Thursday, June 28, 2012

Rhythm or rate control for atrial fibrillation?

- Kenny Lin, MD

For many years, the standard thinking regarding treatment of patients with atrial fibrillation was that drug therapy to restore sinus rhythm (rhythm control) was superior to drug therapy to slow the ventricular response rate (rate control). That all changed in 2002, when a clinical trial found no difference in survival between patients randomized to rhythm or rate control, and a higher incidence of adverse effects in the rhythm control group.

This trial and other evidence led the American Academy of Family Physicians to issue a guideline that recommended rate control with chronic anticoagulation as the preferred strategy for most patients with atrial fibrillation. A recent AFP review article echoed this guidance, assigning an "A" strength of evidence rating to the following statement:  "Rate control is the recommended treatment strategy in most patients with atrial fibrillation. Rhythm control is an option for patients in whom rate control is not achievable or who remain symptomatic despite rate control."

On occasion, however, evidence-based interventions achieve different results in primary care than in clinical trials. A study published earlier this month in the Archives of Internal Medicine used administrative databases in Quebec, Canada to compare mortality between older patients with atrial fibrillation who were initially prescribed rhythm or rate control therapy after their diagnoses. After experiencing similar mortality through 4 years of follow-up, patients in the rhythm control group had a significantly lower risk of death, with 23% lower relative mortality than patients in the rate control group at 8 years. These surprising results beg the question: was this new study somehow flawed? If not, as the subtitle of an accompanying editorial asked, can observational data trump randomized trial results?

Although it is unlikely that treatment guidelines will change any time soon, this study should remind clinicians that management of patients with newly diagnosed atrial fibrillation should be individualized, and the risks and benefits of different strategies discussed in detail before making treatment decisions.