Epicardial adipose tissue modulates arrhythmogenesis in right ventricle outflow tract cardiomyocytes

Relationship Between Epicardial Adipose Tissue Volume and Recurrence After Ablation in Premature Ventricular Complexes

BACKGROUND

Epicardial adipose tissue (EAT) is recognized as a clinical diagnostic marker for cardiometabolic disease. Thicker EAT may be associated with recurrence of ventricular tachycardia after ablation. The association between EAT volume and recurrence of premature ventricular complexes (PVC) following ablation has not been clarified. We investigated the association between EAT volume and PVC recurrence following radiofrequency catheter ablation.

METHODS AND RESULTS

This retrospective study included 401 patients with PVC undergoing catheter ablation with preprocedural non-contrast computed tomography between 2017 and 2022. The impact of EAT volume in predicting PVC recurrence after ablation was analyzed. The mean (±SD) age of patients was 50.2±13.3 years. Multivariable Cox analysis revealed that a large EAT volume was an independent predictor of PVC recurrence after ablation during a median follow-up of 16.3 months. Kaplan-Meier analysis showed a difference in postablation PVC recurrence between the 2 groups dichotomized around the EAT volume cut-off. The risk of recurrence increased with increasing EAT volume according to restricted cubic spline regression. Furthermore, PVC originating from epicardial locations had larger EAT volumes than those originating from the right ventricular outflow tract.

CONCLUSIONS

A large EAT volume was independently associated with PVC recurrence following ablation. Patients with PVC originating from epicardial sites had large EAT volumes. EAT volume may help stratify patients according to their risk of PVC recurrence after ablation.

Atrial fibrillation in cancer, anticancer therapies, and underlying mechanisms

Atrial fibrillation (AF) is a common arrhythmic complication in cancer patients and can be exacerbated by traditional cytotoxic and targeted anticancer therapies. Increased incidence of AF in cancer patients is independent of confounding factors, including preexisting myocardial arrhythmogenic substrates, type of cancer, or cancer stage. Mechanistically, AF is characterized by fast unsynchronized atrial contractions with rapid ventricular response, which impairs ventricular filling and results in various symptoms such as fatigue, chest pain, and shortness of breath. Due to increased blood stasis, a consequence of both cancer and AF, concern for stroke increases in this patient population. To compound matters, cardiotoxic anticancer therapies themselves promote AF; thereby exacerbating AF morbidity and mortality in cancer patients. In this review, we examine the relationship between AF, cancer, and cardiotoxic anticancer therapies with a focus on the shared molecular and electrophysiological mechanisms linking these disease processes. We also explore the potential role of sodium-glucose co-transporter 2 inhibitors (SGLT2i) in the management of anticancer-therapy-induced AF.

Bariatric surgery partially reverses subclinical proarrhythmic structural, electrophysiological, and autonomic changes in obesity

BACKGROUND

Obesity confers higher risks of cardiac arrhythmias. The extent to which weight loss reverses subclinical proarrhythmic adaptations in arrhythmia-free obese individuals is unknown.

OBJECTIVE

The purpose of this study was to study structural, electrophysiological, and autonomic remodeling in arrhythmia-free obese patients and their reversibility with bariatric surgery using electrocardiographic imaging (ECGi).

METHODS

Sixteen arrhythmia-free obese patients (mean age 43 ± 12 years; 13 (81%) female participants; BMI 46.7 ± 5.5 kg/m2) had ECGi pre-bariatric surgery, of whom 12 (75%) had ECGi postsurgery (BMI 36.8 ± 6.5 kg/m2). Sixteen age- and sex-matched lean healthy individuals (mean age 42 ± 11 years; BMI 22.8 ± 2.6 kg/m2) acted as controls and had ECGi only once.

RESULTS

Obesity was associated with structural (increased epicardial fat volumes and left ventricular mass), autonomic (blunted heart rate variability), and electrophysiological (slower atrial conduction and steeper ventricular repolarization time gradients) remodeling. After bariatric surgery, there was partial structural reverse remodeling, with a reduction in epicardial fat volumes (68.7 cm3 vs 64.5 cm3; P = .0010) and left ventricular mass (33 g/m2.7 vs 25 g/m2.7; P < .0005). There was also partial electrophysiological reverse remodeling with a reduction in mean spatial ventricular repolarization gradients (26 mm/ms vs 19 mm/ms; P = .0009), although atrial activation remained prolonged. Heart rate variability, quantified by standard deviation of successive differences in R-R intervals, was also partially improved after bariatric surgery (18.7 ms vs 25.9 ms; P = .017). Computational modeling showed that presurgical obese hearts had a larger window of vulnerability to unidirectional block and had an earlier spiral-wave breakup with more complex reentry patterns than did postsurgery counterparts.

CONCLUSION

Obesity is associated with adverse electrophysiological, structural, and autonomic remodeling that is partially reversed after bariatric surgery. These data have important implications for bariatric surgery weight thresholds and weight loss strategies.

Impact of Epicardial Adipose Tissue on Right Cardiac Function and Prognosis in Pulmonary Arterial Hypertension

BACKGROUND

Although epicardial adipose tissue (EAT) is linked to effects on survival in left-sided heart failure, the association between EAT and right-sided heart failure caused by pulmonary arterial hypertension (PAH) remains unknown.

RESEARCH QUESTION

What are the potential impacts of EAT volume (EATV) on right ventricular function, biomarkers of myocardial injury, and long-term prognosis in patients with PAH?

STUDY DESIGN AND METHODS

A total of 135 age- and BMI-matched patients with PAH and 49 control participants were included in this study. EATV was quantified by using cardiac magnetic resonance and was related to clinical correlates, N-terminal pro-brain natriuretic peptide, and cardiac function. Levels of EATV associated with the risk of clinical worsening were evaluated on a continuous scale (restricted cubic splines) and by previously defined centile categories with Cox proportional hazards regression models and Kaplan-Meier survival estimates.

RESULTS

Compared with the control participants, patients with PAH had a lower EATV (ln [EATV], 3.2 ± 0.8 mL vs 3.5 ± 0.7 mL; P = .034). The association of EATV with right ventricular end-diastolic volume (Pnonlinear = .001), right ventricular end-diastolic volume index (P < .001), right ventricular cardiac output (P = .003), N-terminal pro-brain natriuretic peptide (P = .030), and the risk of clinical worsening (P = .014) was U shaped. Compared with individuals with middle-level EATV, multivariable-adjusted hazard ratio for clinical worsening was 6.0 (95% CI, 1.3-27.8) for the individuals with low-level EATV and 6.8 (95% CI, 1.5-30.2) for high-level EATV in patients with PAH.

INTERPRETATION

Patients with PAH had a decreased EATV compared with control participants. EATV exhibited a U-shaped association with right ventricular function and biomarkers of myocardial injury in patients with PAH. Low and high levels of EATV might reduce long-term event-free survival in patients with PAH.

CLINICAL TRIAL REGISTRATION

Chinese Clinical Trial Registry; No. ChiCTR2100049804; www.chictr.org.cn.

Targeting NLRP3 signaling reduces myocarditis-induced arrhythmogenesis and cardiac remodeling

BACKGROUND

Myocarditis substantially increases the risk of ventricular arrhythmia. Approximately 30% of all ventricular arrhythmia cases in patients with myocarditis originate from the right ventricular outflow tract (RVOT). However, the role of NLRP3 signaling in RVOT arrhythmogenesis remains unclear.

METHODS

Rats with myosin peptide-induced myocarditis (experimental group) were treated with an NLRP3 inhibitor (MCC950; 10 mg/kg, daily for 14 days) or left untreated. Then, they were subjected to electrocardiography and echocardiography. Ventricular tissue samples were collected from each rat's RVOT, right ventricular apex (RVA), and left ventricle (LV) and examined through conventional microelectrode and histopathologic analyses. In addition, whole-cell patch-clamp recording, confocal fluorescence microscopy, and Western blotting were performed to evaluate ionic currents, intracellular Ca2+ transients, and Ca2+-modulated protein expression in individual myocytes isolated from the RVOTs.

RESULTS

The LV ejection fraction was lower and premature ventricular contraction frequency was higher in the experimental group than in the control group (rats not exposed to myosin peptide). Myocarditis increased the infiltration of inflammatory cells into cardiac tissue and upregulated the expression of NLRP3; these observations were more prominent in the RVOT and RVA than in the LV. Furthermore, experimental rats treated with MCC950 (treatment group) improved their LV ejection fraction and reduced the frequency of premature ventricular contraction. Histopathological analysis revealed higher incidence of abnormal automaticity and pacing-induced ventricular tachycardia in the RVOTs of the experimental group than in those of the control and treatment groups. However, the incidences of these conditions in the RVA and LV were similar across the groups. The RVOT myocytes of the experimental group exhibited lower Ca2+ levels in the sarcoplasmic reticulum, smaller intracellular Ca2+ transients, lower L-type Ca2+ currents, larger late Na+ currents, larger Na+-Ca2+ exchanger currents, higher reactive oxygen species levels, and higher Ca2+/calmodulin-dependent protein kinase II levels than did those of the control and treatment groups.

CONCLUSION

Myocarditis may increase the rate of RVOT arrhythmogenesis, possibly through electrical and structural remodeling. These changes may be mitigated by inhibiting NLRP3 signaling.

Epicardial fat and ventricular arrhythmias

The arrhythmogenic role of epicardial adipose tissue (EAT) in atrial arrhythmias is well established, but its effect on ventricular arrhythmias has been significantly less investigated. Since ventricular arrhythmias are thought to cause 75%-80% of cases of sudden cardiac death, this is not a trivial issue. We provide an overview of clinical data as well as experimental and molecular data linking EAT to ventricular arrhythmias, attempting to dissect possible mechanisms and indicate future directions of research and possible clinical implications. However, despite a wealth of data indicating the role of epicardial and intramyocardial fat in the induction and propagation of ventricular arrhythmias, unfortunately there is currently no direct evidence that indeed EAT triggers arrhythmia or can be a target for antiarrhythmic strategies.

Uncovering the Role of Epicardial Adipose Tissue in Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is the most common form of heart failure. Obesity is a modifiable risk factor of HFpEF; however, body mass index provides limited information on visceral adiposity and patients with similar anthropometrics can present variable cardiovascular risk. Epicardial adipose tissue (EAT) is the closest fat deposit to the heart and has been proposed as a biomarker of visceral adiposity. EAT may be particularly important for cardiac function, because of its location (under the pericardium) and because it acts as a metabolically active endocrine organ (which can produce both beneficial and detrimental cytokines). In this paper, the authors review the role of EAT in normal and pathologic conditions and discuss the noninvasive imaging modalities that allow its identification. This review highlights EAT implications in HFpEF and discuss new therapies that act on EAT and might also exert beneficial effects on the cardiovascular system.

Electrical and Structural Insights into Right Ventricular Outflow Tract Arrhythmogenesis

The right ventricular outflow tract (RVOT) is the major origin of ventricular arrhythmias, including premature ventricular contractions, idiopathic ventricular arrhythmias, Brugada syndrome, torsade de pointes, long QT syndrome, and arrhythmogenic right ventricular cardiomyopathy. The RVOT has distinct developmental origins and cellular characteristics and a complex myocardial architecture with high shear wall stress, which may lead to its high vulnerability to arrhythmogenesis. RVOT myocytes are vulnerable to intracellular sodium and calcium overload due to calcium handling protein modulation, enhanced CaMKII activity, ryanodine receptor phosphorylation, and a higher cAMP level activated by predisposing factors or pathological conditions. A reduction in Cx43 and Scn5a expression may lead to electrical uncoupling in RVOT. The purpose of this review is to update the current understanding of the cellular and molecular mechanisms of RVOT arrhythmogenesis.

Relationship between epicardial adipose tissue measured by computed tomography and premature ventricular complexes originating from different sites

AIMS

This study aims to explore the association between the features of epicardial adipose tissue (EAT) in different zones and premature ventricular complexes (PVCs) originating from different sites by computed tomography (CT).

METHODS AND RESULTS

A total of 136 patients who underwent radiofrequency ablation for PVCs were incorporated in this study. One hundred and thirty-six matched controls were included in this study using the case-control method (1:1 matching). PVCs were classified into four subgroups: (1) right ventricular outflow tract (RVOT-PVCs), (2) non-RVOT of the right ventricle (RV-PVCs), (3) left ventricular outflow tract (LVOT-PVCs), and (4) non-LVOT of the left ventricle (LV-PVCs). The volume and density of EAT were quantified by CT. Patients with PVCs had a significantly higher volume and lower density of EAT than the controls (P < 0.001). The LVOT-PVCs and LV-PVCs had a higher left ventricle periventricular EAT volume (LV-EATv) proportion (P < 0.05). The right ventricle periventricular EAT volume (RV-EATv) proportion was higher in ROVT-PVCs and LVOT-PVCs (P < 0.05). RVOT-PVC patients had a higher volume ratio and a smaller density differential (P < 0.05). Patients with LVOT-PVCs had a lower volume ratio and the LV-PVCs showed a greater density differential (P < 0.05).

CONCLUSION

Higher volume and lower density of EAT were significantly associated with frequent PVCs. The RVOT-PVC patients had a higher volume ratio and a smaller density differential. The LVOT-PVCs had a lower volume ratio and the LV-PVCs showed a greater density differential. These suggest a link between EAT structural properties and PVCs and a potential role for regional EAT in the development of PVCs.

Prognostic value of ventricle epicardial fat volume by cardiovascular magnetic resonance in chronic heart failure

The purpose of this study is to explore the prognostic values of ventricle epicardial fat volume (EFV) calculated by cardiac magnetic resonance in patients with chronic heart failure (CHF). A total of 516 patients with CHF (left ventricular ejection fraction ≤ 50%) were recruited, and 136 (26.4%) of whom experienced major adverse cardiovascular events (MACE) within median follow-up of 24 months. The target marker-EFV was found to be associated with MACE in both univariate and multivariable analysis adjusted for various clinical variables (p < 0.01), regardless as a continuous variable and categorized by X-tile program. EFV also showed promising predictive ability, with an area under the curve of 0.612, 0.618, and 0.687 for the prediction of 1-year, 2-year, and 3-year MACE, respectively. In conclusion, EFV could be a useful prognostic marker for CHF patients, helping to identify individuals at greater risk of MACE.

Epicardial fat and atrial fibrillation: the perils of atrial failure

Obesity is a heterogeneous condition, characterized by different phenotypes and for which the classical assessment with body mass index may underestimate the real impact on cardiovascular (CV) disease burden. An epidemiological link between obesity and atrial fibrillation (AF) has been clearly demonstrated and becomes even more tight when ectopic (i.e. epicardial) fat deposition is considered. Due to anatomical and functional features, a tight paracrine cross-talk exists between epicardial adipose tissue (EAT) and myocardium, including the left atrium (LA). Alongside-and even without-mechanical atrial stretch, the dysfunctional EAT may determine a pro-inflammatory environment in the surrounding myocardial tissue. This evidence has provided a new intriguing pathophysiological link with AF, which in turn is no longer considered a single entity but rather the final stage of atrial remodelling. This maladaptive process would indeed include structural, electric, and autonomic derangement that ultimately leads to overt disease. Here, we update how dysfunctional EAT would orchestrate LA remodelling. Maladaptive changes sustained by dysfunctional EAT are driven by a pro-inflammatory and pro-fibrotic secretome that alters the sinoatrial microenvironment. Structural (e.g. fibro-fatty infiltration) and cellular (e.g. mitochondrial uncoupling, sarcoplasmic reticulum fragmentation, and cellular protein quantity/localization) changes then determine an electrophysiological remodelling that also involves the autonomic nervous system. Finally, we summarize how EAT dysfunction may fit with the standard guidelines for AF. Lastly, we focus on the potential benefit of weight loss and different classes of CV drugs on EAT dysfunction, LA remodelling, and ultimately AF onset and recurrence.

Epicardial adipose tissue as a mediator of cardiac arrhythmias

Obesity is associated with higher risks of cardiac arrhythmias. Although this may be partly explained by concurrent cardiometabolic ill-health, growing evidence suggests that increasing adiposity independently confers risk for arrhythmias. Among fat depots, epicardial adipose tissue (EAT) exhibits a proinflammatory secretome and, given the lack of fascial separation, has been implicated as a transducer of inflammation to the underlying myocardium. The present review explores the mechanisms underpinning adverse electrophysiological remodeling as a consequence of EAT accumulation and the consequent inflammation. We first describe the physiological and pathophysiological function of EAT and its unique secretome and subsequently discuss the evidence for ionic channel and connexin expression modulation as well as fibrotic remodeling induced by cytokines and free fatty acids that are secreted by EAT. Finally, we highlight how weight reduction and regression of EAT volume may cause reverse remodeling to ameliorate arrhythmic risk.