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Background and Purpose: Markers of thrombin generation and platelet activation are often elevated in patients with nonvalvular atrial fibrillation, but it is unclear whether such markers usefully predict stroke. Therefore, we undertook the present study to assess the relationship between prothrombin fragment F1.2 (F1.2), beta-thromboglobulin (BTG), fibrinogen, and the factor V Leiden mutation with stroke in atrial fibrillation., Methods: Specimens were obtained from 1531 participants in the Stroke Prevention in Atrial Fibrillation III study. The results were correlated with patient features, antithrombotic therapy, and subsequent thromboembolism (ischemic stroke and systemic embolism) by multivariate analysis., Results: Increased F1.2 levels were associated with age (P<0.001), female sex (P<0.001), systolic blood pressure (P=0.006), and heart failure (P=0.001). F1.2 were not affected by aspirin use and were not associated with thromboembolism after adjustment for age (P=0. 18). BTG levels were higher with advanced age (P=0.006), coronary artery disease (P=0.05), carotid disease (P=0.005), and heart failure (P<0.001), lower in regular alcohol users (P=0.05), and not significantly associated with thromboembolism. Fibrinogen levels were not significantly related to thromboembolism but were associated with elevated BTG levels (P<0.001). The factor V Leiden mutation was not associated with thromboembolism (relative risk 0.5, 95% CI 0.1 to 3.8)., Conclusions: Elevated F1.2 levels were associated with clinical risk factors for stroke in atrial fibrillation, whereas increased BTG levels were linked to manifestations of atherosclerosis. In this large cohort of patients with atrial fibrillation who were receiving aspirin, F1.2, BTG, fibrinogen, and factor V Leiden were not independent, clinically useful predictors of stroke.

Fibrinogen participates in important cellular physiological processes, such as cell adhesion and blood clotting. Although the primary and secondary structures of fibrinogen are known, its tertiary structure is yet to be determined. In attempts to understand the tertiary structure of this important hydrated cellular and plasma membrane protein, the present study using atomic force microscopy was carried out. The techniques presented in this manuscript may also be applicable to enhance the imaging of live cells as well as their subcellular components. The authors have imaged fibrinogen by Tapping Mode atomic force microscopy in fluid. Purified human fibrinogen, together with 15-nm colloidal gold particles serving as an internal calibration standard, were adhered to a poly-L-lysine substrate on freshly cleaved mica. Atomic force microscopy images were obtained using oxide-sharpened silicon nitride probes, either unaltered or with an electron beam deposited extended tip. Although various structures were observed, the predominant forms consisted of a bi- or trinodular slightly curved linear shape. Approximately 300 of these structures were observed with six different tips (1 unaltered and 5 electron beam deposited) and their lengths and heights were analyzed. The mean length of the fibrinogen molecules was 65.8 nm and the mean height was 3.4 nm. The quantitative measurements were little influenced by the shape of the tip, whereas the sharper electron beam deposited tips seemed to produce qualitatively superior images.

Inflammation may play an important role in acute coronary syndromes. We studied the prognostic value of fibrinogen, an acute-phase protein directly involved in thrombotic process, measured serially in 1,473 patients with unstable angina and non-Q-wave myocardial infarction participating in the Thrombolysis in Myocardial Infarction IIIB trial. Overall, no association was found between baseline (pretreatment) fibrinogen and in-hospital (< or = 10 days) myocardial infarction (p=0.70) and death (p=0.64); however, patients with spontaneous ischemia (p=0.004) and the combined unsatisfactory outcome of death, myocardial infarction, and spontaneous ischemia (p=0.003) had higher fibrinogen concentrations than those without these events. This association was confined to patients with unstable angina. A baseline fibrinogen concentration > or = 300 mg/dl was associated with a modest trend toward an increased risk of death, myocardial infarction, or spontaneous ischemia (odds ratio 1.61, 95% confidence interval 1.02 to 2.52; p=0.04). Elevation of fibrinogen, a readily measurable acute-phase protein, at the time of hospital admission is associated with coronary ischemic events and a poor clinical outcome in patients with unstable angina.

No studies have examined the associations of coagulation factor levels with measures of subclinical cardiovascular disease (CVD) in the elderly. The Cardiovascular Health Study (CHS) is a prospective, population-based cohort study of CVD in persons older than 65 years. At the baseline examination, we measured fibrinogen, factor VII, and factor VIII levels in 5024 of the 5201 participants of the CHS and examined the associations of these coagulation factors with measures of subclinical CVD in a cross-sectional analysis. Subclinical CVD measures were based on electrocardiography, carotid ultrasonography, echocardiography, and ankle-arm blood pressure measurements (AAI). For analyses, we used the full cohort as well as two mutually exclusive subgroups: those with prevalent clinical CVD at baseline and those without. Fibrinogen and to a lesser extent factor VIII showed positive associations with a variety of subclinical CVD measures. In age-adjusted analyses, fibrinogen and factor VIII were significantly associated with 8 of 10 measures. In multivariate analyses, fibrinogen was significantly associated with carotid artery stenosis, internal (but not common) carotid artery wall thickness, and AAI. Factor VIII was associated with abnormal wall motion and AAI in the full cohort only. Factor VII was not consistently associated with subclinical disease measures. In bivariate analyses that included data from all three groups, there were 5 positive subclinical disease associations and 5 negative associations for factor VII. In multivariate analyses, there were no significant associations between factor VII and subclinical CVD in the full cohort or in either subgroup. We conclude that in these cross-sectional analyses, fibrinogen and to a lesser extent factor VIII are associated with subclinical CVD in the elderly, even in those without symptoms or a history of clinical CVD. Factor VII, however, was not associated with subclinical CVD in the elderly.

Plasma fibrinogen concentration is a risk factor for cardiovascular disease and has become a common component of epidemiologic studies. Also, fibrinogen analysis has become an important component of clinical trials of thrombolytic therapy and anticoagulation. We studied fibrinogen values from plasma containing three different anticoagulants and compared two different instruments. Clot-rate assays were performed on plasma containing sodium citrate (the recommended specimen) as well as ethylenediamine-tetraacetic acid (EDTA) and EDTA plus D-Phe-Pro-Arg chloromethyl ketone (PPACK) and aprotinin (special anticoagulant), specimens often obtained in multicenter studies. We compared a fibrometer (the BBL) with an analyzer (the Diagnostica Stago ST4), which offers improved throughput, ease of use, and precision. The correlation of citrate and EDTA fibrinogen values (fibrometer) was r = .9718; for citrate and special anticoagulant plasma, r = .9717. Correlations of fibrinogen values from the fibrometer and the analyzer were r = .9558 and r = .9857 for citrate samples and special anticoagulant samples, respectively. We conclude that (1) fibrinogen may be measured by clot-rate assay in EDTA-containing samples and that values may be compared with values obtained from citrate plasma with a correction; (2) samples containing PPACK may be used with only slight modification of the method; and (3) values obtained on the analyzer are directly comparable with those obtained on the fibrometer, facilitating large studies.

Plasma fibrinogen concentration appears to be an important risk factor for the development of atherosclerotic cardiovascular disease of a similar magnitude to cholesterol. The quality control of plasma fibrinogen assays has taken on new importance as a consequence of this potential role as an atherosclerotic risk factor. This article reviews the performance characteristics of 40,000 fibrinogen assays comprising the College of American Pathologists Proficiency Testing Program from 1988 through 1991. Instrument and reagent variables both play roles in the poor interlaboratory reproducibility documented by this study. The absence of either a national or international standard for plasma fibrinogen assays has been a major source of reagent variability. The validation and calibration of the College of American Pathologists lyophilized plasma reference preparation for fibrinogen determination is also reported in this study. The availability of this validated reference plasma should markedly improve interlaboratory reproducibility.

The Cardiovascular Health Study (CHS) was designed to examine cardiovascular disease and its risk factors in older adults. We report here the distributions of the coagulation factors fibrinogen, factor VII, and factor VIII in a population-based cohort of men and women 65 years or older. In other studies of middle-aged individuals, these factors were shown to be associated with cardiovascular risk. In the CHS cohort, all three factors were elevated, compared to levels reported in middle-aged individuals, and fibrinogen and factor VIII values were higher in each successive age group; factor VII values, in contrast, declined slightly with age in the CHS cohort. Compared to white subjects, blacks had higher values for fibrinogen and factor VIII and lower values for factor VII. While women had markedly higher values for factor VII and factor VIII than men at all ages in the CHS, mean fibrinogen values were not different between men and women.

The fibrinogen activity in thawed cryoprecipitate stored between 1 and 6 degrees C is maintained essentially unchanged in most bags for a month. Occasionally, a bag will have a reduction in fibrinogen. If pooling has not occurred, thawed cryoprecipitate should be useful as a source of fibrinogen for a period of time considerably in excess of the 6 hours allowed for its use as a source of factor VIII or von Willebrand factor.

Objectives: To assess the effects of invasive procedures, hemostatic and clinical variables, the timing of beta-blocker therapy, and the doses of recombinant plasminogen activator (rt-PA) on hemorrhagic events.Design: A multicenter, randomized, controlled trial.Setting: Hospitals participating in the Thrombolysis in Myocardial Infarction, Phase II trial (TIMI II).Interventions: Patients received rt-PA, heparin, and aspirin. The total dose of rt-PA was 150 mg for the first 520 patients and 100 mg for the remaining 2819 patients. Patients were randomly assigned to an invasive strategy (coronary arteriography with percutaneous angioplasty [if feasible] done routinely 18 to 48 hours after the start of thrombolytic therapy) or to a conservative strategy (coronary arteriography done for recurrent spontaneous or exercise-induced ischemia). Eligible patients were also randomly assigned to either immediate intravenous or deferred beta-blocker therapy.Measurements: Patients were monitored for hemorrhagic events during hospitalization.Main Results: In patients on the 100-mg rt-PA regimen, major and minor hemorrhagic events were more common among those assigned to the invasive than among those assigned to the conservative strategy (18.5% versus 12.8%, P less than 0.001). Major or minor hemorrhagic events were associated with the extent of fibrinogen breakdown, peak rt-PA levels, thrombocytopenia, prolongation of the activated partial thromboplastin time (APTT) to more than 90 seconds, weight of 70 kg or less, female gender, and physical signs of cardiac decompensation. Immediate intravenous beta-blocker therapy had no important effect on hemorrhagic events when compared with delayed beta-blocker therapy. Intracranial hemorrhages were more frequent among patients treated with the 150-mg rt-PA dose than with the 100-mg rt-PA dose (2.1% versus 0.5%, P less than 0.001). The extent of the plasmin-mediated hemostatic defect was also greater in patients receiving the 150-mg dose.Conclusions: Increased morbidity due to hemorrhagic complications is associated with an invasive management strategy in patients with acute myocardial infarction. Our findings show the complex interaction of several factors in the occurrence of hemorrhagic events during thrombolytic therapy. [ABSTRACT FROM AUTHOR]