A 70-year-old man comes to the clinic for routine follow-up of hypertension and is found to have new atrial fibrillation of unknown duration.
Should antiarrhythmic medications be used to restore sinus rhythm for patients with atrial fibrillation?
There is no evidence that rhythm control in older patients with atrial fibrillation is more effective than rate control for improving patient-oriented outcomes.1
Atrial fibrillation increases the risk of mortality and stroke. Furthermore, diminished atrial filling of the ventricles and irregular ventricular contraction can reduce cardiac output, leading to palpitations, dyspnea, and dizziness. Whereas rate-control strategies for managing atrial fibrillation advocate medically slowing ventricular response to the fibrillating atrium and using anticoagulation to reduce stroke risk, rhythm-control strategies involve medical or electrical conversion to sinus rhythm to improve hemodynamics and symptoms and, theoretically, reduce stroke risk.
The two studies2,3 evaluated in this Cochrane review1 showed that in patients older than 60 years, use of a number of different medications (alone or combined) for pharmacologic cardioversion of atrial fibrillation—including amiodarone (Cordarone), quinidine, sotalol (Betapace), disopyramide (Norpace), and flecainide (Tambocor)—did not improve mortality rates or stroke rates compared with rate control using calcium channel blockers, beta blockers, or digoxin, alone or in combination. Moreover, 50 percent of strokes in patients receiving antiarrhythmics occurred while they were in sinus rhythm, and long-term maintenance of sinus rhythm was achieved in only 56 to 62 percent of patients. Thus, cardioversion of a fibrillating atrium to reduce stroke risk and eliminate the need for warfarin (Coumadin) therapy does not seem to be a reliable solution; long-term maintenance of sinus rhythm is difficult, and those who have successful cardioversion appear to need long-term anticoagulation.
Although concern has been raised that the use of antiarrhythmic medications for atrial fibrillation will increase the risk of malignant dysrhythmias, these were uncommon with rate-control and rhythm-control strategies in the two studies2,3 reviewed. Results of one of the studies2 suggested there may be an increased mortality risk with rhythm control in patients without heart failure, but the numbers of patients with heart failure were low, and definitive data on management of atrial fibrillation in the setting of heart failure are lacking. The same study2 also showed that older patients and those with coronary artery disease may be at higher risk of death with rhythm control compared with rate control.
This review1 provides further evidence in support of recent guidelines on the management of atrial fibrillation. The American College of Cardiology and the American Heart Association note that there is a paucity of evidence indicating restoration and maintenance of sinus rhythm is more beneficial than rate control, and that the data available suggest no definite advantage of one approach over the other.4 The American Academy of Family Physicians and the American College of Physicians go further, recommending rate control with chronic anticoagulation as the best strategy for most patients with atrial fibrillation.5 Both guidelines,4,5 however, state that rhythm control may be appropriate in certain situations, depending on specific patient characteristics such as the desire for symptom control or improvement in exercise tolerance.
Background. Atrial fibrillation is the most common cardiac dysrhythmia. It is associated with significant morbidity and mortality. There are two approaches to the management of atrial fibrillation: controlling the ventricular rate or converting to sinus rhythm in the expectation that this would abolish its adverse effects.
Objectives. To assess the effects of pharmacologic cardioversion of atrial fibrillation in adults on the annual risk of stroke, peripheral embolism, and mortality.
Search Strategy. The authors1 searched the Cochrane Controlled Trials Register (Issue 3, 2002), MEDLINE (2000 to 2002), EMBASE (1998 to 2002), CINAHL (1982 to 2002), and Web of Science (1981 to 2002). They hand searched the following journals (all 1997 to 2002): Circulation, Heart, European Heart Journal, andJournal of the American College of Cardiology, and selected abstracts published on the Web site of the North American Society of Pacing and Electrophysiology (2001, 2002).
Selection Criteria. Randomized controlled trials or controlled clinical trials of pharmacologic cardioversion versus rate control in adults (older than 18 years) with acute, paroxysmal, or sustained atrial fibrillation or atrial flutter, of any duration and of any etiology.
Data Collection and Analysis. One reviewer applied the inclusion criteria and extracted the data. Trial quality was assessed and the data were entered into RevMan.
Primary Results. The authors identified two completed studies: AFFIRM2 (n = 4,060) and PIAF3 (n = 252). The authors found no difference in mortality between rhythm control and rate control (relative risk = 1.14; 95% confidence interval, 1.00 to 1.31). Both studies showed significantly higher rates of hospitalization and adverse events in the rhythm-control group and no difference in quality of life between the two treatment groups. In AFFIRM, there was a similar incidence of ischemic stroke, bleeding, and systemic embolism in the two groups. Certain malignant dysrhythmias were significantly more likely to occur in the rhythm-control group. There were similar scores of cognitive assessment. In PIAF, cardioverted patients enjoyed an improved exercise tolerance, but there was no overall benefit in terms of symptom control or quality of life.
Reviewers’ Conclusions. The authors conclude that there is no evidence that pharmacologic cardioversion of atrial fibrillation to sinus rhythm is superior to rate control. Rhythm control is associated with more adverse effects and increased hospitalization, and it does not reduce the risk of stroke. This conclusion cannot be generalized to all persons with atrial fibrillation. Most of the patients included in these studies were older than 60 years and had significant cardiovascular risk factors.
These summaries have been derived from Cochrane reviews published in the Cochrane Database of Systematic Reviews in the Cochrane Library. Their content has, as far as possible, been checked with the authors of the originalreviews, but the summaries should not be regarded as an official product of the Cochrane Collaboration; minorediting changes have been made to the text (http://www.cochrane.org).
An important limitation of this review1 is that the two studies2,3 evaluated focused mainly on patients older than 60 years without heart failure or ventricular dysfunction. Thus, it sheds little light on the management of atrial fibrillation in younger populations or in patients with heart failure.
For the routine management of atrial fibrillation, this review1 supports using rate control with anticoagulation primarily. If rhythm control is attempted, continued use of anticoagulation appears necessary to maintain a reduced risk of stroke.