Cardiomyopathy in First-Degree Relatives of Patients Presenting With Acute Myocarditis: Prevalence and Prognostic Significance.

BACKGROUND: Acute myocarditis has been genetically linked to dilated cardiomyopathy (DCM), but the clinical significance remains uncertain. We investigated the prevalence and long-term prognosis of DCM and heart failure (HF) among unselected patients hospitalized with acute myocarditis and their first-degree relatives compared with an age- and sex-matched cohort. METHODS: This was an observational study utilizing the Danish nationwide registries, where all patients with a first-time myocarditis diagnosis from 1995 to 2018 were identified and matched (on birth year and sex) with 10 controls from the general population. RESULTS: Totally 3176 patients with acute myocarditis and 31 760 controls were included (median age, 49.8 [Q1-Q3, 32.5-70.2] years; 35.6% female). At baseline, patients with myocarditis had a higher prevalence of DCM (7 [0.2%] versus 8 [0.0%]) and HF (336 [10.6%] versus 695 [2.2%]) than controls; P<0.0001 for both. Patients with myocarditis more often had siblings with DCM (12 [0.4%] versus 17 [0.05%]) or HF (36 [1.1%] versus 89 [0.3%]); P<0.0001, odds ratios 7.09 (3.38-14.85) and 2.92 (1.25-6.80), respectively, whereas parental DCM and HF did not differ among patients with myocarditis and controls. Patients with myocarditis had greater 20-year incidence of DCM, HF, and all-cause mortality (0.5% [0.3%-0.9%], 15% [13%-17%], and 47% [44%-50%]) compared with controls (0.06% [0.03%-0.11%], 6.8% [6.4%-7.3%], and 34% [33%-35%]; P<0.0001). Having a first-degree relative with DCM or HF was associated with increased long-term mortality among the patients with myocarditis (hazard ratio, 1.40 [1.11-1.77]) but not among the controls (hazard ratio, 0.90 [0.81-1.01]; Pdifference=0.0008). CONCLUSIONS: Acute myocarditis aggregates with DCM within families, where it carries a worsened prognosis. A differential association between parents and siblings (with sibling preponderance) could suggest that additional environmental factors are important for myocarditis development even in predisposed individuals.

Rationale and design of the French cohort of acute myocarditis diagnosed by cardiac magnetic resonance imaging (MyocarditIRM).

BACKGROUND: Acute myocarditis usually presents as chest pain with rising troponin and normal coronary arteries. Despite frequent favourable evolution at the acute phase, it is associated with heart failure and ventricular rhythm disorders, and is considered the leading cause of sudden cardiac death in young, apparently healthy, adults. There are no specific recommendations for acute myocarditis diagnosis and management, only expert consensus, given the lack of large databases. AIM: The main objective is to describe the contemporary presentation of acute myocarditis, its management and in-hospital outcomes. Secondary objectives are to investigate survival and event-free survival for up to 10years of follow-up, the determinants of prognosis, the modalities of treatment and follow-up and the gaps between expert consensus and real-life management. METHODS: MyocarditIRM is a prospective multicentre cohort that enrolled 803 consecutive patients with acute myocarditis in 49 participating centres in France between 01 May 2016 and 28 February 2019. The diagnosis of acute myocarditis was acknowledged by cardiac magnetic resonance, using the Lake Louise Criteria. Exclusion criteria were age<18years, lack of health coverage, contraindication to cardiac magnetic resonance and refusal to participate. Detailed information was collected prospectively, starting at admission. Cardiac magnetic resonance imaging (diagnosis and follow-up) is analysed centrally by the certified core laboratory IHU ICAN. Ten years of follow-up for each patient is ensured by linking with the French National Health Database, and includes information on death, hospital admissions, major clinical events and drug consumption. CONCLUSION: This prospective cohort with long-term follow-up represents the largest database on acute myocarditis worldwide, and will improve knowledge about its presentation, management and outcomes.

Endomyocardial biopsy: safety and prognostic utility in paediatric and adult myocarditis in the European Society of Cardiology EURObservational Research Programme Cardiomyopathy and Myocarditis Long-Term Registry.

BACKGROUND AND AIMS: Contemporary multicentre data on clinical and diagnostic spectrum and outcome in myocarditis are limited. Study aims were to describe baseline features, 1-year follow-up, and baseline predictors of outcome in clinically suspected or biopsy-proven myocarditis (2013 European Society of Cardiology criteria) in adult and paediatric patients from the EURObservational Research Programme Cardiomyopathy and Myocarditis Long-Term Registry. METHODS: Five hundred eighty-one (68.0% male) patients, 493 adults, median age 38 (27-52) years, and 88 children, aged 8 (3-13) years, were divided into 3 groups: Group 1 (n = 233), clinically suspected myocarditis with abnormal cardiac magnetic resonance; Group 2 (n = 222), biopsy-proven myocarditis; and Group 3 (n = 126) clinically suspected myocarditis with normal or inconclusive or no cardiac magnetic resonance. Baseline features were analysed overall, in adults vs. children, and among groups. One-year outcome events included death/heart transplantation, ventricular assist device (VAD) or implantable cardioverter defibrillator (ICD) implantation, and hospitalization for cardiac causes. RESULTS: Endomyocardial biopsy, mainly right ventricular, had a similarly low complication rate in children and adults (4.7% vs. 4.9%, P = NS), with no procedure-related death. A classical myocarditis pattern on cardiac magnetic resonance was found in 31.3% of children and in 57.9% of adults with biopsy-proven myocarditis (P < .001). At 1-year follow-up, 11/410 patients (2.7%) died, 7 (1.7%) received a heart transplant, 3 underwent VAD (0.7%), and 16 (3.9%) underwent ICD implantation. Independent predictors at diagnosis of death or heart transplantation or hospitalization or VAD implantation or ICD implantation at 1-year follow-up were lower left ventricular ejection fraction and the need for immunosuppressants for new myocarditis diagnosis refractory to non-aetiology-driven therapy. CONCLUSIONS: Endomyocardial biopsy was safe, and cardiac magnetic resonance using Lake Louise criteria was less sensitive, particularly in children. Virus-negative lymphocytic myocarditis was predominant both in children and adults, and use of immunosuppressive treatments was low. Lower left ventricular ejection fraction and the need for immunosuppressants at diagnosis were independent predictors of unfavourable outcome events at 1 year.

Multisystemic Inflammation Influences Prognosis in Fulminant Lymphocytic Myocarditis.

BACKGROUND: Multisystem inflammatory syndrome (MIS) is a hyperinflammatory shock associated with cardiac dysfunction and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, there are no reports on using MIS criteria, such as multisystemic inflammation (MSI) in fulminant myocarditis, without SARS-CoV-2 infection. This study investigated the differences in clinical characteristics and course between patients with fulminant lymphocytic myocarditis (FLM) plus MSI and those without MSI.Methods and Results: This multicenter retrospective cohort study included 273 patients with FLM registered in the JROAD-DPC database between April 2014 and March 2017. We evaluated the presence of MSI using criteria modified from previously reported MIS criteria and compared the characteristics and risk of mortality or heart transplantation between FLM patients with MSI and without MSI. Of the 273 patients with FLM, 107 (39%) were diagnosed with MSI. The MSI group was younger (44 vs. 57 years; P<0.0001) and had more females (50% vs. 36%; P=0.0236), a higher incidence of pericardial effusion (58% vs. 40%; P=0.0073), and a lower 90-day mortality rate (19% vs. 33%; P=0.0185) than the non-MSI group. The risk of mortality at 90 days was lower in FLM patients aged <50 years with MSI aged <50 years than in those without MSI (P=0.0463). CONCLUSIONS: These results suggest that MSI may influence the prognosis of FLM, especially in patients aged <50 years.

Prognostic value of visual and quantitative CMR regional myocardial function in patients with suspected myocarditis.

According to updated Lake-Louise Criteria, impaired regional myocardial function serves as a supportive criterion in diagnosing myocarditis. This study aimed to assess visual regional wall motional abnormalities (RWMA) and novel quantitative regional longitudinal peak strain (RLS) for risk stratification in the clinical setting of myocarditis. In patients undergoing CMR and meeting clinical criteria for suspected myocarditis global longitudinal strain (GLS), late gadolinium enhancement (LGE), RWMA and RLS were assessed in the anterior, septal, inferior, and lateral regions and correlated to the occurrence of major adverse cardiac events (MACE), including heart failure hospitalization, sustained ventricular tachycardia, recurrent myocarditis, and all-cause death. In 690 consecutive patients (age: 48.0 ± 16.0 years; 37.7% female) with suspected myocarditis impaired RLS was correlated with RWMA and LV-GLS but not with the presence of LGE. At median follow up of 3.8 years, MACE occurred in 116 (16.8%) patients. Both, RWMA and RLS in anterior-, septal-, inferior-, and lateral- locations were univariately associated with outcomes (all p < 0.001), but not after adjusting for clinical characteristics and LV-GLS. In the subgroup of patients with normal LV function, RWMA were not predictive of outcomes, whereas septal RLS had incremental and independent prognostic value over clinical characteristics (HRadjusted = 1.132, 95% CI 1.020-1.256; p = 0.020). RWMA and RLS can be used to assess regional impairment of myocardial function in myocarditis but are of limited prognostic value in the overall population. However, in the subgroup of patients with normal LV function, septal RLS represents a distinctive marker of regional LV dysfunction, offering potential for risk-stratification.

[Asymptomatic SARS-CoV-2 Infection and "in situ split" Liver Resection with Fatal Outcome - A Case Report]. / SARS-CoV-2-Infektion und "In-situ-Split"-Leberresektion mit tödlichem Verlauf.

We report the perioperative course of a 47-year-old patient who underwent a two-stage liver resection for bilobar metastatic colorectal carcinoma. The respiratory asymptomatic patient was tested positive for SARS-CoV-2 by PCR detection one day before the second surgical procedure. Postoperatively, the patient suffered cardiovascular arrest on postoperative day 8 and died despite immediately initiated resuscitative measures. With an initial clinical suspicion of vascular liver failure, postmortem pathologic examination revealed the underlying cause of death to be COVID-19-related myocarditis with acute right heart failure. Individual multidisciplinary risk assessment should be considered very critically when deviating from the "7-week rule" because the benefit is difficult to objectify, even in oncologic patients.

T cells specific for α-myosin drive immunotherapy-related myocarditis.

Immune-related adverse events, particularly severe toxicities such as myocarditis, are major challenges to the utility of immune checkpoint inhibitors (ICIs) in anticancer therapy1. The pathogenesis of ICI-associated myocarditis (ICI-MC) is poorly understood. Pdcd1-/-Ctla4+/- mice recapitulate clinicopathological features of ICI-MC, including myocardial T cell infiltration2. Here, using single-cell RNA and T cell receptor (TCR) sequencing of cardiac immune infiltrates from Pdcd1-/-Ctla4+/- mice, we identify clonal effector CD8+ T cells as the dominant cell population. Treatment with anti-CD8-depleting, but not anti-CD4-depleting, antibodies improved the survival of Pdcd1-/-Ctla4+/- mice. Adoptive transfer of immune cells from mice with myocarditis induced fatal myocarditis in recipients, which required CD8+ T cells. The cardiac-specific protein α-myosin, which is absent from the thymus3,4, was identified as the cognate antigen source for three major histocompatibility complex class I-restricted TCRs derived from mice with fulminant myocarditis. Peripheral blood T cells from three patients with ICI-MC were expanded by α-myosin peptides. Moreover, these α-myosin-expanded T cells shared TCR clonotypes with diseased heart and skeletal muscle, which indicates that α-myosin may be a clinically important autoantigen in ICI-MC. These studies underscore the crucial role for cytotoxic CD8+ T cells, identify a candidate autoantigen in ICI-MC and yield new insights into the pathogenesis of ICI toxicity.

Trends in myocarditis incidence, complications and mortality in Sweden from 2000 to 2014.

Investigate trends in myocarditis incidence and prognosis in Sweden during 2000-2014. Little data exist concerning population-trends in incidence of hospitalizations for myocarditis and subsequent prognosis. Linking Swedish National Patient and Cause of Death Registers, we identified individuals ≥ 16 years with first-time diagnosis of myocarditis during 2000-2014. Reference population, matched for age and birth year (n = 16,622) was selected from Swedish Total Population Register. Among the 8 679 cases (75% men, 64% < 50 years), incidence rate/100,000 inhabitants rose from 6.3 to 8.6 per 100,000, mostly in men and those < 50 years. Incident heart failure/dilated cardiomyopathy occurred in 6.2% within 1 year after index hospitalization and in 10.2% during 2000-2014, predominantly in those ≥ 50 years (12.1% within 1 year, 20.8% during 2000-2014). In all 8.1% died within 1 year, 0.9% (< 50 years) and 20.8% (≥ 50 years). Hazard ratios (adjusted for age, sex) for 1-year mortality comparing cases and controls were 4.00 (95% confidence interval 1.37-11.70), 4.48 (2.57-7.82), 4.57 (3.31-6.31) and 3.93 (3.39-4.57) for individuals aged < 30, 30 to < 50, 50 to < 70, and ≥ 70 years, respectively. The incidence of myocarditis during 2000-2014 increased, predominantly in men < 50 years. One-year mortality was low, but fourfold higher compared with reference population.

Systematic analysis of drug-associated myocarditis reported in the World Health Organization pharmacovigilance database.

While multiple pharmacological drugs have been associated with myocarditis, temporal trends and overall mortality have not been reported. Here we report the spectrum and main features of 5108 reports of drug-induced myocarditis, in a worldwide pharmacovigilance analysis, comprising more than 21 million individual-case-safety reports from 1967 to 2020. Significant association between myocarditis and a suspected drug is assessed using disproportionality analyses, which use Bayesian information component estimates. Overall, we identify 62 drugs associated with myocarditis, 41 of which are categorized into 5 main pharmacological classes: antipsychotics (n = 3108 reports), salicylates (n = 340), antineoplastic-cytotoxics (n = 190), antineoplastic-immunotherapies (n = 538), and vaccines (n = 790). Thirty-eight (61.3%) drugs were not previously reported associated with myocarditis. Antipsychotic was the first (1979) and most reported class (n = 3018). In 2019, the two most reported classes were antipsychotics (54.7%) and immunotherapies (29.5%). Time-to-onset between treatment start and myocarditis is 15 [interquartile range: 10; 23] days. Subsequent mortality is 10.3% and differs between drug classes with immunotherapies the highest, 32.5% and salicylates the lowest, 2.6%. These elements highlight the diversity of presentations of myocarditis depending on drug class, and show the emerging role of antineoplastic drugs in the field of drug-induced myocarditis.

The M2 Gene Is a Determinant of Reovirus-Induced Myocarditis.

Although a broad range of viruses cause myocarditis, the mechanisms that underlie viral myocarditis are poorly understood. Here, we report that the M2 gene is a determinant of reovirus myocarditis. The M2 gene encodes outer capsid protein µ1, which mediates host membrane penetration during reovirus entry. We infected newborn C57BL/6 mice with reovirus strain type 1 Lang (T1L) or a reassortant reovirus in which the M2 gene from strain type 3 Dearing (T3D) was substituted into the T1L genetic background (T1L/T3DM2). T1L was nonlethal in wild-type mice, whereas more than 90% of mice succumbed to T1L/T3DM2 infection. T1L/T3DM2 produced higher viral loads than T1L at the site of inoculation. In secondary organs, T1L/T3DM2 was detected with more rapid kinetics and reached higher peak titers than T1L. We found that hearts from T1L/T3DM2-infected mice were grossly abnormal, with large lesions indicative of substantial inflammatory infiltrate. Lesions in T1L/T3DM2-infected mice contained necrotic cardiomyocytes with pyknotic debris, as well as extensive lymphocyte and histiocyte infiltration. In contrast, T1L induced the formation of small purulent lesions in a small subset of animals, consistent with T1L being mildly myocarditic. Finally, more activated caspase-3-positive cells were observed in hearts from animals infected with T1L/T3DM2 than T1L. Together, our findings indicate that substitution of the T3D M2 allele into an otherwise T1L genetic background is sufficient to change a nonlethal infection into a lethal infection. Our results further indicate that T3D M2 enhances T1L replication and dissemination in vivo, which potentiates the capacity of reovirus to cause myocarditis. IMPORTANCE Reovirus is a nonenveloped virus with a segmented double-stranded RNA genome that serves as a model for studying viral myocarditis. The mechanisms by which reovirus drives myocarditis development are not fully elucidated. We found that substituting the M2 gene from strain type 3 Dearing (T3D) into an otherwise type 1 Lang (T1L) genetic background (T1L/T3DM2) was sufficient to convert the nonlethal T1L strain into a lethal infection in neonatal C57BL/6 mice. T1L/T3DM2 disseminated more efficiently and reached higher maximum titers than T1L in all organs tested, including the heart. T1L is mildly myocarditic and induced small areas of cardiac inflammation in a subset of mice. In contrast, hearts from mice infected with T1L/T3DM2 contained extensive cardiac inflammatory infiltration and more activated caspase-3-positive cells, which is indicative of apoptosis. Together, our findings identify the reovirus M2 gene as a new determinant of reovirus-induced myocarditis.

The absolute and relative changes in high-sensitivity cardiac troponin I are associated with the in-hospital mortality of patients with fulminant myocarditis.

BACKGROUND: We sought to describe the tendency and extent of high-sensitivity cardiac troponin I (hs-cTnI) changes in patients with fulminant myocarditis (FM) after admission and to explore the relationship between the in-hospital mortality of FM and the absolute and relative changes in hs-cTnI within 24 h and 48 h after admission. METHODS: In the retrospective study, the object are patients diagnosed with FM in our single centre. The value of cardiac troponin was recorded after patients admitted to hospital in succession. The absolute and relative changes in hs-cTnI within 24 h and 48 h were described as range distributions. Receiver operating characteristic (ROC) curve and Cox analyses were performed to determine the relationship between in-hospital mortality of FM and hs-cTnI changes. RESULTS: A total of 83 FM patients admitted to our centre from January 1, 2010 to December 31, 2019 were included; 69 patients survived and 14 patients died. In the survival group, 78% of patients experienced a decline in hs-cTnI within 24 h, while 36% of the mortality group exhibited a declining tendency in hs-cTnI (P = 0.003). Nearly 60% of survival group had a 0-2000 ng/l reduction in troponin from baseline within 24 h of admission. However, troponin levels of 50% of patients in the mortality group were 0-10,000 ng/ L higher than baseline 24 h after admission. Multivariable logistic analysis revealed that the declining tendency of hs-cTnI within 24 h, in addition to time from onset to admittance to hospital, intravenous immunoglobulin treatment and the abnormal level of creatinine, were associated with the in-hospital mortality of FM (for the declining tendency of hs-cTnI within 24 h, OR = 0.10, 95% CI 0.02-0.68, P = 0.018). The ROC curve revealed optimal cut-off values of - 618 ng/l for absolute change within 24 h (AUC = 0.800, P < 0.01), - 4389 ng/l for absolute change within 48 h (area under the curve = 0.711, P < 0.01), - 28.46% for relative change within 24 h (AUC = 0.810, P < 0.01), and - 52.23% for relative change within 48 h (AUC = 0.795, P < 0.01). Absolute changes and relative changes in hs-cTnI within 24 h and 48 h were strong predictors of in-hospital mortality by Cox regression analysis after adjustment for sex, time from onset to admission, and occurrence of ventricular tachycardia or ventricular fibrillation. CONCLUSION: Most FM patients who survived experienced a decline in hs-cTnI within 24 h. The absolute and relative changes in hs-cTnI within 24 h and 48 h were strong predictors of in-hospital mortality.

Mortality and ventricular arrhythmia after acute myocarditis: a nationwide registry-based follow-up study.

OBJECTIVE: Incidence and severity of acute myocarditis vary significantly in previous reports and there is a lack of epidemiological studies on the short-term risks of mortality, heart failure and ventricular arrhythmias in patients with acute myocarditis. Therefore, study aims were to examine 90-day risks of mortality, heart failure (HF) and ventricular arrhythmias in patients with acute myocarditis in comparison to age-matched and sex-matched background population controls. METHODS: In this nationwide register-based follow-up study of patients hospitalised with myocarditis between 2002 and 2018 in Denmark, 90-day risks of all-cause mortality, HF, ventricular arrhythmias (ventricular tachycardia, ventricular fibrillation (VF)), cardiac arrest and implantable cardioverter-defibrillator (ICD) implantation were compared with age-matched and sex-matched controls from the background population (1:5 matching). Absolute risks standardised to the age, sex and comorbidity distribution of the entire study population were derived from multivariable Cox regression. RESULTS: A total of 2523 patients hospitalised with myocarditis were included. Median age was 48 years (Q1-Q3: 30-69) and 67.7% were men. Comorbidity burden was more pronounced among patients with myocarditis relative to controls. Standardised 90-day all-cause mortality risk was 4.9% for patients with acute myocarditis versus 0.3% for controls (p<0.001). Ninety-day standardised risks for other endpoints were 7.5% versus 0.1% for HF, 1.9% versus <0.1% for VF/VF/arrest risk and 1.6% versus <0.1% for ICD implantation (all p<0.001). CONCLUSIONS: In this large nationwide register-based follow-up study, patients hospitalised with myocarditis had significantly higher 90-day risks of all-cause mortality, HF, ventricular arrhythmias, cardiac arrest and ICD implantation compared with background population controls.

Postmortem investigation of fatalities following vaccination with COVID-19 vaccines.

Thorough postmortem investigations of fatalities following vaccination with coronavirus disease 2019 (COVID-19) vaccines are of great social significance. From 11.03.2021 to 09.06.2021, postmortem investigations of 18 deceased persons who recently received a vaccination against COVID-19 were performed. Vaxzevria was vaccinated in nine, Comirnaty in five, Spikevax in three, and Janssen in one person. In all cases, full autopsies, histopathological examinations, and virological analyses for the severe acute respiratory syndrome coronavirus 2 were carried out. Depending on the case, additional laboratory tests (anaphylaxis diagnostics, VITT [vaccine-induced immune thrombotic thrombocytopenia] diagnostics, glucose metabolism diagnostics) and neuropathological examinations were conducted. In 13 deceased, the cause of death was attributed to preexisting diseases while postmortem investigations did not indicate a causal relationship to the vaccination. In one case after vaccination with Comirnaty, myocarditis was found to be the cause of death. A causal relationship to vaccination was considered possible, but could not be proven beyond doubt. VITT was found in three deceased persons following vaccination with Vaxzevria and one deceased following vaccination with Janssen. Of those four cases with VITT, only one was diagnosed before death. The synopsis of the anamnestic data, the autopsy results, laboratory diagnostic examinations, and histopathological and neuropathological examinations revealed that VITT was the very likely cause of death in only two of the four cases. In the other two cases, no neuropathological correlate of VITT explaining death was found, while possible causes of death emerged that were not necessarily attributable to VITT. The results of our study demonstrate the necessity of postmortem investigations on all fatalities following vaccination with COVID-19 vaccines. In order to identify a possible causal relationship between vaccination and death, in most cases an autopsy and histopathological examinations have to be combined with additional investigations, such as laboratory tests and neuropathological examinations.

Burden of Cardiomyopathic Genetic Variation in Lethal Pediatric Myocarditis.

BACKGROUND: Acute myocarditis (AM) is a well-known cause of sudden death and heart failure, often caused by prevalent viruses. We previously showed that some pediatric AM correlates with putatively damaging variants in genes related to cardiomyocyte structure and function. We sought to evaluate whether deleterious cardiomyopathic variants were enriched among fatal pediatric AM cases in New York City compared with ancestry-matched controls. METHODS: Twenty-four children (aged 3 weeks to 20 years) with death due to AM were identified through autopsy records; histologies were reviewed to confirm that all cases met Dallas criteria for AM and targeted panel sequencing of 57 cardiomyopathic genes was performed. Controls without cardiovascular disease were identified from a pediatric database and matched by genetic ancestry to cases using principal components from exome sequencing. Rates of putative deleterious variations (DV) were compared between cases and controls. Where available, AM tissues underwent viral analysis by polymerase chain reaction. RESULTS: DV were identified in 4 of 24 AM cases (16.7%), compared with 2 of 96 age and ancestry-matched controls (2.1%, P=0.014). Viral causes were proven for 6 of 8 AM cases (75%), including the one DV+ case where tissue was available for testing. DV+ cases were more likely to be female, have no evidence of chronic inflammation, and associate with sudden cardiac death than DV- cases. CONCLUSIONS: Deleterious variants in genes related to cardiomyocyte integrity are more common in children with fatal AM than controls, likely conferring susceptibility. Additionally, genetically mediated AM may progress more rapidly and be more severe.

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.

Pathogenic Variants Associated With Dilated Cardiomyopathy Predict Outcome in Pediatric Myocarditis.

BACKGROUND: Myocarditis is one of the most common causes leading to heart failure in children and a possible genetic background has been postulated. We sought to characterize the clinical and genetic characteristics in patients with myocarditis ≤18 years of age to predict outcome. METHODS: A cohort of 42 patients (Genetics in Pediatric Myocarditis) with biopsy-proven myocarditis underwent genetic testing with targeted panel sequencing of cardiomyopathy-associated genes. Genetics in Pediatric Myocarditis patients were divided into subgroups according to the phenotype of dilated cardiomyopathy (DCM) at presentation, resulting in 22 patients without DCM (myocarditis without phenotype of DCM) and 20 patients with DCM (myocarditis with phenotype of DCM). RESULTS: Myocarditis with phenotype of DCM patients (median age 1.4 years) were younger than myocarditis without phenotype of DCM patients (median age 16.1 years; P<0.001) and were corresponding to heart failure-like and coronary syndrome-like phenotypes, respectively. At least one likely pathogenic/pathogenic variant was identified in 9 out of 42 patients (22%), 8 of them were heterozygous, and 7 out of 9 were in myocarditis with phenotype of DCM. Likely pathogenic/pathogenic variants were found in genes validated for primary DCM (BAG3, DSP, LMNA, MYH7, TNNI3, TNNT2, and TTN). Rare variant enrichment analysis revealed significant accumulation of high-impact disease variants in myocarditis with phenotype of DCM versus healthy individuals (P=0.0003). Event-free survival was lower (P=0.008) in myocarditis with phenotype of DCM patients compared with myocarditis without phenotype of DCM and primary DCM. CONCLUSIONS: We report heterozygous likely pathogenic/pathogenic variants in biopsy-proven pediatric myocarditis. Myocarditis patients with DCM phenotype were characterized by early-onset heart failure, significant enrichment of likely pathogenic/pathogenic variants, and poor outcome. These phenotype-specific and age group-specific findings will be useful for personalized management of these patients. Genetic evaluation in children newly diagnosed with myocarditis and DCM phenotype is warranted.

[Cardiotoxicity of Anti-PD-L1 Antibody and the Effect of Levothyroxine 
in Attenuating the Related Mortality in Mice].

BACKGROUND: Immune checkpoint inhibitors (ICIs) such as antibodies against programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1), have shown remarkable efficacies in many subtypes of cancers. However, ICIs may also cause severe immune-related adverse events in the recipient patients. Recently, ICI-associated myocarditis have been reported in hundreds of patients worldwide, with a mortality rate of approximately 50% in these cases. This study aims to recapitulate the cardiotoxicity and explore the detoxicifying approaches to attenuate mortality caused by PD-1/PD-L1 inhibitors in healthy mice. METHODS: Six to eight-week-old C57BL/6 mice were inoculated with anti-PD-1 antibody (12.5 µg/g every 5 days for 6 injections), anti-PD-L1 antibody (10 µg/g once a week for 6 weeks), anti-PD-L1 antibody (with the same dosage described above) in combination with levothyroxine (0.25 µg/g, intraperitoneally injected half an hour before anti-PD-L1 antibody injection), or isotype control immunoglobulin IgG (10 µg/g once a week for 6 weeks). The ejection function of the hearts was detected by echocardiography, body temperature and blood pressure were detected by Mouse MonitorTM and non-invassive blood pressure minotor, and serum free thyroxine concentration was detected by The enzyme linked immunosorbent assay (ELISA). RESULTS: PD-L1 was expressed at different levels by the cardiomyocytes of the mice. The isotype control immunoglobulin and anti-PD-1 antibody did not cause death of the mice. The 12 mice receiving 3-6 injections of anti-PD-L1 antibody showed a significant increase in the heart-to-tibial ratio and cardiomyoctye degeneration, hyalinization and extravascular inflammatory cell infiltration. In addition, the serum thyroxine was mardedly decreased to 1/3 of that in the control group mice, and the blood pressure and body temperature were abnormally decreased in mice upon treatment with PD-L1 blockade. Eight of the 12 (66.7%) mice died from multiple intravenous injection of anti-PD-L1 antibody.Intraperitoneal injection of levothyroxine 30 min before the injection of anti-PD-L1 antibody significantly attenuated the mortality rate of the anti-PD-L1 antibody-treated mice. CONCLUSIONS: The anti-PD-L1 antibody is cardiotoxic and lethal, and levothyroxine is able to rescue the mice from this immune checkpoint inhibitor-caused mortality.

COVID-19 myocarditis: quantitative analysis of the inflammatory infiltrate and a proposed mechanism.

COVID-19 has a significant effect upon the cardiovascular system. While a number of different cardiovascular histopathologies have been described at post-mortem examination, the incidence of typical viral myocarditis in COVID-19 positive patients appears very low [1-3]. In this study, we further characterize and quantify the inflammatory cell infiltrate in a COVID-19 study cohort and compare the findings to both an age and disease matched control cohort and a cohort of patients diagnosed with typical inflammatory myocarditis. All study and control cohorts had 1 or more of the comorbidities most commonly associated with severe disease (hypertension, type II diabetes, obesity, or known cardiovascular disease). The results demonstrate a skewed distribution of the number of CD68+ cells in COVID-19 hearts, with upper quantiles showing a significant increase as compared to both matched control hearts, and those with myocarditis. In contrast, hearts from typical inflammatory myocarditis contained increased numbers of CD4+, and CD8+ cells compared to both COVID-19 and control cohorts. In conclusion, the presence of an increased number of CD68+ cells suggests that COVID-19 may incite a form of myocarditis different from typical viral myocarditis, and associated with diffusely infiltrative cells of monocytes/macrophage lineage.

The use of extracorporeal membrane oxygenation in the treatment of fulminant myocarditis: Current progress and clinical outcomes.

Myocarditis is an inflammatory condition of the myocardium and is usually categorised as acute nonfulminant and acute fulminant myocarditis. Myocardial injury can result via viral infections, direct injury or immune responses. Fulminant myocarditis can be characterised by severe and sudden cardiac inflammation that may result from cardiogenic shock, ventricular arrhythmias or multi-organ system failure. Extracorporeal membrane oxygenation (ECMO), also known as extracorporeal life support, is an effective technique for patients with fulminant myocarditis, providing heart and lung support and adequate gas exchange or perfusion to sustain life. Essentially, ECMO pumps blood out of the body to an oxygenator that acts as an artificial lung, which adds oxygen to the blood and removes carbon dioxide. This report aims to review recent advances in ECMO and relate case studies of fulminant myocarditis patients. The types of ECMO, predictive factors for success, clinical studies and recent technological advances in the field will be discussed.