Differential haemostatic risk factors for pregnancy-related deep-vein thrombosis and pulmonary embolism

How can Secondary Thromboprophylaxis in High-Risk Pregnant Patients be Improved?

Low-molecular-weight heparin (LMWH) is suggested for thromboprophylaxis in pregnant women with previous venous thromboembolism (VTE). Anyway, there is only limited amount of studies evaluating the effect of LMWH on hemostatic parameters during pregnancy of patients with previous VTE and the need of secondary thromboprophylaxis. We therefore provide results of prospective and longitudinal assessment of changes in hemostasis in high-risk pregnant women at four times during pregnancy (T1–T4) and one time after the postpartum period (T5) used for individualized modification of thromboprophylaxis. In this study, the results of coagulation factor VIII (FVIII) and protein S (PS) activity, ProC Global ratio and anti-Xa activity were evaluated. Despite the thromboprophylaxis, an increased predisposition to thromboembolic complications was detected (significant increase in FVIII activity and decrease in PS function, ProC Global ratio not normalized even after the postpartum period – p < .0001 between controls and T5 for PS and ProC Global). These results indicate that hemostasis may not be restored even 6 to 8 weeks after delivery and pose the question when is it safe to withdraw the anticoagulant thromboprophylaxis in high-risk patients with prior VTE.

Maternal thrombin generation and D-dimer levels in obesity and pregnancy: results from the maternal thrombin generation in obesity and pregnancy (MaTOPs) study

Venous thromboembolic disease (VTE) risk increases five-fold antenatally and 14-fold during the puerperium. Obesity significantly increases this risk. The D-dimer assay and more novel Calibrated Automated Thrombogram (CAT) assay laboratory tests display potential for use in VTE risk stratification in pregnancy, although to date, research in the performance characteristics of these tests in obese and nonobese pregnant populations is limited. The aim of this study was to compare D-dimer and thrombin generation levels in obese and nonobese pregnant women. Pregnant women were recruited and categorised, as obese (BMI ≥30) or nonobese (BMI 18.5-25). Blood was collected at 26-28 weeks' gestation, 36-40 weeks' gestation and 6-12 weeks postpartum and D-dimer concentrations and endogenous thrombin potential (ETP) were determined. Student's t-test was used to analyse differences in mean D-dimer and ETP. At 36-40 weeks, obese pregnant women had higher D-dimer concentrations (P = 0.001) but lower ETP levels compared with nonobese women (P = 0.044). D-dimer was higher in nonobese than in obese women at 6-12 weeks postpartum (P = 0.026). There was no difference in mean D-dimer (P  = 0.825) and mean ETP (P  = 0.424) between obese and nonobese women at 26-28 weeks. No difference was observed in mean ETP at 6-12 weeks postpartum (P  = 0.472). ETP was lower in both obese and nonobese women postpartum than during pregnancy. D-dimer was lower in obese women but not in nonobese women postpartum. D-dimer concentrations and ETP were not significantly different during multiple time points in pregnancy and postpartum between obese and nonobese pregnant women suggesting limited utility in VTE risk assessment in obese pregnant women.

The Optimal Cutoff Level of D-Dimer during Pregnancy to Exclude Deep Vein Thrombosis, and the Association between D-Dimer and Postpartum Hemorrhage in Cesarean Section Patients

OBJECTIVE

The main purpose was to clarify the optimal D-dimer cutoff level during pregnancy to exclude deep vein thrombosis (DVT) prior to Cesarean section. The secondary purpose was to determine whether D-dimer can predict severe postpartum hemorrhage (PPH) in Cesarean section patients.

METHODS

Two hundred and seventy eight elective Cesarean section cases were enrolled. Clinical factors and blood parameters at 34-37 weeks of gestation were analyzed. To detect DVT, lower extremities veins were examined using color Doppler ultrasonography in cases with D-dimer level ≥ 1.5 μg/mL. In addition, postpartum blood loss amounts during Cesarean section were recorded.

RESULTS

Five DVT cases occurred in 250 singleton pregnancies, and 2 DVT cases occurred in 28 twin pregnancies. The overall incidence of DVT was 2.5%. The D-dimer level was higher in DVT cases than in non-DVT cases (3.84±1.97 vs. 2.31±1.48 μg/mL, P<0.01). The optimal D-dimer cutoff level was 2.6 μg/mL with a negative predic tive value of 99.5%, and sensitivity of 85.7%. PPH during Cesarean section was positively correlated with D-dimer level in all pregnancies. However, this relationship disappeared after excluding twin pregnancies.

CONCLUSION

A D-dimer level < 2.6 μg/mL at 34-37 weeks of gestation has the potential to exclude DVT. D-dimer can be an independent predictor for severe PPH for all Cesarean section cases, including twin pregnancies.

Genome-wide analysis of genetic determinants of circulating factor VII-activating protease (FSAP) activity

Essentials Knowledge of genetic regulators of plasma factor VII activating protease (FSAP) levels is limited. We performed a genome-wide analysis of variants influencing FSAP activity in Scandinavian cohorts. We replicated an association for Marburg-1 and identified an association for a HABP2 stop variant. We identified a novel locus near ADCY2 as a potential additional regulator of FSAP activity.

SUMMARY

Background Factor VII-activating protease (FSAP) has roles in both coagulation and fibrinolysis. Recent data indicate its involvement in several other processes, such as vascular remodeling and inflammation. Plasma FSAP activity is highly variable among healthy individuals and, apart from the low-frequency missense variant Marburg-I (rs7080536) in the FSAP-encoding gene HABP2, determinants of this variation are unclear. Objectives To identify novel genetic variants within and outside of the HABP2 locus that influence circulating FSAP activity. Patients/Methods We performed an exploratory genome-wide association study (GWAS) on plasma FSAP activity amongst 3230 Swedish subjects. Directly genotyped rare variants were also analyzed with gene-based tests. Using GWAS, we confirmed the strong association between the Marburg-I variant and FSAP activity. HABP2 was also significant in the gene-based analysis, and remained significant after exclusion of Marburg-I carriers. This was attributable to a rare HABP2 stop variant (rs41292628). Carriers of this stop variant showed a similar reduction in FSAP activity as Marburg-I carriers, and this finding was replicated. A secondary genome-wide significant locus was identified at a 5p15 locus (rs35510613), and this finding requires future replication. This common variant is located upstream of ADCY2, which encodes a protein catalyzing the formation of cAMP. Results and Conclusions This study verified the Marburg-I variant to be a strong regulator of FSAP activity, and identified an HABP2 stop variant with a similar impact on FSAP activity. A novel locus near ADCY2 was identified as a potential additional regulator of FSAP activity.

Clinical relevance of fibrin fiber diameter during different phases of pregnancy

INTRODUCTION

Pregnancy-related deep vein thrombosis (DVT) is most common during the late phase of pregnancy and the first 6-weeks postpartum. Pregnancy-related DVT can have long-term complications, specifically post-thrombotic syndrome (PTS). Fibrin network ultrastructure is altered during pregnancy and post-partum. It is therefore essential to evaluate fibrin fiber diameter during and after pregnancy as this may provide insight into pregnancy-related DVT and subsequent PTS.

MATERIALS AND METHODS

The fibrin network ultrastructure of females during different phases of pregnancy was compared to that of non-pregnant females to assess possible changes to the fibrin network morphology and fibrin fiber diameter using scanning electron microscopy micrographs.

RESULTS

The fibrin network arrangement was more densely packed during different phases of pregnancy, corresponding to earlier findings. Fibrin diameter decreased significantly during pregnancy, with the greatest decrease occurring during the late phase of pregnancy. The fractal dimensions of fibrin micrographs increased significantly during pregnancy compared to nonpregnant females. These changes are indicative of a simultaneous hypercoagulable and hypofibrinolytic state and correspond to the increased risk of DVT and subsequent development of PTS.

CONCLUSION

It is critical to identify "vulnerable" females with an inflammatory predisposition to prevent possible DVT and subsequent PTS. Modifiable risk factors like obesity and smoking should be addressed to alleviate the burden on the coagulation system. Morphological and viscoelastic techniques are crucial in assessing the coagulatory health of females during pregnancy.

D-dimer concentration outliers are not rare in at-term pregnant women

OBJECTIVES

To determine the D-dimer levels in pregnant women at term and the differences between pregnant women with different D-dimer levels.

DESIGN AND METHODS

The plasma D-dimer concentrations in pregnant women at term were identified in a cross-sectional study. The clinical indicators that are potentially relevant to D-dimer levels were compared between the pregnant women with different D-dimer levels (i.e., normal, mildly increased, and severely increased).

RESULTS

There were always some D-dimer concentration outliers in the pregnant women at term regardless of the presence or absence of complications, and there were no significant differences in maternal age, gestational age, gravidity, parity, blood count, blood coagulation, or liver function between the pregnant women with different D-dimer levels.

CONCLUSIONS

D-dimer levels may vary significantly during pregnancy for unknown reasons. This variation, particularly in pregnant women at term, might lead to questionable diagnostic information regarding coagulation.

The role of inflammation in post-thrombotic syndrome after pregnancy-related deep vein thrombosis: A population-based, cross-sectional study

Previous studies suggest that inflammation may play a role in the pathophysiology of post-thrombotic syndrome (PTS). The aims of the present study were to evaluate markers of inflammation as possible predictors for PTS after pregnancy-related deep vein thrombosis (DVT). We included 182 women with a pregnancy-related DVT during 1990-2003 and 314 controls. All women answered a questionnaire and donated a blood sample in 2006. PTS was diagnosed when a self-reported Villalta score was above 4. The following predictors of PTS were included: high sensitivity C-reactive protein (hsCRP), interleukin (IL)-6, IL-8, IL-10, monocyte chemotactic protein (MCP)-1, transforming growth factor (TGF)-β1, platelet derived growth factor (PDGF)-BB, and the two adhesion molecules intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1. High values were defined as above median value among controls. We found that 41% of cases were diagnosed with PTS 3-16years after index pregnancy. In univariate analyses, high values of hsCRP, IL-6, and IL-10 were significantly associated with PTS with ORs 2.3 (95% CI; 1.2-4.2, p=0.008), 1.9 (1.0-3.5, p=0.04), and 10.8 (1.3-89.8, p=0.01), respectively. Only hsCRP, which has previously been found to be independently associated with PTS, was independently associated with PTS in a multivariate logistic regression model, when adjusting for proximal DVT occurring postpartum, age above 33years, and smoking (adjusted OR 2.4; 95% CI 1.2-4.8, p=0.01). We conclude that hsCRP was associated with PTS 3-16years after pregnancy-related DVT.

Increased thrombin generation in women with polycystic ovary syndrome: A pilot study on the effect of metformin and oral contraceptives

OBJECTIVE

Polycystic ovary syndrome (PCOS) is associated with risk factors for cardiovascular disease (CVD) which may be modified by the use of metformin and oral contraceptives (OC). Thrombin generation (TG) measures are risk markers of CVD and address the composite of multiple factors that influence blood coagulation. This prospective, randomized, intervention study evaluated the potential influence of PCOS on TG measures and the effect of OC and/or metformin on TG measures in women with PCOS.

MATERIAL AND METHODS

Ninety patients with PCOS and 35 controls were included. Patients were randomized to 12 months of treatment with metformin, metformin+OC or OC alone. C-reactive protein (CRP), fibrinogen, total cholesterol, trunk fat mass, body mass index, estradiol, testosterone, sex hormone binding globulin (SHBG) as well as TG measures, i.e. the lag time for formation of thrombin, the endogenous thrombin potential (ETP), peak thrombin concentration (peak) and time to peak were determined at baseline and after 12 months of treatment.

RESULTS

CRP and total testosterone were significantly higher and SHBG significantly lower in PCOS women than in controls (P=0.012, P<0.001 and P=0.008, respectively). The TG measures ETP, peak and lag time were increased in women with PCOS compared to controls (P<0.01). Significant correlations were observed between TG measures and fibrinogen, CRP, SHBG and fat trunk mass (P>0.01). ETP (P=0.006), peak (P=0.003) and lag time (P=0.023) remained increased after adjustment for these potential confounders. Treatment with OC and metformin+OC further increased ETP (P<0.001) and peak (P<0.005) and reduced time to peak (P<0.04). The increase in ETP was significantly lower in the metformin+OC group than in the OC group (P<0.05). Metformin alone did not affect TG significantly.

CONCLUSIONS

PCOS is associated with increase in TG measures independent of other risk factors of CVD. OC increase TG measures further and may thus add to the increased risk of CVD already present in women with PCOS.

Comparison of markers of coagulation activation and thrombin generation test in uncomplicated pregnancies

INTRODUCTION

Pregnancy is a well-established risk factor for venous thromboembolism, and is associated with a state of hypercoagulability or parameters of thrombin generation. Currently, there is a lack of consensual data on thrombin generation during pregnancy. This study aimed to find a sensitive and specific biological marker of coagulation activation and to identify parameters of thrombin generation.

PATIENTS AND METHODS

The population included 101 women with uncomplicated pregnancies. The objective of this study was to correlate thrombin generation test (measured at 5pM tissue factor, 4μM lipids and without thrombomodulin), with fibrinogen and markers of blood coagulation activation: D-dimer, prothrombin fragments 1+2 (F1+2), thrombin-antithrombin complexes (TAT) and fibrin monomer complexes (FMC) in these women. Internal quality control was performed in each set of experiments.

RESULTS

Fibrinogen, D-dimer, F1+2, and TAT concentrations increased significantly throughout pregnancy, and were correlated with term of pregnancy. In our study, thrombin generation seemed to increase early on, and then remained stable throughout normal pregnancy, in contrast with other markers of blood coagulation activation, excepting FMC. The latter are subject to large inter-individual variations, especially during second trimester. No correlation was demonstrated between thrombin generation parameters and other activation markers.

CONCLUSION

While markers of coagulation activation significantly increased during pregnancy, thrombin generation increased only early on and remains stable during pregnancy. Finding a sensitive and specific biological marker for vascular pregnancy complications, such as FMC and thrombin generation levels, requires further investigation.