Age as a Critical Determinant of Atrial Fibrillation: A Two-sided Relationship

Perioperative Risk Factors for New-Onset Perioperative Atrial Fibrillation Following Minimally Invasive Esophagectomy: A Single-Center Retrospective Study

BACKGROUND

Atrial fibrillation (AF) is the most common cardiovascular complication following esophagectomy. The aim of this study was to identify the risk factors for new-onset perioperative (intraoperative and/or postoperative) AF in patients undergoing minimally invasive esophagectomy (MIE).

METHODS

This study used a single-center retrospective design and included 814 patients who were diagnosed with esophageal cancer and underwent McKeown MIE. The patients' characteristics and perioperative data were collected from the electronic medical records and analyzed.

RESULTS

New-onset perioperative AF occurred in 5.3% of the patients (43/814), with 4 patients developing intraoperative AF and 39 patients developing postoperative AF. Multivariate logistic regression analysis identified age (odds ratio [OR] 1.081 and p < 0.001), history of coronary heart disease (OR 4.269 and p < 0.001), and intraoperative blood loss (OR 1.004 and p = 0.008) as independent risk factors for perioperative AF following MIE. The area under the receiver operating characteristic curve for the multivariate logistic regression model was 0.735 (95% confidence interval 0.660-0.810). The incidences of postoperative pulmonary complications and anastomotic leakage were significantly higher in patients with perioperative AF than in those without perioperative AF (both p = 0.011). Patients with perioperative AF also had a longer hospital stay (15.0 vs. 13.0 days and p = 0.034).

CONCLUSIONS

Increasing age, history of coronary heart disease, and intraoperative blood loss were associated with new-onset perioperative AF following MIE. However, the impact of intraoperative blood loss on AF is likely to be of marginal clinical relevance. The observed AF fell below projected estimates, resulting in inadequate statistical power for the study outcomes.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (No. ChiCTR2300074003; date of registration, 27/07/2023).

β-Hydroxybutyrate and Citrate Synthase as Potential Diagnostic Biomarkers in Aging-Related Atrial Fibrillation

The incidence of atrial fibrillation (AF) increases with age; however, the precise mechanisms by which aging elevates AF risk and the effective biomarkers for managing AF in elderly patients remain unclear. We analyzed plasma samples from 100 elderly AF patients, 100 young and 100 elderly patients without atrial fibrillation (NAF), along with left atrial tissues obtained from both AF and NAF patients following valve replacement. Our findings indicate reduced levels of β-OHB and citrate synthase (CS) activity in elderly AF patients compared to their NAF counterparts. Statistical analysis revealed a protective association between β-OHB and CS activity concerning the occurrence of elderly AF. Furthermore, atrial tissues from elderly AF patients exhibited mitochondrial dysfunction, structural remodeling, and low-voltage areas. These results suggest that dysregulation of β-OHB levels and CS activity may contribute to aging-related AF by affecting mitochondrial function and atrial remodeling, highlighting their potential as diagnostic biomarkers for this condition.

Flecainide to Prevent Atrial Arrhythmia After Patent Foramen Ovale Closure: AFLOAT Study, A Randomized Clinical Trial

BACKGROUND

The real incidence of atrial arrhythmia (AA) after patent foramen ovale (PFO) closure and whether this complication can be prevented remain unknown. We assessed whether flecainide is effective to prevent AA during the first 3 months after PFO closure, and whether 6 months of treatment with flecainide is more effective than 3 months to prevent AA after PFO closure.

METHODS

AFLOAT (Assessment of Flecainide to Lower the Patent Foramen Ovale Closure Risk of Atrial Fibrillation or Tachycardia Trial) is a prospective, multicentre, randomized, open-label, superiority trial with a blind evaluation of all the end points (PROBE [Prospective Randomized Open, Blinded End Point] design). Patients were randomized in a 1:1:1 ratio after PFO closure to receive flecainide (150 mg once daily in a sustained-release dose) for 3 months, flecainide (150 mg once daily in a sustained-release dose) for 6 months, or no additional treatment (standard of care) for 6 months. The primary end point was the percentage of patients with at least 1 episode of AA (≥30 seconds) recorded within 3 months after PFO closure on long-term monitoring with an insertable cardiac monitor. The secondary end point was the percentage of patients with at least 1 episode of AA (≥30 seconds) recorded with insertable cardiac monitor during the 3- to 6-month period after PFO closure.

RESULTS

A total of 186 patients were included (mean age, 54 years; 68.8% men) and AA (≥30 seconds) occurred in 53 patients (28.5%) during the 6-month follow-up; 86.8% of these AA events occurred in the first month after PFO closure. The primary outcome occurred in 33 of 123 (26.8%) and 16 of 63 (25.4%) patients receiving flecainide for at least 3 months or standard of care, respectively (risk difference, 1.4% [95% CI, -12.9% to 13.8%]; NS). The secondary end point occurred in 3 of 60 (5.0%), 4 of 63 (6.3%), and 5 of 63 (7.9%) patients receiving flecainide for 6 months, for 3 months, or standard of care, respectively (risk difference, -2.9% [95% CI, -12.7% to 6.9%], and risk difference, -1.6% [95% CI, -11.8% to 8.6%], respectively).

CONCLUSIONS

In the first 6 months after successful PFO closure, AA (≥30 seconds) occurred in 28.5% of cases, mostly in the first month after the procedure. Flecainide did not prevent AA after PFO closure.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT05213104.

Diagnosis to Ablation in Persistent AF: Any Time Can Be a Good Time to Ablate

BACKGROUND

Nonrandomized data suggest that longer diagnosis-to-ablation time (DAT) is associated with poorer outcomes; however, a recent randomized trial found no difference in recurrences when ablation was delayed by 12 months.

OBJECTIVES

This study sought to assess the impact of DAT on atrial fibrillation (AF) recurrence in patients undergoing catheter ablation for persistent AF.

METHODS

CAPLA (Effect of Catheter Ablation Using Pulmonary Vein Isolation With vs Without Posterior Left Atrial Wall Isolation on Atrial Arrhythmia Recurrence in Patients With Persistent Atrial Fibrillation: The CAPLA randomized clinical trial) was a multicenter trial that randomized patients with persistent AF to pulmonary vein isolation + posterior wall isolation or pulmonary vein isolation alone. Follow-up was 12 months. Outcomes were assessed after a 3-month blanking period.

RESULTS

Median DAT in the 334 patients was 28 months (Q1-Q3: 12-66 months). Patients were divided into quartile groups: Q1 was DAT 0 to 12 months (n = 84, median DAT 7 months), Q2 was DAT 13 to 28 months (n = 85, median DAT 20 months), Q3 was DAT 29 to 66 months (n = 84, median DAT 41 months), and Q4 was DAT ≥67 months (n = 81, median DAT 119 months). AF recurrence rate was 36.9% for Q1, 44.7% for Q2, 47.6% for Q3, and 56.8% for Q4 (P = 0.082). On multivariable analysis, DAT Q4 was the only factor significantly associated with risk of recurrence (HR: 1.607; 95% CI: 1.005-2.570; P = 0.048). Median AF burden was 0% (Q1-Q3: 0%-0.47%) in Q1 and 0.33% (Q1-Q3: 0%-4.6%) in Q4 (P = 0.002). Quality of life (assessed by the Atrial Fibrillation Effect on Quality-of-Life questionnaire) improved markedly in all quartiles (Q1: Δ28.8 ± 24, Q2: Δ24.4 ± 23.4, Q3: Δ21.7 ± 26.6, Q4: Δ24.6 ± 21.4; P = 0.331).

CONCLUSIONS

In a cohort of patients with persistent AF undergoing ablation in a prospective trial with standardized entry criteria and intensive electrocardiogram monitoring, those with shorter DAT had lower rates of AF recurrence. However, differences were modest, and all quartiles demonstrated very low AF burden and improvements in quality of life.

The role of cellular senescence in profibrillatory atrial remodelling associated with cardiac pathology

AIMS

Cellular senescence is a stress-related or aging response believed to contribute to many cardiac conditions; however, its role in atrial fibrillation (AF) is unknown. Age is the single most important determinant of the risk of AF. The present study was designed to (i) evaluate AF susceptibility and senescence marker expression in rat models of aging and myocardial infarction (MI), (ii) study the effect of reducing senescent-cell burden with senolytic therapy on the atrial substrate in MI rats, and (iii) assess senescence markers in human atrial tissue as a function of age and the presence of AF.

METHODS AND RESULTS

AF susceptibility was studied with programmed electrical stimulation. Gene and protein expression was evaluated by immunoblot or immunofluorescence (protein) and digital polymerase chain reaction (PCR) or reverse transcriptase quantitative PCR (messenger RNA). A previously validated senolytic combination, dasatinib and quercetin, (D+Q; or corresponding vehicle) was administered from the time of sham or MI surgery through 28 days later. Experiments were performed blinded to treatment assignment. Burst pacing-induced AF was seen in 100% of aged (18-month old) rats, 87.5% of young MI rats, and 10% of young control (3-month old) rats (P ≤ 0.001 vs. each). Conduction velocity was slower in aged [both left atrium (LA) and right atrium (RA)] and young MI (LA) rats vs. young control rats (P ≤ 0.001 vs. each). Atrial fibrosis was greater in aged (LA and RA) and young MI (LA) vs. young control rats (P < 0.05 for each). Senolytic therapy reduced AF inducibility in MI rats (from 8/9 rats, 89% in MI vehicle, to 0/9 rats, 0% in MI D + Q, P < 0.001) and attenuated LA fibrosis. Double staining suggested that D + Q acts by clearing senescent myofibroblasts and endothelial cells. In human atria, senescence markers were upregulated in older (≥70 years) and long-standing AF patients vs. individuals ≤60 and sinus rhythm controls, respectively.

CONCLUSION

Our results point to a potentially significant role of cellular senescence in AF pathophysiology. Modulating cell senescence might provide a basis for novel therapeutic approaches to AF.

Aging and atrial fibrillation: A vicious circle

Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia observed in clinical practice. Its prevalence increases dramatically with advancing age. This review article discusses the recent advances in studies investigating the relationship between aging and AF and the possible underlying mechanisms.

Tongyang Huoxue decoction (TYHX) ameliorating hypoxia/reoxygenation-induced disequilibrium of calcium homeostasis via regulating β-tubulin in rabbit sinoatrial node cells

ETHNOPHARMACOLOGICAL RELEVANCE

β-tubulin is a skeletal protein of sinoatrial node cells (SANCs) that maintains the physiological structure of SANCs and inhibits calcium overload. Tongyang Huoxue decoction (TYHX) is widely used to treat sick sinus syndrome (SSS) owing to its effects on calcium channels regulation and SANCs protection.

AIM OF THE STUDY

This study focuses on the mechanism of TYHX in improving the hypoxia/reoxygenation (H/R)-induced disequilibrium of calcium homeostasis in SANCs via regulating β-tubulin.

MATERIALS AND METHODS

Real-Time PCR (RT-PCR) and Western Blot were adopted to detect the mRNA and protein expression levels of calcium channel regulatory molecules. Laser confocal method was employed to examine β-tubulin structure and fluorescence expression levels in SANCs, as well as calcium wave and calcium release levels.

RESULTS

It was found that the fluorescence expression level decreased and the β-tubulin structure of SANCs was damaged after H/R treatment. The mRNA and protein expression levels of SERCA2a/CaV1.3/NCX and β-tubulin decreased, while the mRNA and protein expression of RyR2 increased. The results of calcium wave and calcium transient experiments showed that the fluorescence expression level of Ca2+ increased and calcium overload occurred in SANCs. After treatment with TYHX, the mRNA and protein expression levels of SERCA2a/CaV1.3/NCX and β-tubulin increased, while the mRNA and protein expression levels of RyR2 decreased and the cell structure was restored. Interestingly, the regulation of TYHX on calcium homeostasis was further enhanced after Ad-β-tubulin treatment and counteracted after siRNA-β-tubulin treatment. These results suggest that TYHX could maintain calcium homeostasis via regulating β-tubulin, thus protecting against H/R-induced SANCs injury, which may be a new target for SSS treatment.

Left Atrial Strain to Predict Postoperative Atrial Fibrillation in Patients Undergoing Coronary Artery Bypass Grafting

BACKGROUND

Postoperative atrial fibrillation (POAF) is a common complication after cardiac surgery being associated with poorer outcomes. Revealing before the operation of left atrial subtle structural/functional abnormalities may help to identify patients at increased risk of POAF. We investigated the role of left atrial strain parameters by preoperative speckle tracking echocardiography as independent predictors of POAF in patients undergoing coronary artery bypass graft.

METHODS

Consecutive patients undergoing isolated coronary artery bypass graft were prospectively enrolled at three Italian centers. All patients underwent transthoracic echocardiography before the operation. The occurrence of POAF up to discharge was monitored.

RESULTS

Overall, a total of 310 patients were included. POAF was demonstrated in 103 patients (33%). At receiver operating characteristic curve analysis, lower global peak atrial longitudinal strain (PALS) values significantly predicted the risk of POAF (area under the curve, 0.74; P<0.001). The optimal cutoff value for the arrhythmia prediction was a global PALS value <28%, with a specificity of 86% and a sensitivity of 36%. The incidence of POAF was 51% in patients with global PALS <28% versus 14% in those with PALS ≥28% (P<0.001), with a POAF-free survival at Kaplan-Meier analysis of 45.4% and 85.7%, respectively (P<0.001). At multivariate analysis, a global PALS <28% carried a 3.6-fold higher risk of POAF (hazard ratio, 3.6 [95% CI, 2.2-5.9]; P<0.001). The risk increase was even higher when PALS <28% was associated with age ≥70 years (adjusted hazard ratio, 11.2 [4.7-26.6], P<0.001).

CONCLUSIONS

A presurgery global PALS <28% is a specific parameter to stratify patients at increased risk of POAF after coronary artery bypass graft. This assessment can be useful to identify patients at higher arrhythmic risk in whom perioperative preventive strategies and stricter monitoring aimed at early diagnosing and treating POAF may be applied.

Cellular Senescence in Cardiovascular Diseases: From Pathogenesis to Therapeutic Challenges

Cellular senescence (CS), classically considered a stable cell cycle withdrawal, is hallmarked by a progressive decrease in cell growth, differentiation, and biological activities. Senescent cells (SNCs) display a complicated senescence-associated secretory phenotype (SASP), encompassing a variety of pro-inflammatory factors that exert influence on the biology of both the cell and surrounding tissue. Among global mortality causes, cardiovascular diseases (CVDs) stand out, significantly impacting the living quality and functional abilities of patients. Recent data suggest the accumulation of SNCs in aged or diseased cardiovascular systems, suggesting their potential role in impairing cardiovascular function. CS operates as a double-edged sword: while it can stimulate the restoration of organs under physiological conditions, it can also participate in organ and tissue dysfunction and pave the way for multiple chronic diseases under pathological states. This review explores the mechanisms that underlie CS and delves into the distinctive features that characterize SNCs. Furthermore, we describe the involvement of SNCs in the progression of CVDs. Finally, the study provides a summary of emerging interventions that either promote or suppress senescence and discusses their therapeutic potential in CVDs.

Impact of 14 Days of Bed Rest in Older Adults and an Exercise Countermeasure on Body Composition, Muscle Strength, and Cardiovascular Function: Canadian Space Agency Standard Measures

INTRODUCTION

Head-down bed rest (HDBR) has long been used as an analog to microgravity, and it also enables studying the changes occurring with aging. Exercise is the most effective countermeasure for the deleterious effects of inactivity. The aim of this study was to investigate the efficacy of an exercise countermeasure in healthy older participants on attenuating musculoskeletal deconditioning, cardiovascular fitness level, and muscle strength during 14 days of HDBR as part of the standard measures of the Canadian Space Agency.

METHODS

Twenty-three participants (12 males and 11 females), aged 55-65 years, were admitted for a 26-day inpatient stay at the McGill University Health Centre. After 5 days of baseline assessment tests, they underwent 14 days of continuous HDBR followed by 7 days of recovery with repeated tests. Participants were randomized to passive physiotherapy or an exercise countermeasure during the HDBR period consisting of 3 sessions per day of either high-intensity interval training (HIIT) or low-intensity cycling or strength exercises for the lower and upper body. Peak aerobic power (V̇O2peak) was determined using indirect calorimetry. Body composition was assessed by dual-energy X-ray absorptiometry, and several muscle group strengths were evaluated using an adjustable chair dynamometer. A vertical jump was used to assess whole-body power output, and a tilt test was used to measure cardiovascular and orthostatic challenges. Additionally, changes in various blood parameters were measured as well as the effects of exercise countermeasure on these measurements.

RESULTS

There were no differences at baseline in main characteristics between the control and exercise groups. The exercise group maintained V̇O2peak levels similar to baseline, whereas it decreased in the control group following 14 days of HDBR. Body weight significantly decreased in both groups. Total and leg lean masses decreased in both groups. However, total body fat mass decreased only in the exercise group. Isometric and isokinetic knee extension muscle strength were significantly reduced in both groups. Peak velocity, flight height, and flight time were significantly reduced in both groups with HDBR.

CONCLUSION

In this first Canadian HDBR study in older adults, an exercise countermeasure helped maintain aerobic fitness and lean body mass without affecting the reduction of knee extension strength. However, it was ineffective in protecting against orthostatic intolerance. These results support HIIT as a promising approach to preserve astronaut health and functioning during space missions, and to prevent deconditioning as a result of hospitalization in older adults.

Tic-Tac: A Translational Approach in Mechanisms Associated with Irregular Heartbeat and Sinus Rhythm Restoration in Atrial Fibrillation Patients

Atrial fibrillation (AF) is a prevalent cardiac condition predominantly affecting older adults, characterized by irregular heartbeat rhythm. The condition often leads to significant disability and increased mortality rates. Traditionally, two therapeutic strategies have been employed for its treatment: heart rate control and rhythm control. Recent clinical studies have emphasized the critical role of early restoration of sinus rhythm in improving patient outcomes. The persistence of the irregular rhythm allows for the progression and structural remodeling of the atria, eventually leading to irreversible stages, as observed clinically when AF becomes permanent. Cardioversion to sinus rhythm alters this progression pattern through mechanisms that are still being studied. In this review, we provide an in-depth analysis of the pathophysiological mechanisms responsible for maintaining AF and how they are modified during sinus rhythm restoration using existing therapeutic strategies at different stages of clinical investigation. Moreover, we explore potential future therapeutic approaches, including the promising prospect of gene therapy.

Advances in basic and translational research in atrial fibrillation

Atrial fibrillation (AF) is a very common cardiac arrhythmia with an estimated prevalence of 33.5 million patients globally. It is associated with an increased risk of death, stroke and peripheral embolism. Although genetic studies have identified a growing number of genes associated with AF, the definitive impact of these genetic findings is yet to be established. Several mechanisms, including electrical, structural and neural remodelling of atrial tissue, have been proposed to contribute to the development of AF. Despite over a century of exploration, the molecular and cellular mechanisms underlying AF have not been fully established. Current antiarrhythmic drugs are associated with a significant rate of adverse events and management of AF using ablation is not optimal, especially in cases of persistent AF. This review discusses recent advances in our understanding and management of AF, including new concepts of epidemiology, genetics and pathophysiological mechanisms. We review the current status of antiarrhythmic drug therapy for AF, new potential agents, as well as mechanism-based AF ablation. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.

Supraventricular Arrhythmia Following Patent Foramen Ovale Percutaneous Closure

BACKGROUND

Randomized studies have reported low rates of atrial fibrillation (AF) after patent foramen ovale (PFO) closure (<6%) but have relied on patient-reported symptomatic episodes, so the true incidence and timing of AF after PFO closure remain unknown.

OBJECTIVES

The aim of this study was to prospectively determine the incidence, timing, and determinants of supraventricular arrhythmia following PFO closure on the basis of loop recorder monitoring.

METHODS

Cardiac monitoring was proposed to all patients after PFO closure from June 2018 to October 2021 at a single center by means of implantable loop recorder monitoring in patients considered at higher risk for AF (age ≥ 55 years, associated cardiovascular risk factors, prior palpitations, or documented supraventricular ectopic activity) or 4-week external loop recorder monitoring in other patients. The primary endpoint was the incidence of AF, atrial flutter, or supraventricular tachycardia lasting >30 seconds within 28 days of the procedure. Determinants of the primary endpoint were assessed using a stepwise logistic regression model.

RESULTS

A total of 225 patients were included. The primary endpoint occurred in 47 patients (20.9%), including 13 (9.9%) and 24 (28.9%) among patients monitored with external loop recorders and implantable loop recorders, respectively. Overall, the median delay from procedure to arrhythmia was 14.0 days (IQR: 6.5-19.0 days), and one-half of these patients reported symptomatic episodes. Determinants of the primary endpoint were older age (adjusted OR: 1.67 per 10-year increase; 95% CI: 1.18-2.36), device left disc diameter ≥25 mm (adjusted OR: 2.67; 95% CI: 1.19-5.98) and male sex (adjusted OR: 4.78; 95% CI: 1.96-11.66).

CONCLUSIONS

Using loop recorder monitoring for ≥28 days, supraventricular arrhythmia was diagnosed in 1 in 5 patients, with a median delay of 14 days, suggesting that this postprocedural event has so far been underestimated.

Ezh2 Inhibits Replicative Senescence of Atrial Fibroblasts Through Promotion of H3K27me3 in the Promoter Regions of CDKN2a and Timp4 Genes

Background

In most cell types, replicative senescence (RS) is supposed to be a principle causative factor for aging. Atrial fibrosis, pathologically characterized by proliferation of atrial fibroblasts (AFs) and excessive accumulation of extracellular matrix proteins, is the most common substrate of atrial fibrillation (Afib) in the elderly. However, whether AFs’ RS develops in the aged and fibrotic left atrium (LA) and, if yes, what is the key regulator for the pathogenesis of AFs’ RS remain largely unknown.

Methods

We obtained the left atrial tissues from young (6–8 weeks old) and aged (24 months old) C57BL/6 male mice. Screening and validation of differential genes were performed using comparative analysis of RNA-seq results. Replicative senescence was examined in primary AFs after cell passage. Further gain-of-function and loss-of-function experiments were performed to explore the regulation of the AFs’ RS progression.

Results

In the present study, we demonstrated that there was a considerable extent of AFs’ RS in the aged and fibrotic LA. Transcriptome screening showed that Ezh2 (Enhancer of zeste homolog 2) was significantly downregulated in the LA tissue of aged mice. Ezh2 is a histone methyltransferase that catalyzes H3K27me3 and mediates transcriptional silencing. We confirmed that Ezh2 was downregulated in the isolated pure senescent AFs. Knockdown of Ezh2 by siRNA or inhibition of Ezh2ʹs methyltransferase activities by GSK-126 and GSK-343 accelerated RS in the early passage of AFs, while its overexpression deaccelerated RS in the late passage of AFs. Mechanistically, Ezh2 suppressed CDKN2a (p16, p19) and Timp4 gene transcription by forming canonical H3K27me3 modifications in their promoter regions. Furthermore, the functional balance between Timp4 and MMP8 in AFs could be collapsed by changes in Ezh2 expression.

Conclusion

These results thus indicate that Ezh2 is a key regulator of AFs’ RS and this work may provide a basis for future treatments for atrial fibrosis in the elderly.

Association between complete right bundle branch block and atrial fibrillation development

Background

Complete right bundle branch block (CRBBB) is an important predictor of atrial fibrillation (AF) recurrence after pulmonary vein isolation. However, the association between CRBBB and AF development remains unclear.

Methods

We performed a retrospective study of 2639 patients (male, n = 1549; female, n = 1090; mean age, 58 ± 13 years). CRBBB was defined as a late R (R′) wave in lead V₁ or V₂ with a slurred S wave in lead I and/or lead V₆ with a prolonged QRS duration (≥120 ms).

Results

Among the 2639 patients, CRBBB was detected in 40 patients (1.5%), and the prevalence of AF was 7.4% (196/2639). The proportion of patients with AF and CRBBB was higher than the proportion of patients with AF without CRBBB (22.5% vs. 7.2%; p = 0.001). In the forward multivariate logistic analysis, CRBBB (odds ratio [OR], 3.329; 95% confidence interval [CI], 1.350–8.211; p = 0.009), complete left bundle branch block (OR, 2.209; 95% CI, 1.238–3.940; p = 0.007), age (OR, 1.020; 95% CI, 1.005–1.035; p = 0.009), valvular heart disease (OR, 2.332; 95% CI, 1.531–3.552; p < 0.001), left atrial diameter (OR, 1.133; 95% CI, 1.104–1.163; p < 0.001), left ventricular ejection fraction (OR, 1.023; 95% CI, 1.006–1.041; p = 0.007), and class I or III anti‐arrhythmic drug use (OR, 10.534; 95% CI, 7.090–15.651; p < 0.001) were associated with AF.

Conclusion

Complete right bundle branch block was significantly associated with AF development in hospitalized patients with cardiovascular diseases.

The role of cellular senescence in cardiac disease: basic biology and clinical relevance

Cellular senescence, classically defined as stable cell cycle arrest, is implicated in biological processes such as embryogenesis, wound healing and ageing. Senescent cells have a complex senescence-associated secretory phenotype (SASP), involving a range of pro-inflammatory factors with important paracrine and autocrine effects on cell and tissue biology. Clinical evidence and experimental studies link cellular senescence, senescent cell accumulation, and the production and release of SASP components with age-related cardiac pathologies such as heart failure, myocardial ischaemia and infarction, and cancer chemotherapy-related cardiotoxicity. However, the precise role of senescent cells in these conditions is unclear and, in some instances, both detrimental and beneficial effects have been reported. The involvement of cellular senescence in other important entities, such as cardiac arrhythmias and remodelling, is poorly understood. In this Review, we summarize the basic biology of cellular senescence and discuss what is known about the role of cellular senescence and the SASP in heart disease. We then consider the various approaches that are being developed to prevent the accumulation of senescent cells and their consequences. Many of these strategies are applicable in vivo and some are being investigated for non-cardiac indications in clinical trials. We end by considering important knowledge gaps, directions for future research and the potential implications for improving the management of patients with heart disease.

Paroxysmal Atrial Fibrillation in Horses: Pathophysiology, Diagnostics and Clinical Aspects

Atrial fibrillation (AF) is the most common arrhythmia in horses causing poor performance. As in humans, the condition can be intermittent in nature, known as paroxysmal atrial fibrillation (pAF). This review covers the literature relating to pAF in horses and includes references to the human literature to compare pathophysiology, clinical presentation, diagnostic tools and treatment. The arrhythmia is diagnosed by auscultation and electrocardiography (ECG), and clinical signs can vary from sudden loss of racing performance to reduced fitness or no signs at all. If left untreated, pAF may promote electrical, functional and structural remodeling of the myocardium, thus creating a substrate that is able to maintain the arrhythmia, which over time may progress into permanent AF. Long-term ECG monitoring is essential for diagnosing the condition and fully understanding the duration and frequency of pAF episodes. The potential to adapt human cardiac monitoring systems and computational ECG analysis is therefore of interest and may benefit future diagnostic tools in equine medicine.

Strain Echocardiography to Predict Postoperative Atrial Fibrillation

Postoperative atrial fibrillation (POAF) complicates 15% to 40% of cardiovascular surgeries. Its incidence progressively increases with aging, reaching 50% in octogenarians. This arrhythmia is usually transient but it increases the risk of embolic stroke, prolonged hospital stay, and cardiovascular mortality. Though many pathophysiological mechanisms are known, POAF prediction is still a hot topic of discussion. Doppler echocardiogram and, lately, strain echocardiography have shown significant capacity to predict POAF. Alterations in oxidative stress, calcium handling, mitochondrial dysfunction, inflammation, fibrosis, and tissue aging are among the mechanisms that predispose patients to the perfect "atrial storm". Manifestations of these mechanisms have been related to enlarged atria and impaired function, which can be detected prior to surgery. Specific alterations in the atrial reservoir and pump function, as well as atrial dyssynchrony determined by echocardiographic atrial strain, can predict POAF and help to shed light on which patients could benefit from preventive therapy.

Comparison of risk profiles for new-onset atrial fibrillation between patients aged <60 and ≥60 years

BACKGROUND

Atrial fibrillation (AF) has a heterogeneous pathophysiology according to individual patient characteristics. This study aimed to identify the effects of widely known risk factors on AF incidence according to age and to elucidate the clinical implications of these effects.

METHODS AND RESULTS

We analyzed data from 501,668 subjects (≥18years old) without AF and valvular heart disease from the Korean National Health Insurance Service-National Sample Cohort. The total population was divided into two groups according to age, <60years and ≥60years. AF occurred in 0.7% of the overall population (3,416 of 501,668) during the follow-up period (mean 47.6 months). In Cox regression analysis, age, male sex, previous ischemic stroke, heart failure, and hypertension were related to increased risk of new-onset AF in both age groups. Especially in the <60years age group, risk of new-onset AF was increased by relatively modifiable risk factors: obesity (body mass index ≥25kg/m2; hazard ratio[HR] 1.37 [1.22-1.55], p<0.001, interaction p<0.001), and hypertension (HR 1.93[1.69-2.22], p<0.001, interaction p<0.001). Although interactions were not significant, chronic obstructive pulmonary disease (HR 1.41[1.24-1.60], p<0.001) and chronic kidney disease (HR 1.28[1.15-1.41], p<0.001) showed increased trends of the risk of new-onset AF in the ≥60years age group.

CONCLUSION

The risk profile for new-onset AF was somewhat different between the <60years and the ≥60years age groups. Compared to the ≥60years group, relatively modifiable risk factors (such as obesity and hypertension) had a greater impact on AF incidence in the <60years age group. Different management strategies to prevent AF development according to age may be needed.

Updates on epicardial adipose tissue mechanisms on atrial fibrillation

Obesity is a well-known risk factor for atrial fibrillation (AF). Local epi-myocardial or intra-myocardial adiposity caused by aging, obesity, or cardiovascular disease (CVD) is considered to be a better predictor of the risk of AF than general adiposity. Some of the described mechanisms suggest that epicardial adipose tissue (EAT) participates in structural remodeling owing to its endocrine activity or its infiltration between cardiomyocytes. Epicardial fat also wraps up the ganglionated plexi that reach the myocardium. Although the increment of volume/thickness and activity of EAT might modify autonomic activity, autonomic system dysfunction might also change the endocrine activity of epicardial fat in a feedback response. As a result, new preventive therapeutic strategies are focused on reducing adiposity and weight loss before AF ablation or inhibiting autonomic neurotransmitter secretion on fat pads during open-heart surgery to reduce the recurrence or postoperative risk of AF. In this manuscript, we review some of the novel findings regarding the pathophysiology and associated risk factors of AF, with special emphasis on the role of EAT in the electrical, structural, and molecular mechanisms of AF initiation and maintenance. In addition, we have included a brief note provided on epicardial fat preclinical models that could be useful for identifying new therapeutic targets.

Mitochondrial Dysfunction Contributes to Aging-Related Atrial Fibrillation

The incidence of atrial fibrillation (AF) increases with age, and telomere length gradually shortens with age. However, whether telomere length is related to AF is still inconclusive, and the exact mechanism by which aging causes the increased incidence of AF is still unclear. We hypothesize that telomere length is correlated with aging-related AF and that mitochondrial dysfunction plays a role in this. This research recruited 96 elderly male patients with AF who were admitted to the Second Medical Center of Chinese PLA General Hospital from April to October 2018. After matching by age and gender, 96 non-AF elderly male patients who were admitted to the hospital for physical examination during the same period were selected as controls. Anthropometric, clinical, and laboratory analyses were performed on all subjects. The mitochondrial membrane potential (MMP) of peripheral blood leukocytes was detected as the indicator of mitochondrial function. Compared with the control group, the leukocyte telomere length (LTL) was significantly shorter (P < 0.001), and the level of PGC-1α in serum was significantly lower in AF patients. Additionally, in subjects without any other diseases, the AF patients had lower MMP when compared with the control. Multivariate logistic regression confirmed that LTL (OR 0.365; 95% CI 0.235-0.568; P < 0.001) and serum PGC-1α (OR 0.993; 95% CI 0.988-0.997; P = 0.002) were inversely associated with the presence of AF. In addition, ROC analysis indicated the potential diagnostic value of LTL and serum PGC-1α with AUC values of 0.734 and 0.633, respectively. This research concludes that LTL and serum PGC-1α are inversely correlated with the occurrence of aging-related AF and that mitochondrial dysfunction plays a role in this.

Role of Oxidative DNA Damage and Repair in Atrial Fibrillation and Ischemic Heart Disease

Atrial fibrillation (AF) and ischemic heart disease (IHD) represent the two most common clinical cardiac diseases, characterized by angina, arrhythmia, myocardial damage, and cardiac dysfunction, significantly contributing to cardiovascular morbidity and mortality and posing a heavy socio-economic burden on society worldwide. Current treatments of these two diseases are mainly symptomatic and lack efficacy. There is thus an urgent need to develop novel therapies based on the underlying pathophysiological mechanisms. Emerging evidence indicates that oxidative DNA damage might be a major underlying mechanism that promotes a variety of cardiac diseases, including AF and IHD. Antioxidants, nicotinamide adenine dinucleotide (NAD⁺) boosters, and enzymes involved in oxidative DNA repair processes have been shown to attenuate oxidative damage to DNA, making them potential therapeutic targets for AF and IHD. In this review, we first summarize the main molecular mechanisms responsible for oxidative DNA damage and repair both in nuclei and mitochondria, then describe the effects of oxidative DNA damage on the development of AF and IHD, and finally discuss potential targets for oxidative DNA repair-based therapeutic approaches for these two cardiac diseases.

Pathophysiology, Risk Factors, and Management of Atrial Fibrillation in Adult Congenital Heart Disease

A confluence of clinical and epidemiologic factors has provoked a steep increase in the prevalence of atrial fibrillation in adults with congenital heart disease. Atrial fibrillation is the most common presenting arrhythmia. Much remains to be unraveled about the mitigating role congenital heart disease, residual hemodynamic defects, surgical ramifications, and shunts and cyanosis on new-onset and recurrent atrial fibrillation in this population. Catheter ablation is increasingly performed for atrial fibrillation. This synopsis provides an overview of current knowledge on atrial fibrillation in adults with congenital heart disease, addresses clinical management, and discusses knowledge gaps and areas for future research.

Risk Factors for Atrial Fibrillation Progression

Atrial fibrillation is a chronic, progressive condition that presents a major health burden. This review summarizes recent studies assessing atrial fibrillation progression and its associated risk factors, describes the mechanisms underlying atrial fibrillation progression, and discusses the clinical implications of the progressive nature of atrial fibrillation. Progression of atrial fibrillation burden, and clinical progression from paroxysmal to more advanced (persistent/permanent) forms is common, but progression rates are variable. Atrial fibrillation progression parallels progressive atrial remodeling induced by atrial fibrillation risk factors and atrial fibrillation itself, and is associated with worse clinical outcomes.

Cellular and mitochondrial mechanisms of atrial fibrillation

The molecular mechanisms underlying atrial fibrillation (AF), the most common form of arrhythmia, are poorly understood and therefore target-specific treatment options remain an unmet clinical need. Excitation–contraction coupling in cardiac myocytes requires high amounts of adenosine triphosphate (ATP), which is replenished by oxidative phosphorylation in mitochondria. Calcium (Ca²⁺) is a key regulator of mitochondrial function by stimulating the Krebs cycle, which produces nicotinamide adenine dinucleotide for ATP production at the electron transport chain and nicotinamide adenine dinucleotide phosphate for the elimination of reactive oxygen species (ROS). While it is now well established that mitochondrial dysfunction plays an important role in the pathophysiology of heart failure, this has been less investigated in atrial myocytes in AF. Considering the high prevalence of AF, investigating the role of mitochondria in this disease may guide the path towards new therapeutic targets. In this review, we discuss the importance of mitochondrial Ca²⁺ handling in regulating ATP production and mitochondrial ROS emission and how alterations, particularly in these aspects of mitochondrial activity, may play a role in AF. In addition to describing research advances, we highlight areas in which further studies are required to elucidate the role of mitochondria in AF.

Dynamics of Atrial Fibrillation Mechanisms and Comorbidities

Atrial fibrillation (AF) contributes to morbidity and mortality of millions of individuals. Its molecular, cellular, neurohumoral, and hemodynamic pathophysiological mechanisms are complex, and there is increasing awareness that a wide range of comorbidities can contribute to AF-promoting atrial remodeling. Moreover, recent research has highlighted that AF risk is not constant and that the temporal variation in concomitant conditions contributes to the complexity of AF dynamics. In this review, we provide an overview of fundamental AF mechanisms related to established and emerging comorbidities or risk factors and their role in the AF-promoting effects. We focus on the accumulating evidence for the relevance of temporally dynamic changes in these risk factors and the consequence for AF initiation and maintenance. Finally, we highlight the important implications for future research and clinical practice resulting from the dynamic interaction between AF risk factors and mechanisms.

Systemic right ventricle in elderly patients with congenitally corrected transposition of the great arteries: Clinical profile, cardiac biomarkers, and echocardiographic parameters

OBJECTIVE

The number of patients with congenitally corrected transposition of the great arteries (ccTGA) surviving to old age is increasing. This study therefore sought to characterize 'geriatric' systemic right ventricle (sRV) in terms of clinical profile, cardiac biomarkers, and echocardiography-derived function when compared with findings in younger patients.

METHODS

A single-center cross-sectional study of adults with ccTGA was performed. Patients underwent clinical assessment; transthoracic echocardiography; and venous blood sampling including N-terminal pro-B-type natriuretic peptide (NTproBNP), galectin-3, and soluble suppression of tumorgenicity 2 (sST2) measurements. In the echocardiographic study, the sRV function was assessed using fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE), systolic pulsed-wave Doppler velocity (s'), and longitudinal strain (LS).

RESULTS

Ten patients with ccTGA aged 60 years or older and 53 patients younger than 60 years of age were included. There were significantly more individuals with hypertension (40% vs. 5.7%), dyslipidaemia (50% vs. 5.7%), and atrial fibrillation (70% vs. 20.7%) in the older group; similarly, we found higher NTproBNP (2706 pg/mL vs. 784.7 pg/mL; p<0.001), and galectin-3 (10.15 ng/mL vs. 7.24 ng/mL; p=0.007) concentrations in elderly ccTGA individuals, while sST2 content did not vary significantly according to age. Upon echocardiographic assessment, lower sRV FAC (28.6% vs. 36.1%; p=0.028) and LS (-12% vs. -15.5%; p=0.017) values were observed in patients aged 60 years or older. TAPSE and s' did not differ between the age groups.

CONCLUSION

Careful screening for acquired comorbidities, particularly atrial fibrillation, in elderly ccTGA patients is warranted. Examining selected cardiac biomarkers and echocardiography-derived parameters are useful in the assessment of the aging sRV.

Triggered Ca2+ Waves Induce Depolarization of Maximum Diastolic Potential and Action Potential Prolongation in Dog Atrial Myocytes

BACKGROUND

We have identified a novel form of abnormal Ca2+ wave activity in normal and failing dog atrial myocytes which occurs during the action potential (AP) and is absent during diastole. The goal of this study was to determine if triggered Ca2+ waves affect cellular electrophysiological properties.

METHODS

Simultaneous recordings of intracellular Ca2+ and APs allowed measurements of maximum diastolic potential and AP duration during triggered calcium waves (TCWs) in isolated dog atrial myocytes. Computer simulations then explored electrophysiological behavior arising from TCWs at the tissue scale.

RESULTS

At 3.3 to 5 Hz, TCWs occurred during the AP and often outlasted several AP cycles. Maximum diastolic potential was reduced, and AP duration was significantly prolonged during TCWs. All electrophysiological responses to TCWs were abolished by SEA0400 and ORM10103, indicating that Na-Ca exchange current caused depolarization. The time constant of recovery from inactivation of Ca2+ current was 40 to 70 ms in atrial myocytes (depending on holding potential) so this current could be responsible for AP activation during depolarization induced by TCWs. Modeling studies demonstrated that the characteristic properties of TCWs are potentially arrhythmogenic by promoting both conduction block and reentry arising from the depolarization induced by TCWs.

CONCLUSIONS

Triggered Ca2+ waves activate inward NCX and dramatically reduce atrial maximum diastolic potential and prolong AP duration, establishing the substrate for reentry which could contribute to the initiation and maintenance of atrial arrhythmias.

Cardiac tissue remodeling in healthy aging: the road to pathology

This review aims to highlight the normal physiological remodeling that occurs in healthy aging hearts, including changes that occur in contractility, conduction, valve function, large and small coronary vessels, and the extracellular matrix. These "normal" age-related changes serve as the foundation that supports decreased plasticity and limited ability for tissue remodeling during pathophysiological states such as myocardial ischemia and heart failure. This review will identify populations at greater risk for poor tissue remodeling in advanced age along with present and future therapeutic strategies that may ameliorate dysfunctional tissue remodeling in aging hearts.

PREvention of recurrent arrhythmias with Mediterranean diet (PREDIMAR) study in patients with atrial fibrillation: Rationale, design and methods

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia. Catheter ablation aims to restore sinus rhythm. However, relapses occur in up to 30% of patients. A Mediterranean diet (MedDiet) enriched with extra-virgin olive oil (EVOO) substantially reduced the incidence of AF in the PREDIMED trial. The PREDIMAR will test a similar intervention in secondary prevention.

Methods

PREDIMAR is a multicenter, randomized, single-blind trial testing the effect of a MedDiet enriched with EVOO to reduce tachyarrhythmia relapses after AF ablation. The primary outcome is the recurrence of any sustained atrial tachyarrhythmia after ablation (excluding those occurring only during the first 3 months after ablation). The target final sample size is 720 patients (360 per group) recruited from 4 Spanish hospitals. A remote intervention, maintained for 2 years, is delivered to the active intervention group including periodic phone calls by a dietitian and free provision of EVOO. The control group will receive delayed intervention after trial completion. Routine electrocardiogram (ECG) and Holter ECG are performed, and a portable cardiac rhythm monitoring device is provided to be worn by participants during 15 months.

Results

Recruitment started in March 2017. Up to July 2019, 609 patients were randomized (average inclusion rate: 5.3 patients/wk). Retention rates after 18 months are >94%.

Conclusions

If our hypothesis is confirmed, the utility of the MedDiet enriched with EVOO in slowing the progression of AF will be proven, preventing recurrences and potentially reducing complications.

Longitudinal study of electrical, functional and structural remodelling in an equine model of atrial fibrillation

Background

Large animal models are important in atrial fibrillation (AF) research, as they can be used to study the pathophysiology of AF and new therapeutic approaches. Unlike other animal models, horses spontaneously develop AF and could therefore serve as a bona fide model in AF research. We therefore aimed to study the electrical, functional and structural remodelling caused by chronic AF in a horse model.

Method

Nine female horses were included in the study, with six horses tachypaced into self-sustained AF and three that served as a time-matched sham-operated control group. Acceleration in atrial fibrillatory rate (AFR), changes in electrocardiographic and echocardiographic variables and response to medical treatment (flecainide 2 mg/kg) were recorded over a period of 2 months. At the end of the study, changes in ion channel expression and fibrosis were measured and compared between the two groups.

Results

AFR increased from 299 ± 33 fibrillations per minute (fpm) to 376 ± 12 fpm (p < 0.05) and atrial function (active left atrial fractional area change) decreased significantly during the study (p < 0.05). No changes were observed in heart rate or ventricular function. The AF group had more atrial fibrosis compared to the control group (p < 0.05). No differences in ion channel expression were observed.

Conclusion

Horses with induced AF show signs of atrial remodelling that are similar to humans and other animal models.

Mechanisms of Arrhythmia and Sudden Cardiac Death in Patients With HIV Infection

Long-term survival of HIV-infected patients has significantly improved with the use of antiretroviral therapy (ART). As a consequence, cardiovascular diseases are now emerging as an important clinical problem in this population. Sudden cardiac death is the third leading cause of mortality in HIV patients. Twenty percent of patients with HIV who died of sudden cardiac death had previous cardiac arrhythmias including ventricular tachycardia, atrial fibrillation, and other unspecified rhythm disorders. This review presents a summary of HIV-related arrhythmias, associated risk factors specific to the HIV population, and underlying mechanisms. Compared with the general population, patients with HIV have several cardiac conditions and electrophysiological abnormalities. As a result, they have an increased risk of developing severe arrhythmias, that can lead to sudden cardiac death. Possible explanations may be related to non-ART polypharmacy, electrolyte imbalances, and use of substances observed in HIV-infected patients; many of these conditions are associated with alterations in cardiac electrical activity, increasing the risk of arrhythmia and sudden cardiac death. However, clinical and experimental evidence has also revealed that cardiac arrhythmias occur in HIV-infected patients, even in the absence of drugs. This indicates that HIV itself can change the electrophysiological properties of the heart profoundly and cause cardiac arrhythmias and related sudden cardiac death. The current knowledge of the underlying mechanisms, as well as the emerging role of inflammation in these arrhythmias, are discussed here.