Current Diagnostic and Therapeutic Aspects of Eosinophilic Myocarditis

A challenging case of eosinophilic myocarditis leading to heart failure and transplantation

The large spectrum of etiologies, severities, and histologic appearances of eosinophilic myocarditis (EoM) poses challenges to its diagnosis and management. Endomyocardial biopsy is the current gold standard for diagnosis. However, cardiovascular magnetic resonance imaging is becoming more frequently used to diagnose acute myocarditis because of enhanced sensitivity when compared to histopathologic examination, and its less invasive nature. We report a complicated case of EoM in a male in his mid-thirties that led to fulminant cardiogenic shock that required immunosuppressive therapy on day 5 of admission and implantation of a left ventricular assist device (LVAD) on day 30. EoM was diagnosed on histopathologic examination of the resected fragment of the left ventricular myocardium. Nine months after the initial presentation, the patient ultimately required heart transplantation. The explanted heart showed minimal residual interstitial inflammation with evidence of mildly active intimal arteritis and patchy areas of interstitial fibrosis. In this report, we describe our patient's clinical features and correlate them with imaging and histopathologic findings to illustrate the difficulty in diagnosing EoM, particularly in this complicated patient that ultimately required heart transplantation. The diagnosis can be challenging due to the variable histopathologic features, clinical presentation, and utilization of therapeutic medications and devices.

Autoimmune Myocarditis, Old Dogs and New Tricks

Autoimmunity significantly contributes to the pathogenesis of myocarditis, underscored by its increased frequency in autoimmune diseases such as systemic lupus erythematosus and polymyositis. Even in cases of myocarditis caused by viral infections, dysregulated immune responses contribute to pathogenesis. However, whether triggered by existing autoimmune conditions or viral infections, the precise antigens and immunologic pathways driving myocarditis remain incompletely understood. The emergence of myocarditis associated with immune checkpoint inhibitor therapy, commonly used for treating cancer, has afforded an opportunity to understand autoimmune mechanisms in myocarditis, with autoreactive T cells specific for cardiac myosin playing a pivotal role. Despite their self-antigen recognition, cardiac myosin-specific T cells can be present in healthy individuals due to bypassing the thymic selection stage. In recent studies, novel modalities in suppressing the activity of pathogenic T cells including cardiac myosin-specific T cells have proven effective in treating autoimmune myocarditis. This review offers an overview of the current understanding of heart antigens, autoantibodies, and immune cells as the autoimmune mechanisms underlying various forms of myocarditis, along with the latest updates on clinical management and prospects for future research.

Interleukin-5 Antagonist Monoclonal Antibody Therapy Improves Symptoms and Reduces Steroid Dependence in Eosinophilic Myocarditis Patients

Eosinophilic myocarditis (EM) is a rare disease associated with significant morbidity and mortality. This case series follows the clinical courses of 3 patients with EM. The use of mepolizumab, an anti-interleukin-5 monoclonal antibody, as an adjunctive treatment was associated with stabilization of cardiac function and improved long-term outcomes.

COVID-19 mRNA vaccine-related myocarditis: A PRISMA systematic review, imaging approach and differential diagnoses

We present a case involving a young individual who developed acute myocarditis on the fourth day following administration of a COVID-19 mRNA vaccine. The patient's condition was managed conservatively, resulting in a favorable outcome. This paper extensively discusses the pathogenesis, clinical manifestations, imaging characteristics of COVID-19 mRNA vaccine-related myocarditis and includes a comprehensive review of pertinent literature. Additionally, a systematic review of COVID-19 mRNA vaccine-related myocarditis, conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) principles, is presented. Healthcare professionals should maintain a clinical suspicion for COVID-19 mRNA vaccine-related myocarditis when encountering patients with confirmed myocarditis who have received recent COVID-19 mRNA vaccination, after ruling out other potential causes. The diagnosis of acute myocarditis primarily relies on adherence to the Lake Louise Criteria (LLC) for cardiac magnetic resonance (CMR). Nevertheless, specific CMR features or distinctive patterns indicative of COVID-19 mRNA vaccine-related myocarditis are currently undefined. Among patients with vaccine-related myocarditis, common CMR findings encompass subepicardial late gadolinium enhancement and T2-based myocardial edema, although these findings lack specificity and may resemble other medical conditions. Supportive care involving a short-term regimen of NSAIDs, colchicine, and steroids represents the cornerstone of treatment for this variant of myocarditis, which tends to be self-limiting with favorable short-term prognoses. Timely diagnosis is paramount for optimizing patient care.

Eosinophilic Myocarditis Resulting in Ventricular Tachycardia Storm

Eosinophilic myocarditis (EM) is a rare but potentially fatal complication of sustained eosinophilia that is characterized by eosinophilic infiltration into myocardial tissue. There are various etiologies of EM that can be classified into general categories: reactive, clonal, and idiopathic. We present a case of EM caused by chronic eosinophilic leukemia, a rare myeloproliferative neoplasm that frequently presents with sustained peripheral eosinophilia. This case displays several serious complications of EM, including recurrent ventricular tachycardia storm, cardiogenic shock, and mural thrombus formation despite anticoagulation. Diagnosis of EM can be difficult as formal diagnosis requires an endomyocardial biopsy. Once EM is suspected, identifying the underlying etiology of eosinophilia is critical for timely implementation of disease-specific therapy.

Role of immune cells in the pathogenesis of myocarditis

Myocarditis is an inflammatory heart disease that mostly affects young people. Myocarditis involves a complex immune network; however, its detailed pathogenesis is currently unclear. The diversity and plasticity of immune cells, either in the peripheral blood or in the heart, have been partially revealed in a number of previous studies involving patients and several kinds of animal models with myocarditis. It is the complexity of immune cells, rather than one cell type that is the culprit. Thus, recognizing the individual intricacies within immune cells in the context of myocarditis pathogenesis and finding the key intersection of the immune network may help in the diagnosis and treatment of this condition. With the vast amount of cell data gained on myocarditis and the recent application of single-cell sequencing, we summarize the multiple functions of currently recognized key immune cells in the pathogenesis of myocarditis to provide an immune background for subsequent investigations.

Eosinophilic myocarditis: comprehensive update on pathophysiology, diagnosis, prognosis and management

Hypereosinophilic syndromes are a group of disorders secondary to the accumulation of eosinophils leading to the injury of one or more organs. Among them, eosinophilic myocarditis (EM) is a rare form of inflammatory cardiomyopathy characterized by eosinophilic infiltration into myocardial tissue and subsequent release of substances with cell membrane damage and cell destruction. The degree of infiltration is thought to depend on the underlying condition, as well as the degree and duration of eosinophil exposure and ranges from mild localized disease to diffuse multifocal infiltrates associated with myocardial necrosis, thrombotic complications and endomyocardial fibrosis. The main causes of EM are hypersensitivity reactions, eosinophilic granulomatosis with polyangiitis, hypereosinophilic syndrome variants, infections and cancer. Clinical presentation can be variable, ranging from asymptomatic forms to life-threatening conditions, to chronic heart failure due to progression to chronic restrictive cardiomyopathy. Marked eosinophilia in peripheral blood, elevated serum eosinophilic cationic protein concentration and multimodality imaging may suggest the etiology of EM, but in most cases an endomyocardial biopsy must be performed to establish a definitive diagnosis. Systemic treatment varies greatly depending on the underlying cause, however the evidence of an eosinophilic infiltrate allows initiation of immunosuppressive therapy, which is the mainstay of treatment in idiopathic and in most forms of EM. Patients with helminthic infection benefit from anti-parasitic therapy, those with myeloid clone often need a tyrosine kinase inhibitor, while anticoagulant therapy should be undertaken in case of possible thrombotic complications.

Fulminant Eosinophilic Myocarditis Without Peripheral Eosinophilia

Eosinophilic myocarditis is a rare form of myocarditis characterized by eosinophilic infiltration and usually associated with peripheral hypereosinophilia. The clinical spectrum of eosinophilic myocarditis ranges widely, from mildly symptomatic to fulminant disease. When patients have fulminant eosinophilic myocarditis, high-dose corticosteroids can lead to dramatic improvement and peripheral eosinophil counts are used as an indicator of response to treatment. However, in some patients, peripheral eosinophilia is absent at initial presentation; reaching a diagnosis and determining treatment response can be challenging in this situation. This report describes a patient with fulminant eosinophilic myocarditis who initially presented with a normal peripheral eosinophil count, was diagnosed through an early endomyocardial biopsy, and was successfully treated with corticosteroids. Endomyocardial biopsy should be performed to confirm the presence of myocardial eosinophilic infiltration, especially for patients who present with fulminant myocarditis, even when peripheral eosinophilia is absent.

Paraneoplastic Syndromes from Head to Toe: Pathophysiology, Imaging Features, and Workup

Patients often have symptoms due to the mass effect of a neoplasm on surrounding tissues or the development of distant metastases. However, some patients may present with clinical symptoms that are not attributable to direct tumor invasion. In particular, certain tumors may release substances such as hormones or cytokines or trigger an immune cross-reactivity between malignant and normal body cells, resulting in characteristic clinical features that are broadly referred to as paraneoplastic syndromes (PNSs). Recent advances in medicine have improved the understanding of the pathogenesis of PNSs and enhanced their diagnosis and treatment. It is estimated that 8% of patients with cancer develop a PNS. Diverse organ systems may be involved, most notably the neurologic, musculoskeletal, endocrinologic, dermatologic, gastrointestinal, and cardiovascular systems. Knowledge of various PNSs is necessary, as these syndromes may precede tumor development, complicate the patient's clinical presentation, indicate tumor prognosis, or be mistaken for metastatic spread. Radiologists should be familiar with the clinical presentations of common PNSs and the selection of appropriate imaging examinations. Many of these PNSs have imaging features that can assist with arriving at the correct diagnosis. Therefore, the key radiographic findings associated with these PNSs and the diagnostic pitfalls that can be encountered during imaging are important, as their detection can facilitate early identification of the underlying tumor, reveal early recurrence, and enable monitoring of the patient's response to therapy. ^© RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Evaluation of myocardial performance by serial speckle tracking echocardiography in diagnosis and follow-up of a patient with eosinophilic myocarditis

BACKGROUND

Speckle tracking echocardiography (STE) has been used as an adjunct diagnostic modality in patients with eosinophilic myocarditis. Its serial dynamic nature, however, has never been reported before.

CASE PRESENTATION

A 17-year-old boy presented in cardiogenic shock state. His full blood count revealed an absolute eosinophilic count of 11.18 × 10³/μL. An emergency 2D echocardiogram (2DE) showed global left ventricular hypokinesia with LVEF = 9.0% by Simpson's method and a large amount of pericardial effusion. STE showed a global longitudinal strain (GLS) of - 4.1%. Because of his poor clinical status and presence of marked hypereosinophilia and the possibility of eosinophilic myocarditis (EM), parenteral pulse therapy with methylprednisolone and inotropes was started with subsequent improvement within the next 48 h. Over the next few days, he had his first cardiovascular magnetic resonance imaging (CMR), which showed late gadolinium enhancement (LGE) in different cardiac regions. After two weeks of therapy, he left the hospital in a stable condition, with LVEF = 38.0%, and GLS = - 13.9%. He did well during his two months of outpatient follow-ups and was found to have an absolute eosinophil count of 0.0% on several occasions. Unfortunately, he was re-admitted because of treatment non-compliance with almost the same, albeit milder, symptoms. The WBC count was 18.1 × 10³ per microliter, and the eosinophilic count was 5.04 × 10³/μL (28%). Heart failure treatment and high-dose prednisolone were started. After 15 days of admission, he got better and was discharged. During both hospital admissions and several months of follow-up, he had multiple 2DEs, STE, and two CMR studies. None of his STEs were identical to the prior studies and were dynamic with frequent wax and wanes throughout the admissions and follow-ups. Thus a single admission-time STE study was not sufficient enough to properly predict the patient's outcome. Follow-up STEs showed new sites of myocardial involvement despite the absence of eosinophilia.

CONCLUSION

The use of STE in this patient, proved to have an added value in the evaluation and stratification of the left ventricular function in patients with EM and can be used as a diagnostic adjunct to CMR for diagnosis of EM.

Eosinophilic myocarditis: Case report and brief review of the literature

Eosinophilic myocarditis (EM) is a cardiac manifestation of hypereosinophilic syndrome with a high mortality rate. EM shares imaging features similar to other restrictive cardiopathies, and include patchy intramural late gadolinium enhancement on cardiac magnetic resonance with or without presence of biventricular thrombus. Diagnosis is confirmed on histopathology, and is the current gold standard. Here we report clinical presentation and imaging findings of EM in a 70-year-old woman who presented with fever and chills.

Eosinophilic Myocarditis: An Often-Overlooked Diagnosis in Patients Presenting with Heart Failure

Introduction. Hypereosinophilic syndrome (HES) is a rare disease characterized by unexplained peripheral eosinophilia along with evidence of end-organ damage. Cardiac involvement is the most life-threatening consequence and is frequently underreported with a prevalence of around 5%. The gold standard for diagnosis is myocardial biopsy, but less-invasive imaging such as cardiac MR (CMR) has been frequently used to help with the diagnosis. We are presenting a unique case of a patient diagnosed with Eosinophilic myocarditis (EM) supported by CMR with rapid improvement after starting steroid treatment. Case Presentation. A 67-year-old African American female with extensive cardiovascular disease history presenting with chest pain was diagnosed with EM secondary to hypereosinophilic syndrome (HES). Lab workup revealed absolute eosinophils of 4.70 × 10³/μL (normal 0–0.75 × 10³/μL). Transthoracic echocardiography showed mild reduction in left ventricular function and a large obliterating thrombus in the right ventricular apex. CMR showed increased signal intensity at the left ventricular and right ventricular apex, consistent with myocardial edema. Subsequently, the patient was placed on dexamethasone 10 mg daily with significant symptomatic improvement. Discussion. EM is a rare complication of hypereosinophilic syndrome and can mimic common cardiovascular diseases such as acute exacerbation of heart failure or myocardial infarction. A high index of suspicion is essential especially in the setting of suggestive lab workup. CMR is a promising noninvasive and cost-effective alternative for myocardial biopsy in diagnosis.

Case Report: Multimodal Imaging Guides the Management of an Eosinophilic Leukemia Patient With Eosinophilic Myocarditis and Intracardiac Thrombus

Background

Eosinophilic leukemia (EL) is a rare, serious and potentially life-threatening condition characterized by the overproduction of eosinophils leading to tissue eosinophilic infiltration and damage. Although multiple organ systems may be involved, progressive eosinophilic myocarditis (EM) is the most common cause of morbidity and mortality. Early diagnosis and follow-up surveillance combined with multimodal imaging are crucial for appropriate treatment of EM.

Case Summary

It’s a rare case of EL with EM and intracardiac thrombus in a 59-year-old patient who presented with asthenia for 3 weeks. Full blood count analysis indicated significant eosinophilia. Bone marrow aspirate revealed dysplastic eosinophilia and a FIP1L1-PDGFRA fusion gene (4q12) was detected, confirming EL. Echocardiography revealed EM with intracardiac thrombus. This was later confirmed by cardiac magnetic resonance imaging. The patient was commenced on imatinib and prednisolone and good clinical response was obtained. Through 18F-FAPI PET/CT imaging, we obtained in vivo visualization of fibroblast activation changes in the early stage of cardiac structure remodeling. With anti-fibrotic therapy after heart failure, the patient achieved a good clinical response.

Conclusion

This case demonstrates in vivo visualization of fibroblast activation after EM. Multimodality imaging can provide early diagnosis and may guide tailored antifibrotic therapy in early stage of EM.

Eosinophilic Myocarditis: A Challenging Diagnosis

Eosinophilic myocarditis (EM) is a rare subtype of myocarditis that is characterized by eosinophilic infiltration of the myocardium and is associated with peripheral eosinophilia in most cases. The diagnosis is suspected in the presence of acute myocarditis and peripheral eosinophilia and is usually confirmed by endomyocardial biopsy (EMB) before starting steroid therapy. Here, we present a case of severe idiopathic eosinophilic myocarditis in a young man with a history of asthma and peripheral eosinophilia. He was treated with high-dose steroids despite negative EMB, and we noted a dramatic improvement in cardiac function. Our case highlights the importance of cardiac magnetic resonance (CMR) and clinical judgment in establishing the diagnosis of EM irrespective of the histopathologic result.

Cardiac MRI in Suspected Acute Myocarditis After COVID-19 mRNA Vaccination

PURPOSE

 To evaluate cardiac MRI characteristics in patients with suspected hypersensitivity myocarditis following mRNA COVID-19 vaccination.

MATERIALS AND METHODS

 Patients clinically suspected of acute myocarditis after COVID-19 vaccination were retrospectively analyzed and compared against a healthy control group. Cardiac MRI protocol included parameters such as T1 and T2 relaxation times, extracellular volume (ECV), T2 signal intensity ratio, and late gadolinium enhancement (LGE). Lymph node size was assessed in the patient group on the injection side. Student t-test, analyses of variance (ANOVA) with Tukey post-hoc test, and χ² test were used for statistical analysis.

RESULTS

 20 patients with clinically suspected post-vaccine myocarditis (28 ± 12 years; 12 men) and 40 controls (31 ± 11 years; 25 men) were evaluated. According to the 2018 Lake Louise criteria (LLC), patients with clinically suspected myocarditis were further subdivided into an LLC-positive group (n = 9) and an LLC-negative group (n = 11). The mean time of symptom onset after vaccination was 1.1 ± 1.2 days (LLC-positive) and 6.5 ± 9.2 days (LLC-negative). Group differences in inflammatory variables between myocarditis patients and control subjects were more pronounced in the LLC-positive group (e. g., T1 relaxation time: 1041 ± 61 ms [LLC positive] vs. 1008 ± 79 ms [LLC-negative] vs. 970 ± 25 ms [control]; p <.001; or T2 signal intensity ratio 2.0 ± 0.3 vs. 1.6 ± 0.3 [LLC-negative] and vs. 1.6 ± 0.3 [control], p = .012). LLC-positive patients were significantly faster in receiving an MRI after initial symptom onset (8.8 ± 6.1 days vs. 52.7 ± 33.4 days; p = .001) and had higher troponin T levels (3938 ± 5850 ng/l vs. 9 ± 11 ng/l; p <.001). LGE lesions were predominantly located at the subepicardium of the lateral wall. Axillary lymphadenopathy was more frequent in the LLC-positive group compared to the LLC-negative group (8/9 [89 %] vs. 0/11 [0 %], p < 0.001).

CONCLUSION

 Vaccine-induced myocarditis should be considered in patients with acute symptom onset after mRNA vaccination, especially if elevated serum troponin T is observed. Imaging findings of vaccine-induced myocarditis are similar to virus-induced myocarditis, allowing for the use of the Lake Louise Criteria for diagnostic purposes.

KEY POINTS

  · Vaccine-induced hypersensitivity myocarditis can be confirmed with cardiac MRI. · Especially patients with sudden onset of symptoms and elevated serum troponin T had positive cardiac MRI findings. · Cardiac MRI characteristics of vaccine-induced myocarditis are similar to those in virus-induced myocarditis.

CITATION FORMAT

· Kravchenko D, Isaak A, Mesropyan N et al. Cardiac MRI in Suspected Acute Myocarditis After COVID-19 mRNA Vaccination. Fortschr Röntgenstr 2022; DOI: 10.1055/a-1752-0951.

Eosinophilic Myocarditis: When Allergies Attack the Heart!

Eosinophilic myocarditis is a clinical condition whereby myocardial injury is mediated by eosinophilic infiltration. A number of underlying causes, including reactive, clonal, or idiopathic hypereosinophilic syndrome, may trigger eosinophilia. Disease presentation may vary from mild subclinical variants to fulminant myocarditis with thromboembolic complications, and in some cases, endomyocardial and valvular fibrosis may be seen. A detailed examination coupled with the use of multimodality imaging, and endomyocardial biopsy may help establish diagnosis. Treatment is aimed at symptomatic management and treating the underlying cause of eosinophilia, such as withdrawal of implicated drugs, antihelminthic therapy for infection, immunosuppression for autoimmune conditions, and targeted therapy with tyrosine kinase inhibitors in cases with clonal myeloid disorders.

A unique case report of relapsing eosinophilic myocarditis causing atrial myopathy and persistent sinus arrest

Background

Eosinophilic myocarditis (EM) is a rare and devastating condition. The underlying cause of EM is unknown, and the natural history is not well understood.

Case summary

A 20-year-old male presented in cardiogenic shock with preceding 24-h history of pleuritic chest pain associated with nausea and vomiting. Electrocardiogram showed sinus tachycardia with widespread ST elevation, significantly raised high-sensitivity troponin T, and raised white cell count with eosinophilia. Transthoracic echocardiogram demonstrated severe left ventricular (LV) impairment and a moderate-sized pericardial effusion. Right ventricular (RV) endomyocardial biopsy and bone marrow biopsy were performed, with both demonstrating prominent eosinophilia. He was initiated on pulse methylprednisolone leading to rapid clinical improvement with normalization of LV function. Day 9 after discharge, he was readmitted to hospital with presyncope and right heart failure. Electrocardiogram revealed junctional escape rhythm, and cardiac magnetic resonance imaging showed scarring confined to the atria. The patient was treated with mepolizumab and underwent an electrophysiology study with electroanatomical mapping, demonstrating sinus arrest and the absence of electrical activity throughout the right atrium. After much deliberation, an implantable cardioverter-defibrillator was implanted with a deep septal RV pacing lead and an apical RV defibrillator lead.

Discussion

We present a unique case of EM with two distinct phases: the first marked by severe LV impairment resolving with immunosuppression; the second characterized by atrial cardiomyopathy leading to persistent symptomatic sinus arrest necessitating permanent pacing. Close follow-up of EM after initial remission is essential to monitor for further complications including heart failure and arrhythmias.

"Heart in DRESS": Cardiac Manifestations, Treatment and Outcome of Patients with Drug Reaction with Eosinophilia and Systemic Symptoms Syndrome: A Systematic Review

Cardiac involvement in drug reaction with eosinophilia and systemic symptoms (DS) is rare but associated with high mortality. The aim of this research was to systematically review case reports by PRISMA guidelines in order to synthetize the knowledge of cardiac manifestations of DS. We identified 42 cases from 36 case reports. Women were two times more affected than men. Two-thirds of patients had cardiac manifestation in the initial phase of the disease, while in one-third of cases cardiac manifestations developed later (mean time of 70 ± 63 days). The most common inciting medications were minocycline (19%) and allopurinol (12%). In 17% of patients, the heart was the only internal organ affected, while the majority (83%) had at least one additional organ involved, most commonly the liver and the kidneys. Dyspnea (55%), cardiogenic shock (43%), chest pain (38%), and tachycardia (33%) were the most common cardiac signs and symptoms reported. Patients frequently had an abnormal ECG (71.4%), and a decrease in left ventricular ejection fraction was the most common echocardiographic finding (45%). Endomyocardial biopsy or histological examination at autopsy was performed in 52.4%, with the predominant finding being fulminant eosinophilic myocarditis with acute necrosis in 70% of those biopsied. All patients received immunosuppressive therapy with intravenous steroids, while non-responders were more likely to have received IVIG, cyclosporine, mycophenolate, and other steroid-sparing agents (60%). Gender and degree of left ventricular systolic dysfunction were not associated with outcomes, but short latency between drug exposure and the first DRESS symptom onset (<15 days) and older age (above 65 years) was associated with death. This underscores the potential importance of heightened awareness and early treatment.

Proposed Pathogenesis, Characteristics, and Management of COVID-19 mRNA Vaccine-Related Myopericarditis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the novel coronavirus causing coronavirus disease 2019 (COVID-19), has affected human lives across the globe. On 11 December 2020, the US FDA granted an emergency use authorization for the first COVID-19 vaccine, and vaccines are now widely available. Undoubtedly, the emergence of these vaccines has led to substantial relief, helping alleviate the fear and anxiety around the COVID-19 illness for both the general public and clinicians. However, recent cases of vaccine complications, including myopericarditis, have been reported after administration of COVID-19 vaccines. This article discusses the cases, possible pathogenesis of myopericarditis, and treatment of the condition. Most cases were mild and should not yet change vaccine policies, although prospective studies are needed to better assess the risk-benefit ratios in different groups.

Case Report: Acute Eosinophilic Myocarditis With a Low-Flow Heart Failure With Preserved Ejection Fraction Phenotype

Eosinophilic myocarditis is a rare subtype of myocarditis characterized by myocardial eosinophilic infiltration, and it is potentially fatal if left untreated. Although endomyocardial biopsy (EMB) is a cornerstone for the histological diagnosis of acute eosinophilic myocarditis (AEM), as it is an invasive procedure and has a low diagnostic accuracy, the diagnosis of AEM with hemodynamic instability remains challenging. We describe a case of AEM presenting as low-flow heart failure with preserved ejection fraction (HFpEF), with rapid progression to cardiogenic shock. The constellation of peripheral eosinophilia, increased left ventricular wall thickness, and HFpEF raised the suspicion of AEM. Contrast-enhanced computed tomography (CT) scan revealed heterogeneous hypoenhancement localized in the basal-to-mid septal and mid anterolateral walls of the left ventricle, strongly suggestive of acute inflammation. Based upon these findings, we performed CT-guided EMB, which lead to a definitive diagnosis. Subsequent high-dose corticosteroids allowed a rapid and dramatic recovery and normalization of cardiac structure and function. This case highlights the clinical importance of assessing AEM as a rare cause of HFpEF and the usefulness of CT-guided EMB in patients with hemodynamic instability.

Eosinophilic Myocarditis in a Patient With Strongyloides stercoralis Infection

A 40-year-old woman with a pulmonary embolism, central nervous system infarcts, and eosinophilia was referred for evaluation. Findings on echocardiography and cardiac magnetic resonance were consistent with eosinophilic myocarditis with left ventricular involvement. Further examination led to the diagnosis of Strongyloides stercoralis infection, and treatment with ivermectin and rivaroxaban resulted in clinical, laboratory, and cardiac imaging improvement. (Level of Difficulty: Intermediate.).

Fulminant Eosinophilic Myocarditis and VT Storm

Eosinophilic myocarditis is a rare and frequently fatal disease that is often undiagnosed until autopsy. We report a case of eosinophilic myocarditis with an unusual initial presentation of palpitations that subsequently evolved into ventricular tachycardia storm and death within 4 days. (Level of Difficulty: Beginner.).

Case Report of Fulminant Eosinophilic Myocarditis With Concomitant Pheochromocytoma

A 33-year-old woman presented with fulminant eosinophilic myocarditis requiring venoarterial extracorporeal membrane oxygenation (ECMO). A computed tomography (CT) scan revealed a retroperitoneal mass that was eventually diagnosed as a pheochromocytoma. This case highlights the need for a comprehensive diagnostic workup for acute cardiomyopathy manifesting as cardiogenic shock in young patients and the benefit of early initiation of mechanical support facilitating both diagnosis and recovery.

The multiple faces of autoimmune/immune-mediated myocarditis in children: a biopsy-proven case series treated with immunosuppressive therapy

The role of immunosuppressive therapy (IT) in paediatric autoimmune/immune‐mediated myocarditis remains poorly defined. To explore its role, we present a series of three consecutive paediatric patients with biopsy‐proven, virus negative, autoimmune/immune‐mediated myocarditis, with distinct clinical and pathological features, who have been successfully treated with IT, a 14‐year‐old boy with Loeffler's fibroblastic parietal endomyocarditis, a 6‐year‐old child with celiac disease with chronic active lymphocytic myocarditis, and a 13‐year‐old boy with long‐standing heart failure and active lymphocytic myocarditis. Patients started IT and entered follow‐up between July 2017 and September 2019; the first patient completed IT. IT was associated with a substantial and sustained recovery of cardiac function in our patients, regardless of their heterogeneous clinical and pathological features. Combination IT was well tolerated and enabled tapering and weaning off steroids.

Short-term use of "ECMELLA" in the context of fulminant eosinophilic myocarditis with cardiogenic shock

Background

Eosinophilic myocarditis (EM) is a rare form of myocarditis. Clinical presentation is various, includes cardiogenic shock and can often be fatal. Diagnosis is based on myocardial eosinophilic infiltration in endomyocardial biopsy. Mechanical circulatory support (MCS) is often required in patients suffering from severe cardiogenic shock. Among the available MCS options the “ECMELLA” concept, a combination of left ventricular venting by Impella® device and extracorporeal life support (ECLS) is possibly able to provide the necessary time frame for diagnostics and initiation of anti-inflammatory medication in patients with fulminant myocarditis.

Case presentation

We report a case of a 38‐year‐old woman who was presented to us in severe cardiogenic shock, quickly requiring hemodynamic support by an Impella CP® device. Further dramatic hemodynamic deterioration accompanied by multi-organ dysfunction required escalation of MCS via ECLS as veno‐arterial extracorporeal membrane oxygenation (VA-ECMO). After histopathological diagnosis of EM, our patient was put on immunosuppressive therapy with prednisolone. Recovery of both right and left ventricular function allowed explanation of VA-ECMO on day 4 and further hemodynamic improvement allowed removal of the Impella® device on day 9. The patient was discharged after 7 weeks with fully restored cardiac function and in a good neurological state.

Conclusions

In severe cardiac shock due to fulminant EM the ECMELLA concept as bridge-to-recovery seems to be a valid option to provide the required time for diagnostics and specific therapy.

Loeffler's Endocarditis: An Integrated Multimodality Approach

Loeffler's endocarditis (LE) is the cardiac manifestation of hypereosinophilic syndrome, a rare systemic disease characterized by the sustained production of eosinophils leading to organ damage. Few data, principally by case reports, are available regarding the diagnostic workup in patients with suspected LE. Thus, we have performed a systematic search of the literature dealing with imaging in LE and propose an integrated multimodality imaging approach in the cardiac diagnostics of LE patients. The aim is to provide an updated state-of-the-art review focused on noninvasive and invasive imaging modalities for this rare and underdiagnosed disease. Standard and advanced echocardiography are typically the first cardiac imaging examinations when LE is suspected and they are also used later in follow-up for prognostic stratification and assessing response to treatment. Cardiac magnetic resonance provides a more detailed anatomical and functional evaluation of cardiac chambers, tissue characterization for the presence and extension of myocardial edema and fibrosis, and ventricular thrombi identification. Computed tomography scan and [18F]-fluoro-deoxy-glucose positron emission tomography may be helpful in selected cases to evaluate the cardiac involvement of LE as well as the other noncardiac manifestations of hypereosinophilic syndrome. Endomyocardial biopsy may be considered in patients with high clinical suspicion of LE if noninvasive imaging findings are confusing or not conclusive. The appropriate use of invasive and noninvasive imaging modalities, combining the available techniques with the patients' clinical features, will hopefully lead to early diagnosis, more accurate staging of disease, and timely treatment of LE that may prevent the irreversible myocardial damage of LE and adverse cardiovascular events.

Inhibition of Bcl2L12 Attenuates Eosinophilia-Related Inflammation in the Heart

Background: The eosinophilic inflammation plays a critical role in myocarditis (Mcd); its underlying mechanism remains to be further elucidated. This study aims to investigate the role of Bcl2-like protein 12 (Bcl2L12) in inducing the defects of apoptosis in eosinophils (Eos) of the heart tissues.

Methods: Human explant heart samples were collected. Eosinophilia and myocarditis (Mcd)-like inflammation were induced in the mouse heart by immunizing with murine cardiac α-myosin heavy chain (MyHCα) peptides.

Results: Markedly more Eos were observed in heart tissues from patients with Mcd than those from patients with dilated cardiomyopathy. Eos isolated from Mcd hearts showed the signs of apoptosis defects. The Eo counts in the Mcd heart tissues were positively correlated with the Bcl2L12 expression in Eos isolated from the heart tissues. Exposure to interleukin 5 in the culture induced the expression of Bcl2L12 in Eos. Bcl2L12 bound c-Myc, the transcription factor of Fas ligand (FasL), to prevent c-Myc from binding to the FasL promoter, to restrict the FasL gene transcription in Eos. Inhibition of Bcl2L12 prevented the induction of eosinophilia and Mcd-like inflammation in the mouse heart.

Conclusions: The Bcl2L12 expression contributes to apoptosis defects in Eos of the Mcd heart. Blocking Bcl2L12 prevents the eosinophilia induction and alleviates Mcd-like inflammation in mice.

Allergy and the Heart: Eosinophilic Myocarditis With Biventricular Thrombi

A 40-year-old woman with history of atopy and peripheral eosinophilia presented with clinical signs of heart failure. Echocardiography revealed a restrictive cardiomyopathy with biventricular thrombi. Hypereosinophilic syndrome resulting in eosinophilic myocarditis (Loeffler’s syndrome) was diagnosed. This case highlights the workup, diagnosis, and management of hypereosinophilic syndrome with eosinophilic myocarditis. (Level of Difficulty: Advanced.)

Right sided heart failure secondary to hypereosinophilic cardiomyopathy - clinical manifestation and diagnostic pathway

Hypereosinophilic cardiomyopathy is a rare restrictive cardiomyopathy which often presents with left-sided heart failure. We present an interesting case of a 58-year-old male patient with known hypereosinophillic syndrome who had presented with congestive cardiac failure with predominant features of right-sided volume overload. Cardiac magnetic resonance imaging confirmed the diagnosis by demonstrating obliteration of the right ventricular apex and endocardial-delayed gadolinium enhancement at the mid-septal and inferior segment, at both the right ventricular and left ventricular apical region, consistent with fibrosis. He was successfully treated with intravenous diuretics to good effect.

This case report demonstrates a rare clinical presentation of right ventricle involvement in hypereosinophilic cardiomyopathy and the current pathway for diagnosis with the favoured emergence of cardiac magnetic resonance imaging. All patients with hypereosinophilic syndrome should be closely monitored for signs of cardiac involvement, as early treatment carries a better prognosis.

Fast spontaneous recovery from acute necrotizing eosinophilic myopericarditis without need for immunosuppressive therapy: a case report of a 27-year-old male

Background

Eosinophilic myocarditis (EM) is rare but accounts for 12-22% of histologically proven acute myocarditis cases. Acute necrotizing EM is considered an aggressive, life-threatening disease which is usually treated by high-dose corticosteroid therapy.

Case summary

We report the case of a 27-year-old man with acute severe pericarditic chest pain, moderately reduced left ventricular (LV) ejection fraction, and a small pericardial effusion. Troponin I level was highly elevated in the absence of coronary artery disease, leading to the diagnosis of acute myopericarditis. In the absence of blood eosinophilia and despite a negative cardiac magnetic resonance study, LV endomyocardial biopsy revealed an acute necrotizing EM. With conventional antiphlogistic and heart failure therapy, the patient became symptom-free and inflammatory and cardiac necrosis markers as well as LV ejection fraction normalized within days. Thus, in the absence of a systemic hypereosinophilic disorder, there was no need for steroid therapy. Long-term follow-up over 12 months showed sustained normalization of cardiac structure and function.

Discussion

Acute necrotizing eosinophilic myopericarditis is not always a dreadful cardiac disease. There are idiopathic cases which may quickly resolve without immunosuppression. There seems to be a publication bias towards critical cases.

Idiopathic eosinophilic myocarditis presenting with features of an acute coronary syndrome

Summary

A 62-year-old female was admitted with severe left-sided chest pain, nausea and pre-syncope. She had widespread T wave inversion on ECG and elevated troponins and was suspected to have an acute coronary syndrome event. Invasive coronary angiogram revealed normal coronary anatomy with no flow-limiting lesions. Echocardiography and cardiac MRI revealed impaired left ventricular (LV) systolic impairment, a mobile LV apical thrombus and a moderate global pericardial effusion with no significant compromise. Full blood count analysis indicated the patient to have significant eosinophilia, and the patient was diagnosed with idiopathic eosinophilic myocarditis. She was commenced on Prednisolone and Apixaban, and eosinophil levels returned to normal after 10 days of steroids. Over the course of 3 months, the patient had a complete recovery of her LV function and resolution of the LV thrombus. This case highlights a rare, reversible case of idiopathic eosinophilic myocarditis which may present similar to acute coronary syndrome.

Learning points:

Diagnostic and prognostic role of electrocardiogram in acute myocarditis: A comprehensive review

Background

Acute myocarditis represents a challenging diagnosis as there is no pathognomonic clinical presentation. In patients with myocarditis, electrocardiogram (ECG) can display a variety of non‐specific abnormalities. Nevertheless, ECG is widely used as an initial screening tool for myocarditis.

Methods

We researched all possible ECG alterations during acute myocarditis evaluating prevalence, physiopathology, correlation with clinical presentation patterns, role in differential diagnosis, and prognostic yield.

Results

The most common ECG abnormality in myocarditis is sinus tachycardia associated with nonspecific ST/T‐wave changes. The presence of PR segment depression both in precordial and limb leads, a PR segment depression in leads with ST segment elevation, a PR segment elevation in aVR lead or a ST elevation with pericarditis pattern favor generally diagnosis of perimyocarditis rather than myocardial infarction. In patients with acute myocarditis, features associated with a poorer prognosis are: pathological Q wave, wide QRS complex, QRS/T angle ≥ 100°, prolonged QT interval, high‐degree atrioventricular block and malignant ventricular tachyarrhythmia. On the contrary, ST elevation with a typical early repolarization pattern is associated with a better prognosis.

Conclusions

ECG alterations in acute myocarditis could be very useful in clinical practice for a patient‐tailored approach in order to decide appropriate therapy, length of hospitalization, and frequency of followup.

Cardiovascular Magnetic Resonance in Nonischemic Myocardial Inflammation: Expert Recommendations

This JACC Scientific Expert Panel provides consensus recommendations for an update of the cardiovascular magnetic resonance (CMR) diagnostic criteria for myocardial inflammation in patients with suspected acute or active myocardial inflammation (Lake Louise Criteria) that include options to use parametric mapping techniques. While each parameter may indicate myocardial inflammation, the authors propose that CMR provides strong evidence for myocardial inflammation, with increasing specificity, if the CMR scan demonstrates the combination of myocardial edema with other CMR markers of inflammatory myocardial injury. This is based on at least one T2-based criterion (global or regional increase of myocardial T2 relaxation time or an increased signal intensity in T2-weighted CMR images), with at least one T1-based criterion (increased myocardial T1, extracellular volume, or late gadolinium enhancement). While having both a positive T2-based marker and a T1-based marker will increase specificity for diagnosing acute myocardial inflammation, having only one (i.e., T2-based OR T1-based) marker may still support a diagnosis of acute myocardial inflammation in an appropriate clinical scenario, albeit with less specificity. The update is expected to improve the diagnostic accuracy of CMR further in detecting myocardial inflammation.

[Atrioventricular block and left ventricular wall mobility disorder in a 44-year-old female patient : A case report of a rarity with pitfalls]

Eosinophilic myocarditis is a rare condition with good treatment options, which can be difficult to diagnose. The clinical presentation can vary from asymptomatic to life-threatening forms. This article describes the case of a 44-year-old woman who suffered from vertigo, chest pain and dyspnea. The woman presented with an intermittent atrioventricular (AV) block II Mobitz type II° and mild impairment of left ventricular ejection fraction. Hypereosinophilia in the peripheral blood, cardiac magnetic resonance imaging (MRI) and endomyocardial biopsy led to the diagnosis of eosinophilic myocarditis, most likely as a result of an allergic reaction to Aspergillus fumigatus. A general treatment recommendation cannot be made due to the lack of evidence-based guidelines; however, recent scientific studies confirmed timely, high-dose steroid administration over several months to be the mainstay of treatment of eosinophilic myocarditis. The following article may be helpful in the early diagnosis and treatment of this underdiagnosed and insidious disease.

Clozapine-Induced Cardiotoxicity Presenting as Sepsis: A Case Report and Literature Review

Clozapine is an atypical antipsychotic agent indicated in the treatment of medication-resistant schizophrenia. It is often reserved as a last line of treatment owing to the potential for serious and potentially life-threatening side effects, the most serious being agranulocytosis requiring close hematological monitoring and possible discontinuation of the medication from further use in the patient even when the agranulocytosis resolves. Other complications of clozapine include sedation, weight gain, elevated triglyceride levels, postural hypotension, and tachycardia. However, the potentially serious complication of myocarditis, though rare (with an incidence of 3%), may lead to cardiomyopathy as described in our present case. We present a 21-year-old patient who was started on clozapine for management of schizophrenia. He developed fever and tachycardia and was admitted to the medical unit on intravenous antibiotics for management of sepsis as he met the criteria for systemic inflammatory response syndrome. His labs revealed an elevated troponin and trending eosinophilia, which, in the context of clozapine use, raises the suspicion of clozapine cardiotoxicity. Echocardiogram showed reduced systolic function (45%). Clozapine was immediately discontinued, and his repeat echocardiogram showed normalization of his systolic function. In view of the increased prevalence of psychiatric illnesses, internists should be aware of rare but potentially life-threatening side effects.

Cellular fraction analysis of pericardial effusion helps the diagnosis of eosinophilic myocarditis

Eosinophilic myocarditis is rare in children, and consequently, it is difficult to diagnose eosinophilic myocarditis rapidly. We report the clinical course of acute eosinophilic myocarditis with pericarditis in two adolescent boys and their associated electrocardiograms. The two patients, 13- and 14-year-old boys, developed cardiomegaly and chest pain with vomiting. On examination by two-dimensional echocardiography, thickening of the ventricular septum and a pericardial effusion were detected. The eosinophil count had increased by the pericardial effusion. Acute eosinophilic myocarditis often complicates a moderate to severe pericardial effusion owing to acute pericarditis. A cellular fraction analysis of the pericardial effusion is easy and useful for the diagnosis of eosinophilic myocarditis. Some serial changes in the electrocardiogram occur during each stage of acute eosinophilic myocarditis. They are induced by eosinophilic granules, which are capable of inducing tissue damage and dysfunction, and those changes in the electrocardiogram resemble the changes after an acute myocardial infarction. It is important to know the characteristics of eosinophilic myocarditis in order to prevent lethal complications.

Significance of troponin I level as a marker of disease activity in the management of acute necrotizing eosinophilic myocarditis with normal peripheral eosinophil count: a case report

Background

Eosinophilic myocarditis is characterized by myocardial eosinophilic infiltration and is largely associated with hypereosinophilia. However, eosinophilic myocarditis with a normal peripheral eosinophilic count has been previously reported. Since the absence of eosinophilia poses a challenge for therapeutic management, we evaluated whether troponin I (TnI) levels can be used in the management of eosinophilic myocarditis where peripheral eosinophilia is absent.

Case summary

We report the case of a 77-year-old woman who developed cardiogenic shock due to acute necrotizing eosinophilic myocarditis, which required mechanical circulatory support. She did not have hypereosinophilia, but endomyocardial biopsy confirmed massive infiltration of eosinophils into the myocardium. We administered high-dose corticosteroids for 3 days and she dramatically improved. Along with this, the TnI level, which was elevated at the time of patient presentation, also decreased after steroid therapy. Troponin I level did not increase again without taking any oral prednisolone, and the follow-up biopsy after 6 months showed complete recovery of eosinophilic myocarditis.

Discussion

Troponin I-guided treatment is a useful tool in the management of eosinophilic myocarditis because it helps with therapeutic decisions, especially in the absence of eosinophilia.

Acute peri-myocarditis with an unusual initial manifestation of gallbladder edema and a profound eosinophilic surge during convalescence

A 29-year-old man with fever and right upper quadrant pain was referred to our hospital. Ultrasonography revealed intense gallbladder edema and pericardial effusion. Despite no symptoms and signs related to heart failure, the patient was clinically suspected of cardiac dysfunction related to acute peri-myocarditis based on his symptoms of preceding fever and headache, pericardial effusion, positive troponin T value, elevated B-type natriuretic peptide level, and sequential changes on electrocardiography. With a profound eosinophilic surge (8,022/µL) during convalescence, acute peri-myocarditis and gallbladder edema resolved spontaneously. This case instructively shows that acute peri-myocarditis initially manifests with abdominal symptoms, mimicking acute acalculous cholecystitis. In addition, an extensive review of acute myocarditis cases with peripheral eosinophilia suggests that there is a subgroup characterized by a predilection for young and middle-aged men, concurrence of pericardial effusion, transient eosinophilic surge during convalescence, and favorable outcome.

Hypereosinophilic Syndrome Complicated by Eosinophilic Myocarditis With Dramatic Response to Steroid

Introduction. Eosinophilic myocarditis is an infiltrative disease that affects the myocardium leading to various presentations. It can be precipitated by medications, helminthiasis, or hypereosinophilic syndrome. Case. We present the case of a young, male patient who presented with palpitations and dyspnea and was found to have heart failure with reduced ejection fracture of 12%. His past medical history was significant for recent lung problem treated with steroids. Based on his history and laboratory findings, he was started on intravenous steroids for treatment of eosinophilic myocarditis. Within 3 days, his ejection fracture improved to 35%. Conclusion. Given the nonspecific clinical presentations, mimicking other diseases, high index of suspicion is warranted to diagnose eosinophilic myocarditis. This is crucial as early detection and treatment with steroids can lead to a dramatic response.

Transient Myocardial Thickening in Cats Associated with Heart Failure

Background

Cats with hypertrophic cardiomyopathy (HCM) and congestive heart failure (CHF) can have resolution of both left ventricular hypertrophy and CHF.

Objectives

To describe the clinical characteristics of cats with transient myocardial thickening (TMT) and CHF compared with a control population of cats without resolution of HCM.

Animals

A total of 21 cats with TMT, 21 cats with HCM.

Methods

Retrospective study. Clinical records at 4 veterinary centers were searched for TMT cases and a control group of cats with HCM and CHF. TMT was defined as initial maximal left ventricular wall thickness (LVWT) ≥6 mm with left‐sided CHF, with subsequent resolution of CHF, reduction in left atrium/aorta (LA/Ao), and LVWT<5.5 mm. HCM was defined as persistent LVWT ≥6 mm.

Results

Cats with TMT were younger (2 [0.4–11.4] years) than cats with HCM (8 [1.6–14] years) (P < 0.0001), and antecedent events were more common (15/21 versus 6/21, respectively) (P = 0.01). In cats with TMT, LVWT normalized from 6.8 [6.0–9.7] mm to 4.8 [2.8–5.3] mm and LA/Ao decreased from 1.8 [1.6–2.3] to 1.45 [1.2–1.7] after a mean interval of 3.3 (95% CI: 1.8–4.7) months. CHF recurred in 1 of 21 TMT and 15 of 21 cats with HCM. Cardiac treatment was discontinued in 20 of 21 cats with TMT and 0 of 21 HCM cats. All cats with TMT survived, whereas 8 of 19 cats with HCM died during the study period.

Conclusions and Clinical Importance

TMT occurs in younger cats, and antecedent events are common. The prognosis is better in cats with CHF associated with TMT than HCM.

Eosinophilic myocarditis as a first presentation of eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome)

We present the case of a 28-year-old man who presented with chest pain and elevated cardiac biomarkers, with no evidence of acute ischaemia. He had a pronounced eosinophilia, abnormal echocardiographic, cardiac MRI and CT findings. He underwent transbronchial biopsy of carinal lymph nodes and of lung parenchyma. Endomyocardial biopsy yielded an eosinophilic infiltrate. He was treated with high dose glucocorticoids and made a rapid recovery. Testing for FIP1L1-PDGFRA and other BCR-ABL1 mutations was negative. Ultimately, he was diagnosed with eosinophilic granulomatosis with polyangiitis, also known as Churg-Strauss syndrome.

Therapeutic effect of anti-IL-5 on eosinophilic myocarditis with large pericardial effusion

Eosinophilic myocarditis (EM) is a rare myocardial disease that results from various eosinophilic diseases, such as idiopathic hypereosinophilic syndrome, helminth infection, medications and vasculitis. Patients with EM may present with different severities, ranging from mild symptoms to a life-threatening condition. Diagnosis of EM is a challenge and requires an extensive workup, including endomyocardial biopsy. Treatment options are limited because EM is rare and there is a lack of randomised controlled trials. We report a case of EM that presented as cardiac tamponade, which was initially treated with high-dose prednisone and immunosuppressant medications without significant improvement. Mepolizumab (anti-interleukin (IL)-5 antibody) was then applied, leading to an increased ejection fraction and stabilised cardiac function. This case report shows, for the first time, that mepolizumab has novel effects in treating EM. Our findings suggest that mepolizumab can be used as a steroid-sparing agent for treating EM.

Dramatic and early response to low-dose steroid in the treatment of acute eosinophilic myocarditis: a case report

Background

Eosinophilic myocarditis encompasses a variety of etiologies and the prognosis varies. For patients with a hypersensitive response to medications, high-dose corticosteroids and discontinuation of culprit medications are the main treatments.

Case presentation

We reported a young man with biopsy-proven eosinophilic myocarditis which was possibly induced by Chinese herbal medicine. His heart failure and left ventricular hypertrophy improved soon after low-dose corticosteroid.

Conclusion

Low-dose corticosteroid may be effective in selected patients with eosinophilic myocarditis. Early echocardiographic follow-up is mandatory for evaluation of the clinical response.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-017-0547-9) contains supplementary material, which is available to authorized users.

Third-Degree Atrioventricular Block and Collapse Associated with Eosinophilic Myocarditis in a Horse

Third‐degree atrioventricular block (AVB) and primary inflammatory myocarditis are uncommon findings in horses. The horse of this report presented for collapse at rest and was found to have multiple cardiac arrhythmias, most notably 3rd‐degree AVB. The horse was subsequently diagnosed with eosinophilic myocarditis on necropsy, a rare form of myocarditis not previously reported in horses. Despite extensive testing, an etiologic agent could not be identified, illustrating the difficulty in identifying a specific cause of myocarditis in horses.