Myocarditis and cardiomyopathy are a group of disorders that primarily affect the myocardium in the absence of hypertensive, congenital, ischemic or valvular heart disease. The distinction between them is somewhat arbitrary and not always made. Although, some people list myocarditis as a subset of cardiomyopathy, few differences help to distinguish the two conditions and this article points out those differences with regard to their onset, etiology, pathology, clinical features, management and prognosis.
It is the acute inflammation of the myocardium. In most of the occasions, cause is idiopathic, but viral infections found to be playing a major role. Most common viral infections are coxsackie virus B, mumps, influenza. Other causes include autoimmune conditions such as rheumatic fever, rheumatoid arthritis, SLE, systemic sclerosis, toxins, sarcoidosis and radiation.
In myocarditis, heart is dilated, flabby and pale. Small-scattered petechial hemorrhages may be seen in the myocardium. Microscopically cardiac muscles are edematous and hyperaemic. There can be infiltration of lymphocytes, plasma cells and eosinophils. Patient may be asymptomatic and sometimes recognized by the presence of an inappropriate tachycardia or abnormal ECG or from the features of heart failure.
Biochemical markers of myocardial ischemia are elevated in proportion to the extent of damage. There may be leukocytosis and raised ESR depending on the cause. Endomyocardial biopsy is diagnostic, but it is performed rarely.
Disease is self limiting. Management is mainly supportive with antibiotic therapy depending on the cause. Arrhythmias and cardiac failure should be treated accordingly. It is advised to avoid intense physical exertion during the active illness. The disease has an excellent prognosis. But in severe cases death may occur due to ventricular arrhythmias and heart failure.
Cardiomyopathy follows a chronic course in which inflammatory features are not prominent. Etiology of the disease may be unknown or associated with toxic, metabolic, degenerative, amyloidosis, myxedema, thyrotoxicosis or glycogen storage diseases although they are very rare.
Cardiomyopathies are classified according to the functional disturbances as dilated, hypertrophic, restrictive and obliterative. Histological features are non specific. Irregular atrophy and hypertrophy with progressive fibrosis may be seen.
Mostly patients are asymptomatic or presents with features of acute coronary syndrome. Chest pain is common. In severe cases, there may be associated heart failure, arrhythmias and systemic embolisation. ECG changes may be present.
Treatment depends on the type of cardiomyopathy but mainly include drugs, implanted pace makers, defibrillators or ablation. Chronic alcoholism is a recognized cause of dilated cardiomyopahty and the effect can be reversed with the cessation of alcohol consumption for 10-20 years.
The prognosis depends on the degree of impairment of myocardial function and associated complications.
What is the difference between myocarditis and cardiomyopathy?
• Myocarditis is acute while cardiomyopathy is more of a chronic condition.
• Myocarditis is usually caused my infectious agents and toxins, but cardiomypathy is mostly genetic or may be associated with degenerative conditions.
• In myocarditis features of acute inflammation in myofibrils are prominent but it is not in cardiomyopahty.
• In myocarditis cardiac markers are elevated depending on the extent of the damage.
• Myocarditis has a good prognosis.
• Management options are different in the two conditions.