Although the number of randomized trials evaluating atrial fibrillation increased by more than 200 percent from 2001 to 2014, there was no significant increase in the use of level A evidence used in guidelines.

Lead researcher Adam S. Barnett, MD, of the Duke Clinical Research Institute, and colleagues published their results online in JAMA Cardiology on Dec. 14.

The researchers noted that the American College of Cardiology (ACC) and American Heart Association (AHA) have published atrial fibrillation guidelines since 2001. The Heart Rhythm Society joined the ACC and AHA in 2011 as an author and stakeholder.

In this analysis, the researchers evaluated recommendations from the atrial fibrillation guidelines in 2001, 2006, 2011 and 2014. They also searched the MEDLINE database for atrial fibrillation studies published from 2001 to 2014.

During that time period, the annual number of publications on atrial fibrillation increased 255 percent, while the annual number of randomized trials increased 244 percent. The researchers added that number of guideline recommendations increased from 95 to 113, but there was no statistically significant differences in the proportion of recommendations assigned to each class of recommendation or level of evidence.

The use of level A evidence increased from 8.4 percent to 8.8 percent of studies, while the use of level B evidence increased from 30.5 percent to 39.8 percent and the use of level C evidence decreased from 60.0 percent to 51.3 percent.

From 2001 to 2014, the use of level C evidence decreased in all categories except for antithrombotic therapy, the use of level B evidence increased in all categories except for miscellaneous and the use of level A evidence decreased within antithrombotic therapy but remained constant or increased in the other categories. None of the changes were statistically significant, according to the researchers.

The proportions of the class of recommendations did not significantly change from 2001 to 2014, either. In 2014, 43.4 percent of the recommendations were class I, 43.4 percent were class IIa/IIb and 13.3 percent were class III.

The researchers added that the level of evidence was downgraded in six of 21 recommendations and upgraded in two of 21 recommendations that were present in the 2001 and 2014 guidelines. Meanwhile, the class of recommendation was not downgraded in any recommendation and was upgraded in two of 21 recommendations.

The analysis had a few limitations, according to the researchers, including that they did not account for changes in the aims and methodology used in the guidelines. They also did not include guidelines from other organizations such as the European Society of Cardiology or the American College of Chest Physicians.

“Guidelines are only as good as the evidence underlying them,” Jonathan Piccini, MD, MHS, the study’s senior author, said in a news release. “Despite great advances in the treatment of atrial fibrillation, a lot of important clinical questions remained unanswered. For example, rate control—a key component of [atrial fibrillation] care—does not have any treatment recommendations supported by the highest level of evidence. Thus, as we design new trials in the future, we need to make sure they address practical treatment decisions in a pragmatic way that helps practicing clinicians.”