Abbreviation: AF.
The most common cardiac dysrhythmia, affecting as many as 5 – 10% of people age 70 and over. It is marked by rapid, irregular electrical activity in the atria, resulting in ineffective ejection of blood into the ventricles and an irregular ventricular response (apical pulse rate). Blood that eddies in the atria may occasionally form clots that may embolize (esp. to the brain, but also to other organs). As a result AF is an important risk factor for stroke. In the U.S., about 75,000 strokes occur each year in patients with AF. AF may also contribute to other diseases and conditions, including congestive heart failure, dyspnea on exertion, and syncope.

ETIOLOGY
AF may occur in otherwise healthy persons with no structural heart disease (lone AF) (e.g., during stress or exercise). It may also develop secondary to alcohol withdrawal; in patients with underlying arrhythmias (such as tachybrady syndrome or Wolff-Parkinson-White syndrome); after cardiac surgery; during cocaine intoxication; in hypertensive urgencies, hypoxia, or hypercarbia (carbon dioxide retention); during myocardial infarction; in pericarditis and pulmonary embolism; or as a consequence of congestive heart failure, COPD, sepsis, or thyrotoxicosis or other metabolic disorders. Chronic AF, also known as persistent, permanent, or sustained AF, usually occurs in patients with structural abnormalities of the heart, such as cardiomyopathies; enlargement of the left atrium; mitral valve disease; or rheumatic heart disease. Paroxysmal AF is AF that occurs intermittently and resolves spontaneously. Recurrent AF is a term used to describe two or more episodes of AF occurring in the same person.

SYMPTOMS
Some patients may not notice rapid or irregular beating of their heart, even though the ventricular rate rises to 200 bpm. Most patients, however, report some of the following symptoms at slower heart rates (100 bpm or greater): dizziness, dyspnea, palpitations, presyncope, or syncope.

DIAGNOSIS
Patients who present with their first episode of atrial fibrillation are typically evaluated with thyroid function tests, cardiac enzymes, a complete blood count, and blood chemistries. In patients with a cardiac murmur or evidence of congestive heart failure, echocardiography is typically performed.

TREATMENT
The acutely ill (unstable) patient with a rapid ventricular response (>150/m) and signs or symptoms of angina pectoris, congestive heart failure, hypotension, or hypoxia should be prepared for immediate cardioversion. Patients who are stable and tolerate the rhythm disturbance without these signs or symptoms are typically treated first with drugs to slow the heart rhythm (e.g., calcium-channel blockers, beta blockers, or digoxin). For most patients with atrial fibrillation with a rapid ventricular response, controlling the rapid heart rate alleviates symptoms. Electrical or chemical cardioversion of initial episodes of atrial fibrillation may successfully restore sinus rhythm, often for a period of several months to as long as a year but does not affect morbidity or mortality. Anticoagulation (e.g., with warfarin) markedly reduces the risk of stroke and should be given for several weeks before, and about a week after, elective cardioversion, and to patients in chronic AF who do not return to sinus rhythm with treatment. Patients who elect not to use anticoagulants for chronic AF, or in whom anticoagulants pose too great a risk of bleeding, usually are given 325 mg of aspirin daily. AF can also be treated with radiofrequency catheter ablation, or with surgical techniques to isolate the source of the rhythm disturbance in the atria or pulmonary veins.
See: ablation

PATIENT CARE
The acutely ill patient is placed on bedrest and monitored closely, with frequent assessments of vital signs, oxygen saturation, heart rate and rhythm, and 12-lead electrocardiography. Supplemental oxygen is supplied and intravenous access established. Preparations for cardioversion (if necessary) and the medications prescribed for the patient are explained. Patients should be carefully introduced to the risks, benefits, and alternatives to stroke prevention with anticoagulation. Stroke is one of the most serious complications for patients with atrial fibrillation. The risk of embolic stroke in AF is about 5% annually without anticoagulation but lower with it. However, the use of anticoagulants increases the risk of bleeding. Patients treated with anticoagulants should maintain an International Normalized Ratio (INR) in the 2.0 to 3.0 range. Regular assessment of the INR reduces the hazard of serious bleeding.

Main entry:
fibrillation