Composition of Coronary Thrombus in Acute Myocardial Infarction

Objective To analyse composition of coronary thrombus in vivo, in ST-elevation Myocardial Infarction (STEMI) patients. Background The dynamic process of intracoronary thrombus formation in STEMI patients is poorly understood. Methods Intracoronary thrombi (n=45) were obtained by thromboaspiration in 288 consecutive STEMI patients presenting for primary percutaneous intervention and analyzed using high definition pictures taken with a scanning electron microscope. Plasma biomarkers (TnI, CRPus, IL-6, PAI-1, sCD40 ligand and TNF-α) and plasma fibrin clots viscoelastic properties were measured simultaneously on peripheral blood. Results Thrombi were mainly composed of fibrin (55.9±18%) with platelets (16.8±18%), erythrocytes (11.5±9%), cholesterol crystal (5.2±8.4%) and leukocytes (1.3±2.0%). The median ischemic time was 175 min IQR 140-297. Ischemic time impacted thrombi composition, resulting in a positive correlation with intracoronary thrombus fibrin content, r=0.38, p=0.01 and a negative correlation with platelet content r=-0.34, p=0.02. Thus, fibrin content increased with ischemic time, ranging from 48.4±21% (6 hours) (p=0.02), while platelet content decreased from 24.9±23% (6 hours) (p=0.07). Soluble CD40 ligand was positively correlated to platelet content in the thrombus (r=0.40, p=0.02) and negatively correlated with fibrin content (r=-0.36; p=0.04). Multivariate analysis indicated that ischemic time was the only predictor of thrombus composition with a 2-fold increase of fibrin-content per ischemic hour (adjusted OR2 1.03-3.7 p=0.01). Conclusions In acute STEMI, platelet and fibrin contents of the occlusive thrombus are highly dependent of ischemic time, which may have a direct impact on the efficacy of drugs or devices used for coronary reperfusion.