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Increased levels of tissue factor-bearing microparticles in patients with premature myocardial infarction

      Previously we have shown that the plasma of patients with a premature myocardial infarction (PMI)<50 years had significantly higher endogenous thrombotic potential (ETP) and tissue factor (TF) than matched controls. Here we sought to determine whether the higher level of TF in PMI patients was predominantly in the form of microparticles (MPs). Plasma from 168 individuals with an MI<50 years and 168 age/sex-matched controls with no history of CHD was analysed for thrombin generation by the Calibrated Automated Thrombogram (CAT) assay using 4μM PL reagent (Stago MP reagent; designed to measure TF+ve MPs). Plasma from 160 of the patients and controls were also analysed after passing through a 0.22μm filter to remove MPs. The CAT assay showed the lag time (LT) and time to peak (ttP) were shorter in the patients (32.9±1.57mins vs 41.5±1.72mins; p=0.0002 and 35.4±1.49mins vs 43.8±1.60mins; p=0.0001 respectively), indicative of higher TF+ve levels in the patients’ samples. The ETP and peak thrombin (PT) levels were also higher in the patients (985±49nM vs 661±45nM; p<0.0001; and 161.8±9.0nM vs 99.2±7.6nM; p<0.0001 respectively). Filtration caused an increase in LT and ttP and removed the difference between the patients and the controls (for LT 41.4±1.92mins vs 45.4±1.90mins; p=0.1357 and for ttP 43.1±1.81mins vs 47.0±1.81mins; p=0.1206). Filtration also deceased ETP and PT slightly for both groups (for ETP 757±54nM vs 576±49nM-; p=0.0136 and for PT 135.6±10.6nM vs 98.1±9.2nM; p=0.0077). These data are consistent with a higher level of TF+ve MPs in the plasma of PMI patients, potentially originating from atherosclerotic plaques.
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