AFib after CABG linked to minimal long-term stroke risk

Patients who developed new-onset postoperative atrial fibrillation (POAF) after coronary artery bypass graft (CABG) surgery showed a 33 percent reduced risk of thromboembolism long-term when compared to those with nonvalvular AFib (NVAF), according to a study published March 28 in JAMA Cardiology.

These findings suggest the two types of AFib aren’t equivalent in their downstream risk and raise questions about whether patients in both groups should be prescribed oral anticoagulants (OACs) at similar rates, wrote lead author Jawad H. Butt, MD, and colleagues. As always, there is the need to balance the risk of thromboembolism, including stroke, with the excess bleeding risk of OACs.

“We found that new-onset POAF after CABG surgery was associated with a lower long-term risk of thromboembolic events compared with that of primary NVAF, despite a similar predicted risk of thromboembolism,” Butt et al. wrote. “The association remained true after adjusting for comorbidities, concomitant pharmacotherapy, and postdischarge anticoagulation medication.”

Using Danish national registries for hospital and outpatient visits, as well as prescription drug filings, the researchers studied long-term outcomes of 2,108 patients who developed POAF after CABG against 8,432 matched patients with NVAF. They found:

  • Thromboembolism occurred at a rate of 18.3 events per 1,000 person-years for POAF versus 29.7 per 1,000 years for NVAF. The adjusted relative risk difference was 33 percent.
  • The use of post-discharge anticoagulation therapy was associated with similar decreases in risk of thromboembolism for both POAF (45 percent reduction) and NVAF (41 percent reduction). However, only 8.4 percent of POAF patients received OACs within 30 days of discharge, while 42.9 percent of NVAF patients were prescribed OACs.
  • Among all CABG patients, the risk of thromboembolism was 11 percent higher for those who developed POAF versus those who didn’t, but that figure failed to reach statistical significance.

According to the researchers, their study differs from previous ones on the same topic because it includes data on postdischarge anticoagulation therapy.

The authors of an accompanying commentary said a clinical trial is needed to more adequately determine the utility of OACs following POAF. Those patients appear to be at a relatively low risk of stroke compared to other AFib patients, but appear to derive significant relative benefit from anticoagulants in the rare cases in which they are prescribed.

“The results of this well-done study are complementary to prior work, conveying the same message that AFib following cardiac surgery may pose a lower long-term risk of stroke than traditional clinical AFib. This has important implications for how clinicians should treat patients with this common problem,” wrote Jeff S. Healey, MD, MSc; William F. McIntyre, MD; and Richard P. Whitlock, MD, PhD—all with the Population Health Research Institute at McMaster University in Canada.

“It is likely that some AF following cardiac surgery is indeed transient and caused by inflammation, while in other cases, it is typical clinical AFib in an at-risk individual that happens to receive a diagnosis for the first time in the postoperative setting. Identifying this latter group who may be at higher risk of AFib recurrence and stroke is not yet possible and should be a priority.”