Eberhard F. Mammen

Oral contraceptives and blood coagulation: a critical review.

Based on epidemiologic data, women who take oral contraceptives seem to have an increased risk of developing thromboembolic disease. In order to explain this association, some studies have been undertaken to find abnormalities in the hemostasis system. Many conflicting test results have been reported, probably reflecting in part the technical difficulties in use of reliable, reproducible, and specific assay systems. None of the data obtained seems to be specific for users of oral contraceptive drugs, and none was found uniformly in all takers of the drugs. Many findings are probably unimportant from the overall point of view of the physiology of hemostasis. Unfortunately, there seems to be no test procedure or even combination of tests that will reliably predict which patient might develop a thromboembolic episode in association with oral contraceptives or in association with any other condition recognized as being a risk factor. Even in most patients who do have a thrombosis, the test procedures fail to signal this event with reliability and predictability. At this time, it is not known whether oral contraceptives do or do not trigger the hemostasis system to develop a thrombosis or by which mechanism they could trigger the event. Fortunately, only a very small number of women develop thrombosis in association with oral contraceptives.

Coagulation defects in liver disease.

A normally functioning hemostasis system is closely related to liver function. The liver parenchymal cells produce most of the factors and inhibitors of the clotting and fibrinolytic systems, and the RES of the liver greatly aids in the clearance of activation products. Hemostasis defects thus depend on the extent of liver damage. A wide spectrum of defects is found in patients with liver cirrhosis. Owing to impaired protein synthesis, most factors and inhibitors of the clotting and the fibrinolytic systems are markedly reduced. Additionally, abnormal vitamin K-dependent factor and fibrinogen molecules have been encountered. Most patients have hyperfibrinolysis that could be DIC in nature. Thrombocytopenia and thrombocytopathy are also found. Acute or chronic hepatocellular disease may display decreased vitamin K-dependent factor levels, especially factor VII and protein C, with other factors still being normal. If patients go into hepatic failure, the abnormalities resemble those found in liver cirrhosis. Vitamin K deficiency is associated with the production of poorly functioning vitamin K-dependent factors. All other hemostasis parameters are normal. Disturbances associated with liver surgeries again depend on the underlying liver problem. Peritoneovenous shunts (LeVeen) may lead to DIC; bleeding from partially resected liver surfaces is usually a mechanical problem. Severe bleeding is encountered with orthotopic liver transplantation. It is greatly influenced by the activation of the fibrinolytic system. This occurs during the anhepatic phase and during the reperfusion phase. The hyperfibrinolysis is mediated by an intense release of t-PA. Antifibrinolytic drugs, if used cautiously, have markedly reduced bleeding and thus reduced need for blood and blood product substitution.

Circadian variation in platelet function in healthy volunteers

Circadian variation in hemostatic factors may contribute to a higher frequency of cardiac events observed in the morning and with activity. Diurnal changes in these factors were investigated by measuring in vitro platelet aggregability in response to epinephrine and adenosine diphosphate together with beta-thromboglobulin and platelet factor 4 as indexes of in vivo platelet activation. Activation of coagulation was measured by thrombin-antithrombin III complexes and D-Dimers. Tests were performed in 9 normal healthy subjects. Circadian changes occurred in beta-thromboglobulin (p less than 0.05) and platelet factor 4 (p less than 0.06). Plasma levels of beta-thromboglobulin and platelet factor 4 were lowest with patients supine and resting at 7 and 8 A.M., and increased with activity, with peak levels achieved at 3 P.M. (p less than 0.01). Thrombin-antithrombin III complexes (p = 0.44), D-Dimer (p = 0.36) and in vitro platelet aggregability to adenosine diphosphate (p = 0.20) did not show diurnal variation. There was a trend toward circadian variation in vitro platelet aggregability to epinephrine, but these changes did not achieve statistical significance (p = 0.16). Circadian changes of in vivo release of beta-thromboglobulin and platelet factor 4 correlated to patient activity and not to the morning peaks in ischemic events. These data indicate that changes in platelet function and not in coagulation have a diurnal occurrence.

Preeclampsia, delivery, and the hemostatic system

To determine the effects of preeclampsia and delivery, the hemostatic system was evaluated before and 24 to 48 hours after delivery in 59 nulliparous patients without clinical signs of disseminated intravascular coagulation. Fifteen patients with mild preeclampsia and 18 with severe preeclampsia were compared with 26 pregnant control patients. Preeclampsia was associated with high fibronectin (p less than 0.001), low antithrombin III (p less than 0.001), and low alpha 2-antiplasmin (p less than 0.005), suggesting endothelial injury, clotting, and fibrinolysis, respectively. After delivery, fibronectin decreased only in preeclamptic patients (p less than 0.005); alpha 2-antiplasmin increased in all groups (p less than 0.001). Endothelial injury in preeclampsia appeared to resolve soon after delivery, which could contribute to the rapid clinical improvement noted in the early puerperium.

Platelet hyperaggregability in patients with chest pain and angiographically normal coronary arteries

Forty-one patients with chest pain and angiographically normal coronary arteries were studied for platelet abnormalities. Patients with conditions known or suspected to be associated with chest pain or platelet dysfunction were excluded. After coronary angiography and 2-week withdrawal from all medications, platelet aggregometry was performed using peripheral venous plasma samples and 3 concentrations of adenosine diphosphate, 2.34, 1.17 and 0.58 microM, and epinephrine, 11, 1.1 and 0.55 microM, as stimuli. Platelet morphology in response to surface contact (adhesion) was evaluated by transmission electron microscopy to determine the percentage of platelets in the round/abortive (inactive), dendritic (intermediate) and spread (activated) forms. Plasma specimens obtained from healthy volunteers of similar age and sex were analyzed in parallel and served as control subjects. Compared with control subjects, patients had increased aggregation at all concentrations of both adenosine diphosphate and epinephrine (p less than 0.001). Patients also had fewer platelets in the dendritic form and more in the round/abortive and spread forms. Thus, patients with chest pain and normal coronary arteries have platelet hyperaggregability in vitro, although the clinical relevance of this finding is unclear.

Changes in hemostasis activity during delivery and theimmediate postpartum period

Postpartum deep vein thrombosis is believed to be related to increased activation of the hemostasis system at the time of delivery. To date, studies designed to test this hypothesis have had relatively small sample sizes or used the measurement of specific coagulation factors and functional tests reflecting hemostasis activity in vitro. With the use of recent technologic advances we determined the effect of delivery on hemostasis in vivo by measuring 11 hemostatic indices simultaneously in 70 healthy pregnant women. Significant increases were found in fibrinopeptide A (p less than 0.001), beta-thromboglobulin (p less than 0.001), and platelet factor 4 (p less than 0.001), suggesting maximum platelet activation and fibrin formation at the time of delivery. In addition to continued clotting activity at 3 hours post partum, increased D-dimer, fibrin-fibrinogen degradation products, and decreased alpha 2-antiplasmin levels suggest maximum fibrinolysis. These changes reflect a peak in hemostatic activity at delivery and in the immediate postpartum period that may predispose the development of deep vein thrombosis.

Thrombosis and hormone replacement therapy in postmenopausal women.

OBJECTIVE The effects of postmenopausal hormone replacement therapy on thrombosis remain controversial. We tested the hypothesis that estrogen or progesterone has no significant effect on thrombosis by means of newly developed markers of blood clotting, specifically prothrombin fragment 1 + 2, a marker of factor Xa generation, and thrombin-antithrombin III complex, a marker of thrombin generation. STUDY DESIGN A prospective study that included 106 women, 68 postmenopausal women on hormone replacement therapy and 38 postmenopausal controls, was performed. Plasma levels of prothrombin fragment 1 + 2 and thrombin-antithrombin III complex were measured by enzyme-linked immunosorbent assay. Multivariate analysis of the covariance was used for statistical analysis, controlling for patients age because the hormone replacement therapy group was older. RESULTS There were no statistically significant differences between the hormone replacement therapy and control groups in either of the clotting parameters measured. A comparison of the levels of prothrombin fragment 1 + 2 and thrombin-antithrombin III complex in patients receiving estrogen alone or estrogen plus progestin also revealed no differences. CONCLUSIONS Current doses of postmenopausal hormone replacement therapy do not appear to enhance in vivo clotting. Thromboembolic complications among postmenopausal women receiving hormone replacement therapy may therefore be secondary to congenital or other acquired coagulation defects.

Effects of warfarin on markers of hypercoagulability in patients with heart failure

Heart failure is associated with a hypercoagulable state. A single-center, randomized, double-blind, placebo-controlled trial was performed to test the hypothesis that warfarin will modify a hypercoagulable state in heart failure. This study included 76 patients with heart failure. At baseline, patients had evidence for a hypercoagulable state with elevated plasma levels of thrombin/antithrombin III (TAT) complexes (3.4 +/- 2.0 ng/ml), prothrombin fragment F1 + 2 (1.5 +/- 0.9 nmol/L), and D-dimers (630 +/- 401 ng/ml). Warfarin therapy (international normalized ratio [INR] 2.7 +/- 1.3) significantly decreased plasma levels of TAT complexes (p < 0.002), F1 + 2 (p < 0.001), and D-dimers (p < 0.001) when compared with baseline values at 1, 2, and 3 months of therapy. In contrast, patients receiving placebo had persistent elevation of TAT complexes (p = not significant [NS]), F1 + 2 (p = NS), and D-dimers (p = NS) during follow-up at 1, 2, and 3 months. The two treatment groups followed different trends over time for all three markers (p < 0.001). The effect of low-intensity warfarin (INR 1.3 +/- 0.08) versus moderate-intensity warfarin (INR 2.3 +/- 1.1 ) on markers of hypercoagulability was evaluated in 14 patients. When compared with baseline, low-intensity warfarin administration decreased plasma levels of TAT complexes (p = NS), F1 + 2 (p = 0.05), and D-dimers (p = 0.04). In these patients F1 + 2 was further reduced with moderate-intensity warfarin (p < 0.001). Our findings suggest that a hypercoagulable state in heart failure can be modified by warfarin therapy.

NATURAL PROTEINASE INHIBITORS IN EXTRACORPOREAL CIRCULATION

With the introduction of the pump oxygenator to cardiac surgery, an unnatural system was utilized to replace the heart and lungs temporarily. Although many surgical procedures that would not otherwise be possible are performed with the aid of a pump oxygenator, the use of such an unphysiological system is not without serious complications. Severe postoperative hemorrhages have frequently been observed in association with the use of pump oxygenators. These bleedings could not always be attributed to an unsatisfactory neutralization of heparin, nor could they be explained by a so-called “heparin-rebound-effect,”’ although a heparin-rebound effect is frequently observed when protamin sulfate is used for the neutralization of heparin.2 After observing severe hemorrhages in the course of open-heart surgery, a number of investigators started to study the coagulation system under these conditi0ns.3-~~ Most frequently, a decrease in the number of circulating platelets and in fibrinogen levels was observed. Some reported decreased levels of prothrombin, Ac-globulin and factor VIII (F-VIII) ,17,20,31,46 while the other coagulation components seemed not to be altered during this procedure. Others described

Markers for endothelial injury, clotting and platelet activation in preeclampsia

SummaryThe etiology of disseminated intravascular coagulation (DIC) in preeclampsia is not well understood. We measured plasma levels of fibronectin (FN), which may reflect endothelial cell injury, fibrinopeptide A (FPA), a specific marker of clotting, platelet counts (PLC) and mean platelet volumes (MPV), as well as β-thromboglobulin (βTG) and platelet factor 4 (Pf4), products of irreversible platelet activation in 24 preeclamptic patients and 24 controls matched for age, gestational age, labor status, and parity. In preeclampsia, FN and FPA were significantly elevated while PLC were significantly decreased (P<0.0001, <0.05 and <0.01, respectively). βTG, Pf4, and MPV values did not show significant differences. These findings support the hypothesis that endothelial injury, clotting activation and platelet consumption are increased in preeclampsia. However, the much closer association of preeclampsia with FN levels as compared to FPA, βTG, Pf4, suggests that endothelial injury is a more basic mechanism of preeclampsia than clotting or platelet activation.