Thyroid, renal, and hepatic function tests, serum electrolytes, and hemograms may help to rule out reversible causes of AF. Chest x-ray is valuable in diagnosing CHF, as well as lung pathology. Recent guidelines recommend that all patients who present with AF undergo echocardiography to evaluate for valvular heart disease, left and right atrial size, left ventricular size and function, left ventricular hypertrophy, and pericardial disease.1 Transesophageal echocardiogram (TEE) should be used to detect intracardiac clots in patients who have had an embolic event or when AF has lasted for more than 48 hours and cardioversion is being considered.
Rate vs rhythm control: What the research reveals
For hemodynamically unstable patients who present with AF and a rapid rate associated with cardiogenic shock, pulmonary edema, acute myocardial infarction, or unstable angina, urgent direct-current cardioversion is indicated. In less urgent cases, treatment is not so clear cut. Spontaneous conversion to sinus rhythm occurs in up to 60% of patients within 24 hours, and in about 80% of patients within 48 hours.8
Intuitively, restoring normal sinus rhythm seems superior to rate control, but several randomized trials9-12 and one meta-analysis13 found no support for that belief when researchers looked at mortality, thromboembolic events, and major hemorrhage.
One of the largest studies was the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM), which involved more than 4000 patients with paroxysmal and persistent AF who were randomized to either rate control or rhythm control.9 The research revealed a nonsignificant trend toward an increased death rate with the rhythm-control strategy—a 5-year mortality rate of 24% vs 21% for patients in the rate-control group. A trend toward higher risk of ischemic stroke, particularly associated with the lack of anticoagulation therapy, was also found in the rhythm-control group. That finding emphasizes the need for indefinite anticoagulation, independent of the use of a rate-control or rhythm-control approach.
A retrospective subanalysis of the AFFIRM trial that evaluated patients on the basis of a number of independent treatment variables found that sinus rhythm, in and of itself, was actually associated with a lower risk of death. But the antiarrhythmic agents that are often needed to achieve sinus rhythm are not associated with higher rates of survival. According to the researchers, this finding suggests that the drugs’ beneficial antiarrhythmic effects are offset by their adverse effects.14
Age is another confounding factor. Most of the AFFIRM subjects were relatively older, with a mean age of 69.7 years. In another study, rhythm control was found to be beneficial in young patients (mean age of 38.6 years) with AF and rheumatic valvular heart disease, in terms of morbidity and mortality.15
With no single treatment strategy emerging as the best approach, guidelines offer help in determining whether to pursue a rate-control or rhythm-control strategy for a particular patient. The recommendations of the British National Institute for Health and Clinical Excellence (NICE) guideline for AF,16 developed on the basis of a systematic literature review as well as expert consensus, are summarized here.
When should you opt for rate control?
The NICE guideline recommends rate control as the initial choice for patients who have persistent AF and:
- are >65 years of age
- have coronary artery disease
- do not have CHF
- are not candidates for cardioversion
- have contraindications to antiarrhythmic drugs.16
The American College of Cardiology (ACC), American Heart Association (AHA), and European Society of Cardiology (ESC) guidelines recommend maintaining a ventricular rate during AF of 60 to 80 beats per minute at rest and 90 to 115 beats per minute during exercise.1
Which drug for which patient?
Beta-blockers and nondihydropyridine calcium channel blockers (verapamil and diltiazem) and digoxin slow conduction through the AV node. Compared with placebo, beta-blockers and calcium channel blockers are effective for controlling the ventricular rate in patients with AF, both at rest and during exercise.17 In the AFFIRM trial, rate control was achieved in 70% of patients treated with beta-blockers vs 54% of patients taking calcium channel blockers.9
That said, the type of drug you use to achieve rate control should be an individual decision based on characteristics of your particular patient. In general, beta-blockers are preferable for patients with myocardial infarction or ischemia, and for any patient in a high adrenergic state, whereas calcium channel blockers should be used for patients with severe asthma or chronic obstructive pulmonary disease. Consider using digoxin for patients with CHF or hypotension, because both beta-blockers and calcium channel blockers can precipitate hemodynamic deterioration in these patients.