Dilated Cardiomyopathy

Understanding the normal heart

The heart has four chambers - two atria and two ventricles. The walls of these chambers are mainly made of special heart muscle called the myocardium. During each heartbeat both of the atria contract first to pump blood into the ventricles. Then both ventricles contract to pump blood out of the heart into the arteries. There are one-way valves between the atria and ventricles and also between the ventricles and the large arteries coming from the heart. The valves make sure that when the atria or ventricles contract, the blood flows in the correct direction.

What is cardiomyopathy?

Cardiomyopathy is a disorder of the heart muscle. There are four main types:

• Dilated cardiomyopathy - where the heart dilates (enlarges).
• Hypertrophic cardiomyopathy - where the heart muscle becomes thickened (hypertrophied).
• Restrictive cardiomyopathy - where the heart muscle cannot relax properly between heartbeats. This is rare.
• Arrhythmogenic right ventricular - a rare type which mainly affects the right side of the heart.

The rest of this leaflet is only about dilated cardiomyopathy.

What happens in dilated cardiomyopathy?

In this condition the heart muscle is weakened. The ventricles then dilate (enlarge) as their muscular walls are weaker and more 'floppy' than normal. Therefore, the heart does not pump blood as strongly as normal.

(Note: other common heart conditions can cause a dilated heart. For example, coronary heart disease, high blood pressure and heart valve disease. These conditions can put a 'strain' on the heart which may cause the heart to dilate. With dilated cardiomyopathy, the heart dilates because of a problem or disease of the heart muscle itself.)

How common is dilated cardiomyopathy?

Dilated cardiomyopathy (DCM) is the commonest type of cardiomyopathy. It can affect both children and adults, but is actually most common in middle aged men. About 2 in 10,000 people in the UK develop dilated cardiomyopathy each year.

What causes dilated cardiomyopathy?

Idiopathic (which means 'unknown cause')

For most people, the cause of their DCM is not known. One possibility is that an unknown viral infection may be responsible, at least for some people. About one in four people with idiopathic DCM have a familial (hereditary) form. This means that several members of their family also have DCM. It is still not clear exactly how hereditary factors may work in this condition.

Other causes

Some cases are due to known causes. There are many conditions which can cause damage or disease to heart muscle. Most are rare. They include the following:

• Alcohol, drugs and other 'poisons'. Up to 3 in 10 cases of dilated cardiomyopathy can be linked to alcohol. After years of heavy drinking, the cells of the heart muscle can become damaged and weakened. Also, heavy drinkers tend to eat poorly (see below). Some other chemicals, pesticides and illegal drugs (such as cocaine) have also been shown to weaken the heart muscle and cause DCM.
• Poor nutrition. If you do not get enough of certain vitamins and minerals, especially vitamin B-1 (thiamine), this can weaken the heart muscle and lead to dilated cardiomyopathy. This is more common in poorer countries and also in people with alcohol dependence who tend not to eat properly.
• Inflammation of the heart muscle (myocarditis) is a rare condition which can be caused by various viruses and other germs. Some people with myocarditis develop dilated cardiomyopathy as a complication.
• Pregnancy and childbirth. Heart muscle inflammation leading to dilated cardiomyopathy occurs very rarely. It is not known how or why pregnancy 'triggers' this to occur. This is called peripartum cardiomyopathy.
• Other diseases which can affect various parts of the body sometimes affect the heart muscle too. A dilated cardiomyopathy may then develop in addition to other symptoms of the disease. For example, dilated cardiomyopathy sometimes occurs with: sarcoidosis, amyloidosis, haemochromatosis, some forms of muscular dystrophy, vasculitis, systemic lupus erythematosus (SLE), polyarteritis nodosa, Wegener's granulomatosis.

What are the symptoms of dilated cardiomyopathy?

If you only have mild enlargement of the heart then you may not have any symptoms. However, if your heart becomes very dilated then symptoms will develop. Symptoms may develop gradually or quite quickly, depending on how quickly the disease progresses. Possible symptoms include the following:

Symptoms of heart failure

Dilated cardiomyopathy is one cause of heart failure (there are many other causes of heart failure). Heart failure does not mean that your heart is going to stop at any minute. It simply means that your heart does not pump as well as it used to do. The amount of 'power' that is lost from the heart varies from person to person.

For many people with DCM, heart failure is mild or moderate. Symptoms can often be treated. In some people with heart failure, the power of the heart becomes very low and then the symptoms become severe.

Symptoms of heart failure are mainly due to a 'backlog' of fluid in the lungs and body, as the heart does not pump effectively. Symptoms include the following:

• Breathlessness (short of breath). In mild cases, you may only become breathless when you exert yourself. For example, when you walk up a hill. With more severe heart failure you may become breathless whilst resting or lying flat.
• Fluid retention in the legs. Fluid retention in the body mainly affects the legs due to the effect of gravity. At first, you may notice some swelling of your feet at the end of the day. In time, the swelling may gradually affect the lower parts of the legs, or higher if it is not treated. For many people there is a gradual build up of fluid. You may not have any fluid retention in your feet or legs with mild heart failure.
• Tiredness. This can be very variable. You may find that constant tiredness is the worst symptom you have.

Other symptoms

Palpitations sometimes occur (where you have an increased awareness of your heartbeat). The heart can sometimes beat irregularly. Some people develop chest pains. If the cardiomyopathy is a result of another cause (such as alcohol excess, myocarditis, etc) then you may also have various other symptoms.

How is dilated cardiomyopathy diagnosed?

A doctor may suspect this condition from:

• Your symptoms.
• Changes on a heart tracing (ECG). This is a tracing of the electrical activity of the heart.
• Changes on a chest X-ray which may show your heart is large or may show some fluid in your lungs due to heart failure.
• An ultrasound scan of the heart called an echocardiogram. This is a painless test which can confirm that your heart is large and dilated.

Various other tests may be done to find, or exclude, causes of an enlarged heart. If no underlying cause is found then the diagnosis of 'idiopathic dilated cardiomyopathy' is confirmed. Further tests on the heart may be done to assess the severity of the condition.

Other, more specialised tests may be performed depending on the severity of your cardiomyopathy. New tests to monitor the progression of DCM are currently being developed and studied in clinical trials.

How does the condition progress?

The progress of the disease is variable. In some cases the condition remains stable or does not get much worse. Medication may keep the symptoms of heart failure away and your lifestyle may be little affected. In some people, the function of the heart gradually deteriorates. Symptoms of heart failure then get worse and need more intensive treatment.

What are the complications of dilated cardiomyopathy?

Complications occur in some cases and include the following:

Arrhythmias

An arrhythmia is an abnormal rate or rhythm of the heartbeat. There are various types of arrhythmia, some more serious than others. Sometimes an arrhythmia develops intermittently and can cause bouts of palpitations, dizziness and other symptoms. Some arrhythmias become permanent. An arrhythmia called atrial fibrillation is the most common one that develops in people with dilated cardiomyopathy. See separate leaflets called 'Arrhythmias' and 'Atrial Fibrillation'.

Blood clots

The blood flow through the heart is slower than normal, especially when the heart is very dilated. This can lead to small blood clots developing within the chambers of the heart. These may travel in the bloodstream and get 'stuck' in arteries of the body. This may lead to a stroke if clot gets stuck in an artery in the brain or to other problems. The risk of blood clots developing can be reduced greatly by taking warfarin (see below).

Sudden death

Sudden collapse and death without any warning occurs very rarely in people with DCM. This is probably due to a severe arrhythmia which may develop suddenly. Medication and/or an implantable defibrillator may reduce this risk.

What is the treatment for dilated cardiomyopathy?

There is no treatment which can reverse the changes of the heart muscle. Treatment aims to ease symptoms if they occur and to prevent complications. If you do not have any symptoms, or only mild symptoms, you may not need any treatment. Treatment which may be required includes the following:

Medication to treat heart failure

Various medicines are used to control the symptoms of heart failure. These may include:

• Angiotensin Converting Enzyme Inhibitors (ACE inhibitors). Most people with heart failure are prescribed an ACE inhibitor. There are several types and brands. These medicines prevent a build up of fluid by interfering with the enzyme 'angiotensin' (a body chemical) which is involved in regulating body fluid.
• A diuretic (water tablet) is commonly needed in addition to an ACE inhibitor. Diuretics work on the kidneys and make you pass out extra urine. This helps to clear excess fluid that builds up in the body. There are different types and brands of diuretic. The dose depends on how bad your symptoms are and can be increased if necessary if your fluid retention becomes worse.
• A beta-blocker, such as bisoprolol or carvedilol, may be prescribed in addition to an ACE inhibitor and diuretic. Beta-blockers have a protective effect on the heart muscle.

Medication to treat arrhythmias which may develop

There are various 'anti-arrhythmic' medicines (for example, amiodarone) which are used to treat and to prevent arrhythmias. They work by interfering with the electrical impulses in the heart.

Warfarin

This may be advised if you develop atrial fibrillation or have a very dilated heart. When the heart beats irregularly, there is an increased risk of blood clots developing. Warfarin is an anticoagulant, which means it helps to prevent blood clotting by thinning the blood.

Other types of treatment for arrhythmias

Other treatments may be an option if you develop certain types of arrhythmia. For example:

• Cardioversion may be an option for some types of arrhythmia. Whilst under anaesthetic, you are given an electrical shock over the heart. This may revert the abnormal rhythm back to normal.
• Artificial pacemakers are used in cases of arrhythmia where the heart beats very slowly (complete heart block) and in certain other situations. An artificial pacemaker is a small device which is inserted just under the skin on the upper chest. Wires from the pacemaker are passed through veins into the heart chambers. The pacemaker can then stimulate the heart to maintain a regular normal heartbeat.
• Implantable cardioverter defibrillators (ICDs) are sometimes used in certain situations - especially if you are at risk of developing serious and life threatening arrhythmias. They are small devices which are similar to pacemakers and are inserted under the skin in the upper chest. Wires are passed through a vein to the heart. The device monitors the heartbeat. If it detects a change to an abnormal rhythm, the device can send a small electrical shock to the heart to stop the abnormal rhythm.

Heart transplant

In some cases the condition progresses and severe heart failure develops which cannot be treated by medication. Heart transplant may then be the only option for treatment.

Some other general points

• Family testing (screening). If you have dilated cardiomyopathy of 'unknown cause' then your first degree relatives (mother, father, brother, sister, child) may be advised to be checked by a heart specialist.
• Weight. Try not to become overweight which can put an extra strain on your heart.
• Alcohol. Your doctor may advise you not to drink alcohol, or only a small amount of alcohol, as it can have lead to the heart muscle being weaker. If your DCM is due to excess alcohol alone then stopping drinking alcohol before serious damage has occurred to your heart is likely to improve your cardiomyopathy and your heart may even completely recover.

What is the prognosis (outlook)?

The prognosis with DCM varies and depends on the severity of the condition. However, overall, the the outlook for people with DCM has improved a lot in the last ten years due to new drug treatments.

Further help and information

Cardiomyopathy Association

Unit 10, Chiltern Court, Asheridge Road, Chesham, Bucks, HP5 2PX
Freephone: 0800 018 1024 or Tel: 01494 791224 Web: www.cardiomyopathy.org