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.

Diagnosis of Pulmonary Embolism in Pregnancy

Pulmonary embolism (PE) is a significant cause of obstetric morbidity and mortality. However, overdiagnosis related to excessive use of diagnostic testing is also associated with long-term major health issues, including impact on future pregnancies and subsequent health care. Accurate diagnosis of PE depends on the knowledge of prevalence of PE in the pregnant population, the a priori probability of a PE based on specific findings in a given patient, and understanding of the accuracy of computed tomography pulmonary angiography (CTPA), the dominant diagnostic modality employed for this diagnosis. Venous thromboembolism is widely considered to be more common in pregnancy. However, this term includes both deep venous thrombosis as well as PE. While the former appears to be more common, published data on the prevalence of PE in pregnancy show little or no increase relative to the general population. Given the published data on the sensitivity and specificity of CTPA, a positive reading is more likely to be a false positive unless the probability of a PE in a given patient is at least 5% (a 200-fold increase from baseline). Doubling the probability to 10% (a 400-fold increase) only improves the positive predictive value to approximately 67%. Strategies to refine the a priori probability of a PE in a given patient are detailed, including scoring systems and D-dimer measurements. A careful history and physical examination and thoughtful development of a differential diagnosis are key elements of clinical practice and should include both the likelihood of each possible diagnosis and the accuracy of diagnostic modalities. This approach should precede the application of a given algorithm. Such a structured approach can decrease utilization and limit false positive diagnoses without increasing morbidity or mortality. KEY POINTS: · Incidence of PE is lower than assumed.. · Incidence is critical for assessing predictive value of a test.. · Computed tomography angiography is likely overused in pregnancy.. · Clinical scoring and D-dimer have a role in PE diagnosis..

Rectus Sheath Hematoma Triggered by Post-cesarean Anticoagulant Therapy for Intraoperative Acute Pulmonary Thromboembolism: A Case Report

Anticoagulant therapy is essential for the prevention or treatment of peripartum venous thromboembolism (VTE). Administration of a therapeutic dose of anticoagulant immediately after cesarean section may result in the formation of a rectus sheath hematoma. A 32-year-old Japanese woman delivered twin neonates by cesarean section at 37+5 weeks of gestation. After the removal of the placenta, the patient suddenly complained of left anterior chest pain and dyspnea with hypotension and desaturation, requiring the administration of oxygen and vasopressors. Postoperative contrast-enhanced computed tomography (CT) revealed pulmonary embolism and massive right ovarian vein thrombosis (OVT). An inferior vena cava filter was placed and continuous intravenous heparin was started. A rectus sheath hematoma was noted on postoperative day 2 (POD 2). On POD 5, heparin administration was temporarily discontinued because of an enlarged rectus sheath hematoma. Approximately 24 hours later, the hemoglobin level recovered, and heparin administration was resumed. No further expansion of the hematoma was observed. When a rectus sheath hematoma is formed due to treatment with a therapeutic dose of anticoagulant immediately after cesarean section for peripartum VTE, temporary suspension of anticoagulant administration is reasonable to prevent further expansion of the hematoma without fatal complication.

Trimester-specific reference intervals of hemostasis biomarkers for healthy pregnancy

Physiological changes in hemostasis during pregnancy have been reported by several authors. This study aimed at establishing reference intervals for the hemostasis biomarkers thrombin-antithrombin complex (TAT), α2-plasmininhibitor-plasmin complex (PIC), thrombomodulin (TM) and tissue plasminogen activator-inhibitor complex (tPAI-C), in healthy pregnancies. After excluding outliers, a total of 496 healthy pregnant women (128 first-trimester, 142 second-trimester, 107 third-trimester and 119 pre-labor) and 103 healthy nonpregnant women were enrolled from Shenzhen Bao'an Women's and Children's Hospital. Hemostasis biomarkers, TAT, PIC, TM and tPAI-C, were measured by using a quantitative chemiluminescence enzyme immunoassay performed on HISCL automated analysers. The median and reference intervals (the 2.5th and 97.5th percentiles) were calculated to establish trimester-specific reference intervals for healthy pregnant women. The reference intervals for TAT, PIC, TM and tPAI-C in the first trimester were 0.7-7.6 1 µg/L, 0.2-0.9 mg/L, 2.8-11.0 TU/ml, and 1.2-6.5 1 µg/L, respectively. The reference intervals in the second trimester were 1.7-12.0 1 µg/L, 0.2-1.0 mg/L, 3.7-11.6 TU/ml, and 2.8-8.8 1 µg/L, respectively. The reference intervals in the third trimester were 2.7-16.1 1 µg/L, 0.1-1.4 mg/L, 2.9-12.9 TU/ml, and 1.9-8.0 1 µg/L, respectively. At pre-labor, the reference intervals were 4.8-32.9 1 µg/L, 0.2-1.9 mg/L, 4.2-12.6 TU/ml, and 2.8-15.4 1 µg/L, respectively. Gestational reference intervals for TAT, PIC, TM and tPAI-C in healthy pregnancies are provided, but only for TAT with increasing concentrations throughout pregnancy, the reference intervals for non-pregnant were not applicable.

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.

Reference intervals for coagulation parameters in non-pregnant and pregnant women

Established reference intervals (RIs) of coagulation parameters generally based on the general population are not applicable to specific women. In order to accurately evaluate the coagulation status of non-pregnant women and pregnant women, specific RIs should be established. Our study recruited 465 non-pregnant women and 1972 pregnant women aged 20-45 years. Eight tests including antithrombin (AT), protein C (PC), free protein S (fPS), lupus anticoagulant (LA), D-dimer, fibrin/fibrinogen degradation products (FDP), coagulation factor VII (FVII), and factor VIII (FVIII) were performed on ACL TOP automated coagulation instrument. The RIs for these tests were established in non-pregnant and pregnant women at different gestational weeks. Compared to the non-pregnant group, the medians of AT and fPS were lower, while the medians of PC, LA normalized ratio, D-dimer, FDP, FVII, and FVIII were higher. During pregnancy, AT and fPS activity showed a decreasing trend, with the increase of gestational age. PC activity, LA normalized ratio, D-dimer concentrations, FDP concentrations, FVII, and FVIII activity presented an increasing trend, with the increase of gestational age. The non-pregnant women-specific RIs and the gestational age-specific RIs of AT, PC, fPS, LA normalized ratio, D-dimer, FDP, FVII, and FVIII needed to be established for accurate clinical diagnoses.

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.

Changes in levels of coagulation parameters in different trimesters among Chinese pregnant women

Background

This article is to explore changes in levels of coagulation parameters in different trimesters among healthy pregnant women in China.

Methods

A total of 760 eligible women were enrolled (first‐trimester group: n = 183, second‐trimester group: n = 183, third‐trimester group: n = 263, non‐pregnant group: n = 131). Seven parameters including prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen (FIB), D‐dimer (DD), fibrinogen degradation products (FDP), and antithrombin III (ATIII), of all participants were collected. The non‐parametric 2.5th–97.5th percentiles reference intervals were calculated for each parameter.

Results

The reference intervals for FIB, PT, APTT, TT, FDP, DD, and ATIII at first trimester were 2.11–4.32 g/L, 10.90–13.85 s, 24.60–39.28 s, 12.95–15.88 s, 0.04–2.55 μg/mL, 0.03–1.15 μg/mL, and 75.57%‐125.31%, respectively. The reference intervals at second trimester were 2.31–4.77 g/L, 9.70–12.64 s, 24.16–35.43 s, 12.95–15.88 s, 0.15–7.40 μg/mL, 0.08–2.13 μg/mL, and 74.35%‐119.28%, respectively. For the third‐trimester, the intervals were 2.39–4.96 g/L, 9.20–11.95 s, 23.90–35.51 s, 13.41–18.00 s, 0.55–13.43 μg/mL, 0.15–3.60 μg/mL, and 71.61%‐118.29%, respectively. The third‐trimester group showed decreased PT, APTT, and ATIII and increased FIB, TT, DD and FDP as compared with the other groups.

Conclusion

In this study, level changes of coagulation parameters in different trimesters were observed. And the ranges for coagulation parameters were presented, which may provide some reference for clinicians to more accurately monitor the coagulation and fibrinolytic system in pregnant women.

Thrombogenicity assessment of Pipeline, Pipeline Shield, Derivo and P64 flow diverters in an in vitro pulsatile flow human blood loop model

Flow diversion is a disruptive technology for the treatment of intracranial aneurysms. However, these intraluminal devices pose a risk for thromboembolic complications despite dual antiplatelet therapy. We report the thrombogenic potential of the following flow diversion devices measured experimentally in a novel human blood in-vitro pulsatile flow loop model: Pipeline™ Flex Embolization Device (Pipeline), Pipeline™ Flex Embolization Device with Shield Technology™ (Pipeline Shield), Derivo Embolization Device (Derivo), and P64 Flow Modulation Device (P64). Thrombin generation (Mean ± SD; μg/mL) was measured as: Derivo (28 ± 11), P64 (21 ± 4.5), Pipeline (21 ± 6.2), Pipeline Shield (0.6 ± 0.1) and Negative Control (1.5 ± 1.1). Platelet activation (IU/μL) was measured as: Derivo (4.9 ± 0.7), P64 (5.2 ± 0.7), Pipeline (5.5 ± 0.4), Pipeline Shield (0.3 ± 0.1), and Negative Control (0.9 ± 0.7). We found that Pipeline Shield had significantly lower platelet activation and thrombin generation than the other devices tested (p < .05) and this was comparable to the Negative Control (no device, p > .05). High resolution scanning electron microscopy performed on the intraluminal and cross-sectional surfaces of each device showed the lowest accumulation of platelets and fibrin on Pipeline Shield relative to Derivo, P64, and Pipeline. Derivo and P64 also had higher thrombus accumulation at the flared ends. Pipeline device with Phosphorylcholine surface treatment (Pipeline Shield) could mitigate device material related thromboembolic complications.

Thrombogenicity assessment of Pipeline Flex, Pipeline Shield, and FRED flow diverters in an in vitro human blood physiological flow loop model

Endovascular treatment of intracranial aneurysms with endoluminal flow diverters (single or multiple) has proven to be clinically safe and effective, but is associated with a risk of thromboembolic complications. Recently, a novel biomimetic surface modification with covalently bound phosphorylcholine (Shield Technology™) has shown to reduce the material thrombogenicity of the Pipeline flow diverter. Thrombogenicity of Pipeline Flex, Pipeline Shield, and Flow Redirection Endoluminal Device (FRED) in the presence of human blood under physiological flow conditions—in addition to relative increase in thrombogenicity with multiple devices—remains unknown and was investigated here. Thrombin generation (mean ± SD; μg/mL; thrombin–antithrombin complex or TAT) was measured as FRED (30.3 ± 2.9), Pipeline (13.9 ± 4.4), Pipeline Shield (0.4 ± 0.3), and negative control (no device; 0.1 ± 0.0). Platelet activation (mean ± SD; IU/μL; beta‐thromboglobulin or βTG) was measured as FRED (148 ± 45), Pipeline (92.8 ± 41), Pipeline Shield (16.2 ± 3.5), and negative control (2.70 ± 0.16). FRED was significantly more thrombogenic than Pipeline and Pipeline Shield (p < 0.05) for TAT. Additionally, Pipeline Shield had significantly lower TAT and βTG than the other devices tested (p < 0.05) and these were comparable to the negative control (p > 0.05). TAT and βTG scaled proportionately with multiple Pipeline devices (N = 6) but was unaffected by multiple Pipeline Shield (N = 6) devices—the latter being statistically similar to negative control (p > 0.05). © 2018 The Authors. Journal Of Biomedical Materials Research Part A Published By Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3195–3202, 2018.

A label-free electrochemical aptasensor based on magnetic biocomposites with Pb2+-dependent DNAzyme for the detection of thrombin

Herein, a novel magnetic biocomposite (Fe₃O₄@Au-S1/S2) was applied to analyze thrombin. The Fe₃O₄@Au-S1/S2 consisted of Fe₃O₄@Au nanoparticles (Fe₃O₄@Au NPs) as carriers for magnetic separation and magnetic field-induced self-assembly, thiolated complementary strand (S1) anchored based on Au-S bond and thrombin binding aptamer (S2) as a recognition element. As a redox indicator, methylene blue (MB) can be adsorbed to DNA anchored on the surface of Fe₃O₄@Au NPs by electro-static interaction. In the absence of thrombin, MB were adsorbed on double-stranded DNA (S1/S2) which anchored on Fe₃O₄@Au NPs and a high electrochemical signal of MB was recorded by Differential pulse voltammetry. Conversely, the complementary strand (S1) exposed after thrombin competitively bonded with aptamer. The introduction of Pb²⁺-dependent DNAzyme (S3) split S1 at specific rA site, resulting in the significantly decreased adsorption capacity of MB. Thus, the thrombin detection could be recorded by monitoring the electrochemical signal reduction of MB through incubation of thrombin with S3. This method exhibited a high sensitivity toward thrombin with a broad linear range from 5 pmol L^-1 to 5 nmol L^-1 and a limit of detection of 1.8 pmol L^-1.