Atrial fibrillation

What is atrial fibrillation?

Atrial fibrillation (or AF) is an irregular heartbeat that originates in the upper chambers (or atria) of the heart. AF is a common arrhythmia and can be permanent or intermittent (known as paroxysmal). In AF the atria quiver at speeds of about 600 times per minute rather than the regular beat. The nerve tissue regulating the transfer of impulses from the upper to the lower chambers permits only a maximum of about 200 impulses to pass per minute. This means that not every ‘fibrillation beat’ can be transmitted to the lower chambers.

The speed and/or irregularity of the heartbeat can produce unpleasant palpitations. It also causes the heart to work less efficiently and can be associated with:

  • Breathlessness
  • Dizziness
  • Chest pain
  • Blackouts

Some people with atrial fibrillation have no symptoms and the condition is picked up by chance when being examined for other reasons.

It is important that atrial fibrillation is both diagnosed and treated. When the atria beat irregularly there is a small risk of blood clots forming in the heart. These blood clots can dislodge and be released into the circulation and this can cause strokes and damage to other organs. The risk of blood clots forming is increased in patients with heart disease, hypertension, diabetes or a previous history of blood clots. Treatment is usually with anticoagulant drugs to reduce the likelihood of blood clots developing.

 

What causes atrial fibrillation?

Atrial fibrillation is a common cause of palpitations and affects more than one in five people over the age of 65, becoming even more common as we get older. It is a recognised complication of many other heart conditions, such as:

  • Coronary heart disease.
  • Valvular heart disease.
  • Heart failure.
  • Hypertension.

It can also be caused by:

  • Too much alcohol
  • An overactive thyroid gland
  • Lung infections
  • Blood clots on the lung (called pulmonary emboli)

Where there is no evidence of heart disease or other identifiable cause the atrial fibrillation is known as lone AF.

How is atrial fibrillation diagnosed and treated?

Atrial fibrillation (or AF) may be suspected when a doctor or nurse takes the pulse. The diagnosis is confirmed by recording the irregular heartbeat on an electrocardiogram (ECG).

If the atrial fibrillation is intermittent (paroxysmal) it may be necessary to monitor the heartbeat for longer periods. Devices are now available that allow the heartbeat to be monitored over 24 hours or even several days while you go about your normal activities. This increases the chance of detecting any abnormalities of the heart rhythm.

Other tests are designed to identify the underlying cause. These may include:

  • Blood tests to look for electrolyte problems or thyroid disease.
  • An ultrasound scan of the heart, called an echocardiogram. This is a painless test that provides important information about the way the heart is working. It provides pictures of the heart in motion and allows the doctor to assess the pumping action of the heart and how the heart valves are working.
  • Cardiac catheterisation: an X-ray/dye procedure done under local anaesthetic that provides information about pressures in the heart, the function of the heart muscle, valves and arteries.

The treatment of atrial fibrillation depends very much on an individual patient’s circumstances. Treating the underlying cause of the AF is important as is avoiding too much alcohol and caffeine. Treatment of AF can be via one (or more) of the following regimes:

  • If the heart rate is otherwise normal and the atrial fibrillation infrequent, no treatment other than aspirin (to reduce the risk of blood clot formation) may be necessary.
  • If the heart rate is too fast, drugs such as digoxin, beta-blockers, calcium channel antagonists or other anti-arrhythmic drugs may be given to slow it down.
  • Warfarin (a drug that thins the blood) rather than aspirin may be advised for some patients thought to be at a higher risk of forming blood clots, or where cardioversion is being considered.
  • Cardioversion, performed usually under general anaesthetic, is a procedure where a controlled electric shock is given to try to restore the heart rhythm to normal. Not all patients are suitable for cardioversion. It is usually reserved for patients who have recently developed AF and do not have other heart problems.
  • Very occasionally, catheter ablation procedures and/or pacemakers are required.

Ventricular arrhythmias

Extra heartbeats originating in the lower chambers of the heart are called ventricular arrhythmias. These range from single extra beats called extrasystoles to prolonged or sustained episodes as occurs in ventricular tachycardia or fibrillation.

Ventricular tachycardia is a condition in which the larger chambers of the heart beat fast but the rate in the upper chambers remains normal. It occurs usually as a complication of heart disease and can be dangerous if untreated, leading to blackouts.

Ventricular fibrillation results from very fast, erratic and uncontrollable electrical signals in the ventricles. This is potentially a very dangerous rhythm as it causes the heart to quiver rather than beat, invariably leading to blackouts within seconds.

The treatment of ventricular arrhythmias depends on the type of rhythm disturbance detected on the ECG or heart monitors.

Sometimes no treatment is required other than lifestyle changes and avoiding triggers such as:

  • Caffeine
  • Alcohol
  • Stress

If these fail to control symptoms, medication may be required, for example:

  • Beta-blockers to slow down the heartbeat.
  • Other more complex anti-arrhythmic drugs such as amiodarone

Rarely more invasive procedures may be needed, and these include:

  • Cardioversion: a procedure usually performed under general anaesthetic where a controlled electric shock is given to try to restore a normal heart rhythm.
  • Catheter ablation: a procedure to destroy tiny abnormal areas of the heart where the arrhythmia is originating.
  • An implantable cardioverter defibrillator: a complex pacemaker for dealing with fast and potentially dangerous arrhythmias.
Copyright © SmallcogHealth