Effects of progestogens on thrombosis and atherosclerosis.
(25/1215)
In contrast with past practice, current hormone replacement usually includes a combination of oestrogens and progestogens. In this article, we review the effect of progestins on haemostasis and in the development of atherosclerosis. Second-generation progestogens produce minor haemostatic changes, and in lipid metabolism they decrease the synthesis of triglycerides and very low density lipoproteins (VLDL) and stimulate hepatic lipoprotein lipase. In combination, progestogens modify the effect of oestrogens on hepatic metabolism, endothelium and platelets. Several new progestins (known as third-generation) have less effect on lipid profiles. In vessel walls, animal studies have shown that progestogens are able dose-dependently to inhibit the beneficial effect of oestrogen without significant changes in lipid concentrations. The endothelium-dependent vasoconstrictor effect of progestogens on the arterial wall has been also evaluated. Large epidemiological studies show a two-fold increase in risk of venous thromboembolism with the use of third-generation progestins. Regarding the risk of myocardial infarction, no definite evidence is yet available with the use of third-generation progestins. The clinical consequence is therefore that second-generation progestins are the first choice in prescription for first-time users. (+info)
Effects of progestins on cardiovascular diseases: the haemostatic system.
(26/1215)
The effect of progestin-only therapy on the haemostatic system has mainly been studied in premenopausal women. Although these studies are difficult to compare, most authors agree that there is no consistent pattern of effects on haemostasis. Oestrogen-progestin combinations have been extensively studied in pre- (combined oral contraceptives) and postmenopausal women (sequential and continuous combined hormone replacement therapy), but mostly with emphasis on the effects of oestrogens. Comparative studies into the differential effects of progestins in combined preparations are scarce. Based on these studies, there is evidence for modifying effects of progestins on oestrogen-induced changes, particularly on fibrinogen, factor VII and the fibrinolytic system. The modifying effects appear to vary among certain progestins, the variation being most likely due to differential effects on lipid metabolism. The clinical interpretation of steroid-induced effects on the haemostatic system is difficult. Retrospective analyses linking certain patterns of haemostatic regulation to the risk of venous or arterial vascular diseases are subject to bias, and no interventional studies are yet available. In the absence of such prospective studies and well-designed comparative studies, the available data do not support the notion of a superiority of certain progestins with regard to cardiovascular risks of combined preparations. (+info)
Changes of hemostasis, endogenous fibrinolysis, platelet activation and endothelins after percutaneous transluminal coronary angioplasty in patients with stable angina.
(27/1215)
OBJECTIVES: This study investigated parameters of endogenous fibrinolysis, activation of coagulation and platelets, and endothelin levels before and after elective percutaneous transluminal coronary angioplasty (PTCA) in patients with stable coronary artery disease (CAD). BACKGROUND: Abrupt vessel closure is a serious short-term complication after PTCA and is often unforeseeable. Detailed insight into the effect of PTCA on hemostasis, platelets and the release of vasoconstrictive substances, which are among the mainly discussed mechanisms of abrupt vessel closure, is needed to enhance the safety of coronary intervention. METHODS: Plasma levels of markers of platelet activity, coagulation, endogenous fibrinolysis and endothelins were determined in 20 patients with stable CAD undergoing elective PTCA. The blood specimens were drawn before, immediately after, 1 h after intervention and on the next morning. RESULTS: All patients showed an initially uncomplicated PTCA. Regarding the efficacy of anticoagulation after receiving 15.000 IU heparin during PTCA, two groups were compared. In eight patients with ineffective anticoagulation production of thrombin and platelet activation directly after and 1 h after PTCA was significantly higher compared with 12 patients with effective anticoagulation. Despite the strong activation of coagulation, only a low fibrinolytic response could be observed. Endothelins rose significantly after PTCA in both groups but stayed longer on higher levels in patients with distinct thrombin generation. Three of the eight patients without sufficient heparin treatment suffered abrupt vessel closure. CONCLUSIONS: Initially uncomplicated dilation of coronary arteries leads to systemically measurable activation of coagulation and platelets in patients with ineffective doses of heparin and release of endothelins in all patients. Therefore, individual adjustment of anticoagulation and platelet inhibition in combination with effective antivasospastic substances are needed in every patient before, during and after initially uncomplicated PTCA to prevent this serious complication. (+info)
Prospective study of markers of hemostatic function with risk of ischemic stroke. The Atherosclerosis Risk in Communities (ARIC) Study Investigators.
(28/1215)
BACKGROUND: Several markers of hemostatic function and inflammation have been associated with increased risk of coronary heart disease, but prospective evidence for their role in ischemic stroke is scant. METHODS AND RESULTS: The Atherosclerosis Risk in Communities (ARIC) Study measured several of these markers in more than 14 700 participants 45 to 64 years old who were free of cardiovascular disease and were followed up for 6 to 9 years for occurrence of ischemic stroke (n=191). There was no apparent association between ischemic stroke incidence and factor VIIc, antithrombin III, platelet count, or activated partial thromboplastin time. After adjustment for multiple cardiovascular risk factors, von Willebrand factor, factor VIIIc, fibrinogen, and white blood cell count were positively associated and protein C was negatively but nonsignificantly associated with ischemic stroke incidence in regression analyses based on either continuous variables or fourths of the variable distributions. The adjusted relative risk (and 95% CI) for ischemic stroke in those in the highest versus lowest fourth were: von Willebrand factor, 1.71 (1.1 to 2.7); factor VIIIc, 1.93 (1.2 to 3.1); white blood cell count, 1.50 (0.9 to 2.4); fibrinogen, 1.26 (0.8 to 2.0); and protein C, 0.65 (0.4 to 1.0). CONCLUSIONS: This study offers modest support for the hypothesis that some markers of hemostatic function and inflammation can identify groups of middle-aged adults at increased risk of stroke. These factors may play a role in the pathogenesis of ischemic stroke. (+info)
Detection of a novel plasma serine protease during purification of vitamin K-dependent coagulation factors.
(29/1215)
A novel serine protease (PHBSP) was purified from human plasma by two chromatographic steps with a final yield of 1.6 mg/l plasma. The protease consists of two disulfide-bridged chains of about 50 and 30 kDa with the light chain containing the active site of the enzyme. NH2-terminal sequence analysis revealed identity to the deduced amino acid sequence of HGFA-like mRNA. The activity of PHBSP is strongly dependent on Ca2+ ions and is efficiently inhibited by alpha2-antiplasmin and aprotinin. Possible functions of PHBSP in the hemostatic system are discussed. (+info)
Cardiovascular morbidity and endothelial dysfunction in chronic haemodialysis patients: is homocyst(e)ine the missing link?
(30/1215)
BACKGROUND: Haemodialysis patients exhibit an excessive burden of atherothrombotic disease, which is not explained adequately by traditional risk factors. Hyperhomocyst(e)inaemia, a consistent finding in uraemic patients, is now widely recognized as an independent risk factor for vascular disease. The aim of this study was to examine the hypothesis that hyperhomocyst(e)inaemia is associated with cardiovascular complications in dialysed patients. METHODS: In a cohort of 63 stable chronic haemodialysis patients, we examined the causal relationship between hyperhomocyst(e)inaemia and vascular endothelial and haemostatic function. All their markers were determined before and after an 8-week course of a 10 mg per day oral folate supplementation, a manoeuvre known to decrease hyperhomocyst(e)inaemia in uraemic patients. RESULTS: History of at least one cardiovascular atherothrombotic event was present in 47.6% of the haemodialysed patients, and radiographic evidence of vascular calcifications in 70%. Hyperhomocyst(e)inaemia was found in all patients, averaging 3.5-fold the upper limit of normal values (P<0.001), despite the lack of clinical and biological evidence of malnutrition. Fibrinogen, von Willebrand factor and plasminogen activator inhibitor type 1, but not endothelin 1, were significantly higher in haemodialysis patients than in controls. After adjustment for all variables, past history of cardiovascular events was independently associated with higher levels of homocyst(e)inaemia only (odds ratio (OR) 1.06; 95% confidence interval (CI) 1.01-1.12; P<0.026). The presence of aortic calcifications was independently and significantly associated with age (OR 1.37; 95% CI 1.07-1.75; P<0.025), homocyst(e)inaemia (OR 1.14; 95% CI 1.02-1.27; P<0.05) and fibrinogen concentration only (OR 9.74; 95% CI 1.25-75.2; P<0.05). None of the endothelial haemostatic factors was, however, related to homocyst(e)ine levels. Mid-term folate supplementation decreased plasma homocyst(e)ine levels significantly without achieving normal values. No significant change of endothelial-haemostatic markers was observed, however, despite the drop in plasma homocyst(e)ine. CONCLUSIONS: Hyperhomocyst(e)inaemia is associated with increased cardiovascular risk in haemodialysis patients. Folate supplementation was partially effective in lowering hyperhomocyst(e)inaemia, but its usefulness in terms of reduction in cardiovascular morbidity and mortality remains to be determined in prospective trials. (+info)
Consequences of acute normovolaemic haemodilution on haemostasis during major orthopaedic surgery.
(31/1215)
Acute preoperative normovolaemic haemodilution (NHD) is an accepted tool for reducing allogeneic blood transfusion requirements during surgery. At present, little is known of its impact on haemostasis. We have investigated the consequences of NHD on haemostasis by comparing conventional global tests (prothrombin time (PT), activated partial thromboplastin time (aPTT) with more specific measures of coagulation (prothrombin fragment 1 + 2 (F 1 + 2), thrombin-antithrombin III complex (TAT) and fibrinolysis (D-dimer (DD), plasmin-alpha 2-antiplasmin complex (PAP)). Blood samples were collected from two groups (NHD and controls) undergoing elective spinal surgery or pelvic osteotomy until day 3 after operation. The conventional global tests remained within normal limits: there were no significant differences between groups. Although surgery induced significant increases in the more specific measures of coagulation and fibrinolysis, there were no differences between NHD and control patients. Major orthopaedic surgery strongly activates coagulation and fibrinolysis. As the degree of these alterations was similar in haemodiluted and control patients, we suggest that acute preoperative normovolaemic haemodilution itself does not appear to be associated with greater perioperative disturbances in haemostasis. (+info)
Evaluation of the effect of storage at -70 degrees C for six months on hemostatic function testing in dogs.
(32/1215)
Freezing is a routine method of storage for plasma that is to be used in evaluating certain aspects of hemostatic function in many species. The purpose of this study was to evaluate the effect of storage at -70 degrees C for 6 mo on canine plasma samples. On fresh and frozen plasma from 12 clinically healthy dogs, prothrombin time, activated partial thromboplastin time, thrombin clotting time, fibrinogen determination, antithrombin III activity, fragment D and E assay, and protamine sulfate test were performed. Clinical agreement analysis was utilized to determine the effect of such storage on all assays. Individual differences detected between fresh and frozen samples were all within 2 standard deviations of the mean difference. With the exception of the activated partial thromboplastin time, storing canine plasma at -70 degrees C for 6 mo has no significant effect on hemostatic function, as assessed by these tests. (+info)