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 as myocarditis does. 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 a 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 the majority of patients are diagnosed with idiopathic myocarditis.
What are symptoms of myocarditis?
Myocarditis can be mild and cause virtually no noticeable symptoms. The most frequent symptom of myocarditis is pain in the chest. Other symptoms are related to the underlying triggering cause, like infection or an autoimmune disorder. The following is a list of symptoms and signs of myocarditis:
Chest pain or chest discomfort
Shortness of breath
Swelling and/or edema
Abnormal heartbeat (palpitations)
Sudden death (in young adults)
Fever (usually associated with an infectious process)
Myocarditis in children and infants has more nonspecific symptoms:
Increasing difficulty breathing
How is myocarditis diagnosed?
Myocarditis is preliminarily diagnosed by detecting signs of irritation of heart muscle during the patient’s history and physical exam. Blood tests for heart muscle enzymes (CPK levels) can be elevated. Electrical testing (EKG) can suggest irritation of heart muscle and document irregular beating of the heart. Nuclear heart scan testing can show irregular areas of heart muscle.
Other tests to help definitively diagnose myocarditis include chest X-rays to determine the size and shape of the heart, MRI, and echocardiogram. Sometimes cardiac catheterization with heart muscle biopsy (endomyocardial biopsy) may be done to definitively determine the likely underlying cause for the disease.