Heart muscle disease

There are three main types of heart muscle disease, all of which can cause a heart attack.

The most common - hypertrophic cardiomyopathy - is the biggest cause of sudden death in people aged under 30.

The warning signs of heart muscle disease - cardiomyopathy - are sudden loss of consciousness, rapid palpitations (arrhythmias), pain in the chest (angina) and unexplained breathlessness.

Primary cardiomyopathy has no specific causes, unlike secondary cardiomyopathy which may be caused by hypertension, heart valve disease, artery diseases or congenital heart defects as well as disease affecting areas other than the heart.

Hypertrophic cardiomyopathy

The heart muscle thickens greatly without any obvious cause. In most cases the disease is hereditary, resulting from a gene abnormality.

The disease is thought to affect at least 125,000 people in the UK.

The muscle mass of the left ventricle is larger than it should be, causing the mitral valve to touch the dividing wall between the two sides of the heart - the septum.

The effect of the narrowing of the passage is to obstruct the blood flow out of the heart. The valve may leak.

The muscle is stiff and has difficulty relaxing, increasing the amount of pressure required to expand when blood flows into the heart. This reduces the blood holding capacity of the heart.

The condition can be present in the foetus and cause stillbirth, or may develop in infancy. But, more usually, it develops during childhood or early adulthood.

Dilated Cardiomyopathy

Dilated, or congestive, cardiomyopathy is more common and occurs due to enlarging and stretching of the heart cavity, weakening the heart so it does not pump normally.

The heart muscle becomes weak and too flexible, preventing it pumping blood efficiently around the body.

Breathlessness results as fluid builds up in the lungs, congesting them. This is called left heart failure.

There may also be right heart failure, where fluid accumulates in the tissues and organs of the body, usually the legs and ankles, and the liver and abdomen.

The cause of the condition is unknown in many cases, but it can be caused by a virus, auto-immune diseases such as rheumatoid arthritis, excessive consumption of alcohol or, rarely, as a result of pregnancy - peri-partum cardiomyopathy.

Shortness of breath, palpitations, tiredness, swollen ankles and angina are common symptoms.

Blood clots often form because the blood is flowing more slowly through the heart.

Arrhythmogenic Right Ventricular Cardiomyopathy

Heart muscle is replaced by fibrous scar and fatty tissue - the right ventricle tends to be most affected.

The right side of the heart may first thicken and later dilate - become thinner.

It may lead to disordered electrical activity, and in some cases problems with the heart's pumping action.

Restrictive Cardiomyopathy

Restrictive cardiomyopathy is the least common form and occurs when the middle layer of the heart cavity wall - the myocardium - is excessively rigid, impairing the filling of the ventricles with blood between heartbeats.

Diagnosis and treatment

The disease can only be identified by screening and the Cardiomyopathy Association in the UK argues this should be extended - currently at risk families are checked.

Conditions are diagnosed using an electrocardiogram, which measures heart beats, and an echocardiogram, which produces a picture of the heart showing any thickening of the muscle.

Cardiac catheterisation, exercise testing, Holter monitoring and other tests may also be necessary.

Complications include blood clots, heart failure, disturbed heart beats and sudden death.

There is no cure but drugs - including ACE inhibitors, beta blockers, digoxin, diuretics and warfarin - surgery or pacemakers may relieve symptoms or prevent full development of the condition. Heart transplant may be used in extreme cases.