Differences in Microparticle Release in Patients With Acute Coronary Syndrome and Stable Angina

Background: Microparticles (MP) are vesicles released from activated or apoptotic cells. Endothelial MP (EMP) are derived from injured endothelium, platelet MP (PMP) from activated platelets, and Annexin V positive MP (AMP) from apoptotic endothelial cells. The aim was to assess the release of MP and its association with inflammation and atherosclerotic burden. Methods and Results: AMP, EMP and PMP were measured on admission (Day 0) in 33 patients with stable angina (SA) and 43 patients with acute coronary syndrome (ACS) undergoing percutaneous coronary interventions (PCI). In SA, peripheral artery disease (PAD) was assessed by ultrasound examination. In 30 of the 76 patients (20 ACS and 10 SA), MP, high-sensitivity-C-reactive protein (hs-CRP), and troponin T (TnT) levels were also assessed 24h (Day 1) and 48h (Day 2) after PCI. AMP, EMP, and PMP were higher in ACS than in SA (all P<0.01). In the SA group, AMP, PMP, and EMP were similar in patients with or without PAD. In the ACS group, AMP increased until Day 2 (P=0.001), while EMP and PMP peaked on Day 1 (P<0.01) then decreased to baseline values. Day 2 AMP correlated with Day 2 TnT levels (r=0.43, P=0.01) while Day 1 EMP and PMP correlated with Day 1 hs-CRP (r=0.37, P=0.04 and r=0.33, P=0.05; respectively). Conclusions: Higher MP levels were observed in ACS than in SA. Atherosclerotic burden did not affect MP levels in stable patients.