Atrial fibrillation

Atrial fibrillation is a common complication of high blood pressure .

Atrial fibrillation is a type of irregular heartbeat caused by a disturbance in the heart's electrical conduction.

 Normally an electrical impulse starts in the right atrium more precisely in the sinus node located there and is transmitted through the heart's conduction system to the ventricles. There it makes the muscle contract. The heart pumps and a heartbeat occurs.

In atrial fibrillation, however, self-sustaining electrical impulses circle around in the atria and are only partly passed on to the ventricles. This causes an irregular heartbeat that is often too fast. In some cases the heartbeat can also be slow if the electrical signal is not passed to the ventricles because of a so-called "conduction block".

Because of the circulating impulses in the atrium, it cannot fill properly with blood and therefore cannot pump the required amount into the ventricles. This reduces the heart's pumping ability because less blood is ejected into the body.

When high blood pressure is present, the conduction disorder usually occurs because the heart enlarges and undergoes fibrotic (scar) changes. As a result, electrical impulses cannot always be transmitted properly and circulating impulses occur. Atrial fibrillation, in turn, promotes the progression of these changes.

In atrial fibrillation the blood flow speed in the atria is reduced. Especially in the socalled atrial appendages (small pouches inside the atria) the blood then flows very slowly. Blood clots can form there, which can be carried by the bloodstream to the brain, for example, and cause a stroke.

Typical symptoms are a racing heart (palpitations), chest pain and shortness of breath when the heart is beating too fast. At a normal rate you may only notice weakness and tiredness or a general drop in performance. If the heart rate slows down because of a conduction block, dizziness and fainting are also possible.

If atrial fibrillation becomes chronic, it is also possible not to notice it at all the body more or less gets used to it.

Treatment and medical follow-up are important, even though atrial fibrillation especially at the beginning usually goes away on its own within 48 hours at the latest.

If left untreated, however, it can recur more often and eventually become persistent. Treatment usually starts with medication; some drugs used to treat high blood pressure also have antiarrhythmic effects. In some cases restoring a normal rhythm is attempted by cardioversion. For this the doctor gives an external electric shock to the heart under short general anesthesia, which often restores a normal rhythm. In severe cases of heart rhythm disorders a pacemaker is implanted.
A more modern treatment option is catheter ablation, a small surgical procedure. Using a catheter, usually threaded from a vein in the groin into the right atrium, the disturbed conduction pathway is destroyed by heat or cold. This treatment is considered very successful for newly occurring or paroxysmal atrial fibrillation. If atrial fibrillation has been present for longer, the success rate is somewhat lower.

The heart is a unique organ. It is the only muscle able to stimulate itself, in a synchronized, regular way and adapted to demand. For this there is the socalled conduction system in the heart. The sinus node mentioned above is located in the right atrium. It is the body's natural pacemaker. It generates the electrical impulses and passes them on to the other stations in the heart. Specialized heart muscle cells pick up these impulses and conduct them through both atria. The next station is the AV node (atrioventricular node), which lies between the right atrium and the right ventricle. It delays the impulse slightly so that the atria contract and push blood into the ventricles. From the AV node the impulse is passed on to the His bundle, from which the two bundle branches (Tawara branches) conduct the impulse to the Purkinje fibers. This ensures that all regions of the heart are reached.

A major feature of the conduction system is that the downstream station can generate an impulse if the predecessor fails. If the sinus node does not send signals, the AV node can generate impulses itself but at a slower rhythm. If the AV node also stops sending impulses, the His bundle, bundle branches and Purkinje fibers can still stimulate the heart so that it can beat at a very slow rate.

• http://www.netdoktor.de/krankheiten/herzrhythmusstoerungen/vorhofflimmern/
• https://www.kompetenznetz-vorhofflimmern.de/de
• https://herzstiftung.de/service-und-aktuelles/presse/pressemitteilungen/vorhofflimmern-katheter-ablation
  

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