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• Early EMB is associated with a higher rate of survival free of HTx/LVAD at one year compared with delayed EMB. [ABSTRACT FROM AUTHOR]

• This patient developed severe, lethal cardiogenic shock. • In postmortem analysis, infiltration of giant cells and lymphocytes into both the myocardium and skeletal muscles was documented; therefore, the patient was diagnosed with giant cell myocarditis with polymyositis. • Giant cell myocarditis with polymyositis is typically associated with thymoma and myasthenia gravis; however, in this case, it was not associated with thymoma, and infiltration of giant cells into both cardiac and skeletal muscle is infrequent. [ABSTRACT FROM AUTHOR]

Abstract Background/Objective To examine tenascin C (TN-C) expression in coronary artery lesions (CALs) and myocardial lesions (MLs) in Kawasaki disease (KD). Methods and Results Twenty-five KD autopsy cases (post-KD-onset range of 6 days to 17 years) were examined in this study. Time-course analysis based on the disease day was performed of the histological findings for the CALs and MLs, as well as the localization and intensity of expression of TN-C. TN-C expression was observed to coincide with the areas where inflammatory cell infiltration was present in both coronary arteries and myocardium during the acute stage of KD, and the intensity of its expression correlated with the degree of inflammation. Obvious TN-C expression persisted in the thickened intima and media of CALs even after Disease Day 27. However, in spite of the presence of inflammatory cell infiltration, TN-C expression became weaker in the adventitia and surrounding connective tissue. After 8 months or more, TN-C was not expressed in the vasculitis scars of most cases, but expression was observed around newly formed vessels in the thickened intima and around recanalized vessels after thrombotic occlusion. Conclusions The findings suggest a correlation between the degree of inflammation and TN-C expression in the cardiovascular lesions of acute–stage Kawasaki disease. Highlights • Serum TN-C is a useful predictor of cardiovascular lesion in acute Kawasaki disease. • TN-C expression in cardiovascular lesions was examined immunohistochemically. • TN-C expression coincided with the area of acute inflammation in cardiovascular system. • Elevation of serum TN-C originates in acute vascular injury in Kawasaki disease. [ABSTRACT FROM AUTHOR]

Abstract Vaccine-associated myocarditis is an extremely rare, yet potentially lethal disease, which requires early diagnosis and prompt treatment. However, its pathogenesis remains elusive. We report the first case of biopsy-proven eosinophilic myocarditis related to tetanus toxoid immunization, with unique histopathologic findings, characterized by perivascular eosinophilic infiltrates with myocyte necrosis and abundant interstitial lymphocytic infiltrates with myocyte necrosis, separately. A systemic high-dose corticosteroid treatment had a dramatic beneficial effect on hemodynamic instability and resulted in complete recovery. This case highlights the value of endomyocardial biopsy in establishing a definite diagnosis and understanding the pathogenesis of vaccine-associated myocarditis. Highlights • Acute eosinophilic myocarditis may be induced by tetanus toxoid immunization. • An endomyocardial biopsy is critical for early diagnosis and prompt treatment. • The clinical significance of vaccine-associated myocarditis should be recognized. [ABSTRACT FROM AUTHOR]

• Histological examination of endomyocardial biopsy or myocardium at autopsy is key to the diagnosis of myocarditis. • There is currently extensive variability in criteria used by pathologists to diagnose myocarditis. • It is difficult to achieve a consensus diagnosis of myocarditis, even amongst experienced cardiovascular pathologists. Histological examination of endomyocardial biopsy or myocardium at autopsy is key to the diagnosis of myocarditis. Among pathologists there is currently extensive variability in routine practice and criteria used to define, diagnose, and report myocarditis as well as to achieve consensus on cases. Two manuscripts emphasizing the need to standardize and implement histopathological diagnostic criteria for myocarditis are reviewed. [ABSTRACT FROM AUTHOR]

• Pathologists worldwide report various biopsy practice of myocarditis diagnosis. • There are regional differences in adopting diagnostic criteria and ancillary testing. • Non-uniformity in current criteria hinders comparative and multicenter studies. Dallas criteria (DC) and European Society of Cardiology criteria (ESCC) have provided valuable frameworks for the histologic diagnosis and classification of myocarditis in endomyocardial biopsy (EMB) specimens. However, the adaptation and the usage of these criteria are variable and depend on local practice settings and regions/countries. Moreover, several ancillary tests that are not included in the current criteria, such as immunohistochemistry (IHC) or viral polymerase chain reaction (PCR), have proven useful for the diagnosis of myocarditis. As a joint effort from the Association for European Cardiovascular Pathology (AECVP) and the Society for Cardiovascular Pathology (SCVP), we conducted an online survey to understand the current practice of diagnosing myocarditis. A total of 100 pathologists from 23 countries responded to the survey with the majority practicing in North America (45%) and Europe (45%). Most of the pathologists reported to examine less than 200 native heart biopsies per year (85%), and to routinely receive 3-5 fragments of tissue per case (90%). The number of hematoxylin-eosin-stained levels for each case varies from 1 to more than 9 levels, with 20% of pathologists routinely asking for more than 9 levels per case. Among the 100 pathologists, 52 reported to use the DC alone, 12 the ESCC alone, 28 both DC and ESCC and 8 reported to use neither the DC nor the ESCC. Overall, 80 pathologists reported to use the DC and 40 the ESCC. Use of DC alone is more common among North American pathologists compared to European ones (80% vs 32.6%) while use of ESCC alone is more common in Europe (20.9% vs 2.5%). IHC is utilized in either every case or selected cases by 79% of participants, and viral PCR is performed by 35% of participants. Variable terminologies are used in reporting, including both histological and clinical terms. The diagnosis of myocarditis is rendered even in the absence of myocyte injury (e.g., in cases of borderline or inactive/chronic myocarditis) by 46% respondents. The majority of the participants think it is time to update the current criteria (83%). The survey data demonstrated that pathologists who render a myocarditis diagnosis practice with variable tissue preparation methods, use of ancillary studies, guideline usage, and reporting. This result highlights the clinically unmet need to update and standardize the current diagnostic criteria for myocarditis on EMB. Additional studies are warranted to establish standard of practice. [ABSTRACT FROM AUTHOR]

• One hundred digital cases were evaluated by cardiovascular pathologists • Consensus was achieved on 90 cases • Subtle forms of myocarditis are challenging to diagnose The two histopathology benchmarks used to diagnose myocarditis are the Dallas Criteria, developed in 1984 and the European Society of Cardiology criteria, developed in 2013, which added immunohistochemistry for the detection of CD3+ T cells (lymphocytes) and CD68+ macrophages. Despite their near universal acceptance, the extent to which pathologists use these criteria or their own criteria to consistently render the diagnosis of myocarditis on endomyocardial biopsy (EMB) is unknown. We digitally scanned slides from 100 heart biopsies, including a trichrome stain and immunostaining, that were chosen as representative of myocarditis, non-myocarditis, and borderline myocarditis, as diagnosed per one institution's use of the Dallas Criteria. Eight blinded international cardiovascular experts were asked to render diagnoses and offer a confidence score on each case. No clinical histories were shared. There was full initial agreement across all experts on 37 cases (16 myocarditis and 21 non-myocarditis) and moderate consensus on 35 cases. After individual inquiries and group discussion, consensus was reached on 90 cases. Diagnostic confidence was highest among the myocarditis diagnoses, lowest for borderline cases, and significantly different between the three diagnostic categories (myocarditis, borderline myocarditis, non-myocarditis; P -value=8.49 × 10−57; ANOVA). Diagnosing myocarditis, particularly in cases with limited inflammation and injury, remains a challenge even for experts in the field. Intermediate cases, termed "borderline" in the Dallas Criteria, represent those for which consensus is particularly hard to achieve. To increase consistency for the histopathologic diagnosis of myocarditis, we will need more specifically defined criteria, more granular descriptions of positive and negative features, clarity on how to incorporate immunohistochemistry findings, and improved nomenclature. [ABSTRACT FROM AUTHOR]

Diagnosis of myocarditis as the cause of death in the forensic setting at post-mortem is currently determined by a forensic pathologist. There is no systematic method for diagnosis and thus the determination is subject to inter-observer variability and is often non-reproducible. The primary aim of this study was to investigate the differences in the amount of inflammation between cases where myocarditis was deemed the cause of death, compared to cases where myocardial inflammation was incidentally present at autopsy, but not determined to be the cause of death. Participants were sourced from the Victorian Institute of Forensic Medicine (VIFM) database, from full autopsies conducted on reportable death in Victoria, Australia between the years 2011 and 2021. Cases of fatal myocarditis were significantly more likely to experience infection-like symptoms prior to death, and to be in hospital at the time of death. Histopathological examination revealed fatal cases had a significantly higher inflammatory index compared to the incidental group. Lethal cases were also significantly more likely to have myocyte necrosis, and a diffuse pattern of inflammation. There are significant differences between cases where myocardial inflammation has been determined to be the cause of death and cases where inflammation in the myocardium was an incidental finding. These results could be used in the forensic autopsy to help pathologists determine if inflammation should be considered fatal or incidental. [ABSTRACT FROM AUTHOR]

• There is no current reproducible method for diagnosis of myocarditis in the post-mortem setting, it is up to the forensic pathologist • There is no system to determine whether inflammation in the heart was the cause of death, or an incidental finding at autopsy. • Variables to distinguish between fatal and incidental myocarditis have not been widely researched and requires further investigation Diagnosis of myocarditis as the cause of death at post-mortem is currently determined by a forensic pathologist. There is no systematic method for diagnosis and thus the determination is subject to inter-observer variability and is non-reproducible. Postmortem studies often rely on the clinical method of diagnosis, which is inaccurate. Furthermore, there is no current standardized method of distinguishing between myocarditis as cause of death, and myocardial inflammation as an incidental finding post-mortem. Only a few studies have investigated a method of quantifying this difference using variables such as number of inflammatory cells and presence of myocyte necrosis, however, there are several limitations hindering the reproducibility of this research. This review investigates the current practices and limitations associated with the diagnosis of myocarditis as cause of death in the autopsy setting [ABSTRACT FROM AUTHOR]

Although dilated cardiomyopathy (DCM) is often caused by viral infections, it frequently involves autoimmune mechanisms associated with particular HLA-DR and DQ alleles. Our homozygous HLA-DQ8Ab 0 transgenic mice in the BALB/c background (HLA-DQ8 BALB/c -Tg) developed early and progressive fatal heart failure from 4 to 5 weeks of age. Clinical signs of the disease included cyanotic eyes, tachycardia with dyspnea (from pale to cyanotic limbs), and terminal whole body edema. Sick mice had extremely dilated hearts, enlarged liver and spleen, and pleural/peritoneal effusion. Histology of the heart showed extensive heart muscle destruction with signs of fibrosis. The autoimmune nature of the disease was shown by high titers of antimyosin antibodies in the sera and IgG deposits in sick heart muscles, as well as focal neutrophil, T cell, and macrophage infiltration of the heart muscle. The sera of the sick mice showed a granular staining pattern on sections of healthy heart muscle. Quantitative analyses of DCM-specific gene expression studies revealed that sets of genes are involved in inflammation, hypoxia, and fibrosis. Treatment with FTY720 (Fingolimod/Gilenya) protected animals from the development of cardiomyopathy. HLA-DQ8 BALB/c -Tg mice represent a spontaneous autoimmune myocarditis model that may provide a useful tool for studying the autoimmune mechanism of DCM and testing immunosuppressive drugs. [ABSTRACT FROM AUTHOR]

• The histologic diagnosis of myocarditis warrants revisiting in light of questions raised preceding and during the pandemic. • Interobserver variability remains high, with divergent practices in different regions of the world. • The diagnosis and implications of myocarditis are reviewed in conjunction with two relevant articles. The histologic criteria for myocarditis are a focal point of scientific debate in the wake of the SARS-CoV-2 pandemic. Variable methodologies have evolved in an evaluation already plagued by high intraobserver variability and low sensitivity. In this commentary, two topical manuscripts are reviewed in the context of this unfolding discussion. [ABSTRACT FROM AUTHOR]

Highlights • Tuberculous myocarditis is a very rare entity with only a few reported cases in literature. • The patient may suffer a sudden death and the disease is usually diagnosed at autopsy. • The incidence of myocarditis has been difficult to study because clinical presentation of disease vary widely ranging from asymptomatic to sudden cardiac death and histopathological examination of the heart is needed to confirm the diagnosis. • If the clinical suspicion is strong and the adjunctive imaging, such as a serial late gadolinium enhanced cardiac magnetic resonance imaging, is suggestive, an early endomyocardial biopsy is indicated, wherever possible. [ABSTRACT FROM AUTHOR]

• Single myocyte necrosis is a relatively specific finding in Covid-19 decedents. • Epicardial macrophages are elevated in the setting of single myocyte necrosis. • Epicardial and myocardial macrophages are increased in Covid-19 decedents' hearts. SARS-Cov-2 infection is not limited to the respiratory tract and can involve other organs including the heart, blood vessels, kidneys, liver, gastrointestinal tract, placenta, and skin. Covid-19 patients with cardiac involvement usually have higher morbidity and mortality compared to those without cardiac involvement. The frequency and the specificity of the myocardial pathological changes in patients who die after documented infection with SARS-Cov-2 is uncertain. Macrophages can be found in the normal heart (interstitium, around the endothelial cells and in the epicardial adipose tissue), and they are considered part of the major immune cell population in the heart. In this case-control autopsy study, we compare the gross and microscopic cardiac findings, and the available clinical characteristics between a group of 10 Covid-19 decedents and a control group of 20 patients who died with non-SARS-Cov-2 severe bronchopneumonia and/or diffuse alveolar damage. The objectives of this semi-quantitative study are to study single myocyte necrosis and its relation to the strain on the heart caused by lung injury as a causative mechanism, and to study the density of myocardial and epicardial macrophages in Covid-19 hearts in comparison to the control group, and in Covid-19 hearts with single myocyte necrosis in comparison to Covid-19 hearts without single myocyte necrosis. Lymphocytic myocarditis was not identified in any of the hearts from the Covid-19 or the control group. Single myocyte necrosis is more frequent in the Covid-19 group compared to the control group, suggesting that it is unrelated to the strain on the heart caused by underlying lung injury. The density of the macrophages in the epicardium and myocardium in the hearts of the Covid-19 group is higher compared to those in the control group. The density of epicardial macrophages is higher in the Covid-19 hearts with single myocyte necrosis than in those without. These observations contribute to our increasing appreciation of the role of macrophages in the pathophysiologic response to infection by SARS-CoV-2. [ABSTRACT FROM AUTHOR]

• Mechanisms of myocardial injury as a complication of COVID-19 have not been well understood. • We experienced a case with cardiogenic shock infected by COVID-19. • With endomyocardial biopsy, there was no sign of typical active myocarditis. • Ischemic changes were found at microvascular level accompanied by microthrombi. • Microvascular thrombotic injury is shown as a cause of fulminant myocarditis-like presentation. Myocardial injury has been reported as a complication of COVID-19. Although several mechanisms have been proposed as its cause, they are mostly based on autopsy studies, We report a 49-year-old male with COVID-19-associated myocardial injury presented like fulminant myocarditis. We performed endomyocardial biopsy on day 2 and we confirmed the presence of microthrombosis histologically. He died on day 5 due to cardiogenic shock. [ABSTRACT FROM AUTHOR]

Introduction Atrial fibrillation (AF) is a common complication in myocarditis. Atrial inflammation has been suggested to play an important role in the pathophysiology of AF. However, little is known about the occurrence of atrial inflammation in myocarditis patients. Here, we analyzed inflammatory cell numbers in the atria of myocarditis patients without symptomatic AF. Methods Cardiac tissue was obtained postmortem from lymphocytic myocarditis patients ( n = 6), catecholamine-induced myocarditis patients ( n = 5), and control patients without pathological evidence of heart disease ( n = 5). Tissue sections of left and right ventricle and left and right atrium were stained for myeloperoxidase (neutrophilic granulocytes), CD45 (lymphocytes), and CD68 (macrophages). These cells were subsequently quantified in atrial and ventricular myocardium and atrial adipose tissue. Results In lymphocytic myocarditis patients, a significant increase was observed for lymphocytes in the left atrial adipose tissue. In catecholamine-induced myocarditis patients, significant increases were found in the atria for all three inflammatory cell types. Infiltrating inflammatory cell numbers in the atrial myocardium correlated positively with those in the ventricles, especially in catecholamine-induced myocarditis patients. Conclusions To a varying extent, atrial myocarditis occurs concurrently with ventricular myocarditis in patients diagnosed with myocarditis of different etiology. This provides a substrate that potentially predisposes myocarditis patients to the development of AF and subsequent complications such as sudden cardiac death and heart failure. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are a group of short, noncoding, regulatory RNA molecules the dysregulation of which contributes to the pathogenesis of myocarditis. Argonaute proteins are essential components of miRNA-induced silencing complex and play important roles during miRNA biogenesis and function. However, the expression pattern of four AGO family members has not yet been detected in the coxsackievirus B3 (CVB3)-induced myocarditis tissue samples. In this study, we detected the expression of four AGOs in the CVB3-infected mouse heart tissues and found that AGO1 and AGO3 up-regulated significantly at 4 and 8 h after CVB3 infection. Further in vitro research indicated that up-regulated AGO1 and AGO3 are related to the down-regulated TNFAIP3, which is a negative regulator of NF-κB pathway. Subsequently, we confirmed that TNFAIP3 is a direct target of miR-19a/b, and during CVB3 infection, the expression of miR-19a/b and miR-125a/b is not significantly changed. TNFAIP3 level is mainly reduced by up-regulated AGO1 and AGO3. This research sheds light on the relationship between overexpressed AGO proteins and CVB3-induced myocarditis, and this provides potential therapeutic target for viral myocarditis. [ABSTRACT FROM AUTHOR]

Although the clinical presentation of myocarditis is very diverse, ranging from mild dyspnea to hemodynamic collapse, myocarditis accompanied with extracardiac myositis is extremely rare. We report a single case of fulminant myocarditis associated with orbital myositis and diaphragmatic paralysis in a 40-year-old man, which was successfully managed by immunosuppressive therapy with steroid. [ABSTRACT FROM AUTHOR]

Lyme disease is a systemic infection commonly found in the northeastern, mid-Atlantic, and north–central regions of the United States. Of the many systemic manifestations of Lyme disease, cardiac involvement is uncommon and rarely causes mortality. We describe a case of a 17-year-old adolescent who died unexpectedly after a 3-week viral-like syndrome. Postmortem examination was remarkable for diffuse pancarditis characterized by extensive infiltrates of lymphocytes and focal interstitial fibrosis. In the cardiac tissue, Borrelia burgdorferi was identified via special stains, immunohistochemistry, and polymerase chain reaction. The findings support B. burgdorferi as the causative agent for his fulminant carditis and that the patient suffered fatal Lyme carditis. Usually, Lyme carditis is associated with conduction disturbances and is a treatable condition. Nevertheless, few cases of mortality have been reported in the literature. Here, we report a rare example of fatal Lyme carditis in an unsuspected patient. [ABSTRACT FROM AUTHOR]

Opportunistic infections cause significant morbidity and mortality in patients infected with the human immunodeficiency virus (HIV). Multiple opportunistic infections can occur in a patient in the setting of severe immunodeficiency and can have atypical clinicoradiological presentation. Cardiac involvement has also been observed on autopsy in HIV-infected patients in the form of myocarditis, dilated cardiomyopathy, endocarditis, neoplasms, and drug-related cardiotoxicity. Mostly, the cardiac opportunistic infections are clinically asymptomatic, and sudden death due to these is extremely rare. We report a case of 44-year-old gentleman who presented with cough, pleuritic chest pain, and breathlessness and died of refractory shock due to myocarditis. At autopsy, he was found to have Toxoplasma myocarditis, Pneumocystis jirovecii pneumonia, and cytomegalovirus adrenalitis. [ABSTRACT FROM AUTHOR]

• Endomyocardial biopsy results are integral for diagnosis and management of myocarditis. Current diagnostic classifications of myocarditis are based on the microscopic and immunochemical characterization of inflammation do not include monocyte/macrophage-predominant (i.e. "histiocytic") myocarditis as a histologic subtype. We describe 6 cases of patients with acute heart failure whose endomyocardial biopsies showed predominant inflammation with macrophages and monocytes identified by immunopositivity for CD68. • Our cases were both cardiac limited (i.e. primary) and associated with systemic disease, including autoimmune disease. Some biopsies showed coagulative necrosis, and some showed features resembling antibody mediated rejection of cardiac allografts. Clinical outcomes ranged from spontaneous resolution to persistent heart failure. • Histiocytic myocarditis appears to be a distinct histopathological subtype associated with heterogeneous clinical contexts and outcomes, and its presence may reflect antibody mediated myocardial injury. Endomyocardial biopsy results are integral for diagnosis and management of myocarditis. Current diagnostic classifications of myocarditis are based on the microscopic and immunochemical characterization of inflammation do not include monocyte/macrophage-predominant (i.e. "histiocytic") myocarditis as a histologic subtype. Endomyocardial biopsies from 6 patients with sudden heart failure were reviewed by 3 cardiac pathologists. Routine stains and immunostains to identify T cells and monocytes/macrophages, complement C4d, and endothelium were applied. Electron microscopy was performed in 2 cases. The 6 patients included 2 with diagnoses of systemic lupus erythematosus (SLE) and 4 without known disease. Microscopy showed space-occupying inflammation in 2 cases and interstitial inflammation in 4. No giant cell myocarditis or eosinophilic myocarditis was found. Immunostains showed infiltration predominantly by macrophages and/or monocytes with markedly fewer T cells. In 4 of 6 cases necrotic cells were immunopositive for complement C4d. Monocytes we identified immunochemically within the microvasculature in 5 cases and by electron microscopy in 2. Patients with SLE had microvascular C4d positivity or interstitial/sarcolemmal staining. Clinical outcomes ranged from spontaneous resolution to persistent heart failure requiring an internal cardioverter/defibrillator. (1) Heart failure with CD68 predominant inflammation ("histiocytic" myocardial inflammatory disease, HMID) occurs with variable clinical presentation and outcome; (2) HMID may be primary or secondary; (3) some cases of HMID show features suggestive of antibody and/or complement mediated myocardial injury, and (4) HMID is a diagnosis distinct from those in classification systems currently in use. [ABSTRACT FROM AUTHOR]

We demonstrated an extremely unusual case of an 83-year-old male's sudden death secondary to characteristic myocardial necrosis and fibrosis with calcification and multinucleated giant cells infiltration, possibly due to sepsis and Stage IV pulmonary pleomorphic carcinoma-induced cachexia after postmortem study. We propose that this calcifying giant cell cardiomyopathy (CGC) would be a new entity especially from the pathological viewpoints and should be considered in the classification of noninfectious myocarditis. Further prospective studies are needed to validate the presence and significance of CGC and the association with any triggers of somewhat microvascular dysfunction and/or toxic agents, after collecting and investigating a larger number of CGC cases examined. [ABSTRACT FROM AUTHOR]

Abstract: Background: The long-term prognosis of biopsy-proven myocarditis is not well known. We hypothesized that a detailed pathological examination of an endomyocardial biopsy (EMB) would reveal prognostic information in patients with acute myocarditis. Methods: Fifty-four patients were diagnosed with acute myocarditis based on an EMB. Pathological diagnosis was categorized into lymphocytic dominant (29.6%), eosinophilic dominant (22.2%), and borderline myocarditis (48.1%). Masson’s trichrome staining and further immunohistochemical staining for CD3, CD20, CD68, HLA-DR, TLR4, TLR8, enteroviral VP1, and caspase-3 expression were performed. The clinical outcomes were defined as all-cause and cardiovascular (CV) death. Results: During the median 10.4 years of follow up (9.7±5.7 years), the overall all-cause mortality was 20.4% and the CV mortality was 14.8% in patients with acute myocarditis. Lymphocytic dominant myocarditis patients showed a poor clinical outcome when compared with eosinophilic dominant myocarditis patients for both all-cause (37.5% vs. 0%, p=0.015) and CV (31.2% vs. 0%, p=0.029) mortality. Among borderline myocarditis patients, the presence of fibrosis was linked with poor clinical outcomes in both all-cause (75.0% vs. 21.4%, p=0.045) and CV (100.0% vs. 25.0%, p=0.034) mortality. No significant associations between clinical outcome and all other immunohistochemical staining targets were observed. Conclusions: Detailed pathological evaluation on an EMB provides prognostic information in patients with acute myocarditis. EMB evaluation should be considered in patients with suspected myocarditis. [Copyright &y& Elsevier]

Background: Granulomatous myocarditis may develop into cardiomyopathy and severe congestive heart failure that requires implantation of a left ventricular assist device (LVAD). Methods: Left ventricular (LV) core samples were collected from 177 patients with severe heart failure at the time of LVAD implantation, and samples were histologically examined and graded for severity of hypertrophy and fibrosis. Granulomatous myocarditis incidentally seen in a subset of samples was characterized by staining and culturing for mycobacteria and fungi. Various clinical parameters in these patients were analyzed. Results: Of the 177 LV core samples examined, 6 (3.4%) showed nonnecrotizing granulomatous inflammation in the myocardial wall. Stains and cultures for mycobacteria and fungi were negative. All six patients [three women, three men; five African American, one Asian; mean age, 52±9 years (range, 41–61 years)] had arrhythmias and required an automatic implantable cardioverter defibrillator. Before LVAD implantation, the patients' mean cardiac index was 1.8±0.4 l/min/m2; cardiac output, 2.9±0.6 l/min; and ejection fraction, 20±2%. One year after LVAD implantation, one patient had undergone heart transplantation. At 2 years, a second patient was transplanted, and one died. At 3 years, a third patient was transplanted and died postoperatively; two patients remained on support. No clinical evidence indicated involvement of other organs or recurrence in the transplanted patients. Conclusion: The incidental diagnosis of granulomatous myocarditis in our patients indicates that histological study of LV core samples in patients who undergo LVAD implantation may contribute to the diagnosis and be a consideration in the management of the underlying cause of heart failure. [ABSTRACT FROM AUTHOR]

Abstract: Background: Viral myocarditis is often caused by coxsackievirus B3 (CVB3) infection and occurs more frequently in males. So far, the mechanisms for this sex difference are not fully elucidated. As a new proinflammatory T cell population, Th17 cells are required for the development of CVB3-induced myocarditis, but their impact on the gender bias in viral myocarditis is still unknown. Methods: Male and female mice were intraperitoneally infected with CVB3; 7 days later, the frequency of splenic Th17 cells and the expression of associated cytokines and transcriptional factors were compared. Meanwhile, the impact of sex hormones on Th17 cell differentiation post CVB3 infection was also evaluated. Results: In infected male mice, Th17 cell frequency was remarkably increased and significantly higher than that in female mice. Accordingly, the expression of associated cytokines and transcriptional factors was also obviously augmented in males. When neutralizing interleukin-17 by monoclonal antibody, the male prevalence of myocarditis was obviously abolished, further confirming the effect of Th17 cells on gender bias in viral myocarditis. It was also found that estradiol significantly inhibited the Th17 differentiation post CVB3 infection both in vitro and in vivo. However, testosterone showed no such effects. Conclusions: Th17 cells were predominantly induced in CVB3-infected males than females as the inhibitory effect of estrogen on Th17 differentiation and played an important role in the sex differences in the sensitivity to CVB3-induced myocarditis. This study may help us understand the role of Th17 cells in viral myocarditis and facilitate the development of corresponding therapeutic strategies. [Copyright &y& Elsevier]

Abstract: Background: C57BL/6 mice have been considered resistant to cardiotropic coxsackievirus B3 (CVB3)-induced myocarditis. However, establishment of viral myocarditis model in C57BL/6 mouse is still a necessity. Here, we discuss the effects of mouse initial body weight and different virus inoculation doses on the onset of acute viral myocarditis in C57BL/6 mouse. Methods: According to initial body weight, mice were grouped into group A (3–4 weeks, 11–15 g) and group B (5–6 weeks, 18–20 g). Then, each group was divided into three subgroups inoculated with different virus doses: 1000 50% tissue culture infectious dose (TCID50)/ml, 10,000 TCID50/ml, and 100,000 TCID50/ml. Virus existence and myocardium inflammatory infiltration conditions were observed and evaluated 7 days postinfection. Results: Immunohistochemistry staining showed that virus capsid protein VP1 appeared in the myocardia of virus-infected mice. Three subgroups in the lower-body-weight group (group A) came out with a higher mortality (40%–100%), while the higher-body-weight group (group B) showed a tendency for body weight decline. Histopathologically, myocardia of the survival cases in the lower-initial-body-weight group got inflammatory infiltration, while almost no inflammation appeared in the dead cases. In the higher-body-weight group, myocardium inflammatory infiltration deteriorated with the increase of virus doses and bared a relatively sound survival rate. Conclusions: This study indicated that the initial body weight and virus infection dose are two factors affecting the onset of viral myocarditis in C57BL/6 mice. Accordingly, initial body weight of 18–20 g and an inoculation dose of 100,000 TCID50/ml×0.3 ml CVB3 might be an optimal choice to induce acute viral myocarditis in C57BL/6 mice. [Copyright &y& Elsevier]

Abstract: Background: Giant cell myocarditis (GCM) is a rare disorder that is known primarily from North American, European, and Japanese case series. The clinical and pathological features of GCM in India have not been reported. Methods: We reviewed the pathology records from 1994 to 2010 from a tertiary care referral hospital in Mumbai for all cases of pathologically confirmed GCM. Gross and microscopic histological features and clinical characteristics of the GCM cases were described and qualitatively compared to GCM case series from other regions of the world. Results: The 12 cases of GCM constituted 0.005% of all autopsies and 0.8% of myocarditis cases. Gross pathological features included variably dilated chambers in 8/12 cases with multifocal involvement of the myocardium. Three had regional hypertrophy associated with marked lymphocytic infiltrate. There were unique cases of a posterior wall rupture with hemopericardium and a case with multiple epicardial inflammatory sessile polyps. A novel possible trigger was suggested by a positive serologic test for leptospirosis in one case. The clinical features including age, gender, presenting symptoms, and prognosis resemble those reported in autopsy-based case series from other regions. Conclusions: GCM affects patients in India at approximately the same rate as in Europe and Japan. The clinical and histological features of GCM are similarly severe and suggest a heart-specific autoimmune reaction. [Copyright &y& Elsevier]

Abstract: Background: The genomic DNA of parvovirus B19, a small single-stranded DNA virus of the genus Erythrovirus, has been shown to persist in solid tissues of constitutionally healthy, immunocompetent individuals. Despite these data, many case reports and series have linked the presence of parvovirus B19 genomic DNA, detected through nucleic acid amplification testing, with myocarditis and cardiomyopathy. Herein, we use multiple tools to better assess the relationship between parvovirus B19 and myocarditis and cardiomyopathy. Methods: Nucleic acid amplification testing, immunohistochemistry, in situ hybridization, and electron microscopy were used to assess the location and activity of parvovirus B19 in cases of myocarditis and in cases with no significant cardiac disease. Results: Nucleic acid amplification testing for parvovirus B19 genomic DNA was positive in 73% of patients with myocarditis/cardiomyopathy and in 26% of patients with no significant disease. In situ hybridization and immunohistochemistry showed that, in cases with amplifiable parvovirus B19 DNA, parvovirus B19 genomic DNA and viral protein production were present in rare mononuclear cells. Conclusions: In a majority of cases of myocarditis and a significant number of otherwise normal hearts, nucleic acid amplification testing detected persistent parvovirus B19 genomic DNA that did not play a significant pathogenic role. The source of parvovirus B19 DNA appeared to be interstitial mononuclear inflammatory cells and not myocardial or endothelial cells. Therefore, nucleic acid amplification testing alone is not diagnostically helpful for determining the etiology of adult myocarditis. [Copyright &y& Elsevier]

Abstract: Endomyocardial biopsy is a commonly performed useful procedure utilized for the evaluation of cardiac tissue. Biopsy may be used to monitor transplant rejection, but it has many other applications including the evaluation of myocarditis, cardiomyopathy, chest pain, arrhythmia, and secondary involvement by systemic diseases. Drug toxicity may be evaluated and neoplasms may be biopsied. Recent developments include advances in myocardial and viral molecular biology and advances in image or electrophysiology guided biopsy. The utility of endomyocardial biopsy is reviewed with consideration of these advances. [Copyright &y& Elsevier]

Abstract: Introduction: CD40 and CD40L, as costimulatory molecules, are reported to play a critical role for cytokine production and antigen-specific T-cell activation in acute viral myocarditis (VMC). The purpose of this study was to probe the therapeutic effect of CD40-Ig in coxsackievirus B3 (CVB3)-induced myocarditis. Methods: Adolescent male Balb/c mice were infected with cardiovirulent CVB3 and then injected with CD40-Ig (0.1 mg/kg) at 6 h and 3 days postinfection (pi), with IgG (0.1 mg/kg) as control. The surviving mice were sacrificed on the seventh day. The copies of CVB3 mRNA in the myocardium were detected by real-time PCR and the expression of CD40 protein and CD4+ T cell was assessed by immunohistochemistry method. The serum level of IL-4 and IFN-γ and their transcriptions in the myocardium were determined by ELISA and real-time PCR. Results: The mortality was low in VMC model mice receiving CD40-Ig treatment with relived inflammation and reduced transcription of CVB3 in the myocardium. The expression pattern of IFN-γ (Th1-related cytokine) and IL-4 (Th2-related cytokine) was altered to Th1 prevalence in the acute phase of VMC. Intervention of CD40-Ig switched the balance of Th1/Th2. Conclusions: Our findings suggest that intervention of CD40-Ig can relieve the myocardial injury and inhibit viral replication of CVB3 in VMC. Its mechanism may involve blocking the interaction between CD40 and CD40L and regulating the Th1/Th2 balance. [ABSTRACT FROM AUTHOR]

Abstract: The role of different types of infections in heart diseases is more important than commonly thought, with new and re-emerging infections (i.e., Mycobacterium tuberculosis). This review addresses the pathology of infective pericarditis, myocarditis, and endocarditis, mainly focusing on the significance of molecular techniques in the detection of infective agents. Molecular investigations represent important ancillary diagnostic tools and combined with other conventional approaches provide a more precise final diagnosis. A close collaboration and communication among cardiologists, cardiac surgeons, pathologists, and microbiologists is essential to ensure optimal diagnoses and management as well as a favorable impact on patient outcome. [Copyright &y& Elsevier]

Abstract: Background: Ventricular assistance device (VAD) implantation provides large ventricular core biopsies available for pathological assessment. We present here the pathological data from 60 apex removed during a 7-year-period in a single institution. Results: The most frequent specific lesions were ischemic myocardial damage. Nonspecific pathological features were quite as frequently observed and correspond either to dilated cardiomyopathies, chronic ischemic cardiopathies, or miscellaneous conditions. Myocarditis represented 10 out of the 60 cases. The pathological data changed the clinical diagnosis in four cases: 1 case of juvenile hemochromatosis featuring as myocarditis and three cases of myocarditis featuring as dilated cardiomyopathies. Conclusion: Apex pathological analysis provides definite diagnosis and contributes to determine the cases which the cardiac disease have a possibility to recover under VAD. [Copyright &y& Elsevier]

Abstract: Background: Myocarditis is an inflammatory disorder of the heart in which T lymphocytes have a central role. No effective treatment is currently at hand for management of the myocarditis. Lymphocyte function requires the active signal transducer Ras. We thus hypothesized that S-farnesylthiosalicylic acid (FTS), a synthetic small molecule that detaches Ras from the inner cell membrane and induces its rapid degradation, will attenuate experimental autoimmune myocarditis (EAM). Methods and results: Two groups of Lewis rats were induced to develop EAM by immunization with porcine cardiac myosin. Group A received 5 mg/kg of FTS, and group B received phosphate-buffered saline (PBS) according to two protocols: FTS or PBS was given 2 days before myosin immunization in protocol 1 and FTS or PBS was given 14 days after myosin immunization in protocol 2. FTS significantly suppressed myocarditis, and this effect was accompanied by a reduction in myosin-specific cellular and humoral immune responses. In the longer regimen, FTS treatment for 6 weeks was associated with preservation of myocardial function made evident by echocardiography. In vitro, FTS significantly attenuated the proliferation of lymphocytes from untreated myocarditic rats to myosin. Conclusions: FTS is effective in suppressing the progression of EAM and its consequent functional myocardial dysfunction. The effect may be mediated by suppression of the cellular and humoral responses to myosin. [Copyright &y& Elsevier]

Abstract: Background: Murine cytomegalovirus (MCMV) is an etiologic agent of acute and chronic myocarditis in BALB/c mice. Immunologic host responses appear to play a key role in pathogenesis but have been incompletely defined. Methods: BALB/c mice were infected with a sublethal dose of MCMV. Cytokine transcription and viral load (measured by quantitative real-time polymerase chain reaction) and histopathological analyses were performed at specified time points. Results: Increased tumor necrosis factor (TNF)-α, interleukin (IL)-6, and interferon (IFN)-γ, as well as IL-10 mRNA transcripts, were detected in the hearts of infected mice starting at Day 1 post-infection (p.i.), with peak levels occurring at Day 8 p.i. (7-fold, 14-fold, 41-fold, and 16-fold higher than background, respectively). Peak cytokine transcription significantly correlated with a 10-fold increase in viral load (P<.001) at Day 8 p.i. Myocarditis-related pathological changes, measured by infiltration foci, were greatest at Day 8 p.i., corresponding with peak cytokine transcription and significantly correlated with IFN-γ levels (P<.0001). Infiltration foci were predominantly composed of CD3+ T cells. Cardiac calcification was observed in most infected mice predominantly over the right ventricle. Histological analysis of heart sections from mice infected with recombinant enhanced green fluorescence protein-MCMV revealed a localized and sporadic pattern of virus throughout all heart layers. Conclusions: MCMV-induced myocarditis in BALB/c mice is characterized by in vivo production of proinflammatory cytokines in a pattern correlating with MCMV viral load. The infection pattern and inflammatory response is highly localized, sporadic, and involves endocardium, epicardium, as well as the myocardium, with greatest amounts of virus detected in areas of pathologic calcification. [Copyright &y& Elsevier]

Myocarditis is an inflammatory disease of myocardium, associated with nonischemic necrosis and degeneration of myocytes. Although the clinical course is rapid, myocarditis can lead to dilated cardiomyopathy with chambers dilatation and ventricular dysfunction. The pathophysiology of myocarditis in humans is not completely understood. There are several etiological agents implicated, mainly viral agents. The clinical presentation is extremely various, with nonspecific systemic symptoms until sudden death. The great variability of symptoms makes the diagnosis, therefore, extremely difficult. We report the case of a 40-year-old woman who developed, after childbirth, hyperthermia associated with neck and left arm pain; initially treated with acetaminophen, without any benefit, the young woman, after few days, died suddenly. The autopsy documented the presence of edematous lungs and enlarged and congested liver. The microbiological tests performed 4 days after death were negative. The heart was normal in shape and volume; a section of the left ventricle wall showed subendocardial discromic areas histologically characterized by multifocal perivascular and interstitial inflammatory infiltrates. These infiltrates consisted mainly of neutrophils with eosinophil component associated with myocyte necrosis and hemorrhagic interstitial infiltration. [ABSTRACT FROM AUTHOR]

Abstract: NK4 may be a promising agent to inhibit tumor invasion and metastasis. To observe the effects of NK4 on the cardiovascular system with pathological injury and to discuss the mechanism, we established an experimental model of viral myocarditis (VCM) by coxsackievirus B3 infection in Balb/c mice on Day 0 and administered NK4 twice daily to the VCM and control mice from Day 20 to Day 45. We then evaluated the cardiac function by means of ultrasonic inspection. Hepatocyte growth factor, TNF (tumor necrosis factor)-α, and angiotensin II levels in the myocardial tissue were measured with enzyme-linked immunosorbent assay. Myocardium histopathology was examined with hematoxylin and eosin stain. Collagen deposition of the myocardium was detected through Masson staining. Microvessel staining with the RECA antibody and apoptosis detection with terminal deoxynucleotidyl transferase-mediated dUTP-biotin end labeling were performed in the myocardium. The changes in MMP3 (matrix metalloproteinase 3), MMP9, TIMP1 (tissue inhibitor of metalloproteinase 1), and TGF (transforming growth factor)-β1 expression in the myocardium were measured by reverse-transcriptase polymerase chain reaction. We found that NK4 intervention increased TGF-β and angiotensin II expression, suppressed MMPs, improved the activities of TIMPs, and then promoted collagen deposition in the myocardium. NK4 intervention also decreased the microvessels'' density and increased the apoptotic cell count in the myocardia of VCM mice. However, we did not observe the obvious changes in the myocardia of control mice after NK4 intervention. These data suggest that NK4 made negative impacts on the restoration of cardiac function and the recovery from VCM in the experimental mice. [Copyright &y& Elsevier]

Abstract: Background: Heat stress prior to induction of various forms of cardiac injury has been shown to result in preconditioning and attenuation of subsequent damage. We evaluated the effects of whole-body hyperthermia (WBH) on experimental autoimmune myocarditis (EAM) induced either by injection of myosin or by adoptive transfer of lymphocytes. Methods and Results: Lewis rats were pretreated with WBH either 24 h prior to EAM induction (Group A1) or 14 days following EAM induction (Group A2). The control group included myocarditic rats that were not exposed to WBH (Group A3). Rats from Group A1 exhibited significant protection from myocarditis as compared to rats from Group A3, evidenced by reduced myocarditis scores (1.60±0.96 vs. 2.88±0.35, P=.016). Rats from Group A2 also exhibited protection from myocarditis although not significantly. In a second experiment, we used adoptive transfer of myosin-reactive lymphocytes to study the mechanism of WBH effect on myocarditis. There was evidence of microscopic myocarditis in four out of five rats that were injected with active lymphocytes (the Control Group B3). Myocarditis was not observed in rats adoptively transferred with preheated rat lymphocyes (Group B1) nor in preheated rats, which underwent administration of nonheated rat lymphocyes (Group B2). Conclusions: Whole-body hyperthermia attenuates experimental myocarditis in the rat. The beneficial effect of whole-body hyperthermia may be related to immunomodulatory effect and direct cardiomyocyte protection. [Copyright &y& Elsevier]

• Myocarditis is an uncommon but potentially life-threatening disease • Clinical onset varies from subclinical disease to sudden death • The evolution of myocarditis ranges from complete recovery to dilated cardiomyopathy • It is crucial to identify predictors of short and long-term outcomes • A correct diagnostic evaluation is crucial to provide an appropriate treatment Although it has been recognized for almost two centuries, myocarditis is still a challenging diagnosis due to the wide heterogeneity of its clinical manifestations and evolution. Moreover, the diagnostic gold standard, endomyocardial biopsy (EMB), is infrequently used, making hard to determine the exact incidence of myocarditis. Clinical presentation includes a wide range of symptoms, ranging from asymptomatic or subclinical disease with mild dyspnea and chest pain to sudden death, due to cardiogenic shock or malignant ventricular arrhythmias. Equally, the evolution of myocarditis largely varies: albeit short-term prognosis is usually good, with complete or partial recovery, dilated cardiomyopathy with chronic heart failure is the major long-term consequence of myocarditis, developing often several years after the acute onset. This narrative review aims to summarize the current knowledge about myocarditis, with a particular attention to predictors of short- and long-term prognosis, in order to provide a rational and practical approach to the diagnosis, evaluation and treatment of suspected myocarditis. [ABSTRACT FROM AUTHOR]

• A significant decrease in QRS duration and R-amplitude occur in VM mice. • A strong correlation between ECG alteration and inflammation in the ventricles. • No correlation between ECG alteration and lesion size/ fibrosis in the ventricles. • The inflammation can form an important arrhythmogenic substrate in mild VM. Viral myocarditis (VM) can induce changes in myocardial electrical conduction and arrhythmia. However, their relationship with myocarditis-associated arrhythmic substrates in the heart such as inflammation and fibrosis is relatively unknown. This we have analyzed in the present study. C3H mice were infected with 1×105 plaque-forming units Coxsackievirus B3 (CVB3, n=68) and were compared with uninfected control mice (n=10). Electrocardiograms (ECGs) were recorded in all conscious mice shortly before sacrifice and included heart rate; P-R interval; QRS duration; QTc interval and R-peak amplitude of lead II and aVF. Mice were sacrificed at 4, 7, 10, 21, 35 or 49 days post-infection. Cardiac lesion size, calcification, fibrosis and cellular infiltration of CD45+ lymphocytes, MAC3+ macrophages, Ly6G+ neutrophils and mast cells were quantitatively determined in cross-sections of the ventricles. Putative relations between ECG changes and lesion size and/or cardiac inflammation were then analyzed. Significant transient reductions in QRS duration and R-peak amplitude occurred between 4 and 14 days post-infection and returned to baseline values thereafter. The magnitude of these ECG changes strongly correlated to the extent of lymphocyte (days 7 and 14), macrophage (days 7 and 10) and neutrophil (days 7) infiltration. The ECG changes did not significantly correlate with lesion size and fibrosis. VM induces transient changes in myocardial electrical conduction that are strongly related to cellular inflammation of the heart. These data show that even in mild VM, with relatively little cardiac damage, the inflammatory infiltrate can form an important arrhythmogenic substrate. [ABSTRACT FROM AUTHOR]

• Endomyocardial biopsy remains a valuable diagnostic tool in patients with suspected myocarditis. • Seventy-five percent of our patients with a diagnostic biopsy for myocarditis had a Class I or IIa indication for biopsy. • ↑ age and ventricular arrhythmias associated with ↑ mortality in diagnostic biopsy myocarditis. • Twenty-five percent of diagnostic biopsy myocarditis patients did not have a 2007 guideline indication for biopsy. • Diagnostic biopsy myocarditis patients more frequently required inotropes + advanced therapies. Diagnostic endomyocardial biopsy (EMB) in patients with suspected myocarditis helps to direct therapy and guide prognosis. This study aimed to investigate the correlation between the 2007 clinical guideline indications for EMB and the presence of a diagnostic biopsy result and associated outcomes in patients with suspected myocarditis in a national quaternary referral center in a contemporary cohort. All cases of suspected myocarditis referred to the National Cardiac Transplant Centre who underwent EMB between 2009 and 2019 were identified retrospectively through pathology records. Outcomes including subsequent need for inotrope and/or mechanical circulatory support (MCS), heart transplantation and in-hospital mortality were recorded. In total, 25 (68% male, mean age of 45 ± 15 years) EMBs were performed for this indication across this time period, 64% (n = 16) of which demonstrated diagnostic results, the majority (75%, n = 12) identifying acute lymphocytic myocarditis, 13% (n = 2) giant cell, one patient (6.3%) eosinophilic and one (6.3%) an immune checkpoint inhibitor myocarditis. The majority of those with histologically confirmed myocarditis had a Class I or IIa guideline indication for EMB (n = 12, 75%). The remaining 4 patients (25%), either met Class IIb criteria (n = 2) or would not have been accounted for in this guideline. The majority of patients requiring inotropes and/or MCS (n = 9/11), and/or heart transplant (n = 3/4), or who later died (n = 4/5) were in the diagnostic biopsy group. In this 10-year National referral sample, 75% of patients with histologically confirmed myocarditis had a Class I or IIa indication for EMB, reinforcing the usefulness of traditional guidelines in this contemporary era. However, 25% of patients with a subsequent confirmed histological diagnosis had either none or a less well-established indication for EMB, highlighting the need for clinical suspicion outside of accepted clinical scenarios. [ABSTRACT FROM AUTHOR]

• COVID-19 hearts do not exhibit typical inflammatory myocarditis. • COVID-19 hearts are associated with increased numbers of CD68+ cells compared to appropriate control hearts and with hearts with myocarditis. • The role of CD68+ cells in the cardiac pathophysiology of COVID-19 needs more investigation. COVID-19 has a significant effect upon the cardiovascular system. While a number of different cardiovascular histopathologies have been described at post-mortem examination, the incidence of typical viral myocarditis in COVID-19 positive patients appears very low [1–3]. In this study, we further characterize and quantify the inflammatory cell infiltrate in a COVID-19 study cohort and compare the findings to both an age and disease matched control cohort and a cohort of patients diagnosed with typical inflammatory myocarditis. All study and control cohorts had 1 or more of the comorbidities most commonly associated with severe disease (hypertension, type II diabetes, obesity, or known cardiovascular disease). The results demonstrate a skewed distribution of the number of CD68+ cells in COVID-19 hearts, with upper quantiles showing a significant increase as compared to both matched control hearts, and those with myocarditis. In contrast, hearts from typical inflammatory myocarditis contained increased numbers of CD4+, and CD8+ cells compared to both COVID-19 and control cohorts. In conclusion, the presence of an increased number of CD68+ cells suggests that COVID-19 may incite a form of myocarditis different from typical viral myocarditis, and associated with diffusely infiltrative cells of monocytes/macrophage lineage. [ABSTRACT FROM AUTHOR]

Abstract: Background: Cardiac involvement in Lyme disease is uncommon and typically manifests clinically by conduction disturbances. Postmortem identification of Borrelia burgdorferi has never been reported in a case of Lyme carditis. Methods and Results: We describe the case of a 37-year-old Caucasian man with a 1-month history of fevers, rash, and malaise who died unexpectedly on the day after he underwent medical evaluation. The only clinical cardiac abnormality found was that of second-degree atrioventricular block. At autopsy, a diffuse carditis, characterized by infiltrates of macrophages, lymphocytes, and eosinophils and primarily in an interstitial, endocardial, and perivascular distribution, was found. Serologic testing from blood drawn on the day before his death demonstrated IgG and IgM antibodies against B. burgdorferi, confirmed by Western blot. Postmortem polymerase chain reaction (PCR) performed in myocardial tissue amplified B. burgdorferi DNA encoding outer-surface protein A. Conclusions: Lyme carditis should be considered in the differential diagnosis of interstitial myocarditis with mixed inflammatory infiltrates. This diagnosis can be confirmed by PCR testing. [Copyright &y& Elsevier]

Background: There are few systemic pathologic studies on myocarditis. This study aimed to clarify the pathologic characteristics of murine myocarditis. Methods: We recorded serial electrocardiograms in experimental viral myocarditis in mice and then examined their cardiac pathology. After taking baseline electrocardiograms, we inoculated the mice intraperitoneally with the encephalomyocarditis virus. Electrocardiograms were serially recorded until 220 days after the virus inoculation. Results: Serial electrocardiograms revealed ectopic beats, low voltage of the QRS complex, and the appearance of complete atrioventricular (AV) block. Corresponding myocardial lesions were found in the hearts of mice with these ectopic beats. Mononuclear cell infiltrations into the His bundle were most frequently found in mice with complete AV block. Conclusions: Inflammatory change with cellular infiltrations was the most common pathologic finding in mice with complete AV block. In clinical settings, anti-inflammatory therapy might be recommended for patients with myocarditis complicated with conduction disturbances. [Copyright &y& Elsevier]

Abstract: Background: Coxsackievirus B3 (CVB3) is the major causative agent of myocarditis in humans. In the mouse model, the inflammatory phase of myocarditis results in extensive damage to the heart and triggers profound extracellular matrix (ECM) remodeling, which may ultimately lead to dilated cardiomyopathy. Matrix metalloproteinases (MMPs) are regulators of the ECM and can degrade all the components in the matrix. Methods: Adolescent male mice were infected with cardiovirulent CVB3 and sacrificed at 3, 9, and 30 days post infection (pi). Transcription of MMP-2, MMP-9, and MMP-12 was assessed by reverse-transcriptase polymerase chain reaction (RT-PCR). Protein expression of these enzymes was examined using immunohistochemistry, and the activation status of MMP-2 and MMP-9 was assessed using gelatin zymography. Tissue inhibitors of metalloproteinases (TIMPs) were analyzed using immunoblotting assays. Myocarditic hearts were also stained with picrosirius red and viewed under polarizing light to examine the collagen network. Results: MMP-2, MMP-9, and MMP-12 transcription was increased at 9 days pi, as determined by RT-PCR. Immunohistochemistry confirmed an increase in translation of these MMP species, and zymographic analysis further showed elevated activation of MMP-2 and MMP-9 following CVB3 infection. TIMP-3 and TIMP-4 expression was down-regulated, while TIMP-1 and TIMP-2 remained constant throughout the infection. Mouse hearts stained with picrosirius red showed an increase in total amount of collagen during the acute phase of infection and disrupted fibrils at later timepoints. Conclusion: After CVB3 infection, ECM remodeling is triggered, and this response may involve increased expression and activation of MMPs. [Copyright &y& Elsevier]

Background: We evaluated the effect of pretreatment with complete Freund''s adjuvant (CFA) on experimentally induced myocarditis concomitant with the assessment of antigen-specific properties of disease-triggering lymphocytes.Methods and results: Rats pretreated with CFA a week prior to myosin immunization developed a significantly attenuated myocardial inflammation as compared to control-treated animals. Furthermore, prior administration of CFA virtually abolished histological evidence of myocarditis induced by transfer of antimyosin lymphocytes.CFA administered subcutaneously prior to myosin immunization resulted in a significant reduction in lymph node cell reactivity to myosin. Assessment of cultured medium from lymphocytes obtained from CFA-pretreated myosin-immunized rats revealed reduced levels of interferon gamma but an increased production of IL-10, suggesting an induction of a Thl to Th2 switch.Conclusions: Thus, CFA treatment suppressed both myosin-induced as well as adoptively transferred myocarditis concomitant with induction of antigen-specific unresponsiveness to myosin and skewing of the immune response in favor of a Th2-dominated profile. [Copyright &y& Elsevier]

Introduction: Viruses are known to induce apoptosis in their host cells. We studied whether cardiomyocyte apoptosis occurs upon coxsackievirus B3 (CVB3) infection and whether virus-associated apoptosis plays a role in the pathogenesis of experimental myocarditis. Methods: BALB/c mice were infected with two variants of CVB3 causing either mild or severe myocarditis. Myocardial and serum samples were collected from Day 1 to Day 14 after virus inoculation. Apoptosis was detected in myocardial tissue sections using the terminal transferase-mediated DNA nick end labelling (TUNEL) assay and staining of active caspase 3, and compared with the presence of infectious CVB3 and viral proteins in cardiomyocytes. Results: Compared with the noninfected control mice, infection with either CVB3 variant resulted in significantly increased cardiomyocyte apoptosis, which peaked on Day 5 after infection. At this time, the average percentages of apoptotic cardiomyocytes were 0.17% (SD 0.04; P=.03) and 0.77% (SD 0.11; P<.01) in mild and severe disease forms, respectively. The amount of apoptosis correlated with titers of infectious CVB3 in the heart muscle. Viral proteins were detected in the TUNEL-positive cells by immunohistochemistry. In the late stages of disease, apoptosis, together with inflammatory infiltrates persisted only in the severe disease form. Conclusions: CVB3-associated myocardial damage involves cardiomyocyte apoptosis. In the early stages of the disease, it appears to be triggered by viral replication in the cardiomyocytes. [Copyright &y& Elsevier]

Background: T-cell-mediated myocardial damage is known to be involved in acute myocarditis and dilated cardiomyopathy. Recently, we found that tumor necrosis factor (TNF) ligand superfamily costimulatory molecules, especially 4-1BBL, played an important role in the myocardial damage of murine acute viral myocarditis. Methods and results: To investigate the roles for CD27L, CD30L, OX40L and 4-1BBL, which belong to TNF ligand superfamily, in the development of acute myocarditis and dilated cardiomyopathy, we analyzed the expression of these antigens in the myocardial tissues of patients with acute myocarditis and dilated cardiomyopathy. We also examined expression of the receptors for these molecules, CD27, CD30, OX40 and 4-1BB, which belong to TNF receptor superfamily, on the infiltrating cells. Strong expression of CD27L, CD30L and 4-1BBL and weak to moderate expression of OX40L was found in the cardiac myocytes of patients with acute myocarditis. Moderate expression of CD27L, CD30L and 4-1BBL and weak expression of OX40L was found on the cardiac myocytes of patients with dilated cardiomyopathy. Most of the infiltrating cells expressed CD27, CD30 and 4-1BB and a part of the infiltrating cells expressed OX40. Conclusions: Our findings suggest that expression of TNF ligand superfamily costimulatory molecules on cardiac myocytes may play a role in the cell-mediated myocardial damage in patients with acute myocarditis and dilated cardiomyopathy as in murine viral myocarditis. [Copyright &y& Elsevier]

The pathophysiology of viral myocarditis is still a matter of debate. Humoral autoimmunity in postviral heart disease remains an attractive but complex hypothesis. Antigenic mimicry with or without cytolytic antibody properties has been shown to play a role in the immunopathogenesis of myocarditis with respect to sarcolemmal/myolemmal epitopes (including the beta-receptor), myosin and some mitochondrial proteins including the antinucleotide translocator (ANT)-carrier and dihydrolipoamid dehydrogenase. Today, refined two-dimensional Western blots are able to identify receptors and enzymes that are target of a humoral immune response or the consequence of an “immunization process.” A humoral immune response to an invading agent will most likely lead to immunodestruction first. After conversion to IgG, the continuing antibody response may indicate the healing or healed process and last for many years or life-long. This paper reviews our present knowledge on the humoral immune response in myocarditis and its interplay with the viral agents and the other components of the immune system. [Copyright &y& Elsevier]