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Heart Disease: Atrial Fibrillation (and Atrial Flutter)

Atrial fibrillation is the most common sustained cardiac arrhythmia

Atrial fibrillation (AF) is a powerful risk factor for ischemic stroke, independently increasing risk about  5 times, regardless of age. It is also an independent risk factor for stroke severity, recurrence, and mortality. AF is the most common cardiac dysrhythmia. Estimates of its prevalence in the U.S. ranged from about 2.7 to 6.1 million in 2010. Being white and older both increase the risk of AF.

Special populations

The percentage of stroke attributable to atrial fibrillation increases from 1.5% at 50-59 years of age to 23.5% in Seniors aged 80-89. (NOTE: These numbers may be significant underestimates, as atrial fibrillation is often asymptomatic and may not be detected clinically.)

Relationship to stroke pathogenesis

Patients with atrial fibrillation have a greatly increased risk of embolic strokes. Ineffective contraction of the atrium allows blood to pool along its walls encouraging thrombus formation. Bits of these thrombi can travel through the left ventricle, enter the systemic circulation and embolize the brain.

A little about control/treatment

In some patients, atrial fibrillation resolves spontaneously. Cardioversion, ablation, or drug therapy may be used to restore a normal cardiac rhythm.  However none of these approaches has been shown to reduce short-term stroke risk. By contrast, in patients with chronic nonvalvular atrial fibrillation, anticoagulation with warfarin significantly reduces stroke risk compared with untreated patients, but it requires monitoring. For patients who have a low overall stroke risk or for whom warfarin therapy is not an option, an antiplatelet agent like aspirin or clopidogrel may be considered. Newer anticoagulants that do not require monitoring are now available (e.g. dabagatran or apixaban) and may replace warfarin in some cases. Clinical decisions about use of these therapies must consider the risk of hemorrhagic complications.