Diseases Of The Myocardium II: Cardiomyopathy

This is defined as s subacute or chronic disorder of ventricular muscle of unknown or unusual cause, often associated with endocardial involvement. It may involve the left ventricle, right ventricle or both.

Classification

1. Primary cardiomyopathy

• Familial hypertrophic obstructive/or non-obstructive cardiomyopathy, eg, idiopathic hypertrophic subaortic stenosis (IHSS), diffuse hypertrophy of the left ventricle.
• Non-familial cardiomyopathy (Idiopathic or cryptogenic cardiomyopathy)
• Endomyocardial fibrosis.

1. Secondary cardiomyopathy: All conditions causing myocarditis may lead on to cardiomyopathy. In addition, a few other conditions may be associated with cardiomyopathy. These are:

• Puerperal cardiomyopathy- this occurs as an acute or subacute cardiac disease following pregnancy and parturition.
• Metabolic causes- hyperthyroidism, hypothyroidism, diabetes mellitus, hemochromatosis.
• Toxins- especially heavy chronic alcoholism
• Infiltrations-carcinomatosis, leukemias, sarcoidosis, amyloidosis.
• Neuromuscular disorders- muscular dystrophies, heredofamilial ataxias.

Congestive or dilated cardiomyopathy: This condition is characterized by cardiomegaly due to dilatation and congestive heart failure.

Hypertrophic cardiomegaly: The hypertrophy may be generalized or localized. The localized form is seen in idiopathic hypertrophic subaortic stenosis in which the interventricular septum hypertrophies produce a dynamic obstruction to left ventricular outflow during ventricular systole. In the generalized form, the left or right ventricle shows hypertrophy without obstructive features.

Obliterative (restrictive) cardiomyopathy: This condition is characterized by fibrosis and obliteration of the ventricular inflow tract and restriction to ventricular filling. One form of restrictive cardiomyopathy is endomyocardial fibrosis (EMF) prevalent in many tropical regions, especially in Ghana and Nigeria. In EMF, the common form involves the right ventricle. Next in frequency is combined involvement of both ventricles. Rarely a purely left ventricular form is also seen. In EMF, there is fibrosis and obliteration of the ventricular inflow tracts. The left ventricular form presents with pulmonary hypertension, mitral incompetence and left ventricular failure. The right ventricular form which is more common presents with right-sided heart failure, gross enlargement of the right atrium, cardiomegaly and the disease follows a chronic course lasting for several years. Onset is in the second or third decades of life. Males are affected more than females. Atrial fibrillation and myocardial calcification may develop.