POSTOPERATIVE atrial fibrillation (POAF) risk prediction took a major step forward as new research showed that myeloperoxidase (MPO) measured directly from the pericardial space strongly predicted atrial fibrillation after coronary artery bypass grafting (CABG).
POAF remains one of the most common complications following cardiac surgery, affecting around one in three patients and increasing the risk of stroke, prolonged hospital stays, and long-term mortality. Despite existing clinical risk scores, accurately identifying patients at highest risk has remained challenging.
Pericardial MPO and Postoperative Atrial Fibrillation Risk
The study evaluated whether pericardial MPO levels, measured from selectively drained pericardial fluid, could improve postoperative atrial fibrillation prediction beyond conventional tools. The investigators enrolled 469 consecutive patients undergoing CABG, dividing them into derivation (201 patients) and validation (268 patients) cohorts. Nearly all patients (98.0%) underwent off-pump CABG, reflecting contemporary surgical practice.
POAF, defined as new-onset atrial fibrillation within seven days after surgery, occurred in 31.8% of the derivation cohort and 35.1% of the validation cohort. MPO concentrations were assessed in pericardial fluid and peripheral blood at baseline, immediately after surgery, and six hours postoperatively.
Pericardial MPO measured six hours after surgery emerged as the strongest independent predictor of POAF. MPO concentrations in selectively drained pericardial fluid were 25-fold higher than mixed drainage samples and 1,648-fold higher than serum levels (both p<0.001).
Building a More Accurate Prediction Model
Using multivariable logistic regression, the researchers developed the pcMPO-AF rule, integrating pericardial MPO with established clinical factors. The model demonstrated excellent discrimination, with an area under the curve of 0.908 in the derivation cohort and 0.865 in external validation. This performance exceeded that of commonly used scores, including CHA₂DS₂-VASc and HATCH.
These findings suggest that pericardial MPO captures both the vulnerable atrial substrate and the acute inflammatory trigger thought to drive POAF. Inflammation-driven atrial conduction inhomogeneity has long been implicated in postoperative arrhythmias, and this study provides clinically actionable biomarker evidence to support that mechanism.
Clinical Implications and Next Steps
The study was conducted at a single centre and included a high proportion of patients undergoing off-pump coronary artery bypass grafting, factors that may limit generalisability to other surgical settings. Nevertheless, the findings highlight the potential of pericardial biomarkers to refine perioperative risk stratification
If validated in broader surgical populations, the pcMPO-AF rule could help clinicians identify high-risk patients early and tailor preventive strategies. Further prospective studies will be needed to determine whether MPO-guided interventions can reduce POAF incidence and improve postoperative outcomes.
Reference
Luo L et al. Myeloperoxidase in selectively drained pericardial fluid predicts postoperative atrial fibrillation after coronary artery bypass grafting. Sci Rep. 2026; DOI:10.1038/s41598-025-32318-x.
