HMN 2025: How Atrial fibrillation after bypass is found in nearly half of patients

Investigators led by LMU University Hospital report a higher-than-expected one-year incidence of new-onset atrial fibrillation after coronary artery bypass grafting, paired with very low burden beyond 30 days.

Postoperative atrial fibrillation (AF) ranks among the most frequent early complications after cardiac surgery with reported incidence near 30%, tying into longer hospital stays, higher costs, discomfort, and observational links to thromboembolic stroke, heart failure, and recurrence.

North American guidelines state that 60 days of oral anticoagulation is reasonable with later reassessment, and European guidance advises that long-term anticoagulation should be considered in patients with new-onset AF after cardiac surgery.

Previous large cohort studies leaned on brief in-hospital telemetry and intermittent checks after discharge, leaving incidence, burden, and recurrence insufficiently characterized and prompting calls for long-term continuous monitoring.

In the study, “Long-Term Continuous Monitoring of New-Onset Atrial Fibrillation After Coronary Artery Bypass Grafting,” published in JAMA, researchers conducted a prospective multicenter cohort study to test whether one-year AF incidence after coronary artery bypass grafting (CABG) exceeds prior literature and to assess AF burden.

Enrollment involved 198 adults at two academic cardiac surgery centers in Germany, all undergoing first-time isolated CABG for three-vessel or left main disease, without prior arrhythmias, monitored for one year after implant of a device during surgery.

Patients were followed through continuous rhythm surveillance using an insertable cardiac monitor placed at skin closure. AF was defined as device-detected and adjudicated episodes lasting at least two minutes.

Within one year, 95 of 198 patients developed new-onset AF, yielding a cumulative incidence of 48% with a 95% CI of 41%–55%. Standard monitoring identified a 34% cumulative incidence with a 95% CI of 27%–41% and Gray’s test P = .01 versus continuous monitoring. Sensitivity analyses using longer episode thresholds produced cumulative incidences of 46% at four minutes, 45% at six minutes, and 44% at 12 minutes.

Across the cohort with new-onset AF, median AF burden over the first year measured 0.07%, corresponding to 370 minutes. Early postoperative days carried the most arrhythmia time, with median burden of 3.65% on days 1–7, 0.04% on days 8–30, and 0% on days 31–365. A total of 2,053 episodes, accounting for 2,522 hours, were recorded, with a median episode length of six minutes and a median time-to-incident episode of 3.3 days. Asymptomatic presentations comprised 63% of episodes, and 67% were not captured by standard monitoring.

Among 95 patients with AF, 73 patients had incident episodes within seven days and 90 within 30 days, and 45% of accumulated AF time occurred within the first seven days and 77% within 30 days.

Recurrent AF later than 30 days appeared in 19 of 90 patients with incident episodes prior to 30 days, totaling 554 episodes with a median length of four minutes. Asymptomatic recurrences comprised 43% of these later episodes, and 3% were detected by standard monitoring.

The authors conclude that continuous monitoring uncovers substantially more AF than standard surveillance, while measured burden remains very low after 30 days.

Their findings question routine long-term oral anticoagulation after new-onset AF following CABG and support reassessment at 30 days when treatment is initiated.

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