ATRIAL  FIBRILLATION

(risk of stroke) (treatment)  (prevention)  (risk of anticoagulation)  (back to screening page)

Atrial fibrillation is the most common significant disturbance of normal heart rhythm. It is characterised by a completely irregular, usually rapid, heart beat.
In atrial fibrillation the first chambers (atria) of the heart do not contract and empty themselves of blood properly, which may result in the formation of blood clots within the chambers.
Problems arise if :
- the heart rate is too rapid to allow correct blood flow
- a clot is dislodged from the atrium and lodges in the brain, resulting in a stroke

The incidence of atrial fibrillation increases with age and is common in people over 70.
Atrial fibrillation can arise for no particular reason, but is more common in the presence of almost any other heart disease. Common associations are coronary artery disease, high blood pressure, heart failure, excess alcohol intake, an overactive thyroid gland or stimulant medication (e.g. Sudafed or Ventolin type medications or excess thyroxine).

Atrial fibrillation may initially be intermittent ('paroxysmal'), but usually becomes persistent ('chronic').
Although patients may be unaware of any symptoms, most people notice palpitations (irregular heart beat, 'thumping' in the chest or 'missed heart beats') or a rapid heart rate.
Diagnosis is easily confirmed with an ECG.

The risk of stroke in atrial fibrillation depends on age and associated heart conditions. A useful guide is the CHADS Index which gives a score as follows :
   -previous stroke                                   2
    -recent hypertension                             1
    -recent heart failure (fluid 'build up')      1
    -diabetes                                              1
    -age 75 or more                                    1
When these scores are added the risk each year of a stroke is:
    score       0           1.9 %
                    1            2.8 %
                    2            4.0 %
                    3            5.9 %
                    4            8.5 %
                    5            12.5 %
                    6            18.2 %
Anticoagulant (warfarin) treatment is normally recommended for a score of 1 or more - the greater the score, the greater the potential benefit from treatment. Anticoagulant therapy is not recommended for a score of 0 as the risk of bleeding associated with the treatment outweighs the potential benefit.

Treatment is aimed at :
1 Correcting any underlying medical problems e.g. overactive thyroid gland, or avoiding stimulants.
2 Reverting the heart to a normal rhythm - particularly in younger patients with relatively recent onset of atrial fibrillation. This may be done with medication (e.g. 'Sotalol' or digoxin) or by electrical cardioversion. Where it has been possible to restore the normal rhythm, medications may be used in an attempt to maintain the normal rhythm (usually a beta blocker or digoxin). When atrial fibrillation has been present for more than 48 hours, anticoagulation is required prior to cardioversion.
In some patients - particularly younger people with little other heart disease and relatively recent onset of atrial fibrillation - surgical 'ablative' treatment' may be considered - a procedure which attempts to interrupt the electrical conducting tissue which lines the atria so that normal heart rhythm is maintained.

In most instances atrial fibrillation will become chronic and a normal rhythm can no longer be maintained - in this situation treatment aims to :
1 Control the heart rate so that the heart beat is more efficient. The most common medications used are beta blockers (e.g. 'Sotalol' or 'Noten') or digoxin ('Lanoxin').
2 Prevent clot formation and reduce the risk of stroke by anticoagulation ('blood thinning') with warfarin ('Marevan' or 'Coumadin')
On average, warfarin reduces the risk of stroke by 60% - the greater the risk, the greater the potential benefit.
Aspirin is much less effective than warfarin (around one third as effective) and could be considered in low risk patients who can't take warfarin.

The risk with anticoagulation is serious haemorrhage including bleeding from the stomach and stroke. Haemorrhage risk is quantified on the 'Warfarin' page, and is highest in the very elderly and those with previous significant bleeding episodes. In these situations the potential risks may be greater than the potential benefits of anticoagulation.
2 to 3 percent of patients on warfarin will have a serious bleed each year while around 8 percent have a stroke prevented - the overall benefit being 5 to 6 percent of patients avoiding both a stoke and a bleed each year.
Pradaxa is a new anticoagulant approved for some groups of patients with atrial fibrillation but is not yet subsidised on the PBS. Pradaxa is at least as effective in preventing stroke as warfarin but does not have dietary and medication interactions. INR monitoring is not required. The risk of haemorrhage is similar.

Self help and prevention of atrial fibrillation include :
1 eat a 'heart healthy' diet
2 reduce alcohol and caffeine intake
3 avoid stimulants e.g. Sudafed and pseudoephedrine containing products
4 cease smoking
5 reduce salt intake
6 undertake regular moderate exercise e.g walking for 20 to 30 minutes per day