3. In a patient with a narrow complex tachycardia of uncertain etiology, what effect will giving adenosine have if the rhythm is atrial fibrillation?

A. The rhythm will terminate, resulting in normal sinus rhythm in a majority of cases.

B. The rhythm will transiently slow down, revealing either no atrial activity or coarse fibrillatory waves before reverting back to the tachycardic state.

C. The rhythm will decrease in heart rate transiently in a person without Wolff-Parkinson-White syndrome.

D. Adenosine will have no effect on atrial fibrillation.