Abstract 17580: Reduced Fibrin Clot Permeability During Acute Phase of Myocardial Infarction is Associated with Increased Area of Microvascular Obstruction
Background: The epicardial pro-thrombotic environment and myocardial edema are primary reasons of perfusion deterioration during acute phase of ST-segment elevation myocardial infarction (STEMI) but their independent influence on microvascular obstruction (MVO) remains poorly understood. We sought to investigate the quantitative impact of ex vivo measured fibrin clot properties and platelet reactivity on MVO territory during primary coronary intervention (PCI).
Methods and Results: Plasma clot permeability (Ks, µm2), which indicates a pore size and clot susceptibility to lysis in an assay using exogenous thrombin (t50%, min) were prospectively assessed in 108 STEMI patients on admission (ADM) and 4 months after PCI (M4). Platelet aggregation after stimulation with 5 µM of adenosine diphosphate (ADP5, %) and platelet-monocyte aggregates (PMA, %) were measured on admission (ADM) and 4 days (D4) after PCI. The MVO (% of infarct size) and infarct size (% of left ventricle mass) were determined by magnetic resonance imaging 2-4 days after STEMI. During acute phase of STEMI pore size of fibrin clot was lower by 26% (5.6 vs. 7.1 µm2, P<0.0001) and clot lysis time was longer by 20% (10.7 vs. 8.9 min, P<0.0001) as compared to follow-up measurements. The area of MVO was correlated with infarct size (r=0.67, P<0.0001), Ks-ADM (r=0.58, P<0.0001), TIMI epicardial blood flow after PCI (r=0.33, P=0.001) and PMA-D4 (r=0.28, P=0.019). All clinical variables that showed the association (p≤0.2) with the size of MVO in univariate model and were included in the multiple model, explained 68.3% of variance for MVO area. The strongest independent predictor of MVO territory was infarct size (r=0.5, 27.2% of variance, P<0.0001). Multiple regression showed also that Ks-ADM (r=-0.28, 15.5% of variance, P=0.0008), TIMI<3 after PCI (r=-0.23, 12.4% of variance, P=0.004), and PMA-D4 (r=0.19, 7.8% of variance, P=0.017) were independently associated with the MVO area.
Conclusions: During acute phase of STEMI patients tend to form dense fibrin clots resistant to lysis. Together with platelet-monocyte aggregates, altered plasma fibrin clot features contribute to the one fourth of microvascular obstruction territory however infarct size remains the strongest determinant of MVO area.
- © 2012 by American Heart Association, Inc.