assessed with immunohistochemistry to determine which types of immune cells are involved in the reaction and how they are distributed. furthermore, pcr and/or rt-pcr may be performed to identify particular viruses. finally, further diagnostic methods like microrna assays and gene-expression profile may be performed. cardiac magnetic resonance imaging (cmri or cmr) has been shown to be very useful in diagnosing myocarditis by visualizing markers for inflammation of the myocardium. cardiac mri is most sensitive when performed 2–3 weeks after the initial clinical presentation of myocarditis and may be repeated 6–12 months after onset to monitor the evolution of disease or response to treatment. the lake louise criteria (established in 2009) are a commonly used mri criteria to establish the diagnosis of myocarditis in suspected cases. the lake louise criteria include increased signal intensity after gadolinium contrast enhancement (a sign of hyperemia, or increased blood flow to damaged tissue), increased myocardial t2 relaxation time or an increased t2 signal intensity (which are signs of tissue edema or swelling), and late gadolinium contrast enhancement (which is a sign of tissue necrosis (tissue damage) or fibrosis (scarring)). in 2018, additional radiographic mri criteria were added, including increased t1 signal intensity and increased extracellular volume (both of which being signs of myocardial injury). the original 2009 lake louise criteria had a 74% sensitivity and 86% specificity in the diagnosis of myocarditis, but when adding the 2018 update to the criteria (in which t1 signal intensity was found to have high diagnostic sensitivity), the sensitivity and specificity in the diagnosis of myocarditis increased to 88% and 96% respectively. cardiac mri, if available, is recommended in all cases of suspected myocarditis. treatment while myocarditis has many etiologies and a variable constellation of signs and symptoms, many causes do not have a specific treatment thus the primary focus is on supportive care and symptom management. in some cases of biopsy-proven myocarditis, the causative cell type may indicate condition specific treatments that are beneficial. these treatments typically consist of corticosteroids, or immunosuppressants. eosinophilic myocarditis, giant cell myocarditis and cardiac sarcoidosis are usually responsive to immunosuppressive treatments; in the form of glucocorticoids with or without azathioprine and cyclosporine. some of these immune mediated forms of myocarditis require an extended course (maintenance course) of immunosuppressive therapy. it is recommended to rule out drugs and parasites as potential causes of eosinophilic myocarditis as these common causes of the variant can be effectively treated with discontinuation of the offending drug or specific anti-parasitic treatment respectively. empiric iv glucocorticoids are indicated in acute myocarditis with cardiogenic shock, heart failure, ventricular arrhythmias or high degree av block that is suspected due to auto-immune disease; but the european society of cardiology also recommends subsequent viral genome testing of endomyocardial biopsy specimens due to risk of viral activation, which may necessitate discontinuation of immunosuppression therapy. in a majority of cases, the main therapies are used to support patients and are dependent on the severity of symptoms and the time course across which myocarditis develops. supportive therapies can be divided into two broad categories, medications and mechanical support. medication the specific medications that are used to support patients are directly related to the cause of the symptom or sign. just as the symptoms of myocarditis mirror those of congestive heart failure, so too do the therapies. additionally, the order in which therapies are used depends on the degree of heart dysfunction, with stabilization of patient blood pressure and breathing taking highest priority when present. this can involve the use of inotropes, or medications that make the heart contract with greater force, as well as antiarrhythmic drugs such as adenosine or carvedilol. in patients that have stable and adequate heart function, further treatments are based on heart failure guidelines. ace inhibitors or angiotensin receptor blockers (arbs) can have a protective benefit to the heart, so either are typically used in any patient with symptomatic myocarditis. simultaneously, beta blockers are used in patients that can tolerate their heart beating at a slower rate. shortness of breath at rest and swelling can be relieved with diuretics such as furosemide, and the addition of aldosterone receptor blockers can augment the diuresis while preventing the excess loss of potassium. in patients with symptoms while resting, additional medications can be added such as digoxin. mechanical support mechanical support is used in cases of myocarditis in which medications alone do not lead to adequate heart function and the body requires additional support to achieve organ perfusion. myocarditis cases that require mechanical circulatory support are categorized as fulminant by definition. people that require additional support with their heart function can benefit from the use of ventricular assist devices like intra-aortic balloon pumps. in people with myocarditis severe enough to cause cardiac arrest, extracorporeal membrane oxygenation (ecmo) is used to adequately pump blood and provide oxygen if needed. both ventricular assist devices and ecmo can be used as bridge therapy until heart transplantation in patients that are candidates. heart transplantation is reserved for those that do not respond to the aforementioned conventional medical therapies. an implantable cardioverter-defibrillator (icd) is sometimes required in those with cardiomyopathy or heart failure caused by myocarditis due to the risk of fatal ventricular arrhythmias. the need for icd is usually assessed 3–6 months after the onset of myocarditis, after the acute phase of myocarditis has passed, with a temporary, wearable cardioverter-defibrillator acting as a temporary treatment in the interim. prognosis the prognosis associated with myocarditis is stratified by the severity and time course along which symptoms develop. in addition to symptom severity, there are also several indicators of heart function that can be used to predict patient outcomes, many of which are part of the standard evaluation of patients presenting with cardiovascular dysfunction. most people with myocarditis have an uncomplicated, self-limited and mild course while making a full recovery. however, those with myocarditis that present with a decreased ejection fraction, or those who present with heart failure, advanced atrioventricular block, with sustained ventricular arrhythmias or with hemodynamic instability have a worse prognosis with an increased risk of death or need for heart transplantation. an electrocardiogram is one of the most common screening tools used in cases of suspected cardiac pathology, such as myocarditis. the findings that correlate with poorer outcomes are non-specific and include widened qrs complexes and qt intervals, partial or complete atrial-ventricular heart block, and malignant ventricular arrhythmias like sustained ventricular tachycardia or ventricular fibrillation. electrocardiogram findings of st elevations with upward concavity and an early repolarization pattern, however, were associated with a better cardiovascular prognosis in general. in cases of acute myocarditis, cardiac magnetic resonance imaging can reveal several prognostic indicators that, similar to ecgs, are non-specific and reflect poorer cardiac physiology. late gadolinium enhancement on cardiac mri demonstrates perturbations in extracellular volume as a result of cell necrosis or edema, and is significantly associated with increases in all-cause mortality, cardiovascular mortality, and major adverse cardiovascular events. the association was strongest with any late gadolinium enhancement, but remained true for findings of anterolateral-specific enhancement. a similar relationship was found between a left ventricular ejection fraction < 50%, increased mortality, and increased major adverse cardiovascular events. myocarditis has been reported to be a major cause of sudden cardiac death (scd) in infants, adolescents, and young adults, but the reported rates show wide variation (1 to 14 percent) among young people depending on differences in scd definition and classification/ definition of myocarditis post-mortem as well as heterogeneity of study populations. and one has also to distinguish between studies about myocarditis in general and fulminant myocarditis. epidemiology the prevalence of myocarditis is estimated to be about 1-10 cases per 100,000 persons per year, with higher estimates at 22 cases per 100,000 persons annually. the highest incidence of myocarditis is seen in men between the ages of 20 and 40. fulminant myocarditis, the most severe subtype, has been shown to occur in up to 2.5% of known myocarditis presentations. when looking at different causes of myocarditis, viral infection is the most prevalent, especially in children; however, the prevalence rate of myocarditis is often underestimated as the condition is easily overlooked and is sometimes asymptomatic. viral myocarditis being an outcome of viral infection depends heavily on genetic host factors and the pathogenicity unique to the virus. if one tests positive for an acute viral infection, clinical developments have discovered that 1-5% of said population may show some form of myocarditis. in regard to the population affected, myocarditis is more common in pregnant women, children, and those who are immunocompromised. myocarditis, however, has shown to be more common in the male population than in the female. multiple studies report a 1:1.3-1.7 female-male ratio of prevalence of myocarditis. in young adults, up to 20% of all cases of sudden death are due to myocarditis. young males specifically have a higher incidence rate than any other population due to their testosterone levels creating a greater inflammatory response that increases the chance of cardiac pathologies. while males tend to have a higher risk of developing myocarditis, females tend to display more severe signs and symptoms, such as ventricular tachycardia and ventricular fibrillation, but do so at an older age. among patients with hiv, myocarditis is the most common cardiac pathological finding at autopsy, with a prevalence of 50% or more. myocarditis is the third most common cause of death among young adults with a cumulative incidence rate globally of 1.5 cases per 100,000 persons annually. myocarditis accounts for approximately 20% of sudden cardiac death in a variety of populations, including adults under the age of 40, young athletes, united states air force recruits, and elite swedish orienteers. with individuals who develop myocarditis, the first year is difficult as a collection of cases have shown there is a 20% mortality rate. myocarditis and covid-19 myocarditis can be seen during covid-19, the disease caused by the sars-cov-2 virus; with the myocarditis being associated with a spectrum of severities from asymptomatic to fulminant. in one cohort study, comparing the autopsy reports of 277 hearts of people who died from covid-19, clinically significant myocarditis was seen in approximately 2% of hearts. other estimates of the incidence of myocarditis in those with covid-19 range from 2.4 cases of definite/probable myocarditis (based on clinical criteria) per 1,000 people with covid-19 to 4.1 cases per 1,000 persons in those who are hospitalized with covid-19. although myocarditis is relatively rare in those with covid-19, when it is present it is likely to follow a severe and fulminant course for those previously hospitalized with covid-19. of those with covid-19 and myocarditis, 39% presented with severe myocarditis associated with hemodynamic instability, needing mechanical circulation support or other major interventions. severe myocarditis in covid-19 is also more likely in those who have covid-19 pneumonia. myocarditis is a rare adverse side effect from mrna covid-19 vaccines. history cases of myocarditis have been documented as early as the 1600s, but the term "myocarditis", implying an inflammatory process of the myocardium, was introduced by german physician joseph friedrich sobernheim in 1837. however, the term has been confused with other cardiovascular conditions, such as hypertension and ischemic heart disease. following admonition regarding the indiscriminate use of myocarditis as a diagnosis from authorities such as british cardiologist sir thomas lewis and american cardiologist and co-founder of the american heart association paul white, myocarditis was under-diagnosed. although myocarditis is clinically and pathologically clearly defined as "inflammation of the myocardium", its definition, classification, diagnosis, and treatment are subject to continued controversy, but endomyocardial biopsy has helped define the natural history of myocarditis and clarify clinicopathological correlations.