cardiovascular disorders
Atrial Fibrillation
Introduction
Atrial fibrillation is a rapid, irregularly irregular atrial rhythm. Symptoms include palpitations and sometimes weakness, effort intolerance, dyspnea, and presyncope. Atrial thrombi may form, causing a significant risk of embolic stroke. Diagnosis is by electrocardiography. Treatment involves rate control with drugs, prevention of thromboembolism with anticoagulation, and sometimes conversion to sinus rhythm by drugs or cardioversion. (See also Overview of Arrhythmias .) Atrial fibrillation has been attributed to multiple wavelets with chaotic reentry within the atria. However, in many cases, firing of an ectopic focus within venous structuresadjacentto the atria (usually the pulmonary veins) is responsible for initiation and perhaps maintenance of atrial fibrillation. In atrial fibrillation, the atria do not contract, and the atrioventricular (AV) conduction system is bombarded with many electrical stimuli, causing inconsistent impulse transmission and an irregularly irregular ventricular rate, which is usually in the tachycardia rate range. Atrial fibrillation is one of the most common arrhythmias, affecting between 3 and 6 million adults in the US. Men and White people are more likely to have atrial fibrillation than women and Black people. Prevalence increases with age; almost 10% of people>80 years are affected. Atrial fibrillation tends to occur in patients with an underlying heart disorder. 