Coagulation activation markers do not correlate with the clinical risk of thrombosis in pregnant women

Establishing Expectancy Values for Fibrin Monomer in Uncomplicated Pregnancy

Background  During pregnancy, a physiological increase of molecular activation markers (MAM) of hemostasis such as prothrombin fragments 1 + 2, thrombin-antithrombin complex, and D-dimers (DD) occurs. Therefore, monitoring MAM levels during pregnancy to evaluate the risk of venous thromboembolism (VTE) may be unreliable; nevertheless, DD analysis in pregnancy is widely performed. In contrast to DD, fibrin monomer (FM) levels have been reported to remain stable during pregnancy. Objectives  The main aim of this study was to define the expected range for FM levels in pregnant outpatients. In addition, we examined the impact of the individual VTE risk, as calculated by the pregnancy risk score of the Royal College of Obstetricians and Gynaecologists (RCOG), as well as that of antithrombotic treatment on FM levels. Methods  A total of 342 pregnant women seen at our hemostasis unit were included throughout 350 pregnancies in 899 samples. Results  Low-risk thrombophilia, but not the RCOG score itself, was found to influence all MAM levels, whereas antithrombotic treatment had only an impact on DD. For FM, a reference range could be calculated irrespective of the pregnancy term, in contrast to other MAMs, which fluctuated throughout pregnancy. Conclusions  Our findings suggest a stronger impact of inherited thrombophilia on hemostasis activity during pregnancy as compared with acquired or other predisposing thrombophilic risk factors. FM levels showed a marginal increase during pregnancy in contrast to other MAM and remain a potential candidate to improve the laboratory assessment of VTE risk during pregnancy. Further prospective studies in pregnant patients with suspicion of VTE are needed.

Thrombin generation test as a marker for high risk venous thrombosis pregnancies

Pregnancy is a well-established risk factor for venous thromboembolism and is associated with a state of hypercoagulability. The use of sensitive and specific biological markers to predict risk factors for thrombosis is essential during pregnancy. Our objective was to investigate the usefulness of thrombin generation test (TGT) as a marker to predict the risk of thrombosis in high risk venous thrombosis (HRVT) pregnancies compared to normal pregnancies. This retrospective study enrolled 134 women with HRVT pregnancies, 78 of whom had monozygotic, spontaneous and untreated pregnancies and formed the study group. The control group comprised 106 women with normal pregnancies. Routine assessment of coagulation activation markers: fibrinogen, D-dimer, prothrombin fragments 1 + 2 (F1 + 2), thrombin-antithrombin complexes (TAT) and fibrin monomer complexes (FMC) was performed every 5 weeks in the study group to detect a possible pathological state of hypercoagulability. TGT was performed using platelet-free plasma, 1 and 5 pM tissue factor (TF), supplemented by phospholipids (PL) ± thrombomodulin. Fibrinogen, D-dimer, F1 + 2, and TAT, but not FMC, increased significantly throughout pregnancy in both groups but no difference was shown between the groups. TGT showed an early increase in thrombin generation in both groups, which stabilized during the second month of pregnancy. No correlation was demonstrated between thrombin generation parameters and coagulation activation markers. Based on our results, TGT did not prove conclusive as a marker to predict the risk of thrombosis in HRVT pregnancies. Finding a sensitive and specific biological marker to predict thrombosis risk requires further investigation.

Hypercoagulable States: A Review

Vascular surgeons are often asked to evaluate patients with recurrent thromboses or thromboses in unusual locations either arterial or venous. There may be obvious inciting factors, but in many of these patients the possibility of a previously undiagnosed hypercoagulable state must be considered. Hypercoagulable states can be acquired (smoking, medication, change in physiologic status as occurs with pregnancy) or congenital. Congenital hypercoagulable disorders are more prevalent in families or patients with a history of thromboembolic events early in life or multiple miscarriages and include conditions such as protein C or S deficiencies, factor V Leiden mutation, and prothrombin gene variant. This article reviews the hypercoagulable states that are encountered in clinical practice as well as guidelines for testing and goals of therapy.

[Thrombosis risk during pregnancy after history of cerebral venous thrombosis]

INTRODUCTION

Few data have been published about the prognosis of a pregnancy following an episode of venous cerebral thrombosis (CVT), and far less about preventive strategy.

METHODS

This is a retrospective study of a case series of 11 pregnancies in six women who had previously presented a CVT.

RESULTS

The first pregnancies after CVT occurred on average 58 months later. Prevention with aspirin or heparin was administered in ten cases during pregnancy, and in all the cases with heparin in postpartum. No recurrence of CVT was observed. A minor pulmonary embolism was diagnosed in postpartum in one case.

CONCLUSION

Prognosis of a pregnancy after a CVT seems to be favourable if a sufficient delay after CVT is respected. Although no results of controlled trials are available, prophylaxis with heparin is probably reasonable as benefit seems higher than risks and is strongly advised during the postpartum period.

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.

[Evaluation of D-dimer as a marker for severity in pregnancies with preeclampsia]

OBJECTIVES

Alterations in blood coagulation and fibrinolysis play a major role in the pathogenesis of preeclampsia. HELLP syndrome is associated with hypercoagulability and leads to maternal and perinatal complications. Our purpose was to evaluate D-dimer as a marker for severity in pregnancies with preeclampsia.

PATIENTS AND METHODS

Plasma D-dimer levels were measured using an enzyme-linked immunosorbent assay (ELISA) technique. We studied the association between D-dimer levels and clinical and biological characteristics of pregnancies complicated by preeclampsia.

RESULTS

D-dimer values increased with increasing gestational age. Patients with HELLP syndrome had mean D-dimer values significantly greater than patients with preeclampsia alone (3848±2551 versus 1578±1077, P<0.001). However, the level of D-dimer at the time of admission was poorly predictive of occurrence of HELLP syndrome. Area under of the ROC curve was 0.69 (CI 95%: 0,59-0,79). The best threshold was 2170 ng/mL with a sensitivity of 0.91 and a specificity of 0.40. Other severity criteria of preeclampsia were not associated with higher levels of D-dimer.

DISCUSSION AND CONCLUSION

In preeclamptic patients, D-dimer levels were related with gestational age and HELLP syndrome. However, accuracy of this test to predict occurrence of HELLP syndrome or severe preeclampsia was too low to recommend its use routinely.

A model for calculating the within-subject biological variation and likelihood ratios for analytes with a time-dependent change in concentrations; exemplified with the use of D-dimer in suspected venous thromboembolism in healthy pregnant women

BACKGROUND

Within-subject biological variation and reference change value (RCV) are difficult to calculate for an analyte with a changing concentration. The aim of this study was to develop a model to examine if it was possible to transform an analyte with a time-dependent change in concentration into a 'steady-state' situation by the use of 'multiples of the median' (MoM) and its natural logarithm (lnMoM). In addition, we wanted to extend the RCV concept, using likelihood and odds ratios, to calculate the post-test probabilities for disease. D-dimer in pregnancy is used as an example.

METHODS

Blood samples from 18 healthy pregnant and 18 healthy non-pregnant women were collected every fourth week. MoM of the D-dimer concentrations was calculated for each four-week interval to obtain a 'steady-state' situation for the D-dimer concentrations. The 'normalized' values were then transformed to the lnMoM to obtain a Gaussian distribution, used for the estimation of biological variation.

RESULTS

Median D-dimer concentrations increased six-fold during pregnancy. Within-subject variation (SD) of lnMoM D-dimer was 0.27 during pregnancy and 0.23 in non-pregnant women, with RCVs of 0.72 and 0.90, respectively.

CONCLUSIONS

By using the lnMoM model, an increasing concentration of an analyte can be transformed to a steady-state situation and the within-subject biological variation and its derived parameters can be calculated.

Predictive Value of the Rapid Whole Blood Agglutination D-Dimer Assay (AGEN SimpliRED) in Community Outpatients with Suspected Deep Venous Thrombosis

CONTEXT

D-dimer assay has been used to screen patients with deep venous thrombosis (DVT). Because both the predictive value and sensitivity/specificity of the test vary according to the type of assay, prevalence, and pretest probability of DVT, clinicians must know the local performance of the d-dimer assay.

OBJECTIVE

To evaluate the predictive value of the rapid whole blood agglutination d-dimer Assay (AGEN SimpliRED) in community outpatients with suspected DVT in the Kaiser Permanente (KP) Mid-Atlantic Region.

DESIGN

Retrospective, randomized, cross-sectional review of electronic medical records of patients with suspected DVT who underwent d-dimer testing for venous thromboembolism.

METHODOLOGY

A total of 5104 patients with suspected venous thromboembolism underwent d-dimer testing using AGEN SimpliRED from April 2001 to December 2002. A total of 551 electronic medical records were reviewed, and results of d-dimer assay and compression ultrasonography were tabulated. Records were analyzed to determine later diagnosis of DVT or unexplained death occurring as late as six months after initial testing.

RESULTS

Electronic records showed a 5.3% disease prevalence. Ten patients were excluded from data analysis. A total of 129 (23.8%) patients had positive d-dimer; the positive predictive value was 20.2% (CI, 13.2% to 27%). A total of 412 (76.1%) patients had negative test results; three of these patients had DVT shown by compression ultra-sonography; negative predictive value was 99.3% (CI, 98.4% to 100%). Calculated sensitivity was 89.7%; specificity was 79.9%.

CONCLUSION

In the outpatient setting, the rapid whole blood agglutination d-dimer assay (AGEN SimpliRED) used in combination with both clinical judgment and compression ultrasonography exhibited a high negative predictive value comparable with previously reported values.

Successful treatment of a patient with primary Sjögren's syndrome complicated with pericarditis during pregnancy

A 35-year-old woman with primary Sjögren's syndrome (pSS) developed fever and chest pain during pregnancy. When the dose of prednisolone was reduced, she experienced chest pain with elevated CRP and D-dimer, resulting in admission to our hospital with marked cardiomegaly and pleural effusion. Because there was no evidence of other autoimmune disorders or infection, oral prednisolone was increased to 30 mg daily with heparin, and hypercoagulopathy was carefully monitored. The patient's condition improved rapidly, and she delivered a healthy baby. This is the first case to support the beneficial effect of prednisolone in pericarditis with pSS, and illustrates its safety during pregnancy.

Altered hemostatic balance and endothelial activation in pregnant women with familial hypercholesterolemia

INTRODUCTION

Patients with familial hypercholesterolemia (FH) are prone to premature cardiovascular disease. During pregnancy plasma lipids reach higher absolute values in FH than in healthy women. Pregnancy is associated with activation of coagulation and possibly also of vascular endothelium, which might further increase the risk of cardiovascular disease in FH. However, whether hemostatic and endothelial activation markers are increased in pregnant FH women compared with non-FH pregnancies, is unknown.

MATERIALS AND METHODS

Activation markers of hemostasis and endothelium were analyzed in blood samples collected prospectively from 22 heterozygous FH women during pregnancy and compared with those of a reference group of 149 healthy, pregnant women.

RESULTS

A procoagulant pattern was detected in both groups, but was more evident among FH women at least partly due to their enhanced thrombin generation, and because tissue factor pathway inhibitor type 1 increased in the reference group only. Furthermore, plasminogen activator inhibitor type 2 antigen increased more in FH than in the reference group. Whereas C-reactive protein, intercellular adhesion marker-1 and E-selectin did not change appreciably, vascular endothelial cell adhesion molecule 1 rose markedly in FH.

CONCLUSION

Increased lipid levels as well as a net procoagulant activity and an enhanced endothelial activation possibly confer additional risks of cardiovascular disease among pregnant FH women.

Imaging pulmonary embolism in pregnancy: what is the most appropriate imaging protocol?

Pulmonary embolism is the leading cause of death in pregnancy. Despite the difficulties in clinical diagnosis and the concerns regarding radiation of the fetus, the British Thoracic Society guidelines for imaging pulmonary embolism do not specifically address the issue of imaging for pulmonary embolism in this group. This communication discusses the difficulties of diagnosis and imaging pulmonary embolism in pregnancy and proposes a suitable imaging protocol. Clinical exclusion of patients from further imaging is recommended if the patient has a low pre-test probability of pulmonary embolism and a normal d-dimer. It is advised that all remaining patients undergo bilateral leg Doppler assessment. If this test is positive, the patient should be treated for pulmonary embolism; if negative, all patients should be referred for CT pulmonary angiography. Ideally, informed consent should be obtained prior to CT scanning. All neonates exposed to iodinated contrast in utero should have their thyroid function tested in the first week of life due to the theoretical risk of contrast induced hypothyroidism.

Maladie thromboembolique périopératoire et obstétricale. Pathologie gynécologique et obstétricale

Venous thromboembolism is a leading cause of maternal mortality in many countries, including France. Most enquiries have repeatedly demonstrated that many deaths could be avoided, suggesting the need to update and ensure a wider diffusion of recommendations. Although thromboembolism-induced maternal death plays a major role, the absolute incidence of events remains low, reducing the ability to perform well-designed research and the level of recommendations presented. Many personal or pregnancy-related factors have been identified as increasing the risk of thromboembolism in pregnant patients but few of them have been associated with a significantly increased risk. A history of thromboembolic event and some thrombophilic factors (including antithrombin deficiency and antiphospholipid syndrome) carry the greatest risk. Pregnancy itself, caesarean delivery and the postpartum period, although associated with an increased risk play a minor role when not combined with other risk factors. Prophylactic treatment relies mainly on low molecular weight heparins which safety is now well established in pregnant patients. Dose and duration of treatment should be adapted to the perceived level of risk. The occurrence of a thromboembolic event is also increased after gynaecological surgery but major and cancer surgery carry the greatest risk. Here also, low molecular weight heparins play a leading role, although non pharmacologic means are useful. Dose and duration should be dependent on the level of risk.

D-dimer levels during delivery and the postpartum

BACKGROUND

D-dimer (DD) measurement has proved to be very useful to exclude venous thromboembolism (VTE) in outpatients. However, during pregnancy, the progressive increase as well as the interindividual variations of DD means that in this instance they are of poor value to rule out VTE. Only a few studies have reported measurements of DD levels in the postpartum.

OBJECTIVES

To measure DD sequentially in the puerperium in order to determine when DD levels return to values obtained in non-pregnant women and can again be used in the exclusion of VTE.

PATIENTS AND METHODS

After uncomplicated pregnancies, 150 women delivering at term either vaginally (n = 100) or by cesarean section (n = 50) were included. DD levels were measured immediately following delivery and next at days 1, 3, 10, 30 and 45.

RESULTS

There was a marked elevation of DD at delivery, especially when instrumental. All DD measurements were above 500 ng mL(-1) at delivery, at day 1 and at day 3 postpartum. A sharp decrease in DD was observed between day 1 and day 3, followed by a slight increase at day 10. At day 30 and day 45, respectively, 79% and 93% of women in the vaginal delivery group and 70% and 83% in the cesarean group had levels below 500 ng mL(-1). Bleeding, breastfeeding and heparin prophylaxis did not modify DD levels significantly.

CONCLUSION

Using the Vidas DD new assay, our study provides reference intervals for DD in the postpartum period. Using a cut-off at 500 ng mL(-1), DD measurement for ruling out VTE was found to be useful again 4 weeks after delivery.

Diagnosis of pulmonary embolism: a cost-effectiveness analysis

OBJECTIVE

Pulmonary embolism is a major cause of maternal death. The work up for suspected pulmonary embolism is complex, with many potential diagnostic options. We performed a cost analysis to evaluate which of several diagnostic strategies was the most cost-effective with the least number of deaths from pulmonary embolism.

STUDY DESIGN

We created a decision tree to evaluate the following strategies: (1) Compression ultrasonography followed by anticoagulation (if there is a positive result) or secondary tests, ventilation perfusion scans or spiral computed tomography (if there is a negative result); high probability ventilation perfusion scans (a positive test result) resulted in anticoagulation; low probability ventilation perfusion scans (a negative test) resulted in no treatment; intermediate tests that resulted in a second test (computed tomography or pulmonary angiography). (2) Ventilation perfusion scans as a primary test followed by anticoagulation. (3) Computed tomography followed by anticoagulation (if there is a positive result). The following assumptions were made: The incidence of pulmonary embolism in pregnant women with suspected pulmonary embolism is 5%; 40% of documented pulmonary embolisms have a positive compression ultrasound result; 10% of ventilation perfusion scans for suspected pulmonary embolism are high probability, 60% are indeterminate, and 30% are low probability for pulmonary embolism; the sensitivity of computed tomography is 95%; the sensitivity of angiography is 98%. The assumed mortality rate of treated pulmonary embolism is 0.7% and of untreated pulmonary embolism in pregnancy is 15% (range, 10%-50%). The angiography-associated mortality rate is 0.5%, and the anticoagulation associated mortality rate is 0.2%. The following costs were used for the model: compression ultrasonography, 200.00 dollars; ventilation perfusion scans, 400.00 dollars; angiography, 1000.00 dollars; computed tomography, 500.00 dollars; and anticoagulation, 5982.00 dollars. With baseline assumptions, spiral computed tomography as the initial diagnostic regimen was found to be the most cost-effective at 17,208 dollars per life saved. Sensitivity analyses were performed over a wide range of assumptions that included alteration of the probability of pulmonary embolism, the sensitivity of computed tomography, ventilation perfusion scans, and compression ultrasonography, the cost of computed tomography, and the mortality rate of untreated pulmonary embolism. Our findings remained robust over a wide range of assumptions.

CONCLUSION

Suspected pulmonary embolism remains a diagnostic quandary. Our analysis indicated that spiral computed tomography offers the most cost-effective method for diagnosing this potentially fatal condition.

Deep vein thrombosis after elective cesarean section

INTRODUCTION

Pregnancy is associated with an overall 5-10 fold increased risk of venous thromboembolism (VTE). The absolute risk is highest during and shortly after delivery. Although operative delivery further increases the risk of VTE, there is no consensus on thromboprophylaxis after an elective cesarean. The aim of the present study was to investigate the frequency of symptomatic and asymptomatic deep venous thrombosis (DVT) in a low risk cesarean section population.

MATERIALS AND METHODS

Fifty-nine women undergoing elective cesarean section were screened for DVT using triplex Doppler sonography 3-5 days after delivery. Markers of activated coagulation were also followed and all women were screened for thrombophilia. Postoperative thromboprophylaxis was not given. During the same period all cases of symptomatic VTE were also recorded.

RESULTS

No DVT was detected by ultrasonography and no women developed symptomatic VTE during the six weeks follow-up period after delivery. Six women had thrombophilia. During the study period, a cesarean section was performed in 1067/5364 (20%) deliveries. Five of these women (0.47%) developed symptomatic pulmonary embolism, and all of these women had additional risk factors for VTE.

CONCLUSION

The risk of DVT among healthy pregnant women undergoing elective cesarean section is low, and general medical thromboprophylaxis is probably not justified.

Longitudinal evaluation of markers of endothelial cell dysfunction and hemostasis in treated antiphospholipid syndrome and in healthy pregnancy

OBJECTIVE

The purpose of this study was to determine whether primary antiphospholipid syndrome pregnancies are associated with endothelial cell activation in the maternal circulation.

STUDY DESIGN

Markers of endothelial cell activation were measured every 4 weeks during pregnancy in the blood of 23 women with primary antiphospholipid syndrome and 19 control subjects. All women with antiphospholipid syndrome received anticoagulant treatment. Plasma concentrations of plasminogen activator inhibitor type 1, tissue plasminogen activator, soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, and soluble thrombomodulin were determined by enzyme-linked immunoassay. Concentrations of prothrombin fragments 1+2 and D-dimers were also determined.

RESULTS

Three antiphospholipid syndrome pregnancies (13%) were complicated by intrauterine growth restriction and preeclampsia; one antiphospholipid syndrome pregnancy (4%) was complicated by preterm rupture of membranes. Six women with antiphospholipid syndrome (26%) had thrombotic events. Differences in concentrations of endothelial cell activation markers between antiphospholipid syndrome and control pregnancies were not significant.

CONCLUSION

Despite poorer pregnancy outcome, there was no evidence of greater endothelial cell activation in antiphospholipid syndrome pregnancies that were treated.

Treatment of acute pulmonary embolism during pregnancy with low molecular weight heparin: three case reports

We report three patients who presented with acute pulmonary embolism (PE) at gestational weeks 13-19. The diagnosis was based on spiral computer tomography of the lungs. In one of the cases, PE was submassive with signs of right ventricle overload. All of the patients were treated with low molecular weight heparin enoxaparine with an initial dose of 1 mg/kg twice daily during 1 month, and therafter with a reduced dose (80%). The target anti-activated factor X levels 3 h after injection were easily kept in the therapeutic range (0.5-0.9 IU/ml). In all cases, the symptoms were relieved within 4 days and no thrombotic or bleeding complications were observed during the rest of the pregnancy. We conclude that low molecular weight heparin seems to be an efficient and practical treatment of PE during pregnancy.

Treatment of deep venous thrombosis with low-molecular-weight heparin during pregnancy

Low-molecular-weight (LMW) heparins have been shown to be at least as effective as unfractionated (UF) heparin in the treatment of deep venous thrombosis (DVT) in nonpregnant subjects. LMW heparins have been shown to be safe when used during pregnancy as they do not cross the placenta. Up to now, they have been used mainly in thromboprophylaxis during pregnancy and rarely in the treatment of acute DVT in pregnant women. In a prospective observational study, we compared the effectiveness and safety of the LMW heparin, dalteparin, with UF heparin in the initial treatment (first week) of DVT during pregnancy. After confirmation of DVT by ultrasonography, 10 women were treated with UF heparin (25,430 IU/day, mean) and 21 women with dalteparin (16,000 IU/day, mean) for 7 days and, thereafter, all women were given treatment doses of LMW heparin for another 2 weeks. The dose was then gradually decreased and kept at a high prophylactic dose until delivery. One patient in the dalteparin group had recurrence of DVT 2 weeks after starting the treatment. No differences were observed between the groups in symptoms or bleeding complications during pregnancy and delivery. Our results indicate that LMW heparin is as effective and safe as UF heparin for the first week of treatment, but LMW heparin has the advantage of being easily administered and few laboratory controls are required.