An intense and short-lasting burst of neutrophil activation differentiates early acute myocardial infarction from systemic inflammatory syndromes.

"BACKGROUND: Neutrophils are involved in thrombus formation. We investigated. whether specific features of neutrophil activation characterize patients with. acute coronary syndromes (ACS) compared to stable angina and to systemic. inflammatory diseases.. METHODS AND FINDINGS: The myeloperoxidase (MPO) content of circulating. neutrophils was determined by flow cytometry in 330 subjects: 69 consecutive. patients with acute coronary syndromes (ACS), 69 with chronic stable angina. (CSA), 50 with inflammation due to either non-infectious (acute bone fracture),. infectious (sepsis) or autoimmune diseases (small and large vessel systemic. vasculitis, rheumatoid arthritis). Four patients have also been studied before. and after sterile acute injury of the myocardium (septal alcoholization). One. hundred thirty-eight healthy donors were studied in parallel. Neutrophils with. normal MPO content were 96% in controls, >92% in patients undergoing septal. alcoholization, 91% in CSA patients, but only 35 and 30% in unstable angina and. AMI (STEMI and NSTEMI) patients, compared to 80%, 75% and 2% of patients with. giant cell arteritis, acute bone fracture and severe sepsis. In addition, in. 32/33 STEMI and 9/21 NSTEMI patients respectively, 20% and 12% of neutrophils had. complete MPO depletion during the first 4 hours after the onset of symptoms, a. feature not observed in any other group of patients. MPO depletion was associated. with platelet activation, indicated by P-selectin expression, activation and. transactivation of leukocyte β2-integrins and formation of platelet neutrophil. and -monocyte aggregates. The injection of activated platelets in mice produced. transient, P-selectin dependent, complete MPO depletion in about 50% of. neutrophils.. CONCLUSIONS: ACS are characterized by intense neutrophil activation, like other. systemic inflammatory syndromes. In the very early phase of acute myocardial. infarction only a subpopulation of neutrophils is massively activated, possibly. via platelet-P selectin interactions. This paroxysmal activation could contribute. to occlusive thrombosis."