What do we currently know about metabolic syndrome and atrial fibrillation?

Obesity: the perfect storm for heart failure

Obesity condition causes morphological and functional alterations involving the cardiovascular system. These can represent the substrates for different cardiovascular diseases, such as atrial fibrillation, coronary artery disease, sudden cardiac death, and heart failure (HF) with both preserved ejection fraction (EF) and reduced EF. Different pathogenetic mechanisms may help to explain the association between obesity and HF including left ventricular remodelling and epicardial fat accumulation, endothelial dysfunction, and coronary microvascular dysfunction. Multi-imaging modalities are required for appropriate recognition of subclinical systolic dysfunction typically associated with obesity, with echocardiography being the most cost-effective technique. Therapeutic approach in patients with obesity and HF is challenging, particularly regarding patients with preserved EF in which few strategies with high level of evidence are available. Weight loss is of extreme importance in patients with obesity and HF, being a primary therapeutic intervention. Sodium-glucose co-transporter-2 inhibitors have been recently introduced as a novel tool in the management of HF patients. The present review aims at analysing the most recent studies supporting pathogenesis, diagnosis, and management in patients with obesity and HF.

Meta-analysis of the Current Research on the Relationship Between Blood Lipid Levels and the Occurrence of Atrial Fibrillation

BACKGROUND

There is still debate in the literature about the relationship between lipid profile and the occurrence of atrial fibrillation (AF). In order to assess the association between blood lipid profiles and incidence of AF, this review was conducted to perform a meta-analysis of all available studies.

METHODS

This review analysed all studies up to 28 February 2023 in PubMed, Google Scholar, and the Cochrane Library that included data regarding blood lipid levels and incidence of AF. For the purpose of calculating pooled estimates, the hazard ratios were extracted from all studies.

RESULTS

Fourteen studies including 19 cohorts with 3,990,484 patients were included in this meta-analysis. An elevation of one standard deviation in total cholesterol (TC) level was associated with an 8% reduction (HR=0.92, 0.88-0.96; p<0.01) in the risk of developing AF. Although increased low-density lipoprotein cholesterol levels were associated with a 7% reduction in the development of AF (HR=0.93, 0.87-1.00; p=0.04), there was high heterogeneity in the random effects model (I2=92%). Changes in high-density lipoprotein cholesterol and triglyceride levels were not found to be associated with AF risk in the pooled analysis. Dose-response meta-analysis showed that TC was inversely linearly associated with the risk of AF (p<0.001).

CONCLUSIONS

Higher TC levels were shown to be independently attributed to an increased risk of AF in individuals without cardiovascular disease. There was no association between the incidence of AF and triglyceride, high-density lipoprotein cholesterol, or low-density lipoprotein cholesterol blood levels.

Estimates of the global, regional, and national burden of atrial fibrillation in older adults from 1990 to 2019: insights from the Global Burden of Disease study 2019

Background

Atrial fibrill ation (AF) is a predominant public health concern in older adults. Therefore, this study aimed to explore the global, regional, and national burden of AF in older adults aged 60-89 between 1990 and 2019.

Methods

The morbidity, mortality, disability-adjusted life years (DALYs), and age-standardized rates of AF were refined from the Global Burden of Diseases study 2019. The epidemiological characteristics were assessed based on numerical values, age-standardized rates per 100,000 person-years, and estimated annual percentage changes (EAPC).

Results

Globally, a total of 33.31 million AF cases, 219.4 thousand deaths, and 65.80 million DALYs were documented in 2019. There were no appreciable changes in EAPC from 1990 to 2019. The disease burden of AF differed significantly across different territories and countries. At the national level, China exhibited the highest number of incident cases [818,493 (562,871-1,128,695)], deaths [39,970 (33,722-46,387)], and DALYs [1,383,674 (1,047,540-1,802,516)]. At the global level, high body mass index (BMI) and high systolic blood pressure (SBP) were two predominant risk factors contributing to the proportion of AF-related deaths.

Conclusion

AF in older adults remains a major public health concern worldwide. The burden of AF varies widely at both national and regional levels. From 1990 to 2019, the cases of incidences, deaths, and DALYs have shown a global increase. The ASIR, ASMR, and ASDR have declined in the high-moderate and high SDI regions; however, the burden of AF increased promptly in the lower SDI regions. Special attention should be paid to the main risk factors for high-risk individuals with AF, which can help control systolic blood pressure and body mass index within normal limits. Over all, it is necessary to illustrate the features of the global AF burden and develop more effective and targeted prevention and treatment strategies.

Evaluation of the Paradoxical Association Between Lipid Levels and Incident Atrial Fibrillation According to Statin Usage: A Nationwide Cohort Study

Objective

Higher levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) are associated with a lower risk of atrial fibrillation (AF). Statin use might exert confounding effects on the paradoxical associations; however, the relationships that distinguish statin users from non-users have not been thoroughly evaluated.

Methods

From the Korean National Health Insurance Database, we included 9,778,014 adults who underwent a health examination in 2009. The levels of TC and LDL-C at the health examination were categorized into quartile values of the total study population. We grouped the study population into statin users and non-users and investigated the associations between TC, LDL-C, and the risk of incident AF.

Results

Of the total population, 867,336 (8.9%) were taking statins. During a mean follow-up of 8.2 years, inverse associations of TC - AF and LDL-C - AF were observed; higher levels of TC and LDL-C were associated with the lower risk of AF in the total population. Overall, statin users showed higher AF incidence rate than non-users, but the inverse associations of TC - AF and LDL-C - AF were consistently observed irrespective of statin usage; adjusted hazard ratio with 95% confidence interval was 0.81 (0.79-0.84) for statin users and 0.81 (0.80-0.83) for non-users in the highest TC quartile, and 0.84 (0.82-0.87) for statin users and 0.85 (0.84-0.86) for non-users in the highest LDL-C quartile (all p<0.001).

Conclusion

The paradoxical relationship between lipid levels (TC and LDL-C) and the risk of AF remains consistent in both statin users and non-users.

Risk prediction for new-onset atrial fibrillation using the Minnesota code electrocardiography classification system

Background

Few risk models are available to predict future onset of atrial fibrillation (AF) in workers. We aimed to develop risk prediction models for new-onset AF, using annual health checkup (HC) data with electrocardiogram findings.

Methods and Results

We retrospectively included 56,288 factory or office workers (mean age = 51.5 years, 33.0% women) who underwent a HC at a medical center and fulfilled the following criteria; age ≥ 40 years, no history of AF, and greater than 1 annual follow-up HC in 2013–2016. Using Cox models with the Akaike information criterion, we developed and compared prediction models for new-onset AF with and without the Minnesota code information. We externally validated the discrimination accuracy of the models in a general Japanese population cohort, the Hisayama cohort. During the median 3.0-year follow-up, 209 (0.37%) workers developed AF. Age, sex, waist circumference, blood pressure, LDL cholesterol, and γ-GTP were associated with new-onset of AF. Using the Minnesota code information, the AUC significantly improved from 0.82 to 0.84 in the derivation cohort and numerically improved from 0.78 to 0.79 in the validation cohort, and from 0.77 to 0.79 in the Hisayama cohort. The NRI and IDI significantly improved in all and male subjects in both the derivation and validation cohorts, and in female subjects in both the validation and the Hisayama cohorts.

Conclusions

We developed useful risk model with Minnesota code information for predicting new-onset AF from large worker population validated in the original and external cohorts, although study interpretation is limited by small improvement of AUC.

Metabolic syndrome, high-sensitivity C-reactive protein levels and the risk of new-onset atrial fibrillation: Results from the Kailuan Study

BACKGROUND AND AIMS

Some studies have reported that metabolic syndrome (MS) and a high inflammatory state are risk factors for atrial fibrillation (AF). However, the combined effect of MS and a high inflammatory state on AF is still unknown. We aimed to investigate the association of MS and high-sensitivity C-reactive protein (hs-CRP) levels with the risk of AF in a large community-based population.

METHODS AND RESULTS

A total of 81,092 subjects from the Kailuan Study with electrocardiogram examination and hs-CRP data at baseline (1st examination, 2006-2007) were included in this study. The enrolled population was divided into 4 groups according to the presence or absence of metabolic syndrome and high hs-CRP (>3 mg/L). The follow-up examinations were performed every two years (2nd examination, 2008-2009; 3rd examination, 2010-2011; 4th examination, 2012-2013; 5th examination, 2014-2015). All participants were followed until the occurrence of AF or the date of the last examination. After a mean time of 7.2 ± 2.0 years, a total of 271 individuals developed incident AF. MS or high hs-CRP alone was not associated with incident AF after multivariable adjustment. However, multiple Cox regression analysis showed that subjects with MS and hs-CRP > 3 mg/L had a greater risk for AF than those without MS and with hs-CRP ≤ 3 mg/L (hazard ratio, 1.61; 95% confidence interval 1.08-2.41; P = 0.019).

CONCLUSION

MS combined with a high hs-CRP level is associated with an increased risk for AF in the Chinese population. However, the mechanism is unknown and awaits further study. TRIAL REGISTRATION SITE: http://www.chictr.org.cn/index.aspx.

REGISTRATION NUMBER

ChiCTR-TNRC-11001489.

Genomic and Proteomic Study of the Inflammatory Pathway in Patients With Atrial Fibrillation and Cardiometabolic Syndrome

Atrial fibrillation (AF) and cardiometabolic syndrome (CMS) have been linked to inflammation and fibrosis. However, it is still unknown which inflammatory cytokines contribute to the pathogenesis of AF. Furthermore, cardiometabolic syndrome (CMS) risk factors such as obesity, hypertension, insulin resistance/glucose intolerance are also associated with inflammation and increased level of cytokines and adipokines. We hypothesized that the inflammatory immune response is exacerbated in patients with both AF and CMS compared to either AF or CMS alone. We investigated inflammatory cytokines and fibrotic markers as well as cytokine genetic profiles in patients with lone AF and CMS. CMS, lone AF patients, patients with both lone AF and CMS, and control patients were recruited. Genetic polymorphisms in inflammatory and fibrotic markers were assessed. Serum levels of connective tissue growth factor (CTGF) were tested along with other inflammatory markers including platelet-to-lymphocyte ratio (PLR), monocyte-to-HDL ratio (MHR) in three groups of AF+CMS, AF, and CMS patients. There was a trend in the CTGF levels for statistical significance between the AF and AF+CMS group (P = 0.084). Genotyping showed high percentages of patients in all groups with high secretor genotypes of Interleukin-6 (IL-6) (P = 0.037). Genotyping of IFN-γ and IL-10 at high level showed an increase in expression in the AF + CMS group compared to AF and CMS alone suggesting an imbalance between the inflammatory and anti-inflammatory cytokines which is exacerbated by AF. Serum cytokine inflammatory cytokine levels showed that IL-4, IL-5, IL-10, IL-17F, and IL-22 were significant between the AF, AF+CMS, and CMS patients. Combination of both CMS and AF may be associated with a higher degree of inflammation than what is seen in either CMS or AF alone. Thus, the identification of a biomarker capable of identifying metabolic syndrome associated with disease will help in identification of a therapeutic target in treating this devastating disease.

Blood lipid profiles and risk of atrial fibrillation: A systematic review and meta-analysis of cohort studies

BACKGROUND

There is an increasing body of evidence associating traditional cardiovascular risk factors with atrial fibrillation (AF), but the relationship between blood lipid profiles and the risk of AF remains controversial.

OBJECTIVE

This study aimed to conduct a systemic review and meta-analysis of large cohort studies to evaluate the relationship between blood lipid profiles and incident AF.

METHODS

PubMed and Embase were searched up to January 31, 2019, for cohort studies that reported the relationship between blood lipid levels and incident AF. The hazard ratios or odds ratios of the highest vs lowest categories of lipid levels were extracted to calculate pooled estimates. Sensitivity analysis and meta-regression were performed to explore potential sources of heterogeneity.

RESULTS

Eleven studies were included in the meta-analysis, including 9 studies for total cholesterol (TC), 5 for low-density lipoprotein cholesterol (LDL-C), 8 for high-density lipoprotein cholesterol (HDL-C), and 8 for triglyceride. Serum TC and LDL-C levels were inversely related to AF risk (relative risk [RR] = 0.81, 95% confidence interval [CI]: 0.72-0.92; RR = 0.79, 95% CI: 0.70-0.88, respectively). Likewise, elevated HDL-C levels were associated with a reduced AF risk (RR = 0.86, 95% CI: 0.76-0.97), whereas no significant association was observed between triglyceride levels and incident AF (RR = 1.02, 95% CI: 0.90-1.17).

CONCLUSIONS

Our meta-analysis of large cohort studies found an inverse relationship between serum TC, LDL-C, and HDL-C levels and AF risk, although there was no significant association between TG levels and incident AF. Future studies regarding AF risk stratification may take these blood lipids into consideration, and further efforts are needed to investigate the potential mechanisms.

Association of metabolic syndrome and chronic kidney disease with atrial fibrillation: A nationwide population-based study in Korea

AIMS

Metabolic syndrome (MetS) and chronic kidney disease (CKD) are significant risk factors for incident atrial fibrillation (AF). Few studies have reported the synergistic effect of MetS and CKD on development of AF. We investigated the individual and synergistic effects of MetS and CKD on the risk of incident AF.

METHODS

We studied a retrospective cohort comprising 22,886,663 Koreans whose data was obtained from the national health claims database established by the Korean National Health Insurance Service between 2008 and 2013. Patients were classified into a MetS and a CKD group and followed-up until 2016 for new-onset AF. A Cox proportional hazards model assessed the independent and synergistic effect of MetS and CKD on the risk of incident AF.

RESULTS

The prevalence of MetS and CKD in these patients was 27.4% and 5.4%, respectively. During a mean follow-up of 5.4 years, AF developed in 225,529 patients (1% of the total cohort). The adjusted hazard ratio (HR) for incident AF was 1.38 (95% confidence interval [CI] 1.36-1.39) for MetS, and 1.35 (95% CI 1.34-1.37) for CKD. Patients with MetS and CKD showed a higher risk of AF (HR 1.75, 95% CI 1.73-1.78) than that observed in those without MetS and CKD.

CONCLUSIONS

The combination of MetS and CKD showed a high risk of development of AF in a large-scale nationwide cohort. Further studies are warranted to determine whether pharmacological and/or lifestyle interventions can control/manage these modifiable risk factors to reduce the risk of development of AF.

Metabolically Healthy Obesity and Risk for Atrial Fibrillation: The HUNT Study

OBJECTIVE

Atrial fibrillation (AF) is the most common arrhythmia and has been described as a global epidemic. Although AF is associated with both obesity and its metabolic consequences, little is known about the association between metabolically healthy obesity and AF.

METHODS

In a population-based study, 47,870 adults were followed for incident AF from 2006 to 2008 until 2015. Participants were classified according to BMI and metabolic status (using waist circumference, triglycerides, high-density lipoprotein cholesterol, blood pressure, and glucose) at baseline.

RESULTS

During a median follow-up of 8.1 years, 1,758 participants developed AF. Compared with metabolically healthy individuals with BMI < 25 kg/m² , the multivariable-adjusted hazard ratios for metabolically healthy and unhealthy obesity were 1.6 (95% CI: 1.2 to 2.1) and 1.6 (95% CI: 1.3 to 1.9), respectively. AF risk increased according to the severity of obesity.

CONCLUSIONS

Metabolically healthy and unhealthy obesity increased AF risk to a similar extent. Severity of obesity was positively associated with AF risk regardless of metabolic status.

Monotherapy of experimental metabolic syndrome: II. Study of cardiovascular effects

Metabolic syndrome belongs to the most important risk factors of cardiovascular diseases. The aim of this study was to investigate changes in cardiovascular system induced by high cholesterol and high fat diet (HCHF) in HTG rats and their influence by a pyridoindole antioxidant - SMe1EC2 (S). The effects of S were compared with those of atorvastatin (A). Male HTG rats were fed HCHF (1% cholesterol + 7.5% lard) for 4 weeks. S and A were administered p.o., 50 mg/kg b.w. Following experimental groups were used: Wistar rats (W), hypertriglyceridemic rats (HTG), HTG rats fed HCHF (CHOL), HTG+S (S-HTG), CHOL+S (S-CHOL), and CHOL+A (A-CHOL). Values of blood pressure (BP) and selected ECG parameters were monitored in conscious animals, functions of the isolated heart and aorta were analyzed ex vivo. At the end of the experiment, systolic (sBP) and diastolic (dBP) blood pressure was increased in HTG and CHOL. S and A decreased BP in all treated groups. Accordingly with BP changes, the aortic endothelial function of CHOL was damaged. Both S and A administration ameliorated the endothelium-dependent relaxation to values of W. PQ and QTc intervals were prolonged in CHOL, while the treatment with S or A improved ECG findings. Prodysrhythmogenic threshold was decreased significantly in CHOL and both treatments returned it to the control values. In conclusion, HCHF increased BP, impaired endothelial relaxation of the aorta and potentiated susceptibility of myocardium to dysrhythmias. The effect of S on the changes induced by HCHF diet was more pronounced than that of A.

The association between insulin resistance and atrial fibrillation: A cross-sectional analysis from SPRINT (Systolic Blood Pressure Intervention Trial)

It is unclear whether metabolic syndrome (MetS) is associated with atrial fibrillation (AF) in an older population with greater cardiovascular risk, including those with chronic kidney disease. The authors investigated the association between MetS and AF in participants in SPRINT (Systolic Blood Pressure Intervention Trial). MetS was defined based on the Modified Third National Cholesterol Education Program. The baseline prevalence rate for MetS was 55%, while 8.2% of the participants had AF. In multivariate regression analyses, AF was not associated with presence of MetS in either chronic kidney disease or non-chronic kidney disease subgroups. Age, race, history of cardiovascular diseases, decreased triglycerides, decreased pulse pressure, and albuminuria remained significantly associated with AF risk. In contrast to the general population, MetS was not associated with AF in the older population with increased cardiovascular risk studied in SPRINT.

Linking atrial fibrillation with non-alcoholic fatty liver disease: potential common therapeutic targets

Non-alcoholic fatty liver disease (NAFLD) and atrial fibrillation (AF) are common chronic non-infectious diseases with rising incidences. NAFLD is an independent risk factor for the onset of AF, after adjusting potentially related factors. The pathogenesis of these diseases share several mechanisms including reduced adiponectin level, insulin resistance, and renin angiotensin aldosterone system (RAAS) activation, in addition to activation of common disease pathways that promote inflammation, oxidative stress, and fibrosis. Furthermore, statins and RAAS blockers exert therapeutic effects concurrently on NAFLD and AF. The common pathogenesis of NAFLD and AF may serve as a potential therapeutic target in the future.

Trajectories of Cardiovascular Risk Factors and Incidence of Atrial Fibrillation Over a 25-Year Follow-Up: The ARIC Study (Atherosclerosis Risk in Communities)

BACKGROUND

Timing and trajectories of cardiovascular risk factor (CVRF) development in relation to atrial fibrillation (AF) have not been described previously. We assessed trajectories of CVRF and incidence of AF over 25 years in the ARIC study (Atherosclerosis Risk in Communities).

METHODS

We assessed trajectories of CVRF in 2456 individuals with incident AF and 6414 matched control subjects. Subsequently, we determined the association of CVRF trajectories with the incidence of AF among 10 559 AF-free individuals (mean age, 67 years; 52% men; 20% blacks). Risk factors were measured during 5 examinations between 1987 and 2013. Cardiovascular events, including incident AF, were ascertained continuously. We modeled the prevalence of risk factors and cardiovascular outcomes in the period before and after AF diagnosis and the corresponding index date for control subjects using generalized estimating equations. Trajectories in risk factors were identified with latent mixture modeling. The risk of incident AF by trajectory group was examined with Cox models.

RESULTS

The prevalence of stroke, myocardial infarction, and heart failure increased steeply during the time close to AF diagnosis. All CVRFs were elevated in AF cases compared with controls >15 years before diagnosis. We identified distinct trajectories for all the assessed CVRFs. In general, individuals with trajectories denoting long-term exposure to CVRFs had increased AF risk even after adjustment for single measurements of the CVRFs.

CONCLUSIONS

AF patients have increased prevalence of CVRF many years before disease diagnosis. This analysis identified diverse trajectories in the prevalence of these risk factors, highlighting their different roles in AF pathogenesis.

Evaluation of the Association Between Retinal Vein Occlusion and the Risk of Atrial Fibrillation Development: A 12-Year, Retrospective Nationwide Cohort Study

We aimed to evaluate the risk of atrial fibrillation (AF) development following retinal vein occlusion (RVO). We performed a nationwide propensity score-matched cohort study by retrospectively reviewing a database from the Korean National Health Insurance Service, comprising approximately 1 million random subjects. RVO and AF were diagnosed based on the Korean Classification of Disease codes. The RVO group was composed of patients with an initial diagnosis of RVO made between 2003 and 2007 (n = 1,801), excluding those who were diagnosed in 2002. The comparison group was composed of randomly selected patients (5 for each patient with RVO, n = 8,930) who were matched to the RVO group according to sociodemographic factors and the year of enrollment. Each sampled patient was tracked until 2013. The predictive value of RVO for AF was analyzed using Cox regression analysis with a hazard ratio (HR) and confidence interval (CI). AF developed in 6.5% of patients in the RVO group and 4.0% of those in the comparison group (p < 0.001). RVO was associated with a greater risk of AF development after adjusting for possible confounders (HR, 1.35; 95% CI, 1.09–1.67). An association between RVO and subsequent AF development was found after adjusting for possible confounding factors.

VLDL from Metabolic Syndrome Individuals Enhanced Lipid Accumulation in Atria with Association of Susceptibility to Atrial Fibrillation

Metabolic syndrome (MetS) represents a cluster of metabolic derangements. Dyslipidemia is an important factor in MetS and is related to atrial fibrillation (AF). We hypothesized that very low density lipoproteins (VLDL) in MetS (MetS-VLDL) may induce atrial dilatation and vulnerability to AF. VLDL was therefore separated from normal (normal-VLDL) and MetS individuals. Wild type C57BL/6 male mice were divided into control, normal-VLDL (nVLDL), and MetS-VLDL (msVLDL) groups. VLDL (15 µg/g) and equivalent volumes of saline were injected via tail vein three times a week for six consecutive weeks. Cardiac chamber size and function were measured by echocardiography. MetS-VLDL significantly caused left atrial dilation (control, n = 10, 1.64 ± 0.23 mm; nVLDL, n = 7, 1.84 ± 0.13 mm; msVLDL, n = 10, 2.18 ± 0.24 mm; p < 0.0001) at week 6, associated with decreased ejection fraction (control, n = 10, 62.5% ± 7.7%, vs. msVLDL, n = 10, 52.9% ± 9.6%; p < 0.05). Isoproterenol-challenge experiment resulted in AF in young msVLDL mice. Unprovoked AF occurred only in elderly msVLDL mice. Immunohistochemistry showed excess lipid accumulation and apoptosis in msVLDL mice atria. These findings suggest a pivotal role of VLDL in AF pathogenesis for MetS individuals.

Comparison of the frequency of atrial fibrillation in young obese versus young nonobese men undergoing examination for fitness for military service

The association between body mass index (BMI) in young adulthood and long-term risk of atrial fibrillation (AF) has not yet been examined for men. We conducted a population-based 36-year cohort study to examine the BMI-associated risk of AF in 12,850 young men who had BMI measured at their examination of fitness for military service. AF was identified from the Danish National Registry of Patients, covering all Danish hospitals since 1977. We began follow-up on the twenty-second birthday of each subject and continued until the occurrence of AF, emigration, death, or December 31, 2012. We used Cox regression to compute hazard ratios (HRs) with 95% confidence intervals (CIs), adjusting for education and height. The cohort contributed a total of 375,888 person-years of follow-up and the median follow-up time was 26 years (mean 29 years). The incidence of AF per 100,000 person-years was 53 for men of normal weight (BMI: 18.5 to 24.9 kg/m(2)), 54 for underweight men (BMI <18.5 kg/m(2)), 106 for overweight men (BMI: 25.0 to 24.9 kg/m(2)), and 144 for obese men (BMI ≥30 kg/m(2)). With normal weight as the reference group, the adjusted HR for AF was 0.99 (95% CI 0.52 to 1.87) for underweight men, 2.08 (95% CI 1.48 to 2.92) for overweight men, and 2.87 (95% CI 1.46 to 5.62) for obese men. The adjusted HR associating 1 unit increase in BMI with AF was 1.12 (95% CI 1.07 to 1.16). In conclusion, overweight and obese young men had more than twice the risk of AF compared with young men of normal weight.