The Role of the Immune System in Pathobiology and Therapy of Myocarditis: A Review.

The role of the immune system in myocarditis onset and progression involves a range of complex cellular and molecular pathways. Both innate and adaptive immunity contribute to myocarditis pathogenesis, regardless of its infectious or non-infectious nature and across different histological and clinical subtypes. The heterogeneity of myocarditis etiologies and molecular effectors is one of the determinants of its clinical variability, manifesting as a spectrum of disease phenotype and progression. This spectrum ranges from a fulminant presentation with spontaneous recovery to a slowly progressing, refractory heart failure with ventricular dysfunction, to arrhythmic storm and sudden cardiac death. In this review, we first examine the updated definition and classification of myocarditis at clinical, biomolecular and histopathological levels. We then discuss recent insights on the role of specific immune cell populations in myocarditis pathogenesis, with particular emphasis on established or potential therapeutic applications. Besides the well-known immunosuppressive agents, whose efficacy has been already demonstrated in human clinical trials, we discuss the immunomodulatory effects of other drugs commonly used in clinical practice for myocarditis management. The immunological complexity of myocarditis, while presenting a challenge to simplistic understanding, also represents an opportunity for the development of different therapeutic approaches with promising results.

Long-term efficacy and safety of tailored immunosuppressive therapy in immune-mediated biopsy-proven myocarditis: A propensity-weighted study.

AIMS: Standardized immunosuppressive therapy (IS) had been previously investigated in biopsy-proven (BP) lymphocytic myocarditis with heart failure (HF). This study evaluated efficacy and safety of tailored IS in BP immune-mediated myocarditis, irrespective of histology and clinical presentation. METHODS AND RESULTS: Consecutive BP myocarditis patients treated with long-term tailored IS on top of optimal medical therapy (OMT), were compared with OMT non-IS controls using propensity-score weighting. The primary outcome was a composite of death or heart transplant, the secondary outcome was a composite of biventricular function, New York Heart Association (NYHA) class variation, and relapse. IS was managed by a multidisciplinary Cardioimmunology Team, involved a safety checklist and active patients' education. Ninety-one IS patients were compared with 267 non-IS patients. IS patients more frequently had systemic immune-mediated diseases (35% vs. 9.7%), lower baseline echocardiographic left ventricular ejection fraction (35% vs. 43%), lower right ventricular fractional area change (34% vs. 41%) and higher frequency of active lymphocytic, eosinophilic and giant cell myocarditis (71% vs. 58%, 12% vs. 1.1%, and 6.6% vs. 1.5%, respectively). At 5-year follow up, no difference was observed in the primary outcome (survival rate 93% in IS vs. 87% in non-IS), but IS patients had a higher relapse rate. Thus, IS patients, with a lower biventricular function and a higher risk profile at baseline, presented similar biventricular function and NYHA class to non-IS patients at follow-up. Minor adverse drug reactions occurred in 13% of patients, all resolved with therapy switch. CONCLUSIONS: Prolonged tailored IS is effective and safe in BP immune-mediated myocarditis irrespective of histology and clinical presentation.

CMR Predictors of Favorable Outcome in Myocarditis: A Single-Center Experience.

Background: Cardiovascular magnetic resonance (CMR) has emerged as the most accurate, non-invasive method to support the diagnosis of clinically suspected myocarditis and as a risk-stratification tool in patients with cardiomyopathies. We aim to assess the diagnostic and prognostic role of CMR at diagnosis in patients with myocarditis. Methods: We enrolled consecutive single-center patients with 2013 ESC consensus-based endomyocardial biopsy (EMB)-proven or clinically suspected myocarditis undergoing CMR at diagnosis. The pre-specified outcome was defined as NYHA class > I and echocardiographic left ventricular ejection fraction (LVEF) < 50% at follow-up. Results: We included 207 patients (74% male, median age 36 years; 25% EMB-proven). CMR showed the highest sensitivity in myocarditis with infarct-like presentation. Patients with EMB-proven myocarditis were more likely to have diffuse LGE and right ventricular LGE (p < 0.001), which was also more common among patients with arrhythmic presentation (p = 0.001). The outcome was met in 17 patients at any follow-up time point, more commonly in those with larger biventricular volumes (p < 0.001), CMR-based diagnosis of dilated cardiomyopathy (p < 0.001), and ischemic LGE (p = 0.005). Higher biventricular systolic function (p < 0.001) and greater LGE extent (p = 0.033) at diagnosis had a protective effect. Conclusions: In our single-center cohort of rigorously defined myocarditis patients, higher biventricular systolic function and greater LGE extent on CMR at diagnosis identified patients with better functional class and higher left ventricular ejection fraction at follow-up. Conversely, larger biventricular volumes, CMR-based DCM features, and the presence of an ischemic LGE pattern at diagnosis were predictors of worse functional class and LV systolic dysfunction at follow-up. Larger prospective studies are warranted to extend our findings to multi-center cohorts.

Uneventful COVID-19 Infection and Vaccination in a Cohort of Patients with Prior Myocarditis.

Myocarditis has in rare cases been associated with COVID-19 infection and has emerged as a possible rare side effect of vaccination with anti-COVID-19 messenger RNA vaccines. However, little is known about possible COVID-19 infection- and/or vaccination-related myocarditis relapse in patients with previous clinically suspected or biopsy-proven myocarditis. Myocarditis may relapse, particularly in females with immune-mediated/autoimmune features and a predisposing immunogenetic background. We aimed to assess the prevalence of myocarditis relapse during the COVID-19 outbreak and following COVID-19 vaccination in a cohort of patients with prior myocarditis. We included in the analysis myocarditis patients on active follow-up, for whom COVID-19 infection and vaccination statuses were known, and collected data on clinical, laboratory and echocardiographic findings, and myocarditis relapse. We enrolled 409 patients, of whom 114 (28%) reported COVID-19 infection and 347 (85%) completed the vaccination scheme. Only one patient, having COVID-19 infection before the vaccination campaign started, was admitted to hospital because of pneumonia; the remaining patients had an uneventful COVID-19 infection course, with only mild symptoms. No myocarditis relapse was recorded following COVID-19 infection or vaccination. Moreover, the frequency of new myocarditis cases following the COVID-19 outbreak was not different compared to the three-year period preceding the COVID-19 era. In conclusion, in our cohort of patients with prior myocarditis, both COVID-19 infection and vaccination were uneventful.

Fulminant Myocarditis: When One Size Does Not Fit All - A Critical Review of the Literature.

Fulminant myocarditis, rather than being a distinct form of myocarditis, is instead a peculiar clinical presentation of the disease. The definition of fulminant myocarditis has varied greatly in the last 20 years, leading to conflicting reports on prognosis and treatment strategies, mainly because of varied inclusion criteria in different studies. The main conclusion of this review is that fulminant myocarditis may be due to different histotypes and aetiologies that can be diagnosed only by endomyocardial biopsy and managed by aetiology-directed treatment. This life-threatening presentation requires rapid, targeted management both in the short term (mechanical circulatory support, inotropic and antiarrhythmic treatment and endomyocardial biopsy) and in the long term (including prolonged follow-up). Fulminant presentation has also recently been identified as a risk factor for worsened prognosis, even long after the resolution of the acute phase of myocarditis.

Transient pericardial constriction: A not so rare entity.

Constrictive pericarditis is a rare, potentially treatable, cause of heart failure with preserved ejection fraction that is characterized by insidious onset, challenging diagnosis and dismal prognosis, even following complete surgical pericardiectomy, particularly in advanced disease stages. In recent years it has been proposed that transient pericardial constriction may occur, with an even rarer frequency, during early phases of acute pericarditis and may resolve following specific treatment without progressing to the chronic, irreversible form. We recently observed two cases of well-documented transient pericardial constriction. In the present work we describe these two cases and provide a review on this rare condition, that, if unrecognized and left untreated, may lead to irreversible constrictive pericarditis.

Myocarditis: Etiology, Pathogenesis, and Their Implications in Clinical Practice.

Myocarditis is an inflammatory disease of the myocardium caused by infectious or non-infectious agents. It can lead to serious short-term and long-term sequalae, such as sudden cardiac death or dilated cardiomyopathy. Due to its heterogenous clinical presentation and disease course, challenging diagnosis and limited evidence for prognostic stratification, myocarditis poses a great challenge to clinicians. As it stands, the pathogenesis and etiology of myocarditis is only partially understood. Moreover, the impact of certain clinical features on risk assessment, patient outcomes and treatment options is not entirely clear. Such data, however, are essential in order to personalize patient care and implement novel therapeutic strategies. In this review, we discuss the possible etiologies of myocarditis, outline the key processes governing its pathogenesis and summarize best available evidence regarding patient outcomes and state-of-the-art therapeutic approaches.

Immunosuppressive Therapy of Biopsy-Proven, Virus-Negative, Autoimmune/Immune-Mediated Myocarditis-Focus on Azathioprine: A Review of Existing Evidence and Future Perspectives.

The use of immunosuppressive therapy (IT) in biopsy-proven, autoimmune/immune-mediated (AI), virus-negative myocarditis has become the standard of care. In particular, according to recent guidelines, azathioprine (AZA), in association with steroids, is a cornerstone of first-line therapy regimens. IT may have a crucial impact on the natural history of AI myocarditis, preventing its progression to end-stage heart failure, cardiovascular death, or heart transplantation, provided that strict appropriateness and safety criteria are observed. In particular, AZA treatment for AI virus-negative myocarditis requires the consideration of some crucial aspects regarding its pharmacokinetics and pharmacodynamics, as well as a high index of suspicion to detect its overt and/or subclinical side effects. Importantly, besides a tight teamwork with a clinical immunologist/immuno-rheumatologist, before starting IT, it is also necessary to carry out a careful "safety check-list" in order to rule out possible contraindications to IT and minimize patient's risk. The aim of this review is to describe the pharmacological properties of AZA, as well as to discuss practical aspects of its clinical use, in the light of existing evidence, with particular regard to the new field of cardioimmunology.

A Machine-Learning Model for the Prognostic Role of C-Reactive Protein in Myocarditis.

Aims: The role of inflammation markers in myocarditis is unclear. We assessed the diagnostic and prognostic correlates of C-reactive protein (CRP) at diagnosis in patients with myocarditis. Methods and results: We retrospectively enrolled patients with clinically suspected (CS) or biopsy-proven (BP) myocarditis, with available CRP at diagnosis. Clinical, laboratory and imaging data were collected at diagnosis and at follow-up visits. To evaluate predictors of death/heart transplant (Htx), a machine-learning approach based on random forest for survival data was employed. We included 409 patients (74% males, aged 37 ± 15, median follow-up 2.9 years). Abnormal CRP was reported in 288 patients, mainly with CS myocarditis (p < 0.001), recent viral infection, shorter symptoms duration (p = 0.001), chest pain (p < 0.001), better functional class at diagnosis (p = 0.018) and higher troponin I values (p < 0.001). Death/Htx was reported in 13 patients, of whom 10 had BP myocarditis (overall 10-year survival 94%). Survival rates did not differ according to CRP levels (p = 0.23). The strongest survival predictor was LVEF, followed by anti-nuclear auto-antibodies (ANA) and BP status. Conclusions: Raised CRP at diagnosis identifies patients with CS myocarditis and less severe clinical features, but does not contribute to predicting survival. Main death/Htx predictors are reduced LVEF, BP diagnosis and positive ANA.

Predictors of relapse, death or heart transplantation in myocarditis before the introduction of immunosuppression: negative prognostic impact of female gender, fulminant onset, lower ejection fraction and serum autoantibodies.

AIMS: Outcome predictors in myocarditis are not well defined; we aimed at identifying predictors of death, heart transplantation (HTx) and relapse before the introduction of immunosuppression. METHODS AND RESULTS: From 1992 to 2012, 466 consecutive patients (68% male, mean age 37 ± 17 years, single centre recruitment, median follow-up 50 months) were included, of whom 216 had clinically suspected and 250 biopsy-proven myocarditis. Serum anti-heart (AHA) and anti-intercalated disk (AIDA) autoantibodies were measured by indirect immunofluorescence. Univariable and multivariable analyses of clinical and diagnostic features at diagnosis were performed. Survival free from death or HTx at 10 years was 83% in the whole study population and was lower in biopsy-proven versus clinically suspected myocarditis (76% vs. 94%, p < 0.001). Female gender (hazard ratio [HR] 2.7, 95% confidence interval [CI] 1.1-6.5), fulminant presentation (HR 13.77, 95% CI 9.7-261.73), high-titre organ-specific AHA (HR 4.2, 95% CI 1.2-14.7) and anti-nuclear antibodies (ANA) (HR 5.2, 95% CI 2.1-12.8) were independent predictors of death or HTx; higher echocardiographic left ventricular ejection fraction (LVEF) at diagnosis was protective, with a 0.93-fold risk reduction for each 1% LVEF increase (95% CI 0.89-0.96). History of myocarditis at diagnosis (HR 8.5, 95% CI 3.5-20.7) was an independent predictor of myocarditis relapse at follow-up; older age was protective (HR 0.95, 95% CI 0.91-0.99). Predictors of death, HTx and relapse did not differ in biopsy-proven versus clinically suspected myocarditis. CONCLUSIONS: Young age and a previous myocarditis were independent relapse predictors; female gender, fulminant onset, lower LVEF at presentation and high-titre organ-specific AHA and ANA were independent predictors of death and HTx, suggesting that autoimmune features predict worse prognosis.

Myocarditis in systemic immune-mediated diseases: Prevalence, characteristics and prognosis. A systematic review.

Many systemic immune-mediated diseases (SIDs) may involve the heart and present as myocarditis with different histopathological pictures, i.e. lymphocytic, eosinophilic, granulomatous, and clinical features, ranging from a completely asymptomatic patient to life-threatening cardiogenic shock or arrhythmias. Myocarditis can be part of some SIDs, such as sarcoidosis, systemic lupus erythematosus, systemic sclerosis, antiphospholipid syndrome, dermato-polymyositis, eosinophilic granulomatosis with polyangiitis and other vasculitis syndromes, but also of some organ-based immune-mediated diseases with systemic expression, such as chronic inflammatory bowel diseases. The aim of this review is to describe the prevalence, main clinical characteristics and prognosis of myocarditis associated with SIDs.