Atrial fibrillation

What atrial fibrillation is

In normal rhythm the sinus node tells the atria to contract in a regular, coordinated way. In atrial fibrillation (AF), chaotic and rapid electrical impulses arise in the atria (often from the pulmonary veins that drain into the left atrium), and the atria “quiver” instead of contracting. The atrioventricular node lets through only some of these impulses, so the ventricles beat irregularly and often fast.

The most important consequence is that blood does not empty well from the atrium, especially from the left atrial appendage, and forms clots. If a clot enters the circulation and reaches the brain, it causes a stroke. A stroke from AF is usually more severe than other strokes. On the other hand, uncontrolled AF with a fast rate over a long time can wear out the heart muscle and lead to heart failure.

By duration, AF is divided into paroxysmal (episodes that stop on their own within 7 days), persistent (lasting more than 7 days or needing intervention to stop it) and permanent (accepted as the permanent rhythm). Over time, AF tends to progress from the paroxysmal to the permanent form, and keeping it under control in the early stages is easier.

Symptoms

Symptoms vary greatly from person to person:

• palpitations: the heart beats fast, hard or “out of order”;
• fatigue and reduced ability to exert yourself;
• dyspnea (difficulty breathing);
• dizziness or near-fainting; rarely fainting;
• chest discomfort.

In some people AF causes no symptoms at all and is found by chance on an ECG or when the pulse is checked. The absence of symptoms does not lower the risk of stroke. For this reason it is useful for people over 65 or with risk factors to check their pulse and to agree if the doctor proposes an ECG.

Risk factors and causes

Atrial fibrillation rarely has one single cause. It is usually the result of an atrium that has been stretched, inflamed or filled with scar tissue (fibrosis) over the years, so that electrical impulses no longer spread in an orderly way. Any condition that overloads the left atrium, whether with pressure, volume or inflammation, gradually raises the chance of AF. The main factors are these:

Valve disease, especially mitral valve stenosis. When the mitral valve narrows, blood passes with difficulty from the left atrium into the ventricle; pressure in the atrium rises, the atrium enlarges and AF often appears, in a considerable share of patients with significant stenosis. In this situation the risk of clots and stroke is particularly high and treatment differs from that of ordinary AF: warfarin is needed rather than the newer drugs (DOACs). A mechanical valve also requires warfarin. Mitral regurgitation (a valve that does not close well) also enlarges the left atrium. Mitral stenosis has its own page: mitral valve stenosis; see also valve diseases.

High blood pressure is the most common controllable factor: high pressure thickens the left ventricle, makes it stiffer and raises pressure in the atrium; with time the atrium enlarges and becomes fibrotic. Heart failure and coronary artery disease (including a previous heart attack) act by the same mechanism, while previous heart surgery can cause temporary or recurrent AF.

Age over 65 is an independent factor, because the atria change with the years. Hyperthyroidism (an overactive thyroid) speeds the heart directly and can be the only cause of AF in a young person; thyroid testing is almost always part of the first assessment. Sleep apnea, obesity and diabetes go with high pressure, inflammation and a larger atrium; weight loss and treatment of sleep apnea lower the risk that AF returns.

Alcohol, even in moderate amounts in some people, can trigger AF episodes (after a party or celebration, the so-called “holiday heart”). Smoking and chronic kidney and lung disease also raise the risk. Among athletes who do years of very intense endurance training, AF is slightly more frequent. Finally there is family predisposition: AF in parents at a young age raises the chance.

AF can appear temporarily during an acute illness, after an operation or after alcohol. Even when the episode is isolated, the cardiologist assesses whether there is an underlying disease and a risk of recurrence.

How the diagnosis is made

The diagnosis is made with an ECG, which shows an irregular rhythm without regular P waves. When episodes come and go, a 24–48-hour Holter ECG or longer monitoring is used. Echocardiography shows the size of the atria, ventricular function and the valves, while blood tests check the thyroid, electrolytes, kidney function and blood count.

After the diagnosis, the cardiologist assesses three things: stroke risk (with scores such as CHA₂DS₂-VA, which take into account heart failure, hypertension, age, diabetes, previous stroke and vascular disease), bleeding risk and symptoms and their effect on daily life.

Treatment: four pillars

Treatment according to the modern approach (ESC 2024, known by the acronym AF-CARE) has four components that work together:

1. Preventing stroke. When risk is high, oral anticoagulants are given. The newer drugs (called DOACs) are preferred in most cases; warfarin is the choice for patients with a mechanical valve or moderate-to-severe mitral stenosis. Aspirin does not replace an anticoagulant. The risk of bleeding is reduced by treating modifiable factors (blood pressure, alcohol, anti-inflammatory drugs), not by stopping the anticoagulant.
2. Controlling symptoms: with rate control (beta-blockers, digoxin, calcium channel blockers) or with rhythm control: antiarrhythmic drugs, cardioversion (a controlled electric shock under brief anesthesia) or catheter ablation at specialized centers. Early rhythm control benefits some patients.
3. Treating risk factors and accompanying conditions: blood pressure control, weight loss, regular exercise, stopping or limiting alcohol, treating sleep apnea and diabetes. This component reduces the number of episodes and improves the results of any other treatment.
4. Evaluation and dynamic follow-up: regular reassessment of risk, symptoms and medicines, because the patient’s situation changes over time.

Cardioversion calls for special care: without adequate anticoagulation (usually three weeks beforehand, or a special check for clots) stroke is a risk, and anticoagulation continues for at least four weeks afterward. Never stop your anticoagulant on your own and do not start any new medicine, including herbal products or anti-inflammatory drugs, without asking your doctor.

When to see a doctor

• when you feel irregular beats that keep recurring, even if they pass on their own;
• when you have reduced exercise capacity, fatigue or new dyspnea;
• when you take an anticoagulant and have unusual bleeding or a blow to the head after a fall;
• immediately to emergency care (127) if palpitations come with chest pain, fainting, or weakness of the arm, leg or face on one side, or with speech difficulty.

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