Controversies in atrial fibrillation

A possible path to persistent re-entry waves at the outlet of the left pulmonary vein

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia, often evolving from paroxysmal episodes to persistent stages over an extended timeframe. While various factors contribute to this progression, the precise biophysical mechanisms driving it remain unclear. Here we explore how rapid firing of cardiomyocytes at the outlet of the pulmonary vein of the left atria can create a substrate for a persistent re-entry wave. This is grounded in a recently formulated mathematical model of the regulation of calcium ion channel density by intracellular calcium concentration. According to the model, the number of calcium channels is controlled by the intracellular calcium concentration. In particular, if the concentration increases above a certain target level, the calcium current is weakened to restore the target level of calcium. During rapid pacing, the intracellular calcium concentration of the cardiomyocytes increases leading to a substantial reduction of the calcium current across the membrane of the myocytes, which again reduces the action potential duration. In a spatially resolved cell-based model of the outlet of the pulmonary vein of the left atria, we show that the reduced action potential duration can lead to re-entry. Initiated by rapid pacing, often stemming from paroxysmal AF episodes lasting several days, the reduction in calcium current is a critical factor. Our findings illustrate how such episodes can foster a conducive environment for persistent AF through electrical remodeling, characterized by diminished calcium currents. This underscores the importance of promptly addressing early AF episodes to prevent their progression to chronic stages.

Naringin activates semaphorin 3A to ameliorate TGF-β-induced endothelial-to-mesenchymal transition related to atrial fibrillation

The loss of semaphorin 3A (Sema3A), which is related to endothelial-to-mesenchymal transition (EndMT) in atrial fibrosis, is implicated in the pathogenesis of atrial fibrillation (AF). To explore the mechanisms by which EndMT affects atrial fibrosis and assess the potential of a Sema3A activator (naringin) to prevent atrial fibrosis by targeting transforming growth factor-beta (TGF-β)-induced EndMT, we used human atria, isolated human atrial endocardial endothelial cells (AEECs), and used transgenic mice expressing TGF-β specifically in cardiac tissues (TGF-β transgenic mice). We evaluated an EndMT marker (Twist), a proliferation marker (proliferating cell nuclear antigen; PCNA), and an endothelial cell (EC) marker (CD31) through triple immunohistochemistry and confirmed that both EndMT and EC proliferation contribute to atrial endocardial fibrosis during AF in TGF-β transgenic mice and AF patient tissue sections. Additionally, we investigated the impact of naringin on EndMT and EC proliferation in AEECs and atrial fibroblasts. Naringin exhibited an antiproliferative effect, to which AEECs were more responsive. Subsequently, we downregulated Sema3A in AEECs using small interfering RNA to clarify a correlation between the reduction in Sema3A and the elevation of EndMT markers. Naringin treatment induced the expression of Sema3A and a concurrent decrease in EndMT markers. Furthermore, naringin administration ameliorated AF and endocardial fibrosis in TGF-β transgenic mice by stimulating Sema3A expression, inhibiting EndMT markers, reducing atrial fibrosis, and lowering AF vulnerability. This suggests therapeutic potential for naringin in AF treatment.

Sacubitril/valsartan attenuates atrial conduction disturbance and electrophysiological heterogeneity with ameliorating fibrosis in mice

Background

Sacubitril/valsartan (SacVal) has been shown to improve the prognosis of heart failure; however, whether SacVal reduces the occurrence of atrial fibrillation (AF) in heart failure has not yet been elucidated. In this study, we aimed to determine whether SacVal is effective in reducing the occurrence of AF in heart failure and identify the underlying mechanism of its electrophysiological effect in mice.

Methods

Adult male mice underwent transverse aortic constriction, followed by SacVal, valsartan, or vehicle treatment for two weeks. Electrophysiological study (EPS) and optical mapping were performed to assess the susceptibility to AF and the atrial conduction properties, and fibrosis was investigated using heart tissue and isolated cardiac fibroblasts (CFs).

Results

EPS analysis revealed that AF was significantly less inducible in SacVal-treated mice than in vehicle-treated mice. Optical mapping of the atrium showed that SacVal-treated and valsartan-treated mice restored the prolonged action potential duration (APD); however, only SacVal-treated mice showed the restoration of decreased conduction velocity (CV) compared to vehicle-treated mice. In addition, the electrophysiological distribution analysis demonstrated that heterogeneous electrophysiological properties were rate-dependent and increased heterogeneity was closely related to the susceptibility to AF. SacVal attenuated the increased heterogeneity of CV at short pacing cycle length in atria, whereas Val could not. Histological and molecular evaluation showed that SacVal exerted the anti-fibrotic effect on the atria. An in vitro study of CFs treated with natriuretic peptides and LBQ657, the metabolite and active form of sacubitril, revealed that C-type natriuretic peptide (CNP) combined with LBQ657 had an additional anti-fibrotic effect on CFs.

Conclusions

Our results demonstrated that SacVal can improve the conduction disturbance and heterogeneity through the attenuation of fibrosis in murine atria and reduce the susceptibility of AF in heart failure with pressure overload, which might be attributed to the enhanced function of CNP.

The role of lactate in cardiovascular diseases

Cardiovascular diseases pose a major threat worldwide. Common cardiovascular diseases include acute myocardial infarction (AMI), heart failure, atrial fibrillation (AF) and atherosclerosis. Glycolysis process often has changed during these cardiovascular diseases. Lactate, the end-product of glycolysis, has been overlooked in the past but has gradually been identified to play major biological functions in recent years. Similarly, the role of lactate in cardiovascular disease is gradually being recognized. Targeting lactate production, regulating lactate transport, and modulating circulating lactate levels may serve as potential strategies for the treatment of cardiovascular diseases in the future. The purpose of this review is to integrate relevant clinical and basic research on the role of lactate in the pathophysiological process of cardiovascular disease in recent years to clarify the important role of lactate in cardiovascular disease and to guide further studies exploring the role of lactate in cardiovascular and other diseases. Video Abstract.

Mechanism of myocardial fibrosis regulation by IGF-1R in atrial fibrillation through the PI3K/Akt/FoxO3a pathway

Atrial structural remodeling takes on a critical significance to the occurrence and maintenance of atrial fibrillation (AF). As revealed by recent data, insulin-like growth factor-1 receptor (IGF-1R) plays a certain role in tissue fibrosis. In this study, the mechanism of IGF-1R in atrial structural remodeling was examined based on in vivo and in vitro experiments. First, cluster analysis of AF hub genes was conducted, and then the molecular mechanism was proposed by which IGF-1R regulates myocardial fibrosis via the PI3K/Akt/FoxO3a pathway. Subsequently, the mentioned mechanism was verified in human cardiac fibroblasts (HCFs) and rats transduced with IGF-1 overexpression type 9 adeno-associated viruses. The results indicated that IGF-1R activation up-regulated collagen Ⅰ protein expression and Akt phosphorylation in HCFs and rat atrium. The administration of LY294002 reversed the above phenomenon, improved the shortening of atrial effective refractory period, and reduced the increased incidence of AF and atrial fibrosis in rats. The transfection of FoxO3a siRNA reduced the anti-fibrotic effect of LY294002 in HCFs. The above data revealed that activation of IGF-1R takes on a vital significance to atrial structural remodeling by facilitating myocardial fibrosis and expediting the occurrence and maintenance of AF through the regulation of the PI3K/Akt/FoxO3a signaling pathway.

Atrial late potentials are associated with atrial fibrillation recurrence after catheter ablation

Background

Previous studies have identified noninvasive methods for predicting atrial fibrillation (AF) recurrence after catheter ablation (CA). We assessed the association between AF recurrence and atrial late potentials (ALPs), which were measured using P‐wave signal‐averaged electrocardiography (P‐SAECG).

Methods

Consecutive patients with paroxysmal AF who underwent their first CA at our institution between August 2015 and August 2019 were enrolled. P‐SAECG was performed before CA. Two ALP parameters were evaluated: the root‐mean‐square voltage during the terminal 20 ms (RMS₂₀) and the P‐wave duration (PWD). Positive ALPs were defined as an RMS₂₀ <2.2 μV and/or a PWD >115 ms. Patients were allocated to either the recurrence or nonrecurrence group based on the presence of AF recurrence at the 1‐year follow‐up post‐CA.

Results

Of the 190 patients (age: 65 ± 11 years, 37% women) enrolled in this study, 21 (11%) had AF recurrence. The positive ALP rate was significantly higher in the recurrence group than in the nonrecurrence group (86% vs. 64%, p = .04), despite the absence of differences in other baseline characteristics between the two groups. In the multivariate analysis, positive ALP was an independent predictor of AF recurrence (odds ratio: 3.83, 95% confidence interval: 1.05–14.1, p = .04).

Conclusions

Positive ALP on pre‐CA P‐SAECG is associated with AF recurrence after CA.

Leukocyte Telomere Length Predicts Progression From Paroxysmal to Persistent Atrial Fibrillation in the Long Term After Catheter Ablation

Background

Aging is significantly associated with the incidence and progression of atrial fibrillation (AF) incidence. This study aimed to evaluate the potential predictive value of leukocyte telomere length (LTL) for progression from paroxysmal AF (PAF) to persistent AF (PsAF) after catheter ablation.

Methods and Results

A total of 269 patients with AF (154 patients with PAF and 115 patients with PsAF, respectively) were prospectively enrolled, and all patients with PAF at baseline were regularly followed up to determine whether and when they should progress to PsAF after catheter ablation therapy. Baseline relative LTL was measured by quantitative real-time PCR (rt-PCT). There was a significant negative association between LTL and age (r = −0.23, p < 0.001). Patients with PsAF had significantly shorter LTL than those with PAF. After a mean follow-up of 854.9 ± 18.7 d, progression events occurred in 35 out of the 154 patients with PAF. Those progressed patients with PAF were older (70.9 ± 8.0 vs. 62.3 ± 10.3, p < 0.001) and had shorter LTL (1.2 ± 0.3 vs. 1.5 ± 0.3, p < 0.001) than those who did not. The receiver operating characteristic (ROC) curve analysis showed a significant value of LTL in distinguishing patients with PAF from patients with PsAF, with an area under the ROC curve (AUC) of 0.63 (95% CI 0.56–0.70, p < 0.001), and the optimal cut-off value of LTL was 1.175, with a sensitivity and specificity of 56.03 and 82.04%, respectively. All patients with PAF were divided into two subgroups according to the optimal cut-off point of LTL calculated by the ROC curve analysis: high LTL group (≥1.175) and low LTL group (<1.175). Kaplan-Meier curve analysis showed that PAF patients with shorter LTL had a significantly higher rate of progression after catheter ablation (40.5% vs. 18.8%, log-rank test p < 0.001). Multivariate Cox proportional-hazards model indicated that LTL [hazard ratio (HR): 2.71, 95% CI 1.36–5.42, p = 0.005] was an independent predictor for progression from PAF to PsAF after catheter ablation therapy, but HATCH score was not (HR: 1.02, 95% CI: 0.68–1.52, p = 0.923).

Conclusion

Leukocyte telomere length was significantly associated with AF types. LTL was independently associated with progression from PAF to PsAF after catheter ablation therapy.

Chinese Clinical Trial Registry, Registration Number: ChiCTR1900021341.

Curcumin, novel application in reversing myocardial fibrosis in the treatment for atrial fibrillation from the perspective of transcriptomics in rat model

In order to explore the possible mechanism of curcumin in the treatment of AF, we focused on the myocardial fibrosis in the pathogenesis of atrial fibrillation to explore whether curcumin could play a role in the treatment of AF by reducing myocardial fibrosis.Rats were given daily gavage of saline (control and AF groups) or curcumin (4 mL/kg, concentration: 50 mg/mL, curcumin groups) during days 4-28. The rat model of AF was induced by Ach - CaCl₂, and evaluate the therapeutic effect of curcumin on the duration of AF rhythm, the degree of myocardial fibrosis and the secretion of inflammatory factors in serum. RNA-seq to explore the possible mechanism of curcumin alleviating myocardial fibrosis of AF. curcumin significantly inhibits the duration of AF and reduces the degree of left atrial fibrosis. ELISA results showed curcumin could significantly reduce the secretion of IL-17A, IL-1β, IL -6 and TGF-β1. Bioinformatics analyses revealed that the IL-17 signaling pathway are involved in the therapeutic mechanism of curcumin. Furthermore, The genes encoding Col1a1, Fasn, Pck1, Bmp10, IL33 and Figf were pivotal and possible key genes for the therapeutic mechanisms of curcumin.Curcumin can reduce the degree of left atrial fibrosis of AF and the secretion of inflammatory factors. The therapeutic effect of curcumin on AF was attributed to its effect on the IL-17 signaling pathway. Besides, COL1A1, FASN, PCK1, BMP10, IL33 and FIGF were the pivotal genes associated with mechanisms of action of curcumin on AF.

Recent-onset atrial fibrillation: a study exploring the elements of Virchow's triad after cardioversion

Purpose

Atrial fibrillation (AF) imposes an inherent risk for stroke and silent cerebral emboli, partly related to left atrial (LA) remodeling and activation of inflammatory and coagulation systems. The aim was to explore the effects of cardioversion (CV) and short-lasting AF on left atrial hemodynamics, inflammatory, coagulative and cardiac biomarkers, and the association between LA functional recovery and the presence of a prior history of AF.

Methods

Patients referred for CV within 48 h after AF onset were prospectively included. Echocardiography and blood sampling were performed immediately prior, 1–3 h after, and at 7–10 days after CV. The presence of chronic white matter hyperintensities (WMH) on magnetic resonance imaging was related to biomarker levels.

Results

Forty-three patients (84% males), aged 55±9.6 years, with median CHA₂DS₂-VASc score 1 (IQR 0–1) were included. The LA emptying fraction (LAEF), LA peak longitudinal strain during reservoir, conduit, and contractile phases improved significantly after CV. Only LAEF normalized within 10 days. Interleukin-6, high-sensitivity cardiac-troponin-T (hs-cTNT), N-terminal-pro-brain-natriuretic peptide, prothrombin-fragment 1+2 (PTf1+2), and fibrinogen decreased significantly after CV. There was a trend towards higher C-reactive protein, hs-cTNT, and PTf1+2 levels in patients with WMH (n=21) compared to those without (n=22). At 7–10 days, the LAEF was significantly lower in patients with a prior history of AF versus those without.

Conclusion

Although LA stunning resolved within 10 days, LAEF remained significantly lower in patients with a prior history of AF versus those without. Inflammatory and coagulative biomarkers were higher before CV, but subsided after 7–10 days, which altogether might suggest an enhanced thrombogenicity, even in these low-risk patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10840-021-01078-9.

Atrial slow conduction develops and dynamically expands during premature stimulation in an animal model of persistent atrial fibrillation

Slow conduction areas and conduction block in the atria are considered pro-arrhythmic conditions. Studies examining the size and distribution of slow conduction regions in the context of persistent atrial fibrillation (AF) may help to develop improved therapeutic strategies for patients with AF. In this work, we studied the differences of size and number in slow conduction areas between control and persistent AF goats and the influence of propagation direction on the development of these pathological conduction areas. Epicardial atrial electrical activations from the left atrial roof were optically mapped with physiological pacing cycle lengths and for the shortest captured cycle lengths. The recordings were converted to local activation times and conduction velocity measures. Regions with slow conduction velocity (less than [Formula: see text]) were identified. The size of the connected regions and the number of non-connected regions were counted for propagation from different orthogonal directions. We found that regions of slow conduction significantly increases in our 15 persistent AF goat recordings in response to premature stimulation (24.4±4.3% increase to 36.6±4.4%, p < 0.001). This increase is driven by an increase of size from (3.70±0.89[mm2] to 6.36±0.91[mm2], p = 0.014) for already existing regions and not by generation of new slow conduction regions (11.6±1.8 vs. 13±1.9, p = 0.242). In 12 control goat recordings, no increase from baseline pacing to premature pacing was found. Similarly, size of the slow conduction areas and the count did not change significantly in control animals.

New Strategies for the Treatment of Atrial Fibrillation

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in the clinical practice. It significantly contributes to the morbidity and mortality of the elderly population. Over the past 25-30 years intense effort in basic research has advanced the understanding of the relationship between the pathophysiology of AF and atrial remodelling. Nowadays it is clear that the various forms of atrial remodelling (electrical, contractile and structural) play crucial role in initiating and maintaining the persistent and permanent types of AF. Unlike in ventricular fibrillation, in AF rapid ectopic firing originating from pulmonary veins and re-entry mechanism may induce and maintain (due to atrial remodelling) this complex cardiac arrhythmia. The present review presents and discusses in detail the latest knowledge on the role of remodelling in AF. Special attention is paid to novel concepts and pharmacological targets presumably relevant to the drug treatment of atrial fibrillation.

8-hydroxypinoresinol-4-O-β-D-glucoside from Valeriana officinalis L. Is a Novel Kv1.5 Channel Blocker

ETHNOPHARMACOLOGY RELEVANCE

In folkloric medicine of many cultures, one of the medical uses of Valeriana officinalis Linn is to treat heart-related disease. Recently, it was shown that the ethanol extracts from V. officinalis could effectively prevent auricular fibrillation, and 8-hydroxypinoresinol-4-O-β-D-glucoside (HPG) from the extracts is one of the two active compounds showing antiarrhythmia activities.

AIM OF THE STUDY

The human Kv1.5 channel (hKv1.5) has potential antiarrhythmia activities, and this study arms at investigating the current blocking effects of HPG on hKv1.5 channel.

MATERIAL AND METHODS

HPG was obtained from V. officinalis extracts, and hKv1.5 channels were expressed in HEK 293 cells. HPG was perfused while recording the current through hKv1.5 channels. Patch-clamp recording techniques were used to study the effects of HPG at various concentrations (10 μM, 30 μM, and 50 μM) on hKv1.5 channels.

RESULTS

The present study demonstrated that HPG inhibited hKv1.5 channel current in a concentration-dependent manner; the higher the concentration, the greater is the inhibition at each depolarization potential. During washout, the channels did not full recover indicating that the un-coupling between HPG and hKv1.5 channels is a slow process.

CONCLUSION

HPG may be an effective and safe active ingredient for AF having translational potential.

A Single-Center Prospective Study of 116 Women with Osteoporosis Treated with Zoledronic Acid Monitored by Electrocardiography for the Development of Cardiac Arrhythmia During the Acute Phase in China

Background

Concerns have been raised among clinicians and patients about the cardiovascular risks of bisphosphonates used in the treatment of osteoporosis. The goal of this study was to investigate the acute effect of zoledronic acid (ZA) infusion on arrhythmia development using an electrocardiograph (ECG).

Material/Methods

This prospective study was a self-controlled case series study that recruited 116 female patients with osteoporosis. The patients underwent standard 12-lead electrocardiography before and 1 day after zoledronic acid intravenous infusion to evaluate cardiac adverse effects and the change in ECG parameters after the infusion. Heart rhythm, atrial and ventricular premature contractions, atrial fibrillation, P wave, and QTc parameters were measured using an ECG. A blood biochemical examination was performed for all patients before the ZA infusion. Body temperature was measured twice per day.

Results

Before ZA administration, ECG findings were normal in 47 patients and abnormal in 69 patients. After ZA administration, ECG findings were normal in 35 patients and abnormal in 81 patients. New onsets of premature atrial contractions and atrial fibrillation were observed in 1 patient each, and new onsets of premature ventricular contractions were observed in 2 patients. The heart rate was obviously higher, and the QT interval was obviously shorter after ZA administration, compared with before administration. No significant differences in P wave and QTc parameters were found between the 2 ECG measurements.

Conclusions

During the acute phase, 116 women with osteoporosis who were treated with zoledronic acid infusion did not develop significantly abnormal ECG changes.

Current Drug Treatment Strategies for Atrial Fibrillation and TASK-1 Inhibition as an Emerging Novel Therapy Option

Atrial fibrillation (AF) is the most common sustained arrhythmia with a prevalence of up to 4% and an upwards trend due to demographic changes. It is associated with an increase in mortality and stroke incidences. While stroke risk can be significantly reduced through anticoagulant therapy, adequate treatment of other AF related symptoms remains an unmet medical need in many cases. Two main treatment strategies are available: rate control that modulates ventricular heart rate and prevents tachymyopathy as well as rhythm control that aims to restore and sustain sinus rhythm. Rate control can be achieved through drugs or ablation of the atrioventricular node, rendering the patient pacemaker-dependent. For rhythm control electrical cardioversion and pharmacological cardioversion can be used. While electrical cardioversion requires fasting and sedation of the patient, antiarrhythmic drugs have other limitations. Most antiarrhythmic drugs carry a risk for pro-arrhythmic effects and are contraindicated in patients with structural heart diseases. Furthermore, catheter ablation of pulmonary veins can be performed with its risk of intraprocedural complications and varying success. In recent years TASK-1 has been introduced as a new target for AF therapy. Upregulation of TASK-1 in AF patients contributes to prolongation of the action potential duration. In a porcine model of AF, TASK-1 inhibition by gene therapy or pharmacological compounds induced cardioversion to sinus rhythm. The DOxapram Conversion TO Sinus rhythm (DOCTOS)-Trial will reveal whether doxapram, a potent TASK-1 inhibitor, can be used for acute cardioversion of persistent and paroxysmal AF in patients, potentially leading to a new treatment option for AF.

Atrial fibrillation and cardiac fibrosis: A review on the potential of extracellular matrix proteins as biomarkers

The involvement of fibrosis as an underlying pathology in heart diseases is becoming increasingly clear. In recent years, fibrosis has been granted a causative role in heart diseases and is now emerging as a major contributor to Atrial Fibrillation (AF) pathogenesis. AF is the most common arrhythmia encountered in the clinic, but the substrate for AF is still being debated. Consensus in the field is a combination of cardiac tissue remodeling, inflammation and genetic predisposition. The extracellular matrix (ECM) is subject of growing investigation, since measuring circulatory biomarkers of ECM formation and degradation provides both diagnostic and prognostic information. However, fibrosis is not just fibrosis. Each specific collagen biomarker holds information on regulatory mechanisms, as well as information about which section of the ECM is being remodeled, providing a detailed description of cardiac tissue homeostasis. This review entails an overview of the implication of fibrosis in AF, the different collagens and their significance, and the potential of using biomarkers of ECM remodeling as tools for understanding AF pathogenesis and identifying patients at risk for further disease progression.

Potassium infusion increases the likelihood of conversion of recent-onset atrial fibrillation-A single-blinded, randomized clinical trial

BACKGROUND

The optimal antiarrhythmic management of recent-onset atrial fibrillation (ROAF) or atrial flutter is controversial and there is a considerable variability in clinical treatment strategies. It is not known if potassium infusion has the potential to convert ROAF or atrial flutter to sinus rhythm (SR). Therefore, we aimed to investigate if patients with ROAF or atrial flutter and plasma-potassium levels ≤4.0 mmol/L have increased probability to convert to SR if the plasma-potassium level is increased towards the upper reference range (4.1-5.0 mmol/L).

METHODS

In a placebo-controlled, single-blinded trial, patients with ROAF or atrial flutter and plasma-potassium ≤4.0 mmol/L presenting between April 2013 and November 2017 were randomized to receive potassium chloride (KCl) infusion (n = 60) or placebo (n = 53). Patients in the KCl group received infusions at one of three different rates: 9.4 mmol/h (n = 11), 12 mmol/h (n = 19), or 15 mmol/h (n = 30).

RESULTS

There was no statistical difference in the number of conversions to SR between the KCl group and placebo [logrank test, P = .29; hazard ratio (HR) 1.20 (CI 0.72-1.98)]. However, KCl-infused patients who achieved an above-median hourly increase in plasma-potassium (>0.047 mmol/h) exhibited a significantly higher conversion rate compared with placebo [logrank P = .002; HR 2.40 (CI 1.36-4.21)] and KCl patients with below-median change in plasma-potassium [logrank P < .001; HR 4.41 (CI 2.07-9.40)]. Due to pain at the infusion site, the infusion was prematurely terminated in 10 patients (17%).

CONCLUSIONS

Although increasing plasma-potassium levels did not significantly augment conversion of ROAF or atrial flutter to SR in patients with potassium levels in the lower-normal range, our results indicate that this treatment may be effective when a rapid increase in potassium concentration is tolerated and achieved.

An automated hybrid bioelectronic system for autogenous restoration of sinus rhythm in atrial fibrillation

Because of suboptimal therapeutic strategies, restoration of sinus rhythm in symptomatic atrial fibrillation (AF) often requires in-hospital delivery of high-voltage shocks, thereby precluding ambulatory AF termination. Continuous, rapid restoration of sinus rhythm is desired given the recurring and progressive nature of AF. Here, we present an automated hybrid bioelectronic system for shock-free termination of AF that enables the heart to act as an electric current generator for autogenous restoration of sinus rhythm. We show that local, right atrial delivery of adenoassociated virus vectors encoding a light-gated depolarizing ion channel results in efficient and spatially confined transgene expression. Activation of an implanted intrathoracic light-emitting diode device allows for termination of AF by illuminating part of the atria. Combining this newly obtained antiarrhythmic effector function of the heart with the arrhythmia detector function of a machine-based cardiac rhythm monitor in the closed chest of adult rats allowed automated and rapid arrhythmia detection and termination in a safe, effective, repetitive, yet shock-free manner. These findings hold translational potential for the development of shock-free antiarrhythmic device therapy for ambulatory treatment of AF.

Preliminary Observations on the Antihypertension Action of Dabigatran Etexilate in Patients With Nonvalvular Atrial Fibrillation: A Prospective Multicenter Single-Arm Interventional Study

Background

In Japan, the number of patients with atrial fibrillation continues to grow with the aging of the population. Prevention of cardiogenic cerebral embolism is extremely important in patients with atrial fibrillation. While warfarin has long played a major role for this purpose, a new oral anticoagulant, dabigatran etexilate (dabigatran), has demonstrated superior efficacy and safety in recent years. We conducted a multicenter prospective interventional study to examine whether dabigatran could demonstrate superiority over warfarin in practical clinical situation.

Methods

Among outpatients attending Fukuoka University Chikushi Hospital or clinics registered with the Chikushi Cardiovascular Disease Clinical Research Network (Chikushi-JRN), 143 patients with nonvalvular atrial fibrillation (NVAF) were enrolled in this study and followed up for 12 months after initiation of dabigatran therapy. The primary endpoint was occurrence of cerebral embolism or systemic embolism, while secondary endpoints were: 1) Bleeding events; 2) Changes in the activated partial thromboplastin time (aPTT); 3) Adverse events; and 4) Changes in blood pressure and pulse rate.

Results

During the follow-up period, none of the patients developed cerebral or systemic embolism (the primary endpoint). In addition, there were no bleeding events or other adverse events (the secondary endpoints). aPTT remained stable throughout the 12-month observation period. A significant decrease in systolic blood pressure was observed at 1 month after initiation of dabigatran therapy, and blood pressure was reduced up to 12 months. Blood pressure showed a significant decrease in patients with paroxysmal atrial fibrillation, but not in patients with chronic atrial fibrillation.

Conclusions

Dabigatran showed a stable anticoagulant effect, and its safety was confirmed. Dabigatran also reduced blood pressure, which may help to explain why it causes fewer major bleeding events than warfarin.

Protocol for a systematic review and network meta-analysis of the management of new onset atrial fibrillation in critically unwell adult patients

BACKGROUND

New onset atrial fibrillation is the most commonly encountered arrhythmia in critically unwell patients with a reported incidence of 4% to 29%. The occurrence of new onset atrial fibrillation may precipitate acute heart failure and lead to thromboembolic complications as well as being associated with increased in-hospital and in intensive care unit (ICU) mortality. Despite being common, much of our current knowledge regarding the treatment of new onset atrial fibrillation comes from patients with chronic atrial fibrillation or post cardiac surgery. It is unclear if management strategies in these patient cohorts can be applied to new onset atrial fibrillation in the general ICU. This protocol for a systematic review and network meta-analysis aims to address this uncertainty and define what is the most effective management strategy for the treatment of new onset atrial fibrillation (NOAF) in acutely unwell adult patients.

METHODS

In this systematic review and network meta-analysis, we plan to search electronic databases (Cochrane Central Register of Controlled Trials [CENTRAL], MEDLINE, EMBASE, Science Citation Index Expanded on Web of Science and relevant trial registries) for relevant randomised and non-randomised trials. Citations will be reviewed by title, abstract and full text by two independent reviewers and disagreement resolved by discussion and a third independent reviewer, if necessary. The Cochrane Risk of Bias tool will be used to assess risk of bias in randomised trials and the Risk of Bias in Nonrandomised Studies of Interventions (ROBINS-I) tool will be used for non-randomised studies. Statistical analysis will be carried out using R package meta and netmeta. We will first conduct a pairwise meta-analysis. If conditions for indirect comparison are satisfied and suitable data are available, we will conduct network meta-analysis using frequentist methodology. Treatments will be ranked according to efficacy with associated P-scores. We will assess the quality of the evidence in the pairwise using GRADE methodology and network meta-analysis comparisons in the CINeMA module in R package meta.

DISCUSSION

Our review will be the first to assess direct and indirect evidence to assess the efficacy and rank the treatments available for new onset atrial fibrillation in critically unwell patients. Our review findings will be applicable to the care of people in a range of acute settings including, ICU, the emergency department and acute medical units.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registry number: CRD42019121739.

Comparative transcriptome analysis to elucidate the therapeutic mechanism of colchicine against atrial fibrillation

In recent years, colchicine has been used to reduce the risk of cardiovascular events; in particular, it has been effectively used for the treatment of atrial fibrillation (AF). We first discovered that colchicine can treat AF in a rat model and that it can reverse the effects of atrial fibrosis. To illustrate the potential therapeutic mechanism of colchicine against AF, we performed comparative transcriptome analyses; our aim was to elucidate the therapeutic effects of colchicine so as to improve treatment and prognoses of AF. Genomics and bioinformatics analyses revealed that the IL-17 signaling pathway, and renin secretion pathway are involved in the mechanism of action of colchicine. Furthermore, there was a significant correlation between overlapping genes in the two groups of differentially expressed genes. The genes encoding Akap4, Pcdha9, Gp2, Cd177, Krt15, Aqp3, Chia, and Bpifb1 were pivotal and possible action sites for the therapeutic mechanisms of colchicine. We conclude that AF involves a multifactorial pathological process. The mechanisms underlying the action of colchicine in the treatment of AF warrant further studies.

Serum relaxin level predicts recurrence of atrial fibrillation after radiofrequency catheter ablation

Relaxin, an emerging biomarker in heart failure, is involved in fibrosis and inflammation. The value of relaxin in predicting recurrence of atrial fibrillation (AF) after radiofrequency catheter ablation (RFCA) is unknown and the subject of this study. We prospectively enrolled 248 consecutive patients with AF (paroxysmal in 127 and persistent in 121) who underwent RFCA at our center after measurement of circulating levels of relaxin by ELISA. Kaplan-Meier analysis with log-rank test and multivariate analysis were used to assess the association between pre-RFCA relaxin levels and post-RFCA AF recurrence at 18 months follow-up. At mean 16.3 ± 3.8 months post-RFCA, 195 (78.6%) patients maintained sinus rhythm, and their pre-RFCA relaxin level was lower than that in patients with AF recurrence (P < 0.001). From lowest to highest pre-RFCA relaxin level tertiles (T1; 82.10-< 234.36; T2; 234.36-< 342.26; and T3; 342.26-740.63 ng/L), AF recurrence rate increased significantly (8.5%, 20.5% and 34.9%, respectively; Kaplan-Meier analysis with log-rank test, χ² = 18.44, P < 0.001). Using a cutoff of 285.4 ng/L, pre-RFCA relaxin level predicted AF recurrence during follow-up with sensitivity of 77.4% and specificity of 55.9% (area under the receiver operating characteristic curve = 0.71). On multivariate Cox proportional hazard model, relaxin level by tertile (T2, hazard ratio 2.678; 95% confidence interval 1.110-6.460; P = 0.028, and T3, hazard ratio 4.745; 95% confidence interval 2.075-10.854; P < 0.001, respectively compared with the T1) was the independent factor predicting recurrence. Elevated pre-RFCA relaxin level is associated with post-RFCA AF recurrence. A simple measurement of relaxin level therefore might help identify patients at high risk of AF recurrence after RFCA.Clinical Trial Registration chictr.org.cn identifier: ChiCTR-OOC-15006130.

Atrioventricular block can be used as a risk predictor of clinical atrial fibrillation

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia, with its incidence making up nearly one‐third of all hospital admissions. Atrioventricular block (AVB) is a conduction abnormality along the atrioventricular node or the His‐Purkinje system. The relationship between atrioventricular conduction block and AF is controversial.

Hypothesis

This study is designed to observe whether there is a correlation between AVB and AF, and which type of AVB has the most obvious correlation with AF.

Methods

This study retrospectively reviewed 1345 patients. We classified the AVB according to the AVB classification criteria. One hundred and two patients were excluded, and the final total sample size was 1243 patients, including 679 patients in the AF group (378, 55.7% males) and 564 patients in the non‐AF group (287, 50.8% males). AF group and non‐AF group were compared to observe the relationship between AVB and AF.

Results

The I AVB have a relative statistical risk of 1.927 (95% confidence interval [CI]: 1.160‐3.203, P < 0.05) with the occurrence of AF. II AVB occupied the largest proportion, accounting for 67 cases (9.87%), and the statistical risk of II AVB in AF is 16.845 (95% CI: 6.099‐46.524, P < 0.000). III AVB has a comparative statistical risk of 17.599 (95% CI: 4.212‐73.541, P < 0.000).

Conclusions

The three types of AVB in the AF group were significantly higher than that in the non‐AF group. II AVB has the highest incidence rate compared with other types of AVB in the AF group. AVB can be used as a risk factor for AF occurrence.

Dynamic Electrocardiography is Useful in the Diagnosis of Persistent Atrial Fibrillation Accompanied with Second-Degree Atrioventricular Block

BACKGROUND

Periodic electrocardiography (ECG) at every clinical visit is generally performed for heart rhythm surveillance, and 24-h Holter ECG is usually used as the gold standard. We aimed to investigate the electrocardiographic features of persistent atrial fibrillation (AF) accompanied with second-degree atrioventricular block (AVB).

METHODS

From October 2012 to November 2015, 204 patients with an RR interval > 2.0 s before radiofrequency ablation were included. Dynamic ECG (DCG) was performed before and after the radiofrequency ablation. The patients were divided into two groups based on changes in DCG after radiofrequency ablation: group A (non-second-degree AVB group) and group B (second-degree AVB group). An RR interval > 2.0 s, the distribution of escape rhythm, mean heart rate and the long RR interval in the two groups were analyzed.

RESULTS

After radiofrequency ablation, all 204 patients who had persistent AF converted to sinus rhythm successfully. In group A (n = 193), the distribution of an RR interval > 2.0 s and escape rhythm were significantly correlated with sleep or rest, while no correlation was observed in group B (n = 11). The average RR interval prolongation and escape rhythm were significantly higher in group B than in group A (p < 0.05). The average number of long RR intervals > 3.0 s and average number of escape rhythm episodes (< 35 bpm) were significant predictive factors of second-degree AVB after radiofrequency ablation.

CONCLUSIONS

DCG is a useful tool for the diagnosis of persistent AF accompanied with second-degree AVB.

A double-blind, randomised, placebo-controlled, cross-over study assessing the use of XEN-D0103 in patients with paroxysmal atrial fibrillation and implanted pacemakers allowing continuous beat-to-beat monitoring of drug efficacy

PURPOSE

The ultrarapid delayed rectifier current (I_Kur) carried by Kv1.5 channels, which are solely expressed in the atrium, is a potential target for safer treatment of paroxysmal atrial fibrillation (PAF). XEN-D0103 is a nanomolar ion channel blocker that selectively inhibits potassium ion flux through the Kv1.5 ion channel. The efficacy of XEN-D0103 in reducing AF burden was assessed in patients with DDDRp permanent pacemakers (PPMs) and PAF.

METHODS

A double-blind, placebo-controlled, cross-over study was performed in patients with PAF and DDDRp PPMs with advanced atrial and ventricular Holters allowing beat-to-beat arrhythmia follow-up. All anti-arrhythmic drugs were withdrawn before randomised treatment. After baseline assessment, patients were randomly assigned to two treatment periods of placebo then XEN-D0103 50 mg bd, or XEN-D0103 50 mg bd then placebo.

RESULTS

Fifty-four patients were screened and 21 patients were eligible and included in the randomised trial. All 21 patients completed both treatment periods. The primary endpoint was change in AF burden assessed by PPM. There was no significant difference in AF burden on treatment with XEN-D0103 versus placebo. There was a reduction in the mean frequency of AF episodes (relative reduction 0.72, 95% CI 0.66 to 0.77; p < 0.0001). XEN-D0103 was safe and well tolerated, and there were no serious adverse events. XEN-D0103 did not have any apparent effect on heart rate compared to placebo.

CONCLUSIONS

XEN-D0103 did not reduce AF burden in patients with PAF and dual chamber pacemakers providing beat-to-beat monitoring. XEN-D0103 was well tolerated and did not have any apparent effect on heart rate. Although single-ion channel blockade with XEN-D0103 did not affect AF in this study, there might be a potential for this agent to be used in combination with other atrially specific drugs in the treatment of AF.

EUDRACT TRIAL REGISTRATION NUMBER

2013-004456-38.

Safety and Efficacy of Inpatient Initiation of Dofetilide versus Sotalol for atrial fibrillation

Background

We sought to investigate and compare the safety and efficacy of two commonly used antiarrhythmic drugs, Dofetilide (DF) and Sotalol (SL), during inpatient drug initiation in patients with symptomatic atrial fibrillation (AF).

Methods

We performed a single center retrospective study of consecutive patients, admitted for initiation of either DF or SL, for AF between 2012 and 2015. Rates of successful cardioversion, QT interval prolongation, adverse events and drug discontinuations were calculated and compared. A two-tailed p value less than 0.05 was considered statistically significant.

Results

Of 378 patients, 298 (78.8%) received DF and 80 (21.2%) SL, mean age was 64 ± 11 years, 90% were Caucasians and 66% were males. Among the patients who remained in AF upon admission (DF: 215/298 (72%) vs. SL: 48/80 (60%)), no significant differences were noted in pharmacological cardioversion rates (DF: 125/215(58%) vs. SL: 30/48 (62.5%); p = 0.58). Baseline QTc was similar between the groups, with higher dose dependent QTc prolongation with DF (472.25± 31.3 vs. 458± 27.03; p = 0.008). There were no significant differences in the rates of adverse events such as bradycardia (7.4% vs. 11.3%; p = 0.26), Torsades de pointes (1.3% vs. 1.2%; p = 1.00), and drug discontinuation (9.0% vs. 5.0%; p = 0.47) between the two groups.

Impact of the type of centre on management of AF patients: Surprising evidence for differences in antithrombotic therapy decisions

Atrial fibrillation (AF) patients may receive treatment from specialists or from general medicine physicians representing different levels of care within a structured health care system. This “choice” is influenced by patient flow within a health care system, patient preference, and individual access to health care resources. We analysed how the postgraduate training and work environment of treating physicians affects management decisions in AF patients. Patient characteristics and treatment decisions were analysed at the time of enrolment into the registry of the German Atrial Fibrillation NETwork (AFNET). A total of 9,577 patients were enrolled from 2004 to 2006 in 191 German centres that belonged to the following four levels of care: 13 tertiary care centres (TCC) enrolled 3,795 patients (39.6%), 58 district hospitals (DH) enrolled 2,339 patients (24.4%), 62 office-based cardiologists (OC) enrolled 2,640 patients (27.6%), and 58 general practitioners or internists (GP) enrolled 803 patients (8.4%). Patients with new-onset AF were often treated in DH. TCC treated younger patients who more often presented with paroxysmal AF. Older patients and patients in permanent AF more often received outpatient care. Consistent with recommendations, younger patients and patients with non-permanent AF received rhythm control therapy more often. In addition, the type of centre affected the decision for rhythm control. Stroke risk was similar between centre types (mean CHADS2 scores 1.6 –1.9). TCC (68.8%) and OC (73.6%) administered adequate antithrombotic therapy more often than DH (55.1%) or GP (52.0%, p<0.001 between groups). Upon multivariate analysis, enrolment by TCC or OC was associated with a 1.60 (1.20–2.12, p=0.001) fold chance for adequate antithrombotic treatment. This difference between centre types was consistent irrespective of the type of stroke risk estimation (ESC 2001 guidelines, CHADS2 score), and also consistent when the recently suggested CHA2DS2-VASc score was used to estimate stroke risk. In conclusion, management decisions in AF are influenced by the education and clinical background of treating physicians in Germany. Inpatients receive more rhythm control therapy. Adequate antithrombotic therapy is more often administered in specialist (cardiologist) centres.

[Alcohol and arrhythmias]

The effects of alcohol on induction of arrhythmias is dose-dependent, independent of preexisting cardiovascular diseases or heart failure and can affect otherwise healthy subjects. While the probability of atrial fibrillation increases with the alcohol dosage, events of sudden cardiac death are less frequent with low and moderate consumption but occur more often in heavy drinkers with alcoholic cardiomyopathy. Men are first affected at higher dosages of alcohol but women can suffer from arrhythmias at lower dosages. Thromboembolisms and ischemic stroke can occur less often at lower dosages of alcohol; however, hemorrhagic stroke and subarachnoid hemorrhage are increased with higher alcohol dosages. Recognizable protective mechanisms of alcohol with respect to cardiovascular diseases only occur with lower amounts of alcohol of less than 10 g per day. Underlying mechanisms explain these controversial effects. Specific therapeutic options for alcohol-related arrhythmias apart from abstinence from alcohol consumption are not known.

Novel Scoring System for Distinction Between Paroxysmal and Non-Paroxysmal Atrial Fibrillation

BACKGROUND

Distinction of paroxysmal atrial fibrillation (PAF) from non-PAF is important in clinical practice, but this is often difficult at the time of first documented AF. Given that fibrillation cycle length (FCL) is longer in PAF than in non-PAF, the aim of this study was to compare various clinical parameters including FCL to establish a scoring system to distinguish PAF and non-PAF.Methods and Results:The subjects consisted of 382 consecutive patients with AF on digital ECG at the present institute between 2008 and 2011. They were divided into PAF and non-PAF groups according to the following clinical course. Propensity score matching yielded 88 matched patient pairs with similar mean age and gender between the 2 groups. FCL was evaluated using customized fibrillation wave analyzer with fast Fourier transform analysis. On multivariate analysis, higher HR, longer FCL, and smaller LAD were independent predictors of PAF. For the scoring, cut-offs for each parameter were determined according to highest sensitivity and specificity on the ROC curves, and 1 point assigned for each parameter. Using this scoring system, 2 points detected PAF with 64% sensitivity and 84% specificity.

CONCLUSIONS

We propose a scoring system including FCL to distinguish PAF from non-PAF. Further studies are needed to validate the results.

Antiarrhythmic Drug Therapy for Atrial Fibrillation

Atrial fibrillation (AF) is the most frequently encountered arrhythmia. Prevalence increases with advancing age and so as its associated comorbidities, like heart failure. Choice of pharmacologic therapy depends on whether the goal of treatment is maintaining sinus rhythm or tolerating AF with adequate control of ventricular rates. Antiarrhythmic therapy and conversion of AF into sinus rhythm comes with the side effect profile, and we should select best antiarrhythmic therapy, individualized to the patient. New antiarrhythmic drugs are being tested in clinical trials. Drugs that target remodeling and inflammation are being tested for their use as prevention of AF or as upstream therapy.

Cilostazol Prevents Atrial Structural Remodeling through the MEK/ERK Pathway in a Canine Model of Atrial Tachycardia

OBJECTIVES

Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice. Atrial structural remodeling (ASR), particularly atrial fibrosis, is an important contributor to the AF substrate. This study aimed to investigate the preventive effects of the phosphodiesterase 3 inhibitor cilostazol on ASR and its potential molecular mechanisms in a canine model of rapid atrial pacing (RAP).

METHODS

Thirty dogs were assigned to sham (Sham), paced/ no treatment (Paced) and paced + cilostazol 5 mg/kg/day (Paced + cilo) groups, with 10 dogs in each group. RAP at 500 beats/min was maintained for 2 weeks, while the Sham group was instrumented without pacing. Cilostazol was provided orally during pacing. Western blotting, RT-PCR and pathology were used to assess ASR.

RESULTS

Cilostazol attenuated atrial interstitial fibrosis and structural remodeling in canines with RAP. MEK/ERK transduction pathway gene expression was upregulated in the Paced group compared with the Sham group. Cilostazol markedly alleviated these changes in the MEK/ERK pathway. Transforming growth factor-β1 protein expression in the Paced group was significantly higher than in the Sham group (p < 0.01), and was significantly reduced by cilostazol (p < 0.01).

CONCLUSIONS

Our findings suggest that cilostazol is beneficial for prevention and treatment in atrial tachycardia-induced ASR in a canine model of RAP.

The Role of Platelet-Derived Growth Factor-B/Platelet-Derived Growth Factor Receptor-β Signaling in Chronic Atrial Fibrillation

OBJECTIVE

To explore the role of platelet-derived growth factor-B (PDGF-B)/platelet-derived growth factor receptor-β (PDGFR-β) signaling in chronic atrial fibrillation (AF).

METHODS

Thirty-nine AF patients and 33 patients with sinus rhythm (SR) were enrolled. Twenty canines were randomized into 5 groups: control, sham and AF lasting 1, 2 or 4 weeks. The AF canine models were made by rapid atrial pacing. Rat atrial fibroblasts were treated with PDGF-BB or PDGF-BB + PDGFR inhibitor AG1295, respectively. Gene expression in the right atrial appendage of patients, the left atrium of canines and rat atrial fibroblasts was measured by quantitative real-time PCR and Western blot, respectively. The degree of atrial fibrosis was evaluated by Masson trichrome staining.

RESULTS

The degree of atrial fibrosis and the expression of PDGF-B, PDGFR-β and collagen type I (COL1) in AF patients significantly increased compared to patients with SR. The degree of atrial fibrosis and the expression of PDGF-B and COL1 in canines increased progressively with the increased duration of AF. The expression of PDGFR-β increased progressively 2 weeks after AF. PDGF-BB promoted the proliferation and COL1 secretion of rat atrial fibroblasts. AG1295 attenuated these effects.

CONCLUSIONS

Our study suggests that PDGF-B/PDGFR-β signaling, which promotes the proliferation and COL1 secretion of atrial fibroblasts, is an important contributor to atrial fibrosis in AF and may represent a novel target for the intervention of AF.

Effects of Wild-Type and Mutant Forms of Atrial Natriuretic Peptide on Atrial Electrophysiology and Arrhythmogenesis

Background—

Atrial natriuretic peptide (ANP) is a hormone with numerous beneficial cardiovascular effects. Recently, a mutation in the ANP gene, which results in the generation of a mutant form of ANP (mANP), was identified and shown to cause atrial fibrillation in people. The mechanism(s) through which mANP causes atrial fibrillation is unknown. Our objective was to compare the effects of wild-type ANP and mANP on atrial electrophysiology in mice and humans.

Methods and Results—

Action potentials (APs), L-type Ca 2+ currents ( I Ca,L ), and Na + current were recorded in atrial myocytes from wild-type or natriuretic peptide receptor C knockout (NPR-C −/− ) mice. In mice, ANP and mANP (10–100 nmol/L) had opposing effects on atrial myocyte AP morphology and I Ca,L . ANP increased AP upstroke velocity ( V max ), AP duration, and I Ca,L similarly in wild-type and NPR-C −/− myocytes. In contrast, mANP decreased V max , AP duration, and I Ca,L , and these effects were completely absent in NPR-C −/− myocytes. ANP and mANP also had opposing effects on I Ca,L in human atrial myocytes. In contrast, neither ANP nor mANP had any effect on Na + current in mouse atrial myocytes. Optical mapping studies in mice demonstrate that ANP sped electric conduction in the atria, whereas mANP did the opposite and slowed atrial conduction. Atrial pacing in the presence of mANP induced arrhythmias in 62.5% of hearts, whereas treatment with ANP completely prevented the occurrence of arrhythmias.

Conclusions—

These findings provide mechanistic insight into how mANP causes atrial fibrillation and demonstrate that wild-type ANP is antiarrhythmic.

Anxiety disorders and physical comorbidity: increased prevalence but reduced relevance of specific risk factors for hospital-based mortality during a 12.5-year observation period in general hospital admissions

Anxiety disorders (AD) are associated with an increase in physical comorbidities, but the effects of these diseases on hospital-based mortality are unclear. Consequently, we investigated whether the burden of physical comorbidity and its relevance on hospital-based mortality differed between individuals with and without AD during a 12.5-year observation period in general hospital admissions. During 1 January 2000 and 30 June 2012, 11,481 AD individuals were admitted to seven General Manchester Hospitals. All comorbidities with a prevalence ≥ 1 % were compared with those of 114,810 randomly selected and group-matched hospital controls of the same age and gender, regardless of priority of diagnoses or specialized treatments. Comorbidities that increased the risk of hospital-based mortality (but not mortality outside of the hospital) were identified using multivariate logistic regression analyses. AD individuals compared to controls had a substantial excess comorbidity, but a reduced hospital-based mortality rate. Twenty-two physical comorbidities were increased in AD individuals compared with controls, which included cardiovascular diseases and their risk factors. The most frequent physical comorbidities in AD individuals were hypertension, asthma, cataract, and ischaemic heart disease. Risk factors for hospital-based mortality in AD individuals were lung cancer, alcoholic liver disease, respiratory failure, heart failure, pneumonia, bronchitis, non-specific dementia, breast cancer, COPD, gallbladder calculus, atrial fibrillation, and angina. The impact of atrial fibrillation, angina, and gallbladder calculus on hospital-based mortality was higher in AD individuals than in controls. In contrast, other mortality risk factors had an equal or lower impact on hospital-based mortality in sample comparisons. Therefore AD individuals have a higher burden of physical comorbidity that is associated with a reduced risk of general hospital-based mortality. Atrial fibrillation, angina, and gallbladder calculus are major risk factors for general hospital-based mortality in AD individuals.

The Association of Serum Galectin-3 Levels with Atrial Electrical and Structural Remodeling

INTRODUCTION

Left atrial (LA) interstitial fibrosis is known to have a role in the initiation and maintenance of atrial fibrillation (AF). The role of galectin-3 in the pathogenesis of cardiac fibrosis has been demonstrated in previous studies. We aimed to determine whether serum galectin-3 level is associated with markers of atrial remodeling, including the extent of LA fibrosis detected by delayed enhancement magnetic resonance imaging (DE-MRI) and atrial electromechanical delay (AEMD) in paroxysmal AF patients with preserved left ventricular (LV) functions.

METHODS AND RESULTS

Thirty-three patients (58 [28-74] years, 51.5% male) with paroxysmal AF who underwent DE-MRI prior to cryoballoon-based AF ablation were included in the study. Serum galectin-3 levels were measured with ELISA. LA volume index (B ± SE: 0.424 ± 0.504, 95% CI: 0.560-2.627, P = 0.004) and serum galectin-3 levels (B ± SE: 0.549 ± 7.745, 95% CI: 16.874-47.550, P < 0.001) were found to be independently correlated with extent of LA fibrosis detected with DE-MRI in paroxysmal AF patients with preserved LV function. Correlation analysis between AEMD parameters and baseline characteristics showed that galectin-3 was significantly correlated with intra-left (ρ = 0.432, P = 0.012) and inter-AEMD (ρ = 0.395, P = 0.023). Duration of AF, LAD, and extent of LA fibrosis were also found to be significantly correlated with AEMD parameters.

CONCLUSION

This is a hypothesis-generating study pointing out that serum galectin-3 level is significantly associated with atrial remodeling in paroxysmal AF patients with preserved LV function. Further studies are necessary to provide exact pathophysiological mechanisms.

Diabetes mellitus and atrial fibrillation: Pathophysiological mechanisms and potential upstream therapies

Diabetes mellitus (DM) represents one of the most important risk factors for atrial fibrillation (AF) while AF is a strong and independent marker of overall mortality and cardiovascular morbidity in diabetic patients. Autonomic, electrical, electromechanical, and structural remodeling, including oxidative stress, connexin remodeling and glycemic fluctuations seem to be implicated in AF pathophysiology in the setting of DM. The present review highlights the association between DM and AF, provides a comprehensive overview of the responsible pathophysiological mechanisms and briefly discusses potential upstream therapies for DM-related atrial remodeling.

Sodium tanshinone IIA sulfonate attenuates the transforming growth factor-β1-induced differentiation of atrial fibroblasts into myofibroblasts in vitro

The differentiation of atrial fibroblasts into myofibroblasts is a critical event in atrial fibrosis. One of the most important factors in atrial fibroblast differentiation is transforming growth factor-β1 (TGF-β1). Accumulating evidence indicates that sodium tanshinone IIA sulfonate (STS) possesses antifibrotic properties. In this study, we therefore investigated whether STS attenuates the TGF-β1‑induced differentiation of atrial fibroblasts. TGF-β1 enhanced collagen production, collagen synthesis and the expression of collagen type I and III, as shown by hydroxyproline assay, collagen synthesis assay and western blot analysis, respectively. In addition, as shown by immunohistochemistry and western blot analysis, TGF-β1 enhanced the expression of α-smooth muscle actin (α-SMA), which is the hallmark of myofibroblast differentiation. These responses were attenuated by treatment with STS. In addition, STS suppressed the TGF-β1‑induced expression of phosphorylated (p)Smad/pSmad3 expression and nuclear translocation. Furthermore, STS suppressed extracellular signal-regulated kinase (ERK) phosphorylation. In conclusion, the current study demonstrates that STS exerts antifibrotic effects by modulating atrial fibroblast differentiation through ERK phosphorylation and the Smad pathway.

Effects of candesartan, an angiotensin II receptor type I blocker, on atrial remodeling in spontaneously hypertensive rats

Hypertension‐induced structural remodeling of the left atrium (LA) has been suggested to involve the renin–angiotensin system. This study investigated whether treatment with an angiotensin receptor blocker, candesartan, regresses atrial remodeling in spontaneously hypertensive rats (SHR). Effects of treatment with candesartan were compared to treatment with a nonspecific vasodilatator, hydralazine. Thirty to 32‐week‐old adult male SHR were either untreated (n = 15) or received one of either candesartan cilexetil (n = 9; 3 mg/kg/day) or hydralazine (n = 10; 14 mg/kg/day) via their drinking water for 14 weeks prior to experiments. Untreated age‐ and sex‐matched Wistar‐Kyoto rats (WKY; n = 13) represented a normotensive control group. Untreated SHR were hypertensive, with left ventricular hypertrophy (LVH) compared to WKY, but there were no differences in systolic pressures in excised, perfused hearts. LA from SHR were hypertrophied and showed increased fibrosis compared to those from WKY, but there was no change in connexin‐43 expression or phosphorylation. Treatment with candesartan reduced systolic tail artery pressures of conscious SHR below those of normotensive WKY and caused regression of both LVH and LA hypertrophy. Although hydralazine reduced SHR arterial pressures to those of WKY and led to regression of LA hypertrophy, it had no significant effect on LVH. Notably, LA fibrosis was unaffected by treatment with either agent. These data show that candesartan, at a dose sufficient to reduce blood pressure and LVH, did not cause regression of LA fibrosis in hypertensive rats. On the other hand, the data also suggest that normalization of arterial pressure can lead to the regression of LA hypertrophy.

Structural remodeling of the atria, involving atria enlargement and fibrosis, in hypertension increases the risk of atrial fibrillation (AF). Treatment of spontaneously hypertensive rats with the angiotensin receptor blocker, candesartan, reduced arterial pressure and myocardial hypertrophy to the level of normotensive rats but had no effect on atrial fibrosis. The resistance of hypertension‐associated atrial fibrosis to the AT1 receptor antagonist may provide insight into the basis to the ineffectiveness of drugs targeting the renin–angiotensin system in reducing incidence of AF in hypertensive patients.

MicroRNAs and atrial fibrillation: mechanisms and translational potential

Atrial fibrillation (AF), the most common sustained arrhythmia in clinical practice, is an important contributor to cardiac morbidity and mortality. Pharmacological approaches currently available to treat patients with AF lack sufficient efficacy and are associated with potential adverse effects. Even though ablation is generally more effective than pharmacotherapy, this invasive procedure has considerable potential complications and is limited by long-term recurrences. Novel therapies based on the underlying molecular mechanisms of AF can provide useful alternatives to current treatments. MicroRNAs (miRNAs), endogenous short RNA sequences that regulate gene expression, have been implicated in the control of AF, providing novel insights into the molecular basis of the pathogenesis of AF and suggesting miRNA targeting as a potential approach for the management of this common arrhythmia. In this Review, we provide a comprehensive analysis of the current experimental evidence supporting miRNAs as important factors in AF and discuss their therapeutic implications. We first provide background information on the pathophysiology of AF and the biological determinants of miRNA synthesis and action, followed by experimental evidence for miRNA-mediated regulation of AF, and finally provide a comprehensive overview of miRNAs as potential novel therapeutic targets for AF.

Atrial apoptosis and fibrosis adversely affect atrial conduit, reservoir and contractile functions

OBJECTIVES

Chronic atrial volume overload and atrial fibrillation (AF) induce structural changes within atrial myocardium. The aim of this study was to evaluate the effect of adverse cellular remodelling on echocardiographic strain rate (SR) deformation indices of atrial contractile, conduit and reservoir functions.

METHODS

Forty-four consecutive patients with organic mitral regurgitation were analysed. Twenty-eight patients had long-standing persistent AF (AF group), while 16 were in normal sinus rhythm (NSR group). Left atrial (LA) samples were harvested from all the patients for histological analysis. Postoperative echocardiographic data acquisition was performed exclusively during organized atrial electrical activity in order to assess the contractile reserve of patients from both groups.

RESULTS

Fibrotic atria had inferior conduit (SR-E: r = -0.36, P = 0.017), reservoir (SR-S: r = -0.31, P = 0.041) and contractile functions (SR-A: r = -0.33, P = 0.027). Analogously, atria with greater apoptotic burdens showed a negative correlation with multiple indices of left atrial functions (SR-E: r = -0.38, P = 0.010; SR-S: r = -0.33, P = 0.028; SR-A: r = -0.28, P = 0.067). The efficiency of atrial contractility was significantly reduced among AF-group patients after conversion to sinus rhythm, when compared with patients in the NSR group (LA active emptying fraction: 20 ± 12 vs 30 ± 10%, P = 0.004; SR-A: 1.1 ± 1.0 vs 2.8 ± 1.9 s(-1), P < 0.001). Superior strain-rate indices of atrial conduit and reservoir functions were noted in the NSR group (SR-E: 3.5 ± 2.3 vs 1.3 ± 1.0 s(-1), P < 0.001; LA expansion index: 86 ± 31 vs 60 ± 42%, P = 0.004). Fibrosis was evident in 7.2 [3.3;9.4]% of the LA tissue sample in the AF group, while it accounted for 3.4 [1.2;8.1]% of atrial tissue in the NSR group (P = 0.054). Apoptosis was documented in 13 (46%) patients in the AF group, whereas none of the patients in the NSR group exhibited signs of programmed cell death (P = 0.001). Myocyte degeneration was more prevalent in the AF group (odds ratio: 7.0, 95% confidence interval: 1.3-36.7, P = 0.021). Age showed a positive correlation with worsening degrees of atrial fibrosis and apoptosis (r = 0.41, P = 0.006; r = 0.49, P = 0.001, respectively). Multiple regression analysis identified SR-S (β = -1.263, P = 0.036) and age (β = 0.144, P = 0.057) as independent predictors of fibrosis. Independent determinants of apoptosis were preoperative AF (β = 4.539, P = 0.007), age (β = 0.188, P = 0.009) and SR-S (β = -1.780, P = 0.002).

CONCLUSIONS

Atria exhibiting greater fibrotic and apoptotic burdens had impaired conduit, reservoir and contractile function, as evaluated by deformation imaging. Among patients with chronic LA volume overload, exposure to long-standing persistent AF induced more pronounced degrees of adverse atrial cellular remodelling. Strain-rate descriptors of atrial reservoir function harboured potential to predict atrial fibrosis and apoptosis.

Prophylactic statin administration may prevent shortening of the fibrillation cycle length in patients with new-onset atrial fibrillation

Patients with recently diagnosed atrial fibrillation (AF) tend to exhibit a longer fibrillation cycle length (FCL) than those having a longer clinical history. However, the electrophysiological properties of new-onset AF may vary because of the clinical background of patients. In this study, we evaluated clinical factors to identify the determinants of FCL in new-onset AF. Electrocardiograms (ECGs) recorded from 2008 through 2011 were analyzed using our digital ECG-profiling system. In the 1,578 AF episodes recorded, 466 new-onset AF episodes were identified using clinical referral history and previous ECGs. After evaluating FCL in these new-onset AF episodes, using a customized fibrillation wave analyzer with fast Fourier transform analysis, we divided the patients into a longer-FCL group and a shorter-FCL group using the median FCL (158 ms). Propensity score matching yielded 135 matched pairs of patients with comparable mean ages between the two groups. Four factors (brain natriuretic peptide levels, and use of angiotensin receptor blockers, calcium channel blockers or statins) exhibited a significant difference between the two groups. Multivariate analysis revealed that statin use was the only significant independent predictor of longer FCL (Odds ratio, 3.86; 95% CI, 1.659.63; P = 0.003). Among various clinical parameters, statin use was related to longer FCL at the time of new-onset AF in patients with AF.

Atrial fibrosis: a risk stratifier for atrial fibrillation

Atrial fibrillation (AF), especially persistent and long-standing persistent AF, may result in electro-anatomical changes in the left atrium, resulting in remodeling and deposition of fibrous tissue. There are emerging data that atrial substrate modification may increase the risk of thromboembolic complications, including stroke. Several studies have reported that atrial fibrosis is due to complex interactions among several cellular and neurohumoral mediators. Late gadolinium enhancement MRI has been reported to allow quantitative assessment of myocardial fibrosis in patients at risk of developing a stroke. Current stroke risk stratification criteria for AF do not utilize atrial fibrosis as an independent risk factor despite its association with AF and stroke. Further research is required in developing adequate risk stratification tools for predicting the stroke risk and catheter ablation outcomes in AF.