Cardiomyopathy – Dilated

Understanding the normal heart

The heart has four chambers – two atria and two ventricles. The walls of these chambers are mainly made of specialised 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 (DCM) – 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 cardiomyopathy – a rare type which mainly affects the right side of the heart.

The rest of this leaflet is only about DCM.

What happens in dilated cardiomyopathy?

In this condition the heart muscle is weakened. The ventricles then dilate (enlarge) because their muscular walls are weaker and more floppy than normal. This means 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 DCM, the heart dilates because of a problem with the heart muscle itself.)

How common is dilated cardiomyopathy?

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

What causes dilated cardiomyopathy?

Unknown cause

For most people the cause is not known. This is sometimes called idiopathic DCM. Another possibility is that an unknown viral infection may be responsible. 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:

  • Alcohol, drugs and other poisons. Up to 3 in 10 cases of DCM 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 diet. If you do not get enough of certain vitamins and minerals, especially vitamin B1 (thiamine), this can weaken the heart muscle and lead to DCM. 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 infections. Some people with myocarditis develop DCM as a complication.
  • Pregnancy and childbirth. Heart muscle inflammation leading to DCM 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 DCM may then develop in addition to other symptoms of the disease. For example, DCM sometimes occurs with: sarcoidosis, amyloidosis, haemochromatosis, some forms of muscular dystrophy, vasculitis, systemic lupus erythematosus (SLE), polyarteritis nodosa, and Wegener’s granulomatosis.

What are the symptoms of dilated cardiomyopathy?

If you only have mild enlargement of the heart, you may not have any symptoms. However, if your heart becomes very dilated, 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

DCM is one cause of heart failure. There are many other causes of heart failure. Heart failure means that your heart does not pump as well as it used to. (It does not mean that your heart is going to stop at any minute.) 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 fluid building up in tissues of the lungs and body. This happens because your heart does not pump effectively. Symptoms include the following:

  • Shortness 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. It may go 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. You may be aware that your heartbeat is fast and/or irregular. 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 because of:

  • Your symptoms.
  • Changes on your electrocardiogram (ECG) – this is a tracing of the electrical activity of the heart.
  • Changes on your chest X-ray. This may show your heart is large or that there is some fluid in your lungs.
  • 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 DCM is confirmed. Further tests on the heart may be done to assess the severity of the condition.

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?

This can be difficult to predict. 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:


An arrhythmia is an abnormal rate or rhythm of the heartbeat. There are various types of arrhythmia and some are more serious than others. An arrhythmia can come and go 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 DCM. 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 a 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 an anticoagulant medicine such as warfarin (see below).

Sudden death

Sudden collapse and death without any warning occurs 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?

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 one or more of the following:

Medication to treat heart failure

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

  • Angiotensin-converting enzyme (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). This 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.

Anticoagulants such as warfarin

An anticoagulant is a medicine which helps to prevent blood clotting so easily. An anticoagulant 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 a commonly used anticoagulant.

Other types of treatment for arrhythmias

Other treatments may be an option if you develop arrhythmias. For example:

  • Cardioversion is an option for some types of arrhythmia. Whilst under anaesthetic, you are given an electric shock over the heart. This may revert the rhythm back to normal.
  • Artificial pacemakers are used in certain types of arrhythmia where the heart beats abnormally 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 an abnormal rhythm, the device can send a small electrical shock to the heart to change it back to normal.

Cardiac resynchronisation

This is a newer treatment developed to help the changes in your heart muscle. Cardiac resynchronisation tries to improve how the electrical impulses in your heart make it pump. This makes it pump more efficiently. This is done by using a pacing device. This is a small box that is placed just under the skin on your chest wall. It has been shown to improve survival for some. Unfortunately, up to 1 in 3 of people with DCM treated this way see no benefit.


Surgery has also been used to improve how efficiently the heart pumps. This is a rapidly developing area and there are various procedures used.

Heart transplant

In some cases the condition progresses and severe heart failure develops. If this cannot be treated by the methods mentioned here, the only option for treatment is a heart transplant.

Some other general points

  • Family testing (screening). If you have idiopathic DCM (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 led 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 outlook?

The outlook with DCM varies and depends on the severity of the condition. However, the the outlook for many people with DCM has improved a lot in the last ten years. This is due to new medical and surgical treatments. In some people with DCM their hearts start pumping more efficiently again. This is called reverse re-modelling. It is seen after some of the treatments mentioned above.

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

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