The effect of atrial dilatation on the genesis of atrial arrhythmias

Characteristics and Outcomes of Atrial Fibrillation in Chronic Heart Failure Patients: A Comprehensive Analysis of the Colombian Heart Failure Registry

Background

Heart failure (HF) and atrial fibrillation (AF) represent conditions that commonly coexist. The impact of AF in HF has yet to be well studied in Latin America. This study aimed to characterize the sociodemographic and clinical features, along with patients' outcomes with AF and HF from the Colombian Heart Failure Registry (RECOLFACA).

Methods

Patients with ambulatory HF and AF were included in RECOLFACA, mainly with persistent or permanent AF. A 6-month follow-up was performed. Primary outcome was all-cause mortality. To assess the impact of AF on mortality, we used a logistic regression model. A P value of < 0.05 was considered significant. All statistical tests were two-tailed.

Results

Of 2,528 patients with HF in the registry, 2,514 records included information regarding AF diagnosis. Five hundred sixty (22.3%) were in AF (mean age 73 ± 11, 56% men), while 1,954 had no AF (mean age 66 ± 14 years, 58% men). Patients with AF were significantly older and had a different profile of comorbidities and implanted devices compared to non-AF patients. Moreover, AF diagnosis was associated with lower quality of life score (EuroQol-5D), mainly in mobility, personal care, and daily activity. AF was prevalent in patients with preserved ejection fraction (EF), while no significant differences in N-terminal prohormone of brain natriuretic peptide (NT-proBNP) levels were observed. Although higher mortality was observed in the AF group compared to individuals without AF (8.9% vs. 6.1%, respectively; P = 0.016), this association lost statistical significance after adjusting by age in a multivariate regression model (odds ratio (OR): 1.35; 95% confidence interval (CI): 0.95 - 1.92).

Conclusions

AF is more prevalent in HF patients with higher EF, lower quality of life and different clinical profiles. Similar HF severity and non-independent association with mortality were observed in our cohort. These results emphasize the need for an improved understanding of the AF and HF coexistence phenomenon.

Development of a novel low-order model for atrial function and a study of atrial mechano-electric feedback

Numerical models of the cardiovascular system have largely focused on the function of the ventricles, with atrial function often neglected. Furthermore, the time-varying elastance method that prescribes the pressure-volume relationship rather than calculating it consistently is frequently used for the ventricles and atrium. This method has yet to be validated however, so its applicability for cardiac modelling is frequently questioned. To overcome this challenge, we propose a synergistic model of left atrium (LA) and left ventricle (LV) by self-consistently integrating various feedback mechanisms among the electro-mechanical and chemical functions of the micro-scale myofiber, the macro-scale dynamics of the LA and LV, the atrioventricular node (AV), and circulation. The model is tested and shown to reproduce the essential features of the atrium cycling, such as the characteristic figure of eight pressure-volume loops. Our model is further developed to investigate the effect of dysfunctions of the mechanical-electric feedback (MEF) in the atrium. Our model not only successfully reproduces key experimental MEF observations such as prolonged action-potential and increases in action-potential magnitude induced by atrial stretch but also shows how MEF and arrhythmia of the atrium lead to a degradation of cardiac output and pumping power with significant consequences. In particular, MEF reproduces arrhythmia such as ectopic and erratic cycling, missed heart beats and restricted function.

Electro-Mechanical Alterations in Atrial Fibrillation: Structural, Electrical, and Functional Correlates

Atrial fibrillation is the most common arrhythmia encountered in clinical practice affecting both patients’ survival and well-being. Apart from aging, many cardiovascular risk factors may cause structural remodeling of the atrial myocardium leading to atrial fibrillation development. Structural remodelling refers to the development of atrial fibrosis, as well as to alterations in atrial size and cellular ultrastructure. The latter includes myolysis, the development of glycogen accumulation, altered Connexin expression, subcellular changes, and sinus rhythm alterations. The structural remodeling of the atrial myocardium is commonly associated with the presence of interatrial block. On the other hand, prolongation of the interatrial conduction time is encountered when atrial pressure is acutely increased. Electrical correlates of conduction disturbances include alterations in P wave parameters, such as partial or advanced interatrial block, alterations in P wave axis, voltage, area, morphology, or abnormal electrophysiological characteristics, such as alterations in bipolar or unipolar voltage mapping, electrogram fractionation, endo-epicardial asynchrony of the atrial wall, or slower cardiac conduction velocity. Functional correlates of conduction disturbances may incorporate alterations in left atrial diameter, volume, or strain. Echocardiography or cardiac magnetic resonance imaging (MRI) is commonly used to assess these parameters. Finally, the echocardiography-derived total atrial conduction time (PA-TDI duration) may reflect both atrial electrical and structural alterations.

Protocol of BEYOND trial: Clinical BEnefit of sodium-glucose cotransporter-2 (SGLT-2) inhibitors in rhYthm cONtrol of atrial fibrillation in patients with diabetes mellitus

SGLT-2 inhibitor, traditionally used for glycemic control, has several beneficial effects that can help manage heart failure (HF). SGLT-2 inhibitors reduce the risk of cardiovascular mortality in patients with HF. As atrial fibrillation (AF) is closely associated with HF and diabetes mellitus (DM) is a risk factor for AF, we assume that SGLT-2 inhibitors will also show therapeutic benefits regarding AF, especially for rhythm control. This trial has a multicenter, prospective, open, blinded endpoint design. It is a 1:1 randomized and controlled study. A total of 716 patients who are newly diagnosed of AF and DM within 1 year will be enrolled from 7 tertiary medical centers. The trial is designed to compare the effects of SGLT-2 inhibitors and other oral hypoglycemic agents on atrial rhythm control in patients with AF and DM. The primary outcome is the recurrence of AF within a year (including post-antiarrhythmic drugs (AAD) or ablation). The secondary outcomes are the ablation rate within a year, change in AF burden, size of the left atrium, NT-proBNP, the AF symptom score, and the quality of life. This trial will prospectively evaluate the effect and safety of SGLT-2 inhibitors on AF rhythm control in patients with DM. It will provide an invaluable dataset on rhythm control in AF with DM for future studies and offer novel information to assist in clinical decisions. (BEYOND trial, ClinicalTrials.gov number: NCT05029115. https://clinicaltrials.gov/ct2/show/NCT05029115).

Pharmacologic Rate versus Rhythm Control for Atrial Fibrillation in Heart Failure Patients

Atrial fibrillation (AF) and Heart failure (HF) constitute two frequently coexisting cardiovascular diseases, with a great volume of the scientific research referring to strategies and guidelines associated with the best management of patients suffering from either of the two or both of these entities. The common pathophysiological paths, the adverse outcomes, the hospitalization rates, and the mortality rates that occur from various reports and trials indicate that a targeted therapy to the common background of these cardiovascular conditions may reverse the progression of their interrelating development. Among other optimal treatments concerning the prevalence of both AF and HF, the introduction of rhythm and rate control strategies in the guidelines has underlined the importance of sinus rhythm and heart rate control in the prevention of deleterious complications. The use of these strategies in the clinical practice has led to a debate about the superiority of rhythm versus rate control. The current guidelines as well as the published randomized trials and studies have not proved that rhythm control is more beneficial than the rate control treatments in the terms of survival, all-cause mortality, hospitalization rates, and quality of life. Therefore, the current therapeutic strategy is based on the therapy guidelines and the clinical judgment and experience. The aim of this review was to elucidate the endpoints of pharmacologic randomized clinical trials and the clinical data of each antiarrhythmic or rate-limiting medication, so as to promote their effective, individualized, evidence-based clinical use.

Heart failure with preserved ejection fraction: An alternative paradigm to explain the clinical implications of atrial fibrillation

Atrial fibrillation (AF) is associated with exercise intolerance, stroke, and all-cause mortality. However, whether this can be solely attributable to the arrhythmia itself or alternative mechanisms remains controversial. Heart failure with preserved ejection (HFpEF) commonly coexists with AF and may contribute to the poor outcomes associated with AF. Indeed, several invasive hemodynamic studies have confirmed that patients with AF are at increased risk of underlying HFpEF and that the presence of HFpEF may have important prognostic implications in these patients.

Mechanistically, AF and HFpEF are closely linked. Both conditions are driven by the presence of common cardiovascular risk factors and are associated with left atrial (LA) myopathy, characterized by mechanical and electrical dysfunction. Progressive worsening of this left atrial (LA) myopathy is associated with both increased AF burden and worsening HFpEF. In addition, there is growing evidence to suggest that worsening LA myopathy is associated with poorer outcomes in both conditions and that reversal of the LA myopathy could improve outcomes. In this review article, we will present the epidemiologic and mechanistic evidence underlying the common coexistence of AF and HFpEF, discuss the importance of a progressive LA myopathy in the pathogenesis of both conditions, and review the evidence from important invasive hemodynamic studies. Finally, we will review the prognostic implications of HFpEF in patients with AF and discuss the relative merits of AF burden reduction vs HFpEF reduction in improving outcomes of patients with AF and HFpEF.

Atrial fibrillation and heart failure: A contemporary review of current management approaches

Atrial fibrillation (AF) and heart failure (HF) frequently coexist and complicate the course of treatment of each other. AF with rapid ventricular conduction can lead to tachycardia-mediated cardiomyopathy, which is a reversible cause of cardiomyopathy. However, in most cases, AF is the manifestation of various underlying cardiomyopathies. Guideline-directed pharmacological and device therapy for HF is essential. The management options for AF and HF include pharmacological rhythm control, pharmacological rate control, and interventional approaches, which include catheter ablation for AF via pulmonary vein isolation and atrioventricular node ablation. This is a contemporary review to discuss the available evidence regarding the various management approaches in this specific patient group.

Heart failure and atrial fibrillation: new concepts in pathophysiology, management, and future directions

A bidirectional pathophysiological link connects heart failure and atrial fibrillation, creating a frequent and challenging comorbidity, which includes neurohormonal hyperactivation, fibrosis development, and electrophysiologic remodeling, while they share mutual risk factors. Management for these devastating comorbidities includes most of the established treatment measures for heart failure as well as rhythm or rate control and anticoagulation mostly for atrial fibrillation, which can be achieved with either pharmaceutical or non-pharmaceutical approaches. The current manuscript aims to review the existing literature regarding the underlying pathophysiology, to present the novel trends of treatment, and to predict the future perspective of these two linked diseases with the numerous unanswered questions.

Managing Atrial Fibrillation in Patients With Heart Failure and Reduced Ejection Fraction: A Scientific Statement From the American Heart Association

Atrial fibrillation and heart failure with reduced ejection fraction are increasing in prevalence worldwide. Atrial fibrillation can precipitate and can be a consequence of heart failure with reduced ejection fraction and cardiomyopathy. Atrial fibrillation and heart failure, when present together, are associated with worse outcomes. Together, these 2 conditions increase the risk of stroke, requiring oral anticoagulation in many or left atrial appendage closure in some. Medical management for rate and rhythm control of atrial fibrillation in heart failure remain hampered by variable success, intolerance, and adverse effects. In multiple randomized clinical trials in recent years, catheter ablation for atrial fibrillation in patients with heart failure and reduced ejection fraction has shown superiority in improving survival, quality of life, and ventricular function and reducing heart failure hospitalizations compared with antiarrhythmic drugs and rate control therapies. This has resulted in a paradigm shift in management toward nonpharmacological rhythm control of atrial fibrillation in heart failure with reduced ejection fraction. The primary objective of this American Heart Association scientific statement is to review the available evidence on the epidemiology and pathophysiology of atrial fibrillation in relation to heart failure and to provide guidance on the latest advances in pharmacological and nonpharmacological management of atrial fibrillation in patients with heart failure and reduced ejection fraction. The writing committee's consensus on the implications for clinical practice, gaps in knowledge, and directions for future research are highlighted.

Atrial fibrillation in patients with systolic heart failure: pathophysiology mechanisms and management

Heart failure (HF) and atrial fibrillation (AF) demonstrate a constantly increasing prevalence during the 21^st century worldwide, as a result of the aging population and the successful interventions of the clinical practice in the deterioration of adverse cardiovascular outcomes. HF and AF share common risk factors and pathophysiological mechanisms, creating the base of a constant interrelation. AF impairs systolic and diastolic function, resulting in the increasing incidence of HF, whereas the structural and neurohormonal changes in HF with preserved or reduced ejection fraction increase the possibility of the AF development. The temporal relationship of the development of either condition affects the diagnostic algorithms, the prognosis and the ideal therapeutic strategy that leads to euvolaemia, management of non-cardiovascular comorbidities, control of heart rate or restoration of sinus rate, ventricular synchronization, prevention of sudden death, stroke, embolism, or major bleeding and maintenance of a sustainable quality of life. The indicated treatment for the concomitant HF and AF includes rate or/and rhythm control as well as thromboembolism prophylaxis, while the progress in the understanding of their pathophysiological interdependence and the introduction of the genetic profiling, create new paths in the diagnosis, the prognosis and the prevention of these diseases.

The common characteristics and mutual effects of heart failure and atrial fibrillation: initiation, progression, and outcome of the two aging-related heart diseases

Atrial fibrillation (AF) and heart failure (HF) are common chronic diseases noted in humans. AF and HF share several risk factors, such as age, hypertension, obesity, diabetes, and dyslipidemia. They can interact with each other, while both their morbidity and mortality have been considerably increased. And AF and HF often occur together, suggesting a strong association between the two. However, the underlying mechanism behind this association is not well understood. Among them, aging is the most significant common risk factor, which represents an aging heart and is characterized by fibrosis and decreased number of cardiomyocytes, known as senescence-related cardiac remodeling for both atria and ventricles. Finally, it is proposed that cardiac remodeling is the key link between AF and HF.

Atrial Fibrillation and Heart Failure: Epidemiology, Pathophysiology, Prognosis, and Management

Atrial fibrillation (AF) and heart failure (HF) have similar risk factors, frequently coexist, and potentiate each other in a vicious cycle. Evidence suggests the presence of AF in both HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF) increases the risk of all-cause mortality and stroke, particularly when AF is incident. Catheter ablation may be an effective strategy in controlling symptoms and improving quality of life in AF-HFrEF. Strong data guiding management of AF-HFpEF are lacking largely due to its challenging diagnosis. Improving outcomes associated with these coexistent conditions requires further careful investigation.

Heart Failure and Atrial Fibrillation, Like Fire and Fury

Heart failure and atrial fibrillation are 2 common cardiovascular disorders that frequently complicate one another and exert a significant detrimental effect on cardiovascular health and well-being. Both heart failure and atrial fibrillation continue to increase in prevalence as the risk factors underlying each condition become more common. This review encompasses what is currently known about the epidemiology and pathophysiology of these comorbidities along with incorporation of landmark trials that have contributed to current guidelines. The focus is on clinically relevant considerations, including the contribution of inflammation in the pathophysiology of atrial fibrillation and heart failure. We explore the emerging role of catheter ablation relative to medical therapy in the management of heart failure with reduced ejection fraction, along with indications for biventricular pacing modalities in cardiac resynchronization therapy. We discuss current guideline-directed therapies and how practice models and national recommendations will likely change based on the most recent randomized controlled trials.

Cardiac Mechano-Electric Coupling: Acute Effects of Mechanical Stimulation on Heart Rate and Rhythm

The heart is vital for biological function in almost all chordates, including humans. It beats continually throughout our life, supplying the body with oxygen and nutrients while removing waste products. If it stops, so does life. The heartbeat involves precise coordination of the activity of billions of individual cells, as well as their swift and well-coordinated adaption to changes in physiological demand. Much of the vital control of cardiac function occurs at the level of individual cardiac muscle cells, including acute beat-by-beat feedback from the local mechanical environment to electrical activity (as opposed to longer term changes in gene expression and functional or structural remodeling). This process is known as mechano-electric coupling (MEC). In the current review, we present evidence for, and implications of, MEC in health and disease in human; summarize our understanding of MEC effects gained from whole animal, organ, tissue, and cell studies; identify potential molecular mediators of MEC responses; and demonstrate the power of computational modeling in developing a more comprehensive understanding of ‟what makes the heart tick.ˮ.

Arrhythmia susceptibility in a rat model of acute atrial dilation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, associated with an increased risk of stroke and heart failure. Acute AF occurs in response to sudden increases of atrial hemodynamic load, leading to atrial stretch. The mechanisms of stretch-induced AF were investigated in large mammals with controversial results. We optimized an approach to monitor rat atrial electrical activity using a red-shifted voltage sensitive dye (VSD). The methodology includes cauterization of the main ventricular coronary arteries, allowing improved atrial staining by the VSD and appropriate atrial perfusion for long experiments. Next, we developed a rat model of acute biatrial dilation (ABD) through the insertion of latex balloons into both atria, which could be inflated with controlled volumes. A chronic model of atrial dilation (spontaneous hypertensive rats; SHR) was used for comparison. ABD was performed on atria from healthy Wistar-Kyoto (WKY) rats (WKY-ABD). The atria were characterized in terms of arrhythmias susceptibility, action potential duration and conduction velocity. The occurrence of arrhythmias in WKY-ABD was significantly higher compared to non-dilated WKY atria. In WKY-ABD we found a reduction of conduction velocity, similar to that observed in SHR atria, while action potential duration was unchanged. Low-dose caffeine was used to introduce a drop of CV in WKY atria (WKY-caff), quantitatively similar to the one observed after ABD, but no increased arrhythmia susceptibility was observed with caffeine only. In conclusion, CV decrease is not sufficient to promote arrhythmias; enlargement of atrial surface is essential to create a substrate for acute reentry-based arrhythmias.

Comorbidities in chronic heart failure: An update from Italian Society of Cardiology (SIC) Working Group on Heart Failure

The increasing number of patients with heart failure HF and comorbidities is due to aging population and increase of life expectancy of patients with cardiovascular disease. Encouraging results derived by recent trials may suggest some comorbidities as new targets for new drugs, highlighting the need for a better understanding of the comorbidities' effects in HF patients and the need of a multidisciplinary approach for the management of chronic HF with comorbidities. We report a brief review about main cardiovascular and non-cardiovascular comorbidities in HF patients in order to update physicians and researchers engaged in the HF research or in "fight against heart failure."

Acute Left Ventricular Unloading Reduces Atrial Stretch and Inhibits Atrial Arrhythmias

BACKGROUND

Left atrium (LA) physiology is influenced by changes in left ventricular (LV) performance and load.

OBJECTIVES

The purpose of this study was to define the effect of acute changes in LV loading conditions on LA physiology in subacute myocardial infarction (MI).

METHODS

MI was percutaneously induced in 19 Yorkshire pigs. One to 2 weeks after MI, 14 pigs underwent acute LV unloading using a percutaneous LV assist device, Impella. The remaining 5 pigs underwent acute LV loading by percutaneous induction of aortic regurgitation. A pressure-volume catheter was inserted into the LA using a percutaneous transseptal approach, and LA pressure-volume loops were continuously monitored. Atrial arrhythmia inducibility was examined by burst-pacing of the right atrium. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) levels and ryanodine receptor phosphorylation were examined in LA tissues to study the potential effect of stretch-dependent oxidative stress.

RESULTS

MI resulted in reduced LV ejection fraction and increased LV end-diastolic pressure with concomitant increase in LA pressure and volumes. Acute LV unloading resulted in a reduction of LV end-diastolic pressure, which led to proportional decreases in mean LA pressure and maximum LA volume. LA pressure-volume loops exhibited a pump flow-dependent, left-downward shift. This was associated with reduced LA passive stiffness, suggesting the alleviation of the LA stretch that was present after MI. Prior to acute unloading of the LV, 71% of the pigs were arrhythmia-inducible; LV unloading reduced this to 29% (p = 0.02). Time to spontaneous termination of atrial arrhythmias was decreased from median 55 s (range 5 to 300 s) to 3 s (range 0 to 59 s). In contrast, acute LV loading with aortic regurgitation increased LA pressure without a significant effect on arrhythmogenicity. Molecular analysis of LA tissue revealed that NOX2 expression was increased after MI, whereas acute LV unloading reduced NOX2 levels and diminished ryanodine receptor phosphorylation.

CONCLUSIONS

Acute LV unloading relieves LA stretch and reduces atrial arrhythmogenicity in subacute MI.

Biomarkers in Atrial Fibrillation and Heart Failure

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice and an important contributor to cardiovascular morbidity and mortality. Although the exact mechanisms behind AF are not completely elucidated, the underlying pathophysiological changes have been well described. Predisposal factors for AF include the older age, the increased left atrial size, the decreased left atrial function, the presence of heart failure and left ventricular systolic dysfunction and the presence of coronary heart disease or pulmonary or mitral valve disease. In addition to these factors, emerging evidence demonstrate that myocardial strain, fibrosis and inflammation, are associated with AF as well as the pathogenesis of the arrhythmia. The natruretic peptide system including Atrial Natriuretic Peptide (ANP), Brain Natriuretic Peptide (BNP) and C-type Natriuretic Peptide (CNP) is indicative of the level of myocardial strain which may predispose to AF. As a result, the aforementioned peptides are increased in AF patients. The levels of myocardial fibrosis biomarkers, such as ST2 and Galectin-3, are elevated suggesting atrial structural abnormalities, while the increased levels of CRP and Interleukin-6 supplement the inflammatory profile of AF patients. Emerging data for the aforementioned biomarkers are discussed in the present review.

Atrial Fibrillation Ablation Should Be First-Line Therapy in Heart Failure Patients: CON

Heart failure (HF) and atrial fibrillation (AF) are the epidemics of the twenty-first century. These often coexist and are the cause of major morbidity and mortality. Management of these patients has posed a significant challenge to the medical community. Guideline-directed pharmacologic therapy for heart failure is important; however, there is no clear consensus on how best to treat AF with concomitant HF. In this article, we provide an in-depth review of the management of AF in patients with HF and provide insight as to why catheter ablation should not be the first line of therapy in this population.

Increased thin filament activation enhances alternans in human chronic atrial fibrillation

Action potential duration (APD) alternans (APD-ALT), defined as beat-to-beat oscillations in APD, has been proposed as an important clinical marker for chronic atrial fibrillation (cAF) risk when it occurs at pacing rates of 120-200 beats/min. Although the ionic mechanisms for occurrence of APD-ALT in human cAF at these clinically relevant rates have been investigated, little is known about the effects of myofilament protein kinetics on APD-ALT. Therefore, we used computer simulations of single cell function to explore whether remodeling in myofilament protein kinetics in human cAF alters the occurrence of APD-ALT and to uncover how these mechanisms are affected by sarcomere length and the degree of cAF-induced myofilament remodeling. Mechanistically based, bidirectionally coupled electromechanical models of human right and left atrial myocytes were constructed, incorporating both ionic and myofilament remodeling associated with cAF. By comparing results from our electromechanical model with those from the uncoupled ionic model, we found that intracellular Ca2+ concentration buffering of troponin C has a dampening effect on the magnitude of APD-ALT (APD-ANM) at slower rates (150 beats/min) due to the cooperativity between strongly bound cross-bridges and Ca2+-troponin C binding affinity. We also discovered that cAF-induced enhanced thin filament activation enhanced APD-ANM at these clinically relevant heart rates (150 beats/min). In addition, longer sarcomere lengths increased APD-ANM, suggesting that atrial stretch is an important modulator of APD-ALT. Together, these findings demonstrate that myofilament kinetics mechanisms play an important role in altering APD-ALT in human cAF. NEW & NOTEWORTHY Using a single cell simulation approach, we explored how myofilament protein kinetics alter the formation of alternans in action potential duration (APD) in human myocytes with chronic atrial fibrillation remodeling. We discovered that enhanced thin filament activation and longer sarcomere lengths increased the magnitude of APD alternans at clinically important pacing rates of 120-200 beats/min. Furthermore, we found that altered intracellular Ca2+ concentration buffering of troponin C has a dampening effect on the magnitude of APD alternans.

Calcium in the Pathophysiology of Atrial Fibrillation and Heart Failure

Atrial fibrillation (AF) is commonly associated with heart failure. A bidirectional relationship exists between the two-AF exacerbates heart failure causing a significant increase in heart failure symptoms, admissions to hospital and cardiovascular death, while pathological remodeling of the atria as a result of heart failure increases the risk of AF. A comprehensive understanding of the pathophysiology of AF is essential if we are to break this vicious circle. In this review, the latest evidence will be presented showing a fundamental role for calcium in both the induction and maintenance of AF. After outlining atrial electrophysiology and calcium handling, the role of calcium-dependent afterdepolarizations and atrial repolarization alternans in triggering AF will be considered. The atrial response to rapid stimulation will be discussed, including the short-term protection from calcium overload in the form of calcium signaling silencing and the eventual progression to diastolic calcium leak causing afterdepolarizations and the development of an electrical substrate that perpetuates AF. The role of calcium in the bidirectional relationship between heart failure and AF will then be covered. The effects of heart failure on atrial calcium handling that promote AF will be reviewed, including effects on both atrial myocytes and the pulmonary veins, before the aspects of AF which exacerbate heart failure are discussed. Finally, the limitations of human and animal studies will be explored allowing contextualization of what are sometimes discordant results.

Increased left atrial size is associated with higher atrial fibrillation recurrence in patients treated with antiarrhythmic medications

BACKGROUND

Atrial fibrillation (AF) is highly prevalent, and antiarrhythmic therapy is often used to help with rhythm control. Some common echocardiographic parameters may be useful in predicting AF recurrence among these patients. The purpose of this study was to evaluate the association between 3 common echocardiographic parameters (left atrial [LA] size, left ventricular ejection fraction [LVEF], and mitral regurgitation [MR]) and AF recurrence among patients treated with antiarrhythmic medications.

HYPOTHESIS

We hypothesized that LA size, LVEF, and severity of MR are predictors of AF recurrence in this population.

METHODS

A real-world cohort of AF patients who had transthoracic echocardiograms was analyzed. Data on LA size, LVEF, and MR were collected retrospectively from echocardiography reports. Patients were followed from the time of the echocardiogram until first recurrence of AF.

RESULTS

A total of 2522 patients had echocardiography reports available for review. LA size showed the strongest prognostic relationship with AF recurrence; neither LVEF nor MR was significantly associated with AF recurrence. These results persisted after adjusting for age, sex, race, tobacco use, alcohol use, drug use, body mass index, and Charlson Comorbidity Index in a multivariable model.

CONCLUSIONS

In a cohort of patients treated with antiarrhythmic medications that had transthoracic echocardiogram data, LA size was a significant predictor of AF recurrence. The clinical utility of this finding would be strengthened by replication in a multicenter setting.

Impact and treatment success of new-onset atrial fibrillation with rapid ventricular rate development in the surgical intensive care unit

BACKGROUND

Atrial fibrillation (AF) with rapid ventricular rate (RVR; heart rate >100) in noncardiac postoperative surgical patients is associated with poor outcomes. The objective of this study was to evaluate the practice patterns of AF management in a surgical intensive care unit to determine practices associated with rate and rhythm control and additional outcomes.

MATERIALS AND METHODS

Adult patients (≥18 y) admitted to the surgical intensive care unit (SICU) from June 2014 to June 2015 were retrospectively screened for the development of new-onset AF with RVR. Demographics, hospital course, evaluation and treatment of AF with RVR, and outcome were evaluated and analyzed.

RESULTS

Thousand seventy patients were admitted to the SICU during the study period; 33 met inclusion criteria (3.1%). Twenty-six patients (79%) had rate and rhythm control within 48 h of AF with RVR onset. β-Blockers were the most commonly used initial medication (67%) but were successful at rate and rhythm control in only 27% of patients (6/22). Amiodarone had the highest rate of success if used initially (5/6, 83%) and secondarily (11/13, 85%). Failure to control rate and rhythm was associated with a greater likelihood of comorbidities (100% versus 57%; P = 0.06).

CONCLUSIONS

New-onset AF with RVR in the noncardiac postoperative patient is associated with a high mortality (21%). Amiodarone is the most effective treatment for rate and rhythm control. Failure to establish rate and rhythm control was associated with cardiac comorbidities. These results will help to form future algorithms for the treatment of AF with RVR in the SICU.

Progression and reversibility of stretch induced atrial remodeling: Characterization and clinical implications

Atrial fibrillation (AF) is the most common sustained arrhythmia and across the developed nations, it contributes to increasing hospitalizations and healthcare burden. Several comorbidities and risk factors including hypertension, heart failure, obstructive sleep apnoea and obesity are known to play an important role in the initiation and perpetuation of AF and atrial stretch or dilatation may play a central mechanistic role. The impact of atrial stretch in the development of AF can vary dependent on the underlying disease. This review focuses on understanding the substrate for AF in conditions of acute and chronic stretch and in the presence of common co-morbidities or risk factors through the review of findings in both animal and human studies. Additionally, the reversibility of atrial remodeling following stretch release will also be discussed. Identification of clinical conditions associated with increased atrial stretch as well as the treatment or prevention of these conditions may help to prevent AF progression and improve sinus rhythm maintenance.

Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers Are Associated With Improved Outcome but Do Not Prevent New-Onset Atrial Fibrillation After Acute Myocardial Infarction

BACKGROUND

Treatment with renin-angiotensin system (RAS) inhibitors might restrain the structural/electrical remodeling associated with atrial fibrillation (AF). Limited evidence exists regarding the potential benefits of RAS inhibition post-acute myocardial infarction (AMI) in patients with AF. This study sought to assess the association between RAS inhibition and all-cause mortality and new-onset AF in patients with/without congestive heart failure (CHF) post-AMI.

METHODS AND RESULTS

Patients hospitalized for AMI between 2006 and 2012 were identified in Swedish registries. Patients were stratified in 4 subgroups; patients with CHF and AF (n=11 489); patients with CHF without AF (n=31 676); patients with AF without CHF (n=10 066); and patients without both CHF and AF (n=59 417). Patients exposed to RAS inhibition were compared to nontreated. Three-year risk of all-cause mortality and new-onset AF was assessed using adjusted Cox regression analyses. At discharge, 83 291 (73.9%) patients received RAS inhibition. RAS inhibition was associated with lower 3-year risk of all-cause mortality in CHF patients with AF, adjusted hazard ratio (HR) with 95% CI 0.75 (0.70-0.81), CHF patients without AF, HR 0.65 (0.60-0.69), AF patients without CHF, HR 0.82 (0.75-0.90), and in patients without CHF and AF, HR 0.76 (0.72-0.81), respectively. RAS inhibition was not associated with lower 3-year risk of new-onset AF in patients without AF but with/without CHF; HR 0.96 (0.84-1.10) and 1.12 (1.02-1.22), respectively.

CONCLUSIONS

RAS inhibition post-AMI was associated with lower risk of all-cause mortality. In patients with/without CHF, RAS inhibition was not associated with lower incidence of new-onset AF.

Effects of RAAS Blockers on Atrial Fibrillation Prophylaxis

Background:

Impact of atrial fibrillation on clinical outcomes is well recognized, and application of renin–angiotensin–aldosterone system (RAAS) blockers for the prevention of atrial fibrillation (AF) is a theoretically appealing concept. However, clinical trials have yielded inconsistent results.

Methods:

A pooled study of 26 randomized controlled trials (RCTs) assessing the efficacy of RAAS blockers on AF prophylaxis was performed.

Results:

A total of 28 reports from 26 randomized controlled trials enrolled 165 387 patients, with an overall 24% reduction in the incidence of AF (odds ratio [OR]: 0.76, 95% confidence interval [CI]: 0.68-0.85], P = .000). Forty-nine percent reduction in the incidence of AF (OR: 0.51, 95% CI: 0.30-0.85, P = .010) in systolic heart failure was observed, whereas no significant effect was observed in patients with diastolic heart failure, postmyocardial infarction, and high cardiovascular disease risk. There was a 19% (OR: 0.81, 95% CI: 0.67-1.00, P = .037) reduction in new-onset and 54% (OR: 0.46, 95% CI: 0.33-0.62, P = .000) reduction in recurrent AF in hypertensive patients with 39% (OR: 0.61, 95% CI: 0.44-0.84, P = .003) risk reduction against calcium blockers and 41% (OR: 0.59, 95% CI: 0.44-0.80, P = .001) risk reduction against β blockers. Angiotensin-receptor blocker appeared marginally superior to angiotensin-converting enzyme inhibitor in primary and secondary prevention.

Conclusion:

This study suggests that RAAS blockade effectively suppresses AF in systolic heart failure, and hypertensives derive greater benefit against new-onset and recurrent AF compared to β blockers, calcium channel blockers, and diuretics.

Impact of B-type natriuretic peptide level on the risk of left atrial appendage thrombus in patients with nonvalvular atrial fibrillation: a prospective study

Background

The impact of B-type natriuretic peptide (BNP) level on the risk of left atrial appendage (LAA) thrombus in patients with nonvalvular atrial fibrillation (NVAF) has not been prospectively studied.

Methods

In two academic medical centers, we obtained BNP levels immediately prior to transesophageal echocardiogram performed to exclude LAA thrombus in patients with NVAF.

Results

Among 261 subjects (mean age 65 ± 12 years; 30 % women) with NVAF, 17 (6.5 %) had LAA thrombus and 85 (32.6 %) had at least mild spontaneous echo contrast (SEC). Mean BNP level was significantly higher in patients with LAA thrombus [775 ± 678 vs. 384 ± 537, P = 0.001]. Receiver operator characteristics analysis demonstrated that BNP has a good discriminatory capacity for LAA thrombus (area under the curve, 0.74; 95 % confidence interval [CI], 0.63–0.85; P = 0.001); BNP ≥ 67 pg/mL was 100 % sensitive and 20 % specific for LAA thrombus. Multivariate logistic regression analysis demonstrated that BNP was not independently associated with LAA thrombus (odds-ratio, 1.05 per 100 pg/mL increment; CI, 0.99–1.12; P = 0.127) after adjusting for CHA₂DS₂-VASc score; while the latter was independently associated with LAA thrombus after adjusting for BNP level (odds-ratio, 1.46 per CHA₂DS₂-VASc point; CI, 1.09–1.96; P = 0.011). Nonetheless, BNP was associated with SEC in univariate and multivariate analysis, after adjusting for the CHA₂DS₂-VASc score, (odds-ratio, 1.08; CI, 1.02–1.14; P = 0.005).

Conclusions

BNP is predictive of SEC. However, it does not provide significant incremental value in the prediction of LAA thrombus.

Atrial fibrillation: mechanisms, therapeutics, and future directions

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia, affecting 1% to 2% of the general population. It is characterized by rapid and disorganized atrial activation leading to impaired atrial function, which can be diagnosed on an EKG by lack of a P-wave and irregular QRS complexes. AF is associated with increased morbidity and mortality and is a risk factor for embolic stroke and worsening heart failure. Current research on AF support and explore the hypothesis that initiation and maintenance of AF require pathophysiological remodeling of the atria, either specifically as in lone AF or secondary to other heart disease as in heart failure-associated AF. Remodeling in AF can be grouped into three categories that include: (i) electrical remodeling, which includes modulation of L-type Ca(2+) current, various K(+) currents and gap junction function; (ii) structural remodeling, which includes changes in tissues properties, size, and ultrastructure; and (iii) autonomic remodeling, including altered sympathovagal activity and hyperinnervation. Electrical, structural, and autonomic remodeling all contribute to creating an AF-prone substrate which is able to produce AF-associated electrical phenomena including a rapidly firing focus, complex multiple reentrant circuit or rotors. Although various remodeling events occur in AF, current AF therapies focus on ventricular rate and rhythm control strategies using pharmacotherapy and surgical interventions. Recent progress in the field has started to focus on the underlying substrate that drives and maintains AF (termed upstream therapies); however, much work is needed in this area. Here, we review current knowledge of AF mechanisms, therapies, and new areas of investigation.

Atrial Fibrillation as a Prognostic Indicator in Medium to Large-Sized Dogs with Myxomatous Mitral Valvular Degeneration and Congestive Heart Failure

Background

The prevalence and prognostic importance of atrial fibrillation (AF) on survival in nonsmall breed dogs with myxomatous mitral valvular disease (MMVD) and congestive heart failure (CHF) remain unknown.

Aim

To identify the prevalence of AF in nonsmall breed dogs with CHF because of MMVD and to characterize the impact of AF on survival outcome.

Animal

Sixty‐four client‐owned dogs (>15 kg) with MMVD and CHF.

Methods

Retrospective review of medical records for dogs weighing >15 kg with MMVD treated for CHF.

Results

Thirty‐three dogs presented with AF or developed AF during follow‐up examinations, and 31 dogs were free of AF until cardiac‐related death. For dogs with AF, median survival time (MST) was 142 days (range: 9–478) while dogs without AF lived 234 days (range: 13–879 days). AF increased risk of cardiac‐related death (HR = 2.544; 95% CI = 1.41–4.59; P = .0019) when compared to dogs without AF. MST was significantly prolonged for dogs with AF whose rates were adequately controlled (<160 bpm; 171 days; n = 13) when compared to dogs that failed to respond to negative chronotropic agents (61 days; n = 20; P = .032). The administration of combination treatment (diltiazem and digoxin) significantly decreased median HR to 144 bpm (range: 84–218 bpm) in dogs with AF and significantly prolonged MST (diltiazem+digoxin: 130 days versus diltiazem: 35 days, P = .0241) when compared to diltiazem alone.

Conclusions and Clinical Importance

Inadequately controlled AF is associated with a higher rate of mortality. Optimization of therapeutic strategies for the rate control of AF remains determined.

Making better scar: Emerging approaches for modifying mechanical and electrical properties following infarction and ablation

Following myocardial infarction (MI), damaged myocytes are replaced by collagenous scar tissue, which serves an important mechanical function - maintaining integrity of the heart wall against enormous mechanical forces - but also disrupts electrical function as structural and electrical remodeling in the infarct and borderzone predispose to re-entry and ventricular tachycardia. Novel emerging regenerative approaches aim to replace this scar tissue with viable myocytes. Yet an alternative strategy of therapeutically modifying selected scar properties may also prove important, and in some cases may offer similar benefits with lower risk or regulatory complexity. Here, we review potential goals for such modifications as well as recent proof-of-concept studies employing specific modifications, including gene therapy to locally increase conduction velocity or prolong the refractory period in and around the infarct scar, and modification of scar anisotropy to improve regional mechanics and pump function. Another advantage of scar modification techniques is that they have applications well beyond MI. In particular, ablation treats electrical abnormalities of the heart by intentionally generating scar to block aberrant conduction pathways. Yet in diseases such as atrial fibrillation (AF) where ablation can be extensive, treating the electrical disorder can significantly impair mechanical function. Creating smaller, denser scars that more effectively block conduction, and choosing the location of those lesions by balancing their electrical and mechanical impacts, could significantly improve outcomes for AF patients. We review some recent advances in this area, including the use of computational models to predict the mechanical effects of specific lesion sets and gene therapy for functional ablation. Overall, emerging techniques for modifying scar properties represents a potentially important set of tools for improving patient outcomes across a range of heart diseases, whether used in place of or as an adjunct to regenerative approaches.

Residual Risk of Stroke and Death in Anticoagulated Patients According to the Type of Atrial Fibrillation

Background and Purpose—

Atrial fibrillation (AF) and heart failure frequently coexist and are associated with increased morbidity and mortality. We investigated the prognosis of anticoagulated patients with permanent AF and nonpermanent AF according to preexisting heart failure in the AMADEUS (Evaluating the Use of SR34006 Compared to Warfarin or Acenocoumarol in Patients With Atrial Fibrillation) trial.

Methods—

The primary outcome was a composite of cardiovascular death and stroke or systemic embolism, analyzed using a Cox proportional hazards model, adjusted for baseline age, sex, diabetes mellitus, hypertension, creatinine, and previous cardiovascular diseases. The median follow-up was 11.6 months (interquartile range, 6.2–15.2).

Results—

Nonpermanent AF was present in 2072 patients (46% of cohort), of which 339 (16%) had preexisting heart failure. A total of 2484 patients had permanent AF (54% of cohort), with a higher burden of heart failure including 730 patients (29%; P <0.001). Overall, death because of cardiovascular causes occurred in 57 patients and 45 had stroke or systemic embolism (1.4/100 person-years for each). Overall, the adjusted incidence of the composite outcome was higher in patients with permanent AF than in patients with nonpermanent AF. In multivariate analysis, permanency of AF, creatinine, prior cerebrovascular events, and previous coronary disease were independently associated with the primary outcome. The hazard ratio for permanent versus nonpermanent AF was 1.68 (95% confidence interval, 1.08–2.55; P =0.02). The presence of heart failure increased the risk of adverse outcomes in a similar way in both permanent and nonpermanent AF (interaction P value=0.76).

Conclusions—

The risk of cardiovascular death, stroke, or systemic embolism is higher in anticoagulated patients with permanent AF than in those with nonpermanent AF, regardless of preexisting heart failure.

Natriuretic peptides for the detection of paroxysmal atrial fibrillation

Background and purpose

Silent atrial fibrillation (AF) and tachycardia (AT) are considered precursors of ischaemic stroke. Therefore, detection of paroxysmal atrial rhythm disorders is highly relevant, but is clinically challenging. We aimed to evaluate the diagnostic value of natriuretic peptide levels in the detection of paroxysmal AT/AF in a pilot study.

Methods

Natriuretic peptide levels were analysed in two independent patient cohorts (162 patients with arterial hypertension or other cardiovascular risk factors and 82 patients with retinal vessel disease). N-terminal-pro-brain natriuretic peptide (NT-proBNP) and BNP were measured before the start of a 7-day Holter monitoring period carefully screened for AT/AF.

Results

244 patients were included; 16 had paroxysmal AT/AF. After excluding patients with a history of AT/AF (n=5), 14 patients had newly diagnosed AT/AF (5.8%) NT-proBNP and BNP levels were higher in patients with paroxysmal AT/AF in both cohorts: (1) 154.4 (IQR 41.7; 303.6) versus 52.8 (30.4; 178.0) pg/mL and 70.0 (31.9; 142.4) versus 43.9 (16.3; 95.2) and (2) 216.9 (201.4; 277.1) versus 90.8 (42.3–141.7) and 96.0 (54.7; 108.2) versus 29.1 (12.0; 58.1). For the detection of AT/AF episodes, NT-proBNP and BNP had an area under the curve in receiver operating characteristic analysis of 0.76 (95% CI, 0.64 to 0.88; p=0.002) and 0.75 (0.61 to 0.89; p=0.004), respectively.

Conclusions

NT-proBNP and BNP levels are elevated in patients with silent AT/AF as compared with sinus rhythm. Thus, screening for undiagnosed paroxysmal AF using natriuretic peptide level initiated Holter monitoring may be a useful strategy in prevention of stroke or systemic embolism.

Five-Year Follow-Up After Catheter Ablation of Persistent Atrial Fibrillation Using the Stepwise Approach and Prognostic Factors for Success

Background—

In the meantime, catheter ablation is widely used for the treatment of persistent atrial fibrillation (AF). There is a paucity of data about long-term outcomes. This study evaluates (1) 5-year single and multiple procedure success and (2) prognostic factors for arrhythmia recurrences after catheter ablation of persistent AF using the stepwise approach aiming at AF termination.

Methods and Results—

A total of 549 patients with persistent AF underwent de novo catheter ablation using the stepwise approach (2007–2009). A total of 493 patients were included (Holter ECGs ≥every 6 months). Mean follow-up was 59±16 months with 2.1±1.1 procedures per patient. Single and multiple procedure success rates were 20.1% and 55.9%, respectively (80% off antiarrhythmic drug). Antiarrhythmic drug–free multiple procedure success was 46%. Long-term recurrences (n=171) were paroxysmal AF in 48 patients (28%) and persistent AF/atrial tachycardia in 123 patients (72%). Multivariable recurrent event analysis revealed the following factors favoring arrhythmia recurrence: failure to terminate AF during index procedure (hazard ratio [HR], 1.279; 95% confidence interval [CI], 1.093–1.497; P =0.002), number of procedures (HR, 1.154; 95% CI, 1.051–1.267; P =0.003), female sex (HR, 1.263; 95% CI, 1.027–1.553; P =0.027), and the presence of structural heart disease (HR, 1.236; 95% CI, 1.003–1.524; P =0.047). AF termination was correlated with a higher rate of consecutive procedures because of atrial tachycardia recurrences ( P =0.003; HR, 1.71; 95% CI, 1.20–2.43).

Conclusions—

Catheter ablation of persistent AF using the stepwise approach provides limited long-term freedom of arrhythmias often requiring multiple procedures. AF termination, the number of procedures, sex, and the presence of structural heart disease correlate with outcome success. AF termination is associated with consecutive atrial tachycardia procedures.