An international and interregional comparison of haemostatic variables in the study of ischaemic heart disease. Report of a working group

Levels of haemostatic variables that may be involved in thrombogenesis have been compared in groups of men of similar mean age in communities at very low (Gambia), high (England and Czechoslovakia) or very high (Scotland and Finland) risk of ischaemic heart disease (IHD). There was a consistent gradient of higher factor VII levels with higher IHD risk and also suggestive gradients in the case of two other vitamin K dependent factors, factors II and X. Mean platelet counts were lower and mean fibrinolytic activity was greater in Gambian men than in European men. There was a suggestive though not entirely consistent association between mean fibrinogen levels and IHD risk in the groups from IHD-endemic countries. The results as a whole, and particularly those on factor VII, strengthen the case for the increasingly detailed epidemiological as well as laboratory investigation of the role of the haemostatic system in thrombogenesis and IHD.

Fibrinogen in ischaemic heart disease

Fibrinogen contributes to both pathological and clinical manifestations of ischaemic heart disease (IHD). Several cross-sectional angiographic studies have shown correlations between the fibrinogen level and the extent of coronary artery disease. The largest of these studies suggests that this relationship is due mainly to luminal occlusion, strengthening the evidence that high fibrinogen levels are thrombogenic. The growing number of prospective studies that have included fibrinogen measurements consistently show a direct, independent and statistically significant association between fibrinogen level and the subsequent incidence of IHD, this association being about as strong as the relation between cholesterol and IHD, for example. The fibrinogen level is also associated with the recurrence of IHD in those who have survived a myocardial infarction and with the onset and recurrence or progression of cerebrovascular disease and lower extremity arterial disease. Besides a contribution to coronary artery changes, high fibrinogen levels predispose to IHD through influences on blood and plasma viscosity, platelet aggregability and the amount of fibrin produced when coagulation is initiated. Progress towards the standardization of methods for measuring fibrinogen increasingly justifies its inclusion in the IHD risk profile. Establishing the value of agents that lower fibrinogen levels is now a high research priority, mainly for clinical reasons but also as part of the evidence for clarifying the nature of the association of raised levels with arterial disease.

An association between the factor VII coagulant activity and thrombin activity induced by surface/cold exposure of normal human plasma

To test whether factor VII activation correlated with the generation of thrombin activity when plasma was exposed to a glass surface and reduced temperature, an association was sought between the changes in factor VII clotting activity (VIIc) and fibrinopeptide A concentration (an index of thrombin activity) in platelet-poor citrated plasma from 42 healthy adults. The Spearman rank correlation (rs) between responses was 0.82 (P less than 0.001). The VIIc assay response to surface/cold exposure was unaffected when thrombin was suppressed by hirudin. An assay for factor VII activity based upon its activation of tritiated factor X revealed an association between the increase in fibrinopeptide A concentration and reduction in functional factor VII concentration during activation of a subset of 22 plasma samples (rs = -0.62; P = 0.003). This loss of functional factor VII was probably due to conversion of active factor VII to its non-functional end-product by factor Xa. The results suggest that VIIc is an index of flux within the coagulation system and support the hypothesis that a high VIIc is an indicator of a hypercoagulable state.

Associations of plasma fibrinogen and factor VII clotting activity with coronary heart disease and stroke: prospective cohort study from the screening phase of the Thrombosis Prevention Trial

BACKGROUND

As with 'conventional' risk factors such as cholesterol and smoking, there is a need for large, long-term prospective studies on hemostatic factors.

OBJECTIVES

To investigate the prospective relationship of fibrinogen and factor VII clotting activity (FVIIc) with risk of coronary heart disease (CHD) and stroke in a study with a large number of outcomes over a period of 15 years.

PATIENTS/METHODS

A cohort of 22 715 men aged 45-69 years was screened for participation in the Thrombosis Prevention Trial. Men were followed up for fatal and non-fatal CHD and stroke events. There were 1515 CHD events (933 CHD deaths) and 391 strokes (180 stroke deaths). Hazard ratios (HRs) and 95% confidence intervals are expressed per standardized increase in log fibrinogen and log FVIIc, adjusting for age, trial treatment group, conventional CHD risk factors and regression dilution bias.

RESULTS

Hazard ratios for fibrinogen were 1.52 (1.37-1.70) for all CHD events, and 1.36 (1.09-1.69) for all strokes. Exclusion of events within the first 10 years showed a persistent association between CHD and fibrinogen, with an adjusted HR of 1.93 (1.42-2.64). The HRs for FVIIc, adjusting for age and trial treatment, were 1.07 (1.01-1.12) for all CHD events and 1.07 (0.97-1.20) for all strokes, and the fully adjusted HRs were, respectively, 0.97 (0.84-1.05) and 1.07 (0.85-1.33).

CONCLUSIONS

The persisting association between fibrinogen and CHD beyond 10 years may imply a causal effect. There is a small effect of FVIIc on CHD, after adjustment for age and trial treatment, but no association independent of other risk factors.

Ethnic differences in blood pressure with observations on noradrenaline and renin. 1. A working population

115 factory workers (62 white, 53 black) were studied with measurements of blood pressure, plasma noradrenaline concentration, and plasma renin activity. Blood pressure was higher in blacks than in whites. There were no ethnic differences in plasma noradrenaline, which increased with age, but was not related to blood pressure. Mean plasma renin activity was 55% lower in blacks than whites and this difference was not related to differences in sodium intake. There were no associations between renin and noradrenaline, or between renin and blood pressure.

Skinfold thickness and cardiovascular risk factors

The relation of blood pressure, serum cholesterol, plasma fibrinogen, and coagulation factor VIIc with skinfold thickness at four sites (forearm, triceps, suprailiac, and subscapular) was examined in 2,948 white participants in the Northwick Park Heart Study. When considered separately, all four skinfolds were significantly associated with the four cardiovascular risk factors in males. Of the two limb skinfolds, forearm was consistently more strongly associated than triceps with the risk factors. The magnitude of the association between forearm skinfold and the risk factors was similar to that of the two trunk skinfolds, suprailiac and subscapular. Multiple regression analysis suggested an independent association of forearm skinfold with cholesterol and blood pressure in males when the other skinfolds were taken into account. There was no consistent difference in the strength of the associations of the two trunk skinfolds with the risk factors. With the exception of systolic blood pressure, the associations between the cardiovascular risk factors and skinfold thickness in males were stronger at younger ages. In the case of females the findings were somewhat different. The associations with the four risk factors were consistently stronger for the two trunk skinfolds than the limb skinfolds. Triceps was somewhat more strongly associated with the risk factors than forearm skinfold except for plasma fibrinogen. Thus there are sex differences in the association of the distribution of subcutaneous fat with cardiovascular risk factors.

Hypercoagulability and ischaemic heart disease

Thrombogenesis is increasingly recognised as an immediate cause of most major clinical episodes of ischaemic heart disease (IHD) and the haemostatic system makes a significant contribution to the development of atheroma. It is therefore important to consider how far concepts of increased thrombotic tendency and hypercoagulability can be demonstrated in reality. A number of general observations do suggest that characteristics of the circulating blood influence the course of events in IHD--for example, the occurrence of IHD or stroke in young women using oral contraceptives in whom advanced arterial wall changes are not a feature. Epidemiologically, the coagulation system has been more rewarding than the study of platelets. The Northwick Park Heart Study (NPHS) has demonstrated a strong relationship between the level of factor VII activity and the later incidence of IHD. Several biochemical characteristics of factor VII suggest that this relationship may well be one of cause and effect. There is growing evidence that high levels of factor VII activity lead to high levels of thrombin production. In addition to NPHS, three other prospective studies have shown an association between high levels of plasma fibrinogen and IHD incidence. Again, there are several reasons for believing that this association, too, is of pathogenetic significance. Dietary fat intake is a major determinant of the factor VII activity level, and smoking of the fibrinogen level. Hypercoagulability determining IHD is best defined, on present evidence, as over-activity of procoagulatory influences (whereas hypercoagulability leading to venous thrombosis is predominantly manifested as underactivity of natural defence mechanisms).(ABSTRACT TRUNCATED AT 250 WORDS)

Circulating levels of coagulation and inflammation markers and cancer risks: individual participant analysis of data from three long-term cohorts

BACKGROUND

Basic and clinical research support the hypothesis that activation of the coagulation and inflammation pathways may affect cancer onset, but there is limited epidemiological data to support this.

METHODS

We examined a large range of haemostatic and inflammation markers, including fibrinogen, in 19 303 male participants from three English cohorts followed for up to 30 years. After excluding the first 3 years of follow-up, 2908 incident cancers were accrued. Competing risk models were fitted to estimate rate ratios (RRs) for cancer incidence, adjusting for age and other confounders.

RESULTS

Baseline white blood cell (WBC) count and circulating levels of fibrinogen, C-reactive protein (CRP), factor VII antigen (VIIa) and prothrombin fragment F1.2 were positively associated with risk of smoking-related cancers, particularly lung cancer. The magnitude of these associations was highest for persistently raised fibrinogen levels. There was, however, substantial confounding by smoking with risk being fully (WBC, CRP and VIIa) or partially (fibrinogen) removed after adjustment. The pooled RRs (95% confidence interval) per one standard deviation increase in fibrinogen levels before and after adjustment for smoking habits were 1.23 (1.12, 1.36) and 1.12 (1.05, 1.20), respectively. The fibrinogen associations were present only among current smokers at entry. The effect of smoking on smoking-related cancers was partly mediated by fibrinogen levels.

CONCLUSIONS

Our results are consistent with elevated circulating levels of fibrinogen and F1.2 being predictors of risk of smoking-related cancers. Further research is necessary to clarify whether elevated levels of fibrinogen and F1.2 are causally relevant or simply correlates of the smoking-cancer association.

Is there any evidence for a protective effect of antithrombotic medication on cognitive function in men at risk of cardiovascular disease? Some preliminary findings

To explore whether antithrombotic medication may protect against cognitive decline, tests of verbal memory, attention, abstract reasoning, verbal fluency, and mental flexibility were administered to 405 men at risk of cardiovascular disease. These subjects were a subgroup of those who had been participating in a randomised double blind factorial trial of low dose aspirin (75 mg daily) and low intensity oral anticoagulation with warfarin (international normalised ratio of 1.5) at 35 general practices across the United Kingdom for at least five years, were at least 55 years old at trial entry, and had been randomly allocated to one of four groups: active warfarin and active aspirin, active warfarin and placebo aspirin, placebo warfarin and active aspirin, and double placebo. Verbal fluency and mental flexibility were significantly better in subjects taking antithrombotic medication than in subjects taking placebo. Aspirin may have contributed more than warfarin to any beneficial effect. These results provide tentative evidence that antithrombotic medication may protect cognitive function in men at risk of cardiovascular disease.

Haemostatic changes following surgery

Changes in factors V, VII and VIII and in fibrinogen were studied in 32 patients undergoing major abdominal surgery. Mean levels of factors V and VII were similar to population-based values preoperatively. Factor V fell following elective surgery and then rose above the mean pre-operative level before returning to it by the tenth post-operative day. Factor VII fell following both elective and emergency surgery and tended to remain depressed throughout the post-operative period. Pre-operative values of factor VIII and fibrinogen were higher than population-based values and higher in the emergency than in waiting-list patients. Both factor VIII and fibrinogen rose following elective surgery but no statistically significant change was seen following emergency surgery. The uncomplicated conditions leading to elective surgery, the acute complications leading to emergency surgery, and surgery itself may each have contributed to increases in factor VIII and fibrinogen levels, whereas the fall in factors V and VII was largely related to surgery itself. The findings may help in the interpretation of associations between clotting factors and thrombotic disease, particularly in the case of factor VII.

Risk factors for stroke and myocardial infarction in women in the United Kingdom as assessed in general practice: a case-control study

Data available in the United Kingdom through the Medical Research Council's General Practice Research Framework were recorded in a study of 603 women aged 45-69 with confirmed diagnoses of stroke or myocardial infarction, each matched by age with two controls. Current cigarette smoking and a family history of myocardial infarction were both strongly associated with the risk of stroke and myocardial infarction, with relative risks of 2.47 (95% confidence interval 1.89 to 3.23) and 1.93 (95% confidence interval 1.52 to 2.44) respectively. The relative risks associated with past smoking decreased according to the length of time since stopping smoking. A family history of stroke was not significantly related to the risk of stroke or myocardial infarction. Single women had a lower risk of stroke and myocardial infarction than married women (relative risk 0.49), but parity, past use of oral contraceptives, and menopausal state were not significantly related to the risk of stroke and myocardial infarction in this study. Other characteristics that were identified as risk factors either for subsequent stroke or for myocardial infarction included not only hypertension, diabetes, and past histories of stroke and myocardial infarction, but also past histories of gynaecological cancer and of venous thrombosis. The association with venous thrombosis may indicate the importance of the haemostatic system in a common pathogenesis of venous thrombosis and myocardial infarction.

Effects of progestogens on the cardiovascular system

The progestogenic component of combined oral contraceptives (OCs) may contribute to the increased risk of stroke and ischemic heart disease in women who take these preparations. This effect is likely to be mediated, at least in part, through elevators in blood pressure. The progestogenic component of OCs does not appear to influence the risk of venous thromboembolism. In terms of reducing the risks of arterial disease in women taking OCs, the safest preparations will be those which minimize the dose of both estrogen and progestogen.

Arterial disease risk factors and angiographic evidence of atheroma of the carotid artery

We conducted a prospective study of serial intravenous digital subtraction angiography to determine the relation of arterial disease risk factors and hemostatic variables with the presence of visible atheroma at the carotid bifurcation. Of the 492 patients with cerebrovascular disease or ischemic heart disease who entered the study, 354 had hematologic studies, including platelet aggregation in 230. Abnormal angiograms were associated with greater age, treated hypertension, current smoking, and lower hemoglobin levels but with higher uric acid, factor VIII, and fibrinogen concentrations. In patients presenting with isolated transient ischemic attacks, abnormal angiograms were also associated with higher levels of cholesterol and triglycerides. To study atheroma progression, the 230 patients with complete data at entry were recalled 2 years later. Repeat angiography in 209 patients showed progression of visible bifurcation disease in 13.4%. There was some evidence that progression was linked to higher age, hypertension, and more severe disease at entry, but further analysis was hampered by the small number of patients showing increased plaque size. The possible role of risk factors and hemostatic variables, especially fibrinogen, is discussed. Factors that did not correlate with progression of angiographically visible disease may also influence clinical end points by other mechanisms, such as thrombogenesis.

Blood pressure and the menstrual cycle

A retrospective analysis of data from 207 non-pregnant premenopausal women showed that the mean level of systolic blood pressure varied with the stage of the menstrual cycle, being higher on days 17-26, the part of the luteal phase during which the peak of progestogen levels develops, than during the luteal phase as a whole, and significantly higher than the mean for all other days of the cycle. The mean levels were 125.4 mmHg (SE 1.76) for days 17-26, 122.5 (SE 1.25) for days 15-28 and 120.1 (SE 1.07) for days 1-16, 27 and 28. This finding supported the hypothesis that endogenous progestogen might have a hypertensive effect, as does exogenous progestogen. However, a second study designed to confirm this finding failed to do so, showing no cyclical change in the level of blood pressure. The subjects in the first study may have been subject to greater psychological stress when the measurements were made than were those in the second, a possibility supported by the large difference in pressure between the two studies. The discrepancy between the two sets of results could be explained if the effect possibly associated with progestogen levels in the retrospective study was due not to a hypertensive action per se but to a progestogen-related increased reaction to stress.

Genetic determinants of the response to bezafibrate treatment in the lower extremity arterial disease event reduction (LEADER) trial

Genetic determinants of baseline levels and the fall in plasma triglyceride and fibrinogen levels in response to bezafibrate treatment were examined in 853 men taking part in the lower extremity arterial disease event reduction (LEADER) trial. Three polymorphisms in the peroxisome proliferator activated receptor alpha (PPARalpha) gene were investigated (L162V, G>A in intron 2 and G>C in intron 7), two in the apolipoprotein CIII (APOC3) gene (-482C>T and -455T>C) and one in the beta-fibrinogen (FIBB) gene (-455G>A). The presence of diabetes (n=158) was associated with 15% higher triglyceride levels at baseline compared to non-diabetics (n=654) (P<0.05). Among the diabetic group, carriers of the PPARalpha intron 7 C allele had 20% lower triglyceride levels compared to homozygotes for the common G allele (P<0.05), with a similar (non-significant) trend for the L162V polymorphism, which is in linkage disequilibrium with the intron 7 polymorphism. For the APOC3 gene, carriers of the -482T allele had 13% lower baseline triglyceride levels compared to -482C homozygotes (P<0.02), but no effect was observed with the -455T>C substitution. In the non-diabetic patients, the PPARalpha V162 allele was significantly associated with 9% higher baseline triglyceride levels (P<0.03) and a similar, but non-significant trend was seen for the intron 7 polymorphism. Overall, triglyceride levels fell by 26% with 3 months of bezafibrate treatment, and current smokers showed a poorer response compared to ex/non-smokers (23% fall compared to 28% P=0.03), but none of the genotypes examined had a significant influence on the magnitude of response. Carriers of the -455A polymorphism of the FIBB gene had, as expected, marginally higher baseline fibrinogen levels, 3.43 versus 3.36 g/l (P=0.055), but this polymorphism did not affect response to treatment. Overall, fibrinogen levels fell by 12%, with patients with the highest baseline fibrinogen levels showing the greatest decrease in response to bezafibrate. For both the intron 2 and the L162V polymorphisms of the PPARalpha gene there was a significant interaction (both P<0.01) between genotype and baseline levels of fibrinogen on the response of fibrinogen levels to bezafibrate, such that individuals carrying the rare alleles in the lowest tertile showed essentially no overall decrease compared to a 0.18 g/l fall in homozygotes for the common allele. Thus while these genotypes are a minor determinant of baseline triglyceride and fibrinogen levels, there is little evidence from this study that the magnitude of response to bezafibrate treatment in men with peripheral vascular disease is determined by variation at these loci.

Coronary artery disease and haemostatic variables in heterozygous familial hypercholesterolaemia

Haemostatic variables were measured in 61 patients with heterozygous familial hypercholesterolaemia, 32 of whom had evidence of coronary heart disease. Age adjusted mean concentrations of plasma fibrinogen and factor VIII were significantly higher in these patients than in the 29 patients without coronary heart disease, but there were no significant differences in serum lipid concentrations between the two groups. Comparisons in 30 patients taking and not taking lipid lowering drugs showed lower values for low density lipoprotein cholesterol, high density lipoprotein cholesterol and antithrombin III, and a higher high density lipoprotein ratio while receiving treatment. The results suggest that hypercoagulability may play a role in the pathogenesis of coronary heart disease in patients with familial hypercholesterolaemia.

Randomised trial of community-based centre versus conventional hospital management in treatment of alcoholism

151 problem drinkers (105 men and 46 women) were recruited from the general medical and psychiatric services of a district general hospital and were allocated randomly to a community-based day centre (ACCEPT) or standard hospital inpatient and outpatient services. 115 patients (79%) were followed up at 12 months. The group as a whole showed improvement in all outcome indices at the 3-month follow-up, and this was maintained at 6 and 12 months. Patients assigned to ACCEPT services claimed to have reduced their alcohol intake (55%) more than their hospital counterparts (37%), and this was confirmed by their informants. Patients referred from the psychiatric services reduced their alcohol intake more than those from general medical services. It is concluded that treatment at a community day centre is at least as cost effective as hospital treatment of alcohol abuse.