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Atrial fibrillation
Atrial fibrillation (commonly called "afib" or AF) is the most common cardiac arrhythmia. It affects between 1 and 2% of the population. Its frequency increases with age, for example, it affects 0.5% of patients aged 40-49 years, 7% of patients aged 60-69 years and 13% of patients aged 80-84 years.
What is atrial fibrillation?
Atrial fibrillation is an abnormal electrical activation of the upper chambers of the heart (the atria) that causes them to contract rapidly and irregularly, which in turn leads to irregular contraction of the ventricles. There is some degree of stagnation of blood in the atria due to their abnormal contraction and blood clots may form.
There are 2 forms of atrial fibrillation:
- Paroxysmal: this is an intermittent form with episodes lasting less than 7 days. The rest of the time, the patient is in normal rhythm = sinus rhythm.
- Persistent: when episodes last 7 days or more
Up to one in five patients progress from the paroxysmal form to the persistent form in one year’s time.
Causes of atrial fibrillation
The mechanisms of atrial fibrillation are complex and likely multiple and are the subject of much research. Many heart diseases may increase the risk of atrial fibrillation:
- High blood pressure
- Myocardial infarction (heart attack)
- Heart failure or decreased heart function ("weak heart")
- Heart valve disorders including mitral valve leak and stenosis
- Cardiac surgery procedures
Certain medical problems and behaviours are associated with an increased risk of developing AF:
- Thyroid diseases
- Excessive alcohol consumption and alcoholism
- Sleep Apnoea
- Obesity
- Lung diseases such as Chronic Obstructive Pulmonary Disease (COPD)
- Diabetes mellitus
- Chronic kidney disease
- Age
- Lack of physical exercise
Symptoms of Atrial Fibrillation
They vary from patient to patient, a number of patients do not feel they are in atrial fibrillation. Nearly a quarter of AF patients experience a loss of quality of life or disruption of daily life due to AF.
Common symptoms are :
- Palpitations, feeling your heart beating irregularly, fluttering, "pounding"...
- Chest pain or tightness
- Dizziness, lightheadedness
- Exercice intolerance, shortness of breath on exertion
- Fatigue, anxiety
- Need to urinate
Severe symptoms of AF can include :
- Shortness of breath at rest or with minimal exertion...
- Loss of consciousness or malaise without loss of consciousness
Implications of atrial fibrillation
Large epidemiological studies have found a correlation (association that does not establish causality) between atrial fibrillation and certain variables:
- Increased all-cause mortality
- Increased cardiovascular mortality
- Increased risk of ischemic stroke
- Increased risk of heart failure
- Increased risk of dementia
Complications of Atrial Fibrillation
Complications are related on the one hand to the formation of clots inside the heart and on the other hand to the rapid and disorganised functioning of the cardiac contraction.
Blood clots can form in the left atrium in patients with atrial fibrillation and fragments or clots can migrate from the heart to the brain, causing an ischaemic stroke, or migrate to other organs (eyes, kidneys) or to the major arteries in the arms or legs. The risk of developing blood clots can be assessed by your doctor. Patients at moderate or high risk of blood clots are advised to take blood thinners or anticoagulant medications.
The other type of complication related to atrial fibrillation is due to the effect of the rapid and disordered contraction of the heart chambers which may in some cases cause decreased heart function or heart failure. Treatment of atrial fibrillation improves heart function.
How is atrial fibrillation diagnosed?
Atrial fibrillation is usually diagnosed by recording the electrical activity of the heart on a 12-lead electrocardiogram (ECG or EKG).
The other ways to diagnose atrial fibrillation are :
- Holter ECG recording for 24 hours or more: it shows the duration of atrial fibrillation
- Interrogation of implantable pacemaker, defibrillator or holter in patients who have been implanted
- Connected devices/wearbles validated for AF diagnosis: Apple watch 3 and above, Huawei watch: as these devices can make errors, it is advisable to have a confirmation with an electrocardiogram in case of irregular rhythm alert
-Personal ECG or iECG: Kardia Mobile, Apple watch 4 and above, Withings move ECG: these devices have an automatic interpretation but it is advisable to show the traces to your cardiologist.
Treatment
The treatment consists of 3 parts: maintaining the normal rhythm, reducing the risk of blood clots and treating risk factors.
a) Maintaining normal rhythm (sinus rhythm)
An electrical shock (electrical cardioversion) can be used to reset the electrical activity of the heart and allow sinus rhythm to resume, if AF is poorly tolerated (e.g. low blood pressure), this can be done on an emergency basis. In other cases, it is recommended to take 3 weeks of anticoagulants and for 4 weeks after the electric shock. Sometimes, a transoesophageal echocardiogram (TOE or TEE) may be recommended before the electric shock to check for the absence of clot in the left atrium.
There are several ways to maintain sinus rhythm
- Specific medications called antiarrhythmics that can be taken on demand in the event of an AF episode (“pill in the pocket”) or continuously to prevent atrial fibrillation from returning, they can have some side effects and sometimes lose their effectiveness over time.
Non pharmacological methods :
- Catheter ablation, which is a procedure where thin electrical wires are introduced through the groin to selectively destroy limited areas of the atria in order to prevent the recurrence of AF.
- Pacemaker implantation is used to treat the slow heartbeat that affects some people with AF. This may allow the uptitration of heart-slowing drugs that can be used to treat AF. In some patients, catheter ablation can be used to disconnect the atria from the ventricles so that the heart rhythm is determined solely by the pacemaker, which means it is always regular.
Controlling the heart rate (rate-control)
In some situations, especially acute situations, medications which slow down the heart rate are given but they are not intended to convert atrial fibrillation fibrillation to sinus rhythm. Some of the symptoms of atrial fibrillation come from the very fast heartbeat, so slowing down the heart rate can improve the symptoms.
The decision to control the rhythm - maintaining sinus rhythm or to control the rate - staying in atrial fibrillation depends on the severity of symptoms, patient-related factors and patient preference, this will be discussed with your doctor.
b) Reducing the risk of blood clots
Patients who are at risk of blood clots usually receive blood thinning drugs or anticoagulants to decrease the risk of clotting. There are two types of these drugs, the vitamin K antagonists (VKA), which require regular blood tests and whose effect is influenced by certain types of food, and the new oral anticoagulants (NOACs or DOACs), which are as effective as vitamin K antagonists but do not require frequent blood tests. Your doctor will discuss with you which blood thinner is best for you.
Patients at risk of blood clots with a contraindication to anticoagulants or a history of major bleeding may be protected by the implantation of a prosthesis in the left atrium to prevent the formation of clots.
c) Addressing risk factors
An important part of treating atrial fibrillation is controlling the risk factors that increase the risk of atrial fibrillation.
Hypertension: Patients with high blood pressure should aim for normal blood pressure: <140/90mmHg in consultation or <135/85mmHg on home blood pressure monitoring
Coronary artery disease: Patients with narrowing of the arteries of the heart (coronary arteries) will be treated with medications, stent implantation or even surgical coronary bypass surgery if necessary.
Overweight/obesity: weight loss is recommended for patients with a body mass index > 25kg/m² (weight in kilograms divided by height in meters). Losing 10% of body weight may be a goal recommended by your doctor.
Heart failure: your doctor will prescribe the most appropriate drug treatment for heart failure patients.
Smoking: patients who are smokers will be advised to stop smoking.
Alcohol: in case of excessive alcohol consumption, a reduction in consumption is recommended (less than 3 units of alcohol per day).
Exercise: Regular exercise is recommended for the reduction of cardiovascular and atrial fibrillation risk.
Respiratory diseases (COPD): Patients with COPD can be referred to pulmonology and receive inhaled treatments.
Sleep Apnea Syndrome: Patients with sleep apnea should be treated with weight reduction and continuous positive airway pressure (CPAP) machines.
References :
Patient education: Atrial fibrillation (Beyond the Basics)
Wadke, Dis Mon 2013
Wilke, EP Europace 2013
Schnabel, Heart 2018
Rienstra, Circulation 2012
Odutayo, BMJ 2016
Kim, Eur Heart J 2019
AF ESC guidelines 2016
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