Atrial fibrillation belongs to diseases characterized by a disturbed cardiac rhythm (irregular heartbeat).
In atrial fibrillation, electric signals do not travel their usual ways but they rather spread chaotically in all directions. The culprit of these abnormal electrical impulses is a damaged cardiac electrical conduction system. Atrial fibrillation also causes blood clots in the heart which can cause a stroke. It can be diagnosed with an electrocardiograph (EKG) or Holter monitor (24-hour EKG recording), in case fibrillation occurs in attacks.
How is atrial fibrillation prevented or treated?
The aim is to normalize the heart rhythm with medications or electrical stimulation, and to prevent abnormal blood clotting.
More detailed description about atrial fibrillation
Atrial fibrillation is one of the most common arrhythmias (i.e. abnormal heart rhythm). It affects about 0.5% of the population in Europe and the USA. Its incidence characteristically increases with advancing age. The disease is represented in all races and both sexes equally.
During a normal heartbeat, the electrical impulses travel from the sinus node, which is a natural pacemaker, through the conduction fibres to the atrio-ventricular node and further to the ventricular conduction system. In the case of atrial fibrillation, the electrical impulses do not travel their natural path but rather chaotically spread in all directions. Fibrillation of the heart muscle appears as a result of these irregular electrical impulses. An irregular and fast heart rate results, the atrial rate reaching up to 175 beats per minute (normal rate is up to 100 beats per minute).
Causes and symptoms
The cause for the appearance of abnormal electrical impulses is most often the abnormal structure of the conduction system or an injured heart muscle. This is characteristic for disease states such as hypertension, myocardial infarction (heart attack), valvular heart disease, congenital heart disease, metabolic disorders (e.g. thyroid disease or hyperthyroidism), exposure to alcohol and drugs, infections and the post-operative states (heart surgery).
Signs and symptoms of the disease are the result of irregular heart rhythms. The heart is able to pump a smaller volume of blood than usual and hypotension (too low a blood pressure) may result. In addition to hypotension, symptoms such as palpitations (the sensation of irregular, rapid heart rate), weakness, shortness of breath, confusion and chest pain appear.
The appearance of atrial fibrillation can herald heart failure because the malfunctioning heart cannot provide enough blood volume to support normal functioning of the body. The other great danger of atrial fibrillation is the increased risk of stroke. Due to irregular atrial activity, blood no longer flows smoothly but rather starts to accumulate and clot. Blood clots form and may travel the circulation and block vessels in other body organs. The most dangerous consequences appear when such blood clots find their way to the brain vessels, resulting in a stroke.
A physician suspects the disease based on characteristic symptoms in patient history. In addition to taking a history, a quality physical exam is a prerequisite for a timely and precise diagnosis. The disease can be confirmed with an ECG (electrocardiograph) as well as Holter monitoring (i.e. 24-hour recording of the heart rhythm), a cardiac ultrasound (Echo) and blood work.
For atrial fibrillation prevention, it is important to treat diseases which contribute to the appearance of atrial fibrillation in addition to the genes. That primarily includes other heart diseases (heart failure, valvular heart disease) as well as hypertension. In addition to pharmacotherapy, a healthy lifestyle with regular physical activity, maintenance of a normal body weight and a healthy diet help prevent atrial fibrillation in the case of the presence of the aforementioned co-morbidities.
Alcohol and caffeine abuse as well as illicit drugs such as cocaine may lead to atrial fibrillation. Hyperthyroidism must also be ruled out.
There are two basic goals of therapy:
Establishment of a normal heart rhythm and heart rate control;
Prevention of blood clots appearing from the chaotic atrial contractions lead to a blood stasis in the heart. The stasis facilitates blood clotting; the formed clots may exit the heart and block the vessels in other organs, most often in the brain.
Therapy is tailored according to each individual's needs. It depends on the severity of symptoms such as dyspnoea, light-headedness, fatigue as well as chest pain and palpitations. It is important to treat the other diseases that may have led to atrial fibrillation, such as heart disease and thyroid dysfunction. The duration of symptoms plays an important role as well, which can be constant or intermittent.
Physicians use cardioversion to re-establish a normal cardiac rhythm. Cardioversion is used to make the chaotically-contracting atria assume the normal sinus rhythm.
It may be achieved with:
Medications (anti-arrhythmic agents), that are later on used for the maintenance of a normal heart rhythm.
Electrical shock that briefly arrests the heart with the hope that the heart will assume a normal rhythm. This procedure is carried out under anaesthesia.
At times, however, the conversion of the arrhythmic heart rhythm to the sinus rhythm is unsuccessful. In such cases, the goal of the therapy becomes the maintenance of the heart rate between 60 and 100 bpm, since an increased frequency that marks atrial fibrillation is harmful to the heart in the long run. This can be achieved by the use of various medications such as the beta blockers, digoxin and calcium channel blockers.
If pharmacotherapy does not attain the desired results, i.e. the heart rate control and the establishment of normal cardiac rhythm, the physician may suggest two further procedures:
Catheter ablation or destruction of the atrial tissue that is responsible for the chaotic atrial contractions in people with otherwise healthy hearts. This is achieved with the use of radio frequencies.
The destruction of the AV (i.e. atrioventricular) node which normally conducts electrical impulses from the atria to the ventricles. In this way, the conduction of the fast impulses which are responsible for the increased heart rate is blocked. This is followed by an implantation of a cardiac pacemaker that ensures the maintenance of a normal heart rate.