Cardiomyopathy is any disease of the heart muscle that weakens the force of cardiac contractions, thereby reducing the efficiency of blood circulation. Cardiomyopathies may be the result of infectious, metabolic, nutritional, toxic, autoimmune, or degenerative disorders. However, in many cases, the cause is unknown.
There are three principal forms of the condition: hypertrophic, dilated, and restrictive cardiomyopathy. In hypertrophic cardiomyopathy, the heart muscle is abnormally thickened. This condition is usually inherited. In dilated cardiomyopathy, which is often of unknown cause, metabolism (chemical activity) of the heart muscle cells is abnormal and the heart’s walls tend to balloon out under pressure. Restrictive cardiomyopathy is a condition in which the heart walls are unusually inflexible, so that the heart cannot fill sufficiently with blood. It is often caused by scarring of the endocardium (the inner lining of the heart) or by amyloidosis (infiltration of the muscle with a starchlike substance).
Symptoms and signs
Symptoms of cardiomyopathy include fatigue, palpitations, and chest pain. Palpitations may be due to an abnormal heart rhythm such as atrial fibrillation (rapid, uncoordinated contractions of the upper chambers of the heart). The condition may lead to heart failure, in which the pumping action of the heart becomes less efficient. Symptoms of heart failure include breathing difficulty and oedema (abnormal fluid accumulation in body tissues).
A chest X-ray may show enlargement of the heart, and echocardiography (an ultrasound technique for imaging the structure and movement of the heart) may show thickened heart muscle. A biopsy (small tissue sample removed for microscopic analysis) of heart muscle may reveal muscle cell abnormalities.
Symptoms of cardiomyopathy may be treated with diuretic drugs to control heart failure and antiarrhythmic drugs to correct the abnormal heart rhythm. In many cases, heart muscle function deteriorates, and the only remaining option is a heart transplant.