New findings question the need for oral anticoagulants for patients who develop atrial fibrillation (AF) after coronary artery bypass grafting (CABG), showing that while the arrythmia may be more frequent than previous research has estimated, the burden of episodes is negligible. 

The study, appearing in JAMA, showed that while nearly half of 198 patients who underwent CABG developed AF within a year of the surgery, the median burden of arrythmia events was well less than 1%.

Previous research has indicated that AF emerges in roughly 30% of patients who undergo CABG. Although the new results point to a higher rate of the arrhythmia, they suggest “post-CABG AF is often transient, characterized by predominantly brief, self-limiting episodes rather than sustained or progressive arrhythmia,” said Florian Herrmann, MD, of the Department of Cardiac Surgery at LMU University Hospital in Munich, Germany, who led the study.

These findings challenge current guideline recommendations, which state that it is reasonable to administer long-term anticoagulants for new-onset AF after cardiac surgery, Herrmann said. “If AF is predominantly confined to the early postoperative period after CABG, the benefit of extended anticoagulation becomes questionable,” he said. “Our findings may help explain why previous studies have failed to demonstrate a clear benefit of anticoagulation in this patient population. Several studies have shown that the associated bleeding risk often outweighs the potential reduction in stroke risk.”

Herrmann and colleagues conducted a prospective cohort study that included 198 patients with three-vessel coronary artery disease, left main disease, and no history of arrythmias or those who received an insertable cardiac monitor during CABG. During the first year after surgery, 48% of patients developed new-onset AF.

The median burden of AF during the first year after CABG was 0.07%, which translated to 370 minutes, according to the researchers. Most of that burden occurred during the first week after surgery (3.65%), dropping to 0.04% on days 8-30 and to effectively 0% beyond that point. 

Given the results, Herrmann and his colleagues advised cardiologists managing AF after CABG to approach arrhythmia with caution.

“If anticoagulation is initiated, we recommend a reassessment 30 days after surgery,” he said. “Such an approach can help avoid unnecessary exposure to bleeding risks associated with prolonged anticoagulation in patients whose arrhythmia may not warrant long-term therapy.”

A Different Category?

The new data show “there really is something different about postoperative AF after cardiac surgery, and that the application of long-term therapies such as anticoagulation should be the exception rather than the norm,” according to Gregory M. Marcus, MD, MAS, of the University of California, San Francisco, who is the author of an editorial accompanying the journal article.

Current recommendations advise clinicians to avoid dismissing AF first observed during a critical illness, recommending thorough monitoring for recurrence in those circumstances. “But those same guidelines recognize that postoperative AF after cardiac surgery may represent a different category,” Marcus, associate editor at JAMA, wrote. “The primary lesson from these [findings] is that AF can indeed be reversible.”

The findings almost certainly do not apply to patients undergoing other types of surgical procedures, Marcus cautioned.

AF following open heart surgery occurs frequently, both in the immediate postoperative phase and long term, raising the risk for stroke in these patients, said Thomas P. Carrigan MD, MHSA, clinical cardiac electrophysiologist at St. Elizabeth Healthcare in Cincinnati and assistant professor at the University of Kentucky College of Medicine in Lexington. However, the current guideline recommending 2 months of powerful blood thinners for AF after CABG is based on limited scientific evidence, added Carrigan, who was not involved it the new study.

“The current recommendations should be revisited and possibly revised,” Carrigan said. “Patients are likely to be overtreated with anticoagulants, which can lead to extra risks without any clinical benefit.”

This study was funded by the Else Kröner-Fresenius-Stiftung and the Deutsche Forschungsgemeinschaft (German Research Foundation). 

Carrigan reported having no relevant financial conflict of interest. 

Martta Kelly is a medical journalist base in the New York metropolitan area.