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Continuous rhythm monitoring after cardiac surgery held clues to help identify people prone to late postoperative atrial fibrillation (POAF) and any associated adverse events.

In the RACE V prospective cohort study, over half of the 98 coronary artery bypass grafting patients studied had at least one POAF episode detected during 2.5 years of monitoring for atrial fibrillation (Afib or AF).

A person's overall longest individual POAF episode during follow-up was strongly linked to a higher total POAF burden after cardiac surgery (P<0.001) -- suggesting it as a surrogate variable for POAF burden during intermittent rhythm monitoring, according to Ulrich Schotten, MD, PhD, of Maastricht University Medical Centre in the Netherlands, and colleagues reporting in .

Several characteristics of early POAF turned out to be predictors of late POAF occurring after 90 days. The strongest was early POAF burden -- or the percentage of time spent in Afib during the first 90 postoperative days -- followed by longest individual early POAF episode and the number of early POAF episodes.

Putting these variables together allows "for more accurate risk stratification compared to early-POAF incidence alone," the study authors wrote.

Afib is the most common complication after cardiac surgery, occurring in 30-60% of people. While perioperative beta-blockers are recommended, they are often withdrawn due to side effects. Interventions such as temporary spinal stimulation and posterior left pericardiotomy have shown some promise, whereas botulinum toxin type A has not been successful for prevention of POAF.

In the present report, Schotten and colleagues reported that people at higher risk for an increased burden of late POAF might have been flagged prior to surgery by preoperative echocardiographic characteristics, namely a reduced left atrial total ejection fraction and increased maximum right atrial volume indexed for body surface area.

"Our findings add to the understanding of late-POAF and demonstrate the vast differences in its presentation, which should be considered in the decision-making process for the long-term management of POAF patients," Schotten's group wrote.

"However, while the longest POAF episode duration may serve as a surrogate marker for overall POAF burden, its impact on downstream outcomes, particularly the risk of stroke, remains unknown," the investigators cautioned. "In the non-surgical populations, several studies showed a greater stroke risk in patients with persistent AF compared to [paroxysmal] AF, but the impact of device-detected AF burden on individual stroke risk is still a matter of debate."

Their observational study nevertheless supported device-detected late POAF as having potential harm in terms of long-term clinical outcomes. A "higher late-POAF burden was associated with atrial functional remodeling during follow-up, indicated by increased atrial volumes and reduced atrial emptying fraction, and with an increased incidence rate of both overall and cardiovascular adverse events," the authors reported.

Schotten and colleagues's study included 98 consecutive people (mean age 66.9 years, 76.5% men) undergoing cardiac surgery who were equipped with Medtronic's Reveal Linq implantable loop recorder (ILR). Among them, 16 had a preoperative history of paroxysmal Afib and 11 had a history of persistent Afib.

The ILR detected all POAF episodes lasting at least 2 minutes. However, for the sake of device memory and storage capacity, study participants were required to perform a manual data transfer from the ILR to a secure central database every 7 days. Investigators monitored transmission compliance on a weekly basis and contacted patients who did not transmit as instructed.

Study participants comprised an adult cohort in which 68.4% underwent coronary artery bypass grafting. All underwent transthoracic echocardiography in the months leading up to surgery and again at the 2.5 year follow-up.

The proportion of those having at least one POAF episode detected by the ILR reached 54.1%, including 46.9% with early POAF and 36.7% with late POAF.

There were a total of over 3,600 detected episodes during 2.5 years in those 53 people, with 28.5% of episodes during the early period.

Compared with early POAF captured only during the first postoperative month, POAF episodes occurring during months 2 and 3 were better predictors of late POAF, the data suggested.

Study authors acknowledged the small sample and the representation of various indications for surgery in their analysis.

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