CAVEATS: Unblinded study excluded very old, high risk
This was not a blinded study, so both patients and providers knew the target heart rates. However, the major outcomes were determined with relative objectivity and were not different between the 2 groups, so it is unlikely that this knowledge would have a major effect on the results. Nonetheless, this is a single study, and the findings are not yet supported by other large, prospective studies.
The researchers did not enroll patients >80 years, who have a higher incidence of atrial fibrillation and are less likely than younger patients to tolerate higher doses of rate-controlling medications. Also excluded were sedentary patients and those with a history of stroke, which resulted in a lower-risk study population. However, 40% of the subjects had a CHADS score ≥2 (an indication of high risk of stroke in patients with atrial fibrillation), and subgroup analysis found that the results applied to higher-risk groups.
Finally, it is possible that it may take longer than 3 years (the duration of study follow-up) for higher ventricular rates to result in adverse cardiovascular outcomes and that there could be a benefit of strict rate control over a longer period of time.
CHALLENGES TO IMPLEMENTATION: Guidelines do not reflect these findings
These findings are not yet incorporated into the ACC/AHA/ESC guidelines or those issued by other organizations. Clinical inertia may stop some physicians from reducing medications for patients with atrial fibrillation, but in general, both doctors and patients should welcome an easing of the drug burden.