Lone atrial fibrillation - an overview

The Party Should Not Last That Long

Too much food, too much wine, and too many friends. You'll pay the price tomorrow; you shouldn't have let the party last so long. This analogy seems apt with respect to our new understanding of atrial fibrillation (AF) and approaches to AF. The keys to understanding recent advances in the management of AF and improving outcomes on therapies are an appreciation that: (1) AF is often a progressive disorder; (2) its progression is related to the degree of atrial myopathy that is present; (3) atrial myopathy is a consequence of the effects of underlying comorbidities as well as the effect of AF itself (tachycardic effects on the atria); (4) adverse outcomes can be a consequence of AF, the underlying atrial myopathy, as well as direct consequences of any comorbidities present; (5) rhythm control of AF early in its course as well as early and optimal treatment of underlying comorbidities have been associated with improved outcomes (eg, lower mortality, lesser thromboembolism, lesser heart failure, fewer hospitalizations) in recent trials; (6) therapies not available 2 decades ago during the rate- versus rhythm-control trials have played a role in the new treatment approaches and make the old idea that rate control is as good as rhythm control somewhat obsolescent; and (7) these now indicate that optimal and early rhythm control and comorbidity treatment provide the best results for AF patients.

Beyond the 2020 guidelines on atrial fibrillation of the European society of cardiology

The most recent atrial fibrillation (AF) guidelines delivered by European Society of Cardiology (ESC) offer an updated approach to AF management, with the perspective of improved characterization of the arrhythmia, the cardiac substrate and the patients profile in terms of associated risk factors and comorbidities. Recommendations were based on careful scrutiny and assessment of all available evidence with the final aim to offer to practitioners a lower level of uncertainty in the complex process of decision making for patients with AF. The 2020 ESC guidelines on AF propose a paradigm shift in the clinical approach to AF patients, moving from a single-domain AF classification to comprehensive characterization of AF patients. Given the complex nature of AF, an integrated holistic management of AF patients is suggested by the guidelines for improving patients outcomes through the formal introduction of the CC (Confirm AF and Characterize AF) to ABC (Atrial fibrillation Better Care) pathway. In line with this concept, these new guidelines underline the importance of a more comprehensive management of AF patients which should not be limited to simply prescribe oral anticoagulation or decide between a rhythm or rate control strategy. Indeed, each step of the ABC pathway represents one of the pivotal pillars in the management of AF and only a holistic approach has the potential to improve patients' outcomes. In this review we will discuss the background that supports some of the new recommendations of 2020 ESC guidelines, with important implications for daily management of AF patients.

Diagnostic Efficacy of Cardiac Scintigraphy with 99mTc-Pyrophosphate for Latent Myocardial Inflammation in Patients with Atrial Fibrillation

Objectives

This work aimed to study the efficacy of hybrid ^99mTc-Pyrophosphate SPECT/CT for diagnosis of latent inflammatory processes in the myocardium of patients with atrial fibrillation (AF).

Methods

The study comprised 34 patients aged 44 ± 9 years with AF of unknown etiology referred for radiofrequency ablation. The data were acquired using hybrid ^99mTc-Pyrophosphate SPECT/CT. To evaluate and interpret the results of hybrid study and to determine localization of radiopharmaceutical accumulation, scintigraphic and CT images were fused. SPECT/CT results were compared with data of endomyocardial biopsy.

Results

Sensitivity, specificity, and accuracy of ^99mTc-Pyrophosphate SPECT/CT in diagnosing myocarditis were 91%, 100%, and 94%, respectively. Proposed diagnostic criteria for myocarditis comprised intensity of the radiopharmaceutical accumulation in the myocardium and the ratios of focus/lung, focus/vertebral column, and focus/LV pool. Minimum cutoff values for the histologically verified myocarditis were >1.47 for focus/lung index, >0.11 for focus/vertebral column ratio, and >1.26 for focus/lung index.

Conclusions

SPECT/CT-based quantitative assessment of ^99mTc-Pyrophosphate accumulation in the myocardium is a highly informative noninvasive method for diagnosis of inflammatory process in the heart in patients with AF of undefined etiology.

Irish wolfhounds with subclinical atrial fibrillation: progression of disease and causes of death

INTRODUCTION

To evaluate the frequency of dilated cardiomyopathy (DCM) and cardiac death (CD) in Irish wolfhounds (IW) with subclinical atrial fibrillation (AF) and to compare cardiac and all-cause mortality to those of a contemporaneous control group of apparently healthy IW with sinus rhythm.

ANIMALS

Fifty-two IW with AF, but without echocardiographic evidence of DCM or other cardiac disease, and an age- and gender-matched control cohort of 52 apparently healthy IW.

METHODS

Data from 1552 IW were retrospectively evaluated. Fifty-two dogs with subclinical AF were compared with 52 IW controls. Time from initial diagnosis to development of DCM was recorded, and survival data were analyzed using cumulative incidence functions.

RESULTS

26/52 AF dogs developed DCM. At study end, in the AF and control group each, 49/52 AF dogs had died, three remained alive. Death in the AF cohort was attributed to CD in 22/49 dogs (12 congestive heart failure [CHF], 10 sudden cardiac deaths [SCD]), while 27 dogs died from non-CD. In the control group, significantly fewer dogs developed DCM (11/52 dogs, p=0.004), even fewer died from CD (5/49; three CHF, two SCD; p=0.001). The odd ratios (95% confidence interval) for dogs with AF vs. controls to develop DCM was 3.7 (1.6-8.8) and to die from CD was 7.2 (2.4-21.2). Median all-cause survival for AF IWs (CD, 36.3 months; non-CD, 33.2 months) did not differ significantly from the control group (CD, 28.6 months, p=0.377; non-CD, 45.3 months, p=0.631).

CONCLUSION

IW with subclinical AF commonly develop DCM and die from cardiac death.

Vaccination and risk of lone atrial fibrillation in the active component United States military

PURPOSE

To evaluate the hypothesis that receipt of anthrax vaccine adsorbed (AVA) increases the risk of atrial fibrillation in the absence of identifiable underlying risk factors or structural heart disease (lone atrial fibrillation).

METHODS

We conducted a retrospective population-based cohort study among U.S. military personnel who were on active duty during the period from January 1, 1998 through December 31, 2006. International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes were used to identify individuals diagnosed with atrial fibrillation in the Defense Medical Surveillance System, and electronic records were screened to include only individuals without evidence of predisposing medical conditions. We used multivariable Poisson regression to estimate the risk of lone atrial fibrillation after exposure to AVA. We also evaluated possible associations with influenza and smallpox vaccines.

RESULTS

Our study population consisted of 2,957,091individuals followed for 11,329,746 person-years of service. Of these, 2,435 met our case definition for lone atrial fibrillation, contributing approximately 8,383 person-years of service. 1,062,176 (36%) individuals received at least one dose of AVA; the median person time observed post-exposure was 3.6 years. We found no elevated risk of diagnosed lone atrial fibrillation associated with AVA (adjusted risk ratio = 0.99; 95% confidence interval = 0.90, 1.09; p = 0.84). No elevated risk was observed for lone atrial fibrillation associated with influenza or smallpox vaccines given during military service.

CONCLUSIONS

We did not find an increased risk of lone atrial fibrillation after AVA, influenza or smallpox vaccine. These findings may be helpful in planning future vaccine safety research.

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.

Hypertension and Atrial Fibrillation: An Intimate Association of Epidemiology, Pathophysiology, and Outcomes

Atrial fibrillation (AF) is the most prevalent sustained arrhythmia found in clinical practice. AF rarely exists as a single entity but rather as part of a diverse clinical spectrum of cardiovascular diseases, related to structural and electrical remodeling within the left atrium, leading to AF onset, perpetuation, and progression. Due to the high overall prevalence within the AF population arterial hypertension plays a significant role in the pathogenesis of AF and its complications. Fibroblast proliferation, apoptosis of cardiomyocytes, gap junction remodeling, accumulation of collagen both in atrial and ventricular myocardium all accompany ageing-related structural remodeling with impact on electrical activity. The presence of hypertension also stimulates oxidative stress, systemic inflammation, rennin-angiotensin-aldosterone and sympathetic activation, which further drives the remodeling process in AF. Importantly, both hypertension and AF independently increase the risk of cardiovascular and cerebrovascular events, e.g., stroke and myocardial infarction. Given that both AF and hypertension often present with limited on patient wellbeing, treatment may be delayed resulting in development of complications as the first clinical manifestation of the disease. Antithrombotic prevention in AF combined with strict blood pressure control is of primary importance, since stroke risk and bleeding risk are both greater with underlying hypertension.

Atrial fibrillation without comorbidities: Prevalence, incidence and prognosis (from the Framingham Heart Study)

BACKGROUND

The epidemiology of atrial fibrillation (AF) without comorbidities, known as 'lone AF', is uncertain. Although it has been considered a benign condition, we hypothesized that it confers a worse prognosis compared with a matched sample without AF.

METHODS

We described the proportion of AF without comorbidities (clinical, subclinical cardiovascular disease and triggers) among the entire AF sample in Framingham Heart Study (FHS). We compared AF without comorbidities with typical AF, and age-, sex- and cohort-matched individuals without AF, using Cox proportional hazards analysis in relation to combined cardiovascular events (stroke, heart failure, myocardial infarction), and mortality.

RESULTS

Of 10,311 FHS participants, 1,961 were diagnosed with incident AF, among which 173 individuals had AF without comorbidities (47% women, mean age 71±12 years). AF without comorbidities had a prevalence of 1.7% of the entire cohort, and an annual incidence of 0.5 per 1000 person-years. During a median follow-up of 9.7 years after initial AF, 137 individuals with AF without comorbidities (79.2%) died and 141 individuals developed cardiovascular events (81.5%). AF without comorbidities had significantly lower mortality (HR 0.67, 95%CI 0.55-0.81, P < .001) and total cardiovascular events (HR 0.66, 95% CI 0.55-0.80, P < .001) compared with typical AF. However, mortality (HR1.43, 95% CI 1.18-1.75, P < .001) and risk of total cardiovascular events (HR 1.73, 95% CI 1.39-2.16, P < .001) were higher than age-, sex-, and cohort-matched individuals without AF.

CONCLUSIONS

The risk of cardiovascular outcomes and mortality among individuals with AF without comorbidities is lower than typical AF, but is significantly elevated compared with matched individuals without AF.

Relation of Biomarkers of Inflammation and Oxidative Stress with Hypertension Occurrence in Lone Atrial Fibrillation

We compared plasma levels of biomarkers of inflammation (CRP) and oxidation (oxLDL), determined at study inclusion in lone atrial fibrillation (LAF) patients (48.6 ± 11.5 years; 74.0% men) and sinus rhythm controls (49.7 ± 9.3 years; 72.7% men, P > 0.05), and investigated the association of baseline CRP and oxLDL levels with the risk for vascular disease (VD) development (hypertension, cerebrovascular disease, coronary/peripheral artery disease, and pulmonary embolism) during prospective follow-up. Baseline CRP (1.2 [0.7–1.9] mg/L versus 1.1 [0.7–1.6] mg/L) and oxLDL levels (66.3 ± 21.2 U/L versus 57.1 ± 14.6 U/L) were higher in LAF patients (both P < 0.05). Following a median of 36 months, incident VD occurred in 14 (28.0%) LAF patients, all of whom developed arterial hypertension, and in 5 (11.4%) controls (hypertension, n = 4; coronary artery disease, n = 1), P < 0.05. LAF patients developed VD more frequently and at a younger age. Both CRP (HR, 2.54; 95% CI, 1.26–5.12; P = 0.009) and oxLDL (HR, 2.24; 95% CI, 1.14–4.40; P = 0.019) were multivariate predictors of incident hypertension in LAF patients, but not in the controls. Further research should clarify clinical relevance of investigated biomarkers for risk stratification and treatment of LAF patients.