Dilated Cardiomyopathy

Authored by , Reviewed by Dr Louise Newson | Last edited | Certified by The Information Standard

Dilated cardiomyopathy is a condition caused by weakness of the heart muscle. The heart becomes enlarged (dilates) and pumps blood less well. Symptoms vary according to severity and the treatment depends on the type of symptoms and whether any complications develop. Some forms of dilated cardiomyopathy run in families.

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.

Cross-section diagram of a normal heart

Cardiomyopathy means a condition caused by a problem with the heart muscle. There are four main types:

  • Dilated cardiomyopathy - where the heart enlarges (dilates).
  • 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.

In dilated cardiomyopathy the heart muscle is weakened. The ventricles then enlarge (dilate) because their muscular walls have become weak and floppy. 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 dilated cardiomyopathy, the heart dilates because of a problem with the heart muscle itself.

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

Unknown cause

For most people the cause is not known. This is sometimes called idiopathic dilated cardiomyopathy. Another possibility is that an unknown viral infection may be responsible. About one in four people with idiopathic dilated cardiomyopathy have a familial (hereditary) form. This means that several members of their family also have dilated cardiomyopathy. 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 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 dilated cardiomyopathy.
  • 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 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). This is a rare condition which can be caused by various infections. 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. The heart muscle can also be affected by other diseases which can affect various parts of the body. A dilated cardiomyopathy may then develop in addition to other symptoms of the disease. For example, dilated cardiomyopathy sometimes occurs with the following conditions:

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:

Symptoms of heart failure

Dilated cardiomyopathy 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 dilated cardiomyopathy, 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 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.
  • Increased fluid in the legs. The build up (retention) of extra fluid in the body is called oedema. It usually 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

A 'thumping heart' (palpitations) may 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.

A doctor may suspect this condition because of:

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. More specialised tests may be performed, depending on the severity of your cardiomyopathy.

Family screening

If you have idiopathic dilated cardiomyopathy (of unknown cause) then your first-degree relatives (mother, father, brother, sister, child) may be advised to be tested (screened) by a heart specialist. 

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.

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:

General lifestyle measures

  • 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 dilated cardiomyopathy 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.
  • Don't smoke. Smoking will risk more damage to your heart.

Medication to treat heart failure

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

  • Angiotensin-converting enzyme (ACE) inhibitors, such as lisinopril or ramipril. 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 a body chemical (the enzyme angiotensin). This is involved in regulating body fluid.
  • A 'water' tablet (diuretic), such as furosemide, 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 an abnormal rate or rhythm of the heartbeat (an arrhythmia). They work by interfering with the electrical impulses in the heart.


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 enlarged (dilated) heart. When the heart beats irregularly, there is an increased risk of blood clots developing.

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 people.


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.

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 a 'thumping heart' (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 Abnormal Heart Rhythms (Arrhythmias) and Atrial Fibrillation.

Blood clots

The blood flow through the heart is slower than normal, especially when the heart is very enlarged (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 greatly reduced by taking an anticoagulant medicine (see above). An anticoagulant medicine reduces the ability of the blood to clot.

Sudden death

Sudden collapse and death without any warning occur rarely in people with dilated cardiomyopathy. This is probably due to a severe arrhythmia which may develop suddenly. Medication and/or an implantable cardioverter defibrillator (ICD) may reduce this risk.

The outlook with dilated cardiomyopathy varies and depends on the severity of the condition. However, the outlook for many people with dilated cardiomyopathy has improved during a period of ten years. This is due to new medical and surgical treatments.

In some people with dilated cardiomyopathy their heart starts pumping more efficiently again. This is seen after some of the treatments mentioned above.

Further reading and references

This is making me ridiculously anxious... few months back i wass having palpitations where i noticed my hearr rate was fairly slow 58/59 at rest i was worried went doctors had an ecg - nothibg showed...

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