Composition of Coronary Thrombus in Acute Myocardial Infarction

Objectives We sought to analyze the composition of coronary thrombus in vivo in ST-segment 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-alpha) and plasma fibrin clot 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 crystals (5.2 +/- 8.4%), and leukocytes (1.3 +/- 2.0%). The median ischemic time was 175 min (inter-quartile range: 140 to 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% (<3 h) up to 66.9 +/- 9% (>6 h) (p = 0.02), whereas platelet content decreased from 24.9 +/- 23% (<3 h) to 9.1 +/- 6% (>6 h) (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 odds ratio: 2.00 [95% confidence interval: 1.03 to 3.7]; p = 0.01). Conclusions In acute STEMI, platelet and fibrin contents of the occlusive thrombus are highly dependent on ischemia time, which may have a direct impact on the efficacy of drugs or devices used for coronary reperfusion. (J Am Coll Cardiol 2011;57:1359-67) (C) 2011 by the American College of Cardiology Foundation