What is the normal composition of pericardial fluid?

The role of pericardial fluid biomarkers in predicting post-operative atrial fibrillation, a comprehensive review of current literature

Post-operative atrial fibrillation (POAF) is a common complication of cardiac surgery which is associated with longer hospital stay, diminished quality of life, and increased mortality. Yet, the pathophysiology of POAF is poorly understood and it is unclear which patients are at highest risk. Pericardial fluid (PCF) analysis is emerging as an important tool for the early detection of biochemical and molecular changes in the cardiac tissue. With the epicardium acting as a semi-permeable membrane, the composition of PCF reflects the activity of the cardiac interstitium. Emerging research on PCF composition has identified promising biomarkers which may help stratify the risk for developing POAF. These include inflammatory molecules, such as interleukin-6, mitochondrial deoxyribonucleic acid, and myeloperoxidase, as well as natriuretic peptides. Additionally, PCF appears to be superior to serum analysis in detecting changes in these molecules during the early postoperative period after cardiac surgery. The aim of the present narrative review is to summarize the current literature on the temporal changes in the levels of potential biomarkers in PCF after cardiac surgery and their association with the development of new-onset postoperative atrial fibrillation.

Accumulation of Inflammatory Mediators in the Normal Pericardial Fluid

There is paucity of studies that focus on the composition of pericardial fluid under resting conditions. The purpose of this study is to determine the levels of inflammatory mediators in pericardial fluid and their correlation with plasma levels in patients undergoing elective cardiac surgery. We conducted a prospective cohort study on candidates for elective aortic valve replacement surgery. Pericardial fluid and peripheral venous blood samples were collected after opening the pericardium. Levels of interleukin 1α (IL-1α); interleukin 1β (IL-1β); interleukin 2 (IL-2) interleukin 4 (IL-4); interleukin 6 (IL-6); interleukin 8 (IL8); interleukin 10 (IL10); tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), vascular endothelial growth factor (VEGF), monocyte chemotactic protein-1 (MCP-1) epidermal growth factor (EGF), soluble E-selectin, L-selectin, P-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) were determined in both pericardial fluid and serum samples. A total of 45 patients with a mean age of 74 years were included of which 66% were males. Serum levels of all study mediators were within normal limits. Serum and pericardial levels of IL-1 α, IL-1 β, IL-2, IL-4, and IL-10 were similar. Levels of VEGF, EGF, VCAM-2, ICAM 1, E-selectin, P-selectin, and L-selectin were significantly lower in pericardial fluid than in serum. However, levels of IL-6, IL-8, TNF-α, IFN-γ, MCP-1, and MCP-1 were significantly higher in the pericardial fluid than in serum. Under normal conditions, the pattern of distribution of different inflammatory mediators in the pericardial fluid does not reflect serum levels. This may either reflect the condition of the underlying myocardium and epicardial fat or the activity of the mesothelial and mononuclear cells present in pericardial fluid.

Metabolomics investigation of post-mortem human pericardial fluid

INTRODUCTION

Due to its peculiar anatomy and physiology, the pericardial fluid is a biological matrix of particular interest in the forensic field. Despite this, the available literature has mainly focused on post-mortem biochemistry and forensic toxicology, while to the best of authors' knowledge post-mortem metabolomics has never been applied. Similarly, estimation of the time since death or post-mortem interval based on pericardial fluids has still rarely been attempted.

OBJECTIVES

We applied a metabolomic approach based on 1H nuclear magnetic resonance spectroscopy to ascertain the feasibility of monitoring post-mortem metabolite changes on human pericardial fluids with the aim of building a multivariate regression model for post-mortem interval estimation.

METHODS

Pericardial fluid samples were collected in 24 consecutive judicial autopsies, in a time frame ranging from 16 to 170 h after death. The only exclusion criterion was the quantitative and/or qualitative alteration of the sample. Two different extraction protocols were applied for low molecular weight metabolites selection, namely ultrafiltration and liquid-liquid extraction. Our metabolomic approach was based on the use of 1H nuclear magnetic resonance and multivariate statistical data analysis.

RESULTS

The pericardial fluid samples treated with the two experimental protocols did not show significant differences in the distribution of the metabolites detected. A post-mortem interval estimation model based on 18 pericardial fluid samples was validated with an independent set of 6 samples, giving a prediction error of 33-34 h depending on the experimental protocol used. By narrowing the window to post-mortem intervals below 100 h, the prediction power of the model was significantly improved with an error of 13-15 h depending on the extraction protocol. Choline, glycine, ethanolamine, and hypoxanthine were the most relevant metabolites in the prediction model.

CONCLUSION

The present study, although preliminary, shows that PF samples collected from a real forensic scenario represent a biofluid of interest for post-mortem metabolomics, with particular regard to the estimation of the time since death.

Pericardial Effusion and Cardiac Tamponade Pathophysiology and New Approaches to Treatment

PURPOSE OF REVIEW

The objective of this manuscript is to examine up-to-date approaches to the diagnosis and treatment of pericardial effusions and cardiac tamponade.

RECENT FINDINGS

Recent recommendations from the American Society of Echocardiography and the European Society of Cardiology have improved our management of the patient with pericardial effusion and cardiac tamponade, but significant knowledge gaps remain. Novel diagnostic and triage strategies have been suggested, and recent information have improved our facility to assess the presence and size of a pericardial effusion, assess its hemodynamic impact, and determine its cause. Despite these recent findings, there is a scarcity of evidence-based data to direct the management of pericardial effusion and cardiac tamponade. While the first-line function of echocardiography in managing these disorders is undisputed, there are increasingly niche functions for multimodality imaging.

Chronic Pericardial Effusion: Causes and Management

Chronic pericardial effusion is a common pericardial syndrome whose approach has been well standardised in recent years. The main challenge associated with this condition is the progression (sometimes unheralded) to cardiac tamponade. Pericardial effusions may present either as an isolated finding or in the context of a specific etiology including autoimmune, neoplastic, or metabolic disease. Among investigations used during diagnostic work-up, echocardiography is of paramount importance for the diagnosis, sizing, and serial evaluation of the hemodynamic impact of effusions on heart diastolic function. In an individualised manner, advanced imaging including computed tomography and cardiac magnetic resonance imaging should be performed, especially if baseline tests are inconclusive. Triage of these patients according to the most recent 2015 European Society of Cardiology Guidelines for the diagnosis and management of pericardial diseases should take into account the presence of hemodynamic compromise as well as suspicion of malignant or purulent pericarditis as first step, C-reactive protein serum level measurement as second step, investigations for a specific condition known to be associated with pericardial effusion as third step, and finally the size and the duration of the effusion. Treatment depends on the evaluation of the above-mentioned parameters and should ideally be tailored to the individual patient. Prognosis of chronic pericardial effusions depends largely on the underlying etiology. According to novel data, the prognosis of individuals with idiopathic, chronic (> 3 months), large (> 2 cm), asymptomatic pericardial effusions is usually benign and a watchful waiting strategy seems more reasonable and cost-effective than routine drainage as previously recommended.

New Developments in the Management of Recurrent Pericarditis

Recurrent pericarditis is a common and troublesome complication that affects 15%-30% of patients with a previous episode of pericarditis. However, the pathogenesis of these recurrences is not well understood, and most cases remain idiopathic. Recent advances in medical therapy, including the use of colchicine and anti-interleukin-1 agents like anakinra and rilonacept, have suggested an autoinflammatory rather than an autoimmune mechanism for recurrences with an inflammatory phenotype. As a result, a more personalized approach to treatment is now recommended. Patients with an inflammatory phenotype (fever and elevated C-reactive protein level) should receive colchicine and anti-interleukin-1 agents as first-line therapy, whereas those without systemic inflammation should receive low to moderate doses of corticosteroids (eg, prednisone 0.2-0.5 mg/kg/d as an initial dose) and consider azathioprine and intravenous human immunoglobulins in the case of corticosteroid failure. Tapering of corticosteroids should be slow after achieving clinical remission. In this article, we review the new developments in the management of recurrent pericarditis.

Pericardial Immune Cells and Their Evolving Role in Cardiovascular Pathophysiology

The pericardium plays several homeostatic roles to support and maintain everyday cardiac function. Recent advances in techniques and experimental models have allowed for further exploration into the cellular contents of the pericardium itself. Of particular interest are the various immune cell populations present in the space within the pericardial fluid and fat. In contrast to immune cells of the comparable pleura, peritoneum and heart, pericardial immune cells appear to be distinct in their function and phenotype. Specifically, recent work has suggested these cells play critical roles in an array of pathophysiological conditions including myocardial infarction, pericarditis, and post-cardiac surgery complications. In this review, we spotlight the pericardial immune cells currently identified in mice and humans, the pathophysiological role of these cells, and the clinical significance of the immunocardiology axis in cardiovascular health.

Cardiac tamponade

Cardiac tamponade is a medical emergency caused by the progressive accumulation of pericardial fluid (effusion), blood, pus or air in the pericardium, compressing the heart chambers and leading to haemodynamic compromise, circulatory shock, cardiac arrest and death. Pericardial diseases of any aetiology as well as complications of interventional and surgical procedures or chest trauma can cause cardiac tamponade. Tamponade can be precipitated in patients with pericardial effusion by dehydration or exposure to certain medications, particularly vasodilators or intravenous diuretics. Key clinical findings in patients with cardiac tamponade are hypotension, increased jugular venous pressure and distant heart sounds (Beck triad). Dyspnoea can progress to orthopnoea (with no rales on lung auscultation) accompanied by weakness, fatigue, tachycardia and oliguria. In tamponade caused by acute pericarditis, the patient can experience fever and typical chest pain increasing on inspiration and radiating to the trapezius ridge. Generally, cardiac tamponade is a clinical diagnosis that can be confirmed using various imaging modalities, principally echocardiography. Cardiac tamponade is preferably resolved by echocardiography-guided pericardiocentesis. In patients who have recently undergone cardiac surgery and in those with neoplastic infiltration, effusive-constrictive pericarditis, or loculated effusions, fluoroscopic guidance can increase the feasibility and safety of the procedure. Surgical management is indicated in patients with aortic dissection, chest trauma, bleeding or purulent infection that cannot be controlled percutaneously. After pericardiocentesis or pericardiotomy, NSAIDs and colchicine can be considered to prevent recurrence and effusive-constrictive pericarditis.

Causes of Polyserositis: A Systematic Review

At present, polyserositis (PS) remains a challenging entity, which resides both in the fact that there is confusion regarding the terminology, and that it is still understudied. We aimed to identify the etiologies of PS, reported in adult patients.

METHODS

We performed a systematic review of the literature on PubMed(MEDLINE) database, using the following (MESH) terms: pleurisy/etiology, pleural effusion/etiology, pericarditis/etiology, pericardial effusion/etiology, pericardial effusion chronic, ascites/etiology, ascitic fluid/etiology, polyserositis, serositis, and serositides.

RESULTS

A total of 1979 articles were identified, dating from 1973 onwards. After screening the articles, we included 114 patients from 23 articles (one case series including 92 patients and 22 case reports) in the final report. The most common diagnosis was neoplasia (30; 26.3%), followed by autoimmune diseases (19, 16.7%) and infections (16, 12.3%). Still, in 35 cases, the etiology of PS remained unkown.

CONCLUSION

PS is a challenging and understudied entity, which is associated with a wide range of diagnoses. However, prospective studies should be developed in order to have a clear understanding regarding its etiologies and their prevalences.

Metabolic signatures in pericardial fluid and serum are associated with new-onset atrial fibrillation after isolated coronary artery bypass grafting

Postoperative atrial fibrillation (POAF) is a common complication of coronary artery bypass grafting (CABG) procedures. However, the molecular mechanism of POAF remains poorly understood, hence the absence of effective prevention strategies. Here we used targeted metabolomics on pericardial fluid and serum samples from CABG patients to investigate POAF-associated metabolic alterations and related risk prediction of new-onset AF. Nine differential metabolites in various metabolic pathways were found in both pericardial fluid and serum samples from patients with POAF and without POAF. By using machine learning algorithms and regression models, a 4-metabolite (aceglutamide, ornithine, methionine, and arginine) risk prediction model was constructed and showed accurate performance in predicting POAF in both discovery and validation sets. This work extends the metabolic insights of the cardiac microenvironment and blood in patients with POAF and paves the way for the use of targeted metabolomics for predicting POAF in patients with CABG surgery.

Chronic pericardial effusion: current concepts and emerging trends

INTRODUCTION

Pericardial effusion (PEF) is a common and challenging pericardial syndrome with a variety of clinical manifestations ranging from asymptomatic, incidentally uncovered small PEFs, to life-threatening cardiac tamponade.

AREAS COVERED

: This review focuses on the pathophysiology, epidemiology, etiology, classification, clinical findings, diagnostic work-up, management and outcome of PEFs. Particular emphasis has been given on the most recent evidence concerning the contribution of imaging for the detection, differential diagnosis and evaluation of the hemodynamic impact of PEFs on the diastolic filling of the heart. Moreover, simplified algorithms for PEF triage and management have been included.

EXPERT OPINION

The management of patients with PEFs is mainly based on four parameters namely hemodynamic impact on diastolic function, elevation of inflammatory markers, presence of a specific underlying condition known to be associated with PEF and finally size and duration of the effusion. Novel data have contributed to change our view towards large, asymptomatic, "idiopathic" PEFs and dictated a rather conservative approach in most cases. It is also stressed that there is a compelling need for additional research, which is essential for tailored treatments aiming at the improvement of quality of life and containment of health care costs.

Immunomodulating Therapies in Acute Myocarditis and Recurrent/Acute Pericarditis

The field of inflammatory disease of the heart or "cardio-immunology" is rapidly evolving due to the wider use of non-invasive diagnostic tools able to detect and monitor myocardial inflammation. In acute myocarditis, recent data on the use of immunomodulating therapies have been reported both in the setting of systemic autoimmune disorders and in the setting of isolated forms, especially in patients with specific histology (e.g., eosinophilic myocarditis) or with an arrhythmicburden. A role for immunosuppressive therapies has been also shown in severe cases of coronavirus disease 2019 (COVID-19), a condition that can be associated with cardiac injury and acute myocarditis. Furthermore, ongoing clinical trials are assessing the role of high dosage methylprednisolone in the context of acute myocarditis complicated by heart failure or fulminant presentation or the role of anakinra to treat patients with acute myocarditis excluding patients with hemodynamically unstable conditions. In addition, the explosion of immune-mediated therapies in oncology has introduced new pathophysiological entities, such as immune-checkpoint inhibitor-associated myocarditis and new basic research models to understand the interaction between the cardiac and immune systems. Here we provide a broad overview of evolving areas in cardio-immunology. We summarize the use of new imaging tools in combination with endomyocardial biopsy and laboratory parameters such as high sensitivity troponin to monitor the response to immunomodulating therapies based on recent evidence and clinical experience. Concerning pericarditis, the normal composition of pericardial fluid has been recently elucidated, allowing to assess the actual presence of inflammation; indeed, normal pericardial fluid is rich in nucleated cells, protein, albumin, LDH, at levels consistent with inflammatory exudates in other biological fluids. Importantly, recent findings showed how innate immunity plays a pivotal role in the pathogenesis of recurrent pericarditis with raised C-reactive protein, with inflammasome and IL-1 overproduction as drivers for systemic inflammatory response. In the era of tailored medicine, anti-IL-1 agents such as anakinra and rilonacept have been demonstrated highly effective in patients with recurrent pericarditis associated with an inflammatory phenotype.

Pericarditis and pericardial effusion: one or two distinct diseases?

The main pericardial syndromes include acute and recurrent pericarditis, constrictive pericarditis and chronic pericardial effusion in the absence of overt inflammation. Despite recent advances in pericardial syndromes, certain clinical scenarios depict remarkable peculiarities and their management is often challenging for the clinician. Acute pericarditis is the most common pericardial disease and in most instances is accompanied by pericardial effusion. On the other hand, pericardial effusion may appear as a separate clinical entity occasionally characterized by absence of inflammatory markers elevation. In cases that effusions are accompanied by C-reactive protein (CRP) elevation, the administration of empiric anti-inflammatory treatment as in acute pericarditis, is the guidelines recommended approach. Conversely, the optimal management of patients with pericardial effusions in the absence of clinical or subclinical inflammation (as depicted by CRP levels and cardiac magnetic resonance findings), is not supported by solid evidence. Patients with chronic pericardial effusions should be followed in specialized centers according to tailored timelines, based on the specific clinical scenarios which should take into account etiology, effusion size, disease duration and stability as regards symptoms and effusion volume. Patients should also be advised to seek medical care at any time if symptoms like chest pain, dyspnea and fatigue should appear.

New Approaches to Management of Pericardial Effusions

Purpose of Review

Pericardial effusion is a challenging pericardial syndrome and a cause of serious concern for physicians and patients due to its potential progression to life-threatening cardiac tamponade. In this review, we summarize the contemporary evidence of the etiology; diagnostic work-up, with particular emphasis on the contribution of multimodality imaging; therapeutic options; and short- and long-term outcomes of these patients.

Recent Findings

In recent years, an important piece of information has contributed to put together several missing parts of the puzzle of pericardial effusion. The most recent 2015 guidelines of the European Society of Cardiology for the diagnosis and management of pericardial diseases are a valuable aid for a tailored approach to this condition. Actually, current guidelines suggest a 4-step treatment algorithm depending on the presence or absence of hemodynamic impairment; the elevation of inflammatory markers; the presence of a known or first-diagnosed underlying condition, possibly related to pericardial effusion; and finally the duration and size of the effusion. In contrast to earlier perceptions, based on the most recent evidence, it seems that in the subgroup of asymptomatic patients with large (> 2-cm end-diastolic diameter), chronic (> 3 months) C-reactive protein negative, idiopathic (without an apparent cause) pericardial effusion, a conservative approach is the most reasonable option.

Summary

At present there is an increasing interest in the pericardial syndromes in general and pericardial effusions in specific, which has consistently expanded our knowledge in this “hazy landscape.” Apart from general recommendations applied to all cases, an individualized, etiologically driven treatment is of paramount importance.

Isolation and Multiple Differentiation of Rat Pericardial Fluid Cells

Objective

The aim of the present study is to isolate and analyze the characterization of pericardial fluid cells (PFCs) from rat and provides a morphological basis for the basic research and clinical application of PFCs.

Methods

After aseptic thoracotomy was performed, normal saline was injected into the pericardial cavity of 50 adult Sprague–Dawley rats. The mixture of diluted pericardial fluid was extracted, centrifuged, and cultured. The cell morphology of different generations in the pericardial fluid was observed on an inverted microscope. The expression levels of CD44, CD29, CD90, and pan-hematopoietic marker CD45 were analyzed via flow cytometry. The third-generation cells were used for osteogenic, adipogenic, and cardiac differentiation.

Results

PFCs were successfully isolated and subcultured. PFCs were predominantly circular in shape after 24 h of culture. Following subculture for 3 days, the cells demonstrated a spindle shape. The rat pericardial fluid contains cell populations with uniform morphology, good growth state, and strong proliferation ability. Flow cytometry results showed that CD29 (100%) and CD90 (99.3%) were positively expressed, whereas CD45 (0.30%) and CD44 (0.48%) were negatively expressed. The PFCs could differentiate into osteoblasts and adipocytes after being induced. Cardiac differentiation was also confirmed by cardiac troponin T (cTnT) and α-sarcomeric actin (α-SA) staining.

Conclusion

This study revealed that a subpopulation of cells was isolated from pericardial fluid, which exhibited progenitor cell features and multiple differentiation potency. PFCs could serve as an alternative cell source for myocardial tissue repair, engineering, and reconstruction.