Chronic Myocarditis

A: Many different environmental agents can trigger myocarditis including viral or bacterial infections, toxins, and drugs 7. The reasons why some persons recover and others do not is an area of active investigation.

A: Examination of heart tissue under a microscope is the only way to prove the diagnosis of chronic myocarditis. Up to 40% of patients with chronic dilated cardiomyopathy (large, poorly functioning hearts) who have symptoms of heart failure despite standard medical care can have myocarditis when special techniques are used to study heart tissue.

Magnetic resonance imaging (MRI) of the heart is under evaluation to aid in the diagnosis of chronic myocarditis. The sensitivity and specificity of MRI for the diagnosis of myocarditis varies with the duration of illness and the sequences used.

Blood tests that measure damage to heart muscle cells (e.g. troponin T) can also be elevated in chronic myocarditis, but the levels may be normal or only minimally elevated.

The electrocardiogram has nonspecific changes in the majority of myocarditis cases. There are also no specific echocardiographic features of chronic myocarditis.

The known viral causes of myocarditis include:

Parvovirus B19

Parvovirus B19 spreads via respiratory droplets that are expelled when infected people cough, sneeze, or speak. Approximately half the population carries its antibodies. It is the cause of fifth disease, sometimes called slapped cheek syndrome for the red facial rash caused in children ages six to 10. Teens and adults typically experience rashes elsewhere, especially the hands and feet. Symptoms of infection usually occur within a week of exposure and last for approximately one week. Parvovirus B19 has also been associated with:

• Severe birth defects
• Miscarriage
• Infection in patients with acquired immunodeficiency syndrome (AIDS), arthritis, and aplastic anemia (lack of red blood cell production)

At this time, there is no vaccination against parvovirus B19.

Human Herpes Virus 6

This virus is transmitted via saliva and often presents with a rash and fever. It is so common that most infants are exposed by 13 months of age, although infection may occur during the first weeks of life. Approximately 20% of infant emergency department visits are linked to fevers caused by human herpes virus 6. Conditions associated with this virus include:

• Sixth disease (roseola infantum)
• Hepatitis
• Encephalitis
• Multiple sclerosis
• Chronic fatigue syndrome
• Fibromyalgia
• And more…

Once contracted, the virus remains in the salivary glands and bone marrow for life.

Enteroviruses

These viruses include Coxsackie A virus, or hand, foot, and mouth disease, and Coxsackie B virus, which typically presents as a mild rash, nasal and throat infections, and symptoms commonly associated with colds. It has been known to cause not just myocarditis but also:

• Pericarditis, or the inflammation of the membrane that surrounds the heart
• Meningitis, or inflammation of the spinal cord’s outer membranes
• Pancreatitis, or inflammation of the pancreas

A: Non-infectious causes of myocarditis are uncommon, and include myocarditis associated with connective tissue diseases such as systemic lupus erythematosus or rheumatoid arthritis. Myocarditis can also develop in patients who have rare primary disorders of immune regulation.

A: Yes, most patients with chronic myocarditis also have dilated cardiomyopathy, or an enlarged heart 6. Having an enlarged heart places the patient at a greater risk for developing heart failure. Because of this, and the difficulty of treating dilated cardiomyopathy, patients may need a heart transplant. However, there are other causes of dilated cardiomyopathy and heart failure besides myocarditis.

A: There is no established treatment for chronic myocarditis. However, studies in patients with chronic heart failure that did not respond to usual care suggest a limited role for immunosuppression. Randomized trials of patients with chronic myocarditis (diagnosed by special stains of heart biopsy tissue) immunosuppression with azathioprine and prednisone resulted in an improvement in quality of life and left ventricular ejection fraction. This treatment strategy is now under evaluation in well-designed, multicenter trials. Other studies seek to evaluate antiviral therapy in patients with evidence of chronic viral heart infections.

A: No, most patients with myocarditis resolve the disease relatively quickly. Only certain susceptible individuals progress from acute to chronic myocarditis and dilated cardiomyopathy 1. Research has shown that susceptibility to develop “chronic myocarditis” depends on the type of immune response an individual has in response to infections, chemicals, or physical damage to the heart2,3,8-10.

A: Research in animal models has shown that myocarditis can be a biphasic disease, meaning that acute myocarditis can resolve and then several weeks or months later it can reappear 1. Researchers have found that proteins called cytokines that are released from inflammatory cells during acute myocarditis begin to cause changes in heart structure that only appear several weeks or months later 2-5. This process is called “remodeling” and leads to fibrosis (i.e. scar tissue in the heart) and dilated cardiomyopathy (i.e. an enlarged heart). However, it is important to note that only some individuals progress from acute to chronic myocarditis, while most patients with acute myocarditis do not develop the chronic phase of the disease.

A: In most cases, chronic myocarditis involves autoimmunity 16. An autoimmune response occurs when the immune system attacks the cells and tissues of our body. The immune system does this in an attempt to heal the damage induced by infections or chemicals, for example, but can end up causing damage itself. This results in chronic inflammation and may involve the deposition of proteins called autoantibodies on cardiac tissue that can adversely affect heart function and further promote inflammation 16-18.

A: Not necessarily. Patients are at a risk for heart failure during acute and chronic myocarditis, but for different reasons. For example, patients may be at heightened risk for heart failure during “acute myocarditis” because of the release of cytokines (which are immune signaling proteins) that adversely affect cardiac function, but at risk for heart failure during “chronic myocarditis” more because of poor cardiac function due to myocardial scarring 5.

A: Yes. Chronic myocarditis, dilated cardiomyopathy, and heart failure occurs more frequently in men than women. Recently two studies were published finding that myocardial recovery after acute myocarditis and transplant-free survival occurred much less frequently in men than women with myocarditis 6,11. Another study found that men are two times more likely to develop myocardial fibrosis (i.e. scarring) following myocarditis than women 12. Fibrosis is a scar that develops in the cardiac muscle that makes it more difficult for the heart to pump efficiently and usually leads to dilated cardiomyopathy, or an enlarged heart, and may progress to heart failure. Researchers have found that elevated testosterone levels in males directly promote the type of inflammation that leads to increased myocarditis, fibrosis, dilated cardiomyopathy, and heart failure 4,8,13-15.