All patients should have undergone an initial assessment (Fig. 19-2) on presentation to the emergency department (ED), including 12-lead ECG (to be done within 10 minutes after arrival to the ED), history, and physician exam. Patients should be considered for evaluation of acute coronary syndrome by obtaining a blood specimen for cardiac markers and also should be considered for evaluation for acute heart failure by obtaining a BNP (β-type natriutretic peptide) level if diagnosis is uncertain. If the BNP level exceeds 500 pg/mL, patients should be treated for acute heart failure. It has been shown in multiple clinical trials that the prevalence of AF increased relative to the New York Heart Association heart failure class (8). Acute coronary syndrome and acute heart failure should be treated respectively per published guidelines and pathways (9,10).

Additional initial laboratory tests should include a basic metabolic panel, complete blood count, magnesium level, thyroid function tests, and coagulation panel. All patients should have a chest x-ray.

All patients should be assessed for hemodynamic stability (Fig. 19-3) as defined by advanced cardiac life support (ACLS) guidelines (11). If patients are unstable, emergency synchronized D/C cardioversion should be performed.

We have developed a systematic approach to the pathophysiology of AF and Afl (Fig. 19-4) by using acronyms that can easily be remembered by physicians, nurses, and other health care personnel:

Timing the duration of atrial fibrillation and atrial flutter is sometimes difficult if the patient cannot pinpoint the starting time of their arrhythmia. It is well accepted that patients whose arrhythmia is less than 48 hours in duration can safely have a cardioversion performed (Fig. 19-5), and those with arrhythmia >48 hours may have developed atrial thrombus, which increases the risk of thromboembolic events postcardioversion.

Transthoracic electrical cardioversion is more successful than pharmacologic cardioversion, with an overall success rate of 75% to 93%, inversely related to the duration of AF, chest wall impedance, and left atrial size (12,13,14). The success rate for pharmacologic cardioversion in selected patients approaches 70% at best (15), and there is a risk of proarrhythmia. For this reason, we recommend electrical cardioversion.

There are two conventional positions for the electrode placement: anterior-lateral and anterio-posterior. Several studies have shown that less energy is required and a higher success rate is achieved with electrodes in the anteroposterior position (16,17). For this reason, we recommend the anteroposterior location. The energy required for cardioversion of AF is often >200 joules (18). More energy is required in obese patients and for long-standing AF. The initial energy used depends in part on the waveform of the current delivered by the defibrillation. Biphasic devices have been shown to be more effective and require less energy than monophasic devices (19).

When the onset of AF cannot be accurately determined or if AF is longer than 48 hours, anticoagulation should always be administered (Fig. 19-6).

The conventional approach was to recommend anticoagulation with a therapeutic international normalized ratio (INR) (2.0 to 3.0) for 3 weeks before and 4 weeks after cardioversion.

Anticoagulation prior to cardioversion can be shortened if transesophageal echo (TEE) is done and indicates the absence of thrombus in the left atrium or the left atrial appendage. The TEE guided approach has been evaluated in the Assessment of Cardioversion Utilizing Echocardiography (ACUTE) trial (20,21). With this approach, which we often employ, heparin is given immediately and concurrently with warfarin, and heparin is continued until the INR is therapeutic. Cardioversion is done immediately when the TEE suggests that there is no evidence of thrombus; warfarin is continued for at least 4 weeks depending on long-term risk.

Either intravenous unfractionated heparin or subcutaneous low-molecular-weight heparin may be used (22). Consideration of discontinuation of warfarin after 4 weeks can be made when there is no recurrence of AF and there are no stroke risk factors.

The nomenclature used to classify AF has been diverse (23). The published guidelines (4) suggest the classification of first detected, paroxysmal (self-terminating), persistent (not self-terminating), and permanent (Fig. 19-7).

In this regard we define permanent AF as continuous AF of longer than 7 days, with failed cardioversion or when a decision has been made not to attempt cardioversion. A patient with permanent AF will be managed with rate control and anticoagulation medication. Holter monitoring can be used to evaluate rate control. Patients whose rate control is unsuccessful should have an electrophysiology (EP) consult to consider atrioventricular (AV) nodal ablation and permanent pacemaker implantation.