Myocarditis in Emergency Medicine Clinical Presentation

Many patients with myocarditis present with a nonspecific illness characterized by fatigue, mild dyspnea, and myalgias. A few patients present acutely with fulminant congestive heart failure (CHF) secondary to widespread myocardial involvement. Small, focal inflammation in electrically sensitive areas may be the etiology of patients whose initial presentation is sudden death. Some presentations of myocarditis, especially those related to parvovirus B19, present like an acute lateral wall myocardial infarction.

Most cases of myocarditis are subclinical; therefore, the patient rarely seeks medical attention during acute illness. These subclinical cases may have transient ECG abnormalities.

An antecedent viral syndrome is present in more than one half of patients with myocarditis. The appearance of cardiac-specific symptoms occurs primarily in the subacute virus-clearing phase; therefore, patients commonly present 2 weeks after the acute viremia.

Fever is present in 20% of patients.

Other symptoms include fatigue, myalgias and arthralgias, and malaise.

Chest discomfort is reported in 35% of patients. The pain is most commonly described as a pleuritic, sharp, stabbing precordial pain. Pericarditis may be present in many cases and may cause some of the clinical presentation of pain. It may be substernal and squeezing and, therefore, difficult to distinguish from that typical of ischemic pain.

Dyspnea on exertion is common.

Orthopnea and shortness of breath at rest may be noted if CHF is present.

Palpitations are common. Syncope in a patient with a presentation consistent with myocarditis may signal high-grade atrioventricular (AV) block and risk for sudden death.

Pediatric patients, particularly infants, present with nonspecific symptoms, including the following:

• Fever
• Respiratory distress
• Poor feeding or, in cases with CHF, sweating while feeding
• Cyanosis in severe cases

In a 6-year study of pediatric ED patients, the most common presenting symptom was dyspnea and more than half of patients were initially diagnosed with asthma or pneumonia. Six percent of patients had primarily GI symptoms.^[10]

Physical findings of myocarditis can range from a normal examination, through all classes of congestive heart failure (CHF) to cardiovascular collapse and shock.

Patients with mild cases of myocarditis have a nontoxic appearance and simply may appear to have a viral syndrome.

Tachypnea and tachycardia are common. Tachycardia is often out of proportion to fever.

More acutely ill patients have signs of circulatory impairment due to left ventricular failure.

A widely inflamed heart shows the classic signs of ventricular dysfunction including the following:

• Jugular venous distention
• Bibasilar crackles
• Ascites
• Peripheral edema

S₃ or a summation gallop may be noted with significant biventricular involvement.

Intensity of S₁ may be diminished.

Cyanosis may occur.

Murmurs of mitral or tricuspid regurgitation may be present due to ventricular dilation.

In cases where a dilated cardiomyopathy has developed, signs of peripheral or pulmonary thromboembolism may be found.

Diffuse inflammation may develop leading to pericardial effusion, without tamponade, and pericardial and pleural friction rub as the inflammatory process involves surrounding structures.

The causes of myocarditis are numerous and can be roughly divided into infectious, toxic, and immunologic etiologies, with viral etiologies most common in North America.

Amongst the infectious causes, viral acute myocarditis is by far the most common.

In a study of 172 patients with a biopsy sample showing myocarditis in which a viral genome was identified by polymerase chain reaction, the most common viruses were adenovirus, 8.1%; parvovirus B19, 36.6%; human herpesvirus 6 (HHV-6), 10.5%; enterovirus, 32.6%; co-infection with HHV-6 and parvovirus B19, 12.6%.^[11]

Other viruses implicated in myocarditis include influenza virus, echovirus, herpes simplex virus, varicella-zoster virus, hepatitis, Epstein-Barr virus, and cytomegalovirus.

Human immunodeficiency virus (HIV) deserves special mention because it seems to function differently than other viruses. HIV-1 glycoprotein 120 can directly disrupt cardiac contractility without an inflammatory response. This may explain why HIV genomes can be amplified from patients without histologic signs of inflammation. Myocarditis is the most commonly found cardiac abnormality found on biopsy tissue, present in some degree, in more than 50% of HIV patients.^[4] In addition, in patients who are infected with HIV, T-cell – mediated immune suppression increases the risk of contracting myocarditis due to other infectious causes.^[3]

Nonviral infectious causes are numerous and varied. Worldwide, the most common bacterial cause is diphtheria, and, in South America, the protozoal Chagas disease is a common entity. Streptococcal and staphylococcal species and Bartonella, Brucella, Leptospira, and Salmonella species can spread to the myocardium as a consequence of severe cases of endocarditis. Borrelia burgdorferi, the spirochete agent in Lyme disease, is also a known cause of myocarditis. Parasitic myocarditis from trypanosomiasis; trichinosis; and, in the immunocompromised host, toxoplasmosis have been identified.

Toxic myocarditis has a number of etiologies including both medical agents and environmental agents.^{[12, 1, 4]}

Among the most common drugs that cause hypersensitivity reactions are clozapine, penicillin, ampicillin, hydrochlorothiazide, methyldopa, and sulfonamide drugs. This syndrome is associated with peripheral eosinophilia, fever, and rash in patients who have biopsy findings of an eosinophilic infiltrate of the myocardium.

Numerous medications (eg, lithium, doxorubicin, cocaine, numerous catecholamines, acetaminophen) may exert a direct cytotoxic effect on the heart. Zidovudine (AZT) has been associated with myocarditis.

Environmental toxins include lead, arsenic, and carbon monoxide. Cases have been attributed to Chinese sumac.

Wasp and scorpion stings and spider bites, specifically black widows, may cause myocarditis.

Radiation therapy may cause a myocarditis with the development of a dilated cardiomyopathy.

Immunologic etiologies of myocarditis encompass a number of clinical syndromes and include the following:

• Connective tissue disorders such as systemic lupus erythematosus (SLE), rheumatoid arthritis, scleroderma, and dermatomyositis can often result in a dismal prognosis.
• Idiopathic inflammatory and infiltrative disorders such as Kawasaki disease, sarcoidosis, and giant cell arteritis may be a cause.

Rejection of the post transplant heart may present as inflammatory myocarditis.