Fibrinolytic activity and clotting factors in ischaemic heart disease in women

Relationship of coagulation and fibrinolytic variables with arterial structure and function in Africans

INTRODUCTION

Although both coagulation and fibrinolysis are associated with cardiovascular disease (CVD) the underlying nature and pathways of many of these associations are still unclear. Our aim was to determine which of the current or 5-year prior levels of total fibrinogen, fibrinogen γ', plasminogen activator inhibitor-1 (PAI-1act) and global fibrinolytic potential were the stronger determinant of arterial structure and function.

MATERIALS AND METHODS

This prospective study consisted of 2010 Africans over the age of 35 years with 5-year follow-up data available for 1288 participants. Cardiovascular measurements included arterial stiffness, blood pressure and carotid intima media thickness.

RESULTS

Fibrinogen γ' showed stronger associations with blood pressure than total fibrinogen also in the presence of other CVD risk factors. PAI-1act was positively associated with blood pressure both cross-sectionally and prospectively, with the longitudinal association being the stronger determinant, also after adjustment for known CVD risk factors. Clot lysis time (CLT) was positively associated, both prospectively and cross-sectionally, with intima media thickness and negatively with markers of arterial stiffness but not after adjustment for known CVD risk factors.

CONCLUSIONS

Fibrinogen γ' was more strongly associated with CVD function than total fibrinogen. PAI-1act was significantly associated with blood pressure with changes in PAI-1 levels preceding changes in blood pressure. Different mechanisms may be at play determining arterial wall stiffness/thickening and blood pressure as observed from the opposing associations with PAI-1act and CLT. CLT was not independently related to cardiovascular measures as its associations were weakened in the presence of other known CVD risk factors.

Evaluation of pre-analytical, demographic, behavioural and metabolic variables on fibrinolysis and haemostasis activation markers utilised to assess hypercoagulability

BACKGROUND

Measurement of some haemostatic factors and products formed during activation of haemostasis seems to be promising in the determination of hypercoagulability.

METHODS

The fibrinolytic variables euglobulin clot lysis time, tissue-type plasminogen activator, plasminogen activator inhibitor-1 and the haemostasis activation markers prothrombin fragment 1+2, thrombin-antithrombin complex and D-dimer were determined in 101 apparently healthy men and women aged 20-92 years (58+/-18 years, mean+/-SD) to establish variability due to several demographic, behavioural and metabolic factors.

RESULTS

None of the fibrinolytic variables were affected by smoking, while tissue-type plasminogen activator antigen was significantly lower in women compared to men. Multiple regression analysis revealed several independent associations between tissue-type plasminogen activator, plasminogen activator inhibitor, body mass index and lipid levels, describing up to 40% of the variance in fibrinolytic variables. For haemostasis activation markers, no gender difference or effect of smoking was observed. Only D-dimer was independently associated with age. The haemostasis activation markers determined proved to be extremely sensitive to blood sampling procedure and were significantly higher in samples obtained by an untrained nurse compared to a trained nurse.

CONCLUSIONS

Fibrinolytic variables are predominantly modulated by age, body mass index and blood lipids, while haemostasis activation markers are mainly un-influenced by these factors.

Cardiovascular complications of obesity in adolescents

Obesity is an increasingly important worldwide health problem, representing the major risk factor for coronary heart disease. The increase in the prevalence of obesity, particularly among younger age groups, is likely to have long-term implications for cardiovascular disease (CVD) in the years to come, especially at a young age. Obesity plays a central role in the insulin resistance (IR) syndrome and increases the risk of atherosclerotic CVD. The present review will examine the relationships among cardiovascular risk (CVR) factors during the childhood-adolescence-adulthood transition. In fact, the relation between obesity, in particular visceral obesity and CVD, appears to develop at a relatively young age. The foremost physical consequence of obesity is atherosclerotic CVD, and an intriguing example of obesity-related cardiovascular complications affecting young women is the polycystic ovary syndrome (PCOS).

Air Pollution and Hospital Admissions for Ischemic Heart Diseases among Individuals 64+ Years of Age Residing in Seoul, Korea

There is increased evidence that air pollution may be associated with cardiovascular disease. The authors' prior investigations on the association between air pollution exposure and stroke mortality led to the current study, which was conducted to assess the effects of ambient air pollution on ischemic cardiovascular diseases among the elderly population (i.e., males and females 64+ yr of age) in Seoul, Korea. The authors estimated the relative risks of hospitalization associated with an interquartile range (IQR) increase in pollution concentrations; a generalized additive Poisson model was used to conduct a time-series analysis of the counts. The concentrations of ambient air pollutants were lower than the current recommendations for air quality in Korea. The estimated relative risks of hospitalization associated with an IQR were 1.05 (95% confidence interval [CI] = 1.01, 1.10) for particulate matter less than or equal to 10 microm in diameter (PM10) (IQR = 40.4 microg/m3); 1.10 (95% CI = 1.05, 1.15) for ozone (IQR = 21.7 ppb); 1.08 (95% CI = 1.03, 1.14) for nitrogen dioxide (IQR = 14.6 ppb); 1.07 (95% CI = 1.01, 1.13) for carbon monoxide (IQR = 1.0 ppm); and 0.95 (95% CI = 0.90, 1.01) for sulfur dioxide (IQR = 4.4 ppb). The authors observed that sulfur dioxide was a significant risk factor for ischemic heart disease-related hospital admissions during the summer months (i.e., June, July, and August) (relative risk = 1.32; 95% CI = 1.08, 1.62). Hospital admissions for ischemic heart diseases were associated significantly with daily variations in levels of ambient air pollutants. These findings may provide new insights into the possible pathologic mechanisms involving air pollutants, and they support the hypothesis that the elderly appear to be at particular risk from the effects of air pollution, at pollutant levels lower than the standards commonly adopted by many countries.

Effects of regular ingestion of black tea on haemostasis and cell adhesion molecules in humans

OBJECTIVE

To assess the effects in humans of regular ingestion of black tea on haemostasis-related variables and cell adhesion molecules.

DESIGN

Twenty-two subjects were recruited from the general population to a randomised-controlled crossover study. Subjects stopped drinking tea, apart from that provided, for the duration of the study. During a 4-week baseline period all subjects drank 5 cups/day (250 ml) of hot water. The effects of 5 cups/day of black tea for 4 weeks were then compared with hot water. Platelet aggregation in response to three doses of collagen and ADP, plasma concentrations of coagulation and fibrinolytic factors (fibrinogen, factor VII, tPA, PAI-1) and plasma concentrations of cell adhesion molecules (soluble P-selectin, E-selectin, ICAM-1, VCAM-1) were assessed twice, one week apart, at the end of each period. Twenty-four hour urinary concentration of 4-O-methylgallic acid (4OMGA), assessed once at the end of each period, was used as a marker of black tea polyphenol intake.

RESULTS

The 24 h urinary excretion of 4OMGA was increased during regular ingestion of black tea in comparison to hot water (P<0.0001). Black tea resulted in lower soluble P-selectin (P=0.01) in comparison to hot water, but did not influence other adhesion molecules. Soluble P-selectin was significantly correlated with mean collagen-stimulated platelet aggregation at baseline (r=0.61, P=0.003), and during regular ingestion of hot water (r=0.70, P<0.0001) and black tea (r=0.51, P=0.01). However, platelet aggregation was not different between the black tea and hot water periods for collagen- or ADP-stimulated aggregation at any dose. Coagulation and fibrinolytic factors were also not different between periods.

CONCLUSIONS

The effect of black tea on soluble P-selectin provides a potential mechanism for cardiovascular benefits of regular ingestion of tea.

SPONSORSHIP

This study was supported by grants from the Tea Trade Health Research Association and the National Heart Foundation of Australia.

Prospective study of fibrinolytic factors and incident coronary heart disease: the Atherosclerosis Risk in Communities (ARIC) Study

The fibrinolytic system may play a role in the pathogenesis of coronary heart disease (CHD), but existing prospective studies have not consistently shown an independent association between fibrinolytic factors and CHD. None has reported an association between plasminogen and CHD incidence. In the prospective Atherosclerosis Risk in Communities (ARIC) Study of middle-aged adults, we examined the association of incident CHD with several fibrinolytic factors: tissue plasminogen activator antigen, plasminogen activator inhibitor-1, plasminogen, and fibrin fragment D-dimer as well as a marker of coagulation activation (prothrombin fragment F1.2). We measured these in stored baseline plasma samples of 326 subjects who developed CHD and, for comparison, a stratified random sample of the entire cohort (n=720). Tissue plasminogen activator and plasminogen activator inhibitor-1 antigen levels were associated positively with CHD incidence in analyses adjusted for age, race, and sex but were not associated with CHD after adjustment for other risk factors. Plasminogen and D-dimer levels were associated positively and independently with CHD incidence; the multivariable-adjusted relative risks (95% CIs) for the highest versus lowest quintiles were 2.20 (1.2 to 4.2) for plasminogen and 4.21 (1.9 to 9.6) for D-dimer. F1.2 was not associated with CHD incidence. Our findings lend support for a link between fibrinolytic factors and CHD incidence. A positive association between plasminogen and CHD is seemingly opposite the direction expected but may reflect a compensatory response to impaired plasminogen activation in subjects prone to CHD.

Haemostatic function, arterial disease and the prevention of arterial thrombosis

Recent years have seen the expansion of information linking raised plasma levels of individual clotting factors and evidence of disturbances of fibrinolytic activity with the risk of thrombotic manifestations of arterial disease, both in community-based, apparently healthy populations and in patients with known atherosclerosis. Some of these prothrombotic changes in the haemostatic system may result partly from underlying chronic inflammation or acute infection and may, in turn, contribute substantially to the thrombotic risk which accompanies these underlying processes. The importance of the coagulation system in the pathogenesis of arterial thrombosis is further illustrated by the benefit in the Thrombosis Prevention Trial of low-intensity, dose-adjusted warfarin in the primary prevention of ischaemic heart disease. Clinical trials of bezafibrate, which is being used for its fibrinogen-lowering as well as lipid-modifying properties, are in progress.

Fibrinogen and cardiovascular risk

The hypothesis that fibrinogen is closely related to cardiovascular risk has been strengthened through the results of various lines of research, which this review will aim to unravel. Several prospective epidemiological studies convincingly show elevated fibrinogen to represent a major, independent cardiovascular risk factor. Cross-sectional studies strongly associate fibrinogen and conventional cardiovascular risk factors. Clinical cohort studies demonstrate that increased fibrinogen is also a risk factor for the sequelae of cardiovascular disease. Our knowledge about the determinants of the variable plasma level of fibrinogen in health and disease is incomplete. Understanding of the mechanisms that might be involved in the atherothrombogenic action of fibrinogen is also fragmentary. Fibrinogen strongly affects blood coagulation, blood rheology and platelet aggregation. In addition, it has direct effects on the vascular wall and is a prominent acute phase reactant. All of these phenomena might constitute pathophysiological mechanisms involved in the association between fibrinogen and cardiovascular events. Their relative importance is unclear at present. Even though many crucial questions await conclusive answers, little doubt exists that fibrinogen represents a major, independent risk factor.

Effects of hormone replacement therapies on fibrinogen and plasma viscosity in postmenopausal women

In women, cardiovascular morbidity and mortality sharply increase after the onset of menopause. There is substantial evidence that hormone replacement therapy (HRT) may decrease the risk of coronary heart disease (CHD); however, the mechanisms of this preventive effect are unclear. We investigated the association between HRT and plasma viscosity as well as fibrinogen levels in postmenopausal women of a population-based sample (n=300, age 52-65 years). A total of 94 women used HRT; of these, 50 took oestrogen monotherapy and 44 used oestrogen-progesterone combinations. HRT was associated with significantly lower fibrinogen concentrations (2.32 v 2.68 g/l, P<0.001) and decreased plasma viscosity (1.147 v 1.176 mPa/s, P=0.01). Multivariate analyses controlling simultaneously for the effects of age, smoking, body mass index, and use of diuretics confirmed decreased fibrinogen and plasma viscosity values in women using HRT. A trend towards lower plasma viscosity (1.139 v 1.160 mPa/s) and plasma fibrinogen (2.28 v 2.44 g/l) was observed in women on oestrogen-progesterone combinations as compared with oestrogen monotherapy users: however, after controlling for the above-mentioned variables these differences were not statistically significant. This study demonstrates decreased plasma viscosity in women on HRT. Improved rheology offers a mechanism by which HRT lowers the risk of CHD in postmenopausal women.

The plasminogen activator system in women with polycystic ovary syndrome

OBJECTIVE

To evaluate the plasminogen activator system in women with polycystic ovary syndrome (PCOS).

DESIGN

Case-control study.

SETTING

A district general hospital in the United Kingdom.

PATIENT(S)

Eleven women with PCOS and 12 controls.

INTERVENTION(S)

Venipunctures for assays of the plasminogen activator system.

MAIN OUTCOME MEASURE(S)

Euglobulin clot lysis times, plasminogen activator inhibitor 1 (PAI-1) activity, fibrinogen, plasminogen, and alpha-2 antiplasmin concentrations in plasma.

RESULT(S)

Women with PCOS may had a significantly longer euglobulin clot lysis time (mean +/- SD, 389 +/- 164 minutes vs. 220 +/- 110 minutes), a higher PAI-1 activity (mean +/- SD, 19.7 +/- 12 arbitrary units (AU) per mL vs. 10.9 +/- 7.9 AU/mL), and a higher fibrinogen level (mean +/- SD, 4.02 +/- 0.64 g/L vs. 3.15 +/- 0.6 g/L) compared to controls.

CONCLUSION(S)

Women with the PCOS may have an imbalance in the plasminogen activator system that is tilted toward a reduced production of the proteolytic enzyme plasmin. Systemically, this may increase their risk of cardiovascular disease, but at cellular level in the ovaries, it may result in impaired follicular rupture and anovulation.