NPPB and atrial fibrillation: It would appear that high endogenous EPO confers a higher mortality risk that is not directly related to anemia or mild-to-moderate renal dysfunction and cannot be explained by immediate general operative risk (as assessed by STS score), relevant specific heart disorders such as atrial fibrillation, age, key cardiac laboratory biomarkers such as NTproBNP, and hs-CRP, an inflammatory marker.