Atrial fibrillation: causes and therapies

Atrial fibrillation is one of the most common cardiac arrhythmias. The heart beats irregularly. Without treatment, there is a risk of serious consequences, such as a stroke

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The atria often move quickly and irregularly in atrial fibrillation

© W & B / Dr. Ulrike Möhle

Atrial fibrillation - briefly explained

Atrial fibrillation is a heart rhythm disorder in which the atria move quickly and uncontrollably (fibrillation). This leads to an irregular heartbeat and can encourage the formation of blood clots (thrombi) in the atrium. If such clots are washed from the heart into the blood vessels, the result can be a stroke, for example.

Atrial fibrillation can have a number of causes, including high blood pressure, certain heart conditions, or excessive alcohol consumption. Some forms of atrial fibrillation often start out in attacks and go away on their own after minutes or hours.

The doctor diagnoses atrial fibrillation using the typical electrocardiogram. Anticoagulants help prevent thrombi from forming in the left atrium. In some cases, the normal heart rhythm can be restored by a so-called cardioversion with medication or an electric shock. A form of therapy that is preferred today is so-called catheter ablation, in which certain areas in the left atrium are obliterated. In some cases, especially in older people with minor symptoms, therapy with drugs that do not eliminate the atrial fibrillation but only ensure that the heart does not beat too quickly is an option.

Atrial fibrillation is an abnormal heart rhythm. A persistently irregular, usually significantly accelerated heartbeat is characteristic.

frequency

The incidence of atrial fibrillation in the general population averages 2.2 percent. It increases significantly with age and reaches a frequency of up to 16 percent in 70 to 80-year-olds.

Atrial fibrillation is often not noticed at all - especially the atrial fibrillation (paroxysmal atrial fibrillation) that occurs at the beginning. Its frequency is therefore likely to be underestimated. The increasing use of implanted or wearable electronic devices with recording of the heart rhythm will possibly increase the number of cases, since previously unnoticed atrial fibrillation attacks are suddenly recorded.

Video: what is atrial fibrillation?

How dangerous is atrial fibrillation?

Unlike ventricular fibrillation, atrial fibrillation is not itself life threatening. Nevertheless, atrial fibrillation also harbors serious dangers: there is a risk of complications from blood clots (so-called thromboembolic complications), especially a stroke and cardiac insufficiency.

About 20 percent of all strokes are due to atrial fibrillation. The risk of stroke depends on age and concomitant diseases. Without anti-coagulant drugs, people over the age of 70 are expected to have a stroke risk of 20 to 30 percent within five years.

Younger people with atrial fibrillation are less likely to have a stroke (around one percent per year) if they have no heart disease or concomitant diseases. Whether a therapy with anticoagulants (anticoagulation) is necessary should always be decided on a case-by-case basis according to the so-called CHAD2DS2-VASc score.

© W & B / Jörg Neisel

What happens with atrial fibrillation in the heart?

Normally, the ventricles work perfectly in a team: First, the two atria contract, and blood flows into the two ventricles. Well-timed, the chambers then contract and pump blood into the circulation.

This smooth process is coordinated by specialized heart cells. They transmit electrical signals to the heart chambers in a set order so that they work together optimally. This mechanism is called excitation formation and conduction.

Stimulus conduction in the healthy heart

The graph above shows the normal course of electrical excitation in the heart.

A specialized cell structure on the roof of the right atrium, the sinus node, generates electrical impulses at regular intervals. They first activate the muscles of the atria. Shortly afterwards, they reach the heart chambers via the so-called AV node and a special line system and trigger a contraction there.

Disturbed stimulation

With atrial fibrillation, this process gets mixed up. Numerous electrical signals generated outside the sinus node "circle" in the atria.

As a result of the uncoordinated excitation of the atrial muscles, there is no longer any effective atrial contraction. The movement of the atria is more like "twitching" - they flicker and can no longer effectively support the ventricles in their pumping work.

The AV node is comparable to a filter station: it only allows part of the chaotic electrical signals from the atria to reach the ventricles - fortunately. Otherwise they would also flicker. And that would be life-threatening.

However, the AV node often lets a large number of electrical impulses "through". Then the chambers pump quickly and irregularly - often noticeable as a palpitation of the heart, palpitations or a racing heart.

At first, atrial fibrillation often occurs like a seizure and can end spontaneously after a short time. One then speaks of paroxysmal (attack-like) atrial fibrillation.

Consequences of atrial fibrillation

The atria can no longer support the ventricles in their pumping work. In the niches of the atrial muscles (for example in the so-called atrial appendage of the left atrium) blood can more or less remain and thus tend to form clots (thrombus formation). Such a clot (a thrombus) in the left atrium can loosen and be washed away into the left ventricle and from there into the body's large circulation. There, the clot can clog an organ artery, causing a stroke or circulatory disorder in another organ. If atrial fibrillation has persisted for a long time, the atria enlarge, their tissue structure and the electrical properties of the muscle cells change.

Anyone who feels that their heart is beating unusually fast or irregularly should always consult a doctor to be on the safe side. Complaints such as shortness of breath, dizziness or poor performance should also be clarified.

Symptoms of atrial fibrillation

Depending on the extent of the cardiac arrhythmia, the symptoms range from barely perceptible complaints to massive disorders of wellbeing. Unperceived (asymptomatic) atrial fibrillation may remain untreated for a long time and thus carries a risk of stroke.

How clearly patients feel symptoms is closely related to the pulse rate: the faster the heart beats, the more likely those affected are to perceive symptoms. The pulse rate, in turn, depends on how many of the very fast atrial impulses reach the ventricles. The AV node plays a decisive role here: it lies between the atria and the ventricles and has a kind of filter or braking function. It intercepts the rapid atrial impulses (they are between 300 and 600 per minute) and only allows part of them to reach the ventricles. Depending on the impulse line in the AV node, the heart rate can be up to 160 beats per minute or just 50 to 70 beats per minute.

Because effective atrial contractions no longer take place, the amount of blood that the chambers transport into the blood vessels per heartbeat is reduced. At rest, this amount of blood is reduced by up to 15 percent. The reduced delivery rate is even more noticeable during physical exertion. Those affected complain of strong palpitations or rapid heartbeat and, above all, of shortness of breath.

Symptoms of paroxysmal atrial fibrillation

Seizure-like atrial fibrillation - paroxysmal atrial fibrillation - usually only lasts for a short time. It is either not noticed at all or is described as a very unpleasant "palpitations" and palpitations. Patients may also cite a sudden feeling of weakness (mainly caused by a drop in blood pressure), shortness of breath, heart pain and a feeling of anxiety as further symptoms. These sufferers are able to indicate the sudden onset and end of the arrhythmia very precisely.

What causes atrial fibrillation?

Atrial fibrillation can have different causes. The following are some of the most common known causes of atrial fibrillation:

  • high blood pressure
  • old age
  • coronary heart disease
  • Valvular heart disease
  • Heart muscle disorders, such as inflammation of the heart muscle
  • Heart failure
  • Hyperthyroidism
  • excessive consumption of alcohol

© W & B / Jörg Neisel

Diagnosis: recognize atrial fibrillation

Around 75 percent of patients experience atrial fibrillation symptoms - for example, a particularly irregular, fast heartbeat or persistent palpitations. Such symptoms cause the doctor to feel the pulse and listen to the heart. An EKG (electrocardiogram) can sometimes immediately clarify whether the arrhythmia is caused by atrial fibrillation or another irregularity in the heart rhythm. However, atrial fibrillation often occurs only temporarily (paroxysmal or paroxysmal) in the initial phase of the disease - and therefore not always exactly when the doctor is currently writing an EKG in the doctor's office. The examination often shows a normal EKG. In this case, the doctor will try to record episodes of atrial fibrillation with a long-term EKG over 24 to 48 hours. To do this, the patient takes a small portable device home and wears it for a day or two. The data is then evaluated in practice.