Endomyocardial fibrosis

Although usually mild, this inflammation of the heart muscle can be fatal. Here's how to intervene.

Dave Mannheim, 37, arrives at your emergency department (ED) complaining of shortness of breath and chest pain. He recently had symptoms of an upper respiratory infection, including fever and chills. A chest X-ray shows cardiac enlargement.

An electrocardiogram (ECG) shows nonspecific ST-segment and T-wave abnormalities and left axis deviation. Your assessment reveals jugular vein distension, bibasilar crackles, and peripheral edema. The ED physician suspects myocarditis.

A relatively rare disorder, acute myocarditis is an inflammation of the myocardium, the heart's muscular layer. If not treated, it can lead to coronary artery thrombus, coronary ischemia, dilated cardiomyopathy, cardiac arrhythmias, and sudden death. Difficult to diagnose, myocarditis should be considered if myocardial infarction (MI) has been ruled out in a patient with dyspnea and chest discomfort, especially if he has a history of recent viral illness.

Understanding myocarditis

Triggered by a virus or another underlying cause (see What Can Trigger Myocarditis?), leukocytes, lymphocytes, and macrophages infiltrate the myocardium, leading to inflammation and interstitial fibrosis in the myocardium. Because inflammation and fibrosis reduce blood flow, areas of the myocardium may become necrotic. This necrosis may be patchy or global.

Cardiac contractility decreases, leading to a reduction in cardiac output (CO). If CO falls significantly, the patient may experience overt left ventricular failure and die. In less serious cases, the patient is still at risk for complications or death from dilated cardiomyopathy.

In the United States, most clinically significant cases of acute myocarditis are caused by the coxsackievirus type B. The patient may have upper respiratory symptoms such as fever, chills, and sore throat. Other possible signs and symptoms include abdominal pain and nausea, vomiting, diarrhea, arthralgia, and myalgia. These generally occur up to 6 weeks before the patient has signs and symptoms of myocarditis, such as chest pain and overt heart failure with dyspnea. Specific signs and symptoms of myocarditis depend on the type of infection and the degree of myocardial damage.

In children, symptoms of myocarditis are nonspecific and include fever, respiratory distress, poor feeding, and cyanosis.

Finding clues

The following diagnostic tests can help you determine if a patient has myocarditis or another condition.

* A chest X-ray may show an enlarged heart with evidence of heart failure, such as prominent blood vessels or fluid within the lungs.

* An ECG may show arrhythmias, as well as ST-segment and T-wave abnormalities. Decreased QRS amplitude and transitory Q-wave development suggest myocarditis. You also may notice a heart block. The ECG usually returns to normal within 2 months.

* Echocardiography is less likely to be as definitive as it is for diagnosing pericardial effusion. Changes noted on echocardiography include diffuse hypocontractility and cardiac chamber hypertrophy. In some cases, echocardiography reveals valvular dysfunction and pericardial effusions.

* Endomyocardial biopsy through cardiac catheterization may be performed to confirm the diagnosis of myocarditis. However, because of the patchy nature of myocarditis, results are accurate only about 65% of the time. Lab studies may show an increase in creatine kinase, an increased erythrocyte sedimentation rate, and an increase in white blood cells (leukocytosis).

Treating myocarditis

Fortunately, most cases of viral myocarditis are mild and self-limiting. Treatment is supportive, aimed at promptly recognizing and treating cardiac arrhythmias, preserving myocardial function, and preventing heart failure and other complications, such as dilated cardiomyopathy. If the underlying cause of myocarditis is Lyme disease or another bacterial infection, the patient will receive antibiotics as indicated. Monitor for arrhythmia development, especially in the acute phase.

Mainstays of treatment include providing supplemental oxygen, limiting myocardial oxygen demand, and enhancing circulatory support and cardiac output if needed. Patients who develop heart failure may be treated with angiotensin-converting enzyme (ACE) inhibitors, diuretics, and sodium restriction. Anticoagulation may be indicated to reduce the risk of thrombosis and pulmonary embolism. In more severe cases of myocarditis, the patient may need inotropic support with such intravenous drugs as dobutamine.

Myocarditis appears to make patients sensitive to digoxin. If your patient is taking digoxin, monitor him for toxicity.

Intravenous immunoglobulin may be given to enhance the immune system and limit the disease. In severe cases, the patient may need heart transplantation.

During the acute phase of myocarditis, keep the patient on bed rest because activity increases myocardial oxygen demand. Teach him about his medications and when he can resume activities and exercise.

Mr. Mannheim, who had severe myocarditis with dilated cardiomyopathy has an ejection fraction below 35%. He's put on sodium restriction, furosemide, and an ACE inhibitor and will be evaluated to determine if his heart failure can be managed medically or if he'll need a heart transplant.

By knowing how to recognize myocarditis and intervene appropriately, you may be able to help your patient avoid complications and recover quickly.

SELECTED WEB SITE

Family Practice Notebook: Myocarditis http://www.fpnotebook.com/CV131 .htm

Last accessed on March 9, 2004.

SELECTED REFERENCES

Alspach, J.: Core Curriculum for Critical Care Nursing. Philadelphia, Pa., WB. Saunders Co., 1998.

Gawlinski, A., and Hamwi, D.: Acute Care Nurse Practitioner Clinical Curriculum and Certification Review. Philadelphia, Pa., W.B. Saunders Co., 1999.

Tedeschi, A., et al.: "High-Dose Intravenous Immunoglobulin in the Treatment of Acute Myocarditis. A case Report and Review of the Literature," Journal of Internal Medicine. 251(2):169-173, February 2002.

By Susan Simmons Holcomb, RN-CS, ARNP, MN, PHD

Susan Simmons Holcomb is a nurse practitioner at the Walk-In Health Care of Olathe in Olathe, Kan., and a consultant in continuing nursing education at Kansas City (Kan.) Community College.

Copyright Springhouse Corporation Apr 2004
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