Atrial fibrillation is a common arrhythmia (abnormal heart rhythm). More than 2 million Americans have this abnormal heart rhythm. Although not uncommon in people in their 50’s atrial fibrillation becomes increasingly common with advancing age. During normal rhythm, the heart’s intrinsic pacemaker (or sino-atrial node) produces an electrical impulse that travels through specialized conducting tissue throughout the atria (the upper chambers), stimulating the atrial myocardium or heart muscle to contract, pumping blood from the atria into the ventricles. The electrical signal also spreads through connecting pathway between the atria and ventricles (the lower chambers) called the atrioventricular (AV) node. As the impulse passes through the AV node and spreads, the myocardium of the ventricles contract, pumping blood out of the heart. Each contraction results in a heartbeat. During atrial fibrillation, the generation and the spread of electrical impulses in the atria are chaotic. As a result, the atrial myocardium contracts ineffectively (fibrillate). The AV node is bombarded by electrical signals not all of which are transmitted to the ventricles. This results in an irregular and often rapid heart rate. The loss of atrial contraction, the rapid rates and irregular rhythm cause the heart to beat less efficiently. Atrial fibrillation can be caused by changes that occur as the heart ages. However it often occurs as a result of structural heart disease from coronary artery disease, myocardial infarction, valvular heart disease, hypertension, cardiomyopathies etc. It can also develop as a complication of emphysema or other lung diseases; exposure to stimulants such as cocaine, caffeine or tobacco; intake of alcohol or from metabolic abnormalities such as an overactive thyroid.Atrial fibrillation may be classified as recurrent (2 or more identified episodes of atrial fibrillation), paroxysmal (episodes terminates spontaneously within 7 days, often within 24 hours), persistent (atrial fibrillation is present for more than seven days) or chronic (i.e., the arrhythmia has been persistently present).
Abraham Salacata, MD, FACC