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Objectives: We sought to assess the effects of antithrombotic therapy after thrombolysis for acute myocardial infarction on markers of thrombin generation and activity and to determine the relation of these markers with clinical outcomes., Background: Thrombin activation and generation often occur with thrombolysis for acute myocardial infarction. Antithrombotic regimens have been developed to reduce the resulting thrombotic complications., Methods: We sampled plasma markers of thrombin generation and activity after thrombolysis in 292 patients. We assessed the relations of these markers with clinical outcomes at 30 days., Results: Fibrinopeptide A (FPA), a marker of thrombin activity toward fibrinogen, was elevated at baseline (12.3 ng/ml) and increased to 18.4 ng/ml by 90 min after streptokinase and subcutaneous heparin treatment. With intravenous heparin, this increase was attenuated, but intravenous heparin did not prevent thrombin generation, as measured by prothrombin fragment 1.2 (F1.2). Heparin level, measured by anti-Xa activity, correlated with activated partial thromboplastin time (aPTT, r = 0.62 to 0.67). Thrombin activity, measured by FPA, was as closely related to aPTT as to the heparin level. Baseline levels of F1.2 were significantly related to the risk of death or reinfarction at 30 days (p = 0.008); values 12 h after enrollment also were related to 30-day mortality (p = 0.05)., Conclusions: Although intravenous heparin partly suppresses the increased thrombin activity associated with thrombolysis, it does not inhibit thrombin generation. The aPTT was as good a measure of suppression of thrombin activity as the heparin level itself. Hematologic markers of thrombin generation were found to be related to the subsequent risk of thrombotic events.

The major conclusions of this position article are as follows: (1) In the absence of a history of a bleeding disorder, the bleeding time is not a useful predictor of the risk of hemorrhage associated with surgical procedures. (2) A normal bleeding time does not exclude the possibility of excessive hemorrhage associated with invasive procedures. (3) The bleeding time cannot be used to reliably identify patients who may have recently ingested aspirin or nonsteroidal anti-inflammatory agents or those who have a platelet defect attributable to these drugs. The best preoperative screen to predict bleeding continues to be a carefully conducted clinical history that includes family and previous dental, obstetric, surgical, traumatic injury, transfusion, and drug histories. A history suggesting a possible bleeding disorder may require further evaluation; such an evaluation may include performance of the bleeding time test, as well as a determination of the platelet count, the prothrombin time, and the activated partial thromboplastin time. In the absence of a history of excessive bleeding, the bleeding time fails as a screening test and is, therefore, not indicated as a routine preoperative test.

Current protocols for use of tissue-type plasminogen activator in acute myocardial infarction include heparin estimated by the activated partial thromboplastin time (aPTT). Recent reports indicate a risk of recurrent ischemic events with long aPTT values. Longer aPTT values in the Thrombolysis in Myocardial Infarction-II (TIMI II) Trial, obtained within the first 48 hours, were associated with patency at 18 to 48 hours and better left ventricular function at discharge (average 9.6 days), but also with emergency catheterizations within the first 48 hours and, weakly, with recurrent ischemia during the first 18 hours. A moderate decrease in fibrinogen, compared with a "small" decrease, was also associated with patency, but a "large" decrease was associated with hemorrhagic events. Patency was associated with higher fibrinogen values and higher plasminogen values at baseline. The aPTT results support frequent monitoring during the first 24 to 48 hours to ensure optimal clinical outcome. The coagulation factor results suggest that there may be an optimum window for fibrinogenolysis in this setting.

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.

Blood levels of C-reactive protein (CRP), a marker of inflammation, are related to cardiovascular disease risk. To determine cross-sectional correlates in the elderly, we measured CRP in 400 men and women older than 65 years and free of clinical cardiovascular disease at baseline as part of the Cardiovascular Health Study. Only 2% of the values were greater than 10 mg/L, the cut-point usually used to identify inflammation. CRP levels appeared tightly regulated, since there were strong bivariate correlations between CRP and the following: inflammation-sensitive proteins such as fibrinogen (r = .52); measures of fibrinolysis such as plasmin-antiplasmin complex (r = .23); pack-years of smoking (r = .30); and body mass index (r = .24; all P values < or = .001). The association with pack-years was independent of the length of time since cessation of smoking. CRP levels were also associated with coagulation factors VIIc, IXc, and Xc; HDL cholesterol (negative) and triglyceride; diabetes status; diuretic use; ECG abnormalities; and level of exercise. Because of effect modification, two multiple linear regression prediction models were developed for CRP, one each for never smokers and ever smokers. An a priori physiologic model was used to guide these analyses, which disallowed the use of other inflammation-sensitive variables such as fibrinogen. In never smokers, the independent predictors were body mass index (+), diabetes status (+), plasmin-antiplasmin complex (+), and the presence of ECG abnormalities (+); this model predicted 15% of the CRP population variance. In ever smokers, the predictors were body mass index (+), plasmin-antiplasmin complex (+), pack-years of smoking (+), HDL cholesterol (-), and ankle-arm blood pressure index (-); this model predicted 42% of the population variance. We conclude that levels of CRP in the healthy elderly are tightly regulated and reflect lifetime exposure to smoking as well as level of obesity, ongoing level of fibrinolysis, diabetes status, and level of subclinical atherothrombotic disease. Moreover, exposure to smoking affects the relation of CRP to these other factors.

Objectives: We sought to determine the extent of Factor V proteolysis during thrombolytic therapy., Background: Thrombin- or Factor Xa-activated Factor V is an essential cofactor in the prothrombinase complex. In purified systems, plasmin, the major product of thrombolytic therapy, is known to first activate then inactivate Factor V., Methods: We used quantitative gel electrophoresis and Western blotting to analyze the cleavages in plasma Factor V after thrombolytic therapy., Results: The addition of streptokinase to plasma resulted in the activation then inactivation of Factor V, confirming previous results using purified reagents. We also identified the Factor V fragments resulting from the action of thrombin and plasmin. After thrombolytic therapy, there was considerable Factor V cleavage. The cleavage patterns were consistent with the action of plasmin, with little evidence for the action of thrombin. In the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries trial (n = 17), we observed an average 58% loss of intact Factor V at 6 h (range 1% to 91%). Samples from the Thrombolysis in Myocardial Infarction trial, Phase II (n = 12), collected on a shorter time scale, showed a loss of up to 99% at 50 min, with the loss of intact Factor V associated with the plasma concentration of plasminogen activator. Samples from patients with bleeding (n = 12) showed extensive Factor V cleavage., Conclusions: Factor V cleavage in thrombolytic therapy is primarily plasmin mediated, rapid and often extensive. It is likely that transient increases, as well as longer term losses, of Factor V cofactor activity play a role in both ischemic and hemorrhagic events subsequent to thrombolytic therapy. The extensive loss of Factor V in some patients may affect the estimation of heparinization.

Case reports cited in Medline or Biological Abstracts (1966-1996) were reviewed to evaluate the impact of vitamin K1 dietary intake on the stability of anticoagulant control in patients using coumarin derivatives. Reported nutrient-drug interactions cannot always be explained by the vitamin K1 content of the food items. However, metabolic data indicate that a consistent dietary intake of vitamin K is important to attain a daily equilibrium in vitamin K status. We report a diet that provides a stable intake of vitamin K1 equivalent to the current U.S. Recommended Dietary Allowance, using food composition data derived from high-performance liquid chromatography. Inconsistencies in the published literature indicate that prospective clinical studies should be undertaken to clarify the putative dietary vitamin K1-coumarin interaction. The dietary guidelines reported here may be used in such studies.

This study assesses the effects of invasive procedures, hemostatic and clinical variables, and doses of recombinant tissue plasminogen activator (t-PA) on hemorrhagic events in the thrombolysis in myocardial ischemia (TIMI), phase 1B clinical trial (n = 1,425). Patients seen within 24 hours of the onset of ischemic chest pain at rest were randomized using a 2 x 2 factorial design for comparison of: (1) t-PA versus placebo as initial therapy, and (2) an early invasive (coronary arteriography with percutaneous angioplasty, if feasible) versus an early conservative strategy (coronary arteriography followed by revascularization if initial medical therapy failed). All patients received conventional medication for acute ischemic syndromes, including heparin, aspirin, beta blockers, nitrates, and calcium antagonists. The total dose of t-PA or placebo was 0.8 mg/kg, up to a maximum dose of 80 mg. In patients treated with t-PA, major and minor hemorrhagic events were more common than among those assigned to placebo (p < 0.001). Patients assigned to the invasive strategy arm had a higher hemorrhagic event rate than the noninvasive strategy, although the difference was not significant (p = 0.026). Patients > 75 years of age had higher intracranial hemorrhage rates than those < 75 years of age (6.7% vs 0.2%, respectively, p = 0.01). Major hemorrhagic events were more common in patients with higher heparin levels (p < 0.001), higher peak D-dimer levels (p = 0.007), and lower nadir fibrinogen levels (p = 0.005). Thus, increased morbidity due to hemorrhagic complications is associated with the use of t-PA, increased age, and selected hemostatic measures. Comparison to TIMI II demonstrates a significant association between the dose of t-PA and hemorrhagic complications.

Studies suggest that thrombosis is important in the progression of atherosclerotic lesions. The biochemical markers prothrombin fragment 1-2 and fibrinopeptide A reflect in vivo thrombin generation and activity, respectively. As such, they are markers that might be associated with cardiovascular risk. From the Cardiovascular Health Study, a cohort study of 5201 persons over 65 years of age, 399 persons free of clinical cardiovascular disease (CVD) at the baseline examination were selected for study of specialized markers of hemostasis. We report the cross-sectional relationships of the thrombin markers to CVD risk factors and measures of subclinical CVD. The range of fragment 1-2 2 was 0.12 to 0.85 nmol/L. The range of fibrinopeptide A was 0.9 to 44.1 micrograms/L. High levels of fragment 1-2 and fibrinopeptide A were associated with age, with levels higher in women than men. Fragment 1-2 was associated with smoking; high levels of triglyceride, creatinine, and C-reactive protein; and low levels of glucose. Fibrinopeptide A was associated with high C-reactive protein and apolipoprotein(a) and lower ankle-brachial index. There were no significant associations of the thrombin markers with race, fibrinogen, alcohol consumption, diabetes, or most measures of subclinical CVD. Study findings support a hypothesis that there are physiological interrelationships between cardiac risk factors, hemostasis, inflammation, and progression of atherosclerosis.

A higher white blood cell (WBC) count has been shown to be a risk factor for myocardial infarction and stroke in middle-aged populations. This study evaluated the relation between baseline WBC count and other risk factors, as well as subclinical and prevalent disease, in the Cardiovascular Health Study, an epidemiologic study of coronary heart disease and stroke in 5,201 persons aged 65 years or older. Baseline data were collected over a 12-month period in 1989-1990. WBC counts were statistically significantly higher in people with prevalent and subclinical atherosclerotic cardiovascular disease than in those who were free of disease. WBC counts correlated (p < 0.01) positively with coagulation factors, measures of glucose metabolism, creatinine, smoking, and triglycerides. In contrast, WBC counts correlated negatively with high density lipoprotein cholesterol, forced expiratory volume, forced vital capacity, and height. The correlations between WBC counts and risk factors were similar in both the entire cohort and the subgroup of persons who had never smoked. The authors conclude that WBC counts in the elderly are associated with prevalent and subclinical atherosclerotic cardiovascular disease, as well as its risk factors.

Percutaneous coronary revascularization in patients with unstable angina and coronary thrombus carries a high complication rate. A new strategy to reduce thrombus burden before revascularization was tested in a multicenter prospective trial. Patients with unstable angina and coronary thrombus (n = 45) received alteplase through an infusion catheter at the proximal aspect of the target lesion and concomitant intracoronary heparin via a standard guiding catheter. Angiography was performed before and alter lesion-directed therapy and post-intervention. Systemic fibrinogen depletion and thrombin activation were not observed, while fibrinolysis was evident for > or = 4 hr after treatment. Target lesion stenosis did not change significantly after lesion-directed therapy, but thrombus score was reduced, particularly among patients who had large thrombi (mean 2.2 vs. 1.6, P = 0.02). Revascularization was successful in 89% of patients. Median final stenosis was 30% and mean final thrombus score was 0.4. Complications included recurrent ischemia (11%), MI (7%), abrupt closure (7%), severe bleeding (4%), and repeat emergency angioplasty (2%). Patients with overt thrombus appeared to derive the most angiographic benefit from lesion-directed alteplase plus intracoronary heparin. Later revascularization was highly successful. This strategy may be a useful adjunct to percutaneous revascularization for patients with unstable angina and frank intracoronary thrombus.

Measures of markers of in vivo activation of coagulation were assessed in patients on stable long-term oral anticoagulant therapy and analyzed with respect to the International Normalized Ratio (INR). The range of F1+2, FPA, and antithrombin--enzyme complex results (ATM) were significantly lower as compared to normals. Plasmin-antiplasmin complexes were unaffected by anticoagulation. An inverse correlation was evident between F1+2, FPA, and INR values at low intensity anticoagulation, and FPA and complexed antithrombin were correlated at high INRs. The relative ratio of plasma FPA/F1+2 and ATM/F1+2 increased with increasing INR. In conclusion, the interrelationship of these measures changes with intensity of anticoagulation as measured by INR, and appears complex. The utility of using these measures for patient monitoring awaits future clinical trials.

Background: Although intravenous heparin is commonly used after thrombolytic therapy, few reports have addressed the relationship between the degree of anticoagulation and clinical outcomes. We examined the activated partial thromboplastin time (aPTT) in 29,656 patients in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-I) trial and analyzed the relationship between the aPTT and both baseline patient characteristics and clinical outcomes., Methods and Results: Intravenous heparin was administered as a 5000-U bolus followed by an initial infusion of 1000 U/h, with dose adjustment to achieve a target aPTT of 60 to 85 seconds. aPTTs were collected 6, 12, and 24 hours after thrombolytic administration. Higher aPTT at 24 hours was strongly related to lower patient weight (P < .00001) as well as older age, female sex, and lack of cigarette smoking (all PT< .0001). At 12 hours, the aPTT associated with the lowest 30-day mortality, stroke, and bleeding rates was 50 to 70 seconds. There was an unexpected direct relationship between the aPTT and the risk of subsequent reinfarction. There was a clustering of reinfarction in the first 10 hours after discontinuation of intravenous heparin., Conclusions: Although the relationship between aPTT and clinical outcome was confounded to some degree by the influence of baseline prognostic characteristics, aPTTs higher than 70 seconds were found to be associated with higher likelihood of mortality, stroke, bleeding, and reinfarction. These findings suggest that until proven otherwise, we should consider the aPTT range of 50 to 70 seconds as optimal with intravenous heparin after thrombolytic therapy.

Although coronary thrombosis is thought to play a pivotal role in the pathogenesis of unstable angina and non-Q wave myocardial infarction and antithrombotic therapy is a mainstay in the early management of these patients, the relation between measures of systemic anticoagulation and clinical events has not been defined clearly. In the Thrombolysis in Myocardial Ischemia III trial, 1473 patients with ischemic chest pain at rest evaluated within 24 hours of symptom onset were randomized to (1) tissue plasminogen activator (TPA) or placebo and (2) an early invasive or an early conservative strategy. All patients received a full complement of anti-ischemic medication, aspirin, and continuous intravenous heparin titrated to an activated partial thromboplastin time (aPTT) of 1.5 to 2.0 times control for 72 to 96 hours. The median aPTT in all study groups exceeded the minimum threshold (45 seconds) by 24 hours and remained within the designated range during the protocol-directed heparin infusion. No differences in median aPTT values for the 72- to 96-hour study period were observed between groups (p=not significant). Median 12-hour heparin concentrations were >0.2 U/ml in all groups; however, values <0.2 U/ml were common thereafter, particularly in TPA-treated patients. Time-dependent covariate analyses failed to identify statistically significant differences in either aPTT or heparin levels between patients with in-hospital clinical events (spontaneous ischemia, myocardial infarction, or death) and those without events (p=0.27). Furthermore, early clinical events occurred in a similar percentage of patients with optimal anticoagulation (all aPTTs >60 seconds, all heparin levels>0.2 U/ml), and those with aPTTs or heparin levels below these thresholds. Aggressive (high-intensity) anticoagulation with heparin to achieve aPTTs >2.0 times control does not appear to offer additional clinical benefit to lower levels (1.5 to 2.0 times control) among patients with unstable angina and non-Q wave myocardial infarction receiving intravenous heparin and oral aspirin. Therefore, the optimal level of anticoagulation in this common clinical setting is between 45 and 60 seconds when heparin is included in the treatment strategy. Direct plasma heparin measurement does not offer an advantage to routine aPTT monitoring. The occurrence of spontaneous ischemia, myocardial infarction, and death in spite of antischemic therapy and optimal anticoagulation (as it is currently defined) with heparin supports ongoing efforts to develop more effective antithrombotic agents.

Clinical and biochemical evidence of a rebound phenomenon after discontinuing thrombin inhibitors has been reported in patients with unstable angina. To investigate if a similar phenomenon occurs in patients undergoing coronary angioplasty, 14 patients were prospectively studied during and after discontinuation of heparin infusion. A transient thrombotic state identified by a significant increase in a polypeptide fragment and fibrinopeptide A was observed 3 hours after abruptly discontinuing heparin infusion. This observation may be clinically important in managing patients after coronary angioplasty.

A unique blood coagulation factor X variant has been identified in a family with a history of bleeding. Plasma from affected family members had prolonged prothrombin times and activated partial thromboplastin times, low to below normal factor X coagulant activity, and normal factor X antigen levels. Sequencing of DNA from the propositus revealed a single G to A substitution in one allele of factor X at base 964 resulting in an amino acid substitution of Asn for Asp at residue 282. This residue corresponds with the active site Asp102 of chymotrypsin. The substitution eliminates a TaqI restriction site and provided the basis for a screening assay to detect the mutation in polymerase chain reaction (PCR) amplified factor X exon VIII DNA. Fourteen additional family members were identified as having the mutation at base 964. Plasma factor X purified from the proposita using an anti-factor X monoclonal antibody immunoadsorbent exhibited an approximately 50% decrease in specific activity compared with factor X purified from a normal individual in a similar manner. Bleeding in family members with the mutation, termed factor X Stockton, appears to be due to disruption of normal hemostasis by the presence in plasma of circulating abnormal factor X. Factor X Stockton is the first naturally occurring substitution at the active site Asp of a serine protease and underscores the importance of this amino acid residue in factor Xa coagulant activity.

Prenatal maternal vitamin K1 supplementation to improve the hemostatic status of the fetus may depend upon the route of administration and subsequent presentation at the placental barrier. We investigated intramuscular (IM) vs oral (PO) vitamin K1 supplementation in eight healthy, nonpregnant women of childbearing age. Pharmacokinetics were studied in each subject after a 5 mg IM dose and after a 5 mg oral dose of vitamin K1 approximately one month later. Plasma collected at the peak vitamin K level for each treatment was separated into very low density lipoproteins (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL) and lipoprotein-free fractions by density gradient ultracentrifugation. Vitamin K1 was measured in the plasma and lipoprotein fractions using HPLC. The concentration of vitamin K1 in plasma reached a peak 2 h after an IM dose and remained high throughout the 30 h course of the study. In contrast, the oral dose of vitamin K1 peaked at 4 h and rapidly decreased to near baseline by 18 to 30 h. The distribution of vitamin K1 in the lipid fractions was different for IM compared to PO. The percentage of vitamin K1 in the VLDL fraction at the peak for an oral dose was significantly higher than for an IM dose (80.8% +/- 3.5 vs 10.8% +/- 6.5, p < 0.0001). After the oral absorption stage, the subjects took 5 mg of vitamin K1 orally, once a day, for 12 days. No significant differences were observed for the following coagulation proteins and hemostatic markers measured immediately before and after long-term oral vitamin K supplementation: factor II, factor VII, protein C, and thrombin-antithrombin III complex. In conclusion, physiological processing of supplemented vitamin K1 differs in the IM vs PO routes of administration and 12 days of oral vitamin K1 does not alter the concentration of selected vitamin K-dependent coagulation proteins or thrombin-antithrombin complex generation.

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.

Meizothrombin is an intermediate that is produced during the conversion of prothrombin to thrombin in systems composed of purified factor Xa and factor Va that are quantitatively assembled on an anionic phospholipid surface. The biological significance of this intermediate has recently been challenged by the apparent absence of meizothrombin during clotting of sodium citrate-anticoagulated plasma. We analyzed the formation of thrombin during coagulation of nonanticoagulated, unchilled, minimally manipulated whole blood in glass tubes. The process was stopped at 0, 3, 5, and 7 minutes by the addition of biotinylated peptidyl chloromethyl-ketone active-site labeling reagents. Plasma/serum was separated by centrifugation, and labeled species were extracted by immunoadsorption with a polyclonal anti-prothrombin antibody. The purified prothrombin-derived species were separated by SDS-polyacrylamide gradient gel electrophoresis and visualized on a chemiluminescent avidin blot. Meizothrombin appeared as an intermediate product of this reaction and persisted with some increase through the 7-minute time point. We also observed incorporation of the active-site label into a species of lower molecular weight consistent with the B1 chain of beta- and/or gamma-thrombin. These degraded forms of thrombin have not been previously demonstrated in a biologically relevant preparation. Our data clearly establish the generation of meizothrombin as an intermediate product of thrombin generation during whole-blood clotting. The data also represent the first experimental evidence for the generation of beta- and gamma-thrombin in a biologically relevant environment and time scale.

Background: The abrupt cessation of heparin and other thrombin inhibitors when used to treat acute coronary syndromes has been accompanied by a clustering of thrombotic events. It is unknown whether these events are the result of inadequate antithrombin therapy or whether they represent a rebound increase in thrombin activity. This study was designed to determine whether there is a true rebound, as defined by an increase followed by a subsequent decrease, in thrombin activity after discontinuation of intravenous heparin therapy., Methods and Results: Thirty-five patients with recent acute myocardial infarction or unstable angina who had received at least 48 hours of intravenous heparin were studied. Patients underwent ST-segment monitoring, and blood samples for determination of thrombin generation and activity were drawn at 0, 3, 6, 10, and 24 hours after heparin discontinuation. Median aPTT was 65 seconds before heparin discontinuation. Median fibrinopeptide A increased from 9.5 to 16.9 ng/mL at 3 hours (P < .0004) and returned to 10.5 by 24 hours. Prothrombin fragment 1.2 likewise transiently increased, from 0.34 to 0.51 nmol/L at 6 hours (P < .0002). Modified antithrombin III decreased over time (P < .002), and activated protein C increased from 2.3 to 4.5 ng/mL at 3 hours (P < .001). Although there were no clinical thrombotic events in the first 24 hours, 4 patients had evidence of ischemia by ST-segment monitoring at a median of 12 hours after heparin discontinuation. The degree of increase in fibrinopeptide A and prothrombin fragment 1.2 was not found to be associated with baseline diagnosis, duration of heparin therapy, baseline level of antithrombin III, or activated protein C., Conclusions: This study demonstrates a transient rebound increase in thrombin activity as well as in activated protein C upon abrupt discontinuation of intravenous heparin. Clinicians should be vigilant for associated thrombotic events. Further investigation of the significance, mechanism, and possible prevention of this rebound phenomenon is needed.

The Cardiovascular Health Study is an observational cohort study of risk factors for cardiovascular disease in 5201 participants, ages > or = 65 years. We report the methods and quality-assurance results for blood procurement, processing, shipping, storage, and sample analysis used during the first examination period (May 1989-June 1990). The most frequent difficulty in phlebotomy and processing was the requirement of more than one venipuncture (in 2.6% of the participants). The CVs for control materials ranged from 0.93% for glucose to 10.7% for insulin; most were < 4%. In addition to standard quality-assurance methods, we applied two other methods: technical error calculation for replicates, and weighted linear regression to assess time trend in results of control materials. After outliers were excluded, technical error values ranged from 1.7 for uric acid to 18.8 for insulin. Factor VII and factor VIII had slight trends over the 12-month analysis period. Results of quality-assurance analyses used to resolve problems were successful, thereby improving the second laboratory examination.

The role of two protein C gamma-carboxyglutamic acid domain mutations in familial thrombosis, protein CVermont (Bovill, E. G., Tomczak, J. A., Grant, B., Bhushan, F., Pillemer, E., Rainville, I.R., and Long, G. L. (1992) Blood 79, 1456-1465), was investigated. Two single mutations (Glu20-->Ala and Val34-->Met) and the naturally occurring double mutation were created by site-directed mutagenesis and were expressed in human kidney 293 cells. Purified recombinant protein C with the mutation glutamate to alanine at position 20 is defective in the assays of activated partial thromboplastin time, factor Va inactivation, and fibrinolysis. Mutation from valine to methionine at position 34 has only a minor effect. Activation of Glu20 mutants by thrombin-thrombomodulin was not enhanced by phospholipid vesicles and showed a different calcium dependence compared with the wild type, suggesting that Gla20 is important in the interaction of the protein C Gla domain with a phospholipid-mediated site on the thrombomodulin molecule. Glu20-substituted protein C is not inhibited by calcium ion in its interaction with the calcium-dependent monoclonal antibody H-11, suggesting that this mutation has lost the calcium-induced, lipid-independent conformational transition of the protein C Gla domain. These data indicate that the loss of Gla20 causes the major familial dysfunction of protein C to associate with phospholipid as well as to undergo Ca(2+)-dependent, lipid-independent conformational changes and are consistent with the importance of Gla20 in both external and internal Ca2+ binding based upon the x-ray-derived structure of the homologous Gla domain in bovine prothrombin.

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.

We determined factor VII antigen (FVIIag) levels in 705 healthy blood donors ranging in age from 17 to 79 years using a two-site solid-phase enzyme immunoassay developed in our laboratory. The mean (+/- SD) FVIIag level for the total population was 102 +/- 31%. FVIIag levels for men (n = 375) and women (n = 330) were 101 +/- 28% and 103 +/- 33%, respectively. A significant increase in FVIIag was observed with age in both men (r = 0.25, p < 0.0001) and women (r = 0.35, p < 0.0001). FVIIag levels were significantly higher in women > 60 years when compared to men (median women: 125%; median men: 111%; p < 0.05). On a subset of the study group (n = 45), FVIIag levels were correlated to total cholesterol (r = 0.27, p = 0.08) and triglyceride (r = 0.41, p < 0.01). Assuming the commonly used reference interval of 60-140% for FVII, the frequencies of FVIIag values for < 60% and > 140% using our assay were 2.1% and 9.2%, respectively. Gender and age-related differences in FVIIag levels must be considered in a reference interval. We further suggest that assay-specific reference ranges be established, which may include values outside the commonly used values of 60-140%.

Background: Unstable angina signals a sudden transition from stable to unstable atherosclerotic coronary artery disease. Although assessment of platelet activity has been shown to provide diagnostic and prognostic information, most available methods lack sufficient sensitivity or specificity for them to be useful in clinical practice. In recent years, fluorescently labeled antibodies and flow cytometry have permitted the detection of activation proteins on individual platelets. The purpose of the present study was to assess the ability of flow cytometry to detect platelet activation in patients with unstable angina and non-Q-wave myocardial infarction., Methods: Platelet activation before treatment was determined from whole-blood samples in 19 patients participating in the Thrombolysis in Myocardial Ischemia (TIMI)-IIIB study and in nine healthy volunteers (total of 24 samples) using flow cytometry and a monoclonal antibody (clone 1E3) to the activation-dependent, surface-expressed protein P-Selectin., Results: Among healthy volunteers, a small percentage of platelets were activated (2.0 +/- 2.5%). In contrast, 15 out of 19 (79%) patients with suspected myocardial ischemia at rest had 10.4 +/- 11.1% activated platelets (95% confidence interval 4.9-15.9%; P < 0.01). Seven patients (37%) were found to have more than 10% activated platelets. The degree of platelet activation did not differ significantly between patients with unstable angina and those with elevated creatine kinase levels (non-Q-wave myocardial infarction)., Conclusion: Whole-blood flow cytometric techniques can minimize the artifactual platelet activation often seen with other techniques and therefore offer distinct advantages in the investigation of patients with thrombotic coronary syndromes. In TIMI-III, patients with unstable angina and non-Q-wave myocardial infarction had clear evidence of platelet activation. An ongoing study will examine the correlation between platelet activation assessed using flow cytometry and clinical events in a larger patient cohort.

Objective: To describe relationships between age and sub-clinical cardiovascular disease, manifest chronic disease, and physical functioning and limitations among persons aged 65 years and older, with emphasis on the "oldest old," those 85 years and older., Design: Observational population-based study., Setting: Four U.S. communities: Forsyth County, North Carolina; Sacramento County, California; Washington County, Maryland; and Pittsburgh, Pennsylvania., Participants: 5,201 men and women aged 65 years and older., Measurements: Demographic data; histories of cardiovascular disease (CVD), chronic lung disease, arthritis, diabetes, and hypertension; measures of subclinical disease including arm and ankle blood pressures, internal carotid wall thickness and stenosis, ejection fraction, left ventricular mass, fractional shortening, and diastolic function, electrocardiographic left ventricular hypertrophy and cardiac injury score, forced expiratory flow and volume; functional status including self-reported physical functioning, hearing and sight limitations and health status, and performance-based measures of function. These variables were examined among men and women in three age groups: 65-74 years, 75-84 years, and 85 + years. Subgroups of participants with and without manifest CVD were also examined., Main Results: In women, the prevalence of CVD and other chronic conditions increased with age, and the highest rates occurred among those 85 years and older. In men, prevalence rates increased between the two younger groups, but the oldest group had lower than expected rates for coronary heart disease, cerebrovascular disease, hypertension, and chronic lung disease. In contrast, there were strong age-related linear trends in most of the subclinical measures of blood pressure, atherosclerosis and pulmonary function and in virtually all measures of functional status in both gender groups across the age range. There was a particularly marked decline in functional status between the two older age groups. While subclinical disease was greater and functional status was poorer among those with manifest CVD, with few exceptions, age-related trends were not significantly different between the two groups., Conclusions: Lower than expected prevalence rates of CVD among those aged 85 years and older, particularly among men, in this study of community-dwelling elderly may represent selection bias or a real plateauing in disease prevalence with age. However, subclinical disease appears to increase and functional status to decline across the age range in both men and women regardless of the presence of CVD. The apparent increase in subclinical disease with age indicates potential for CVD prevention after age 65.

Background: To better understand the role of race/ethnicity in survival after acute myocardial infarction, we compared clinical and laboratory data, response to thrombolytic therapy, and clinical outcome in 2885 patients participating in the Thrombolysis in Myocardial Infarction Phase II (TIMI II) Trial among three groups of patients (2564 whites, 174 blacks, and 147 Hispanics)., Methods and Results: Differences were found in baseline characteristics among the three groups including (1) age (mean age for whites, 57.2 years; blacks, 54.8 years; Hispanics, 52.8 years; P < .001), (2) sex (percentage of women for whites, 17.6; blacks, 28.7; Hispanics, 14.3; P < .001), and (3) risk factor prevalence: current smoking (percent for whites, 49.4; blacks, 62.1; Hispanics, 55.1; P < .003), history of hypertension (percent for whites, 36.6; blacks, 55.7; Hispanics, 39.5; P < .001), and diabetes mellitus (percent for whites, 11.9; blacks, 22.4; Hispanics, 19.7; P < .001). Changes in hemostatic factors 5 hours after infusion of recombinant tissue plasminogen activator (rt-PA) revealed a more profound fall in fibrinogen levels in black patients compared with the response seen in Hispanic or white patients (mean change in fibrinogen +/- SD, mg/dL: 151.3 +/- 107.4, 112.2 +/- 97.0, 109.4 +/- 98.6; P < .001, respectively) without more frequent infarct-related artery patency or hemorrhagic complications. Mortality was similar in the white, black, and Hispanic patients through the first year after adjustment for baseline variables., Conclusions: TIMI II data yield evidence that (1) corroborates published reports of a high prevalence of classic cardiovascular risk factors among minority patients with acute myocardial infarction, (2) there is a greater decrease in fibrinogen levels 5 hours after the start of rt-PA infusion among black patients than in white and Hispanic patients without evidence of more frequent infarct-related artery patency or hemorrhagic complications, and (3) thrombolytic therapy with appropriate supplemental measures is associated with comparable 1-year mortality in white, black, and Hispanic patients.

The purpose of this study was to investigate a family with type IV Ehlers-Danlos syndrome (EDS-IV) and platelet sensitivity to aspirin, an association that, to our knowledge, has not been reported previously. Type IV Ehlers-Danlos syndrome is a rare disorder of type III collagen metabolism characterized by bruising easily and death at an early age from exsanguination by rupture of a major viscus or artery. Previous studies have suggested an association between various types of Ehlers-Danlos syndrome and abnormal platelet function. In this family, EDS-IV is inherited in an autosomal dominant pattern. The transmission of the platelet functional disorder from the proband to only one of two children affected with EDS-IV in this family suggests that there is a genetic component to this condition that is independent of EDS-IV.

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.

This study investigated the incidences of undercarboxylated (protein induced by vitamin K absence: PIVKA) prothrombin and protein C in 496 neonates across a wide range of gestational ages. These findings are related to vitamin K1 levels (an indicator of cofactor availability) and vitamin K1 epoxide levels (a measure of the efficiency of the hepatic vitamin K cycle). PIVKA protein C was present in at least trace amounts in 27% of infants; whereas, PIVKA prothrombin was present in 7% of infants. PIVKA prothrombin and protein C were present at high plasma concentrations in 2% to 3% of term and preterm neonates and both PIVKA protein C and prothrombin increased with gestational age. Despite elevated plasma concentrations of PIVKA protein C and diminished levels of normally carboxylated protein C, clinical thrombosis was not observed. The mean (+/- SD) vitamin K1 level in the study population was 0.009 +/- 0.02 nmol/L (adult reference interval: 0.3 to 2.6 nmol/L) with no clear relationship between vitamin K1 levels and production of PIVKA protein C or prothrombin. By comparison with adults, the epoxide form of the vitamin comprised an abnormally high proportion of total vitamin K1; this suggests possible inefficiencies in hepatic reductase cycling.

Current concepts of cardiovascular disease pathophysiology include a prominent role for thrombosis as a key factor. Thrombosis is not only the usual precipitant to a clinical event, but it may also be involved in atherosclerotic plaque development throughout most of the adult years. However, our understanding of thrombotic risk factors, especially in the elderly, is poor and research has just begun in this area. Fibrinogen has been clearly established as an independent risk factor in the middle aged, but there are conflicting data concerning older persons. Factor VII and plasminogen activator inhibitor-1 look promising as risk factors in the middle aged, but there are no data currently available concerning the status of these factors in the elderly. Many associations exist between the thrombotic risk factors and other cardiovascular risk factors such as plasma lipids and glucose intolerance, making the establishment of independence difficult, and little is known about how these different factors may interact in older individuals. Ongoing studies should provide many answers in the near future.

Objectives: Protein C inhibits coagulation and promotes fibrinolysis. This study investigates the association between protein C deficiency and pregnancy loss, thrombosis in pregnancy, and thrombosis with oral contraception., Study Design: Fifteen protein C--deficient patients and 37 controls from a single kindred were studied. An obstetric history was obtained by telephone. Data were analyzed by logistic regression, Fisher's exact test, and Student t test., Results: Protein C--deficient women experienced a 33% pregnancy loss versus 19% in the controls (not significant). Thromboembolism during pregnancy in protein C--deficient women was 33% (45% in those not receiving prophylactic anticoagulation) versus 5% in controls (odds ratio 7.37, p = 0.026). Five of 12 protein C--deficient women using oral contraception developed thrombosis versus 0 of 33 controls. The risk of thrombosis for protein C--deficient women using oral contraception is increased (p < 0.001)., Conclusions: Perinatal outcome is not statistically different with protein C deficiency. Protein C deficiency increases the risk of thrombosis during pregnancy and with oral contraception. Prophylactic heparin is suggested during pregnancy for protein C--deficient women with personal or family histories of thrombosis. Oral contraception is not advised.

To evaluate sources of interlaboratory variation in factor VIII coagulant assays and the effects of uniform calibration on it, data were analyzed from Survey Set H2-C, 1987, of the College of American Pathologists, Northfield, Ill, into which the College of American Pathologists Reference Preparation for Factor VIII was incorporated. Peer group performance and its improvement by uniform calibration were evaluated by comparing means, precisions, and numbers of acceptable survey scores. Results showed a poorer performance by less experience laboratories and by those that used undesirable calibrators. Substantial improvement was seen with uniform calibration, especially among laboratories that had employed poorer calibrators. Although variance component analysis showed that the type of calibrator was the most important contributor to interlaboratory variation, it accounted for only 10% of total variability. Participant summaries and questionnaires that spanned several years revealed steady improvement in methodology but no striking changes in interlaboratory variation.

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.

This study investigates type II protein C deficiency in a family with manifestations of both arterial and venous thrombosis. Of 64 members of the kindred, 14 have been tested and 7 have PC deficiency. Among affected individuals (n = 7), mean protein C levels by different assays were as follows: enzyme-linked immunosorbent assay (ELISA), 3.8 micrograms/mL (2.1 to 4.3 micrograms/mL); amidolytic with venom activator, 115% (60% to 140%); clotting with venom activator, 42% (23% to 59%). The mean ratio of clotting to amidolytic assays for the affected individuals was 0.37 compared with a normal range of 0.8 to 1.2. Thus, the affected individuals have normal total protein C and their activated protein C has a normal active site assessed by chromogenic substrate; however, they have markedly diminished clotting activity. Immunoassay and chromatography data suggested an abnormality of carboxylation in the gamma carboxyglutamic acid (Gla) domain. Polymerase chain reaction amplification and direct DNA sequencing of exon 2 from genomic DNA of affected individuals showed two nucleotide substitutions. One of the mutations (A----C) results in Glu20----Ala, thereby eliminating a site for vitamin K-dependent gamma-carboxylation. The other substitution (G----A) results in a Val34----Met mutation. DNA sequencing of the other exons from affected individuals has shown no further difference from that of the wild-type gene. The former mutation also removes a Bgl II restriction endonuclease site, which has allowed us to confirm the mutation in affected individuals by direct digestion and Southern hybridization of genomic DNA from family members. This is the first reported family with documented Gla domain mutations in the protein C gene.

Monitoring coagulation parameters during thrombolytic therapy could be useful for prediction and treatment of haemorrhagic episodes. Technology based on dry reagent chemistry has been developed that allows rapid (less than 10 min) assays on small samples of whole blood. The assay principle is based on the restriction of motion of paramagnetic particles during fibrin polymerization, and subsequent liberation of particle motion during fibrinolysis. This technology was used to monitor prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen levels and fibrinolysis profiles during thrombolytic therapy with tissue plasminogen activator for acute myocardial infarction. The PT and aPTT obtained with the COAG-1 correlated well with conventional assays (r = 0.93 and 0.92 for PT and aPTT, respectively; p = 0.0001). Fibrinogen estimates, obtained by COAG-2 also correlated well with modified Clauss assays (r = 0.86, p = 0.0001). The rapid determination of the aPTT may improve management of adjunctive anticoagulant therapy following thrombolysis. The fibrinolysis profile may be useful during thrombolytic therapy to verify that a lytic state has been achieved, to monitor the lytic state throughout therapy, and to verify that the lytic state normalizes once therapy has been completed.

The use of thrombolytic therapy has dramatically altered the treatment of acute myocardial infarction and is rapidly spreading from large medical centers to community hospitals throughout the country. The widespread use of thrombolytic therapy will benefit a wide range of people, but the potential risks of this form of therapy must be understood. Hemorrhage is one of the major risks of thrombolytic therapy. This review will focus on the data available from a number of recent, large trials of thrombolytic therapy for acute myocardial infarction with respect to laboratory parameters that may predict hemorrhagic complications and/or help with their management. We will discuss both conclusions drawn from currently available data and address future research directions.

The anticoagulant factor Protein S circulates in two major forms, free and bound to C4b binding protein (C4BP). We report a monoclonal antibody-based enzyme-linked immunosorbent assay of human Protein S that is sensitive (detection limit 30 ng) and free of notable competition from other vitamin K-dependent proteins. We demonstrate assay sensitivity to Protein S-C4BP complex, as well as to free Protein S by (a) results of immunoaffinity chromatography involving the assay antibody; (b) parallelism between the standard curve and a plasma dilution curve, including dilutions greater than 100-fold; (c) lack of effect of added C4BP on Protein S values; and (d) reactivity in the assay by high-molecular-mass plasma Protein S in gel permeation studies. These latter studies also indicate that uncomplexed Protein S has an apparent molecular mass of approximately 150,000 Da, attributable to either polymerization or conformational considerations. Inter- and intra-assay CVs were 9.8% and 5.1%, respectively, and 90% of Protein S added to plasma was recovered. Reference ranges (mean and SD) for total Protein S in middle-aged normal subjects were 16.6 (1.9) mg/L for men (n = 54) and 16.0 (3.0) mg/L for women (n = 38). In the polyethylene glycol precipitation method, the reference values for free Protein S were 5.4 (1.6) mg/L for men and 4.4 (1.1) mg/L for women.

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.

A 67-year-old woman had symptoms of an upper respiratory tract infection for which she received a five-day course of erythromycin. Epistaxis and gross hematuria subsequently developed, and the patient was found to have a selective Factor X deficiency. She received supportive therapy and prothrombin complex concentrates (Factors II, VII, IX, and X), with subsequent resolution of her transient Factor X deficiency. Her hospital course, however, was complicated by the development of multiple cerebral infarctions. This is the tenth reported case of transient Factor X deficiency not associated with amyloidosis. In seven of the previous cases, as in this patient, the deficiency was associated with a preceding upper respiratory infection. This is the only case, however, with evidence of inhibitory activity in the plasma that was directed toward Factor X.

Recent laboratory studies have demonstrated that intracisternal administration of recombinant tissue plasminogen activator (rt-PA) can facilitate the normal clearing of blood from the subarachnoid space and prevent or ameliorate delayed arterial spasm. The results of a preliminary Phase I trial of intracisternal rt-PA in 10 patients are reported with documented aneurysmal subarachnoid hemorrhage (SAH). All patients enrolled were classified as clinical Grade III or IV (according to Hunt and Hess) with thick clots or layers of blood in the basal cisterns and major cerebral fissures (Fisher Grade 3). Ventriculostomy and surgery for clipping of the aneurysms were performed within 48 hours of hemorrhage. In one patient, 10 mg rt-PA was instilled into the subarachnoid cisterns prior to closing the dura. In the remaining nine patients, a small silicone catheter was left in the subarachnoid space and rt-PA (5 mg in four cases or 1.5 mg (0.5 mg every 8 hours for three infusions) in five cases) was instilled 12 to 24 hours after surgery. Minor local bleeding complications were noted in all patients receiving 5 or 10 mg rt-PA. Oozing was noted at the operative incision site in four of five patients and at the ventriculostomy site in two patients. One patient developed a small epidural hematoma that was treated by delayed drainage. No bleeding complications were noted in the patients receiving the lower regimen of rt-PA (three infusions of 0.5 mg each). Serial coagulation studies demonstrated no evidence of systemic fibrinolysis. Analysis of cisternal cerebrospinal fluid samples revealed thrombolytic tissue plasminogen activator (t-PA) levels for 24 to 48 hours. Follow-up cerebral angiography 7 to 8 days after rupture disclosed mild to moderate spasm in nine patients, while one patient with hemorrhage from a posterior inferior cerebellar artery aneurysm had severe focal spasm of the vertebral arteries that was not symptomatic. These results suggest that postoperative treatment with rt-PA may be effective in reducing the severity of delayed cerebral vasospasm. The results of serial t-PA levels suggest that the lower dosage regimen with divided dosages at 8-hour intervals is well tolerated and that even lower dosages may be effective. Further studies are clearly indicated.

In the Thrombolysis in Myocardial Infarction, Phase II pilot and clinical trial, 908 patients [326 (35.9%) in the pilot study and 582 (64.0%) in the randomized study] were treated with 150 mg recombinant tissue-type plasminogen (rt-PA) activator in combination with heparin and aspirin, and 3,016 patients [64 (2.1%) in the pilot study and 2,952 (97.9%) in the randomized study] were treated with 100 mg rt-PA in combination with heparin and aspirin. Adverse neurological events occurred in 23 patients treated with 150 mg rt-PA (2.5%) [nine cerebral infarctions (1.0%), 12 intracerebral hemorrhages (1.3%), and two subdural hematomas (0.2%)] and in 33 patients treated with 100 mg rt-PA (1.1%) [20 cerebral infarctions (0.7%), 11 intracerebral hemorrhages (0.4%), and two subdural hematomas (0.1%)]. The difference in adverse neurological events observed comparing the two rt-PA regimens was primarily due to a higher frequency of intracerebral bleeding among patients treated with 150 mg rt-PA (1.3% versus 0.4%, p less than 0.01). Patients with recent (within 6 months) histories of stroke were not eligible for the study, and patients with any history of cerebrovascular disease were declared ineligible early in the study. The small number of patients (89, or 2.3%) with any history of neurological disease, intermittent cerebral ischemic attacks, or stroke who were enrolled before the stricter eligibility criteria were imposed or on the basis of incomplete baseline information experienced an increased frequency of intracerebral hemorrhage compared with patients without such histories (3.4% versus 0.5%). Mortality at 6 weeks after presentation among 23 patients who had intracerebral hemorrhage was 47.8%. Intracerebral hemorrhage is a severe but infrequent complication of rt-PA therapy for acute myocardial infarction. The combined frequency of intracerebral hemorrhage, subdural hematoma, and cerebral infarction after treatment with 100 mg rt-PA is comparable to that observed in other trials with thrombolytic agents in acute myocardial infarction.

Lupus anticoagulants are antibodies that interfere with in vitro phospholipid-dependent coagulation reactions. In vivo, they have been associated with a variety of thromboembolic problems. Samples from patients with lupus anticoagulants were included in the 1986 and 1987 College of American Pathologists proficiency survey program. Participant performance on these samples demonstrated significant variation in the responsiveness of different activated partial thromboplastin reagents to lupus anticoagulants. The level of factor VIII in these samples reported by the participants also varied with the reagent used. Follow-up studies demonstrated striking reagent-dependent differences in the dilutional effect on apparent factor VIII, IX, XI, and XII activity. These results point out the importance of selecting sensitive and responsive reagents for appropriate identification of lupus inhibitors. In addition, the results indicate that the choice of reagent used for factor assays can affect the apparent factor activity as well as whether a dilutional effect is noted when a lupus anticoagulant is present in the test sample, an important consideration when trying to distinguish a lupus anticoagulant from a specific factor inhibitor.