Altered distributions of monocyte subsets are associated with various cardiovascular diseases such as coronary artery disease, stroke and atrial fibrillation.[15–18] Human monocyte subpopulations are defined by different expression profiles of the cell surface molecules CD 14 (lipopolysaccharide (LPS) receptor) and CD16 (Fcγ-III receptor).[19] Three subpopulations can be distinguished, classical (CD14++CD16−), non-classical (CD14+CD16++) and intermediate (CD14++CD16+).[20, 21]. Here, CD14 is linked to atrial fibrillation.