New-onset atrial fibrillation (NOAF) occurred in 18 percent of patients undergoing coronary artery bypass grafting (CABG) but just 0.1 percent of those receiving PCI, according to an analysis of the international EXCEL trial published in the Journal of the American College of Cardiology.
What’s more, the patients who developed NOAF within a few days of surgery were at a 3.02-fold risk of death and a 4.19-fold risk of suffering a stroke over the following three years. Compared to patients who didn’t develop atrial fibrillation (AFib) after CAGB, those who did had a higher 30-day risk of bleeding events and were more than twice as likely to meet the trial’s composite endpoint of death, heart attack or stroke within three years.
When NOAF didn’t occur, the rate of the primary endpoint didn’t differ significantly between PCI and CABG.
“The higher periprocedural rates of stroke with CABG compared with PCI that has been noted in most prior trials may in part be explained by the greater rate of NOAF after surgical revascularization,” wrote lead author Ioanna Kosmidou, MD, PhD, and colleagues. “Although a recent large registry-based analysis suggested that post-operative AF was a predictor only of early stroke, in the present study the increased rate of stroke with in-hospital NOAF emerged not within 30 days, but during long-term follow-up.”
Kosmidou et al. studied 1,812 patients with left main coronary artery disease and no AFib at hospital presentation. They were all deemed fit for either CABG or PCI by a heart team and randomized to one of the procedures.
The authors suggested the extremely low rate of AFib in the PCI-treated group could be due to the relatively low-risk study population, few of whom presented with acute MI. They found older age, greater body mass index, and reduced left ventricular ejection fraction (LVEF) were independent predictors of NOAF in patients undergoing CABG.
“Notably, NOAF was a stronger multivariable predictor of death after CABG than either diabetes or reduced LVEF. … PCI had superior three-year event-free survival compared with CABG if NOAF after surgery occurred. PCI may thus be preferred in selected patients who have a very high risk of NOAF after surgery,” Kosmidou and colleagues wrote.
A substudy of the EXCEL trial is underway and will assess the additional costs in treating patients who develop NOAF, the authors said. They added other studies are necessary to guide preventive measures for NOAF associated with CABG, and to assess whether long-term anticoagulation can improve outcomes for patients who do develop AFib following CABG.
In a related editorial, three physicians pointed out postoperative AFib (POAF) is often considered an isolated event and less dangerous than other AFib. The importance of the present study, they said, is it shows that is not the case—there is still a long-term adverse effect of POAF following cardiac surgery.
However, they questioned whether this development is truly responsible for downstream cardiovascular events.
“Several risk factors have been identified for post-operative stroke in the cardiac surgical population including older age, renal insufficiency, diabetes, left ventricular dysfunction, and hypertension,” the editorialists wrote. “Because many of these conditions are also risk factors for POAF, it is possible that POAF is just an incidental marker of other high-risk attributes that cause higher stroke and mortality rates. Although Kosmidou et al. perform extensive multivariable adjustment, confounding linkage among these risk factors can never be completely eliminated.”
The physicians said randomized trials are the only way to determine whether POAF is “truly causative” for death and stroke, or simply associated with those outcomes.