ANSWER 24
This patient has viral myocarditis due to Coxsackie B virus. Viruses which can cause
myocarditis include Coxsackie B and A, echovirus, adenovirus, influenza, varicella, polio,
mumps, rabies, viral hepatitis, rubella, Epstein–Barr virus (EBV), cytomegalovirus (CMV), and
herpes simplex virus. Myocarditis may occur during a bacteraemia or fungaemia. Rickettsia
and diptheria can cause myocarditis. In rural South America acute infection with the proto-
zoanTrypanosoma cruzicauses fever, myocarditis and hepatosplenomegaly, and 10–30 years
later this can lead to cardiac failure and conduction system defects (Chagas’ disease). Cocaine
abuse can cause myocarditis, and sudden death. Profound hypocalcaemia, hypophos-
phataemia, and hypomagnaesaemia can all cause myocardial depression.
The clinical picture of myocarditis is non-specific, but common symptoms include myal-
gia, fatigue, shortness of breath, pericardial pain and palpitations. The prodromal flu-like
illness is suggestive of this condition. The main clinical signs are those of cardiac failure.
Patients usually have a marked sinus tachycardia disproportionate to the slight fever. ECG
usually shows ST segment and T-wave abnormalities. There may be atrial or, more com-
monly, ventricular arrhythmias or signs of conducting system defects. Chest X-ray may be
normal if the myocarditis is mild, but if there is cardiac failure there will be cardiomegaly
and pulmonary congestion. The differential diagnoses in this case include hypertrophic
cardiomyopathy, pericarditis and myocardial ischaemia.
Echocardiography should be performed to confirm the diagnosis. Echocardiographic changes
may be focal affecting only the right or left ventricle, or global. There is poor contractility of
the myocardium. Cardiac enzymes such as creatine kinase are raised. An endomyocardial
biopsy is performed as soon as possible, and will show evidence of myocardial necrosis. Paired
serum samples should be taken for antibody titres to Coxsackie B and mumps. Coxsackie virus
can be cultured from the throat, stool, blood, myocardium or pericardial fluid.
Bed rest is the treatment for the period of acute viral myocarditis. Diuretics and angiotensin-
converting enzyme (ACE) inhibitors are used to treat cardiac failure. There is controversy
over treatment with corticosteroids. Corticosteroids tend to be used in patients with a short
history, a positive endomyocardial biopsy, and the most severe disease. Most cases are
benign and self-limiting, and cardiac function will return to normal. However a minority
will develop permanent cardiac damage leading to a dilated cardiomyopathy. Definitive
treatment may then involve cardiac transplantation.
- The features in favour of the diagnosis of viral myocarditis include the young age of the
patient, the preceding acute febrile illness and subsequently the raised serum antibody
titres to Coxsackie B. - It is important to take a history of foreign travel and substance abuse
- Outcome in adults is generally good, but a proportion of patients will develop a dilated
cardiomyopathy.