Atrial fibrillation after bypass surgery found in almost half of patients

LMU University Hospital-led investigators report a higher-than-expected 1-year incidence of new-onset atrial fibrillation after coronary artery bypass grafting, associated with a very low burden beyond 30 days.

Postoperative atrial fibrillation (AF) is among the most common early complications after cardiac surgery with a reported incidence close to 30%, linked to longer hospital stays, higher costs, discomfort, and observational links to thromboembolic stroke, heart failure, and recurrence.

North American guidelines indicate that 60 days of oral anticoagulation is reasonable, with subsequent reassessment, and European guidelines advise consideration of long-term anticoagulation in patients with new-onset AF after cardiac surgery.

Previous large cohort studies relied on brief in-hospital telemetry and intermittent post-discharge monitoring, leaving incidence, burden, and recurrence insufficiently characterized and prompting continued long-term surveillance.

In the study “Long-term continuous monitoring of new-onset atrial fibrillation after coronary artery bypass grafting,” published in JAMAThe investigators conducted a multicenter prospective cohort study to test whether the 1-year incidence of AF after coronary artery bypass grafting (CABG) exceeded previous literature and to assess the burden of AF.

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

Patients were monitored with continuous rhythm monitoring using an insertable cardiac monitor placed at the skin closure. AF was defined as episodes detected and assessed by the device lasting at least two minutes.

Within one year, 95 of 198 patients developed new AF, giving a cumulative incidence of 48% with a 95% CI of 41% to 55%. Standard monitoring identified a cumulative incidence of 34% with a 95% CI of 27% to 41% and Gray test P = 0.01 compared to continuous monitoring. Sensitivity analyzes using longer episode thresholds produced cumulative incidences of 46% at four minutes, 45% at six minutes, and 44% at 12 minutes.

In the new-onset AF cohort, the median AF burden in the first year was 0.07%, corresponding to 370 minutes. The first postoperative days were those with the longest duration of arrhythmia, with a median burden of 3.65% on days 1 to 7, 0.04% on days 8 to 30, and 0% on days 31 to 365. In total, 2,053 episodes, totaling 2,522 hours, were recorded, with a median duration of six minutes and a median time to incident of 3.3 days. Asymptomatic presentations accounted for 63% of episodes and 67% were not captured by standard surveillance.

Among the 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 after 30 days occurred in 19 of 90 patients with incident episodes before 30 days, totaling 554 episodes with a median duration of four minutes. Asymptomatic recurrences accounted for 43% of these subsequent episodes, and 3% were detected by standard surveillance.

The authors conclude that continuous monitoring reveals significantly more AF than standard monitoring, while the measured burden remains very low after 30 days.

Their results call into question long-term routine oral anticoagulation after the onset of AF after CABG and support re-evaluation 30 days after treatment initiation.

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