What Is Atrial Fibrillation?
Atrial fibrillation, or AF, is the most common heart rhythm disorder. It is estimated that between 1.5 and 2 percent of the population of industrialized countries suffer from atrial fibrillation. As the risk of suffering from atrial fibrillation increases with the age, aging societies can expect an increase in the morbidity rate among their populations.1 Atrial fibrillation is characterized by an irregular heartbeat. In the beginning, the irregular pulse often appears paroxysmal, meaning it causes sudden attacks. These can last for minutes, hours or even days until the heart rhythm spontaneously normalizes. Over time, these attacks may develop into chronic atrial fibrillation, which requires medical treatment as they no longer end spontaneously. Patients usually get used to the irregular pulse, which causes atrial fibrillation to go unnoticed in some cases. This can have potentially fatal consequences, as atrial fibrillation increases the risk of stroke. In order to prevent a stroke, it is therefore essential to detect even asymptomatic phases of atrial fibrillation. Patients with silent episodes of atrial fibrillation require a special drug therapy for stroke prevention.
In atrial fibrillation, the muscles of the atria no longer contract rhythmically and in sync with one another. This means that too little blood reaches the heart chambers and the heart’s ability to pump blood declines in general. There is also a chance that in certain areas of the atria, particularly the cardiac auricles, blood can stagnate, consequently leading to blood clots. These blood clots can float off and cause a stroke if they clog a blood vessel in the brain. Atrial fibrillation can lead to a racing heart (tachycardia), an irregular heartbeat and, in some circumstances, a slow heart rate (bradycardia).
In contrast to ventricular fibrillation, atrial fibrillation is usually not life-threatening. One must not, however, underestimate the elevated risk of stroke. You should therefore immediately go for examination by a physician if you have the feeling something is wrong.
Paroxysmal atrial fibrillation, which occurs suddenly and disappears without treatment, often goes unnoticed. In other cases, the irregular pulse causes symptoms such as heart palpitations, tachycardia, chest pain, dizziness and restlessness. If the heart’s pumping capacity is significantly reduced, shortness of breath and general debility may occur as a result of atrial fibrillation. In some cases atrial fibrillation may also trigger anxiety.
It is important that even asymptomatic atrial fibrillation be detected in time. Without treatment, paroxysmal attacks may become occur more and more frequently and can increase the risk of a stroke. At-risk patients should therefore be examined on a regular basis.
One of the major risk factors for atrial fibrillation is age. Pre-existing conditions of the cardiovascular system also increase the risk of atrial fibrillation:
- High blood pressure
- Heart failure
- Cardiac enlargement (dilatation)
- Valvular heart disease: mitral valve stenosis, valvular aortic stenosis
Moreover, diseases such as hyperthyroidism or diabetes mellitus as well as excessive alcohol consumption and electrolyte shifts influence the development of atrial fibrillation.
The easiest way to detect atrial fibrillation is to check your pulse. If your pulse is irregular, there is a high likelihood you have atrial fibrillation. With the help of an electrocardiogram or ECG suspected chronic atrial fibrillation can quickly be confirmed.
Cases of paroxysmal atrial fibrillation, however, are far more difficult to verify, as the ECG has to be performed during an attack in order to detect it. For those with paroxysmal atrial fibrillation, therefore, an examination at the doctor’s office may not lead to any conclusive diagnosis. In that case a long-term ECG is performed; this measures heart activity for 24 hours or longer. If the result is still ambiguous, a heart monitor may be implanted to achieve the correct diagnosis. The implantable monitor is placed under the skin over the left breast muscle of the patient and can monitor the patient’s heart rhythm for several years.
Moreover, an exercise ECG should establish how the heart responds to exertion. Further examinations such as cardiac ultrasound and blood tests may also be used to detect causes or comorbidities of atrial fibrillation.
The aim of treating atrial fibrillation is to restore the normal heart rhythm, to regulate heart rate and to minimize the risk of a stroke. The heart rhythm can be restored by antiarrhythmic medication or electric cardioversion.
After cardioversion, antiarrhythmic medication is used to prevent the recurrence of atrial fibrillation. It is also used for rate control therapy. If the antiarrhythmic medication cannot permanently normalize the heart rhythm, catheter ablation, in which the cells responsible for abnormal heart rhythm are treated, will be considered. Paroxysmal atrial fibrillation often does not require treatment as it resolves spontaneously.
Electrical cardioversion enables a kind of reset of cardiac activity via a targeted dose of electric current, following which the heart is once more able to be beat in its normal heart rhythm. Cardioversion is performed under anesthesia. During and after an electrical cardioversion, there is a high risk of blood clotting inside the heart. To prevent blood clots from forming, patients receive anticoagulant medication.
Blood clots, which had already developed due to atrial fibrillation, may break free during cardioversion, float into an artery of the brain and lead to stroke. If a physician suspects there are blood clots inside the heart, they will perform a transesophageal echocardiogram (TEE) before the cardioversion. In this procedure the physician introduces a small ultrasound device into the esophagus and navigates it close to the heart. If the physician does not find any blood clots, he may carry out the cardioversion on the spot. If blood clots are detected, however, the cardioversion has to be delayed while the patient is given drugs to resolve the existing clots and to prevent the development of new ones.
The aim of catheter ablation, also known as radiofrequency ablation, is to isolate the areas of the heart causing atrial fibrillation from the rest of the heart. Usually these cells are in the heart’s left atrium around the lung veins. To get there, the physician introduces a thin flexible tube into a large blood vessel in the groin and guides it carefully into the left atrium. There he or she destroys the "bad tissue” with heat (radiofrequency energy) or extreme cold (kryoablation). The resulting scarification isolates the affected area from the healthy area of the heart. After the procedure, the patient receives anticoagulant medication, to prevent the formation of blood clots. The heart’s activity ismeasured regularly after the ablation in order to assess whether the procedure was successful; if necessary, it will be repeated.
First of all, it is important to adhere to your physician’s prescriptions and recommendations. If you are in doubt as to whether the prescribed medication and/or procedures as well as recommendations regarding your life-style are good for you, talk with your physician or ask another physician for a second opinion.
In addition, you should reduce risk factors by living healthily, eating a light and balanced diet, drinking only small amounts of alcohol and exercising often, but not too strenuously.
1 Camm AJ et al. 2012 focused update of the ESC Guidelines for the management of atrial fibrillation. European Heart Journal Nov 2012, 33 (21) 2719-2747; DOI: 10.1093/eurheartj/ehs253