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    Myocarditis – Diagnosis and Treatment

    Cardiovascular, Inflammatory

    Last Updated Jan 19, 2022
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    By Floyd Besserer, Shayne Hopwood


    • Myocarditis is a challenging and potentially life-threatening condition that is underdiagnosed in the emergency department.
    • Complications include cardiomyopathy, heart failure, arrhythmias, and fulminant myocarditis.
    • It is more common in males and younger populations.
    • Myocarditis is an inflammatory disease of the cardiac musculature as seen on biopsy.
    • Causes include:
      • Infectious
        • Most commonly viral.
        • Consider bacterial, fungal, protozoal, and parasitic.
      • Immune-mediated and systemic disorders
        • Allergens including drug hypersensitivity, tetanus toxoid, vaccines, serum sickness.
        • Autoimmune such as IBD, giant cell, SLE, scleroderma, thyrotoxicosis, GPA, Kawasaki’s, rheumatic heart disease.
        • Alloantigens such as in heart transplant rejection.
      • Toxins
        • Alcohol, amphetamines, anthracyclines, heavy metals, carbon monoxide, catecholamines, radiation.

    Clinical presentation

    • Variable clinical presentation
      • Symptoms include dyspnea and chest pain (most common), as well as fatigue, palpitations, and edema.
      • Presentation may range from subclinical or mild symptoms to severe heart failure, cardiogenic shock, and sudden cardiac death.
      • Viral prodrome often present including fever, malaise, myalgia, cough, and diarrhea 2 weeks prior to cardiac dysfunction.
    • Suspect myocarditis in patients with
      • Heart failure or cardiogenic shock with ventricular dysfunction and no clear etiology.
      • Signs of MI with minimal or absent cardiovascular risk factors or normal angiogram and no clear etiology.
      • Pediatric patient with signs of cardiac dysfunction, especially with viral prodrome.
      • Patient with suspected sepsis who worsens with IV fluids and has signs of volume overload.

    Diagnostic Process

    • Gold standard for diagnosis is endomyocardial biopsy (EMB)
      • Limited role in emergency room setting as it is not readily available, has a high sampling error, and has relatively low yield in terms of impact on patient management.
    • Recommended approach is based on 3 tiered classification as adapted from Sagar et al. 2012 when myocarditis is suspected.
      • Possible subclinical acute myocarditis
        • No cardiovascular symptoms but at least one of:
          • Elevated cardiac biomarkers.
          • ECG findings consistent with cardiac injury.
          • Abnormal cardiac function on echo.
          • CMRI findings.
        • Probable acute myocarditis
          • Cardiovascular symptoms AND at least one of:
            • Elevated cardiac biomarkers.
            • ECG findings consistent with cardiac injury.
            • Abnormal cardiac function on echo.
            • CMRI findings.
          • Definite myocarditis
            • Histological or immune-histological evidence of myocarditis.
    • Recommended investigations
      • Labs: CBC, lytes, renal/liver function, CRP, troponin, BNP
        • Troponin levels are commonly elevated in myocarditis, but their absence is not sensitive in myocarditis and should not be used for prognosis.
        • Over 50% of patients will have elevated BNP, but the absence of BNP does not rule out myocarditis.
        • CRP positive in majority of patients, but is not specific for myocarditis.
        • CBC showing eosinophilia may suggest eosinophilic myocarditis.
      • ECG
        • Useful to evaluate for ST/T wave changes, AV blocks.
      • CXR
        • Abnormal in 50% of patients including cardiomegaly, pulmonary edema, and pleural effusions.
        • Not sensitive.
      • Echocardiogram
        • Assessing for global or regional ventricular dysfunction, wall motion abnormalities, and pericardial effusions.
        • If formal TTE unavailable, POCUS is useful to assess for gross signs of cardiac dysfunction or for pulmonary edema.
      • Consider cardiovascular MRI (CMRI)
        • Patients must be clinically stable.
        • Findings must be consistent with myocarditis according to Lake-Louise criteria (specialist interpretation recommended.)
        • Useful in low risk myocarditis to differentiate between myocarditis and ACS or in intermediate risk myocarditis for diagnosis.
        • Limited role in high risk myocarditis.

    Recommended Treatment

    • Treatment should be tailored around the etiology of the myocarditis, risk stratification, and clinical presentation.
    • For hemodynamically unstable patients
      • May require inotropic support, diuresis, and ventilator support.
      • Norepinephrine is the preferred vasopressor in myocarditis.
      • Avoid excessive IV fluids which may worsen symptoms.
    • For hemodynamically stable patients
      • If heart failure is present, standard heart failure therapy may be used including ACEi/ARB and beta blocker with consideration of MRA.
    • Immunosuppressive agents should only be considered for subgroups of patients with specific etiologies of myocarditis including giant cell myocarditis, sarcoidosis, or other systemic autoimmune diseases, which require EMB.
    • Immunotherapy is not recommended as it has not been shown to affect outcomes and may have significant side effects.
    • Antiviral therapy should not routinely be used.
    • NSAIDs not recommended as it may worsen mortality in myocarditis, as seen in experimental models, although clinical trial data is lacking.
    • Physical exercise should be restricted in the acute phase, which will require follow-up 6 months after onset of the disease (expert opinion.)
    • Disposition
      • All patients with suspected acute myocarditis should be admitted to hospital and those requiring vasopressors or ventilator support require ICU admission.
      • 50% recover fully.
      • 30% will decompensate.
      • 20% require transplantation.

    Quality Of Evidence?


    Overall evidence for diagnosis of myocarditis is mixed as there have been multiple proposed definitions with no clear universally agreed upon criteria. We have chosen a clinical approach as suggested by Sagar et al. as this is more relevant in an emergency department setting.


    Overall evidence for the treatment of myocarditis is poor given the lack of large multi-centre randomized controlled trials. The recommendations are based on the consensus of the Canadian and European guidelines utilizing existing data available and expert opinion.


    Related Information

    Reference List

    1. Caforio ALP, Pankuweit S, Arbustini E, Basso C, Gimeno-Blanes, Felix SB, Fu M, Helio T, Heymans S, Jahns R. 2013. Current state of knowledge on aetiology, diagnosis, management, and therapy of myocarditis: a position statement of the European Society of Cardiology Working Group on Myocardial and Pericardial Diseases. Euro Heart J. 34:2636-2648.

    2. Ezekowitz JA, O’Meara E, McDonald MA, Abrams H, Chan M, Ducharme A, Giannetti N, Grzeslo A, Hamilton PG, Heckman GA. 2017. 7.5.5 Myocarditis in: 2017 Comprehensive update of the Canadian society guidelines for the management of Heart failure. Can J Cardiol. 33: 1342-1433.

    3. Gottlieb M, Bridwell R, Petrak V, Long B. 2021. Diagnosis and management of myocarditis: An evidence-based review for the emergency medicine clinician. J Emerg Med. 61(3): 222-233.

    4. Sagar S, Liu PP, Cooper LT. 2012. Myocarditis. Lancet. 379(9817): 738-747.

    5. Sinagra G, Anzini M, Pereira NL, Bussani R, Finocchiaro G, Bartunek J, Merlo M. 2016. Myocarditis in clinical practice. Mayo Clin Proc. 91(9): 1256-1266.


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