation catheters resulted in the progressive improvement of PV isolation durability at 3-month remapping and high freedom from atrial arrhythmia survival rates, providing a promising focal PFA treatment option integrated with current ablation workflows.

Relationship between predictive factors and atrial high-rate episodes in heart failure with reduced ejection fraction patients with cardiac implantable electronic devices

Objective Atrial high-rate episodes (AHRE) are atrial tachyarrhythmia episodes detected by implanted cardiac devices, characterised by an atrial rate exceeding 180–190 beats per minute. Recent studies have linked AHRE to the development of atrial fibrillation (AF) and increased stroke risk, especially when episodes last longer than 5–6 min. This study aimed to evaluate the relationship between predictive factors and the occurrence of AHRE in heart failure with reduced ejection fraction (HFrEF) patients with cardiac implantable electronic devices (CIEDs). Methods This single-centre, retrospective study included a cohort of 155 consecutive HFrEF patients with CIEDs, but without a diagnosis of AF, enrolled between January 2023 and December 2023. Patients were stratified based on the presence of AHRE detected during device interrogation. Results The average age of the patients was 54 ± 14 years, and 83.2% of the study population were male. Patients with AHRE had a reduced left ventricular ejection fraction (LVEF) (p = 0.026) and an increased left atrial diameter (p < 0.001) compared to the group without AHRE. Patients with AHRE had elevated levels of creatinine, uric acid, and TSH compared to those without AHRE (p = 0.006, p = 0.021, p = 0.009, respectively). In the univariable logistic regression analysis, LVEF (HR = 0.690, 95% CI = 0.610–0.913, p = 0.013), left atrial diameter (HR = 8.215, 95% CI = 1.557–43.34, p < 0.001), creatinine (HR = 7.369, 95% CI = 1.749–31.05, p = 0.006), uric acid (HR = 1.073, 95% CI = 1.062–1.196, p = 0.020), total cholesterol (HR = 0.989, 95% CI = 0.979–0.999, p = 0.031), and C-reactive protein levels (HR = 1.146, 95% CI = 1.002–1.131, p = 0.047) were identified as independent predictors of AHRE. In multivariable logistic regression analysis, left ventricular ejection fraction (HR = 0.890, 95% CI = 0.795–0.998, p = 0.046), left atrial diameter (HR = 8.215, 95% CI = 1.557–43.34, p < 0.001), and uric acid concentration (HR = 1.650, 95% CI = 1.063–2.561, p = 0.025) were identified as predictors of atrial high-rate events. Conclusion LVEF, left atrial diameter, and uric acid level were found to be independent predictors of AHRE in patients with HFrEF. Identifying AHRE is crucial for risk stratification and guiding therapeutic decisions to improve patient outcome.

Clinical Characteristics and Prevalence of Atrial High-Rate Episodes in Patients With Cardiac Implantable Electronic Devices.

Background Atrial high-rate episodes (AHREs) detected by cardiac implantable electronic devices (CIEDs) are indicative of future clinical atrial fibrillation (AF) and stroke risk. This study aimed to investigate the prevalence of AHREs among Thai patients with CIED implantation and identify associated risk factors. Methods A retrospective observational study enrolled 278 CIEDpatients with AHREs lasting five minutes to 24 hours, with an average atrial rate ≥ 175 bpm, excluding known clinical AF at device implantation. Data were collected from electronic and paper medical records, and statistical analyses included Student's t-test, Mann-Whitney U test, and multivariable logistic regression. Results Of the 278 patients, 52 with pre-existing AF diagnoses were excluded. The median age was 64.86 years, with a balanced gender distribution. Hypertension was observed in 121 (53.54%) patientsand diabetes in 62 (27.43%) patients. Following the designated follow-up period, 58 (20.79%) patients experienced AHREs, and eight (3.53%) developed clinical AF. Multivariable analysis confirmed diabetes as a significant risk factor for AHREs. Conclusion This study underscores the importance of monitoring AHREs for early detection of AF and stroke risk in Thai patients with CIEDs. Diabetes emerged as a significant risk factor, highlighting the need for personalized management strategies in clinical practice.

Catheter Ablation or Surgical Therapy in Severe Atrial Functional Mitral Regurgitation Caused by Long-Standing Persistent Atrial Fibrillation-Propensity Score Analysis.

There is no consensus on the treatment strategy for patients with severe atrial functional mitral regurgitation combined with heart failure (HF), with a lack of comparative studies in patients with long-standing persistent atrial fibrillation and severe atrial functional mitral regurgitation. We aim to compare mitral valve repair combined with the maze procedure with catheter ablation in patients with severe atrial functional mitral regurgitation due to long-standing persistent atrial fibrillation. Patients with severe atrial functional mitral regurgitation and long-standing persistent atrial fibrillation were included in this retrospective cohort study. Surgical patients underwent mitral valve repair combined with the Cox maze procedure, whereas catheter patients underwent catheter radiofrequency ablation. Mortality, atrial fibrillation recurrence, and HF readmission were assessed using overlap propensity score weighting. Then, between 2018 and 2022, we identified 302 patients: 215 in the surgical group and 87 in the catheter group. There were significant differences in the baseline characteristics between groups. The surgical group had lower rates of atrial fibrillation recurrence (P=0.03), HF readmission (P=0.03), and mitral regurgitation grade >2 at discharge (P<0.01) and follow-up (P<0.01). However, there were no significant differences in the 5-year freedom from death (log-rank P=0.87), atrial fibrillation recurrence (log-rank P=0.36), or HF readmission rates (log-rank P=0.18). Compared with surgical patients, the catheter group had higher atrial fibrillation recurrence and HF readmission rates; however, the difference was not significant after overlap propensity score weighting. Although the proportion of patients with significant mitral regurgitation at the last follow-up was higher after catheter ablation, most patients still showed an effective decrease in mitral regurgitation severity.

The Restitution Threshold Index Characterizes the Association Between Atrial Fibrillation Ventricular Rate and Ejection Fraction.

Patients with reduced left ventricular ejection fraction (LVEF) and rate-controlled atrial fibrillation (AF) may improve after restoring sinus rhythm. This may be due to the elimination of the short R-R intervals during AF even when mean heart rate is acceptable. This work aims to evaluate a novel parameter representing the burden of short R-R intervals during AF and its association with reduced LVEF and LVEF recovery after catheter ablation (CA). Patients with persistent AF were prospectively enrolled pre-CA and grouped as having reduced (LVEF≤50%) or preserved LVEF. Sequential R-R intervals on resting Holter monitoring were measured. We sought to define a threshold R-R interval at which the difference in the percentage of short R-R intervals is greatest when comparing patients with reduced and preserved ejection fraction. We termed this threshold the restitution threshold (RT) in the belief that this may be possible to apply as a threshold to identify patients with AF-mediated cardiomyopathy. This percentage burden of intervals shorter than the RT was defined as the restitution threshold index (RTI). The association with reduced LVEF in AF and predicting improvement in LVEF after CA was then evaluated. One hundred four patients were enrolled; 53 (51%) had a reduced LVEF. There was no difference in mean heart rate; however, at an RT of 660ms, the RTI was higher in the reduced LVEF arm (56.1% ± 23.1% vs 39.5% ± 26.0%; P< 0.001). It was an independent predictor of left ventricular systolic dysfunction. The RTI in the reduced LVEF arm had an area under the receiver operating characteristic of 0.74 (95%CI: 0.47-0.95) and positive predictive value of 0.97 for LVEF improvement after CA, which was observed in 39 of 47 (83.0%) participants in sinus rhythm. The RTI in persistent AF was associated with a reduced LVEF, whereas mean heart rate was not. The RTI could be used to predict LVEF improvement after CA.

Accelerated atrial pacing reduces left-heart filling pressure: a combined clinical-computational study.

Accelerated atrial pacing offers potential benefits for patients with heart failure with preserved ejection fraction (HFpEF) and atrial fibrillation (AF), compared with standard lower-rate pacing. The study investigates the relationship between atrial pacing rate and left-heart filling pressure. Seventy-five consecutive patients undergoing catheter ablation for AF underwent assessment of mean left atrial pressure (mLAP) and atrioventricular (AV) conduction delay (PR interval) in sinus rhythm and accelerated atrial pacing with 10 bpm increments up to Wenckebach block. Computer simulations (CircAdapt) of a virtual HFpEF cohort complemented clinical observations and hypothesized the modulating effects of AV coupling and atrial (dys)function. In the study cohort, 49(65%) patients had a high HFpEF likelihood (H2FPEF ≥ 5.0), and 28(37%) an elevated mLAP ≥ 15 mmHg at sinus rhythm. Optimal pacing rates of 100 [70-110]bpm (median [IQR]) significantly reduced mLAP from 12.8 [10.0-17.4]mmHg in sinus rhythm (55 [52-61]bpm) to 10.4 [7.8-14.8]mmHg (P < .001). Conversely, higher pacing rates (130 [110-140]bpm) significantly increased mLAP to 14.7 [11.0-17.8]mmHg (P < .05). PR interval and, hence, AV conduction delay prolonged incrementally with increasing pacing rates. Simulations corroborated these clinical findings, showing mLAP reduction at a moderately increased pacing rate and a subsequent increase at higher rates. Moreover, simulations suggested that mLAP reduction is optimized when AV conduction delay shortens with increasing rate. Accelerated pacing acutely reduces left-heart filling pressure in patients undergoing AF catheter ablation and computer simulations with HFpEF features, suggesting it as a potential therapeutic strategy to alleviate congestion symptoms. Virtual HFpEF patient cohorts hypothesize that AV sequential pacing may further optimize this therapy's beneficial effects.

Abstract 4124369: Mid-term Outcomes of Transcatheter Versus Surgical Aortic Valve Replacement in Low to Moderate Risk Patients with Severe Aortic Stenosis: A Meta-analysis of Randomised Clinical Trials

Background: Several clinical trials have demonstrated non-inferiority of transcatheter aortic valve replacement (TAVR) compared with surgical aortic valve replacement (SAVR) in patients with severe aortic stenosis (AS) and low to intermediate surgical risk. However, mid-term results are still contentious. Question: Is TAVR superior to SAVR in the mid-term in terms of mortality outcomes or adverse cardiovascular events? Methods: We searched Embase, Pubmed and Cochrane databases for RCTs that compared TAVR with SAVR in patients with symptomatic severe AS with a follow-up of at least 4 years. Outcomes of interest were all-cause mortality and disabling stroke. Results: We included six RCTs involving 6,444 patients with severe AS, of whom 3,282 (50.9%) underwent TAVR. There was no difference in mortality from all causes (RR 1.08; 95%CI 0.94-1.25; p=0.30; I 2 =45%) and disabling stroke (RR 0.95; 95%CI 0.75-1.21; p=0.67; I 2 =9%) between groups. In the subgroup analysis, 5-year mortality (RR 1.28; 95%CI 1.10-1.49; I 2 =0%) was higher in the TAVI group. The new pacemaker implantation rate was higher in the TAVI group (RR 2.22; 95%CI 1.42-3.45; p=0.0004 ; I 2 =91%). However, new atrial fibrillation rate was higher in the SAVR group (RR 0.42; 95%CI 0.37-0.49; p=0.00001; I 2 =62%). Conclusion: Mid-term mortality and disabling stroke of patients with severe AS treated with TAVR or SAVR were similar.

Abstract 4136983: Estimating Atrial Fibrillation Rate in Patients Using Artificial Intelligence Referenced to Tissue Action Potentials

Background: Ablation by pulmonary vein isolation (PVI) is the most effective approach to treat atrial fibrillation (AF), but 30-40% of patients may not respond. Studies including the CAPLA trial suggest that ablating sites of rapid activation on the posterior left atrial wall or elsewhere may improve success. However, AF rate is rarely calibrated and, since electrograms often include noise or far field activity, may overestimate rate (underestimate cycle length) at many sites. Hypothesis: We hypothesized that artificial intelligence (AI) algorithms may more accurately indicate local AF rate, by excluding spurious activations referenced to simultaneous monophasic action potential (MAP) recordings, compared to conventional measurements. Methods: We studied N=303 AF patients at ablation (68.2±8.0 years, 17.8% females, 72.9% non-paroxysmal AF). Patients were matched N=229 into development and one quarter (N=74) into hold-out test cohorts. Patients underwent AF mapping using multipolar catheters, and a subset with MAP catheters (MedFact, GmbH). We used the development set to train an AI algorithm to reliably detect AF activations, which we compared in the test cohort to a standard dV/dt approach referenced to adjacent MAPs within 2 mm (N=20 patients) and manually annotated activations (N=64 patients). Results: Fig A shows AF in a 66 year old woman, where dV/dt often marked non-physiological activations within repolarization shown in the adjacent MAP. Conversely, the AI system excluded spurious deflections and better correlated with experts (black). In summary, Fig. B shows that AI provided a higher F1 score than dV/dt compared to MAPs (median[IQR]: 0.86 [0.5 - 1] vs. 0.67 [0.40 - 0.73], p&lt;0.01) and experts (0.89 [0.73 - 1] vs. 0.72 [0.60 - 0.89]], p&lt;0.01). Fig C shows that the AI approach better identified AF cycle length (rate; blue) than standard approaches (green) that substantially underestimate cycle length (p&lt;0.05). Conclusions: In this large registry, a novel AI-based approach more accurately detected AF rates in clinical electrograms, referenced to experts and action potential recordings, than standard approaches which overestimated rate. AI may improve characterization of AF activity within the atria.

MYH6 Variants Are Associated with Atrial Dysfunction in Neonates with Hypoplastic Left Heart Syndrome.

Background: MYH6 variants are the most well-known genetic risk factor (10%) for hypoplastic left heart syndrome (HLHS) and are associated with decreased cardiac transplant-free survival. MYH6 encodes for α-myosin heavy chain (α-MHC), a contractile protein expressed in the neonatal atria. We therefore assessed atrial function in HLHS patients with MYH6 variants. Methods: We performed a retrospective, blinded assessment of pre-stage I atrial function using 2D speckle-tracking echocardiography (2D-STE). Variant carriers were control-matched based on AV valve anatomy, sex, and birth year. Studies were obtained postnatally from awake patients prior to surgical intervention. Right atrial (RA) and right ventricular (RV) strain and strain rate (SR) were measured from the apical four-chamber view. Results: A total of 19 HLHS patients with MYH6 variants had echocardiograms available; 18 were matched to two controls each, and one had a single control. RA active strain (ASct) was decreased in variant carriers (-1.41%, IQR -2.13, -0.25) vs. controls (-3.53%, IQR -5.53, -1.28; p = 0.008). No significant differences were identified in RV strain between the groups. RA reservoir strain (ASr) and conduit strain (AScd) positively correlated with heart rate (HR) in MYH6 variant carriers only (ASr R = 0.499, p = 0.029; AScd R = 0.469, p = 0.043). RV global longitudinal strain (GLS) as well as RV systolic strain (VSs) and strain rate (VSRs) correlated with HR in controls only (GLS R = 0.325, p = 0.050; VSs R = 0.419, p = 0.010; VSRs R = 0.410, p = 0.012). Conclusions: We identified functional consequences associated with MYH6 variants, a known risk factor for poor outcomes in HLHS. MYH6 variant carriers exhibit impaired RA contractility despite there being no differences in RV function between variant carriers and controls. MYH6 variants are also associated with an ineffective RA reservoir and conduit function at high heart rates, despite preserved RV diastolic function. RA dysfunction and reduced atrial "kick" may therefore be a significant contributor to RV failure and worse clinical outcomes in HLHS patients with MYH6 variants.

Pulsed Field Ablation in Atrial Fibrillation: Initial Experience of the Efficacy and Safety in Pulmonary Vein Isolation and Beyond.

Regional differences in pulsed field ablation (PFA) adoption for pulmonary vein isolation (PVI) with additional posterior wall ablation (PWA) in Asia remains unknown. We hereby report our experience on the safety and efficacy of PFA in AF ablation. Consecutive AF patients who underwent PFA from September 2022 to January 2024 were included. The primary efficacy endpoint was freedom from atrial arrhythmia recurrence after a 90-day blanking period at 12 months. Safety endpoints included 30 days of all-cause death, cardiac tamponade, stroke, myocardial infarction, and heart failure hospitalization. One hundred and one (72.3% males, 79.2% pAF) patients underwent PFA for AF. Thirty-one (30.7%) had structural heart disease with mean LVEF of 57.4 ± 8.1% and CHA2DS2-VASc score of 1.4 ± 1.3. Twenty-nine (28.7%) underwent additional PWA (PVI + PWA) using PFA. PWA was acutely successful in all patients. Patients who underwent PWA were more likely to have persistent AF and require general anesthesia and electroanatomic mapping (all p < 0.05). Total PFA applications for PVI, LA dwell time, procedural time, and fluoroscopy time were similar between the PVI-only and PVI + PWA groups (all p > 0.05). The 1-year atrial arrhythmia recurrence rates were 10% for pAF and 21% for the persistent AF group. The primary efficacy endpoint was not significantly different between the PVI-only and PVI+PWA groups (12-month KM estimates 90.3% [95% CI, 83.3-97.3] and 82.8% [95% CI, 68.1-97.4], respectively). There were no complications related to PFA use. PFA can be safely, effectively, and efficiently adopted for AF ablation. Additional PWA, if pursued, had similar procedural metrics to the PVI-only strategy without increased complications.

Normal ranges of left atrial phasic strains and strain rates by 2D speckle-tracking echocardiography in pediatrics: a systematic review and meta-analysis

Establishing normal values of left atrial (LA) phasic strains and strain rates is essential for distinguishing between normal and abnormal functions, determining the degree of abnormality, and understanding the clinical significance of reported values in pediatrics. This meta-analysis aimed to establish normal values of two-dimensional speckle-tracking echocardiography (2DSTE)-derived LA phasic strains and strain rates in the pediatric population and identify the sources of inter-study heterogeneity for these values. A comprehensive search of PubMed, Scopus, and Embase databases was conducted using keywords such as “left atrial/left atrium,” “strain/speckle/deformation,” and “echocardiography” combined with pediatric age categories. Inclusion criteria comprised English-language human studies involving healthy subjects under 18 years of age. Subjects were categorized as neonates (up to 1 month), infants (1–12 months), and children (1–18 years). A random-effects model was applied to determine 2DSTE-derived LA strains and strain rates, and a meta-regression analysis was performed to investigate inter-study heterogeneity. Our analysis included 17 studies involving 1448 healthy subjects. For children, the mean values of LA strains during the reservoir, conduit, and contraction phases were 47.3% (95% CI 42.5–52.1%), 32.8% (95% CI 27.8–37.8%), and 12% (95% CI 10.0–14.1%), respectively. The mean values for LA strain rates were 2.4 s−1 (95% CI 1.1–3.8 s−1), 4.3 s−1 (95% CI 0.6–8.0 s−1), and 2.4 s−1 (95% CI 0.4–4.5 s−1), respectively. Inter-study heterogeneity for 2DSTE-derived LA phasic strains and strain rates was attributed to factors such as the number of study participants, publication year, software utilized, gating methods, the number of analyzed segments, the geographical region of the study, and heart rate. This study established the normal range of 2DSTE-derived LA phasic strains and strain rates. Additionally, inter-study heterogeneity was found to be influenced by various demographic, physiologic, and methodological factors.

Identifying at-risk patients for atrial high-rate episodes by machine learning

Abstract Background Current evidence suggests that atrial high rate episodes (AHRE)/subclinical atrial fibrillation (AF) are associated with increasing risk of clinical AF, and subsequently, ischaemic stroke and other adverse cardiovascular events. Purpose To construct a high-performance model by machine learning (ML) for the prediction of AHRE detected by a cardiac implantable electronic device (CIED) capable of atrial sensing in a European cohort. Methods We utilized data from a prospective cohort of patients with CIED. AHRE was defined as an episode lasting at least 5 minutes with atrial rate ≥ 175 beats per minute. We divided the cohort into training and internal validation cohorts in 7:3 and used 5-fold cross-validation in the training cohort to assess model performance and prevent model overfitting. Pre-selected features were imported into eight common ML algorithms to predict AHRE, including light gradient boosting machine (LightGBM), random forest (RF), logistic regression, support vector machine, multiple perceptron, eXtreme gradient boosting machine (XGBoost), Gaussian naïve Bayes, and K nearest neighbours. The importance ranking of the features was interpreted by calculating the SHapley Additive exPlanationation (SHAP) value for each feature within the optimal model. Results A total of 500 consecutive patients with CIEDs (mean age 70.2±13.3; 39.2% female) were included. Of these, 164 patients (32.8%) were found to have AHRE. Among all ML models, RF was the best performing model, which obtained the highest AUC (0.738), recall (0.673) and F1-score (0.584) in the internal validation cohort. The results of SHAP showed that antiplatelet, statin, age, white blood cell count, and cardiomyopathy were the first five important features, indicating that the RF model had good interpretability and reliability. Conclusion Our study is the first to demonstrate in a European cohort the effectiveness and feasibility of ML algorithms in predicting AHRE in patients detected by CIEDs. The best RF models require further external validation to assess generalizability to other cohorts.Figure 1Figure 2

No improvement in atrial arrhythmia rates in patients on baroreflex activation therapy

Abstract Background Atrial arrhythmias encompass a wide range of abnormal cardiac rhythms including atrial fibrillation, atrial flutter, and atrial tachycardia. Patients with heart failure with reduced ejection fraction (HFrEF) have increased risk of atrial arrhythmias, ultimately leading to increased morbidity. Baroreflex Activation Therapy (BAT) employs an implantable device to increase parasympathetic nervous system activity by stimulating the carotid baroreceptors thereby reducing afterload and heart failure symptoms. In our prior study, BAT therapy has been shown to reduce hospitalization rates in patients with HFrEF. However, the effects of BAT on atrial arrhythmia has never been studied. Objective In this study, we analyzed the effects of BAT on atrial arrhythmia rates in patients with HFrEF. Methods Patients with HFrEF with BAT therapy for at least 12-months at a hospital were retrospectively studied. Inclusion criteria includes implantable cardioverter-defibrillator (ICD) placement of at least 12-months pre- and post-BAT therapy. Additionally, patients diagnosed with atrial arrhythmias prior to the study timeline were excluded. Atrial arrhythmia rates 6 and 12-months pre-BAT therapy and 6 and 12-months post-BAT therapy were compared. Atrial arrhythmia episodes were recorded through ICD interrogation every 1-3 months in the clinic. Of the 31 identified patients on BAT therapy, 11 patients fit the inclusion criteria. For the 11 patients in the study, 3 identified as female and 8 identified as male, 6 identified as white, 4 identified as Hispanic, and 1 identified as African-American with a mean age of 59.8 ± 17.4 years. The average left ventricular ejection fraction pre-BAT therapy was 23.8 ± 10.8%. Results The mean average atrial arrhythmia rates for 6-month pre-BAT therapy and 6-month post-BAT therapy were 0.12/month ± 0.40 and 1.32/month ± 2.76 respectively (p=0.18), suggesting no differences in atrial arrhythmia rates at 6-months with BAT therapy. The mean average atrial arrhythmia rates for 12-month pre-BAT therapy and 12-month post-BAT therapy were 0.11/month ± 0.35 and 2.40/month ± 5.84 respectively (p=0.22), suggesting no differences in atrial arrhythmia rates at 12-months with BAT therapy. Conclusion Although BAT therapy has been shown to decrease hospitalization rates, BAT therapy is not associated with decreased atrial arrhythmia rates at 6 months and 12 months.

Atrial rates during treated ventricular tachycardia in patients with implantable cardioverter defibrillators: clinical implications of a vagal sinus node response

Abstract Introduction Autonomic tone plays an important role in the genesis and sustenance of ventricular tachycardia (VT). Whilst sympathetic hyperactivity is an established driver of ventricular arrhythmias, sinus node response during VT varies broadly between patients, and can be paradoxical. Purpose We hypothesized that device-detected changes in sinus node rate could be an important surrogate of the autonomic response to VT, and may exert significant – and potentially modifiable – haemodynamic consequences independent of ventricular activity. Methods Device electrograms were analysed from consecutive patients with dual chamber implantable cardioverter defibrillators (ICDs) requiring anti-tachycardia pacing (ATP) or defibrillation for sustained monomorphic VT. Atrial rates were measured before VT onset (‘baseline’) and again at the point of detection by the device. Sinus node response was characterized as ‘stable’ (atrial rate remained within 10% of baseline), ‘sympathetic’ (atrial rate increased &amp;gt;10%) or ‘vagal’ (atrial rate decreased &amp;gt;10%). Patients who did not maintain ventriculoatrial dissociation or who presented in atrial tachyarrhythmia were excluded. Symptoms and electrical response to ICD therapies were recorded. Results 172 treated episodes of VT were included from 97 patients (median age: 69 years, 65% male, 31% ischaemic cardiomyopathy, median ventricular rate: 205bpm, median ejection fraction: 30%). Sinus node response was stable in 55%, sympathetic in 24% and vagal in 21%. A vagal response was associated with ATP-refractory VT (OR: 2.2 (1.1-4.8) p=0.03) and, when adjusting for ventricular rate, was independently associated with symptoms of presyncope or syncope (adjusted OR: 6 (2.7-13.7), p&amp;lt;0.0001). Conclusions This preliminary analysis suggests that a vagal sinus node response during VT is associated with adverse outcomes in ICD patients. Vagolytic therapy has recently been demonstrated to improve haemodynamic tolerance during VT ablation; whether supportive atrial pacing during VT could mitigate symptoms and potentiate arrhythmia termination in ICD patients warrants further exploration. Figure 1: Change in sinus node rate during sustained monomorphic ventricular tachycardia in patients with dual chamber ICDs, stratified by the occurrence of presyncopal symptoms or syncopeFigure 1

Incidence of silent brain injury in pacemaker implanted patients with atrial high-speed episodes (AHRE)

Abstract Purpose Atrial high rate episodes (AHRE) are tachyarrhythmia attacks that can be detected by implantable cardiac devices. In the European Society of Cardiology (ESC) 2020 AF guideline, AHRE is defined as ≥ 175 bpm for the device-programmed rate criterion and ≥ 5 minutes for the duration criterion. AHRE has been shown to be one of the predisposing factors of AF and stroke. However, the relationship between AHRE and SBI has not been clarified yet. Neuron spesific enolase (NSE) is a valid biomarker for quantifying the volume of neuronal damage. In this study, we aimed to evaluate the incidence of silent brain injury (SBI), defined as elevated NSE levels in AHRE detected patients. Method Between January 2021 and June 2022, 80 patients who underwent routine pacemaker control, met the inclusion and exclusion criteria, and had AHRE detected in their permanent pacemaker records were included in a university faculty of medicine cardiology arrhythmia polyclinic. For the control group, patients who had a permanent pacemaker and did not have AHRE or any other arrhythmia were included. Of patients with AHRE detected in the last 6 months and those who had an AHRE attack within the last 72 hours were examined. Results Individuals included in the study were divided into subgroups according to AHRE duration. Group 1 (non-AHRE) 80 (50.0%), Group 2 (AHRE lasting &amp;lt;5 min) 24 (15.0%), Group 3 (≥5 min - &amp;lt;1h) 33 (20.6%), 19 (11.9%) patients in Group 4 (lasting ≥1 h - &amp;lt;24 h) and 4 (2.5%) patients in Group 5 (lasting ≥24 h). There was a statistically significant difference in NSE median values between groups (p=&amp;lt;0.001). In Mann Whitney U test with Bonferronni correction, the median values of all other groups were significantly different from each other (p=&amp;lt;0.001). In the correlational analysis, there was a statistically significant positive relationship between AHRE duration and NSE values (r=0.842; p=&amp;lt;0.001). Additionally, there was correlation between AHRE duration and age (r=0.235; p=0.036), CHA2DS2-VASc score (r=0.226, p=0.044) and LA diameter (r=0.300; p=0.007). NSE levels were positively correlated with AHRE duration (r=0.842; p=&amp;lt;0.001) and LA diameter (r=0.242; p=0.030). Conclusion AHRE duration was longer in patients with advanced age, increased CHA2DS2-VASc score, and increased LA diameter. This may play a role in explaining the underlying pathophysiological changes in AHRE before AF develops. Since NSE levels are related to LA diameter as well as AHRE duration, it can be thought that increasing LA diameter contributes to the development of thrombus.

Atrial fibrillation recurrence rates in patients with transthyretin cardiac amyloidosis undergoing pulmonary vein isolation: a comparative retrospective study with propensity score matching

Abstract Background Atrial fibrillation (AF) affects up to 70% of individuals diagnosed with transthyretin cardiac amyloidosis (ATTR CA) [1]. AF ablation is frequently considered in the management of these patients, but there is a lack of data about outcomes of the procedure in this population. Purpose This study aims to evaluate AF recurrence rates and long-term AF recurrence-free survival in patients with ATTR CA undergoing pulmonary vein isolation (PVI). Methods A single-center retrospective study was conducted, including all patients diagnosed with ATTR CA who underwent PVI from 2016 to 2023. We compared patients with amyloidosis (cases) to those without (controls), employing propensity score matching for age, gender, AF type (paroxysmal vs. persistent), BMI, diabetes, arterial hypertension diagnosis, antiarrhythmic drug therapy post-index ablation, and left atrium (LA) volume assessed by 3D rotational angiography (3DRA). Results 16 patients with CA were matched to 16 patients without (32 patients in total). After matching, the populations demonstrated comparable baseline characteristics (figure 1). The study consistently revealed a higher AF recurrence rate, after PVI, in the CA group (81.3%) compared to the control group (37.5%) at the last follow-up (p-value 0.01) (median follow-up 1255 ± 1055 days in CA and 1491 ± 464 days in control group), as well as a significantly lower long-term AF-recurrence free survival (log-rank p = 0.01 – figure 2). Additionally, the recurrence rate at 1-year post-procedure was 56.25% in the CA group and 18.75% in the control group (p-value 0.03). Conclusions Pulmonary vein isolation remains a viable treatment option for individuals with ATTR CA. However, it proved less effective (or less durable) than in the general population without the disease, both at 1-year follow-up and for longer periods, as shown also with recurrence-free survival rate. Further studies are warranted to determine the optimal treatment strategy for this specific population.Baseline Characteristics fig. 1Kaplan Meyer fig. 2

Lesion size index-guided radiofrequency catheter ablation using an impedance-based three-dimensional mapping system to treat sustained atrial tachycardia in a horse.

Sustained atrial tachycardia at an atrial rate of 191/min on the surface ECG was detected in a 6-year-old Warmblood mare. The vectorcardiogram obtained from a 12-lead ECG suggested a caudo-dorsal right atrial origin of the arrhythmia. Impedance-based three-dimensional electro-anatomical mapping, using the EnSite™ Precision Cardiac Mapping System revealed a clockwise macro-reentry around a line of conduction block in the caudomedial right atrium. Ten radiofrequency applications were applied to isolate the caudal vena cava myocardial sleeves at a power of 35 W and mean contact force of 14 ± 3 g until a lesion size index of 6 was reached. Sinus rhythm was restored at the first energy application. Successful isolation was confirmed by demonstrating entrance and exit block. Holter monitoring 5 days post-ablation revealed no abnormalities. To date, 9 months after treatment, no recurrence has been observed. The use of lesion size index-guided ablation and isolation of the arrhythmogenic substrate in the caudal vena cava may minimise the risk of recurrence.

Performance of the novel ANTWERP score in predicting heart function improvement after atrial fibrillation ablation in Asian patients with heart failure.

Previous research has demonstrated that atrial fibrillation (AF) ablation improves heart function variably among patients. We proposed that the ANTWERP score, which was validated in a European group of patients with low left ventricular ejection fraction (LVEF) who had AF ablation, would be valid in an Asian group as well. The purpose of the study is to examine how well a new scoring system (the ANTWERP score) can predict heart function improvement after atrial fibrillation ablation in Asian patients with heart failure. A retrospective review was conducted on patients (n = 84) undergoing AF ablation between January 2019 and June 2022. Initial diagnoses for impaired LV systolic function were confirmed by echocardiography. Patients meeting the "2021 Universal Definition of HF" criteria for LVEF recovery were classified as "responders." Similarities were observed between responders and nonresponders regarding comorbidities, AF type, and LVEF, except for the left ventricular internal diameter in diastole. A higher percentage of responders had an ANTWERP score ≤2 (87.8%) compared to those with a score >2 (55.6%). LVEF improvement was notably higher in the former group (+14.8% vs. +9.4%, p = .043). Atrial reverse remodeling and recurrent atrial arrhythmia rates were similar across groups. The conclusion of the study was that the ANTWERP score effectively predicted LVEF improvement after atrial fibrillation ablation in the Asian population and that this scoring system could be used to guide clinical decisions and prognosis prediction.

The negative chronotropic effects of (±)-propranolol and (±)-4-NO2-propranolol in the rat isolated right atrium are due to blockade of the 6-nitrodopamine receptor.

The positive chronotropic action induced by 6-nitrodopamine (6-ND) is selectively blocked by β1-adrenoceptor antagonists at concentrations that do not affect the positive chronotropic effect induced by dopamine, noradrenaline, and adrenaline. Here, the effects of ( ±)-propranolol, ( ±)-4-NO2-propranolol, and ( ±)-7-NO2-propranolol were investigated in the rat isolated right atrium. The atrium was mounted in glass chambers containing gassed (95%O2:5%CO2) and warmed (37°C) Krebs-Henseleit's solution, and the isometric tension registered (PowerLab system). ( ±)-Propranolol, ( ±)-4-NO2-propranolol, and ( ±)-7-NO2-propranolol caused concentration-dependent falls in the spontaneous atrial frequency (pIC50: 4.80 ± 0.10, 4.64 ± 0.10, and 4.95 ± 0.10, respectively). The calculated pA2 values for ( ±)-propranolol, ( ±)-4-NO2-propranolol, and ( ±)-7-NO2-propranol on noradrenaline-induced positive chronotropism were 8.44 ± 0.08, 6.41 ± 0.07, and 9.21 ± 0.29, respectively. The positive chronotropism induced by 6-ND (10pM) was blocked by ( ±)-propranolol (1µM) and ( ±)-4-NO2-propranolol (30nM), whereas ( ±)-7-NO2-propranolol (1µM) had no effect on 6-ND-induced responses. The pIC50 of ( ±)-propranolol, ( ±)-4-NO2-propranolol, and ( ±)-7-NO2-propranolol were significantly shifted to the right in L-NAME-treated atria. The discrepancy between pA2 values of ( ±)-propranolol and its respective pIC50 indicates that the falls in atrial rate induced by ( ±)-propranolol should not be attributed to b-adrenergic antagonism. The reduced chronotropism by ( ±)-propranolol was unaffected by the sodium channel inhibitors tetrodotoxin and lidocaine but that was abolished in atria pre-treated with ( ±)-4-NO2-propranolol. The finding that ( ±)-propranolol reduces spontaneous atrial rate only in concentrations that affect 6-ND-induced positive chronotropism confirms the role of this catecholamine as an endogenous modulator of heart chronotropism. ( ±)-4-NO2-Propranolol behaves as a selective antagonist of 6-ND in the rat isolated atrium.