Update on acute myocarditis

MicroRNAs Regulating Mitochondrial Function in Cardiac Diseases

Mitochondria are the key organelles that supply cellular energy. As the most active organ in the body, the energy required to maintain the mechanical function of the heart requires a high quantity of high-quality mitochondria in cardiomyocytes. MicroRNAs (miRNAs) are single-stranded noncoding RNAs, approximately 22 nt in length, which play key roles in mediating post-transcriptional gene silencing. Numerous studies have confirmed that miRNAs can participate in the occurrence and development of cardiac diseases by regulating mitochondrial function-related genes and signaling pathways. Therefore, elucidating the crosstalk that occurs between miRNAs and mitochondria is important for the prevention and treatment of cardiac diseases. In this review, we discuss the biogenesis of miRNAs, the miRNA-mediated regulation of major genes involved in the maintenance of mitochondrial function, and the effects of miRNAs on mitochondrial function in cardiac diseases in order to provide a theoretical basis for the clinical prevention and treatment of cardiac disease and the development of new drugs.

Myocardial infarction with non-obstructive coronary arteries (MINOCA) complicating myocarditis

Myocarditis can lead to myocardial infarction in the absence of coronary artery obstruction. We report a case of probable myocarditis, complicated by myocardial infarction with non-obstructive coronary arteries. A 19-year-old man presented with chest pain typical of myocarditis. He was a smoker but was otherwise well. Electrocardiogram revealed diffuse ST-elevation and echocardiography revealed a thin, akinetic apex. Troponin-T levels on admission were raised leading to an initial diagnosis of myocarditis being made. However, late gadolinium enhancement study on cardiac magnetic resonance imaging demonstrated transmural enhancement typical of ischaemia. Coronary angiogram was normal, leading to a likely diagnosis of myocardial infarction with non-obstructive coronary arteries. It is important to highlight that coronary assessment remains important when working up for myocarditis, as myocardial infarction with non-obstructive coronary arteries can often complicate myocarditis in cases of normal angiography. Another important lesson was on how cardiac magnetic resonance imaging provided vital evidence to support underlying ischaemia despite normal coronary angiogram, leading to a diagnosis of myocardial infarction with non-obstructive coronary arteries. Myocardial infarction with non-obstructive coronary arteries remains a broad ‘umbrella’ term and cardiac magnetic resonance imaging, as well as more invasive coronary imaging techniques during angiography, can further assist in its diagnosis. Our case provides a reminder that myocardial infarction with non-obstructive coronary arteries, although increasingly recognised, remains under-diagnosed and can often overlap with peri-myocarditis, highlighting the need to employ multi-modality imaging in guiding management.

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.

Immunomodulatory Role of Tenascin-C in Myocarditis and Inflammatory Cardiomyopathy

Accumulating evidence suggests that the breakdown of immune tolerance plays an important role in the development of myocarditis triggered by cardiotropic microbial infections. Genetic deletion of immune checkpoint molecules that are crucial for maintaining self-tolerance causes spontaneous myocarditis in mice, and cancer treatment with immune checkpoint inhibitors can induce myocarditis in humans. These results suggest that the loss of immune tolerance results in myocarditis. The tissue microenvironment influences the local immune dysregulation in autoimmunity. Recently, tenascin-C (TN-C) has been found to play a role as a local regulator of inflammation through various molecular mechanisms. TN-C is a nonstructural extracellular matrix glycoprotein expressed in the heart during early embryonic development, as well as during tissue injury or active tissue remodeling, in a spatiotemporally restricted manner. In a mouse model of autoimmune myocarditis, TN-C was detectable before inflammatory cell infiltration and myocytolysis became histologically evident; it was strongly expressed during active inflammation and disappeared with healing. TN-C activates dendritic cells to generate pathogenic autoreactive T cells and forms an important link between innate and acquired immunity.

Fulminant myocarditis: a comprehensive review from etiology to treatments and outcomes

Fulminant myocarditis (FM) is characterized by a rapid progressive decline in cardiac function and a high mortality rate. Since the first report of FM patients in the 1980s, several clinical trials and research studies have been published increasing our knowledge regarding FM. Currently, the diagnosis of FM depends on various techniques including electrocardiography, echocardiography, endomyocardial biopsy, and cardiac magnetic resonance. The development of mechanical circulation support (MCS) devices and progress in our understanding of the pathophysiological mechanisms underlying FM, treatment regimens have evolved from simple symptomatic treatment to a life support-based comprehensive treatment approach. The core mechanism underlying the development of FM is the occurrence of an inflammatory cytokine storm. This review provides a comprehensive account of the current understanding of FM pathophysiology and knowledge regarding its etiology, pathophysiology, treatments, and outcomes.

Pre-Existing Cardiovascular Conditions as Clinical Predictors of Myocarditis Reporting with Immune Checkpoint Inhibitors: A VigiBase Study

Simple Summary

Up to 50% of myocarditis events developed in cancer patients upon treatment with immune checkpoint inhibitors (ICIs) are fatal. Therefore, identification of clinical risk factors predicting myocarditis onset during treatment with ICIs is important for the purpose of cardiac surveillance of high-risk patients. The aim of this retrospective matched case-control study was to assess whether pre-existing cardiovascular conditions were associated with the reporting of myocarditis with ICIs in VigiBase, the World Health Organization global database of suspected adverse drug reactions. Taking drugs labelled for the treatment of cardiovascular conditions as a proxy for concomitant cardiovascular risk factors and/or cardiovascular diseases, we found an association of moderate size between pre-existing cardiovascular conditions and the reporting of myocarditis with ICIs. Future prospective pharmacoepidemiological studies should assess the causal relationship between pre-existing cardiovascular conditions and myocarditis onset in a cohort of cancer patients followed during treatment with ICIs.

Abstract

Although rare, immune checkpoint inhibitor (ICI)-related myocarditis can be life-threatening, even fatal. In view of increased ICI prescription, identification of clinical risk factors for ICI-related myocarditis is of primary importance. This study aimed to assess whether pre-existing cardiovascular (CV) patient conditions are associated with the reporting of ICI-related myocarditis in VigiBase, the WHO global database of suspected adverse drug reactions (ADRs). In a (retrospective) matched case-control study, 108 cases of ICI-related myocarditis and 108 controls of ICI-related ADRs other than myocarditis were selected from VigiBase. Drugs labeled as treatment for CV conditions (used as a proxy for concomitant CV risk factors and/or CV diseases) were found to be associated more strongly with the reporting of ICI-related myocarditis than with other ICI-related ADRs (McNemar’s chi-square test of marginal homogeneity: p = 0.026, Cramer’s coefficient of effect size: Φ = 0.214). No significant association was found between pre-existing diabetes and ICI-related myocarditis reporting (McNemar’s test of marginal homogeneity: p = 0.752). These findings offer an invitation for future prospective pharmacoepidemiological studies to assess the causal relationship between pre-existing CV conditions and myocarditis onset in a cohort of cancer patients followed during ICI treatment.

Management perspectives from the 2019 Wuhan international workshop on fulminant myocarditis

Fulminant myocarditis (FM) is a form of acute myocardial inflammation leading to rapid-onset hemodynamic instability due to cardiogenic shock or life-threatening arrhythmias. As highlighted by recent registries, FM is associated with high rates of death and heart transplantation, regardless of the underlying histology. Because of a paucity of evidence-based management strategies exists for this disease, an International workshop on FM was held in Wuhan, China, in October 2019, in order to share knowledge on the disease and identify areas of consensus. The present report highlights both agreements and controversies in FM management across the world, focusing the attention on areas of opportunity, FM definition, the use of endomyocardial biopsy and viral identification on heart specimens, treatment algorithms including immunosuppression and the timing of circulatory support escalation. This report incorporates the most recent recommendations from national and international professional societies. Main areas of interest and aims of future prospective observational registries and randomized controlled trials were finally identified and suggested.