Table of Contents
- Definition of Myocarditis
- Epidemiology of Myocarditis
- Etiology of Myocarditis
- Classification of Myocarditis
- Pathophysiology of Myocarditis
- Pathology of Myocarditis
- Symptoms and Clinical Presentation of Myocarditis
- Diagnostics of Myocarditis
- Differential Diagnosis of Myocarditis
- Treatment of Myocarditis
- Complications of Myocarditis
- Prognosis of Myocarditis
- Review Questions
Definition of Myocarditis
Myocarditis is the inflammation of the myocardium, which contains the contractile muscle layer of the heart. Progression of this inflammatory disease may lead to heart failure.
Epidemiology of Myocarditis
The annual incidence of myocarditis is estimated to be about 17 cases per 100,000 individuals. Fatality occurs in less than 2% of all cases. In approximately 4% of cases of infection with coxsackie B virus, the heart will be affected as well. For other cardiotropic viruses, this number decreases by about 1%. When young adults die from sudden cardiac arrest, the autopsy will reveal myocarditis in approximately 10% of those patients.
Etiology of Myocarditis
Myocarditis may be caused by one or more of the following :
- Infectious organisms.
- Autoimmune disorders.
- Exogenous agents.
- Genetic predisposition.
- Environmental causes.
A distinction is made between infectious and noninfectious forms. The coxsackie B virus is often the trigger of the infectious form of myocarditis. Other entero-, adeno-, and influenza viruses, (e.g., Epstein-Barr virus, cytomegalovirus, hepatitis C virus, or human immunodeficiency virus [HIV]) can also lead to myocarditis. Bacteria are able to induce myocarditis as well. This includes primarily staphylococci, streptococci, enterococci, and the spirochete Borrelia burgdorferi. Fungi, protozoa, and parasites may also be the cause.
In rare cases, chronic systemic diseases such as rheumatoid arthritis, vasculitis, and collagenases can trigger noninfectious myocarditis. Medications may cause hypersensitivity myocarditis. An idiopathic Fiedler myocarditis or myocarditis following radiation therapy to the mediastinum is also possible.
|Viral infections (most common)||Bacterial infections (occasional)|
Classification of Myocarditis
Myocarditis can be classified according to its course or its pathogenesis. The disease may be acute or chronic myocarditis in nature. The pathogenesis can be differentiated based on whether it is infectious myocarditis, toxic myocarditis, idiopathic myocarditis, or autoimmune myocarditis.
Pathophysiology of Myocarditis
The virus damages myocardial cells, which triggers an immune reaction. This can cause the destruction of other myocardial cells or cause cross-reactions between viral and myocardial structures, which produce antibodies. This eventually leads to the inability of the heart to pump properly, resulting in heart failure (viral myocarditis).
Pathology of Myocarditis
Histologically, Myocarditis can be divided into the following categories:
- Contraction band necrosis, reperfusion
Initially, viral infections typically present with a serous exudate and hypereosinophilia. Later, the fibrotic replacement of cardiac muscle cells can occur. In bacterial infections, microabscesses that are rich in granulocytes and bacteria are present.
Symptoms and Clinical Presentation of Myocarditis
The onset and progression of myocarditis are slow and nonspecific, with symptoms such as fever, fatigue, or chest pain. During the course of the disease (days to weeks), signs of heart failure and arrhythmia, as well as tachycardia, can develop. Rarely, the course may be fulminant and similar to an infarction.
|Unexplained heart failure||Arrhythmia|
|May mimic acute MI||Cardiac abnormalities developing during recognized systemic infection|
|E.g. fever, malaise, arthralgias, respiratory symptoms|
Diagnostics of Myocarditis
Laboratory diagnostics of myocarditis
The patient’s medical history often reveals evidence of a previous infection. Clinical signs can be combined with laboratory values such as an elevated erythrocyte sedimentation rate (ESR) and increased C-reactive protein (CRP), troponin, and CK-MB levels, as well as with bacteriological and viral diagnostics. ECG may show nonspecific changes. Diagnosis is confirmed after detection of the pathogen in a myocardial biopsy.
Differential Diagnosis of Myocarditis
Similar diseases to myocarditis
A distinction must be made between postmyocardial cardiomyopathy, viral myocarditis as well as virus-positive myocarditis, and inflammatory dilated cardiomyopathy (DCM).
Treatment of Myocarditis
Therapeutic approaches for myocarditis
Initially, the treatment of myocarditis involves relieving the symptoms. Physical rest, abstinence from alcohol, thromboembolism prophylaxis, and the treatment of complications such as heart failure are indicated. Moreover, the therapeutic approach may be causal by treating the causative disease such as diphtheria or Chagas disease. As part of research studies, antiviral and immunosuppressive treatments are also used.
|Supportive therapy – hemodynamically stable patients||Chagas disease|
|Anti-viral therapy: limited applications||Immunosuppression|
|Not for routine use|
Complications of Myocarditis
Complications of myocarditis include:
- Idiopathic dilated cardiomyopathy
- Cardiac Insufficiency
- Cardiac arrhythmias
Prognosis of Myocarditis
Partial or full clinical recovery can be expected, but relapse is also a possibility. Unresolved cases may lead to dilated cardiomyopathy. Indicators of advanced cardiomyopathy may warrant heart transplantation.
The answers can be found below the references.
1. Which is the most common trigger of infectious myocarditis?
- Cardiotropic viruses
2. How can the diagnosis of myocarditis be confirmed?
- Measurement of troponin
- Increased ESR
- Myocardial biopsy
- Determining the CK-MB level
- Changes in the EKG
3. Which of the following is least likely to be part of the clinical manifestation of myocarditis?
- Serous exudate
- Fibrotic replacements
- Hypertrophic myocytes
- Microabscesses rich in bacteria