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Friday, April 1, 2011

Asymptomatic Atrial Fibrillation

A 56-year-old man is evaluated in the office during a routine physical examination. He has no cardiovascular complaints. His medical history is unremarkable.

On physical examination, heart rate is approximately 90/min and irregularly irregular, and blood pressure is 130/78 mm Hg. Except for the abnormal cardiac rhythm, the remainder of the examination is unremarkable.

The electrocardiogram demonstrates atrial fibrillation with a heart rate of 92/min. The chest radiograph is unremarkable. Laboratory test results, including assessment of thyroid function, are normal. The patient is not aware of the abnormal rhythm or its duration.

In addition to heart rate control, which of the following would be most appropriate for this patient?
A Aspirin
B Clopidogrel
C Direct-current cardioversion
D Warfarin

Key Point
Aspirin is sufficient thromboembolic risk protection in patients with asymptomatic atrial fibrillation and no risk factors for stroke.

Answer and Critique (Correct Answer = A)

This patient with asymptomatic atrial fibrillation has no risk factors for stroke; therefore, aspirin would be sufficient thromboembolic risk protection. The CHADS2 score is used to assess stroke risk in patients with atrial fibrillation. The CHADS2 score assigns 1 point each for the presence of congestive heart failure, hypertension, age 75 years or older, and diabetes mellitus and 2 points for a history of stroke or transient ischemic attack. This patient's CHADS2 score is 0; therefore, risk of stroke is low and anticoagulation other than aspirin is not necessary.

Cardioversion is recommended primarily for patients with symptoms related to atrial fibrillation or patients with hemodynamic deterioration due to the loss of sinus rhythm. There are no data to suggest that conversion to sinus rhythm improves survival; cardioversion is therefore not indicated in this patient. If the patient's symptoms progressed to a point at which cardioversion would be indicated, anticoagulation with warfarin would be required first because of the potential of having an atrial clot that could embolize upon the restoration of sinus rhythm. Clopidogrel has not been demonstrated to be effective thromboprophylaxis for patients with atrial fibrillation. The combination of clopidogrel and aspirin has been shown to worsen outcomes in patients with atrial fibrillation by increasing the risk of bleeding.

1. Go AS, Fang MC, Singer DE. Antithrombotic therapy for stroke prevention in atrial fibrillation. Prog Cardiovasc Dis. 2005;48:108-24. [PMID: 16253651]

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