The results of this study suggest that the concentrations of bioactive phospholipid substances, including lysophosphatidylcholine [LysoPC (0-0/16:0)], lysophosphatidylethanolamine [LysoPE (18:0/0-0 and 20:0/0-0)], platelet-activating factor (PAF), and 1-O-hexadecyl-lyso-sn-glycero-3-phosphocholine (Lyso-PAF), are lower in the AF than in the HF. Here, PCLAF is linked to atrial fibrillation.