The heart normally beats in a regular fashion at around 70-80 beats per minute. This varies during the day with the heart rate being slower during periods of rest and increasing during periods of exercise. There are many types of irregular heart beat but the commonest is atrial fibrillation (AF), where the heart beats in a completely irregular way. This affects around 1% of the population. Atrial fibrillation occurs because the normal organised flow of an electrical impulse through the heart to leading to contraction has been disturbed. In the two collecting chambers of the heart, the electrical activity has become completely random which has two effects, irregular electrical stimulation of the two pumping chambers of the heart (ventricles) which leads to an irregular heartbeat and also a loss of pumping function in the atria. The irregular heart beat can lead to symptoms and the loss of contraction in the atria can lead to clot formation in certain areas of the atria.
Sometimes in atrial fibrillation the heart beats in an irregular fashion and also quickly. Fast AF (where the heart beats faster than 100 beats per minute) means that the heart does not have sufficient time to fill with blood between hearbeats and this can lead to shortness of breath and the inability to be able to do much physical activity in addition to palpitations, the sensation of being aware of your own heartbeat.
AF can be present all the time or intermittently. Intermittent AF that lasts up to 7 days and then terminates is called paroxysmal AF and recurrent AF is where more than 1 such episode has occurred. Persistent AF is where the AF has lasted more than 7 days and permanent AF is where the AF has lasted more than 1 year.
Symptoms of Atrial Fibrillation
The symptoms of AF are variable and wide ranging. They also vary depending on the heart rate. The commonest symptom is palpitation, the awareness of your own heart beat. Other symptoms that occur in AF include tiredness, shortness of breath, a reduced ability to undertake physical activity, dizzynes and occasionally chest pain.
Risk Factors for Atrial Fibrillation
Atrial fibrillation may occur in otherwise normal hearts. There are also a large number of conditions that increase the risk of developing atrial fibrillation. In general they all tend to lead to stretching (or dilatation) of the left atrium or increase the likelihood that disorganised electrical impulses develop in the atria. Causes related to the heart include a heart attack, problems with some valves of the heart (either leaking or narrowing), heart defects that you are born with (such as holes in the heart), problems with the heart muscle (such as hypertrophic cardiomyopathy) and heart failure. Other general causes include high blood pressure, disease of the thyroid, alcohol, tea coffee and other caffeinated drinks, being overweight, various diseases of the lungs and also some infections.
Diagnosing Atrial Fibrillation
There are a number of tests to look for and to confirm the presence of AF. If you have permanent AF then AF can be diagnosed by taking your pulse and performing a 12 lead ECG. If the AF is intermittent then the ECG may be normal and monitoring for a longer period is required. This can be from 24 hours (or multiples of 24 hours) using external monitors attached to the skin up to long term monitoring with monitors that are implanted under the skin lasting for 1-2 years. Other tests that are often performed include an echocardiogram to ensure that the heart is structurally normal and routine blood tests. Both of these investigations may find a cause for the AF which if treated may also treat the AF.
Treating Atrial Fibrillation
There are 3 parts to the treatment of AF; firstly treat the cause (if any), secondly treating the AF itself and finally preventing the formation of clots in the collecting chambers of the heart.
Treating the cause can include things such as treating the thyroid disease, treating infection and also reducing caffeine and alcohol intake.
For the treatment of the AF itself there are 2 approaches called rhythm and rate control. For rhythm control (which means to try to keep the heart in a normal rhythm and) drugs are commonly used which include medication such as a beta blocker (eg Atenolol or Sotalol). Another option is to perform a cardioversion. This is where you are put to sleep for a short period of time and an electrical shock is applied to the heart to change the rhythm from AF back to a normal rhythm. For rate control the idea is to use medication to reduce the heart rate so that the heart can pump effectively. Medications can include beta blockers, digoxin and other drugs.
For both intermittent and permanent AF there is a procedure called an ablation which in some patients can restore a normal heart rhythm. This is where are series of small tubes are passed through the veins in the leg into the collecting chambers of the heart (atria) under X ray guidance. The electrical activity can then be studied in detail and then a series of scar lines made using radiofrequency ablation will remove the abnormal electrical activity in the heart and restore normal electrical activity which will lead to a normal, regular heart beat.
The final consideration is the risk of clots forming in the heart. These are important as they can break off and then lead to a stroke. There are several risk factors that increase the chances of clot formation in the heart if you have AF and these include your age, the presence of other conditions such as diabetes and high blood pressure and other diseases of the heart such as heart failure. The risk of a stroke is determined by using the CHADS2VASC score. This score is then used to determine if agents that thin the blood (anticoagulants) are needed to reduce the risk of clot formation. The most commonly used anticoagulant is Warfarin which needs careful monitoring of the blood to ensure that your blood is sufficiently thinned but that it is not to thin (which increases the chances of bleeding). There are new drugs that have been developed which work differently to Warfarin but have a similar effect. These are called NOAC’s (new oral anticoagulants) and include Dabigatran, Apixaban and Rivaroxaban.