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Rate Control May Edge Out Rhythm Control For Atrial Fibrillation

Treatment of atrial fibrillation, the most common sustained cardiac arrhythmia, is likely to change markedly in the wake of reports from two major studies in North America and Europe.

Contrary to prevailing practice, use of rhythm control for atrial fibrillation offers no survival advantage over rate control and is linked with higher rates of adverse drug effects.

Moreover, the rhythm approach does not result in lower risk of stroke, improved quality of life or improved cognitive function, all of which have been presumed to be benefits of this over the "heart rate" strategy.

These are the dramatic findings of the massive North American Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) trial supported by the United States National Heart, Lung and Blood Institute of the National Institutes of Health (NIH).

Echoing these results are those of a smaller European study led by Dr Isabelle C. Van Gelder from the University Hospital, Groningen, the Netherlands.

The researchers, while suggesting their conclusion does not necessarily apply to patients with first-time atrial fibrillation, found rate control is not inferior to rhythm control for preventing death and morbidity from cardiovascular causes.

Until now, optimal management strategy for atrial fibrillation has been uncertain. However, the preferred and most frequently used initial therapy has been to restore and maintain a normal heart rhythm.

Now, the mutually-confirming findings of these two studies suggest rate control is an acceptable, and often preferred, therapeutic approach to this common disorder, although both sets of authors underline that anticoagulant therapy should be maintained, whatever strategy is used.

The AFFIRM trial was a multicentre, randomised comparison of the two approaches to treatment in more than 4,000 patients with atrial fibrillation and a high risk of stroke or death. Primary end point was overall mortality.

Of 4,060 patients enrolled, 70.8 percent had a history of hypertension, and 38.2 percent had coronary artery disease. Of the 3,311 patients with echocardiograms, left atrium was enlarged in 64.7 percent, and left ventricular function was depressed in 26 percent.

There were 356 deaths among those assigned to rhythm-control therapy and 310 in those on rate control (mortality at five years, 23.8 percent and 21.3 percent respectively; hazard ratio 1.15).

More patients on rhythm than on rate control were hospitalised, and there were also more adverse drugs effects in the rhythm group.

In both treatment groups, the majority of strokes occurred after warfarin had been stopped or when the international normalised ratio was sub-therapeutic.

In the European study, 522 patients with persistent atrial fibrillation after a previous electrical cardioversion were randomly assigned to one of the two treatments.

Primary end point was a composite of death from cardiovascular causes, heart failure, thromboembolic complications, bleeding, pacemaker implant and severe adverse drug effects.

Those in the rate-control group received oral anticoagulant drugs and rate-slowing medication while those on rhythm control underwent serial cardioversions and received anti-arrhythmic drugs and oral anticoagulants.

After a mean of 2.3 ± 0.6 years, 39 percent of the 266 patients on rhythm control versus 10 percent of the 256 on rate control had sinus rhythm.

Primary end point occurred in 44 patients (17.2 percent) in the rate control and in 60 (22.6 percent) in the rhythm group.
N Engl J Med 2002;347:1825-33 and N Engl J Med 2002;347:1834-40.

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