Increased pericardial adipose tissue is correlated with atrial fibrillation and left atrial dilatation

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.

Effect of epicardial fat volume on outcomes after left atrial posterior wall isolation in addition to pulmonary vein isolation in patients with persistent atrial fibrillation

Background

Greater epicardial adipose tissue (EAT) is related to higher recurrences after atrial fibrillation catheter ablation (AFCA). We investigated the effects of posterior wall box isolation (POBI) in conjunction with circumferential pulmonary vein isolation (CPVI) on rhythm outcomes according to varying EAT volumes among patients with persistent atrial fibrillation (PeAF).

Materials and methods

We included 1,187 patients with PeAF undergoing a de novo AFCA including those receiving CPVI alone (n = 687) and those receiving additional POBI (n = 500). The rhythm outcomes at 2 years post-AFCA were compared in subgroups stratified by the EAT volume using propensity overlap weighting.

Results

A reduced EAT volume was linearly associated with more favorable rhythm outcomes for additional POBI than for CPVI alone (P for interaction = 0.002). Among the patients with smaller EAT volumes (≤116.23 mL, the median value, n = 594), additional POBI was associated with a reduced AF recurrence risk as compared to CPVI only [weighted HR (hazard ratio) 0.74, 95% CI (confidence interval) 0.56–0.99]. In contrast, among the remaining 593 patients with greater EAT volumes (>116.23 mL), No difference was observed in the recurrence risk between the additional POBI and CPVI alone groups (weighted HR 1.13, 95% CI 0.84–1.52). Among 205 patients with repeat ablations, the POBI reconnection rate was more frequent in the large EAT group (77.4%) than in the small EAT group (56.7%, P = 0.034).

Conclusion

While PeAF patients with a smaller EAT volume averted AF recurrence by additional POBI after CPVI, no benefit of the POBI was observed in those with a greater EAT volume.

The Predictive Value of Epicardial Fat Tissue Volume in the Occurrence and Development of Atrial Fibrillation: A Systematic Review and Meta-Analysis

Background

Atrial fibrillation (AF) is one of the most common arrhythmias in clinical practice. Although fat is currently considered to be a risk factor for AF and a pathogenic link between epicardial fat tissue (EFT) and AF has been speculated, there are currently few clinical studies and literature data domestically or abroad.

Objective

This study conducted a meta-analysis of observational case series studies to verify the relationship between atrial fibrillation and EFT and to strengthen the predictive value of EFT in the occurrence, development, and postablative recurrence of AF.

Methods

We conducted a systematic search of the literature in electronic databases until December 2021 and supplemented this through manual searches of individual studies, reviewed articles, and reference lists in conference proceedings. This study conducted a meta-analysis to compare the differences between different populations, such as healthy participants and AF patients, healthy subjects and AF subtype cases, and paroxysmal and persistent AF with AF recurrence and without AF recurrence after ablation.

Results

Following the retrieval of 828 articles, only 22 articles were selected as research results. Accordingly, the meta-analysis results show that the volume of EFT in AF is greater than that in healthy subjects (MD = 39.34 ml, 95% CI = 27.11, 51.58); persistent AF is greater than paroxysmal AF (MD = 14.37 ml, 95% CI = 7.46, 21.27); and recurrence after ablation is greater than without recurrence (MD = 14.37 ml, 95% CI = 7.46, 21.27).

Conclusion

The results of this study further confirm the connection between EFT and AF and that EFT has a certain predictive value for the occurrence and development of AF.

Atrial Fibrillation after Coronary Bypass Surgery? Is Epicardial Fat a Risk Factor?

BACKGROUNDS

 Postoperative atrial fibrillation (POAF) is one of the most common complication of cardiac surgery. Epicardial fat tissue may play a role in the development of atrial fibrillation (AF). The aim of this study was to evaluate relationship between epicardial fat volume (EFV) and the appearance of new-onset AF in patients undergoing isolated coronary artery bypass graft (CABG) with normal echocardiographic functions.

METHODS

 Between January 2017 and June 2020, 281 coronary artery disease patients undergone isolated CABG surgery with normal echocardiographic functions were included in the study. Patient characteristics, medical history, and perioperative variables were retrospectively collected. Patients with AF predisposition factors were excluded.

RESULTS

 Sixty-seven patients (23.8%) developed postoperatively AF during hospital stay. In univariate analysis, patients with postoperative AF were older compared with sinus rhythm patients (60.78 ± 9.03 vs. 65.46 ± 9.22, p = 0.001). There are no statistically significant differences between groups and EFV compared (107.78 ± 41.04 vs. 106.66 ± 34.98 p = 0.84). Large left atrial diameter, female patient, cardiopulmonary bypass and longer cross-clamp time showed correlation between POAF without statistical significance.

CONCLUSION

 Aging is the only associated factor with AF in this study. There was no EFV difference between POAF and non-AF groups in patients undergoing isolated CABG with normal echocardiographic functions.

Development and Validation of a Machine Learning-Based Radiomics Model on Cardiac Computed Tomography of Epicardial Adipose Tissue in Predicting Characteristics and Recurrence of Atrial Fibrillation

Purpose

This study aimed to evaluate the feasibility of differentiating the atrial fibrillation (AF) subtype and preliminary explore the prognostic value of AF recurrence after ablation using radiomics models based on epicardial adipose tissue around the left atrium (LA-EAT) of cardiac CT images.

Method

The cardiac CT images of 314 patients were collected wherein 251 and 63 cases were randomly enrolled in the training and validation cohorts, respectively. Mutual information and the random forest algorithm were used to screen for the radiomic features and construct the radiomics signature. Radiomics models reflecting the features of LA-EAT were built to differentiate the AF subtype, and the multivariable logistic regression model was adopted to integrate the radiomics signature and volume information. The same methodology and algorithm were applied to the radiomic features to explore the ability for predicting AF recurrence.

Results

The predictive model constructed by integrating the radiomic features and volume information using a radiomics nomogram showed the best ability in differentiating AF subtype in the training [AUC, 0.915; 95% confidence interval (CI), 0.880–0.951] and validation (AUC, 0.853; 95% CI, 0.755–0.951) cohorts. The radiomic features have shown convincible predictive ability of AF recurrence in both training (AUC, 0.808; 95% CI, 0.750–0.866) and validation (AUC, 0.793; 95% CI, 0.654–0.931) cohorts.

Conclusions

The LA-EAT radiomic signatures are a promising tool in the differentiation of AF subtype and prediction of AF recurrence, which may have clinical implications in the early diagnosis of AF subtype and disease management.

Impaired fasting glucose: a risk factor for atrial fibrillation and heart failure

BACKGROUND

Dysglycaemia is associated with overall cardiovascular disease even at prediabetes levels. The aim of this study was to explore the association between glucose levels and future risk of developing atrial fibrillation and heart failure, respectively.

METHODS

In this prospective cohort study subjects from the Swedish AMORIS-cohort with fasting glucose from health examinations 1985-1996 without previous cardiovascular disease (N = 294,057) were followed to 31 December 2011 for incident atrial fibrillation or heart failure. Cox proportional hazard models with attained age as timescale and adjustments for sex, cholesterol, triglycerides, and socioeconomic status were used to estimate hazard ratios by glucose categorized groups (normal glucose 3.9-6.0 mmol/L, impaired fasting glucose; 6.1-6.9 mmol/L, undiagnosed diabetes ≥ 7.0 mmol/L, and diagnosed diabetes).

RESULTS

During a mean follow-up time of 19.1 years 28,233 individuals developed atrial fibrillation and 25,604 developed heart failure. The HR for atrial fibrillation was 1.19 (95% confidence interval 1.13-1.26) for impaired fasting glucose, 1.23 (1.15-1.32) for undiagnosed diabetes and 1.30 (1.21-1.41) for diagnosed diabetes. Corresponding figures for heart failure were; 1.40 (1.33-1.48), 2.11 (1.99-2.23), 2.22 (2.08-2.36) respectively. In a subset with BMI data (19%), these associations were attenuated and for atrial fibrillation only remained statistically significant among subjects with diagnosed diabetes (HR 1.25; 1.02-1.53).

CONCLUSIONS

Fasting glucose at prediabetes levels is associated with development of atrial fibrillation and heart failure. To some extent increased BMI may drive this association.

Impaired fasting glucose: a risk factor for atrial fibrillation and heart failure

BACKGROUND

Dysglycaemia is associated with overall cardiovascular disease even at prediabetes levels. The aim of this study was to explore the association between glucose levels and future risk of developing atrial fibrillation and heart failure, respectively.

METHODS

In this prospective cohort study subjects from the Swedish AMORIS-cohort with fasting glucose from health examinations 1985-1996 without previous cardiovascular disease (N = 294,057) were followed to 31 December 2011 for incident atrial fibrillation or heart failure. Cox proportional hazard models with attained age as timescale and adjustments for sex, cholesterol, triglycerides, and socioeconomic status were used to estimate hazard ratios by glucose categorized groups (normal glucose 3.9-6.0 mmol/L, impaired fasting glucose; 6.1-6.9 mmol/L, undiagnosed diabetes ≥ 7.0 mmol/L, and diagnosed diabetes).

RESULTS

During a mean follow-up time of 19.1 years 28,233 individuals developed atrial fibrillation and 25,604 developed heart failure. The HR for atrial fibrillation was 1.19 (95% confidence interval 1.13-1.26) for impaired fasting glucose, 1.23 (1.15-1.32) for undiagnosed diabetes and 1.30 (1.21-1.41) for diagnosed diabetes. Corresponding figures for heart failure were; 1.40 (1.33-1.48), 2.11 (1.99-2.23), 2.22 (2.08-2.36) respectively. In a subset with BMI data (19%), these associations were attenuated and for atrial fibrillation only remained statistically significant among subjects with diagnosed diabetes (HR 1.25; 1.02-1.53).

CONCLUSIONS

Fasting glucose at prediabetes levels is associated with development of atrial fibrillation and heart failure. To some extent increased BMI may drive this association.

New Insights on the Role of Connexins and Gap Junctions Channels in Adipose Tissue and Obesity

Due to the inability to curb the excessive increase in the prevalence of obesity and overweight, it is necessary to comprehend in more detail the factors involved in the pathophysiology and to appreciate more clearly the biochemical and molecular mechanisms of obesity. Thus, understanding the biological regulation of adipose tissue is of fundamental relevance. Connexin, a protein that forms intercellular membrane channels of gap junctions and unopposed hemichannels, plays a key role in adipogenesis and in the maintenance of adipose tissue homeostasis. The expression and function of Connexin 43 (Cx43) during the different stages of the adipogenesis are differentially regulated. Moreover, it has been shown that cell–cell communication decreases dramatically upon differentiation into adipocytes. Furthermore, inhibition of Cx43 degradation or constitutive overexpression of Cx43 blocks adipocyte differentiation. In the first events of adipogenesis, the connexin is highly phosphorylated, which is likely associated with enhanced Gap Junction (GJ) communication. In an intermediate state of adipocyte differentiation, Cx43 phosphorylation decreases, as it is displaced from the membrane and degraded through the proteasome; thus, Cx43 total protein is reduced. Cx is involved in cardiac disease as well as in obesity-related cardiovascular diseases. Different studies suggest that obesity together with a high-fat diet are related to the production of remodeling factors associated with expression and distribution of Cx43 in the atrium.

Increased Pericardial Adipose Tissue in Smokers

BACKGROUND

Pericardial adipose tissue (PAT), a visceral fat depot directly located to the heart, is associated with atherosclerotic and inflammatory processes. The extent of PAT is related to the prevalence of coronary heart disease and might be used for cardiovascular risk prediction. This study aimed to determine the effect of smoking on the extent of PAT.

METHODS

We retrospectively examined 1217 asymptomatic patients (490 females, age 58.3 ± 8.3 years, smoker n = 573, non-smoker n = 644) with a multislice CT scanner and determined the PAT volume. Coronary risk factors were determined at inclusion, and a multivariate analysis was performed to evaluate the influence of smoking on PAT independent from accompanying risk factors.

RESULTS

The mean PAT volume was 215 ± 107 mL in all patients. The PAT volume in smokers was significantly higher compared to PAT volume in non-smokers (231 ± 104 mL vs. 201 ± 99 mL, p = 0.03). Patients without cardiovascular risk factors showed a significantly lower PAT volume (153 ± 155 mL, p < 0.05) compared to patients with more than 1 risk factor. Odds ratio was 2.92 [2.31, 3.61; p < 0.001] for elevated PAT in smokers.

CONCLUSION

PAT as an individual marker of atherosclerotic activity and inflammatory burden was elevated in smokers. The finding was independent from metabolic risk factors and might therefore illustrate the increased inflammatory activity in smokers in comparison to non-smokers.

Can We Decrease Epicardial and Pericardial Fat in Patients With Diabetes?

Diabetes mellitus (DM) is a chronic and complex metabolic disorder and also an important cause of cardiovascular (CV) disease (CVD). Patients with type 2 DM (T2DM) and obesity show a greater propensity for visceral fat deposition (and excessive fat deposits elsewhere) and the link between adiposity and CVD risk is greater for visceral than for subcutaneous (SC) adipose tissue (AT). There is growing evidence that epicardial AT (EAT) and pericardial AT (PAT) play a role in the development of DM-related atherosclerosis, atrial fibrillation (AF), myocardial dysfunction, and heart failure (HF). In this review, we will highlight the importance of PAT and EAT in patients with DM. We also consider therapeutic interventions that could have a beneficial effect in terms of reducing the amount of AT and thus CV risk. EAT is biologically active and a likely determinant of CV morbidity and mortality in patients with DM, given its anatomical characteristics and proinflammatory secretory pattern. Consequently, modification of EAT/PAT may become a therapeutic target to reduce the CV burden. In patients with DM, a low calorie diet, exercise, antidiabetics and statins may change the quantity of EAT, PAT or both, alter the secretory pattern of EAT, improve the metabolic profile, and reduce inflammation. However, well-designed studies are needed to clearly define CV benefits and a therapeutic approach to EAT/PAT in patients with DM.

Cardiac Adiposity and Arrhythmias: The Role of Imaging

Increased cardiac fat depots are metabolically active tissues that have a pronounced pro-inflammatory nature. Increasing evidence supports a potential role of cardiac adiposity as a determinant of the substrate of atrial fibrillation and ventricular arrhythmias. The underlying mechanism appears to be multifactorial with local inflammation, fibrosis, adipocyte infiltration, electrical remodeling, autonomic nervous system modulation, oxidative stress and gene expression playing interrelating roles. Current imaging modalities, such as echocardiography, computed tomography and cardiac magnetic resonance, have provided valuable insight into the relationship between cardiac adiposity and arrhythmogenesis, in order to better understand the pathophysiology and improve risk prediction of the patients, over the presence of obesity and traditional risk factors. However, at present, given the insufficient data for the additive value of imaging biomarkers on commonly used risk algorithms, the use of different screening modalities currently is indicated for personalized risk stratification and prognostication in this setting.

Association of pericardial adipose tissue with left ventricular structure and function: a region-specific effect?

BACKGROUND

The independent role of pericardial adipose tissue (PAT) as an ectopic fat associated with cardiovascular disease (CVD) remains controversial. This study aimed to determine whether PAT is associated with left ventricular (LV) structure and function independent of other markers of general obesity.

METHODS

We studied 2471 participants (50.9 % women) without known CVD from the Korean Genome Epidemiology Study, who underwent 2D-echocardiography with tissue Doppler imaging (TDI) and computed tomography measurement for PAT.

RESULTS

Study participants with more PAT were more likely to be men and had higher cardiometabolic indices, including blood pressure, glucose, and cholesterol levels (all P < 0.001). Greater pericardial fat levels across quartiles of PAT were associated with increased LV mass index and left atrial volume index (all P < 0.001) and decreased systolic (P = 0.015) and early diastolic (P < 0.001) TDI velocities, except for LV ejection fraction. These associations remained after a multivariable-adjusted model for traditional CV risk factors and persisted even after additional adjustment for general adiposity measures, such as waist circumference and body mass index. PAT was also the only obesity index independently associated with systolic TDI velocity (P < 0.001).

CONCLUSIONS

PAT was associated with subclinical LV structural and functional deterioration, and these associations were independent of and stronger than with general and abdominal obesity measures.

Pericardial adipose tissue is an independent risk factor of coronary artery disease and is associated with risk factors of coronary artery disease

Objective

Pericardial adipose tissue volume (PATV) is related to the mechanism of coronary artery disease (CAD), but its association with CAD risk factors is not clear. This study aimed to investigate the relationships between PATV and its associated factors.

Methods

A total of 682 inpatients were consecutively enrolled in this study. Patients were divided into the high PATV group (PATV ≥174.5 cm³; n = 506) and low PATV group (PATV  < 174.5 cm³; n = 176). Multiple linear regression analysis was conducted to evaluate the related factors of PATV. Multivariable logistic regression was used to analyze the risk factors of CAD.

Results

Left ventricular fat volume, right ventricular fat volume, body mass index, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were significant and independent risk factors of enlargement of PATV. Increased PATV was identified as an independent risk factor of CAD, and increased pulse pressure was also independently and positively correlated with CAD.

Conclusions

PATV is significantly correlated with the classic risk factors of CAD. Pulse pressure is also correlated with PATV. PATV is an independent risk factor of CAD, and pericardial adipose tissue may alternatively be used in non-invasive diagnostic examination of CAD.

Difference in epicardial adipose tissue distribution between paroxysmal atrial fibrillation and coronary artery disease

BACKGROUND

An increase in epicardial adipose tissue (EAT) volume is associated with the development of atrial fibrillation (AF) and coronary artery disease (CAD), but little is known about differences in its distribution.

METHODS AND RESULTS

We included 50 patients with paroxysmal AF (PAF), 50 patients with CAD, and 50 control patients. Using multidetector computed tomography, EAT volumes surrounding the whole heart (total EAT), the atrium (atrial-EAT), and the ventricle (ventricular-EAT) were measured. EAT atrial/ventricular (A/V) ratio was calculated by dividing atrial- by ventricular-EAT volume. The total EAT volume indexes in the PAF and CAD groups were significantly larger than those in the control group. The atrial-EAT volume index in the PAF group was significantly larger than that in the CAD and control groups, whereas the ventricular-EAT volume index in the CAD group was significantly larger than that in the PAF and control groups. Thus, EAT A/V ratio was smaller in the CAD and control group than that in the PAF group (0.28 ± 0.12 vs. 0.38 ± 0.13 vs. 0.54 ± 0.33, P < .001). Univariate and multivariate linear regression analysis showed EAT A/V ratio to be independently associated with cardiovascular disease type (PAF vs. CAD; P < .001, β = .463).

CONCLUSIONS

Atrial- and ventricular-dominant distribution of EAT was observed in the PAF and CAD groups, respectively. Uneven distribution of EAT may imply the direct contribution of EAT-related inflammation to the pathogenesis of AF or CAD.

Inflammatory and Imaging-based Predictors of Atrial Fibrillation Recurrence after Pulmonary Vein Isolation Using Electroanatomical Mapping – the INFLAMAP Study

Atrial fibrillation (AF) is the most frequent form of supraventricular arrhythmia in medical practice. It is characterized by chaotic electrical activity in the atria, which often leads to irregular and fast ventricular contractions. Pulmonary veins (PV) play an essential part in the genesis of AF. There are a series of risk factors that trigger the development and recurrence of AF after PV isolation. Despite advanced medical technology, the success rate of AF ablation is not satisfactory. The purpose of this study is to assess the preprocedural imaging and serum biomarkers linked to an increased recurrence of AF after PV isolation. The primary endpoint is represented by AF recurrence after PV isolation. In addition, the rate of cardiovascular death and the rate of major adverse cardiovascular events will be assessed in relation to the enlargement of the left atrium and the volume of epicardial adipose tissue surrounding the heart.

Differences in the structural characteristics and distribution of epicardial adipose tissue between left and right atrial fibrillation

Aims

Right atrial (RA) fibrillation (RAF) was previously characterized by initiation from RA ectopies, presence of a right-to-left dominant frequency gradient during atrial fibrillation (AF), and augmentation of the gradient by adenosine triphosphate infusion. We investigated structural characteristics of the bi-atria and epicardial adipose tissue (EAT) volume in patients with RAF.

Methods and results

By using multidetector computed tomography, RA, left atrial (LA), right and LA appendage (RAA and LAA, respectively) volumes, pulmonary vein (PV) sizes, and EAT volumes were compared between the RAF group (n = 8) and LA fibrillation (LAF) group (n = 32). Compared with the LAF group, the LA volume was smaller (median 81.3 [95% CI, 74.2-88.5] vs. 64.5 [54.8-74.2] mL/m2; P = 0.04), the LAA volume was smaller (10.1 [9.0-11.3] vs. 6.5 [4.5-8.5] mL/m2; P = 0.008), and the RAA volume was larger (10.8 [9.1-12.4] vs. 14.1 [11.6-16.6] mL/m2; P = 0.044) in the RAF group. The RA volume was not significantly different between the groups (73.6 [66.8-80.3] vs. 68.1 [57.1-79.1] mL/m2; P = 0.47). The RAF group had smaller PVs (1.44 [1.33-1.55] vs. 1.12 [0.94-1.30] cm2/m2 for the left inferior PV; P = 0.01). Both the LA-EAT and RA-EAT volumes were smaller in the RAF group than the LAF group (4.2 [2.8-5.6] vs. 9.1 [7.8-10.4] mL/m2; P < 0.001 and 5.3 [4.3-6.3] vs. 9.5 [8.4-10.6] mL/m2; P < 0.001, respectively).

Conclusion

RAF was structurally characterized by predominant RAA enlargement, small left atrium, and less EAT surrounding the atria. Electrical properties that determine the features of AF (RAF vs. LAF) may be genetically linked to structural properties.

Epicardial adipose tissue and atrial fibrillation: pathophysiological mechanisms, clinical implications, and potential therapies

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice and is associated with increased cardiovascular morbidity and mortality. Epicardial adipose tissue (EAT) serves as a biologically active organ with important endocrine and inflammatory function. Review An accumulating body of evidence suggests that EAT is associated with the initiation, perpetuation, and recurrence of AF, but the precise role of EAT in AF pathogenesis is not completely elucidated. Pathophysiological mechanisms involve adipocyte infiltration, profibrotic and pro-inflammatory paracrine effects, oxidative stress, neural mechanisms, and genetic factors.

CONCLUSIONS

Notably, EAT accumulation seems to be associated with stroke and adverse cardiovascular outcomes in AF. Weight loss, specific medications and ablation of ganglionated plexi (GP) seem to be potential therapies in this setting.

Effect of sex on glucose handling by adipocytes isolated from rat subcutaneous, mesenteric and perigonadal adipose tissue

Background

Adult rat epididymal adipocytes are able to convert large amounts of glucose to lactate and glycerol. However, fatty acid efflux is much lower than that expected from glycerol levels if they were the product of lipolysis. Use of glucose for lipogenesis is limited, in contrast with the active glycolysis-derived lactate (and other 3-carbon substrates). In this study, we analyzed whether white adipose tissue (WAT) site and sex affect these processes.

Methods

Mature adipocytes from perigonadal, mesenteric and subcutaneous WAT of female and male rats were isolated, and incubated with 7 or 14 mM glucose during 1 or 2 days. Glucose consumption, metabolite efflux and gene expression of glycolytic and lipogenesis-related genes were measured.

Results

The effects of medium initial glucose concentration were minimal on most parameters studied. Sex-induced differences that were more extensive; however, the most marked, distinct, effects between WAT sites, were dependent on the time of incubation. In general, the production of lactate was maintained during the incubation, but glycerol release rates increased with time, shifting from a largely glycolytic origin to its triacylglycerol (TAG) lipolytic release. Glycerol incorporation was concurrent with increased TAG turnover: lipolytic glycerol was selectively secreted, while most fatty acids were recycled again into TAG. Fatty acid efflux increased with incubation, but was, nevertheless, minimal compared with that of glycerol. Production of lactate and glycerol from glucose were maximal in mesenteric WAT.

Discussion

Female rats showed a higher adipocyte metabolic activity than males. In mesenteric WAT, gene expression (and substrate efflux) data suggested that adipocyte oxidation of pyruvate to acetyl-CoA was higher in females than in males, with enhanced return of oxaloacetate to the cytoplasm for its final conversion to lactate. WAT site differences showed marked tissue specialization-related differences. Use of glucose for lipogenesis was seriously hampered over time, when TAG turnover-related lipolysis was activated. We postulate that these mechanisms may help decrease glycaemia and fat storage, producing, instead, a higher availability of less-regulated 3-carbon substrates, used for energy elsewhere.

Epicardial Adipose Tissue Is Associated With Left Atrial Dysfunction in People Without Obstructive Coronary Artery Disease or Atrial Fibrillation

BACKGROUND

Epicardial adipose tissue (EAT) is a metabolically active visceral fat depot. Although EAT volume is associated with the incidence and burden of atrial fibrillation (AF), its role in subclinical left atrial (LA) dysfunction is unclear. This study aims to evaluate the relationships between EAT volumes, LA function, and LA global longitudinal strain.

METHODS

One hundred and thirty people without obstructive coronary artery disease or AF were prospectively recruited into the study in Australia and underwent cardiac computed tomography and echocardiography. EAT volume was quantified from cardiac computed tomography. Echocardiographic 3-dimensional (3D) volumetric measurements and 2D speckle-tracking analysis were performed.

RESULTS

Using the overall median body surface area-indexed total EAT volume (EATi), the study cohort was divided into 2 groups of larger and smaller EATi volume. Subjects with larger EATi volume had significantly impaired LA reservoir function (3D LA ejection fraction, 46.1% ± 8.9% vs 49.0% ± 7.0%, P = 0.044) and reduced LA global longitudinal strain (37.6% ± 10.2% vs 44.1% ± 10.7%, P < 0.001). Total EATi volume was a predictor of impaired 2D LA global longitudinal strain (standardized β = -0.204, P = 0.034), reduced 3D LA ejection fraction (standardized β = -0.208, P = 0.036), and reduced 3D active LA ejection fraction (standardized β = -0.211, P = 0.017). Total EATi volume, rather than LA EATi volume, was the more important predictor of LA dysfunction.

CONCLUSIONS

Indexed EAT volume is independently associated with subclinical LA dysfunction and impaired global longitudinal strain in people without obstructive coronary artery disease or a history of AF.

Obesity and metabolic features associated with long-term developing diastolic dysfunction in an initially healthy population-based cohort

BACKGROUND

Diastolic dysfunction (DD) is increasingly common. However, its metabolic determinants are poorly known. This study aims to determine which metabolic and inflammatory features predict DD in initially healthy adults.

METHODS

We prospectively analyzed the association between metabolic features and DD in 728 initially healthy adults aged 30-60 from Eastern France enrolled in the STANISLAS population-based cohort. Clinical and biological cardiovascular features were collected at baseline (1994-1995). DD was assessed twenty years later (2011-2016) by echocardiography using current international guidelines. For replication purposes, 1463 subjects from the Malmö Preventive Project cohort were analyzed.

RESULTS

In the STANISLAS cohort, 191 subjects (26.2%) developed DD. In age-sex-adjusted logistic models, significant predictors of DD were body mass index (BMI, odds ratio for 1-standard-deviation increase (OR) 1.28, 95% CI 1.08-1.52), waist circumference (WC, OR 1.48, 95% CI 1.18-1.84), waist-hip ratio (OR 1.53, 95% CI 1.16-2.02), systolic blood pressure (OR 1.19, 95% CI 1.00-1.43) and triglycerides (TG, OR 1.18, 95% CI 1.00-1.40). Subjects with elevated WC (> 80th percentile) and TG (> 50th percentile) had a twofold higher DD risk (age-sex-adjusted odds ratio 2.00, 95% CI 1.20-3.31, P = 0.008), whereas no such interplay was observed for BMI. In the Malmö cohort, BMI was similarly associated with DD; participants with both elevated BMI and TG were at higher DD risk (age-sex-adjusted odds ratio 1.61, 95% CI 1.18-2.20, P = 0.002).

CONCLUSIONS

Subjects with elevated WC and TG may have a higher long-term DD risk. Prevention targeting visceral obesity may help reduce the incidence of DD.

Epicardial fat and atrial fibrillation: current evidence, potential mechanisms, clinical implications, and future directions

Obesity is increasingly recognized as a major modifiable determinant of atrial fibrillation (AF). Although body mass index and other clinical measures are useful indications of general adiposity, much recent interest has focused on epicardial fat, a distinct adipose tissue depot that can be readily assessed using non-invasive imaging techniques. A growing body of data from epidemiological and clinical studies has demonstrated that epicardial fat is consistently associated with the presence, severity, and recurrence of AF across a range of clinical settings. Evidence from basic science and translational studies has also suggested that arrhythmogenic mechanisms may involve adipocyte infiltration, pro-fibrotic, and pro-inflammatory paracrine effects, oxidative stress, and other pathways. Despite these advances, however, significant uncertainty exists and many questions remain unanswered. In this article, we review our present understanding of epicardial fat, including its classification and quantification, existing evidence implicating its role in AF, potential mechanisms, implications for clinicians, and future directions for research.

Epicardial Fat, Paracrine-mediated Inflammation and Atrial Fibrillation

Atrial fibrillation is the most frequent arrhythmia in adults, becoming more frequent with age. Recent clinical studies demonstrated that epicardial fat is linked with atrial fibrillation induction and recurrence. The arrhythmogenic mechanism consists in the fact that the epicardial adipose tissue is metabolically active, inducing local inflammation and enhancing the oxidative stress, which lead to atrial fibrillation as well as atherosclerosis. Having metabolic activity and secreting various anti- and pro-inflammatory biomarkers, the fat surrounding the heart has been linked to the complex process of coronary plaque vulnerabilization. This clinical update aims to summarize the role of epicardial adipose tissue in the pathogenesis, persistence, and severity of atrial fibrillation.

Increased Ca buffering underpins remodelling of Ca2+ handling in old sheep atrial myocytes

KEY POINTS

Ageing is associated with an increased risk of cardiovascular disease and arrhythmias, with the most common arrhythmia being found in the atria of the heart. Little is known about how the normal atria of the heart remodel with age and thus why dysfunction might occur. We report alterations to the atrial systolic Ca2+ transient that have implications for the function of the atrial in the elderly. We describe a novel mechanism by which increased Ca buffering can account for changes to systolic Ca2+ in the old atria. The present study helps us to understand how the processes regulating atrial contraction are remodelled during ageing and provides a basis for future work aiming to understand why dysfunction develops.

ABSTRACT

Many cardiovascular diseases, including those affecting the atria, are associated with advancing age. Arrhythmias, including those in the atria, can arise as a result of electrical remodelling or alterations in Ca2+ homeostasis. In the atria, age-associated changes in the action potential have been documented. However, little is known about remodelling of intracellular Ca2+ homeostasis in the healthy aged atria. Using single atrial myocytes from young and old Welsh Mountain sheep, we show the free Ca2+ transient amplitude and rate of decay of systolic Ca2+ decrease with age, whereas sarcoplasmic reticulum (SR) Ca content increases. An increase in intracellular Ca buffering explains both the decrease in Ca2+ transient amplitude and decay kinetics in the absence of any change in sarcoendoplasmic reticulum calcium transport ATPase function. Ageing maintained the integrated Ca2+ influx via ICa-L but decreased peak ICa-L . Decreased peak ICa-L was found to be responsible for the age-associated increase in SR Ca content but not the decrease in Ca2+ transient amplitude. Instead, decreased peak ICa-L offsets increased SR load such that Ca2+ release from the SR was maintained during ageing. The results of the present study highlight a novel mechanism by which increased Ca buffering decreases systolic Ca2+ in old atria. Furthermore, for the first time, we have shown that SR Ca content is increased in old atrial myocytes.

Associations of Epicardial, Abdominal, and Overall Adiposity With Atrial Fibrillation

Background—

Although adiposity is increasingly recognized as a risk factor for atrial fibrillation (AF), the importance of epicardial fat compared with other adipose tissue depots remains uncertain. We sought to characterize and compare the associations of AF with epicardial fat and measures of abdominal and overall adiposity.

Methods and Results—

We conducted a meta-analysis of 63 observational studies including 352 275 individuals, comparing AF risk for 1-SD increases in epicardial fat, waist circumference, waist/hip ratio, and body mass index. A 1-SD higher epicardial fat volume was associated with a 2.6-fold higher odds of AF (odds ratio, 2.61; 95% confidence interval [CI], 1.89–3.60), 2.1-fold higher odds of paroxysmal AF (odds ratio, 2.14; 95% CI, 1.45–3.16) and, 5.4-fold higher odds of persistent AF (odds ratio, 5.43; 95% CI, 3.24–9.12) compared with sinus rhythm. Likewise, a 1-SD higher epicardial fat volume was associated with 2.2-fold higher odds of persistent compared with paroxysmal AF (odds ratio, 2.19; 95% CI, 1.66–2.88). Similar associations existed for postablation, postoperative, and postcardioversion AF. In contrast, associations of abdominal and overall adiposity with AF were less extreme, with relative risks per 1-SD higher values of 1.32 (95% CI, 1.25–1.41) for waist circumference, 1.11 (95% CI, 1.08–1.14) for waist/hip ratio, and 1.22 (95% CI, 1.17–1.27) for body mass index.

Conclusions—

Strong and graded associations were observed between increasing epicardial fat and AF. Moreover, the strength of associations of AF with epicardial fat is greater than for measures of abdominal or overall adiposity. Further studies are needed to assess the mechanisms and clinical relevance of epicardial fat.

Relation of Pericardial Fat, Intrathoracic Fat, and Abdominal Visceral Fat With Incident Atrial Fibrillation (from the Framingham Heart Study)

Obesity is associated with increased risk of developing atrial fibrillation (AF). Different fat depots may have differential associations with cardiac pathology. We examined the longitudinal associations between pericardial, intrathoracic, and visceral fat with incident AF. We studied Framingham Heart Study Offspring and Third-Generation Cohorts who participated in the multidetector computed tomography substudy examination 1. We constructed multivariable-adjusted Cox proportional hazard models for risk of incident AF. Body mass index was included in the multivariable-adjusted model as a secondary adjustment. We included 2,135 participants (53.3% women; mean age 58.8 years). During a median follow-up of 9.7 years, we identified 162 cases of incident AF. Across the increasing tertiles of pericardial fat volume, age- and gender-adjusted incident AF rate per 1,000 person-years of follow-up were 8.4, 7.5, and 10.2. Based on an age- and gender-adjusted model, greater pericardial fat (hazard ratio [HR] 1.17, 95% confidence interval [CI] 1.03 to 1.34) and intrathoracic fat (HR 1.24, 95% CI 1.06 to 1.45) were associated with an increased risk of incident AF. The HRs (95% CI) for incident AF were 1.13 (0.99 to 1.30) for pericardial fat, 1.19 (1.01 to 1.40) for intrathoracic fat, and 1.09 (0.93 to 1.28) for abdominal visceral fat after multivariable adjustment. After additional adjustment of body mass index, none of the associations remained significant (all p >0.05). Our findings suggest that cardiac ectopic fat depots may share common risk factors with AF, which may have led to a lack of independence in the association between pericardial fat with incident AF.

Relationships between left atrial pericardial fat and permanent atrial fibrillation: Results of a case-control study

PURPOSE

The goal of this study was to retrospectively investigate the relationships between pericardial fat, left atrium volume (LAV) as measured on multidetector row computed tomography (MDCT) and persistent atrial fibrillation (AF) using a case-control study.

MATERIALS AND METHODS

The study population consisted of 58 patients (19 men, 39 women; mean age, 67.8±10 [SD] years) with persistent AF and 74 control subjects (30 men, 44 women; mean age, 67.8±10.9 [SD] years). The associations between the presence of persistent AF and periatrial pericardial fat volume (PAFV), periatrial pericardial fat thickness (PAFT), and LAV as measured on MDCT were searched for using univariate and multiple linear regression analysis.

RESULTS

On univariate analysis, significant differences were found between patients with AF and control subjects for mean PAFV (54.33cm(3)±23.43 [SD]; range: 12.2-111.1cm(3) vs 42.99cm(3)±20.76 [SD]; range: 7.4-103.9cm(3), respectively) (P=0.01), PAFT at the esophagus (1.87mm±1.65 [SD]; range: 0.1-9.5mm vs 1.12mm±0.77 [SD]; range: 0.1-3.6mm, respectively) (P<0.001) and normalized LAV (78.3cm(3)/m(2)±48.84 [SD]; range: 32.1-319.6cm(3)/m(2) vs 42.1cm(3)/m(2)±25.43 [SD]; range: 15.7-191.4cm(3)/m(2), respectively) (P<0.001). Multiple linear regression analysis revealed that only LAV was an independent predictor (P<0.001) of persistent AF. Also PAFV was significantly associated with LAV (P=0.01).

CONCLUSION

LAV is greater in patients with AF than in control subjects and PAFV is strongly associated with LAV. PAFV and PAFT are not independently associated with AF.

Relationship between epicardial adipose tissue volume and atrial fibrillation : A systematic review and meta-analysis

BACKGROUND

Several studies have suggested that epicardial adipose tissue (EAT) volume may be associated with the risk of atrial fibrillation (AF). However, these studies have reported conflicting results. We therefore aimed to investigate the relationship between EAT volume and AF.

METHODS

We systematically retrieved the relevant studies reporting on the relationship between EAT volume and AF using the Cochrane Library, PubMed, Medline, EBSCO, and Embase databases. Data were extracted from applicable articles, and mean differences were pooled using the RevMan 5.3 software.

RESULTS

Ten case-control studies were identified. With regard to the relationship between EAT volume and AF, both total-EAT volume (24.23 ml, 95 % CI: 19.40-29.06, p < 0.00001) and EAT volume surrounding the left atrium (LA-EAT; 16.35 ml, 95 %CI: 12.73-19.98, p < 0.00001) were significantly increased in patients with AF. With regard to the relationship between the different types of AF and EAT volume, there was a significant difference in the total-EAT volume subgroup (19.38 ml, 95 % CI: 11.45-27.31, p < 0.0001) and in the LA-EAT volume subgroup (17.91 ml, 95 % CI: 15.13-20.69, p < 0.00001) between patients with persistent AF (PeAF) and paroxysmal AF (PAF). However, there was no significant difference between the total-EAT and LA-EAT volume subgroups (χ (2)  = 0.12, p = 0.70).

CONCLUSION

EAT volume may be associated with an increased risk of AF. Additionally, the EAT volume in patients with PeAF was larger than that in PAF patients, independent of the location of EAT.

Monocyte-platelet aggregates and CD11b expression as markers for thrombogenicity in atrial fibrillation

BACKGROUND

A strong interdependence is known between atrial fibrillation (AF), inflammation and thrombogenesis. Monocyte-platelet aggregates (MPAs) are sensitive markers of platelets and monocyte activation. It is not known whether MPAs are associated with thrombogenicity in AF. Therefore, we examined differences in the content of MPAs and CD11b expression in patients with AF in dependence of the presence of atrial thrombus formation.

METHODS

107 patients with symptomatic AF underwent transesophageal echocardiography (TEE) before planned cardioversion or pulmonary vein isolation. Flow-cytometric quantification analysis was done on the day of performed TEE to determine the content of MPAs and the expression of CD11b on monocytes and granulocytes.

RESULTS

Compared to patients without thrombus (n = 80) those with an echocardiographic proven left atrium (LA) thrombus (n = 27) showed an increased extent of the risk factors age, diabetes and heart failure. The content of MPAs (147 ± 12 vs. 311 ± 29 cells/µl, p < 0.001) as well as the CD11b expression on monocytes (p < 0.05) and granulocytes (p < 0.05) were strongly associated with the existence of a LA thrombus. The content of MPAs and the CD11b expression remained independent predictors for LA thrombus after adjustment in logistic regression analysis and negatively correlated with left atrial appendage flow velocity. MPAs above 170 cells/µl (OR 34.2, p = 0.01) had a sensitivity of 96 % and a specificity of 73 % for predicting LA-thrombus.

CONCLUSIONS

The content of MPAs and the CD11b expression on monocytes and granulocytes are increased in AF-patients with proven thrombus formation. They seem to be appropriate biomarkers for stratification of thromboembolic risk in patients with AF.

Cardiac adipose tissue and its relationship to diabetes mellitus and cardiovascular disease

Type-2 diabetes mellitus (T2DM) plays a central role in the development of cardiovascular disease (CVD). However, its relationship to epicardial adipose tissue (EAT) and pericardial adipose tissue (PAT) in particular is important in the pathophysiology of coronary artery disease. Owing to its close proximity to the heart and coronary vasculature, EAT exerts a direct metabolic impact by secreting proinflammatory adipokines and free fatty acids, which promote CVD locally. In this review, we have discussed the relationship between T2DM and cardiac fat deposits, particularly EAT and PAT, which together exert a big impact on the cardiovascular health.

Association of epicardial and peri-atrial adiposity with the presence and severity of non-valvular atrial fibrillation

Epicardial adipose tissue (EAT), as an endocrine organ, may serve as a source of pro-inflammatory cytokines. Also, given the strong relationship between atrial fibrillation (AF), obesity and inflammation, the purpose of this study was to investigate the association of non-valvular AF with epicardial and periatrial fat. A total of 618 (192 in sinus rhythm, 169 with paroxysmal AF, 133 with persistent AF and 124 with permanent AF) patients who underwent CT angiography for the evaluation of CAD or pulmonary vein anatomy before catheter ablation were enrolled in this study. Thickness of the EAT and periatrial fat were measured by CT angiography. Together with body mass index, these were examined in relation to the presence and severity of AF and left atrial (LA) diameter. Patients with AF had significantly more total EAT and periatrial fat thickness compared with patients in sinus rhythm (p < 0.001). EAT thickness was significantly higher in permanent, persistent and paroxysmal AF compared with sinus rhythm group (p < 0.001). Multivariable multinomial logistic regression analysis comparing patients with sinus rhythm and subtypes of AF revealed a significant association between periatrial fat and total EAT thickness with all AF subtypes. Correlation analysis demonstrated that both total EAT thickness and periatrial fat thickness were significantly correlated with LA diameter (p < 0.05). Epicardial fat thickness is associated with both the presence and severity of AF independent of all other risk factors including LA diameter. Mediators for the association of EAT with AF pathophysiology requires future large scale prospective studies.

Determinants of left atrial appendage volume in stroke patients without chronic atrial fibrillation

BACKGROUND

Left atrial appendage (LAA) volume has been shown to be increased in patients with acute cryptogenic stroke. Atrial fibrillation (AF) is a well-recognized risk factor but it is not the only one associated with LAA enlargement. The aim of the study was to clarify the multifactorial etiology of LAA enlargement in cardiogenic stroke/TIA patients without AF.

METHODS

Altogether 149 patients with suspected cardioembolic stroke/TIA (47 females; mean age 61 years) underwent cardiac CT. Diagnosed AF on admittance was an exclusion criteria but 24-hour Holter ambulatory ECG revealed paroxysmal AF (PAF) in 20 patients. Body surface area adjusted LAA volume was evaluated. Eighteen different variables were registered including general characteristics, definite and potential causal risk factors for ischemic stroke/TIA, clinical echoparameters and CT based cardiac volumetric and adipose tissue measurements. A stepwise linear regression analysis was performed to achieve a model adjusted for the number of predictors of LAA volume increase.

RESULTS

In linear regression analysis, the best model accounted for 30% of the variability in LAA volume, including PAF (19%) and enlarged left atrial volume (6%), enlarged left ventricle end-systolic diameter (3%) and decreased pericardial adipose tissue (2%). No multi-colinearity between variables was observed. In addition to PAF, no other definitive or potential causal risk factors could account for the LAA volume in these patients.

CONCLUSIONS

LAA volume increase seems to be poorly associated with currently known stroke/TIA risk factors, except for AF. Targeting more comprehensive ECG monitoring for stroke patients with increased LAA volume should be considered.

Arterial stiffness, body fat compartments, central hemodynamics, renal function and left atrial size

BACKGROUND

Left atrial (LA) size is an important predictor of stroke, death, and atrial fibrillation. It was demonstrated recently that body fat, arterial stiffness and renal functions are associated with LA diameter. However, data are lacking for comprehensive assessments of all these risk factors in a single population. Therefore, the aim of the present study was to investigate the association between LA size and different fat descriptors, central hemodynamics, arterial stiffness, and renal function in healthy subjects.

METHODS

To this end, body fat percentage, abdominal, subcutaneous fat, and general descriptors of body fat were estimated in 162 healthy subjects (mean age 51 years). Echocardiography was performed to assess LA diameter. Arterial stiffness and peripheral and central hemodynamics were estimated by digital volume pulse analysis and pulse wave analysis. Glomerular filtration rate was estimated by MDRD formula.

RESULTS

There were significant (p < 0.05) bivariate correlations between LA diameter and all descriptors of body fat (except subcutaneous fat). Arterial stiffness and estimated glomerular filtration rate (eGFR) were also significantly correlated with LA size. Multiple regression analysis including all significant confounders, such as sex, mean arterial pressure, arterial stiffness, eGFR and body fat descriptors, explained 35% of variance in LA diameter.

CONCLUSIONS

In conclusion, the present study reveals significant, independent relationships between body fat, arterial stiffness, and LA size.