Fibrinolytic parameters in women undergoing ovulation induction

The Pathophysiology of Hypercoagulability and Infertility

Alongside an interplay of a multitude of factors, attainment of a favorable pregnancy outcome is predicated on successful implantation, which in itself is a complex process anchored by balanced interchange with the hemostatic system. Among other etiologies, failure of implantation can result in infertility, and lead affected couples to consider assisted reproductive technology (ART) in an effort to fulfill their desire for procreation. Given the critical role of the hemostatic system in the process of implantation, documentation of a hypercoagulable state during controlled ovarian stimulation in the context of in vitro fertilization, as well as the potential association of its derangement in the setting of thrombophilia, with infertility, ART, ovarian hyperstimulation syndrome, and failure of implantation are explored. Additionally, current evidence addressing the relationship between ART and thromboembolism is examined, as is the role of therapy with heparin and aspirin to decrease thrombotic risk and improve ART-related pregnancy outcomes. Evidence-based recommendations from relevant professional societies are summarized.

Microparticles reveal cell activation during IVF – a possible early marker of a prothrombotic state during the first trimester

Cell-derived microparticles (MPs) are known to be elevated in a number of diseases related to arterial and venous thromboembolism (VTE), such as acute myocardial infarction, VTE (deep-vein thrombosis and pulmonary embolism) and peripheral arterial disease. IVF-associated pregnancies have previously been shown to be associated with an increased incidence of VTE, mechanisms behind being unknown and sparsely studied. Our objective was to assess cell activation during IVF through analysis of MP levels and phenotype following ovarian stimulation. Thirty-one women undergoing IVF were included and blood samples were collected at down regulation of oestrogen and at high level stimulation with 10- to 100-fold increased endogenous oestrogen levels. MPs were analysed by flow cytometry and phenotyped according to size and protein expression. We found that overall phosphatidylserine positive platelet-, endothelial- and monocyte-derived MPs significantly increased following ovarian stimulation with increased levels of platelet activation markers CD40 ligand and P-selectin. Furthermore, there was an increase in endothelial-derived MPs exposing activation marker E-selectin and monocyte-derived MPs, while neutrophil-derived MPs decreased slightly. In conclusion we found a major increase in MPs and markers indicating cell activation in parallel with the profound oestrogen boost during IVF. To assess whether these changes in MPs are associated with thromboembolic events requires extended longitudinal studies.

A New Perspective on the Risk of Hypercoagulopathy in Ovarian Hyperstimulation Syndrome Using Thromboelastography

Thromboelastography (TEG) provides real-time assessment of hemostasis by measuring the viscoelastic properties, coagulation factor, and platelet activity in whole blood samples. In this prospective case-control study, we wanted to investigate whether blood clot formation assessment, using TEG, can identify a hypercoagulable state in women with severe ovarian hyperstimulation syndrome (OHSS). Thirty-six women who were hospitalized with severe OHSS were allocated to the OHSS group and 32 women undergoing controlled ovarian hyperstimulation but who did not develop OHSS were allocated to the control group. The TEG indices were compared between women with severe OHSS and controls. All the coagulation indices assessed by TEG were significantly different in the OHSS group compared to the controls, depicting a hypercoagulable state. Median coagulation index was 3.6 (interquartile range: 2.80-4.15) and 1.45 (interquartile range: 0.20-2.30) in study group and controls, respectively ( P < .001). Our results show that TEG can be used to depict a hypercoagulable state in women with severe OHSS.

Fibrinolysis alterations in infertile women during controlled ovarian stimulation: influence of BMI and genetic components

INTRODUCTION

Ovarian stimulation protocols have been described to induce prothrombotic phenotype through alterations of both coagulation and fibrinolysis pathways. We investigated fibrinolytic changes during ovarian stimulation through a global test (CLT) and PAI-1 and TAFI concentrations at different times of ovarian stimulation procedure, and the influence of polymorphisms in genes encoding for fibrinogen chains (FGA, FGB, FGG), t-PA (PLAT), TAFI (CBP2), FXIII (FXIIA1, FXIIIB), plasminogen (PLG) and PAI-1 (PAI1) on their intermediate phenotype.

MATERIALS AND METHODS

We evaluated fibrinolytic and genetic parameters in 110 infertile women undergoing ovarian stimulation procedure (in vitro fertilization, IVF or intracytoplasmic sperm injection, ICSI). All women were observed during the mid-luteal phase of cycle (T(0)) and on day 5 (T(1)), 7 (T(2)) and 9 (T(3)) of the ovarian stimulation.

RESULTS

Significant changes in fibrinolytic parameters from T(0) to T(3) of ovarian stimulation were found (CLT p=0.003; TAFI p=0.009 and PAI-1 p=0.003). CLT values, TAFI and PAI-1 concentrations significantly increased from baseline to T(1) (p<0.0001, p=0.01, p=0.005, respectively)(,) and decreased at T(2,) but remained higher than those at T(0). Moreover, at baseline overweight women showed longer CLT, higher TAFI and PAI-1 concentrations than normal weight women, as well as at T(1) two-fold longer CLT and higher PAI-1 concentrations were observed (p=0.001 and p=0.05, respectively). Significant differences of TAFI and PAI-1 concentrations during ovarian stimulation according to TAFI and PAI1 polymorphisms were observed.

CONCLUSIONS

This study shows alterations of fibrinolysis and suggests the contribution of TAFI and PAI1 genes in modulating fibrinolysis changes during the ovarian stimulation cycle.

The “ART” of thromboembolism: A review of assisted reproductive technology and thromboembolic complications

Since its development over 25 years ago, the use of assisted reproductive technology (ART) is on the increase. Along with its use, are also reports of thromboembolic complications (TEC); these events could resulted in significant maternal morbidity and even mortality. In this article, we reviewed the general principles of ART. We also performed a search of all published cases of TEC associated with ART, and summarized the results of studies investigating underlying hemostatic changes with ART. The goal of this article is to provide non-fertility specialists an understanding of ART, so as to better manage TEC when they occur in predisposed patients. The most common ART procedure performed today, is in-vitro fertilization-embryo transfer (IVF-ET). The process of IVF involves the use of exogeneous hormones to achieve cycle control, stimulate the ovaries, and support implantation. During this process, supraphysiological estradiol levels can result. One major complication of this intervention, ovarian hyperstimulation syndrome (OHSS), can be associated with both arterial and venous thrombotic complications. These events (especially venous thrombosis) have also been reported to occur weeks after OHSS has resolved; and they can present in unusual sites (upper extremities) resulting in treatment challenges. From current available studies, it is clear that with ovarian stimulation, both the coagulation and fibrinolytic systems are activated. This activation appears to be exaggerated and prolonged with the development of OHSS. Whether these changes are sufficient by themselves to explain the occurrence of TEC is yet unknown. Future studies should be focused on defining the frequency and risk factors of these complications; provide a closer examination of the resultant changes in the coagulation cascade during ART, OHSS and early pregnancy; and investigating the appropriate treatment and thromboprophylaxis for patients undergoing a procedure considered "elective".

The aromatase inhibitor anastrozole is associated with favorable embryo development and implantation markers in mice ovarian stimulation cycles

OBJECTIVE

To investigate the embryonic and endometrial effects of anastrozole in preimplantation and implantation phases in FSH-induced cycles in mice.

DESIGN

Blind randomized study.

SETTING

University research laboratory.

ANIMAL(S)

Twenty-seven mature female mice.

INTERVENTION(S)

Single-dose anastrozole (25 mg/kg [0.75 mg]), recombinant FSH (5 IU/mL), and hCG (5 IU/mL) (n = 9); recombinant FSH (5 IU/mL) and hCG (5 IU/mL) (n = 9); or sterile saline (1 mL) (n = 9). The morning of finding the vaginal plug was designated as day 1 of embryonic development (E1). Three mice from each group were sacrificed on E1 and embryos aspirated from uterine tubes. The rest of the mice were sacrificed on E2.5-3 and uteruses removed.

MAIN OUTCOME MEASURE(S)

Embryo quality, endometrial histologic evaluation, and immunohistochemical analysis of tumor necrosis factor-alpha, leukemia inhibitory factor, laminin, and collagen IV staining.

RESULT(S)

Anastrozole use in FSH-induced cycles not only caused an increase in preimplantation receptivity and implantation but also supported release of implantation markers. The enhanced embryo development seen in this study would explain the higher implantation because embryo development is synchronized with endometrial development.

CONCLUSION(S)

In mice, the use of anastrozole in FSH-induced cycles has a positive effect on embryo quality and implantation. This effect might be species dependent, and human studies are needed.

In vitro fertilization-induced alterations in coagulation and fibrinolysis as measured by thromboelastography

Supraphysiologic increases in estrogen produced by in vitro fertilization (IVF) promote the expression of hemostatic markers. Although quantitative studies of individual markers have been performed during IVF, their results are conflicting and do not reveal the qualitative effect of each marker on the overall coagulation and fibrinolytic processes. Thrombelastograph (TEG) coagulation analysis, by contrast, provides a global measure of coagulation and fibrinolysis and can indicate the relative contributions of clotting factors, fibrinogen, and platelets to each process. We studied the serum estrogen concentrations and TEG variables in 24 women at the beginning and conclusion of an IVF stimulation cycle. Serum estradiol (E(2)) concentrations (mean +/- SD) increased from 26.9 +/- 8.6 to 2098 +/- 913 pg/mL (P < 0.005) at baseline and oocyte retrieval, respectively. The measured TEG indices demonstrated alterations in coagulation rather than fibrinolysis. Although significant changes were noted in both the clot formation time and the coagulation index (P < 0.005), all TEG values remained within the normal range. In addition, an increased role of fibrinogen in promoting clot strength was observed. These findings may assist in the treatment of IVF patients who ultimately develop thromboembolic complications as a result of ovarian hyperstimulation. IMPLICATIONS. The dramatic changes in estrogen produced by in vitro fertilization therapies result in hemostatic marker alterations. Thrombelastograph coagulation analysis, which provides a global assessment of these changes, demonstrated significant alterations in two coagulation indices (clot formation time, coagulation index), although all variables remained within normal limits. The relative importance of fibrinogen versus platelets in determining clot strength was observed. No significant alterations in fibrinolysis were detected.

The mechanisms of thrombotic risk induced by hormone replacement therapy

OBJECTIVES

To review the available information on the action of hormones on the mechanisms involved in thrombotic risk.

RESULTS AND CONCLUSIONS

Thrombosis plays a crucial role in the genesis and progression of both coronary heart disease (CHD) and venous thromboembolic disease (VTED), the two main forms of cardiovascular disease. Two main determinants of the thromboembolic phenotype, hypercoagulable state and altered endothelium, accumulate much of the work performed on the influence of hormones on thrombosis. Information has accumulated mainly for oestrogens, but increasing evidences support a role for progestogens. The sensitivity of each of the three components of the hemostatic balance, the coagulation cascade, the anticoagulant system and fibrinolysis, to oestrogens has been widely examined in the literature. Functional tests suggest that HRT is accompanied by a procoagulant state. Much of the work has concentrated on changes induced on reputable indicators of risk for either CHD or VTED. Distinct indicators of increased coagulability, such as resistance to activated C protein, antithrombin or tissue factor pathway inhibitor have been selected for VTED, whereas factor VII, fibrinogen, and defective fibrinolysis, for CHD. Different states of genetic susceptibility have been involved in both forms of the disease. The status of health of endothelium, defines another scenario for attention in CHD. A long-term anti-atherogenic action of oestrogens, which may be associated with short-term risk in cases of atherosclerosis-induced endothelial dysfunction, may most adequately explain much of the clinical observation. In both CHD and VTED, the procoagulant changes initiate soon after HRT administration.

Hemostatic Factors and Ischemic Heart Disease Risk Among Postmenopausal Women

The following is a review of (largely) epidemiologic evidence on whether changes in plasma hemostatic concentrations occur with menopause and with postmenopausal hormone therapy which may have an impact on risk of ischemic heart disease. To date, only plasma fibrinogen has been positively associated with long-term risk of disease among women; however, data are sparse. Taken together, the evidence supports an impact of endogenous sex hormone levels on thrombotic potential and points to a modest increase in a number of plasma hemostatic factor levels at menopause. Results of studies of estrogen therapy are somewhat conflicting. Observational findings suggest that, except for possibly the Factor VII level, estrogen therapy may prevent the menopause-related rise in plasma hemostatic factors. In contrast, controlled experiments have found increased markers of thrombin generation with use of common formulations of estrogen therapy. The hemostatic effects found with oral preparations do not appear to occur with transdermal forms of estrogen although data are limited. Overall, the evidence shows menopause to have an impact on plasma levels of hemostatic factors which appears to be modified by use of oral estrogen. Whether these alterations in plasma levels have an impact on risk of ischemic heart disease among postmenopausal women remains to be demonstrated.

Generation of thrombin in blood plasma of non-pregnant and pregnant women studied through concentration of thrombin-antithrombin III complexes

OBJECTIVE

The main question in this study is how much more thrombin is generated in blood plasma of pregnant women than in non-pregnant women.

STUDY DESIGN

Thrombin-antithrombin III complexes (TAT) were used as markers of thrombin generation in vivo. They were measured by the ELISA method in blood plasma of 15 non-pregnant and 43 pregnant, as well as 30 parturient women and 10 women after delivery.

RESULTS

With normal menstrual cycles, TAT levels did not change significantly throughout the cyclic phases, and the mean +/- S.D. calculated for all cyclic phases was 1.9 +/- 0.3 micrograms/l. In the 2nd trimester the level of TAT was 16.0 +/- 2.8 micrograms/l and at term 21.5 +/- 11.9 micrograms/l. Throughout the 1st and 2nd stage of labour the level of TAT increased insignificantly, but after placenta separation it was significantly higher than before labour (30.8 +/- 20.4 micrograms/l). In the 3rd and 7th days after delivery the level of TAT was still higher than in non-pregnant women.

CONCLUSION

It was found that the level of TAT in normal menstrual cycles is stable, whereas it increases in pregnancy. Relating the values of the cycle to those of pregnancy it was calculated, that at the end of pregnancy there is a ten-fold increase of TAT level and after placenta separation and expulsion--temporarily even fifteen-fold--increase. In the 3rd to 7th day after delivery, the TAT level was still higher than in non-pregnant women.

In vitro platelet function in controlled ovarian hyperstimulation cycles

OBJECTIVE

To determine the effects of elevated endogenous E2 levels on in vitro platelet function in patients undergoing controlled ovarian hyperstimulation (COH).

DESIGN

Women with normal ovulatory cycles and patients undergoing COH on cycle day 3 and near ovulation (preovulatory follicles were at least 16 mm in diameter) were studied. Serum E2, Thrombostat 4000, (V. d. Goltz, Seeon, Germany), von Willebrand factor antigen (vWF-Ag), and platelet aggregation and adenosine triphosphate (ATP) release to adenosine diphosphate (ADP), collagen (COL), and arachidonic acid (AA) were measured.

SETTING

University-based outpatient infertility clinic.

PATIENT(S)

Twenty-two consenting infertile women undergoing COH cycles and 14 women with documented ovulatory cycles.

MAIN OUTCOME MEASURE(S)

Whole blood platelet aggregation with ADP, COL, AA, and Thrombostat 4000.

RESULTS(S)

Estradiol levels rose significantly at peak times (P = 0.011). No changes were noted in in vitro platelet function measured by the Thrombostat 4000 and by whole blood platelet aggregation with ADP and AA and in ATP release with ADP, COL, or AA. Aggregation with collagen was increased because of likely elevations in vWF-Ag levels.

CONCLUSION(S)

No significant changes in in vitro platelet function were noted in 19 women undergoing COH with E2 levels two to three times that observed in oral contraceptive or hormone replacement therapy users, suggesting no increased risk for arterial thromboembolism.