What causes atrial fibrillation?
Atrial fibrillation is associated with many cardiac conditions, including cardiomyopathy, coronary artery disease, valvular heart disease, ventricular hypertrophy and other associated conditions. Atrial fibrillation has been associated with hyperthyroidism, acute alcohol intoxication, changes in the autonomic nervous system and is common after cardiac surgery. The most common condition associated with atrial fibrillation is high blood pressure. Some people have atrial fibrillation
with no obvious source or associated condition. This is more frequent in younger people and it is called "lone" atrial fibrillation. It is likely that people who have this form of atrial fibrillation have had some inflammatory process or trauma to the atrium. Some people have a focal source that originates from the pulmonary veins.
Many conditions can cause disorganized electrical activity in the atria to develop. In many cases, a "leaky" or a sticky (stenotic) mitral valve can result in an enlarged (dilated) atria. Patients with a history of high blood pressure (hypertension), can develop atrial fibrillation, because high blood pressure eventually begins to affect the atria. Blockages in the arteries that supply the heart with blood (coronary arteries), heart attacks, and an overactive thyroid gland can also lead to atrial fibrillation. Excessive consumption of alcohol acts as a toxin on the heart, and patients who binge drink or chronically drink large amounts of alcohol are at risk for developing atrial fibrillation. Patients with heart failure, in which the left ventricle, the heart’s main pumping chamber, does not pump blood normally, may develop atrial fibrillation as blood "backs up" from the left ventricle into the left atrium. Rarely, a blood clot develops in the legs and travels to the lungs, causing a pulmonary embolus that can trigger atrial fibrillation. Pericarditis (inflammation of the tissue that surrounds the heart, the pericardium) can irritate the atria and lead to atrial fibrillation. In some patients, there simply is no clear cause for the condition.
In a heart that is beating normally, the rate of ventricular contraction is the same as the rate of atrial contraction. In AF, however, the rate of ventricular contraction is less than the rate of atrial contraction. The rate of ventricular contraction in AF is determined by the speed of transmission of the atrial electrical discharges through the AV node. In people with a normal AV node, the rate of ventricular contraction in untreated AF usually ranges from 80 to 180 beats/minute; the higher the transmission, the higher the heart rate.
Some older people have slow transmission through the AV node due to disease within the AV node. When these people develop AF, their heart rates remain normal or slower than normal. As disease in the AV node advances, these people can even develop an excessively slow heart rate and require a permanent pacemaker to increase the rate of ventricular contractions.
More information on atrial fibrillation
What is atrial fibrillation (AF)? - Atrial fibrillation (AF) is an electrical rhythm disturbance of the heart affecting the atria. Atrial fibrillation is the most common form of irregular heartbeat.
What causes atrial fibrillation? - Atrial fibrillation is associated with many cardiac conditions, including cardiomyopathy, coronary artery disease, valvular heart disease.
What're the symptoms of atrial fibrillation? - Symptoms of atrial fibrillation include palpitations, fainting, dizziness, weakness, shortness of breath and angina pectoris.
What're the complications of atrial fibrillation? - The most devastating complication of atrial fibrillation occurs when a blood clot forms in the left atrium and is pumped to the brain.
How is atrial fibrillation diagnosed? - The diagnosis of atrial fibrillation includes a medical history and physical examination, an electrocardiogram (ECG), and an echocardiogram.
What's the treatment for atrial fibrillation? - Treatment for atrial fibrillation depends on the underlying cause. A highly effective, safe treatment for atrial fibrillation is still an unmet medical need.