美国医师执照考试丛书：急诊医学（第2版）_（美），罗士，（AdamJ.Rosh）著_9787811168587

　　Emergency Medicine：PreTest Self-Assessment and Review，Second Edition，is intended to provide medical students，as well as house officers and physicians，with a convenient tool for assessing and improving their knowledge of emergency medicine.The 500 questions in this book are similar in format and complexity to those included in Step 2 of the United States Medical Licensing Examination （USMLE）.They may also be a useful study tool for Step 3 and clerkship examinations.

　　3. The answer is e. （Rosen, pp 1083-1085.） Atrial fibrillation （AF） is a rhythm disturbance of the atria that results in irregular, chaotic, ventricular waveforms. This chaotic activity can lead to reduced cardiac output from a loss of coordinated atrial contractions and a rapid ventricular rate, both of which may limit diastolic filling and stroke volume of the ventricles. Atrial fibrillation may be chronic or paroxysmal, lasting minutes to days. On the ECG, fibrillatory waves are seen and accompanied by an irregular QRS pat- tern. The main ED treatment for atrial fibrillation is rate control. This can be accomplished by many agents, but the agent most commonly used is diltiazem, a CCB with excellent AV nodal blocking effects.
　　（a） If the patient was unstable, he should be immediately cardioverted. However, this patient is stable and asymptomatic; therefore, the goal in the ED is rate control. （b） Catheterization would be correct if the patient exhibited ST-segment elevations on the ECG. （c） If the patient is in atrial fibrillation for greater than 48 hours, then he needs to be anticoagulated prior to cardioversion. Coumadin, along with heparin, are agents used for anticoagulation. In general, a patient with stable atrial fibrillation under- goes an echocardiogram to evaluate for thrombus. If there is a thrombus present, patients are placed on Coumadin for 2 to 3 weeks and cardioversion takes place when their international normalized ratio （INR） is therapeutic. If no clot is seen on echocardiogram, then heparin is administered and cardioversion can take place immediately （d） Amiodarone is also used for rate control in atrial fibrillation; however, it is not a first-line agent and is recommended to be used selectively in patients with a low left ventricular ejection fraction.

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