CORRESPONDENCE: LETTER TO THE EDITOR
Beta-Blockers Versus Digoxin to Control Ventricular Rate During Atrial Fibrillation
Henrique H. Veloso, MD* and
Angelo A.V. de Paola, MD
* VOTCOR, Hospital da Venerável Ordem Terceira da Penitência, Rua Conde de Bonfim 1033, Rio de Janeiro, Brazil (Email: hhorta{at}cardiol.br).
The recent study of Olshansky et al. (1) investigated the approaches used to control rate, the effectiveness of rate control, and changeovers from one drug class to another in the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study. Comparing the cumulative achievement of adequate ventricular rate control and the time to discontinuation of rate-control therapy, the investigators concluded that beta-blockers were the most effective drugs. We believe the superiority of beta-blockers over other therapeutic options, particularly over digoxin, must be interpreted with caution.
Adequate ventricular rate control was cumulatively obtained in a similar proportion of patients taking beta-blockers alone and digoxin alone (59% vs. 58%, respectively), a result that was confirmed both during rest (68% for both therapies) and with exertion (72% vs. 70%, respectively). Afterwards, the researchers considered beta-blockers more effective, observing that, over time, more patients taking digoxin or a calcium channel blocker were changed to another drug (p < 0.0001). However, in this comparison, the group of patients using beta-blockers and calcium channel antagonists included those taking digoxin concomitantly, whereas the digoxin group included only individuals using this drug alone. It is possible to observe that, in patients using beta-blockers, the association of digoxin increased the proportion of adequate rate control from 59% to 70%, and this increment may have led to the observed superiority with beta-blocker therapy. Randomized studies have already demonstrated that the association of digoxin with beta-blockers is more effective than beta-blockers alone in this setting (2,3).
In their discussion, the investigators (1) stated that "because no placebo control was used in this trial, it is possible that no medication would have worked as well as digoxin did to control the rate." Because the randomization of the AFFIRM trial was not performed to compare drugs to control ventricular rate, this observation should not be restricted to digoxin. The concept that oral digoxin is efficient in controlling ventricular rate during atrial fibrillation is well accepted (4), despite being supported more by studies that demonstrated the reduction of ventricular rate after the initiation of the therapy (5) than by the sparse number of randomized placebo-controlled trials (6).
In conclusion, we do believe that the report by Olshansky et al. (1) from the AFFIRM study does not allow the conclusion that "beta-blockers were the most effective drugs" in controlling ventricular rate during atrial fibrillation. In their study, the efficacy of beta-blockers and digoxin, both used alone, was equivalent. Our opinion, in accordance with current guidelines for the management of atrial fibrillation, is that digoxin is still a first-line alternative to control ventricular rate in patients with atrial fibrillation, particularly in cases with congestive heart failure and left ventricular systolic dysfunction (4).
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1. Olshansky B, Rosenfeld LE, Warner AL, et al. AFFIRM Investigators The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) studyapproaches to control rate in atrial fibrillation. J Am Coll Cardiol 2004;43:1201-1208.[Abstract/Free Full Text]
2. Farshi R, Kistner D, Sarma JS, Longmate JA, Singh BN. Ventricular rate control in chronic atrial fibrillation during daily activity and programmed exercisea crossover open-label study of five drug regimens. J Am Coll Cardiol 1999;33:304-310.[Abstract/Free Full Text]
3. Khand AU, Rankin AC, Martin W, Taylor J, Gemmell I, Cleland JG. Carvedilol alone or in combination with digoxin for the management of atrial fibrillation in patients with heart failure? J Am Coll Cardiol 2003;42:1944-1951.[Abstract/Free Full Text]
4. Fuster V, Rydén LE, Asinger RW, et al. ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation: executive summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines and Policy Conferences (Committee to Develop Guidelines for the Management of Patients with Atrial Fibrillation): developed in collaboration with the North American Society of Pacing and Electrophysiology J Am Coll Cardiol 2001;38:1231-1266.[Free Full Text]
5. Koh KK, Kwon KS, Park HB, et al. Efficacy and safety of digoxin alone and in combination with low-dose diltiazem or betaxolol to control ventricular rate in chronic atrial fibrillation Am J Cardiol 1995;75:88-90.[CrossRef][Web of Science][Medline]
6. Ang EL, Chan WL, Cleland JG, et al. Placebo controlled trial of xamoterol versus digoxin in chronic atrial fibrillation Br Heart J 1990;64:256-260.[Abstract/Free Full Text]
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