New-Onset Atrial Fibrillation Post-CABG More Common, Lasts Longer in Men Than in Women

In the ongoing push to understand the link between CABG surgery and new-onset atrial fibrillation, a large, multicenter registry has found that women were at lower risk of developing post-CABG A-fib and that when they did their episodes were shorter. Moreover, the study, which used continuous in-hospital ECG/telemetry monitoring to track episodes of atrial fibrillation, picked up higher rates of the complication than are typically captured by the Society of Thoracic Surgeons (STS) definition, which defines post-operative A-fib (POAF) as requiring treatment (either medication or cardioversion).

Speaking with TCTMD, lead author Giovanni Filardo, PhD (Baylor Scott & White Health, Dallas, TX), noted that, until relatively recently, peri- and postoperative A-fib was believed to be “something that would resolve quickly and wouldn’t impact long-term outcomes. In other words, it was seen, for the hospital, as something that was just increasing costs.”

That’s changed. A host of studies have now linked POAF with increased morbidity and mortality, but the true incidence of the problem, which of its characteristics may be associated with worse outcomes, and whether these differ between men and women remain open questions.

Filardo and colleagues reported their findings online this week ahead of print in the November 2016 issue of Circulation: Cardiovascular Quality and Outcomes.

A Hypothesis Proved Wrong

Filardo et al reviewed the incidence of new A-fib among 11,236 consecutive patients undergoing CABG at four US centers, including one high-volume specialty hospital, over an 8-year period. In all, the unadjusted rate of post-CABG atrial fibrillation was 29.5%—30.2% in men and 27.4% in women. After adjustment for STS-recognized risk factors, women had a significantly lower risk than men of developing atrial fibrillation after CABG (OR 0.75; 95% CI 0.64-0.89].  Episodes of A-fib in women were also significantly shorter, although the number of episodes and the odds of stroke and A-fib at the time of discharge were no different between sexes.

Speaking with TCTMD, Filardo noted that his hypothesis going in was that women would have higher rates of A-fib because they are typically older, with more comorbidities at the time they develop significant coronary disease. “I was completely wrong,” he said with a laugh.

He also pointed to the ECG monitoring/telemetry used in this study, noting that the rates of A-fib documented using continuous monitoring were approximately 5% higher than what would have been picked up if the STS definition had been applied. “So what we found is that A-fib may be underrecognized and there may be more people at risk [of POAF-associated adverse outcomes] than we previously thought. It will be very interesting to see if those people who had atrial fibrillation according to our definition are at the same, lower, or higher risk compared to those patients who don’t have A-fib.”

The investigators believe their study is the largest multicenter study to look at both the incidence and characteristics of new, post-CABG atrial fibrillation according to patient sex. Filardo says he and his colleagues are planning to follow Medicare patients in the current cohort in order to examine whether differences in incidence and duration influence long-term outcomes, including mortality.

Asked whether POAF is a factor that should be given greater consideration when deciding on a revascularization strategy, Filardo pointed out that while A-fib rates following PCI are typically much lower than they are following CABG, the crude incidence rates for CABG and PCI cannot be compared, given the very different and confounding risk factor profiles in patients currently undergoing the two procedures.