Diseases involving the heart muscle are called cardiomyopathy (‘cardio’ stands for heart, ‘myo’ stands for muscle and ‘pathy’ for disease). In general, the term is used to denote primary disease of the heart muscle and not damage to the heart muscle secondary to diseases of the blood vessels or the heart valves.
Common types of cardiomyopathy
Cardiomyopathies are generally classified into three:
In restrictive cardiomyopathy, there is restriction of filling of the affected ventricle (lower muscular chambers of the heart). It may affect either of the ventricles alone or both ventricles together. A type of restrictive cardiomyopathy which was common in tropical regions is known as endomyocardial fibrosis. Endomyocardial fibrosis usually involves the right ventricle than the left ventricle. In this condition, the apex and body of the right ventricle are obliterated and the outflow region is enlarged. The stiff right ventricle makes emptying of the right atrium (thin wall upper chamber of the heart) more difficult and hence it enlarges. The affected individuals have an enlarged tummy and swelling of legs (edema) along with shortness of breath. Blood clots may form in the enlarged right atrium.
In this variety, the ventricular muscle is thickened, commonly affecting the left ventricle. Thickened muscle may obstruct the outflow of blood from the left ventricle. Then it is called hypertrophic obstructive cardiomyopathy (HOCM). This variety is an important cause of sudden death in athletes. It is also transmitted genetically. First degree relatives of an affected individual has about 50% probability of being affected. Thickened left ventricular muscle has difficulty in filling as the heart relaxes after pumping out blood. This increases the filling pressures of the heart and leads to congestion of the lungs, causing breathlessness on exertion. Thickened heart muscle can also generate abnormal heart rhythms which could be life threatening.
In the dilated variety of cardiomyopathy, the heart muscles are flabby and the ventricles are dilated. Dilated cardiomyopathy can also occasionally be transmitted genetically. As the ventricular muscles are very weak, they are unable to pump blood sufficient to the needs of the body. This causes fatigue and breathlessness. The enlarged ventricles can also lead to blood clot formation in these chambers due to the sluggishness of blood flow. Clots can move out from the heart and cause obstruction to any of the blood vessels. If a clot obstructs a blood a vessel of the brain, a stroke results.