Cardiomyopathy

Definition

The word "cardiomyopathy" refers to any intrinsic disease of the myocardium, or heart muscle. Such diseases may be caused by infections, exposure to toxic substances, or thiamine deficiency, and a large proportion are of unknown origin. The type of heart muscle disease produced by alcohol is known as a dilated cardiomyopathy, because one or more heart chambers are abnormally distended with blood (Bristow, O'Connell 168-176). Cardiomyopathies do not affect the valves or coronary arteries.

Nature of Cardiomyopathy

By nature, cardiomyopathy is a dangerous and serious disease. There are four main forms - dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), arrhythmogenic right ventricular cardiomyopathy (ARVC) and restrictive cardiomyopathy (RCM).

Dilated cardiomyopathy: The heart becomes enlarged and pumps less strongly. (Hein, Schaper, 292-301) The heart muscle becomes weak, thin or floppy and is unable to pump blood efficiently, leading to heart failure. The condition is often genetic and is diagnosed when other causes of heart failure, such as coronary artery disease, hypertension and valve disease, have been excluded.

Hypertrophic cardiomyopathy: This is characterized by an excessive thickening of the heart muscle. The cardiac muscle cells are usually aligned in parallel lines but here the cells become disorganized. These changes in the structure of the heart may cause rhythm disturbances and sudden death.

Arrhythmogenic right ventricular cardiomyopathy: The heart muscle is replaced by fibrous scar and fatty tissue. This is patchy in distribution, so abnormal areas may be surrounded by normal ones. The right ventricle (lower heart chamber) tends to be most affected. It is thought that abnormal genes lead to heart muscle degeneration and that fibrous and fatty tissue replaces these heart muscle cells in an attempt by the body to repair the damage. The disorganized structure leads to abnormal electrical activity which causes rhythm disturbances and sudden death.

Restrictive cardiomyopathy: This occurs when the walls of the ventricles are stiff and prevent the normal filling with blood. The causes are unknown, although it can be secondary to rare metabolic disorders. Most cardiomyopathies are inherited if either parent is affected you have a 50 per cent chance of inheriting the abnormal gene implicated. It used to be thought that dilated cardiomyopathy could be caused by pregnancy and excessive alcohol intake, but now it is recognized that putting extra stress on the heart unmasks the underlying genetic defect.

Signs and Symptoms

Symptoms and severity of cardiomyopathy vary with the patient. Some have few or no symptoms, while others develop problems such as heart failure (where the muscle is not strong enough to pump blood around the body), abnormal rhythms, and blood clots (from the slowing of blood flow). Common symptoms include shortness of breath, chest pains - usually brought on by physical exertion - palpitations and light-headedness or blackouts. (Hein, Schaper, 292-301) But for some, the first indication of a problem comes too late - unexpected sudden death in the young is usually ascribed to abnormalities of the heart muscle (cardiomyopathy) or premature coronary artery disease. When post-mortem examinations fail to reveal such abnormalities, the term sudden arrhythmic death syndrome (SAD) is ...