CORRESPONDENCE: LETTERS TO THE EDITOR
Reply
Brian Olshansky, MD,
Lynda Rosenfeld, MD,
Alberta Warner, MD,
Allen Solomon, MD,
Gearoid O'Neill, MD,
Arjun Sharma, MD,
Edward Platia, MD,
Gregory Feld, MD,
Toshio Akiyama, MD,
Michael Brodsky, MD,
H. Leon Greene, MD The AFFIRM Investigators
University of Iowa Hospitals, 200 Hawkins Drive, Iowa City, IA 52242
(Email: brian-olshansky{at}uiowa.edu).
We thank Dr. Van Gelder and colleagues and Dr. Shelton for their interest in our study (1). We agree with Dr. Van Gelder and colleagues that the optimal heart rate in atrial fibrillation (AF) during rest and exercise is unknown. Perhaps minimal effort to achieve rate control during AF is sufficient. However, absence of adequate rate control can lead to adverse consequences such as tachycardia-induced cardiomyopathy. Our Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) substudy was not designed to evaluate the mortality and morbidity of inadequate rate control; thus, we cannot comment on these end points.
Both ablation of the atrioventricular junction and pacemaker insertion were allowed "innovative" therapies in the AFFIRM study, and they may have contributed to the relatively frequent use of this approach. Furthermore, attempting to achieve more "stringent" rate control may have led to more symptomatic drug-induced bradycardia and subsequent pacemaker insertion in the AFFIRM study, compared to the more "lenient" criteria used in the RAte Control versus Electrical cardioversion (RACE) study. However, the patient population in the AFFIRM study was not directly comparable to that in RACE, and pacemaker implantation per capita in the U.S. is higher than in Europe. These factors may have influenced the differences between these two studies.
We agree that a long-term, prospective, randomized trial would be useful. We applaud Dr. Van Gelder and colleagues for pursuing answers to some of these difficult issues in the RAte Control Efficacy in permanent atrial fibrillation (RACE II) study.
Dr. Shelton concurs that the optimal approach to rate control remains primarily based on clinical experience. He notes that 248 patients in the AFFIRM study crossed over to the rhythm-control group, and 108 patients underwent ablation of the atrioventricular junction (1). Many patients (approximately one-half) in the rate-control group were actually in sinus rhythm at any given visit, and their heart rates thus were not included in the data for that follow-up visit. Indeed, the numbers of patients reported for each follow-up visit interval were considerably less than the 2,027 randomized to the rate-control arm. However, the AFFIRM study experience was far larger than other studies reported to date.
Although Dr. Shelton is correct in stating that care should be taken in interpreting the data, it should be noted that patients with permanent AF are the most underrepresented segment of patients with AF in the AFFIRM study population.
Although the AFFIRM study was not designed to evaluate specific avenues to rate control, the approach we described is a composite of clinical experience utilized by a wide range of physicians who were involved in the study. Most patients can achieve adequate rate control during AF. As seen in routine clinical practice, unless permanent AF is present, not all patients will be in AF at every visit. Furthermore, the study was not designed specifically to evaluate patients with paroxysmal AF, permanent AF, or younger patients not at risk for stroke or death. It is not known whether the approaches described for the AFFIRM study patients will apply to other patient populations with AF. Clearly there is a need for carefully controlled, prospective, randomized, multicenter clinical trials to evaluate further the optimal approach to rate control in many different patient populations.
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References
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- Olshansky B, Rosenfeld LE, Warner AL, et al. AFFIRM investigators The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study: approaches to control rate in atrial fibrillation J Am Coll Cardiol 2004;43:1201-1208.[Abstract/Free Full Text]
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