Acute phase reaction, fibrinogen level and thrombus size

Association between histological severity of Helicobacter pylori infection and cardiovascular risk scores in the Korean population

BACKGROUND AND AIMS

Although there have been several reports on the association between Helicobacter pylori (HP) infection and cardiovascular disease (CVD), most studies have been done through noninvasive testing such as serologic test or urea breath test. This study investigated the relationship between histological features of HP gastritis and cardiovascular risk scores.

METHODS

A total of 21,251 subjects (mean age, 43.8 ± 9.6 years; males, 72.1%) who underwent routine health checkup and gastric biopsy were retrospectively analyzed. The severity of gastritis was assessed using the updated Sydney system (USS). With four different risk predicting algorithms, we calculated Framingham coronary heart disease (CHD) risk score, ATP III revised Framingham CHD risk score, generalized Framingham risk against total CVD, and ACC/AHA 10-year risk of a first hard atherosclerotic-CVD event in each subject.

RESULTS

About half of the study subjects (51.2%, n = 10,890) were confirmed to have HP infection. Subjects with HP infection were younger (42.9 ± 9.0 vs. 44.7 ± 10.2 years, p < 0.001) than those without. After adjustment for age, most of the estimated 10-year cardiovascular risk increased as the grade of USS elements increased. As the sum of the USS scores increased, all the 4 estimated 10-year cardiovascular risk scores increased proportionally (p < 0.05 for each).

CONCLUSIONS

The histological features of gastritis assessed using USS were associated with various cardiovascular risk scores. This study provides strong evidence on an association between chronic inflammation and increased cardiovascular risk.

Differential haemostatic risk factors for pregnancy-related deep-vein thrombosis and pulmonary embolism

Limited data exist on thrombophilia and the risk of venous thrombosis (VT) during pregnancy and postpartum. The objectives of the present study were to investigate the role of haemostatic risk factors for pregnancy-related VT and their phenotypic expression in deep-vein thrombosis (DVT) and pulmonary embolism (PE). Total 313 cases with objectively verified first time VT and 353 controls were selected from a source population of 377,155 women with 613,232 pregnancies. The adjusted odds ratio (aOR) for pregnancy-related VT was 1.7 (95% confidence interval [CI] 1.1–2.8) for women with factor VIII >90th percentile. The aOR for VT for endogenous thrombin potential and D-dimer values >90thpercentiles were 1.8 (95% CI 1.1–3.0) and 2.1 (95% CI 1.3–3.3), respectively. Factor IX >90thpercentile or free protein S ≤the 5th percentile increased the risk for PE, and the aORs were 2.4 (95% CI 1.1–5.0) and 3.1 (95% CI 1.3–7.2), respectively. Women carrying the factor V Leiden (F5 rs6025) polymorphism, or who had reduced sensitivity to activated protein C (aPC) in the absence of F5 rs6025, had increased risk for DVT, with unadjusted ORs 7.7 (95% CI 4.7–12.7) and 3.5 (95% CI 2.2–5.4), respectively. Women with a history of pregnancy-related VT showed activation of coagulation and had elevated factor VIII. Furthermore, high levels of factor IX and low levels of free protein S were associated with increased risk for PE, whereas aPC resistance and F5 rs6025 were risk factors for DVT and not PE.

Time course of haemostatic effects of fibrinogen concentrate administration in aortic surgery

Background

There is currently a contrast between the demonstrated benefits of fibrinogen concentrate in correcting bleeding and reducing transfusion, and its perceived thrombogenic potential. This analysis evaluates the effects of fibrinogen concentrate on coagulation up to 12 days after administration during aortic surgery.

Methods

We performed a post hoc analysis of a prospective, randomized, double-blind, controlled trial of fibrinogen concentrate as first-line haemostatic therapy in aortic surgery. After cardiopulmonary bypass (CPB) and protamine administration, subjects with coagulopathic bleeding received fibrinogen concentrate or placebo. The placebo group received allogeneic blood products, including fresh-frozen plasma (FFP; n=32); the fibrinogen concentrate group received fibrinogen concentrate alone (FC; n=14), or fibrinogen concentrate followed by allogeneic blood products (FC+FFP; n=15). Plasma fibrinogen, fibrin-based clotting (ROTEM^®-based FIBTEM assay), and peri- and postoperative haematological and coagulation parameters were compared.

Results

Plasma fibrinogen and FIBTEM maximum clot firmness (MCF) decreased ∼50% during CPB but were corrected by FC or FC+FFP. At last suture, the highest values for plasma fibrinogen (360 mg dl⁻¹) and FIBTEM MCF (22 mm) were within normal ranges—below the acute phase increases observed after surgery. In patients receiving only FFP as a source of fibrinogen, these parameters recovered marginally by last suture (P<0.001 vs FC and FC+FFP). All groups displayed comparable haemostasis at 24 h post-surgery. Fibrinogen concentrate did not cause alterations of other haemostasis parameters.

Conclusions

Fibrinogen concentrate provided specific, significant, short-lived increases in plasma fibrinogen and fibrin-based clot firmness after aortic surgery.

Causal relationship between hyperfibrinogenemia, thrombosis, and resistance to thrombolysis in mice

Epidemiologic studies have correlated elevated plasma fibrinogen (hyperfibrinogenemia) with risk of cardiovascular disease and arterial and venous thrombosis. However, it is unknown whether hyperfibrinogenemia is merely a biomarker of the proinflammatory disease state or is a causative mechanism in the etiology. We raised plasma fibrinogen levels in mice via intravenous infusion and induced thrombosis by ferric chloride application to the carotid artery (high shear) or saphenous vein (lower shear); hyperfibrinogenemia significantly shortened the time to occlusion in both models. Using immunohistochemistry, turbidity, confocal microscopy, and elastometry of clots produced in cell and tissue factor-initiated models of thrombosis, we show that hyperfibrinogenemia increased thrombus fibrin content, promoted faster fibrin formation, and increased fibrin network density, strength, and stability. Hyperfibrinogenemia also increased thrombus resistance to tenecteplase-induced thrombolysis in vivo. These data indicate that hyperfibrinogenemia directly promotes thrombosis and thrombolysis resistance and does so via enhanced fibrin formation and stability. These findings strongly suggest a causative role for hyperfibrinogenemia in acute thrombosis and have significant implications for thrombolytic therapy. Plasma fibrinogen levels may be used to identify patients at risk for thrombosis and inform thrombolytic administration for treating acute thrombosis/thromboembolism.

The value of serum procalcitonin in differential diagnosis of pulmonary embolism and community-acquired pneumonia

Presence of high fever may cause confusion in differential diagnosis of pulmonary embolism (PE) versus pneumonia. The aim of this study is to investigate the diagnostic value of serum procalcitonin (PCT) in differential diagnosis of PE and community-acquired pneumonia (CAP). A total of 24 patients with proven PE and 22 patients with CAP were included in the study. The study population was subdivided as PE patients with fever (group 1, n = 8) and without fever (group 2, n = 16); and CAP (group 3, n = 22). Serum PCT and systemic inflammatory markers were measured at the initial diagnosis and the third day of the treatment. The relation of PCT level with the other systemic inflammatory markers was investigated in each measurement point. The initial mean serum PCT level in group 3 (2.24 ± 0.99 ng/mL) was statistically higher than group 1 (0.48 ± 0.77 ng/mL) and group 2 (0.14 ± 0.17 ng/mL; P = .000, .000, respectively). Procalcitonin level at the initial (2.24 ± 0.99 ng/mL) and the third day of treatment (0.92 ± 0.62 ng/mL) in group 3 showed a statistically significant reduction (P = .000). There were no statistically significant reduction in PCT levels by anticoagulation in groups 1 and 2 (P = .262, .119, respectively). Other systemic inflammatory markers including interleukin 6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor α (TNF-α) levels statistically significantly decreased with anticoagulant and antimicrobial therapy. This study suggested that serum PCT level may be valuable for differentiating PE patients with or without fever from patients with CAP.

C-reactive protein and venous thromboembolism. A prospective investigation in the ARIC cohort

The role of inflammation in the causation of venous thromboembolism (VTE) is uncertain. In 10,505 participants of the Atherosclerosis Risk in Communities (ARIC) Study, we assessed the association of the systemic inflammation marker, elevated C-reactive protein (CRP), with incidence of VTE (n=221) over a median of 8.3 years of follow-up. Adjusted for age, race, and sex, the hazard ratios of VTE across quintiles of CRP were 1.0, 1.61, 1.16, 1.56, and 2.31 (p for trend p<0.0007). For CRP above the upper 10 percentile (> or = 8.55 mg/L), compared with the lowest 90% of CRP values, the hazard ratio of VTE was 2.07 (95% CI 1.47, 2.94). Further adjustment for baseline hormone replacement therapy, diabetes, and body mass index attenuated the hazard ratios only slightly. For example, the adjusted hazard ratio of VTE was 1.76 (95% CI 1.23, 2.52) for CRP above versus below the 90(th) percentile. In conclusion, this prospective, population-based study suggests elevated CRP is independently associated with increased risk of VTE.

Role of Chlamydia pneumoniae in atherosclerosis

Cardiovascular disease, resulting from atherosclerosis, is a leading cause of global morbidity and mortality. Genetic predisposition and classical environmental risk factors explain much of the attributable risk for cardiovascular events in populations, but other risk factors for the development and progression of atherosclerosis, which can be identified and modified, may be important therapeutic targets. Infectious agents, such as Chlamydia pneumoniae, have been proposed as contributory factors in the pathogenesis of atherosclerosis. In the present review, we consider the experimental evidence that has accumulated over the last 20 years evaluating the role of C. pneumoniae in atherosclerosis and suggest areas for future research in this field.

Relationship between minor myocardial damage and inflammatory acute-phase reaction in acute coronary syndromes

BACKGROUND

In severe acute coronary syndromes (ACS) elevation of markers of inflammation and acute phase reaction (APR) like C-reactive protein (CRP) as well as a release of troponin have been reported. Using a high sensitivity troponin T (TnT) test we investigated whether an APR occurs in ACS only in the presence of ischemic myocardial damage.

METHODS

In 85 patients with ACS C-reactive protein (CRP), serum amyloid A (SAA), fibrinogen, thrombin antithrombin III complexes (TAT) and kallikrein were determined vs. high sensitive TnT (> or =0.02 ng/ml) initially and 2 d later vs. 45 patients with stable angina pectoris and 42 controls.

RESULTS

In stable angina pectoris, markers of inflammation and coagulation were slightly elevated (p < 0.05). Initially in ACS elevations of CRP to 1.2 +/- 0.3 mg/dl, SAA to 4.8 +/- 2.6 mg/dl and fibrinogen to 448 +/- 21 mg/dl (all p < 0.01 vs. controls) were found followed by a significant APR (p < 0.01). In the subgroup of TnT positive ACS patients, an APR with increased CRP (4.1 +/- 1.3 mg/dl), SAA (20.4 +/- 8.3 mg/dl), and fibrinogen (641 +/- 45 mg/dl) was detectable (all p < 0.05 vs. TnT negative patients). In contrast, patients without TnT release showed APR markers comparable to patients with stable angina pectoris.

CONCLUSION

Our findings demonstrate an association between myocardial injury in ACS and acute phase reaction as evidenced by several molecular markers. A highly sensitive TnT-test identified myocardial injury in about all patients with APR while a standard TnT cut-off (0.1 ng/ml) missed 32% of these patients. Thus, the APR in patients with ACS is strongly associated with at least minor ischemic myocardial damage and prior findings of an APR independent from myocardial injury are probably based on less sensitive troponin tests.

[Fibrinogen as a risk factor in ischemic heart disease]

<zakljucak> Mesto fibrinogena u razvoju ateroskleroze i arterijske tromboze je verovatno znacajno jer on ucestvuje i u procesu nastanka i rasta plaka modulise hemoreoloske osobine krvi, a cini i osnovu koaguluma tokom procesa tromboze. Koncentracija fibrinogena u krvi je dobar nezavisan prognosticki parametar za razvoj akutnog infarkta miokarda, kako kod zdravih odraslih osoba, tako i kod koronarnih bolesnika. Nivo fibrinogena u krvi je delimicno genetski determinisan, ali i brojni faktori spoljasnje sredine uticu na njegov nivo. Vrlo je bitan odnos izmedju fibrinogena i nekih drugih vaznih faktora rizika. Fibrinogen i holesterol imaju izgleda sinergisticki ucinak na razvoj akutnog koronarnog sindroma. Moguce je da je fibrinogen jedna od najznacajnijih spona izmedju pusenja i koronarne bolesti. Veoma je mali broj lekova koji se mogu dugorocno primenjivati i smanjiti nivo fibrinogena u krvi, tako da za sada ne postoje klinicke studije o vrednosti ovakve terapije u lecenju i prevenciji akutnih koronarnih sindroma. Shodno tome sve dok se ne dokaze da se smanjenjem nivoa fibrinogena u krvi smanjuje rizik za ispoljavanje koronarne bolesti, njegova uloga kao faktora rizika ostaje nedovoljno definisana.

Fibrinogen and C-reactive protein on admission as markers of final infarct size after primary angioplasty for acute myocardial infarction

BACKGROUND

In acute myocardial infarction (AMI) treated conservatively or with thrombolysis, marked increases of C-reactive protein (CRP) and fibrinogen have been observed. No data are however available concerning a possible relation between CRP and fibrinogen levels on admission and markers of infarct size after obtaining thrombolysis in myocardial infarction (TIMI) flow III by primary angioplasty.

METHODS

We studied 34 patients with a first AMI (29 men, mean age 54+/-11 years) who were treated with primary angioplasty (TIMI flow III in all patients, no concomitant treatment with glycoprotein IIb-IIIa antagonists) within 6 h of onset of pain. CRP and fibrinogen levels on admission were determined and related to the following markers of infarct size: peak creatine kinase MB (CKMB) levels, radionuclide left ventricular ejection fraction (LVEF) at discharge and thallium-201 single-photon emission computed tomography (SPECT) infarct size at 1 month.

RESULTS

Median CRP levels were 0.4 mg/dl (range 0.09-3 mg/dl), median fibrinogen levels 412 mg/dl (range 198-679 mg/dl), mean CKMB was 178+/-151 U/l, mean LVEF 52+/-8% and mean thallium-201 infarct size 7+/-6%. Although CRP levels were related to fibrinogen levels on admission (r=0.56, P=0.002), only fibrinogen levels were related to markers of infarct size (r=0.58, P=0.001 for CKMB, r=-0.44, P=0.01 for LVEF and r=0.64, P=0.001 for thallium-201 infarct size). No relation was found between CRP or fibrinogen levels on admission and the extent of coronary artery disease or the myocardial area at risk. In multiple regression analysis, the relation between fibrinogen and markers of infarct size was independent of CRP levels and the duration of pain on admission.

CONCLUSIONS

These findings indicate a relation between fibrinogen levels on admission and myocardial infarct size in patients treated with primary angioplasty for AMI. This relation seems to be independent of CRP levels and the duration of pain on admission. If confirmed in larger patient populations, fibrinogen levels on admission could have an important value for risk stratification and more aggressive reduction of infarct size in patients who are treated with primary angioplasty.

Increased reactivity of platelets induced by fibrinogen independent of its binding to the IIb-IIIa surface glycoprotein: a potential contributor to cardiovascular risk

OBJECTIVES

To determine whether augmented activation (degranulation) of platelets might contribute to the association between higher concentrations of fibrinogen and risk of myocardial infarction, we characterized adenosine diphosphate (ADP)-induced expression of P-selectin by platelets in whole blood as a function of this exposure to selected concentrations of fibrinogen.

BACKGROUND

An increased risk of myocardial infarction has been associated with increased concentrations of fibrinogen.

METHODS

Fibrinogen was added to blood anticoagulated with corn trypsin inhibitor (a specific inhibitor of Factor XIIa without effect on other coagulation factors). Degranulation of platelets was identified by flow cytometry.

RESULTS

Addition of fibrinogen to blood did not activate platelets under basal conditions (without ADP). By contrast, a concentration-dependent increase in ADP and thrombin receptor agonist peptide (TRAP)-induced activation occurred with increasing concentrations of fibrinogen. Increased ADP-induced degranulation was apparent with the addition of 100 mg/dl of fibrinogen (p < or = 0.001 for 1.5 micromol/liter ADP, n=10 subjects). Inhibition by abciximab of binding of fibrinogen to the surface glycoprotein IIb-IIIa did not attenuate the observed augmentation of reactivity induced by fibrinogen. Augmented degranulation was associated with uptake of fibrinogen into alpha-granules without surface binding despite pretreatment with abciximab as shown by laser scanning confocal microscopy.

CONCLUSIONS

Fibrinogen in blood augments degranulation of platelets in response to ADP and is accompanied by uptake of fibrinogen into alpha-granules. Thus, elevated concentrations of fibrinogen secondary to inflammation implicated in cardiovascular risk may operate, in part, by increasing reactivity of platelets.

Association of virulent Helicobacter pylori strains with ischemic heart disease

BACKGROUND

Previous studies have reported an association between chronic Helicobacter pylori infection and ischemic heart disease. However, it is not clear whether this association is really due to the virulence of the bacterium or is merely the result of confounding factors (in particular, age and social class).

METHODS AND RESULTS

We assessed the prevalence of infection by Helicobacter pylori and by strains bearing the cytotoxin-associated gene-A (CagA), a strong virulence factor, in 88 patients with ischemic heart disease (age, 57+/-8 years; 74 men) and in 88 age- and sex-matched controls (age, 57+/-8 years; 74 men) with similar social background. Prevalence of Helicobacter infection was significantly higher in patients than in controls (62% versus 40%; P=.004), with an odds ratio of 2.8 (95% CI, 1.3 to 7.4; P<.001) adjusted for age, sex, main cardiovascular risk factors, and social class. Patients with ischemic heart disease also had a higher prevalence of CagA-positive strains (43% versus 17%; P=.0002), with an adjusted odds ratio of 3.8 (95% CI, 1.6 to 9.1; P<.001). Conversely, prevalence of CagA-negative strains was similar in patients and controls (19% versus 23%), with an adjusted odds ratio of 0.8 (95% CI, 0.4 to 1.4).

CONCLUSIONS

The association between Helicobacter pylori and ischemic heart disease seems to be due to a higher prevalence of more virulent Helicobacter strains in patients. These results support the hypothesis that Helicobacter pylori may influence atherogenesis through low-grade, persistent inflammatory stimulation.

Fibrinogen as a factor of thrombosis: experimental study

Epidemiological, clinical, and experimental studies have clearly demonstrated the strong association between baseline fibrinogen level and risk of thromboembolic complications. The pathogenesis of postoperative or post-traumatic thrombosis in man is associated with fibrinogen level in plasma. The purpose of this study was to evaluate the effects of fibrinogen administration on thrombus formation at different dosages. To investigate these effects, we used an experimental model of induced thrombosis in rat microcirculation. This model allows single endothelial cell destruction by laser injuries, thus leading to thrombus formation. Fibrinogen was injected intravenously via penis vein and tested at various dosages (50, 100, and 200 mg/kg), 60 minutes after injection on arterial thrombosis induction and 120 minutes after injection on venous thrombosis induction. Results showed that the administration of fibrinogen increases the number of emboli, the duration of embolization, the amplitude, and the velocity of the ex-vivo platelet aggregation induced by ADP (p < 0.05). A positive correlation between the percent of fibrinogen increase in plasma and the enhancement of thromboembolic risk in the experimented animals was observed.

Physical activity status and adverse age-related differences in coagulation and fibrinolytic factors in women

Adverse changes in coagulation and fibrinolytic factors are thought to contribute to the increased risk of cardiovascular disease and atherothrombosis with age. We tested the hypothesis that such age-related changes in specific coagulation and fibrinolytic factors are absent in physically active women. Resting levels of plasma fibrinogen, tissue-type plasminogen activator (t-PA) antigen and activity, plasminogen activator inhibitor-1 (PAI-1) antigen and activity, and fibrin D-dimer were measured in 24 healthy premenopausal women: 11 sedentary (aged 28+/-1 years; Pre-S) and 13 physically active (aged 30+/-1 years; Pre-PA) and in 27 healthy postmenopausal women: 14 sedentary (aged 61+/-1 years; Post-S) and 13 physically active (aged 58+/-1 years; Post-PA). Post-S had higher (P<.05) fibrinogen, t-PA antigen, PAI-1 antigen, PAI-1 activity, and fibrin D-dimer levels and lower t-PA activity than Pre-S. Post-PA demonstrated lower (P<.01) plasma fibrinogen, t-PA antigen, PAI-1 antigen, and PAI-1 activity and higher (P<.01) t-PA activity levels than Post-S. In addition, plasma fibrin D-dimer levels tended (P=.06) to be lower in Post-PA than in Post-S. Although plasma levels of fibrinogen and fibrin D-dimer in Post-PA were lower than in Post-S, they were higher (P<.05) than in Pre-PA. Importantly, however, the fibrinolytic profile of Post-PA did not differ from that of Pre-PA. The results of the present study demonstrate that the adverse age-associated differences in plasma fibrinogen concentrations and the endogenous fibrinolytic system in sedentary healthy women are either attenuated or absent in highly physically active women. The smaller or absent age-related differences in coagulation and fibrinolytic factors in women who habitually exercise may represent an important mechanism contributing to their lower age-related increase in both cardiovascular disease and atherothrombotic events. Future studies need to determine whether women who are moderately active would demonstrate the same favorable hemostatic profile.

-455G/A polymorphism of the beta-fibrinogen gene is associated with the progression of coronary atherosclerosis in symptomatic men: proposed role for an acute-phase reaction pattern of fibrinogen. REGRESS group

Increased plasma fibrinogen levels have been identified as a risk indicator for myocardial infarction, stroke, and thrombosis. Both environmental and genetic factors make an important contribution to plasma fibrinogen levels in humans. In the present study we evaluated, in patients with serum cholesterol levels between 4 and 8 mmol/L, the relation of plasma levels and polymorphisms of fibrinogen with coronary artery disease (CAD), cross-sectionally at baseline and after a 2-year follow-up period in which they received either a placebo or pravastatin. Higher plasma fibrinogen levels (3.9 g/L) were observed at baseline in patients with the -455AA genotype than in patients with the -455GA (3.2 g/L) and -455GG (3.1 g/L) genotypes of the -455G/A fibrinogen beta gene polymorphism (P<.05). Plasma levels of fibrinogen were not related to the baseline angiographic variables (mean segment diameter [MSD] and minimum obstruction diameter [MOD]), nor to the quantitative changes in these angiographic variables. However, in the placebo group, patients with the -455AA genotype had more progression of CAD, expressed by a significantly greater decrease of the MSD and MOD, after the 2-year follow-up period than patients with the other genotypes. The -455G/A polymorphism was related to the progression of CAD, and pravastatin therapy seemed to offset this deleterious effect. We hypothesized that the -455A allele may promote a stronger acute-phase response in fibrinogen and that the resulting higher fibrinogen levels may form the pathogenetic basis for the stronger progression of coronary atherosclerosis. Experiments to verify this hypothesis are being proposed and advocated, in view of the possibility of identifying a genetic marker that can recognize a subgroup of patients with an increased risk who may benefit from early treatment with lipid-lowering or anticoagulant drugs.

Prognostic influence of increased fibrinogen and C-reactive protein levels in unstable coronary artery disease. FRISC Study Group. Fragmin during Instability in Coronary Artery Disease

BACKGROUND

The prognostic influences of fibrinogen and C-reactive protein levels and their relations to myocardial damage in unstable coronary artery syndromes have not been well described.

METHODS AND RESULTS

Fibrinogen and C-reactive protein were determined at inclusion and related to outcome after 5 months in 965 patients with unstable angina or non-Q-wave myocardial infarction randomized to 5 weeks with low-molecular-weight heparin or placebo. The probabilities of death were 1.6%, 4.6%, and 6.9% (P=.005) and the probabilities of death and/or myocardial infarction were 9.3%, 14.2%, and 19.1% (P=.002), respectively, in patients stratified by tertiles of fibrinogen (< 3.38, 3.38 to 3.99, and > or = 4.0 g/L). The probabilities of death were 2.2%, 3.6%, and 7.5% (P=.003) after stratification of patient data by tertiles of C-reactive protein level (< 2, 2 to 10, and > 10 mg/L). In logistic multiple regression analysis, increased fibrinogen levels were independently associated with the incidence of death and/or myocardial infarction (P=.013), and elevated C-reactive protein level was associated with the incidence of death (P=.012). The increased relative risk of subsequent death or myocardial infarction in individuals with an elevated fibrinogen level was consistent in most subgroups evaluated; although significantly so only in patients with signs of myocardial damage.

CONCLUSIONS

Increased levels of both fibrinogen and C-reactive protein are associated with a worse outcome in patients with unstable coronary artery disease. The increased risk associated with elevated fibrinogen levels is independent of, and additive to, the prognostic influence of myocardial damage.

Chronobiological patterns of onset of acute cerebrovascular diseases

There is a considerable amount of data indicating that several major unfavorable cerebrovascular events are not randomly distributed over time, but show a peculiar distribution along the day, the week, and the months of the year. The authors review the available evidence on the chronobiological (circadian, weekly, and seasonal) patterns of onset of acute cerebrovascular diseases and variations in their possible triggering mechanisms. The existence of a peculiar chronobiological pattern in the onset of acute cerebrovascular disease, characterized by both circadian (morning and evening occurrence), circaseptan (last and first days of the week), and circannual (especially in winter) is confirmed, although differences depending on biological (gender, age), pathological (diabetes, hypertension, smoke, alcohol), cultural, social, and environmental factors exist. A deeper knowledge of the underlying pathophysiologic mechanisms could provide more effective insights for both preventive strategies and optimization of therapeutic approach.

Resistance of gammaA/gamma' fibrin clots to fibrinolysis

Elevated plasma fibrinogen levels are a major risk factor for thrombosis. This report shows two mechanisms by which fibrinogen can affect the fibrinolysis rate in vitro and thus may lead to thrombosis. First, the lysis rate of fibrin decreases as the initial concentration of fibrinogen increases. Second, a minor variant form of fibrinogen decreases the rate of fibrinolysis. This variant, gammaA/gamma' fibrinogen, has one altered gamma chain and is known to bind to factor XIII zymogen. In a fibrinolysis assay containing purified thrombin, fibrinogen, tissue-type plasminogen activator, and plasminogen, clots from gammaA/gammaA and gammaA/gamma' fibrinogen lysed at similar rates. However, when factor XIII was added, slower lysis was seen in gammaA/gamma' fibrin clots when compared with gammaA/gammaA fibrin clots. A D-dimer agglutination assay showed that the gammaA/gamma' clots were more highly cross-linked than the gammaA/gammaA clots. The lysis rates of gammaA/gamma' clots were similar to gammaA/gammaA clots in the presence of N-ethylmaleimide, a specific inhibitor of factor XIIIa. The gammaA/gamma' fibrin clots made in the presence of factor XIII showed increased proteolytic resistance to both plasmin and trypsin. Clots made from afibrinogenemic plasma reconstituted with gammaA/gamma' fibrinogen also showed significant resistance to lysis compared with gammaA/gammaA fibrinogen. These data demonstrate gammaA/gamma' fibrin is resistant to fibrinolysis, possibly as a result of concentrating factor XIII on the clot. The total fibrinogen concentration and the amount of gammaA/gamma' fibrinogen increase clot stability in vitro and thus may contribute independently to the risk of thrombosis in humans.

Morphological and hemostatic changes in rats with abdominal arterial prosthesis

We evaluated the changes over time in hemostatic factors during ongoing arterial thrombosis in rats, as induced by a loop-shaped aortic prosthesis. Moreover, we investigated this condition by inspecting in parallel local thrombus growth, systemic vascular prostacyclin and t-PA production. One minute after loop insertion, activated platelets spread on the internal surface of the prosthesis and 24 hrs later numerous platelet aggregates supported by a fibrin network could be observed. However, no evidence for platelet activation could be concomitantly found in peripheral blood. A sustained increased in PGI2 formation was detected together with a progressive increase in plasma fibrinolytic activity during thrombus growth. The levels of fibrinogen as well as antithrombin III (ATIII) and heparin cofactor II (HCII) activities were steadily increased in loop-bearing animals. In conclusion, the dynamic phases of thrombus formation, in an aortic prosthesis, produce changes in vascular function and in hemostatic factors at the level of systemic blood.

Hemostatic abnormalities in acute myocardial infarction as detected by specific blood markers

In order to elucidate the mechanism of thrombus formation in acute myocardial infarction (AMI), coagulation and fibrinolytic and inhibitory proteins were systemically examined in 12 patients with AMI and 29 normal subjects. Activities of factor XII, II and V and concentration of high molecular weight kininogen and Factor II were significantly lower in AMI patients than in normal control subjects. Factor XI activity was also increased in AMI patients as compared with normal controls. Von Willebrand Factor and fibrinogen levels were increased in patients with AMI. Plasma D-dimer concentration was also significantly higher in AMI patients than in controls. Activation of the intrinsic pathway, thrombin generation, fibrin formation and fibrin degradation may be present in patients with AMI just after the onset of coronary thrombus formation.

Seasonal variations of plasma fibrinogen and factor VII activity in the elderly: winter infections and death from cardiovascular disease

There are approximately 20,000 excess deaths from cardiovascular disease each winter in England and Wales. The reasons for the excess have not been fully elucidated. For one year, we studied 96 men and women aged 65-74 living in their own homes in order to examine seasonal variation in plasma fibrinogen and factor VII clotting activity (FVIIc), and to investigate relationships with infection and other cardiovascular-disease risk factors. Both fibrinogen and FVIIc plasma values were greater in winter with estimated winter-summer differences (confidence intervals) of 0.13 (0.05-0.20) g/L for fibrinogen and 4.2 (1.2-7.1)% of standard for FVIIc. These differences could account for 15% and 9% increases in ischaemic heart disease risk in winter respectively. After adjustment for confounding by season, fibrinogen was strongly related to neutrophil count (p < 0.0001), C-reactive protein (p < 0.0001), alpha 1-antichymotrypsin (p < 0.0001), and self-reported cough (p < 0.0001) and coryza (p = 0.0004), but not to ambient temperature. Therefore, we suggest that seasonal variation in fibrinogen might be induced by winter respiratory infections via activation of the acute phase response. Seasonal variations in the cardiovascular risk factors fibrinogen and FVIIc provide further possible explanations for the marked seasonal variation in death from ischaemic heart disease and stroke in the elderly.

The role of fibrinogen as a cardiovascular risk factor

Several epidemiological studies have produced longitudinal data identifying fibrinogen as a major cardiovascular risk factor. Cross-sectional results show strong associations between fibrinogen and a variety of demographic variables, cardiovascular risk factors, or diseases. Clinical cohort studies demonstrate that fibrinogen might also be a risk factor for the sequelae of cardiovascular disease. Knowledge about the determinants of the plasma level of fibrinogen in health and disease is as yet incomplete. Understanding of the mechanisms leading to the atherothrombogenic action of fibrinogen is also fragmentary. Fibrinogen strongly affects blood coagulation, blood rheology and platelet aggregation; in addition fibrinogen and its metabolites have direct effects on the vascular wall. Finally, fibrinogen is a prominent acute phase protein. All of these phenomena might provide some insight into the pathophysiological mechanisms involved. It is concluded that fibrinogen represents a major, independent risk factor that should now be included into the cardiovascular risk profile.

Strenuous exercise, plasma fibrinogen, and factor VII activity

OBJECTIVE

To assess the effect of physical activity on plasma fibrinogen and factor VII activity and thus on the risk of ischaemic heart disease.

DESIGN

Cross sectional survey.

SETTING

Ten group practices in the Medical Research Council's General Practice Research Framework.

PATIENTS

3967 men aged 45-69 attending screening clinics for the thrombosis prevention trial.

METHODS

Structured interview to elicit the intensity and frequency of physical exercise during past month. Measurement of fibrinogen, factor VII activity, cholesterol concentration, blood pressure, and other indices of ischaemic heart disease risk.

RESULTS

Strenuous exercise was associated with significantly lower fibrinogen concentrations than mild exercise, implying a difference of about 15% in the risk of ischaemic heart disease. Strenuous exercise was also associated with lower cholesterol concentrations. More frequent strenuous exercise was associated with lower factor VII activity.

CONCLUSIONS

With the recognition of plasma fibrinogen as a strong index of ischaemic heart disease risk the results of this and other studies suggest a pathway through which the protective effect of strenuous exercise may partly be mediated and they provide doctors and patients with a valuable incentive towards prevention, particularly in those whose risk of ischaemic heart disease is substantially due to raised fibrinogen concentrations.

Physiologic alteration of fibrinogen levels: influence upon patency of microvenous anastomoses

High baseline levels of plasma fibrinogen have been correlated with increased risk for cardiovascular disease. Since fibrinogen plays a central role in both coagulation and platelet aggregation and is a primary component of thrombi, this study was designed to assess the relationship of circulating fibrinogen concentration and vein anastomotic patency. Subcutaneously injected turpentine was used to increase, and intravenous ancrod (snake venom) to decrease, plasma fibrinogen levels. Rat femoral vein anastomoses were performed, and patency was assessed after 120 min of flow. Rat tail bleeding times were obtained, and blood samples were drawn to determine fibrinogen and plasma protein concentrations, Lee-White clotting times, and activated partial thromboplastin times (APTT). Increased patency was found in the ancrod group (88%) (P < 0.05 vs. controls); turpentine-treated and control groups were not significantly different (71% and 63%, respectively). The ancrod group also showed significantly prolonged tail bleeding times and APTT. Fibrinogen levels were significantly decreased in the ancrod group (1.73 mg/ml) and elevated in the turpentine group (4.91 mg/ml) vs. controls (2.34 mg/ml; P < 0.005). These results indicate that elevated fibrinogen levels, in particular when triggered by an acute-phase response, do not appear to predispose small vessel repairs toward thrombosis. Furthermore, this study supports the use of ancrod as an anticoagulant for microvascular surgery.

Properties of four acute phase proteins: C-reactive protein, serum amyloid A protein, alpha 1-acid glycoprotein, and fibrinogen

Four plasma proteins, referred to as positive acute phase proteins because of increases in concentration following inflammatory stimuli, are reviewed: C-reactive protein (CRP), serum amyloid A protein (SAA), alpha 1-acid glycoprotein (AAG), and fibrinogen. The CRP and SAA may increase in concentration as much as 1000-fold, the AAG and fibrinogen approximately twofold to fourfold. All are synthesized mainly in the liver, but each may be produced in a number of extrahepatic sites. The role of cytokines in induction of the acute phase proteins is discussed, particularly the multiple functional capabilities of interleukin-6 (IL-6). Other cytokines that regulate acute phase gene expression and protein synthesis include IL-1, tumor necrosis factor alpha, interferon gamma, as well as other stimulatory factors and cofactors. The physicochemical characteristics of each protein are reviewed together with the molecular biology. For each protein, the known biological effects are detailed. The following functions for CRP have been described: reaction with cell surface receptors resulting in opsonization, enhanced phagocytosis, and passive protection; activation of the classical complement pathway; scavenger for chromatin fragments; inhibition of growth and/or metastases of tumor cells; modulation of polymorphonuclear function; and a few additional diverse activities. The role of plasma SAA is described as a precursor of protein AA in secondary amyloidosis; other functions are speculative. AAG may play an immunoregulatory role as well as a role in binding a number of diverse drugs. In addition to clot formation, new data are described for binding of fibrinogen and fibrin to complement receptor type 3. Finally, the concentration of each protein is discussed in a wide variety of noninfectious and infectious disease states, particularly in connective tissue diseases. The quantification of the proteins during the course of various acute and chronic inflammatory disorders is useful in diagnosis, therapy, and in some cases, prognosis.

Disorders of the hemostatic system and the risk of the development of thrombotic and cardiovascular diseases: limitations of laboratory diagnosis

The relationship between hemostatic abnormalities and thrombotic and cardiovascular diseases is summarized. All known congenital and acquired abnormalities in the biochemistry of hemostasis are related to thrombotic and cardiovascular diseases in the way that would be expected on the basis of theories about the role of balances between coagulation and fibrinolysis and between activating and inhibiting factors. Notwithstanding the consistency between theory and observed abnormalities, a causal relationship between biochemical abnormality and clinical symptoms has been proved only in a limited number of situations, and it is possible that certain abnormalities only (or also) mark pathologic events. The limitations of laboratory diagnosis of hemostatic disorders in relation to hemostasis as a local process are discussed. It is proposed that more attention be paid to methods of evaluating the local aspects, for example, methods that assess reaction products in the circulation and that can provide an averaged message of the local phenomena. In addition, such methods can provide information about the dynamic balances in the hemostatic system, whereas historically more attention has been paid to the static balances in the potential of hemostatic processes.