Myocarditis

Myocarditis

Cover image: Viral heart disease, also known as myocarditis, is a heart condition is known to affect young people | Shutterstock

Introduction

https://www.youtube.com/watch?v=8tLtoHTjkpg

Myocarditis, also known as inflammatory cardiomyopathy, is inflammation of the heart muscle.


Aetiology

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Viral infection is the most common aetiology, but several other aetiologies of myocarditis have also been implicated. | Pollack, A., Kontorovich, A. R., Fuster, V. and Dec, G. W. (2015) ‘Viral myocarditis[mdash]diagnosis, treatment options, and current controversies’, Nat Rev Cardiol. Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved., 12(11), pp. 670–680. Available at: http://dx.doi.org/10.1038/nrcardio.2015.108.

Pathophysiology

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Phase 1 (Acute Phase) commences with viral entry into the host and transit to the myocardium. In predisposed individuals, coxsackievirus binds to DAF on the cell surface, which shuttles the virus towards the CAR, localized at cell–cell junctions. The complex is internalized by the cell, triggering numerous cellular responses and activation of host innate immunity. Virus replication within the cardiomyocyte causes cell lysis, which prompts a set of cascades leading to the release of cytokines. In phase 2 (Subacute Phase), both cellular and humoral responses contribute to autoimmune-mediated injury. The first immune cells recruited to the injured myocardium are NK cells, followed by macrophages. Infiltration of T cells typically peaks at 7–14 days; this timing coincides with the most severe phase of disease. As viral titres decrease, inflammation subsides (phase 3, Chronic Phase) and some individuals experience complete resolution of myocardial injury. However, in other patients, viral genomic material persists (in some cases up to 12 months; viral persistence throughout the entirety of end-stage disease until time of transplantation has been demonstrated), contributing to chronic inflammation and dilated cardiomyopathy. Abbreviations: CAR, coxsackievirus and adenovirus receptor; DAF, decay accelerating factor; LV, left ventricular; NK, natural killer; TNF, tumour necrosis factor. | FF, M., JD, H., Moridzadeh, R., Nicholson, J., Trimarchi, S. and KA, E. (2016) ‘Acute aortic dissection and intramural hematoma: A systematic review’, JAMA, 316(7), pp. 754–763. Available at: http://dx.doi.org/10.1001/jama.2016.10026.

Clinical Features

  • ASYMPTOMATIC
  • SYMPTOMATIC
    • Positional chest pain (M/C)
    • Tachyarrhythmias
      • Inflammation of pacemaker cells
    • General symptoms:
      • Fever, fatigue, dyspnoea

 

myocarditis
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Complications

  • Heart failure due to dilated cardiomyopathy
  • Cardiac arrest
  • Sudden death

Diagnosis

Investigations

  • BLOOD
    • Markers of myocardial damage:
      • ↑ Troponin
      • ↑ Creatine kinase
    • ↑ C-reactive protein (CRP)
    • ↑ Erythrocyte sedimentation rate (ESR)
  • SEROLOGY
    • ↑ IgM

ECG

  • Saddle shaped ST-elevations
  • Sinus tachycardia
  • T-wave inversion

Imaging

  • X-ray chest
    • Enlarged heart
  • Echocardiography
    • Inflammed heart muscle walls

Histopathology (Biopsy)

  • DEFINITIVE
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a | Substantial inflammatory infiltration (blue staining) is seen on haematoxylin and eosin staining of a left ventricular apical specimen from a woman aged 56 years with fulminant myocarditis (magnification ×100). b | The same specimen shows profound lymphocyte and macrophage intrusion (black arrows), myocyte destruction (asterix), derangement of myocardial architecture (yellow arrows), and intracellular oedema (haematoxylin and eosin staining, magnification ×400). c | Four-chamber and d | short-axis images acquired using cardiac MRI in a separate patient with acute myocarditis revealing abnormal patchy epicardial delayed gadolinium enhancement in the inferolateral segments. Abbreviations: LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. | FF, M., JD, H., Moridzadeh, R., Nicholson, J., Trimarchi, S. and KA, E. (2016) ‘Acute aortic dissection and intramural hematoma: A systematic review’, JAMA, 316(7), pp. 754–763. Available at: http://dx.doi.org/10.1001/jama.2016.10026.

Management

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Comprehensive clinical practice guidelines specific to the treatment of myocarditis do not exist. We have proposed this algorithm for the diagnosis and treatment of patients with myocarditis. If any uncertainty exists with regard to the diagnosis, cardiac MRI is extremely valuable, owing to its high specificity and capacity to distinguish myocarditis from other myocardial disease processes. Abbreviations: ECG, electrocardiogram; EMB, endomyocardial biopsy; LV, left ventricular. | Pollack, A., Kontorovich, A. R., Fuster, V. and Dec, G. W. (2015) ‘Viral myocarditis[mdash]diagnosis, treatment options, and current controversies’, Nat Rev Cardiol. Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved., 12(11), pp. 670–680. Available at: http://dx.doi.org/10.1038/nrcardio.2015.108.

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