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 diseases. 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 the myocardium includes 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 the 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
- Liver congestion
- Abnormal heartbeat (palpitations)
- Sudden death (in young adults)
- Fever (usually associated with an infectious process)
Myocarditis in children and infants has more nonspecific symptoms:
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 the 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 determine the likely underlying cause for the disease definitively.
What is the treatment for myocarditis?
Often, myocarditis improves on its own without treatment with complete recovery. Sometimes, treatment of the underlying cause (such as bacterial infections) can lead to full recovery (for example, after antibiotics). Consequently, the diagnosis of the precise underlying cause of myocarditis can help optimal treatment.
However, in patients with more prolonged or more severe cases of myocarditis, individuals may need more specific medications or even hospitalization. Medications to reduce the heart's workload and/or reduce edema are commonly used to treat symptoms of myocarditis. They may include the following:
- Captopril (Capoten)
- Lisinopril (Zestril, Prinivil)
- Ramipril (Altace)
- Metoprolol (Lopressor)
- Carvedilol (Coreg)
- Furosemide (Lasix)
Individuals with severe symptoms of myocarditis (heart failure, acute shortness of breath) may require other treatments such as IV medications and/or vascular assist devices (pumps that help a weak heart pump) or extracorporeal membrane oxygenation (ECMO) to help provide oxygen to the blood. Occasionally, patients may require a heart transplant. Individuals who develop very irregular heartbeats (arrhythmias) may need an implanted pacemaker.
What is the prognosis (outlook) for patients with myocarditis?
The prognosis for patients with acute myocarditis who rapidly recover is very good. Even patients that develop severe myocarditis can completely recover with mild or no complications. However, if damage to the heart muscle becomes chronic and/or progressive, the prognosis for the patient declines. Those who develop severely weakened heart muscle cardiomyopathy have a poorer prognosis.
Tang, W. H. W., et al. "Myocarditis." Medscape. 5 Sept. 2014.
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