How Useful is the RED-AF Tool for Improving Outcomes in Patients with Atrial Fibrillation?

Researchers from Vanderbilt University have developed a new tool for deciding when hospitals should admit patients with symptomatic atrial fibrillation (AF) and when they should send them home.

Emergency departments currently admit 70% of patients who present with systematic AF, but the 30-day risk of stroke or death for such patients is only 1% to 3%, said Tyler Barrett, MD, speaking at the American College of Emergency Physicians 2014 Scientific Assembly.

Barrett, who presented findings at a special session for research most likely to have an impact on clinical practice, argued such high admission rates were not only needless but financially unsustainable as the cost of hospital care and the number of people with AF both continue to grow.

In an effort to distinguish which cases really merit hospitalization, Barrett and colleagues developed the Risk Estimator Decision Aid for Atrial Fibrillation (RED-AF).

The risk estimator is a formula that produces a single risk score from information about 12 risk factors: age, sex, hypertension, smoking, inadequate 2-hour emergency department ventricular rate control, dyspnea, ongoing beta-blocker use, ongoing diuretic use, heart failure, peripheral edema, chronic obstructive pulmonary disease, and heart palpitations in the emergency department.

The study team validated its tool with data from the ongoing Atrial Fibrillation and Flutter Outcome Risk Determination (AFFORD) trial. Team members plugged in all the relevant data about 497 study participants who went to the emergency department with symptomatic AF. Then, they determined the optimal risk threshold by noting which patients suffered during the next 30 days from adverse events — another emergency department visit or hospital admission, stroke, decompensated heart failure, myocardial infarction, heart arrhythmias or death.

Some 120 (24%) of the patients experienced some adverse event within 30 days of their initial emergency department visits. Recurrence of AF symptoms brought 39 of them back to the emergency room and caused doctors to admit another 32 of them into the hospital. Worse, 13 patients had strokes and 4 died from causes related to AF.

The risk estimator performed significantly better than many emergency departments in determining which patients to send home, though there remains room for improvement.

Barrett told his audience that, when his team used a RED-AF score of 87 as the threshold between admitting patients or sending them home, the tool exhibited a sensitivity of 0.96, a specificity of 0.19, a positive predictive value of 0.27, and a negative predictive value of 0.93.

Reaction to the study results, which were also published in the Annals of Emergency Medicine, has been mixed.

Some physicians have noted that the low positive predictive value indicates use of the formula would sill lead to much needless hospitalization, particularly among patients who smoke.

“Applying this score seems unlikely to outperform our usual clinical assessment,” wrote Daniel J. Pallin, MD, MPH, in a research review published in Journal Watch. “Most ED patients with atrial fibrillation do well in the short term. Emergency department providers should emphasize the need for anticoagulation and the value of a visit to the patient's usual provider as soon as possible after the ED visit.”

Other physicians, however, say that the study results suggest that, whatever the tool’s imperfections, it will still allow emergency room doctors to send more patients home than they currently do. Better still, the risk estimator’s high negative predictive value should allow them to feel confident that they are not sending many people home in error.