Atrial fibrillation (AF)
What is it ?
Atrial fibrillation is a fast heartbeat (tachyarrhythmia) of the upper chambers of the heart (atria). The abnormal impulses tend to originate form the pulmonary veins and spread to the atria. There, the impulses create a multitude of short-circuits and the function of the atria becomes disorganised. As a result, the main pumping chambers (the ventricles) pump irregularly and this is felt as palpitations. The irregular contraction of the atria also leads to pooling of blood and formation of clots inside the heart. These can then travel to the brain to produce a stroke, or to other organs to cause damage (pulmonary embolism, peripheral embolism, etc.)
There are many possible causes of atrial fibrillation, including:
Alcohol (particularly binge dringing)
Coronary artery disease
Sick sinus syndrome
Cardiac valve defects
Congenital heart defects
AF may also occur in people who do not have heart disease. In this case, it is called 'lone' atrial fibrillation.
Some patients may have no symptoms at all. The condition may have been discovered incidentally, perhaps after going to the doctor's for an unrelated complaint. Other patients, however, may feel the following:
Palpitations, which are sensations of a racing, uncomfortable, irregular heartbeat or a flopping in your chest.
Shortness of breath
Types of AF
AF is classified according to its duration:
Paroxysmal AF: 'Paroxysmal' means intermittent. Episodes occur suddenly and stop without treatment within seven days (usually within two days). The period of time between each episode (each paroxysm) can vary from patient to patient.
Persistent AF: 'Persistent' means' that AF lasts longer than 7 days. However, the heartbeat can be reverted back to a sinus rhythm (normal rhythm) with cardioversion treatment. Persistent AF tends to reccur so it may come back again after a successful cardioversion.
Permanent AF: 'Permanent' means long-term. Cardioversion may have been tried without success. People with permanent AF receive 'rate-control' treatment, in order to to bring their heart rate back down to normal, but the rhythm remains irregular (see below).
The diagnosis is first suspected when there is an irregularly irregular pulse, ie. a pulse with no particular rhythm pattern. The confirmation of the diagnosis is with a heart trace (ECG).
How to check your pulse
To check your pulse:
Put one of your hands out so you’re looking at your palm.
Use the index/first finger and middle finger of your other hand and place the pads of these fingers on the inside of your wrist.
You should place them at the base of your thumb near where the strap of a watch would sit.
Press lightly and feel the pulse. If you can’t feel anything press slightly harder or move your fingers around until you feel your pulse.
Once you’ve found your pulse, continue to feel it for about 20-30 seconds.Feel the rhythm of the pulse and check if it’s regular or irregular.
Altenatively, there are now some clinically validated mobile phone apps that may be useful for monitoring the pulse. Please note that these applications DO NOT provide a reliable diagnosis - this must be done by the cardiologist.
Ambulatory ECG monitoring: this is to see if and when AF is present and whether it gives rise to a slow or a fast pulse. These are geared towards assessing how fast or slow the main pumping chambers (ventricles) are contracting throughout a normal day.
Implantable loop recorder (or 'Reveal' device): This is an implantable device that may be useful in the long-term detection and follow-up of patients with atrial fibrillation.
Echocardiogram: This is to see whether your heart is structurally normal. Attention will be paid to weakness of the heart muscle (cardiomyopathy) and heart valves.
Coronary artery CT and/or angiogram: if coronary heart disease is suspected as the cause of AF, a coronary artery CT (CTCA) or a coronary angiogram may be required.
The aim of treatment is:
To try to get back to a normal rhythm (sinus rhythm), although this may not be possible in some patients
To control the heart rate
To prevent strokes
Conversion to a normal rhythm
This can be achieved with:
Direct-current cardioversion (DC cardioversion): This involves application of an electric shock to the chest under sedation.
Medication: Drugs include flecainide, sotalol, amiodarone or dronedarone.
Ablation: This procedure involves an operation with catheters (see ablation). Ablation is very effective for patients with intermittent ('paroxysmal') AF, but less effective in patients with persistent and permanent AF.
Controlling the heart rate
This can be achieved with drugs. If drugs are not effective, the combination of a pacemaker an atrioventricular node (AV node) ablation is an alternative.
AF slows down the passage of blood through the atria and this leads to formation of clots inside the heart which travel to the brain and cause a stroke or a transient ischaemic attack (TIA). Clots can also travel to other organs, such as the lungs (pulmonary embolism), the intestine (mesenteric embolism) and the kidneys (renal embolism).
In the past, aspirin as thought to provide protection against strokes in patients with AF. This, however, has proven not to be the case and we now know that aspirin does not protect from strokes in patients with atrial fibrillation.
See below for the factors that are considered in the decision to recommend aspirin or oral anticoagulants, such as warfarin, synthrome and the new oral anticoagulants, such as dabigatran, apixaban, edoxaban and rivaroxaban. With warfarin and synthrome, you will to attend the anticoagulant clinic weekly dose adjustment. Once the blood thinnning is stable, you will need only attend the clinic every six to eight weeks. You will need to keep your warfarin level stable. Some substances, such as alcohol, certain food items and other medication, including cough remedies and herbal cures may affect the warfarin level.
Note that aspirin and clopidogrel are less eﬀective than anticoagulants than warfarin, synthrome or the new oral anticoagulants.
CHA2DS2-VASc score for stroke risk in AF
This scoring system allows the calculation of the risk of stroke in patients with AF who do not have heart valve disease:
Congestive Heart Failure 1
Age >75 years 2
Age between 65 and 74 years 1
Vascular disease 1
Diabetes mellitus 1
The European Society of Cardiology (ESC) guidelines recommends:
CHADS2 score of 2 and above: oral anticoagulation therapy (OAC)
CHADS2 score is 0-1, other stroke risk modifiers should be considered: (i) If 2 or more risk factors (essentially a CHA2DS2-VASc score score of 2 or more), OAC is recommended; and (ii) If 1 risk factor (essentially a CHA2DS2-VASc score score=1), OAC or aspirin (OAC preferred) is recommended, and patient values and preferences should be considered.
if CHA2DS2-VASc score score of zero: such patients are 'truly low risk', and thus, the ESC guideline recommendation is to prescribe either aspirin or no antithrombotic therapy, but 'no antithrombotic therapy' is preferred.
The new oral anticogulants are not suitable for patients with AF due to valvular disease. In this case, warfarin should be considered.
Video: the electrical system of the heart
Video: Effects of AF
Example of a mobile phone application