Obesity and atrial fibrillation

Apixaban plasma concentrations in patients with obesity

PURPOSE

Routine therapeutic drug monitoring of apixaban is currently not recommended but may however be warranted in some situations and for some patient groups to provide better and safer treatment. Due to limited data on apixaban concentrations in different subpopulations, it is still unclear which group of patients could possibly gain from monitoring. The purpose of this study was to examine apixaban exposure in patients with obesity compared with normal-weight patients.

METHODS

Forty patients with obesity (mean BMI 39.4 kg/m2) and 40 controls with normal weight (mean BMI 23.4 kg/m2), treated with apixaban 5 mg twice daily were included. The patients were matched for age, sex, and renal function. Trough and peak apixaban concentrations were measured with LC‒MS/MS methodology.

RESULTS

The median trough concentrations in patients with obesity (58.7, range 10.7-200.7 ng/ml) were slightly higher than those in patients with normal weight (52.0, range 31.0-150.9 ng/ml) (p < 0.05). Notably, the variability in trough concentration was considerably higher in patients with obesity. Peak concentrations were similar in both groups, with a median of 124.5 ng/ml (range 82.0-277.5) and 113.5 ng/ml (range 75.5-334.6) in patients with obesity and normal weight, respectively.

CONCLUSION

Apixaban exposure did not vary substantially between obese and normal weight matched controls, implying that general dose adjustments are not required. However, vast interindividual variability was observed in patients with obesity, suggesting that measuring the concentrations could be valuable for specific patients. Further research is needed to identify which specific patients may benefit from this approach.

Burden of cardiometabolic disorders and lifetime risk of new-onset atrial fibrillation among men and women: the Rotterdam Study

AIMS

To examine the association between the burden of cardiometabolic disorders with new-onset atrial fibrillation (AF) and lifetime risk of AF incidence among men and women.

METHODS AND RESULTS

Four thousand one hundred and one men and 5421 women free of AF at baseline (1996-2008) from the population-based Rotterdam Study were included. Sex-specific Cox proportional-hazards regression models were used to assess the association between the burden of cardiometabolic disorders and risk of new-onset AF. The remaining lifetime risk for AF was estimated at index ages of 55, 65, and 75 years up to age 108. Mean age at baseline was 65.5 ± 9.4 years. Median follow-up time was 12.8 years. In the fully adjusted model, a stronger association was found between a larger burden of cardiometabolic disorders and incident AF among women [hazard ratio (HR): 1.33% and 95% conference interval (CI): 1.22-1.46], compared to men [1.18 (1.08-1.29)] (P for sex-interaction <0.05). The lifetime risk for AF significantly increased with the number of cardiometabolic disorders among both sexes. At an index age of 55 years, the lifetime risks (95% CIs) for AF were 27.1% (20.8-33.4), 26.5% (22.8-30.5), 29.9% (26.7-33.2), 30.8% (25.7-35.8), and 33.3% (23.1-43.6) among men, for 0, 1, 2, 3, and ≥4 comorbid cardiometabolic disorders. Corresponding risks were 15.8% (10.5-21.2), 23.0% (19.8-26.2), 29.7% (26.8-32.6), 26.2% (20.8-31.6), and 34.2% (17.3-51.1) among women.

CONCLUSION

We observed a significant combined impact of cardiometabolic disorders on AF risk, in particular among women. Participants with cardiometabolic multimorbidity had a significantly higher lifetime risk of AF, especially at a young index age.

Enablers and Hindrances of Lifestyle Changes Among Patients With Atrial Fibrillation: A Qualitative Study

BACKGROUND

Atrial fibrillation (AF) seriously affects the health status and quality of life of affected patients. However, the lifestyle changes recommended by the guidelines for patients are not ideal. Hence, understanding the factors that promote and hinder healthy behavior changes in patients with AF is crucial for self-management.

OBJECTIVE

The aims of this study were to understand the factors enabling and hindering health behaviors in patients with AF and to provide a reference for promoting health management among these patients.

METHODS

Using the purposive sampling method, 22 patients with AF admitted to the Cardiac Center of Beijing Chaoyang Hospital, Capital Medical University, from March 2021 to June 2021 were selected for in-depth face-to-face interviews. The thematic analysis method was used to summarize and refine the themes.

RESULTS

The following 2 themes and 15 subthemes were eventually extracted by analyzing and summarizing the interview data. The 7 factors facilitating health behaviors in patients with AF were risk perception, outcome expectancy, behavioral intention, action plan, response plan, self-efficacy, and social support. There were 8 hindering factors: personal preferences and habits, specific customary culture, weak self-control, accessibility of exercise conditions, symptom-related distress, cognitive weakness, multiple medication use, and insufficient awareness of condition monitoring.

CONCLUSIONS

The factors affecting health behaviors in patients with AF are complex, and healthcare providers should reinforce the facilitators of health behaviors in these patients and provide them with targeted interventions against hindering factors. Results can be used to develop health behavior intervention programs for patients with AF.

Impact of Obesity on Atrial Electrophysiological Substrate

(1) Background. Obesity is a well-established worldwide recognised risk factor for atrial fibrillation (AF). Prior review papers reported on the associations between obesity and AF development, but not on the relation between obesity and atrial electrophysiology. We therefore conducted a systematic review to describe the current knowledge of the characteristics of the atrial electrophysiological substrate in obese individuals and how they relate to the development of AF. (2) Methods. A search was conducted in Pubmed, Embase, and the Cochrane Library for publications evaluating the impact of obesity on atrial electrophysiology, electrical substrates, and their relation to the development of AF. (3) Results. A systematic literature search retrieved 477 potential publications based on the inclusion criteria; 76 full-text articles were selected for the present systematic review. The literature demonstrated that obesity predisposes to not only a higher AF incidence but also to more extensive atrial electrophysiological abnormalities increasing susceptibility to AF development. (4) Conclusion. Obesity may predispose to an overall increase in atrial electropathology, consisting of an increase in the slowing of the conduction, conduction block, low-voltage areas, and complex fractionated electrograms. To determine the impact of obesity-induced atrial electrical abnormalities on the long-term clinical outcome, further prospective studies are mandatory.

mTOR Modulation of IKr through hERG1b-Dependent Mechanisms in Lipotoxic Heart

In the atria, the rapid delayed rectifier channel (IKr) is a critical contributor to repolarization. In lipotoxic atria, increased activity of the serine/threonine mammalian target of rapamycin (mTOR) may remodel IKr and predispose patients to arrhythmias. To investigate whether mTOR produced defects in IKr channel function (protein expression and gating mechanisms), electrophysiology and biochemical assays in HEK293 cells stably expressing hERG1a/1b, and adult guinea pig atrial myocytes were used. Feeding with the saturated fatty acid palmitic acid high-fat diet (HFD) was used to induce lipotoxicity. Lipotoxicity-challenged HEK293 cells displayed an increased density of hERG1a/1b currents due to a targeted and significant increase in hERG1b protein expression. Furthermore, lipotoxicity significantly slowed the hERG1a/1b inactivation kinetics, while the activation and deactivation remained essentially unchanged. mTOR complex 1 (mTORC1) inhibition with rapamycin (RAP) reversed the increase in hERG1a/1b density and inactivation. Compared to lipotoxic myocytes, RAP-treated cells displayed action potential durations (APDs) and IKr densities similar to those of controls. HFD feeding triggered arrhythmogenic changes (increased the IKr density and shortened the APD) in the atria, but this was not observed in low-fat-fed controls. The data are the first to show the modulation of IKr by mTORC1, possibly through the remodeling of hERG1b, in lipotoxic atrial myocytes. These results offer mechanistic insights with implications for targeted therapeutic options for the therapy of acquired supraventricular arrhythmias in obesity and associated pathologies.

The Atrium in Atrial Fibrillation - A Clinical Review on How to Manage Atrial Fibrotic Substrates

Atrial fibrillation (AF) is the most common sustained arrhythmia in the population and is associated with a significant clinical and economic burden. Rigorous assessment of the presence and degree of an atrial arrhythmic substrate is essential for determining treatment options, predicting long-term success after catheter ablation, and as a substrate critical in the pathophysiology of atrial thrombogenesis. Catheter ablation of AF has developed into an essential rhythm-control strategy. Nowadays is one of the most common cardiac ablation procedures performed worldwide, with its success inversely related to the extent of atrial structural disease. Although atrial substrate evaluation remains complex, several diagnostic resources allow for a more comprehensive assessment and quantification of the extent of left atrial structural remodeling and the presence of atrial fibrosis. In this review, we summarize the current knowledge on the pathophysiology, etiology, and electrophysiological aspects of atrial substrates promoting the development of AF. We also describe the risk factors for its development and how to diagnose its presence using imaging, electrocardiograms, and electroanatomic voltage mapping. Finally, we discuss recent data regarding fibrosis biomarkers that could help diagnose atrial fibrotic substrates.

Updates on epicardial adipose tissue mechanisms on atrial fibrillation

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

Impact of body mass index on left atrial dimension in HOCM patients

Background

Substantial studies have demonstrated that left atrial (LA) enlargement was a robust predictor of atrial fibrillation (AF) and obesity was a modifiable risk factor for cardiovascular diseases. However, the role of body mass index (BMI) on LA dimension in hypertrophic obstructive cardiomyopathy (HOCM) remains unclear.

Methods

A total of 423 HOCM patients (average BMI 25.4 ± 3.4 kg/m²) were recruited for our study. Participants were stratified into three groups based on BMI: normal weight (BMI < 23 kg/m²), overweight (BMI 23–27.5 kg/m²), and obesity (BMI ≥ 27.5 kg/m²).

Results

Compared with normal weight, patients with obesity had significantly lower prevalence of syncope (p = 0.007) and moderate or severe mitral regurgitation (p = 0.014), and serum NT-proBNP (p = 0.004). Multiple linear regression analysis indicated that BMI (β = 0.328, p < 0.001), log NT-proBNP (β = 0.308, p < 0.001), presence of AF (β = 0.209, p = 0.001), and left ventricular diastolic diameter index (β = 0.142, p = 0.019) were independently related with LA diameter. However, BMI was not an independent predictor of the presence of AF on multivariable binary logistical regression analysis.

Conclusions

BMI was independently associated with LA diameter; however, it was not an independent predictor of prevalence of AF. These results suggest that BMI may promote incidence of AF through LA enlargement in HOCM.

Role of epicardial adipose tissue in the development of atrial fibrillation in hypertensive patients

Obesity is a progressing epidemic, the prevalence of which has doubled over the past 30 years. The distribution of adipose tissue is an important factor in predicting the risk of cardiovascular events. The most significant inflammatory activity is characteristic of epicardial adipose tissue (EAT), the role of which in the development of atrial fibrillation (AF) remains a subject of discussion.

Aim. To study the effect of EAT size on the development of AF in hypertensive (HTN) patients.

Material and methods. The study included 95 patients with HTN aged 38-72 years (mean age, 61,5±1,8 years), including 45 patients with paroxysmal AF (group I) and 50 patients in the comparison group (group II). In order to assess the severity of visceral obesity, all patients underwent a general examination and echocardiography. To determine the EAT volume, cardiac multislice computed tomography was performed.

Results. Echocardiography revealed that the EAT thickness was significantly greater in hypertensive patients with paroxysmal AF than in the comparison group: 11,6±0,8 and 8,6±0,4 mm, respectively (p<0,001). According to cardiac multislice computed tomography, a significant increase in EAT volume was revealed in patients of group I (4,6±0,4 ml) compared with group II (3,5±0,25 ml) (p=0,019). In hypertensive patients with paroxysmal AF, a positive moderate relationship between the EAT volume and left atrial volume was revealed (r=0,7, p=0,022). Multivariate analysis showed that in hypertensive patients, EAT thickness >10 mm and volume >6 ml can serve as integral markers of the onset of paroxysmal AF.

Conclusion. Integral markers of AF in hypertensive patients are an increase in the EAT thickness >10 mm (odds ratio, 4,1; 95% confidence interval, 1,1-5,6) and volume >6 ml (odds ratio 3,7; 95%, confidence interval 1,0-4,2).

Non-coding RNAs and Atrial Fibrillation

Atrial fibrillation is the most frequent type of cardiac arrhythmia in humans, with an estimate incidence of 1-2% in the general population, rising up to 8-10% in the elderly. Cardiovascular risk factors such as diabetes, obesity, hypertension and hyperthyroidism can increase the occurrence of AF. The onset of AF triggers additional AF episodes, leading to structural and electrical remodeling of the diseased heart. Understanding the molecular bases of atrial fibrillation have greatly advance over the last decade demonstrating a pivotal role of distinct ion channels in AF pathophysiology. A new scenario has opened on the understanding of the molecular mechanisms underlying AF, with the discovery of non-coding RNAs and their wide implication in multiple disease states, including cardiac arrhythmogenic pathologies. microRNAs are small non-coding RNAs of 22-24 nucleotides that are capable of regulating gene expression by interacting with the mRNA transcript 3'UTRs and promoting mRNA degradation and/or protein translation blockage. Long non-coding RNAs are a more diverse group of non-coding RNAs, providing transcriptional and post-transcriptional roles and subclassified according to their functional properties. In this chapter we summarized current state-of-the-art knowledge on the functional of microRNAs and long non-coding RNAs as well as their cross-talk regulatory mechanisms in atrial fibrillation.

Effect of fish oil on circulating asymmetric dimethylarginine and adiponectin in overweight or obese patients with atrial fibrillation

Obesity and adipose-derived peptides might be involved in the pathogenesis of atrial fibrillation (AF). Adiponectin plays a major role in the modulation of several metabolic pathways, and asymmetric dimethylarginine (ADMA) has been suggested to be predictive of AF and associated adverse events. The aim of this study was to investigate the effect of fish oil supplementation on circulating adiponectin and ADMA in overweight or obese patients with persistent AF. In this randomized, double-blind, placebo-controlled trial, 80 overweight or obese (body mass index (BMI) ≥ 25 kg/m2) patients with persistent AF were randomly assigned to two groups to receive either 2 g/day fish oil or placebo, for 8 weeks. Serum levels of adiponectin and ADMA, and anthropometric indexes were measured. This study showed that serum adiponectin concentrations increased significantly following fish oil supplementation compared with the placebo group (13.15 ± 7.33 vs. 11.88 ± 6.94 µg/ml; p = .026). A significant reduction was also observed in serum ADMA levels in the fish oil compared with the placebo group following the intervention (0.6 ± 0.13 vs. 0.72 ± 0.15 µmol/L; p = .001). The changes in serum adiponectin and ADMA concentrations remained significant after adjustments for baseline values, age, sex, and changes of BMI and waist circumference (p = .011 and p = .001, respectively). In conclusion,  8 weeks supplementation with fish oil increased serum adiponectin and decreased ADMA concentrations in overweight or obese patients with persistent AF. As adiponectin and ADMA are suggested to be involved in many pathways associated with AF, the current findings might be promising in the clinical management of this disease, an issue that needs further investigations.

Effects of body mass index on the safety and effectiveness of direct oral anticoagulants: a retrospective review

BACKGROUND

The International Society on Thrombosis and Haemostasis recommends avoiding the use of direct oral anticoagulants (DOACs) in patients with a body mass index (BMI) greater than 40 kg/m² or weight greater than 120 kg.

HYPOTHESIS

Higher BMI is associated with altered pharmacokinetics which may affect the safety and effectiveness for DOACs.

METHODS

Data were collected on 3458 patients taking a DOAC prior to admission to a Midwestern health system between February 2013 and August 2016. Of these, 43 patients had a thrombotic event and 70 patients had an overt bleeding event. Patients were stratified among the following three BMI groups: BMI < 30 kg/m², BMI 30-40 kg/m², and BMI > 40 kg/m².

RESULTS

There was no statistically significant difference between BMI groups for thrombotic events (p = 0.598) or for overt bleeding events (p = 0.065). The BMI < 30 kg/m² had the highest occurrence rate of bleeding events. It was observed that bleeding occurrence decreased as the BMI groups increased. The BMI > 40 kg/m² group had the lowest risk of bleeding events, and was the only group to have a higher occurrence rate of thrombotic events compared to bleeding events.

CONCLUSIONS

Among patients admitted to a single health system on DOAC therapy over a three-and-a-half-year period, obesity did not significantly correlate with thrombotic or overt bleeding complications. This study is limited as a single health system study with low overall event rates. A preliminary finding of this study showed a trend towards decreased bleeding frequency as BMI increased.

Murine model of left ventricular diastolic dysfunction and electro-mechanical uncoupling following high-fat diet

BACKGROUND/OBJECTIVES

It is well established that obesity is an independent risk factor for cardiac death. In particular various cardiac alterations have been described in obese patients such as long QT on ECG, impaired diastolic filling of the left ventricle (LV), and all-type arrhythmias. In the present study, the above alterations were all reproduced in a mouse model of fat diet-induced obesity.

ANIMALS/METHODS

In C57BL6 mice fed on a high fat (n = 20, HF-group) or standard diet (n = 20, C-group) for 13 weeks, balanced by sex and age, we examined heart morphology and function by high-frequency ultrasounds and electric activity by surface ECG. Besides, the autonomic sympathovagal balance (heart-rate variability) and the arrhythmogenic susceptibility to adrenergic challenge (i.p. isoproterenol) were compared in the two groups, as well as glucose tolerance (i.p. glucose test) and liver steatosis (ultrasounds).

RESULTS

Body weight in HF-group exceeded C-group at the end of the experiment (+28% p < 0.01). An abnormal ventricular repolarization (long QTc on ECG) together with impaired LV filling rate and increased LV mass was found in HF-group as compared to C. Moreover, HF-group showed higher heart rate, unbalanced autonomic control with adrenergic prevalence and a greater susceptibility to develop rhythm disturbances under adrenergic challenge (i.p. isoprenaline). Impaired glucose tolerance and higher liver fat accumulation were also found in HF mice compared to C.

CONCLUSIONS

The described murine model of 13 weeks on HF diet, well reproduced the cardiovascular and metabolic disorders reported in clinical obesity, suggesting its potential utility as translational mean suitable for testing new pharmaco-therapeutic approaches to the treatment of obesity and its comorbidity.

Differential Modulation of IK and ICa,L Channels in High-Fat Diet-Induced Obese Guinea Pig Atria

Obesity mechanisms that make atrial tissue vulnerable to arrhythmia are poorly understood. Voltage-dependent potassium (I_K, I_Kur, and I_K1) and L-type calcium currents (I_Ca,L) are electrically relevant and represent key substrates for modulation in obesity. We investigated whether electrical remodeling produced by high-fat diet (HFD) alone or in concert with acute atrial stimulation were different. Electrophysiology was used to assess atrial electrical function after short-term HFD-feeding in guinea pigs. HFD atria displayed spontaneous beats, increased I_K (I_Kr + I_Ks) and decreased I_Ca,L densities. Only with pacing did a reduction in I_Kur and increased I_K1 phenotype emerge, leading to a further shortening of action potential duration. Computer modeling studies further indicate that the measured changes in potassium and calcium current densities contribute prominently to shortened atrial action potential duration in human heart. Our data are the first to show that multiple mechanisms (shortened action potential duration, early afterdepolarizations and increased incidence of spontaneous beats) may underlie initiation of supraventricular arrhythmias in obese guinea pig hearts. These results offer different mechanistic insights with implications for obese patients harboring supraventricular arrhythmias.

Structural Equation Model (SEM) of Stroke Mortality in Spanish Inpatient Hospital Settings: The Role of Individual and Contextual Factors

Introduction: Traditionally, predictive models of in-hospital mortality in ischemic stroke have focused on individual patient variables, to the neglect of in-hospital contextual variables. In addition, frequently used scores are betters predictors of risk of sequelae than mortality, and, to date, the use of structural equations in elaborating such measures has only been anecdotal. Aims: The aim of this paper was to analyze the joint predictive weight of the following: (1) individual factors (age, gender, obesity, and epilepsy) on the mediating factors (arrhythmias, dyslipidemia, hypertension), and ultimately death (exitus); (2) contextual in-hospital factors (year and existence of a stroke unit) on the mediating factors (number of diagnoses, procedures and length of stay, and re-admission), as determinants of death; and (3) certain factors in predicting others. Material and Methods: Retrospective cohort study through observational analysis of all hospital stays of Diagnosis Related Group (DRG) 14, non-lysed ischemic stroke, during the time period 2008-2012. The sample consisted of a total of 186,245 hospital stays, taken from the Minimum Basic Data Set (MBDS) upon discharge from Spanish hospitals. MANOVAs were carried out to establish the linear effect of certain variables on others. These formed the basis for building the Structural Equation Model (SEM), with the corresponding parameters and restrictive indicators. Results: A consistent model of causal predictive relationships between the postulated variables was obtained. One of the most interesting effects was the predictive value of contextual variables on individual variables, especially the indirect effect of the existence of stroke units on reducing number of procedures, readmission and in-hospital mortality. Conclusion: Contextual variables, and specifically the availability of stroke units, made a positive impact on individual variables that affect prognosis and mortality in ischemic stroke. Moreover, it is feasible to determine this impact through the use of structural equation methodology. We analyze the methodological and clinical implications of this type of study for hospital policies.

Influence of Body Mass Index on Recurrence of Ventricular Arrhythmia, Mortality in Defibrillator Recipients With Ischaemic Cardiomyopathy

BACKGROUND

Obesity is associated with increased risk of cardiovascular disease. There is little known, however, about the influence of body mass index (BMI) on spontaneously occurring ventricular arrhythmias in patients with ischaemic heart disease. We sought to examine the effect of BMI on the ventricular arrhythmia (VA) recurrence and mortality in defibrillator recipients with ischaemic cardiomyopathy.

METHODS

Consecutive patients (n = 123) with ischaemic cardiomyopathy (left ventricular ejection fraction (LVEF) ≤ 40%) and a primary or secondary prevention defibrillator were included. Patients were classified according to their BMI as being normal (18.5-24.99, n = 54/ 43.9%), overweight (2 -29.99, n = 43/ 35%) or obese (>30, n = 26/20.3%).

RESULTS

The primary combined endpoint of VA recurrence and mortality occurred in 36%, 5.4% and 11.5% of patients with normal, overweight and obese BMI (p = 0.001). When adjusting for risk factors such as ejection fraction, age and triple vessel disease, on multivariable analysis, normal BMI remained a significant predictor for the primary outcome (Hazard Ratio, Normal vs Overweight = 7.1, 95% CI 1.8-25, p = 0.002: Hazard Ratio, Normal vs Obese = 5.5, 95% CI 1.11-25, p = 0.033). There was a non-significant trend towards reduced survival in patients with normal weight in comparison to overweight and obese patients (p = 0.08).

CONCLUSION

In defibrillator recipients with ischaemic cardiomyopathy, BMI appears to be a significant predictor for the combined primary outcome of spontaneously occurring ventricular arrhythmias and mortality. Normal BMI, compared to overweight and obese patients had worse outcomes, suggesting the presence of the obesity paradox in ventricular arrhythmogenesis late post infarction.

Genetics of Atrial Fibrilation: In Search of Novel Therapeutic Targets

Atrial fibrillation (AF) is the most frequent arrhythmogenic disease in humans, ranging from 2% in the general population and rising up to 10-12% in 80+ years. Genetic analyses of AF familiar cases have identified a series of point mutations in distinct ion channels, supporting a causative link. However, these genetic defects only explain a minority of AF patients. Genomewide association studies identified single nucleotide polymorphisms (SNPs), close to PITX2 on 4q25 chromosome, that are highly associated to AF. Subsequent GWAS studies have identified several new loci, involving additional transcription and growth factors. Furthermore, these risk 4q25 SNPs serve as surrogate biomarkers to identify AF recurrence in distinct surgical and pharmacological interventions. Experimental studies have demonstrated an intricate signalling pathway supporting a key role of the homeobox transcription factor PITX2 as a transcriptional regulator. Furthermore, cardiovascular risk factors such as hyperthyroidism, hypertension and redox homeostasis have been identified to modulate PITX2 driven gene regulatory networks. We provide herein a state-of-the-art review of the genetic bases of atrial fibrillation, our current understanding of the genetic regulatory networks involved in AF and its plausible usage for searching novel therapeutic targets.

A review and critique of published real-world weight management program studies

BACKGROUND

Beyond the essential but somewhat artificial conditions that typify formal clinical studies, real-world evidence (RWE) of weight loss program effectiveness is paramount for an accurate assessment of such programs and refinement of best practices.

OBJECTIVES

To evaluate the current state of RWE studies and publications on weight loss, identify the range of weight loss components being used in RWE programs, and to provide a general overview of the consistency or lack of consistency with regard to measuring and reporting outcomes.

METHODS

A structured search of PubMed was performed to identify relevant English-language publications from 2006 to December 2017 that reported real-world studies of weight loss among adults. Duplicates, non-relevant publications, articles on weight loss surgery, pediatric studies, randomized controlled trials, studies with self-reported weight loss, no objective weight measures, or that failed to include weight loss results were excluded.

RESULTS

This review included 62 RWE publications. Forty-nine studies included dietary intervention, 37 included exercise, 29 included motivational counseling, and 5 contained some patients who had pharmacologic treatment as part of their weight loss regimen. The numbers of participants per study ranged from 10 to more than 3 million. The interventions reported in the publications included diet, exercise, counseling to promote diet and/or exercise, motivational counseling, and pharmacotherapy, and various combinations of these.

CONCLUSIONS

Despite general acceptance that weight loss programs are capable of facilitating successful outcomes, this review revealed substantial inconsistency in the design and reporting of such programs, making it very difficult to draw conclusions about the comparative merits of different real-world weight loss strategies/components. In addition, there was a marked lack of congruence with current weight loss management guidelines, and notably few studies incorporating anti-obesity medications. There clearly is a need for greater rigor and standardization among designing and reporting RWE weight-loss studies.

Compliance in weight control reduces atrial fibrillation worsening: A retrospective cohort study

BACKGROUND AND AIM

Obesity plays a dominant role in the etiology of atrial fibrillation (AF), and the maintenance of a normal body mass index (BMI) seems to prevent and even reduce the incidence of the arrhythmia's recurrence. We selected 270 patients (pts) to assess whether this therapeutic effect was statistically significant even in Mediterranean patients.

METHOD AND RESULTS

In this retrospective cohort study, we analyzed every symptomatic AF relapse during a total follow-up of 657 patient-years. Clinical data, BMI variations, and pts' history were available in our clinical database. We divided the pts in four groups (Gs), according to their BMI variation during the follow-up: G1, normal weight pts, maintaining their weight; G2, overweight pts, losing weight; G3, overweight pts, maintaining their weight; G4, pts gaining weight. Their follow-up (in months) was normalized according to their AF relapses, thus obtaining a mean AF-free period for each patient. Among the overweight groups, G2 showed the best AF-free period (9.7 months). However, G3 and G4 showed a reduced AF-free interval (4.6 and 1.7 months, respectively). G1, predictably, had the longest AF-free period (10 months).

CONCLUSION

The results of the present study confirm that simple non-invasive intervention aimed to normalize BMI and to control risk factors through appropriate lifestyle can be highly effective in reducing the AF burden, by acting on comorbidities and proarrhythmic mechanisms. Therefore, serious attempt should be made to correct risk factors before an ablation therapy is proposed.

Cardiac Ion Channel Regulation in Obesity and the Metabolic Syndrome: Relevance to Long QT Syndrome and Atrial Fibrillation

Obesity and its associated metabolic dysregulation leading to metabolic syndrome is an epidemic that poses a significant public health problem. More than one-third of the world population is overweight or obese leading to enhanced risk of cardiovascular disease (CVD) incidence and mortality. Obesity predisposes to atrial fibrillation, ventricular, and supraventricular arrhythmias; conditions that are underlain by dysfunction in electrical activity of the heart. To date, current therapeutic options for cardiomyopathy of obesity are limited, suggesting that there is considerable room for development of therapeutic interventions with novel mechanisms of action that will help normalize rhythm in obese patients. Emerging candidates for modulation by obesity are cardiac ion channels and Ca handling proteins. However, the underlying molecular mechanisms of the impact of obesity on these channels/Ca handling proteins remain incompletely understood. Obesity is marked by accumulation of adipose tissue associated with a variety of adverse adaptations including dyslipidemia (or abnormal levels of serum free fatty acids), increased secretion of pro-inflammatory cytokines, fibrosis, hyperglycemia, and insulin resistance, that will cause electrical remodeling and thus predispose to arrhythmias. Further, adipose tissue is also associated with the accumulation of subcutaneous and visceral fat, which are marked by distinct signaling mechanisms. Thus, there may also be functional differences in the outcome of regional distribution of fat deposits on ion channel/Ca handling proteins expression. Evaluating alterations in their functional expression in obesity will lead to progress in the knowledge about the mechanisms responsible for obesity-related arrhythmias. These advances are likely to reveal new targets for pharmacological modulation. The objective of this article is to review cardiac ion channel/Ca handling proteins remodeling that predispose to arrhythmias. Understanding how obesity and related mechanisms lead to cardiac electrical remodeling is likely to have a significant medical and economic impact.

The associations of leptin, adiponectin and resistin with incident atrial fibrillation in women

OBJECTIVES

Higher body mass index (BMI) is an important risk factor for atrial fibrillation (AF). The adipokines leptin, adiponectin and resistin are correlates of BMI, but their association with incident AF is not well known. We explored this relationship in a large cohort of postmenopausal women.

METHODS

We studied an ethnically diverse cohort of community-dwelling postmenopausal women aged 50-79 who were nationally recruited at 40 clinical centres as part of the Women's Health Initiative investigation. Participants underwent measurements of baseline serum leptin, adiponectin and resistin levels and were followed for incident AF. Adipokine levels were log transformed and normalised using inverse probability weighting. Cox proportional hazard regression models were used to estimate associations with adjustment for known AF risk factors.

RESULTS

Of the 4937 participants included, 892 developed AF over a follow-up of 11.1 years. Those with AF had higher mean leptin (14.9 pg/mL vs 13.9 pg/mL), adiponectin (26.3 ug/mL vs 24.5 ug/mL) and resistin (12.9 ng/mL vs 12.1 ng/mL) levels. After multivariable adjustment, neither log leptin nor log adiponectin levels were significantly associated with incident AF. However, log resistin levels remained significantly associated with incident AF (HR=1.57 per 1 log (ng/mL) increase, p=0.006). Additional adjustment for inflammatory cytokines only partially attenuated the association between resistin and incident AF (HR=1.43, p=0.06 adjusting for C-reactive protein (CRP); HR=1.39, p=0.08 adjusting for IL-6). Adjusting for resistin partially attenuated the association between BMI and incident AF (HR=1.14 per 5 kg/m(2), p=0.006 without resistin; HR=1.12, p=0.02 with resistin).

CONCLUSIONS

In women, elevated levels of serum resistin are significantly associated with higher rates of incident AF and partially mediate the association between BMI and AF. In the same population, leptin and adiponectin levels are not significantly associated with AF.

High-fat diet-dependent modulation of the delayed rectifier K(+) current in adult guinea pig atrial myocytes

Obesity is associated with hyperlipidemia, electrical remodeling of the heart, and increased risk of supraventricular arrhythmias in both male and female patients. The delayed rectifier K(+) current (IK), is an important regulator of atrial repolarization. There is a paucity of studies on the functional role of IK in response to obesity. Here, we assessed the obesity-mediated functional modulation of IK in low-fat diet (LFD), and high-fat diet (HFD) fed adult guinea pigs. Guinea pigs were randomly divided into control and obese groups fed, ad libitum, with a LFD (10 kcal% fat) or a HFD (45 kcal% fat) respectively. Action potential duration (APD), and IK were studied in atrial myocytes and IKr and IKs in HEK293 cells using whole-cell patch clamp electrophysiology. HFD guinea pigs displayed a significant increase in body weight, total cholesterol and total triglycerides within 50 days. Atrial APD at 30% (APD30) and 90% (APD90) repolarization were shorter, while atrial IK density was significantly increased in HFD guinea pigs. Exposure to palmitic acid (PA) increased heterologously expressed IKr and IKs densities, while oleic acid (OA), severely reduced IKr and had no effect on IKs. The data are first to show that in obese guinea pigs abbreviated APD is due to increased IK density likely through elevations of PA. Our findings may have crucial implications for targeted treatment options for obesity-related arrhythmias.

Management of rivaroxaban in relation to bodyweight and body mass index

Being overweight or obese is associated with a higher individual risk of venous thromboembolism and poorer postprocedural outcomes after hip or knee replacement surgery. In addition, there is evidence that obesity represents a significant driving factor for the current and projected prevalence of atrial fibrillation. Rivaroxaban and other direct oral anticoagulants offer fixed-dose regimens for these indications. They do not require therapeutic drug monitoring or dose adjustment according to the weight of the patient. However, primary care physicians seem to be hesitant to accept the concept of a fixed-dose regimen for patients at extremes of weight, perhaps because of familiarity with weight-based dosing of other drugs including low molecular weight heparins. The main concerns related to unadjusted dosing are increased exposure in underweight patients leading to a risk of excessive bleeding and conversely to underanticoagulation of overweight patients. Rivaroxaban has shown similar efficacy and a similar or better safety profile compared with standard treatment for several venous and arterial indications, including venous thromboembolism, nonvalvular atrial fibrillation, and acute coronary syndrome. Prespecified subgroup analyses of patients stratified by weight or body mass index demonstrated outcomes that were consistent with the overall analysis and within each weight and body mass index group. The results suggest that standard-dose rivaroxaban can be safely prescribed in adult patients of all weights.

Gene regulatory networks in atrial fibrillation

Atrial fibrillation (AF) is the most frequent arrhythmogenic syndrome in humans. With an estimate incidence of 1%-2% in the general population, AF raises up to almost 10%-12% in 80+ years. Thus, AF represents nowadays a highly prevalent medical problem generating a large economic burden. At the electrophysiological level, distinct mechanisms have been elucidated. Yet, despite its prevalence, the genetic and molecular culprits of this pandemic cardiac electrophysiological abnormality have remained largely obscure. Molecular genetics of AF familiar cases have demonstrated that single nucleotide mutations in distinct genes encoding for ion channels underlie the onset of AF, albeit such alterations only explain a minor subset of patients with AF. In recent years, analyses by means of genome-wide association studies have unraveled a more complex picture of the etiology of AF, pointing out to distinct cardiac-enriched transcription factors, as well as to other regulatory genes. Furthermore a new layer of regulatory mechanisms have emerged, i.e., post-transcriptional regulation mediated by non-coding RNA, which have been demonstrated to exert pivotal roles in cardiac electrophysiology. In this manuscript, we aim to provide a comprehensive review of the genetic regulatory networks that if impaired exert electrophysiological abnormalities that contribute to the onset, and subsequently, on self-perpetuation of AF.

Evaluating the Atrial Myopathy Underlying Atrial Fibrillation: Identifying the Arrhythmogenic and Thrombogenic Substrate

Atrial disease or myopathy forms the substrate for atrial fibrillation (AF) and underlies the potential for atrial thrombus formation and subsequent stroke. Current diagnostic approaches in patients with AF focus on identifying clinical predictors with the evaluation of left atrial size by echocardiography serving as the sole measure specifically evaluating the atrium. Although the atrial substrate underlying AF is likely developing for years before the onset of AF, there is no current evaluation to identify the preclinical atrial myopathy. Atrial fibrosis is 1 component of the atrial substrate that has garnered recent attention based on newer MRI techniques that have been applied to visualize atrial fibrosis in humans with prognostic implications regarding the success of treatment. Advanced ECG signal processing, echocardiographic techniques, and MRI imaging of fibrosis and flow provide up-to-date approaches to evaluate the atrial myopathy underlying AF. Although thromboembolic risk is currently defined by clinical scores, their predictive value is mediocre. Evaluation of stasis via imaging and biomarkers associated with thrombogenesis may provide enhanced approaches to assess risk for stroke in patients with AF. Better delineation of the atrial myopathy that serves as the substrate for AF and thromboembolic complications might improve treatment outcomes. Furthermore, better delineation of the pathophysiologic mechanisms underlying the development of the atrial substrate for AF, particularly in its earlier stages, could help identify blood and imaging biomarkers that could be useful to assess risk for developing new-onset AF and suggest specific pathways that could be targeted for prevention.

Dosing of Target-Specific Oral Anticoagulants in Special Populations

OBJECTIVE

To review current literature for target-specific oral anticoagulants (TSOACs) and provide critical analysis for dosing recommendations in special population groups.

DATA SOURCES

A literature search was conducted in Medline (1996 to April week 2 2015) and Embase (1980 to 2015 week 16) using key terms dabigatran, rivaroxaban, apixaban, edoxaban, kidney diseases, liver diseases, elderly, obesity, and special populations.

STUDY SELECTION AND DATA EXTRACTION

Randomized controlled trials in English assessing efficacy and safety of TSOACs in healthy adults and special populations were selected for analysis.

DATA SYNTHESIS

Phase 3 trials for TSOACs predominately excluded patients with severe renal impairment or active liver disease. There were no exclusion criteria based on age, body weight or body mass index. Additional conclusions were made in special populations, including those with renal or liver impairment and obese and elderly patients, based on secondary analyses, pharmacokinetic, and pharmacodynamic studies.

CONCLUSIONS

Pharmacokinetic and pharmacodynamic changes associated special populations may alter clinical decision with regard to drug selection and dosing. It is valuable to understand the rationale for labeled dosing recommendations in nonvalvular atrial fibrillation and venous thromboembolism treatment and prevention, particularly in patients that fall into special population groups. Furthermore, the use of TSOACs is likely to increase as clinicians gain experience with these agents and additional TSOACs and indications are approved.

Relationship Between Obesity and Driving

Obesity, which has become epidemic throughout many parts of the world, is known to be a risk factor for a range of diseases including hypertension, diabetes, and vascular disease. Based on this review, it also appears that obesity is associated with increased crash risk and increased risk of serious or fatal injury in a crash. The problem is particularly an issue for commercial truck drivers. Data are presented showing the high prevalence of obesity in truck drivers. Inadequate sleep, poor nutrition, lack of exercise, and the sedentary nature of driving all contribute to the risk of obesity. The obesity related condition of obstructive sleep apnea (OSA) is known to increase crash risk. Treatment of this condition has been demonstrated to improve driving performance and to reduce crash risk. Screening truck drivers for obesity related health conditions, such as OSA, would be expected to result in public safety benefits.