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Atrial fibrillation, also called AF, is the most common heart rhythm disturbance, affecting at least 1% of the UK population. It increases in prevalence with age, affecting at least 10% of people over the age of 80 years. It is important for two main reasons: (i) AF directly causes a quarter of all strokes and (ii) AF can cause debilitating symptoms. In some patients, AF is a potentially reversible cause of heart failure. Early detection is therefore key to permit effective stroke prevention, to control symptoms associated with AF and to promote healthy heart function.
Symptoms caused by AF
Atrial fibrillation is characterized by an irregular heart rhythm, which may vary in rate from very slow (<40 beats/minute) to very fast (>200 beats/minute). Although this often occurs in the presence of known medical problems, for example high blood pressure, heart valve problems, overactive thyroid gland, many patients with atrial fibrillation are otherwise entirely fit and well and the diagnosis is made incidentally by means of a fortuitous ECG or pulse check by a vigilant doctor or nurse. When present, symptoms can include palpitations, fatigue, breathlessness or dizzy spells. Importantly, symptoms can be episodic depending on the type of AF present. Your specialist will discuss this with you in detail.
Types of AF
Atrial fibrillation is currently classified according to duration of episodes of continuous AF. Paroxysmal AF lasts continuously for less then seven days; Persistent AF lasts continuously for between one week and one year; Longstanding persistent AF is continuous for longer than a year. The risk of stroke does not dependent on the type of AF – all carry an equivalent risk and all merit anticoagulation according to calculated stroke risk. The treatment for the heart rhythm disturbance per se will vary according to the type of AF.
Do I have AF?
Atrial fibrillation can only be confirmed by means of an electrocardiographic recording ie symptoms of palpitations or an irregular pulse are not enough to make the diagnosis. For a patient in AF all the time, a 12 lead ECG will suffice to make the diagnosis. For a patient with episodic, or paroxysmal, AF, a period of continuous monitoring will be required.
Treatments for AF
Anticoagulation (use of blood thinning medication) has been proven beyond doubt to reduce the risk of stroke in AF. While anticoagulation carries a small risk of causing bleeding, anticoagulation in AF is only recommended in those patients where (a) the risk of stroke occurrence far outweighs the risk of bleeding on an anticoagulant and (b) the benefit of stroke prevention outweighs the risk of bleeding on an anticoagulant. Medications currently used to reduce stroke risk in AF include warfarin, dabigatran, rivaroxaban and apixaban. Aspirin is ineffective in preventing AF-related strokes. Your specialist will discuss your individual stroke risk with you and make the most lifestyle-appropriate recommendation for you.
Drug therapy does not cure AF and is most often recommended in 2 situations. If you have symptomatic, paroxysmal AF, it would be usual to use an antiarrhythmic medication designed to suppress the episodes of symptomatic AF. If you have continuous AF, it may be equally appropriate to use medication either to restore a normal heart rhythm or simply to control the heart rate within the normal range while remaining in AF. Every patient is different and your treatment will be tailored to you.
Direct Current Cardioversion
Cardioversion does not cure AF and is only appropriate for patients in continuous AF or in an emergency situation. The procedure is done as a day case. Under general anaesthetic lasting approximately 10 minutes, 2 sticky patches are placed on the front and back of the chest. A controlled electric shock is delivered between the patches. The shock has the effect of silencing the erratic atrial impulses allowing recovery of normal heart rhythm function. Cardioversion is effective in terminating AF in the majority of appropriately selected patients however the AF recurrence rate is high and repeated cardioversions separated by a matter of a few months is not appropriate in most patients with AF.
Pacemakers do not cure AF. Some patients with AF may suffer with slow irregular heart rates or may experience slow heart rates as a result of the medication they take for AF. In this situation, a pacemaker implantation may be of benefit. Similarly, in patients with AF where the heart rate is rapid and difficult to control with medication, it is possible to implant a pacemaker and to ablate the atrioventricular junction of the heart in a short day case procedure. This simple procedure electrically disconnects the fibrillating upper cardiac chambers (the atria) from the lower cardiac chambers (the ventricles), such that the heart rhythm is now determined entirely by the pacemaker and is therefore completely regular. This procedure is effective in selected patients but is irreversible.