Noninvasive imaging in myocarditis

[Development of a Deep Learning Model for Judging Late Gadolinium-enhancement in Cardiac MRI]

PURPOSE

To verify the usefulness of a deep learning model for determining the presence or absence of contrast-enhanced myocardium in late gadolinium-enhancement images in cardiac MRI.

METHODS

We used 174 late gadolinium-enhancement myocardial short-axis images obtained from contrast-enhanced cardiac MRI performed using a 3.0T MRI system at the University of Tokyo Hospital. Of these, 144 images were used for training, extracting a region of interest targeting the heart, scaling signal intensity, and data augmentation were performed to obtain 3312 training images. The interpretation report of two cardiology specialists of our hospital was used as the correct label. A learning model was constructed using a convolutional neural network and applied to 30 test data. In all cases, the acquired mean age was 56.4±12.1 years, and the male-to-female ratio was 1 : 0.82.

RESULTS

Before and after data augmentation, sensitivity remained consistent at 93.3%, specificity improved from 0.0% to 100.0%, and accuracy improved from 46.7% to 96.7%.

CONCLUSION

The prediction accuracy of the deep learning model developed in this research is high, suggesting its high usefulness.

Acute myocarditis: an overview of pathogenesis, diagnosis and management

Acute myocarditis encompasses a diverse presentation of inflammatory cardiomyopathies with infectious and non-infectious triggers. The clinical presentation is heterogeneous, from subtle symptoms like mild chest pain to life-threatening fulminant heart failure requiring urgent advanced hemodynamic support. This review provides a comprehensive overview of the current state of knowledge regarding the pathogenesis, diagnostic approach, management strategies, and directions for future research in acute myocarditis. The pathogenesis of myocarditis involves interplay between the inciting factors and the subsequent host immune response. Infectious causes, especially cardiotropic viruses, are the most frequently identified precipitants. However, autoimmune processes independent of microbial triggers, as well as toxic myocardial injury from drugs, chemicals or metabolic derangements also contribute to the development of myocarditis through diverse mechanisms. Furthermore, medications like immune checkpoint inhibitor therapies are increasingly recognized as causes of myocarditis. Elucidating the nuances of viral, autoimmune, hypersensitivity, and toxic subtypes of myocarditis is key to guiding appropriate therapy. The heterogeneous clinical presentation coupled with non-specific symptoms creates diagnostic challenges. A multifaceted approach is required, incorporating clinical evaluation, electrocardiography, biomarkers, imaging studies, and endomyocardial biopsy. Cardiovascular magnetic resonance imaging has become pivotal for non-invasive assessment of myocardial inflammation and fibrosis. However, biopsy remains the gold standard for histological classification and definitively establishing the underlying etiology. Management relies on supportive care, while disease-specific therapies are limited. Although some patients recover well with conservative measures, severe or fulminant myocarditis necessitates aggressive interventions such as mechanical circulatory support devices and transplantation. While immunosuppression is beneficial in certain histological subtypes, clear evidence supporting antiviral or immunomodulatory therapies for the majority of acute viral myocarditis cases remains insufficient. Substantial knowledge gaps persist regarding validated diagnostic biomarkers, optimal imaging surveillance strategies, evidence-based medical therapies, and risk stratification schema. A deeper understanding of the immunopathological mechanisms, rigorous clinical trials of targeted therapies, and longitudinal outcome studies are imperative to advance management and improve the prognosis across the myocarditis spectrum.

Understanding long COVID myocarditis: A comprehensive review

Infectious diseases are a cause of major concern in this twenty-first century. There have been reports of various outbreaks like severe acute respiratory syndrome (SARS) in 2003, swine flu in 2009, Zika virus disease in 2015, and Middle East Respiratory Syndrome (MERS) in 2012, since the start of this millennium. In addition to these outbreaks, the latest infectious disease to result in an outbreak is the SARS-CoV-2 infection. A viral infection recognized as a respiratory illness at the time of emergence, SARS-CoV-2 has wreaked havoc worldwide because of its long-lasting implications like heart failure, sepsis, organ failure, etc., and its significant impact on the global economy. Besides the acute illness, it also leads to symptoms months later which is called long COVID or post-COVID-19 condition. Due to its ever-increasing prevalence, it has been a significant challenge to treat the affected individuals and manage the complications as well. Myocarditis, a long-term complication of coronavirus disease 2019 (COVID-19) is an inflammatory condition involving the myocardium of the heart, which could even be fatal in the long term in cases of progression to ventricular dysfunction and heart failure. Thus, it is imperative to diagnose early and treat this condition in the affected individuals. At present, there are numerous studies which are in progress, investigating patients with COVID-19-related myocarditis and the treatment strategies. This review focuses primarily on myocarditis, a life-threatening complication of COVID-19 illness, and endeavors to elucidate the pathogenesis, biomarkers, and management of long COVID myocarditis along with pipeline drugs in detail.

Enhanced Myocardial Tissue Visualization: A Comparative Cardiovascular Magnetic Resonance Study of Gradient-Spin Echo-STIR and Conventional STIR Imaging

Purpose

This study is aimed at evaluating the efficacy of the gradient-spin echo- (GraSE-) based short tau inversion recovery (STIR) sequence (GraSE-STIR) in cardiovascular magnetic resonance (CMR) imaging compared to the conventional turbo spin echo- (TSE-) based STIR sequence, specifically focusing on image quality, specific absorption rate (SAR), and image acquisition time.

Methods

In a prospective study, we examined forty-four normal volunteers and seventeen patients referred for CMR imaging using conventional STIR and GraSE-STIR techniques. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), image quality, T2 signal intensity (SI) ratio, SAR, and image acquisition time were compared between both sequences.

Results

GraSE-STIR showed significant improvements in image quality (4.15 ± 0.8 vs. 3.34 ± 0.9, p = 0.024) and cardiac motion artifact reduction (7 vs. 18 out of 53, p = 0.038) compared to conventional STIR. Furthermore, the acquisition time (27.17 ± 3.53 vs. 36.9 ± 4.08 seconds, p = 0.041) and the local torso SAR (<13% vs. <17%, p = 0.047) were significantly lower for GraSE-STIR compared to conventional STIR in short-axis plan. However, no significant differences were shown in T2 SI ratio (p = 0.141), SNR (p = 0.093), CNR (p = 0.068), and SAR (p = 0.071) between these two sequences.

Conclusions

GraSE-STIR offers notable advantages over conventional STIR sequence, with improved image quality, reduced motion artifacts, and shorter acquisition times. These findings highlight the potential of GraSE-STIR as a valuable technique for routine clinical CMR imaging.

Adolescent Onset of Acute Heart Failure

Heart failure in adolescents can manifest due to a multitude of causes. Presentation is often quite variable ranging from asymptomatic to decompensated heart failure or sudden cardiac death. Because of the diverse nature of this disease, a thoughtful and extensive evaluation is critical to establishing the diagnosis and treatment plan. Identifying and addressing reversible pathologies often leads to functional cardiac recovery. Some disease states are irreversible and progressive, requiring chronic heart failure management and potentially advanced therapies such as transplantation.

Characteristics of Electrocardiogram Findings in Fulminant Myocarditis

Fulminant myocarditis (FM) is an acute and severe form of myocarditis with rapid progression and poor clinical outcomes in the absence of acute or chronic coronary artery disease. Electrocardiogram (ECG) abnormalities can provide preliminary clues for diagnosis; however, there is a lack of systemic descriptions on ECG changes in FM populations. Thus, a retrospective analysis of 150 consecutive FM patients and 300 healthy controls was performed to determine the characteristic ECG findings in FM. All patients included had markedly abnormal ECG findings. Specifically, 83 (55.33%) patients had significantly lower voltage with remarkably decreased QRS amplitudes in all leads compared with healthy controls (p < 0.01), and 77 (51.33%) patients had a variety of arrhythmias with lethality ventricular tachycardia/ventricular fibrillation in 21 (14.00%) patients and third-degree atrioventricular block in 21 (14.00%) patients, whereas sinus tachycardia was only found in 43 (28.67%) patients with the median heart rate (HR; 88.00 bpm, IQR: 76.00-113.50) higher than that of controls (73.00 bpm, IQR: 68.00-80.00) (p = 0.000). Conduction and repolarization abnormalities were common in patients. A longer QTc interval (452.00 ms, IQR: 419.00-489.50) and QRS duration (94.00 ms, IQR: 84.00-119.00) were observed in patients compared to controls (QTc interval = 399.00 ms, IQR: 386.00-414.00; QRS duration = 90.00 ms, IQR: 86.00-98.00) (p < 0.05). Additionally, HR > 86.50 bpm, QTc > 431.50 ms, and RV5 + SV1 < 1.715 mV can be used to predict FM. Thus, marked and severe ECG abnormalities provide preliminary clues for the diagnosis of FM.

Pediatric Myocarditis

Myocarditis is a condition caused by acute or chronic inflammation of the cardiac myocytes, resulting in associated myocardial edema and myocardial injury or necrosis. The exact incidence is unknown, but is likely underestimated, with more mild cases going unreported. Diagnosis and appropriate management are paramount in pediatric myocarditis, as it remains a recognized cause of sudden cardiac death in children and athletes. Myocarditis in children is most often caused by a viral or infectious etiology. In addition, there are now two highly recognized etiologies related to Coronavirus disease of 2019 (COVID-19) infection and the COVID-19 mRNA vaccine. The clinic presentation of children with myocarditis can range from asymptomatic to critically ill. Related to severe acute respiratory syndrome-Coronavirus 2 (SARs-CoV-2), children are at greater risk of developing myocarditis secondary to COVID-19 compared to the mRNA COVID-19 vaccine. Diagnosis of myocarditis typically includes laboratory testing, electrocardiography (ECG), chest X-ray, and additional non-invasive imaging studies with echocardiogram typically being the first-line imaging modality. While the reference standard for diagnosing myocarditis was previously endomyocardial biopsy, with the new revised Lake Louise Criteria, cardiac magnetic resonance (CMR) has emerged as an integral non-invasive imaging tool to assist in the diagnosis. CMR remains critical, as it allows for assessment of ventricular function and tissue characterization, with newer techniques, such as myocardial strain, to help guide management both acutely and long term.

COVID-19 Associated Fulminant Myocarditis in a Fully-Vaccinated Female: A Case Report with Clinical Follow-up

Background

Myocarditis is considered a serious adverse event after COVID-19 infection. The risk and severity of myocarditis after COVID-19 disease decreased significantly in the vaccinated population. We present a case of cardiac magnetic resonance proven fulminant myocarditis following COVID-19 disease in a young female who was previously vaccinated with 2 doses of the BIBP (Sinopharm) vaccine.

Case summary

A 29-year-old female was referred to the hospital with acute chest pain, dyspnea, and nausea. Her electrocardiogram revealed ST-segment elevation in anterolateral leads with reciprocal changes in inferior leads. She was primarily diagnosed with ST-elevation myocardial infarction following spontaneous coronary artery dissection (SCAD) according to her age and gender. Her coronary angiography was normal. RT-PCR nasopharyngeal swab was positive for SARS-COV-2 infection. According to her history and excluding coronary artery diseases, she was clinically diagnosed with myocarditis and received corticosteroids, IVIG, and colchicine. She was discharged in a favorable condition after 11 days of hospitalization. Cardiac magnetic resonance imaging confirmed the diagnosis of myocarditis according to the updated lake Louise criteria. On her 4-month follow-up, she was asymptomatic, and her echocardiography showed improvement in biventricular function.

Discussion

The diagnosis of myocarditis caused by COVID-19 infection may be challenging as the symptoms of myocarditis, and COVID-19 disease may overlap. It should be considered when patients have acute chest pain, palpitation, elevated cardiac biomarkers, and new abnormalities in ECG or echocardiography. Cardiac MRI is a non-invasive gold standard modality for diagnosing and follow-up of myocarditis and should be used in clinically suspected myocarditis. The long-term course of myocarditis following COVID-19 disease is still unclear, but some evidence suggests it may have a favorable mid-term outcome.

Higher Troponin Levels on Admission are associated With Persistent Cardiac Magnetic Resonance Lesions in Children Developing Myocarditis After mRNA-Based COVID-19 Vaccination

BACKGROUND

Acute pericarditis/myocarditis is a rare complication of the mRNA-based vaccines and although mostly self-limiting, long-term sequelae remain unclear.

METHODS

We enrolled all patients admitted to the emergency department between September 2021 and February 2022 meeting the CDC work case definition, with symptoms onset after mRNA-based COVID-19 vaccine. Alternative virologic causes were excluded. Clinical data, laboratory values, cardiologic evaluation, electrocardiogram (ECG), and echocardiogram (ECHO) were collected on admission, at discharge, and during follow-up in all patients. Cardiac Magnetic Resonance (CMR) was performed only in those with signs consistent with myocarditis.

RESULTS

We observed 13 patients (11M and 2F), median age 15 years, affected by acute pericarditis/myocarditis after COVID-19 mRNA vaccination (11 after Comirnaty® and 2 after Spikevax®). Symptoms'onset occurred at a median of 5 days (range, 1 to 41 days) after receiving mRNA vaccine (13 Prizer 2 Moderna): 4 patients (31%) after the 1st dose, 6 (46%) after the 2nd, and 3 (23%) after 3rd dose. Increased levels of high-sensitive troponin T (hsTnT) (median 519,5 ng/mL) and N-terminal-pro hormone BNP (NT-proBNP) (median 268 pg/mL) and pathognomonic ECG and ECHO abnormalities were detected. On admission, 7 of 13 (54%) presented with myopericarditis, 3 (23%) with myocarditis, and 3 (23%) with pericarditis; CMR was performed in 5 patients upon pediatric cardiologist prescription and findings were consistent with myocarditis. At 12 weeks of follow-up, all but one patient (92%), still presenting mild pericardial effusion at ECHO, were asymptomatic with normal hsTnT and NT-proBNP levels and ECG. On CMR 6 of 9 patients showed persistent, although decreased, myocardial injury. Higher hsTnT levels on admission significantly correlated with persistent CMR lesions.

CONCLUSION

Evidence of persistent CMR lesions highlights the need for a close and standardized follow-up for those patients who present high hsTnT levels on admission.

Toxic myocarditis presenting as an acute coronary syndrome

Background

Acute myocarditis is one of the causes of acute non-ischemic myocardial injury mimicking acute coronary syndrome (ACS) on presentation. It is usually underdiagnosed due to the non-specificity of presenting symptoms, elevated troponin levels, and abnormal ECG (electrocardiogram) findings. Delayed contrast-enhanced cardiac MRI (CMR) is known as the gold standard imaging modality for differentiating acute non-ischemic myocardial injury from infarcted myocardium. The most frequent cause of myocarditis is viral infections, but further infrequent causes include other infectious pathogens, toxins, hypersensitivity drug reactions, and autoimmune diseases. Cannabis is one of the most abused illicit and recreational drugs in the world among adolescents and adults. Also, many reports of marijuana-associated cardiovascular risks have been established previously, mainly presenting as arrhythmias, myocardial infarction, and myocarditis.

Case presentation

A 19-year-old female, complaining of radiating chest pain to the left arm and jaw, along with associated sweating for 1 day. Initial work-up showed elevated troponin levels with ST segment elevation on ECG. On further investigation, CMR showed findings of myocarditis and negative virology work-up led to a work-up of proper history, which revealed marijuana abuse, with a history of consumption 3 days before presentation. Hence, it was diagnosed as toxic myocarditis secondary to presumed cannabis abuse and treated for same.

Conclusions

Non-ischemic myocardial injury causes like myocarditis should be considered in young patients especially, who are presenting to emergency with ACS. CMR should be used as a first line diagnostic imaging modality (based on its availability) in cases mimicking an ACS or suspected myocarditis, especially in young patients. Though viral etiology is considered the most common cause of myocarditis, less common causes such as toxic myocarditis must be considered in cases of young individuals presenting with ACS in an emergency.

Immune checkpoint inhibitor induced myocarditis, myasthenia gravis, and myositis: A single-center case series

BACKGROUND

Immune checkpoint inhibitors can result in overlap syndrome comprised of myasthenia gravis, myositis and myocarditis. However, the mortality predictors have not been clearly delineated.

METHODS

We examined the characteristics of 11 patients diagnosed with overlap syndrome at Cleveland Clinic. All the available clinical, diagnostic, biochemical and disease specific factors were examined. Clinical predictors of increased mortality were using student t-test for parametric data and Wilcoxon-signed rank testing for nonparametric data.

RESULTS

Seven patients out of eleven patients were alive during the analysis. Our study did confirm that troponins were indicator of early demise. However, study showed that elevated creatinine, BUN, and decreased hemoglobin were also observed in patients who met early demise. Unlike previously published studies, elevated NT Pro-BNP and reduced left ventricular ejection fraction were not a seen in this study. However, there were higher incidence of electrical abnormalities in deceased patients when compared to alive.

CONCLUSION

Our study is first to examine various clinical parameters of overlap syndrome that might be predictive of mortality. This study confirms troponin as possible predictor and adds elevated creatinine, BUN and reduced hemoglobin as possible early biomarkers in deceased patients. The analysis showed that reduced LVEF was not a seen in deceased patients.

Clinical Characteristics of Patients with Myocarditis following COVID-19 mRNA Vaccination: A Systematic Review and Meta-Analysis

COVID-19 mRNA vaccinations have recently been implicated in causing myocarditis. Therefore, the primary aim of this systematic review and meta-analysis was to investigate the clinical characteristics of patients with myocarditis following mRNA vaccination. The secondary aims were to report common imaging and laboratory findings, as well as treatment regimes, in these patients. A literature search was performed from December 2019 to June 2022. Eligible studies reported patients older than 18 years vaccinated with mRNA, a diagnosis of myocarditis, and subsequent outcomes. Pooled mean or proportion were analyzed using a random-effects model. Seventy-five unique studies (patient n = 188, 89.4% male, mean age 18-67 years) were included. Eighty-six patients had Moderna vaccines while one hundred and two patients had Pfizer-BioNTech vaccines. The most common presenting symptoms were chest pain (34.5%), fever (17.1%), myalgia (12.4%), and chills (12.1%). The most common radiologic findings were ST-related changes on an electrocardiogram (58.7%) and hypokinesia on cardiac magnetic resonance imaging or echocardiography (50.7%). Laboratory findings included elevated Troponin I levels (81.7%) and elevated C-reactive protein (71.5%). Seven patients were admitted to the intensive care unit. The most common treatment modality was non-steroid anti-inflammatory drugs (36.6%) followed by colchicine (28.5%). This meta-analysis presents novel evidence to suggest possible myocarditis post mRNA vaccination in certain individuals, especially young male patients. Clinical practice must therefore take appropriate pre-cautionary measures when administrating COVID-19 mRNA vaccinations.

Pediatric Myocarditis: What Have We Learnt So Far?

Myocarditis is an inflammatory disease of the myocardium that is troublesome to diagnose and manage, especially in children. Since the introduction of endomyocardial biopsy (EMB), new diagnostic tools have provided useful data. Especially when enhanced with immunohistochemistry and polymerase chain reaction (PCR) studies, EMB remains the gold standard for the diagnosis. Notably, cardiac magnetic resonance (MRI) is a non-invasive tool that can confirm the diagnosis and has a particular usefulness during the follow-up. The causes of myocarditis are heterogeneous (mostly viral in children). The course and outcome of the illness in the pediatric population represent a complex interaction between etiologic agents and the immune system, which is still not fully understood. The clinical presentation and course of myocarditis vary widely from paucisymptomatic illness to acute heart failure refractory to therapy, arrhythmias, angina-like presentation and sudden cardiac death. In this setting, cardiac biomarkers (i.e., troponins and BNP), although unspecific, can be used to support the diagnosis. Finally, the efficacy of therapeutic strategies is controversial and not confirmed by clinical trials. In this review, we summarized the milestones in diagnosis and provided an overview of the therapeutic options for myocarditis in children.

Fulminant Myocarditis Following SARS-CoV-2 Infection

A 60-year-old woman with a past medical history of asthma presented with fulminant myocarditis 9 days after testing positive for SARS-CoV-2 and 16 days after developing symptoms consistent with COVID-19. Her hospital course was complicated by the need for veno-arterial extracorporeal membrane oxygenation, ventricular arrhythmias, and pseudomonas bacteremia. She ultimately recovered and was discharged to home with normal left ventricular systolic function. Thereafter, she developed symptomatic ventricular tachycardia, for which she received an implantable cardioverter-defibrillator and antiarrhythmic drug therapy.

COVID-19-Associated Myocarditis: An Evolving Concern in Cardiology and Beyond

Simple Summary

Coronavirus disease-2019 (COVID-19) affects many organs in the body, including the heart. One complication of particular concern is inflammation of the heart muscle, called myocarditis. This paper presents updated research data on COVID-19-associated myocarditis. Specifically, we review the incidence, potential mechanisms, blood and imaging tests that can be used to detect the disease. We emphasize that, in contrast with early reports, recent data suggest that myocarditis in the setting of COVID-19 is relatively uncommon, yet infected individuals are at a substantially increased risk for poor outcomes. It is important to continue research in this area.

Abstract

The direct and indirect adverse effects of SARS-CoV-2 infection on the cardiovascular system, including myocarditis, are of paramount importance. These not only affect the disease course but also determine clinical outcomes and recovery. In this review, the authors aimed at providing an update on the incidence of Coronavirus disease-2019 (COVID-19)-associated myocarditis. Our knowledge and experience relevant to this area continues to evolve rapidly since the beginning of the pandemic. It is crucial for the scientific and medical community to stay abreast of current information. Contrasting early reports, recent data suggest that the overall incidence of SARS-CoV-2-associated myocarditis is relatively low, yet infected individuals are at a substantially increased risk. Therefore, understanding the pathophysiology and diagnostic evaluation, including the use of serum biomarkers and imaging modalities, remain important. This review aims to summarize the most recent data in these areas as they relate to COVID-19-associated myocarditis. Given its increasing relevance, a brief update is included on the proposed mechanisms of myocarditis in COVID-19 vaccine recipients.

Combined lenalidomide/bortezomib for multiple myeloma complicated by fulminant myocarditis: a rare case report of widely used chemotherapy

BACKGROUND

Drug-induced myocarditis is a rare complication of certain cancer treatments, characterized by the development of myocardial inflammation shortly after initiation of treatment, potentially leading to heart failure and/or malignant arrhythmias. The development of eosinophilic myocarditis after administration of lenalidomide has been described and bortezomib has been associated with the development of cardiomyopathies and atherosclerosis.

CASE SUMMARY

A 69-year-old woman, recently diagnosed with multiple myeloma underwent local radiotherapy for a pathological fracture of the 4th lumbar vertebra and was treated with bortezomib-lenalidomide-dexamethasone. Within 19 days after therapy initiation, she presented with gastrointestinal symptoms, an erythematous pruritic rash, and general fatigue. Surprisingly, routine electrocardiogram (ECG) showed upwardly concave ST-elevation in I and aVL and ST-depressions in II, III, and aVF. Troponin levels were markedly elevated to 5470 ng/L. Complete blood count revealed eosinophilia. Based on further cardiac work-up, including echocardiography, coronary angiography, and cardiac magnetic resonance imaging (MRI) showing positive T2 imaging and patchy subepicardial late gadolinium enhancement, she was diagnosed with hypersensitivity myocarditis. Additional endomyocardial heart biopsy did not reveal any abnormalities, probably due to sampling error. After discontinuation of chemotherapy and prompt treatment with high doses of corticosteroids, the patient recovered.

DISCUSSION

Diagnosis of drug-induced myocarditis can be challenging and even long known widely used (chemo)therapy should be considered a potential trigger. Early diagnosis and treatment are crucial, warranting alertness for suggestive symptoms. Cardiac biomarkers, ECG monitoring, and cardiac MRI are key to confirm the diagnosis. In patients with preserved left ventricular systolic function, two-dimensional speckle tracking echocardiography can provide additional diagnostic information. Every patient presenting with eosinophilia and/or acute onset of auto-immune symptoms after initiation of therapy with lenalidomide/bortezomib deserves prompt cardiac screening. The gold standard remains an endomyocardial biopsy, although sampling error may occur.

A Review of the Role of Imaging Modalities in the Evaluation of Viral Myocarditis with a Special Focus on COVID-19-Related Myocarditis

Viral myocarditis is inflammation of the myocardium secondary to viral infection. The clinical presentation of viral myocarditis is very heterogeneous and can range from nonspecific symptoms of malaise and fatigue in subclinical disease to a more florid presentation, such as acute cardiogenic shock and sudden cardiac death in severe cases. The accurate and prompt diagnosis of viral myocarditis is very challenging. Endomyocardial biopsy is considered to be the gold standard test to confirm viral myocarditis; however, it is an invasive procedure, and the sensitivity is low when myocardial involvement is focal. Cardiac imaging hence plays an essential role in the noninvasive evaluation of viral myocarditis. The current coronavirus disease 2019 (COVID-19) pandemic has generated considerable interest in the use of imaging in the early detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-related myocarditis. This article reviews the role of various cardiac imaging modalities used in the diagnosis and assessment of viral myocarditis, including COVID-19-related myocarditis.

Safety of Endomyocardial Biopsy in New-Onset Acute Heart Failure Requiring Veno-Arterial Extracorporeal Membrane Oxygenation

BACKGROUND

Endomyocardial biopsy (EMB) has an important role in determining the pathogenesis of new-onset acute heart failure (new-AHF) when noninvasive testing is impossible. However, data on safety and histopathologic outcomes in patients requiring veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is lacking.

METHODS

A retrospective, multicenter cohort of patients undergoing EMB while requiring VA-ECMO for new-AHF between 1990 and 2020 was compared with a cohort of nontransplant related biopsies not requiring VA-ECMO. Primary end point of the study was to determine the safety of EMB. Additionally, we describe the underlying pathogenesis causing new-AHF based on histopathologic examination of the samples obtained.

RESULTS

A total of 23 patients underwent EMB while requiring VA-ECMO (10.0%), 125 (54.3%) during an unplanned admission, and 82 (35.7%) in elective setting. Major complications occurred in 8.3% of all procedures with a significantly higher rate in patients requiring VA-ECMO (26.1% versus 8.0% versus 3.7%, P=0.003) predominately due to the occurrence of sustained ventricular tachycardia or need of resuscitation (13.0% versus 3.2% versus 1.2%, P=0.02). EMB led to a histopathologic diagnosis in 78.3% of the patients requiring VA-ECMO which consisted primarily of patients with myocarditis (73.9%).

CONCLUSIONS

EMB in patients requiring VA-ECMO can be performed albeit with a substantial risk of major complications. The risk of the procedure was offset by a histopathologic diagnosis in 78.3% of the patients, which for the majority consisted of patients with myocarditis. The important therapeutic and prognostic implications of establishing an underlying pathogenesis causing new-AHF in this population warrant further refinement to improve procedural safety.

Diagnosis and Management of Myocarditis in Children: A Scientific Statement From the American Heart Association

Myocarditis remains a clinical challenge in pediatrics. Originally, it was recognized at autopsy before the application of endomyocardial biopsy, which led to a histopathology-based diagnosis such as in the Dallas criteria. Given the invasive and low-sensitivity nature of endomyocardial biopsy, its diagnostic focus shifted to a reliance on clinical suspicion. With the advances of cardiac magnetic resonance, an examination of the whole heart in vivo has gained acceptance in the pursuit of a diagnosis of myocarditis. The presentation may vary from minimal symptoms to heart failure, life-threatening arrhythmias, or cardiogenic shock. Outcomes span full resolution to chronic heart failure and the need for heart transplantation with inadequate clues to predict the disease trajectory. The American Heart Association commissioned this writing group to explore the current knowledge and management within the field of pediatric myocarditis. This statement highlights advances in our understanding of the immunopathogenesis, new and shifting dominant pathogeneses, modern laboratory testing, and use of mechanical circulatory support, with a special emphasis on innovations in cardiac magnetic resonance imaging. Despite these strides forward, we struggle without a universally accepted definition of myocarditis, which impedes progress in disease-targeted therapy.

The potential role of plasma miR-155 and miR-206 as circulatory biomarkers in inflammatory cardiomyopathy

AIMS

Establishing a diagnosis of inflammatory cardiomyopathy (iCMP) by non-invasive means remains challenging despite advances in cardiac magnetic resonance imaging. Previous studies suggested the involvement of microRNAs in the pathogenesis of iCMP. We examined the association of a predefined set of circulatory microRNAs with clinical characteristics of iCMP and evaluated their diagnostic performance in suspected iCMP.

METHODS AND RESULTS

Eighty-nine patients with clinical suspicion of iCMP were included in the analysis. All patients underwent cardiac catheterization with left ventricular endomyocardial biopsy, echocardiography, and cardiac magnetic resonance imaging applying the Lake Louise criteria (LLC). Plasma levels of miR-21, miR-126, miR-133a, miR-146b, miR-155, and miR-206 were determined using real-time polymerase chain reaction. Based on immunohistological findings on endomyocardial biopsy, iCMP was diagnosed in 67% of study participants (n = 60). Plasma levels of miR-155 and miR-206 were significantly increased in patients with iCMP as compared with patients with dilated cardiomyopathy (P = 0.008 and P = 0.009, respectively). In receiver operating characteristic curve analysis, miR-155 and miR-206 demonstrated superior diagnostic performance for iCMP (0.68 and 0.67, respectively) compared with LLC [area under the curve (AUC) 0.60], Troponin T (AUC 0.51), and N-terminal pro-brain natriuretic peptide (AUC 0.51). While baseline miR-155 and miR-206 plasma levels were predictive for biopsy-proven iCMP (odds ratio = 2.61, 95% confidence interval = 1.28-5.31, P = 0.008 and odds ratio = 2.65, 95% confidence interval = 1.27-5.52, P = 0.009) on univariate logistic regression analysis, the presence of positive LLC, high baseline C-reactive protein, or presence of clinical symptoms and signs of viral infection failed to predict iCMP (P > 0.05, respectively).

CONCLUSIONS

The present data suggest that plasma levels of miR-206 and miR-155 are potential novel biomarkers for confirming the diagnosis of iCMP.

Combination of echocardiography and emergency endomyocardial biopsy for suspected myocarditis in the cardiovascular emergency medical care

Myocarditis is a fatal inflammatory disease of myocardium, diagnosed with clinical and histopathological findings by endomyocardial biopsy (EMB). Myocarditis has a variety of clinical presentations and a dynamic and sometimes rapid process of severity. Echocardiography plays an important role in the management of myocarditis because it has noninvasiveness and portability. Once acute myocarditis is suspected by an echocardiography, pathological information should be required as early as possible. In our cardiovascular center, emergency EMB suspecting myocarditis was performed in 19 cases (1.3%) among consecutive 1469 cases (70.1 ± 12.6 years old, male 67.5%) undergoing emergency coronary angiograms from April 2014 to September 2017. Hematoxylin-eosin stain of the biopsy specimens were prepared with microwave-accelerated histoprocessing within 3-5 hours after EMB for rapid pathological diagnosis of myocarditis. We reviewed the value of emergency echo-EMB combination leading to the early decision making of intensive care, corticosteroids and proper mechanical circulatory support prior to the possible sudden collapse in patients with myocarditis.

Implementation and Outcomes of a Clozapine-Associated Myocarditis Screening Program in a Region of South Australia-Lessons Learned

PURPOSE

Clozapine-associated myocarditis (CAM) is a serious complication, mostly occurring in the first month of treatment. Public mental health in South Australia introduced a screening protocol in 2011 using baseline and weekly C-reactive protein and troponin. The aim of this study was to assess protocol adherence and management of cases with positive screening results.

METHODS

We identified all patients commenced on clozapine in our area between 2012 and 2015. Those with abnormal C-reactive protein and/or troponin in the first 4 weeks of treatment were identified (potential cases). For those, we collected clinical characteristics and test results and reviewed their management.

FINDINGS

Protocol compliance increased to 80%. We identified 24 potential CAM cases, 8 at high risk based on established definition (7.6% of new commencements) and 9 formally diagnosed from 143 commenced on clozapine. Potential cases not meeting CAM definition were significantly more likely commenced on clozapine for the first time and have preexisting respiratory disease. Likely CAM cases were younger, and more often prescribed additional antipsychotics, specifically quetiapine. Seven (78%) of 9 patients diagnosed with CAM met published CAM definition. In 14 undiagnosed potential cases, 10 (71%) did not have timely testing to exclude CAM.

CONCLUSIONS

Maintaining a high index of suspicion, clinical monitoring and timely testing is important to supplement CAM screening protocols. More research is needed to identify those that can be safely rechallenged or even continue clozapine treatment with monitoring.

Cardiovascular Toxicity of Immune Checkpoint Inhibitors: Clinical Risk Factors

Purpose of Review

Immune checkpoint inhibitors, such as monoclonal antibodies targeting CTLA-4, PD-1, and PD-L1, have improved the outcome of many malignancies, but serious immune-related cardiovascular adverse events have been observed. Patients’ risk factors for these toxicities are currently being investigated.

Recent Findings

Interfering with the CTLA-4 and PD-1 axes can bring to several immune-related adverse events, including cardiotoxic events such as autoimmune myocarditis, pericarditis, and vasculitis, suggesting that these molecules play an important role in preventing autoimmunity.

Summary

Risk factors (such as pre-existing cardiovascular conditions, previous and concomitant cardiotoxic treatments, underlying autoimmune diseases, tumor-related factors, simultaneous immune-related toxic effects, and genetic factors) should be always recognized for the correct management of these toxicities.

Multi-organ point-of-care ultrasound for COVID-19 (PoCUS4COVID): international expert consensus

COVID-19 has caused great devastation in the past year. Multi-organ point-of-care ultrasound (PoCUS) including lung ultrasound (LUS) and focused cardiac ultrasound (FoCUS) as a clinical adjunct has played a significant role in triaging, diagnosis and medical management of COVID-19 patients. The expert panel from 27 countries and 6 continents with considerable experience of direct application of PoCUS on COVID-19 patients presents evidence-based consensus using GRADE methodology for the quality of evidence and an expedited, modified-Delphi process for the strength of expert consensus. The use of ultrasound is suggested in many clinical situations related to respiratory, cardiovascular and thromboembolic aspects of COVID-19, comparing well with other imaging modalities. The limitations due to insufficient data are highlighted as opportunities for future research.

Acute Myocarditis After Black Widow Spider Bite: A Case Report

The black widow spider (BWS) is a venomous spider whose bite can cause various clinical conditions that range from local damage to serious systemic complications, including death. Cases of myocarditis following a BWS bite are rare but they can be fatal on occasion. However, the prognostic significance of the bite and presentation of myocarditis is unknown. Our case involved a 50-year-old man who presented with myocarditis after being bitten by a BWS and subsequently admitted to the intensive care unit for cardiac monitoring. During the hospital stay, he showed worsening signs on both the electrocardiographic and echocardiographic evaluations despite therapeutic success. Subsequent cardiac magnetic resonance and coronary angiography investigations showed no significant alterations; blood and instrumental test results slowly improved, and the patient was discharged home after 12 days of hospitalization without complications. This case illustrates that acute myocarditis, although an infrequent complication of BWS bite, has the potential to be lethal. The correct diagnosis, which is not always easy to formulate, is important to identify those patients who can benefit from careful monitoring and specific therapies aimed at reducing the risk of life.

Diagnostic and prognostic role of cardiac magnetic resonance in acute myocarditis

Acute myocarditis (AM) is commonly found in everyday clinical practice. Differential diagnosis between various causes of myocardial damage with non-obstructive coronary arteries can be cumbersome for clinician. Moreover, AM may be provoked by a number of different causes and clinical presentation can be heterogeneous with potential overlap going from asymptomatic or subclinical to severe heart failure, arrhythmias, and death. Cardiac magnetic resonance (CMR) over the last decades has proven to be the diagnostic technique of choice since it allows identifying AM with excellent diagnostic accuracy. Latest technological advancement with parametric imaging such as T1 and T2 mapping further increases sensitivity and provides additional help towards a correct diagnosis. CMR however is no longer to be considered as a mere diagnostic tool but also as a powerful source of prognostic information. Scientific evidence has corroborated CMR's role beyond diagnosis demonstrating how late gadolinium enhancement (LGE) presence is a powerful predictor of cardiac events and how the presence of septal LGE is to be considered of worst prognosis regardless of LGE extension even in patients with preserved global systolic function. CMR should be routinely performed in all patients with AM suspicion since its diagnostic and prognostic role is of paramount important and could modify therapeutic strategy and subsequent clinical decisions.

Recognition and Initial Management of Fulminant Myocarditis: A Scientific Statement From the American Heart Association

Fulminant myocarditis (FM) is an uncommon syndrome characterized by sudden and severe diffuse cardiac inflammation often leading to death resulting from cardiogenic shock, ventricular arrhythmias, or multiorgan system failure. Historically, FM was almost exclusively diagnosed at autopsy. By definition, all patients with FM will need some form of inotropic or mechanical circulatory support to maintain end-organ perfusion until transplantation or recovery. Specific subtypes of FM may respond to immunomodulatory therapy in addition to guideline-directed medical care. Despite the increasing availability of circulatory support, orthotopic heart transplantation, and disease-specific treatments, patients with FM experience significant morbidity and mortality as a result of a delay in diagnosis and initiation of circulatory support and lack of appropriately trained specialists to manage the condition. This scientific statement outlines the resources necessary to manage the spectrum of FM, including extracorporeal life support, percutaneous and durable ventricular assist devices, transplantation capabilities, and specialists in advanced heart failure, cardiothoracic surgery, cardiac pathology, immunology, and infectious disease. Education of frontline providers who are most likely to encounter FM first is essential to increase timely access to appropriately resourced facilities, to prevent multiorgan system failure, and to tailor disease-specific therapy as early as possible in the disease process.

Myocarditis in the Setting of Cancer Therapeutics: Proposed Case Definitions for Emerging Clinical Syndromes in Cardio-Oncology

Recent developments in cancer therapeutics have improved outcomes but have also been associated with cardiovascular complications. Therapies harnessing the immune system have been associated with an immune-mediated myocardial injury described as myocarditis. Immune checkpoint inhibitors are one such therapy with an increasing number of case and cohort reports describing a clinical syndrome of immune checkpoint inhibitor–associated myocarditis. Although the full spectrum of immune checkpoint inhibitor–associated cardiovascular disease still needs to be fully defined, described cases of myocarditis range from syndromes with mild signs and symptoms to fatal events. These observations in the clinical setting stand in contrast to outcomes from randomized clinical trials in which myocarditis is a rare event that is investigator reported and lacking in a specific case definition. The complexities associated with diagnosis, as well as the heterogeneous clinical presentation of immune checkpoint inhibitor–associated myocarditis, have made ascertainment and identification of myocarditis with high specificity challenging in clinical trials and other data sets, limiting the ability to better understand the incidence, outcomes, and predictors of these rare events. Therefore, establishing a uniform definition of myocarditis for application in clinical trials of cancer immunotherapies will enable greater understanding of these events. We propose an operational definition of cancer therapy-associated myocarditis that may facilitate case ascertainment and report and therefore may enhance the understanding of the incidence, outcomes, and risk factors of this novel clinical syndrome.

Imaging-Specific Cardiomyopathies: A Practical Guide

Heart failure is a clinical syndrome with a broad spectrum of presentations. Cardiovascular imaging techniques such as echocardiography, cardiovascular magnetic resonance, computed tomography, and nuclear imaging play a crucial role in diagnosis, guiding management, and providing prognostic information. Each of these imaging modalities has their own respective strengths and weaknesses. Cardiac imaging can help differentiate between ischemic and nonischemic cardiomyopathies. Additionally, imaging techniques can display disease-specific findings, aiding in diagnosis of nonischemic cardiomyopathies and can provide a means to monitor response to therapy. The choice of imaging modality in the workup of cardiomyopathy should be based on the specific clinical question and the knowledge of the strengths and limitations of each imaging modality.

Longitudinal 18F-FDG PET imaging in a rat model of autoimmune myocarditis

AIMS

Although mortality rate is very high, diagnosis of acute myocarditis remains challenging with conventional tests. We aimed to elucidate the potential role of longitudinal 2-Deoxy-2-18F-fluoro-D-glucose (18F-FDG) positron emission tomography (PET) inflammation monitoring in a rat model of experimental autoimmune myocarditis.

METHODS AND RESULTS

Autoimmune myocarditis was induced in Lewis rats by immunizing with porcine cardiac myosin emulsified in complete Freund's adjuvant. Time course of disease was assessed by longitudinal 18F-FDG PET imaging. A correlative analysis between in- and ex vivo18F-FDG signalling and macrophage infiltration using CD68 staining was conducted. Finally, immunohistochemistry analysis of the cell-adhesion markers CD34 and CD44 was performed at different disease stages determined by longitudinal 18F-FDG PET imaging. After immunization, myocarditis rats revealed a temporal increase in 18F-FDG uptake (peaked at week 3), which was followed by a rapid decline thereafter. Localization of CD68 positive cells was well correlated with in vivo18F-FDG PET signalling (R2 = 0.92) as well as with ex vivo18F-FDG autoradiography (R2 = 0.9, P < 0.001, respectively). CD44 positivity was primarily observed at tissue samples obtained at acute phase (i.e. at peak 18F-FDG uptake), while CD34-positive staining areas were predominantly identified in samples harvested at both sub-acute and chronic phases (i.e. at 18F-FDG decrease).

CONCLUSION

18F-FDG PET imaging can provide non-invasive serial monitoring of cardiac inflammation in a rat model of acute myocarditis.

The Diagnostic and Clinical Approach to Pediatric Myocarditis: A Review of the Current Literature

Myocarditis is an inflammatory disease of the myocardium with a broad spectrum of clinical presentations, ranging from mild symptoms to severe heart failure. The course of patients with myocarditis is heterogeneous, varying from partial or full clinical recovery in a few days to advanced low cardiac output syndrome requiring mechanical circulatory support or heart transplantation. Myocarditis is a very heterogeneous disease, especially in the pediatric age group as worldwide disease myocarditis has been defined by the World Health Organization/International Society and Federation of Cardiology as an inflammatory disease of the heart muscle diagnosed by established histological, immunologic, and immunohistological criteria. Pediatric myocarditis remains challenging from the perspectives of diagnosis and management. Multiple etiologies exist, and the majority of cases appear to be related to viral illnesses. Enteroviruses are believed to be the most common cause, although cases related to adenovirus may be more frequent than suspected. The clinical presentation is extremely varied, ranging from asymptomatic to sudden unexpected death. A high index of suspicion is crucial. There is emerging evidence to support investigations such as serum N-terminal B-type natriuretic peptide levels, as well as cardiac magnetic resonance imaging as adjuncts to the clinical diagnosis. In the future, these may reduce the necessity for invasive methods, such as endomyocardial biopsy, which remain the gold standard. Management generally includes supportive care, consisting of cardiac failure medical management, with the potential for mechanical support and cardiac transplantation. Treatments aimed at immunosuppression remain controversial. The paediatrics literature is extremely limited with no conclusive evidence to support or refute these strategies. All these summarised in this article and the listed current literature showed that there is no consensus regarding aetiology, clinical presentation, diagnosis, and management of myocarditis in pediatric patients.

The Clinicopathological Profile of Eosinophilic Myocarditis

Eosinophilic myocarditis (EM) is a rare form of myocarditis. As there is extreme diversity in its manifestations, the true incidence is difficult to assess and no proper epidemiological criteria are present. It generally presents with a wide array of clinical manifestations. Clinical presentation tends to differ in cases and not all the patients show the same signs and symptoms. The etiology of EM often remains obscure but potential causes have been identified which may include hypersensitivity to drugs, exposure to certain viruses and parasites, and hyper-eosinophilic syndromes. Endomyocardial biopsy is considered to be a gold standard for the diagnosis of EM. Echocardiography, cardiac magnetic resonance, and bio markers particularly serum eosinophilic cationic protein concentrations are also known to aid in diagnosis. EM may lead to progressive, irreversible, and fatal myocardial damage if prompt diagnosis is not made and therapy is not initiated. The current treatment regimens include corticosteroids, cytotoxic agents, and immunosuppressive therapy. However, a proper treatment criterion is yet to be established.

Subclinical left ventricular dysfunction and correlation with regional strain analysis in myocarditis with normal ejection fraction. A new diagnostic criterion

BACKGROUND

The diagnosis of myocarditis is challenging, especially in case of normal left ventricular systolic function. The aim of this study is to test the hypothesis that 2D speckle tracking echocardiography (2DSTE) can detect subclinical left ventricular (LV) dysfunction in patients with myocarditis and preserved LV function without regional wall motion abnormalities and that regional strain analysis can correlate with cardiac magnetic resonance (CMR) findings.

METHODS

Study population consisted of 25 consecutive patients with myocarditis and 19 controls. All patients underwent a full echocardiographic study at the first day of their admission and in addition to conventional echocardiographic measurements, global longitudinal and circumferential strain of the left ventricle (LVGLS, LVCS accordingly), as well as regional strains of the lateral wall, were estimated. Moreover, all patients underwent a CMR scan during the first week from their admission.

RESULTS

Although there was no statistical difference between the two groups of patients in systolic function, myocarditis patients demonstrated significantly impaired LVGLS (-16.5 ± 2.2 vs -20.5 ± 1.3%, p < 0.0001) and LVCS (-16.4 ± 3.7 vs -20.9 ± 2%, p = 0.002), as well as segmental longitudinal strains of the lateral wall. CMR in all myocarditis patients revealed late gadolinium enhancement in the lateral left ventricle free wall.

CONCLUSIONS

In patients with acute myocarditis with preserved ejection fraction, 2DSTE evaluation appears to be a promising, useful noninvasive and inexpensive tool in addition to existing methods used for the diagnosis of acute myocarditis, since it seems to be able to identify myocardial fibrosis early in the setting of the disease.

Diagnostic role of strain imaging in atypical myocarditis by echocardiography and cardiac MRI

BACKGROUND

The diagnosis of myocarditis presenting as isolated acute chest pain with elevated troponins but normal systolic function is challenging with significant drawbacks even for the gold-standard endomyocardial biopsy.

OBJECTIVE

This study aimed to evaluate the diagnostic role of strain imaging by echocardiography and cardiac MRI in these patients.

MATERIALS AND METHODS

This was a retrospective review of children with cardiac MRI for acute chest pain with elevated troponins compared to normal controls. Echocardiographic fractional shortening, ejection fraction, speckle-tracking-derived peak longitudinal, radial, and circumferential strain were compared to cardiac MRI ejection fraction, T2 imaging, late gadolinium enhancement, speckle-tracking-derived peak longitudinal strain, radial strain, and circumferential strain.

RESULTS

Group 1 included 10 subjects diagnosed with myocarditis, 9 (90%) males with a median age of 15.5 years (range: 14-17 years) compared with 10 age-matched controls in group 2. All subjects in group 1 had late gadolinium enhancement consistent with myocarditis and troponin ranged from 2.5 to >30 ng/ml. Electrocardiogram changes included ST segment elevation in 6 and abnormal Q waves in 1. Qualitative echocardiographic function was normal in both groups and mean fractional shortening was similar (35±6% in group 1 vs. 34±4% in group 2, P=0.70). Left ventricle ejection fraction by cardiac MRI, however, was lower in group 1 (52±9%) compared to group 2 at (59±4%) (P=0.03). Cardiac MRI derived strain was lower in group 1 vs. group 2 for speckle-tracking-derived peak longitudinal strain (-12.8±2.8% vs. -17.1±1.5%, P=0.001), circumferential strain (-12.3±3.8% vs. -15.8±1.2%, P=0.020) and radial strain (13.6±3.7% vs. 17.2±3.2%, P=0.040). Echocardiography derived strain was also lower in group 1 vs. group 2 for speckle-tracking-derived peak longitudinal strain (-15.6±3.9% vs. -20.8±2.2%, P<0.002), circumferential strain (-16±3% vs. -19.8±1.9%, P<0.003) and radial strain (17.3±6.1% vs. 24.8±6.3%, P=0.010).

CONCLUSION

In previously asymptomatic children, myocarditis can present with symptoms of acute chest pain suspicious for coronary ischemia. Cardiac MRI and echocardiographic strain imaging are noninvasive, radiation-free tests of immense diagnostic utility in these situations. Long-term studies are needed to assess prognostic significance of these findings.

Assessment of TSPO in a Rat Experimental Autoimmune Myocarditis Model: A Comparison Study between [18F]Fluoromethyl-PBR28 and [18F]CB251

Overexpression of the 18-kDa translocator protein (TSPO) is closely linked to inflammatory responses in the heart, including myocarditis, which can lead to myocardial necrosis. In vivo assessment of inflammatory responses has enabled the precise diagnosis of myocarditis to improve clinical outcomes. Here, we evaluated TSPO overexpression in a rat model of experimental autoimmune myocarditis (EAM) compared to healthy rats using two TSPO radiotracers, [¹⁸F]fluoromethyl-PBR28 ([¹⁸F]1) and [¹⁸F]CB251 ([¹⁸F]2). All radiolabeling methods were successfully applied to an automated module for the reproducible preparation of TSPO radiotracers. Both radiotracers were directly compared in an EAM rat model, as well as in healthy rats to determine whether either radiotracer provides a more promising assessment of in vivo TSPO overexpression. [¹⁸F]2 provided more specific TSPO-uptake in the heart of the EAM rats (1.32-fold that of the heart-to-lung uptake ratio versus healthy controls), while [¹⁸F]1 did not show a significant difference between the two groups. Histopathological characterization revealed that a prominent positron emission tomography (PET) signal of [¹⁸F]2 in the EAM rats corresponded to the presence of a higher density of TSPO compared to the healthy controls. These results suggest that the imidazole[1,2-a]pyridine-based radiotracer [¹⁸F]2 is a sensitive tool for noninvasively diagnosing myocarditis related to inflammation of the heart muscle by assessing abnormal TSPO expression.

Noninvasive Imaging of Myocardial Inflammation in Myocarditis using 68Ga-tagged Mannosylated Human Serum Albumin Positron Emission Tomography

The diagnosis of myocarditis traditionally relies on invasive endomyocardial biopsy but none of the imaging studies so far are specific for infiltration of the inflammatory cells itself. We synthesized ⁶⁸Ga-2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) mannosylated human serum albumin (MSA) by conjugating human serum albumin with mannose, followed by conjugation with NOTA and labeling it with ⁶⁸Ga. The efficacy of ⁶⁸Ga-NOTA-MSA positron emission tomography (PET) for imaging myocardial inflammation was tested in a rat myocarditis model. A significant number of mannose receptor-positive inflammatory cells infiltrated the myocardium in both human and rat myocarditis tissue. ⁶⁸Ga-NOTA-MSA uptake was upregulated in organs of macrophage accumulation, such as liver, spleen, bone marrow and myocardium (0.32 (0.31~0.33) for normal versus 1.02 (0.86~1.06) for myocarditis (median (range), SUV); n=4~6 per group, p-value=0.01). ⁶⁸Ga-NOTA-MSA uptake in the left ventricle was upregulated in myocarditis compared with normal rats (2.29 (1.42~3.40) for normal versus 4.18 (3.43~6.15) for myocarditis (median (range), average standard uptake value ratio against paraspinal muscle); n=6 per group, p-value<0.01), which was downregulated in rats with cyclosporine-A treated myocarditis (3.69 (2.59~3.86) for myocarditis versus 2.28 (1.76~2.60) for cyclosporine-A treated myocarditis; n=6 per group, p-value<0.01). The specificity of the tracer was verified by administration of excess non-labeled MSA. ⁶⁸Ga-NOTA-MSA uptake was significantly enhanced earlier in the evolution of myocarditis before any signs of inflammation could be seen on echocardiography. These results demonstrate the potential utility of visualizing infiltration of mannose receptor-positive macrophages with ⁶⁸Ga-NOTA-MSA PET in the early diagnosis of as well as in the monitoring of treatment response of myocarditis.

Increased Echogenicity and Radiodense Foci on Echocardiogram and MicroCT in Murine Myocarditis

Objectives

To address the question as to whether echocardiographic and/or microcomputed tomography (microCT) analysis can be utilized to assess the extent of Coxsackie B virus (CVB) induced myocarditis in the absence of left ventricular dysfunction in the mouse.

Background

Viral myocarditis is a significant clinical problem with associated inflammation of the myocardium and myocardial injury. Murine models of myocarditis are commonly used to study the pathophysiology of the disease, but methods for imaging the mouse myocardium have been limited to echocardiographic assessment of ventricular dysfunction and, to a lesser extent, MRI imaging.

Methods

Using a murine model of myocarditis, we used both echocardiography and microCT to assess the extent of myocardial involvement in murine myocarditis using both wild-type mice and CVB cleavage-resistant dystrophin knock-in mice.

Results

Areas of increased echogenicity were only observed in the myocardium of Coxsackie B virus infected mice. These echocardiographic abnormalities correlated with the extent of von Kossa staining (a marker of membrane permeability), inflammation, and fibrosis. Given that calcium phosphate uptake as imaged by von Kossa staining might also be visualized using microCT, we utilized microCT imaging which allowed for high-resolution, 3-dimensional images of radiodensities that likely represent calcium phosphate uptake. As with echocardiography, only mice infected with Coxsackie B virus displayed abnormal accumulation of calcium within individual myocytes indicating increased membrane permeability only upon exposure to virus.

Conclusions

These studies demonstrate new, quantitative, and semi-quantitative imaging approaches for the assessment of myocardial involvement in the setting of viral myocarditis in the commonly utilized mouse model of viral myocarditis.

Myocardial T1 maps reflect histological findings in acute and chronic stages of myocarditis in a rat model

BACKGROUND

Cardiovascular magnetic resonance offers both diagnostic and prognostic information in myocarditis. Using an established animal model of myocarditis, the aim of this study was to measure myocardial T1 before the onset, in the acute and in the chronic phases of the disease and to compare its course with histological and immunohistochemistry findings.

METHODS

Male young Lewis rats were immunized with 0.25 mg porcine myocardial myosin into the rear footpads on day 0. Native and contrast-enhanced ECG-triggered cardiac MRI examinations were performed before immunization on day 0 and on days 14, 21 and 35. Left ventricular function, pre- and post- contrast T1 parameters and LGE images were assessed using Small animal look-locker inversion recovery (SALLI). For each of the indicated time points a minimum of 4 rats were randomly sacrificed for pathological investigations including conventional histology (HE and Sirius-Red staining) and immunohistochemistry (CD 68) investigations.

RESULTS

All immunized rats developed myocarditis (morbidity 100%). Histologically we observed increased wall thickness with biventricular macrophage-rich mixed inflammatory infiltrates. All rats with a histologically severe myocarditis showed increased native T1 and decreased post-contrast T1 of the myocardium.

CONCLUSIONS

The assessment of native T1 and post-contrast T1 allows accurate differentiation between healthy myocardium and myocardium with inflammation and also between the acute and chronic phases of the disease.

[Myocarditis in the differential diagnosis of cardiomyopathies. Endomyocardial biopsy or MRI?]

Myocarditis is an inflammatory disease of the heart muscle commonly caused by viral pathogens. Dilated cardiomyopathy is a major long-term sequela of myocarditis and at least in part related to post-viral immune-mediated responses. Establishing a diagnosis of myocarditis represents a major challenge because of the variable clinical picture and the lack of readily available, non-invasive diagnostic tests. In recent years, cardiac magnetic resonance imaging (cMRI) has emerged as a promising additional diagnostic tool in patients with suspected myocarditis: cMRI not only provides important insights into structural and functional abnormalities of the heart but relevant tissue pathologies can also be visualized. The diagnostic accuracy of three tissue criteria, i.e. the edema ratio, early gadolinium enhancement ratio and late gadolinium enhancement, has been characterized in several studies. Endomyocardial biopsy (EMB) is widely considered to be the reference standard for diagnosis of myocarditis. Although limited by sampling error, EMB is the only diagnostic procedure that can be used to confirm myocarditis. Laboratory analyses of EMB may provide information about specific causes of myocarditis and are, at least in part, of prognostic relevance. In a subset of patients the results of EMB may guide therapeutic decision-making. Additional efforts are needed in cardiac imaging, molecular characterization of EMB and evaluation of serum biomarkers to improve the diagnostic work-up in patients with suspected myocarditis and to identify potential novel targets for a cause-specific therapy of myocarditis.