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Quick GuideHeart Disease: Symptoms, Signs, and Causes
What is myocarditis?
Myocarditis is inflammation of the heart muscle (myocardium). The inflammation of the heart muscle causes degeneration or death of heart muscle cells. Myocarditis has many different causes and can result in a range of outcomes from mild (presenting briefly and resolving) to rapidly progressing fatal disease. Myocarditis is differentiated from pericarditis because pericarditis is inflammation of the sac that surrounds the heart and does not involve heart muscle like myocarditis. However, it is not unusual to have a patient present with both pericarditis and myocarditis.
There are many different types of myocarditis and a wide range of possible agents that can trigger the disease. Examples include:
- Viral: Coxsackie B virus, enterovirus, adenovirus, influenza, and many others
- Bacterial: Streptococci, meningococci, clostridia, Corynebacterium, mycobacteria, and many others
- Fungal and parasites: Candida, aspergillosis, Cryptococcus, schistosomes, filaria, malaria, toxoplasma, and many others
- Lymphocytic: Heart muscle infiltrated with lymphocytes
- Eosinophilic: Heart muscle infiltrated with eosinophils
- Autoimmune: Caused by autoimmune diseases, such as lupus
- Fulminant: Inflammatory process in the heart muscle that leads to acute severe heart failure
- Idiopathic: Inflammatory process in the heart muscle with no known cause
- Acute: Symptoms appear rapidly and usually decrease after week or two
- Chronic: Slow appearance of symptoms that last greater than two weeks
What causes myocarditis?
The causative agents that damage myocardium include the following:
- Cytotoxic effects of infecting agents like viruses, bacteria fungi, and/or parasites
- Immune response triggered by infecting agents and cytokines produced in the myocardium in response to infection or inflammation
- Chemicals released during myocardial cell death
- Autoimmune responses can also trigger myocardial inflammation
- Some medications and/or toxins such as clozapine, radiation therapy, arsenic, carbon monoxide, and many others
- Certain diseases like lupus, Wegener's granulomatosis, and others
About half of the time, the triggering agent for myocardial inflammation is not known (idiopathic). This is especially true in pediatric population where about 82% of patients are diagnosed with idiopathic myocarditis.