Background-It has been suggested by clinical, epidemiological, and experimental in vitro studies that homocysteine potentiates thrombin generation. This prothrombotic effect however has not previously been demonstrated in patients presenting with acute coronary syndromes (ACS). Methods and Results-Patients with ACS (n ϭ117) presenting with confirmed acute myocardial infarction (MI) (n ϭ57) or unstable angina pectoris (UAP) (n ϭ60) were consecutively recruited together with patients (n ϭ18) in whom the presenting chest pain was not of cardiac origin (NCP), included as controls. Plasma samples were collected on admission and before clinical intervention. Homocysteine was assayed by high performance liquid chromatography, and both Factor VIIa and prothrombin fragment F1ϩ2 were analyzed by ELISA. There were significant elevations in F1ϩ2 in MI (PϽ0.001) and UAP (Pϭ0.003), and modest elevations in Factor VIIa in UAP (PϽ0.05) compared with NCP but no differences in homocysteine levels among those groups. On dividing patients with ACS into quartiles of homocysteine, there was a stepwise increase in F1ϩ2 (PϽ0.0001) and of Factor VIIa (PϽ0.05). There were significant correlations in ACS between homocysteine and F1ϩ2 (rϭ0.46, PϽ0.0001), homocysteine and Factor VIIa (rϭ0.24, PϽ0.01), and F1ϩ2 and Factor VIIa (rϭ0.41, PϽ0.0001). There was no correlation between homocysteine and either F1ϩ2 (rϭϪ0.15, Pϭ0.57) or Factor VIIa (rϭ0.22, Pϭ0.37) in the NCP patients. Conclusions-Elevated plasma homocysteine is associated with and may cause elevated Factor VIIa and thrombin generation in patients presenting with ACS. These findings suggest an explanation for the prothrombotic effect of homocysteine in ACS.
SummaryThere is growing evidence that the tissue factor/factor VIIa pathway of coagulation is enhanced during cardiopulmonary bypass. Hitherto, available evidence has suggested that upregulated monocyte bound tissue factor is made available, either in the blood collected from the site of surgery or on circulating cells. However, cellular upregulation is slow, while generation of factor VIIa in blood collected from the pericardial cavity is rapid. We have therefore investigated the possibility of an alternative source of tissue factor, plasma (as opposed to cellular) tissue factor in blood samples taken from the central vein catheter (systemic circulation) and collected from the pericardial cavity during cardiopulmonary bypass. Six patients undergoing first time cardiopulmonary bypass grafting were studied. Tissue factor antigen was found to be rapidly elevated (by 15 min) in the pericardial plasma, ∼5-fold above systemic levels (p <0.004). Similar elevations were found in markers of coagulation activation, factor VIIa antigen (p = 0.066), prothrombin fragment F1+2 (p <0.003) and thrombin-antithrombin complex (p <0.03). To explore whether plasma tissue factor was (or had been) functionally active, factor VIIa was measured also with the soluble tissue factor functional assay after removal of heparin. Functional factor VIIa activity fell significantly in the systemic circulation, probably due to the heparin-induced increase (∼15-fold) in tissue factor pathway inhibitor (TFPI), but was elevated in pericardial blood compared with that taken from the central line catheter (p <0.006). These results demonstrate that both components of the activation complex for the extrinsic pathway of coagulation are rapidly generated in pericardial blood during bypass.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.