Atrial Fibrillation

Atrial fibrillation is an abnormal heart rhythm which involves the two small, upper heart chambers. Heart beats in a normal heart begin after electricity generated in the atria by the sinoatrial node spreads through the heart and causes contraction of the heart muscle and pumping of blood. In AF, the regular electrical impulses of the sinoatrial node are replaced by disorganized, rapid electrical impulses which result in irregular heart beats.

Atrial fibrillation is the most common cardiac arrhythmia. The risk of developing atrial fibrillation increases with age — AF affects four percent of individuals in their 80s. An individual may spontaneously alternate between AF and a normal rhythm or may continue with AF as the dominant cardiac rhythm without reversion to the normal rhythm. This variety of disorder is sometimes associated with the secretion of adrenalin under conditions of emotional stress in this age group.

Atrial fibrillation is often asymptomatic, but may result in symptoms of palpitations, fainting, chest pain, or even heart failure. These symptoms are especially common when atrial fibrillation results in a heart rate which is either too fast or too slow. In addition, the erratic motion of the atria leads to blood stagnation which increases the risk of blood clots that may travel from the heart to the brain and other areas. Thus, AF is an important risk factor for stroke, the most feared complication of atrial fibrillation.

The symptoms of atrial fibrillation may be treated with medications which slow the heart rate. Several medications as well as electrical cardioversion may be used to convert AF to a normal heart rhythm. Surgical and catheter-based therapies may also be used to prevent atrial fibrillation in certain individuals. People with AF are often given blood thinners such as warfarin to protect them from strokes.

Atrial fibrillation is usually accompanied by symptoms related to either the rapid heart rate or embolization. Rapid and irregular heart rates may be perceived as palpitations, exercise intolerance, and occasionally produce angina and congestive symptoms of shortness of breath or edema. Sometimes the arrhythmia will be identified with the onset of a stroke or a transient ischemic attack (TIA). It is not uncommon to identify atrial fibrillation on a routine physical examination or electrocardiogram (ECG/EKG), as it may be asymptomatic in some cases.

The main goals of treatment of atrial fibrillation are to prevent temporary circulatory instability and to prevent stroke. Rate and rhythm control are principally used to achieve the former, while anticoagulation may be required to decrease the risk of the latter. The primary factors determining atrial fibrillation treatment are duration and evidence of hemodynamic instability. Cardioversion is indicated with new onset AF and with hemodynamic instability.

AF can cause disabling and annoying symptoms. Palpitations, angina, lassitude, and decreased exercise tolerance are related to rapid heart rate and inefficient cardiac output caused by AF. There are two ways to approach these symptoms: rate control and rhythm control. Rate control treatments seek to reduce the heart rate to normal, usually 60 to 100 beats per minute. Rhythm control seeks to restore the normal heart rhythm, called normal sinus rhythm. Studies suggest that rhythm control is mainly a concern in newly diagnosed AF, while rate control is more important in the chronic phase. Rate control with anticoagulation is as effective a treatment as rhythm control in long term mortality studies, the AFFIRM Trial.

AF with a persistent rapid rate can cause a form of heart failure called tachycardia induced cardiomyopathy. This can significantly increase mortality and morbidity. The early treatment of AF through either rate-control or rhythm-control can prevent this condition and thereby improve mortality and morbidity.

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Related Links:

• American Heart Association
• Mayo Clinic

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