Thromboembolism in pregnancy: challenges and controversies in the prevention of pregnancy-associated venous thromboembolism and management of anticoagulation in women with mechanical prosthetic heart valves

Venous Thromboembolism Risk Assessment Models in Obstetrics: A Review of Current Practices and Future Directions

Pregnancy is a major risk factor for venous thromboembolism (VTE) and its associated complications. The hypercoagulable state in both the antenatal and postnatal periods contributes to thromboembolism and continues to be a leading cause of maternal morbidity and mortality worldwide. The non-specific signs and symptoms of VTE in pregnancy and the lack of specific Risk Assessment Models (RAMs) propose a diagnostic challenge in the obstetric population. This review aims to discuss and compare existing RAMs and highlights the important challenges of using established RAMs in obstetric patients. It also emphasizes the importance of enhancing and individualizing RAMs in obstetrics to improve maternal healthcare. KEY POINTS: · VTE is a major complication of pregnancy, associated with increased maternal morbidity and mortality.. · VTE RAMs lack sensitivity and specificity in stratifying VTE risk in pregnancy.. · Validating VTE RAMs in the obstetric population aims to improve maternal outcomes..

Treasure to the mother and threat to the fetus: case report of warfarin-associated fetal intracranial hemorrhage and review of literature

In patients with mechanical heart valve protheses, warfarin is usually recommended because of its exceptional anticoagulation effects. However, warfarin can cross the placenta, leading to teratogenicity and even catastrophic hemorrhage in the fetus. The present article describes a case of warfarin-associated fetal intracranial hemorrhage. The patient was a woman in her early 30s. At the age of 11 years, she had undergone aortic valve replacement (mechanical) for aortic regurgitation. Since then, she had been taking oral warfarin. During her pregnancy, her prothrombin time-international normalized ratio was maintained between 1.5 and 2.5. At 35 weeks of gestation, fetal ultrasonography revealed an intracranial mass in the left hemisphere. An emergency cesarean section was performed because fetal intracranial hemorrhage was suspected. A male infant was delivered with a 1- 5-, and 10-minute Apgar score of 1, 5, and 7, respectively. Cranial computed tomography revealed multiple hemorrhage sites with newly emerged bleeding spots. In patients with mechanical heart valve protheses, obstetricians face the dilemma of individual-patient differences and the difficulty of intensive monitoring of the coagulation parameters in the fetus. Tailor-made anticoagulation therapy and a more intensive ultrasonic monitoring strategy, even that involving regular magnetic resonance imaging, are necessary in these patients.

Outcomes in Pregnant Women with Valvular Heart Disease from Portuguese-Speaking African Countries Treated in Portugal through an International Agreement of Health Cooperation

Aims

We performed a clinical audit of maternal and fetal outcomes in pregnant women with valvular heart disease (VHD) from Portuguese-speaking African countries who were transferred for their care, during a twenty-year period, through a memorandum of agreement of international cooperation.

Methods and results

A retrospective analysis of 81 pregnancies in 45 patients with VHD (median age 24, interquartile range 22-29 years) from 2000 to 2020 was performed. The main outcome measures were maternal cardiovascular and fetal outcomes. History of rheumatic heart disease was present in 60 (74.1%) pregnancies. Most were in New York Heart Association (NYHA) functional class I or II; at the first evaluation, 35 (43.2%) were on cardiac medication and 49 (60.5%) were anticoagulated. Forty-eight pregnancies had at least one valvular prosthesis, including 38 mechanical heart valves. During pregnancy, deterioration in NYHA functional class occurred in 35 (42.0%), and eight (9.9%) patients required initiation or intensified cardiac medication. Mechanical valve thrombosis complicated four (4.9%) pregnancies, all cases on heparin, and resulted in one maternal death. Haemorrhagic complications happened in 7 (8.6%) anticoagulated patients, in the immediate postpartum or puerperal period. The 81 pregnancies resulted in 56 (69.1%) live births, while miscarriage and fetal malformations occurred in 19 (23.5%) and 12 (14.8%) pregnancies, respectively. In multivariate analysis, vitamin K antagonist therapy was the only independent predictor of an unsuccessful pregnancy (p = 0.048).

Conclusion

In a high-income country, successful pregnancy was possible with low rate of maternal events in women with VHD transferred from five low-middle income countries in Africa. The use of anticoagulation with a vitamin K antagonist was associated with an unsuccessful pregnancy.

Anticoagulation for mechanical heart valves during pregnancy: A case report and a literature review

RATIONALE

Most previous treatment guidelines for pregnant women with mechanical heart valves recommend that low molecular weight heparin (LMWH) should be applied once every 12 hours and only as required to reach peak anti-Xa levels of approximately 1.0 to 1.2 IU/mL, but it is commonly associated with subtherapeutic trough levels, consequently with an inadequate level of anticoagulation. Our case report here together with a literature review suggests that dose-adjusted (Target trough anti-Xa levels of 0.6 to 0.7 IU/mL and with peak anti-Xa levels of around 1.0 to 1.2 IU/mL or < 1.5 IU/mL) LMWH should be given thrice daily throughout pregnancy. In addition, the findings of this rare case indicate that a combination of LMWH and warfarin is effective in the treatment of small thromboses in pregnancy.

PATIENT CONCERNS

In the 1st trimester of pregnancy, a 28-year old pregnant female with a mechanical valve had a significant increase in the aortic valve flow rate and suspected mechanical valve thrombosis.

DIAGNOSES

The peak velocity of the pregnant female aortic mechanical valve increased, and mechanical valve thrombosis was suspected.

INTERVENTIONS

We adjusted the enoxaparin sodium dose every 12 hours to 1 injection every 8 hours, with a total daily dose of 160 mL. Based on the original application of LMWH, warfarin (3 mg/day) was recommended.

OUTCOMES

The pregnant woman delivered a live baby by cesarean section, and the peak flow velocity of the mechanical valve in the aortic position was reduced to nearly equivalent to the patient's pre-pregnancy status. The mother and the baby were in good health at the time of discharge.

LESSONS

LMWH is administered twice daily, and anti-Xa trough levels are mostly in a subtherapeutic state, which may lead to insufficient anticoagulation and thrombosis. Dose-adjusted LMWH thrice daily throughout pregnancy is the recommended treatment for pregnant women with mechanical heart valves. The combination of LMWH and warfarin exhibited good efficacy for the treatment of small thromboses.

Management of pregnant patients with pulmonary arterial hypertension

Pregnant individuals with pulmonary arterial hypertension (PAH) have significantly high risks of maternal and perinatal mortality. Profound changes in plasma volume, cardiac output and systemic vascular resistance can all increase the strain being placed on the right ventricle, leading to heart failure and cardiovascular collapse. Given the complex network of opposing physiological changes, strict contraception and reduction of hemodynamic fluctuations during pregnancy are important methods of minimizing the risk of maternal mortality and improving the outcomes following pregnancy. In this review, we discuss the recent research progress into pre-conception management and the various therapeutic strategies for pregnant individuals with PAH.

Alternatives to Low Molecular Weight Heparin for Anticoagulation in Pregnant Women with Mechanical Heart Valves in Middle-Income Countries: A Cohort Study

Objective

To compare cardiac complications and pregnancy outcomes in women with mechanical heart valves (MHVs) on two different anticoagulation regimens in a middle-income country.

Methods

We conducted a retrospective cohort study comparing outcomes in pregnant women with MHVs that received vitamin K antagonists (VKAs) throughout pregnancy versus sequential anticoagulation (heparins in the first trimester and peripartum period and VKAs for the remainder of pregnancy), at a tertiary centre in South India, from January 2011 to August 2020.

Results

We identified 138 pregnancies in 121 women, of whom 32 received VKAs while 106 were on sequential anticoagulation. There were no differences between groups with regard to maternal deaths [0 vs. 6 (5.7%), p = 0.34], thromboembolic events [2 (6.3%) vs. 15 (14.2%), p = 0.36], haemorrhagic complications [4 (12.5%) vs. 12 (11.3%), p = 0.85], cardiac events [1 (3.1% vs. 17 (16%), p = 0.07], spontaneous miscarriages [5 (15.6%) vs. 13 (12.3%), p = 0.62], stillbirths [0 vs. 5 (5.4%), p = 0.581] or neonatal deaths [2 (8.7%) vs. 1 (1.1%), p = 0.11]. Both cases of warfarin embryopathy received >5 mg warfarin in the first trimester. Thromboembolic events were associated with subtherapeutic doses of heparin in the first and third trimesters and the early postpartum period. Fetal growth restriction and preterm birth complicated 34 (29.3%) and 26 (22.4%) pregnancies respectively.

Conclusion

Pregnancy complications associated with MHVs in middle-income countries may be reduced by multidisciplinary surveillance, avoiding first-trimester warfarin if daily doses >5 mg and ensuring therapeutic levels of heparin during bridging in the first and third trimesters and peripartum period. Administration of low-dose aspirin should be considered as this may prevent placentally-mediated complications of pregnancy.

Highlights

Pregnancy complications associated with MHVs in LMICs may be reduced by multidisciplinary surveillance, avoiding first-trimester warfarin if the daily dose is >5 mg, ensuring therapeutic levels of heparin in the first trimester and peripartum period.Placentally-mediated complications of pregnancy can be prevented by administering low-dose aspirin.Vitamin K antagonists or sequential regimen can be used as suitable alternatives to LMWH for anticoagulation in pregnant women with MHVs.

Valvular Heart Disease in Pregnancy: Anticoagulation and the Role of Percutaneous Treatment

Valvular heart disease is present in about 1% of pregnancies, and it poses a management challenge as both fetal and maternal lives are at risk of complications. Pregnancy is associated with significant hemodynamic changes, which can compromise the cardiac status in women with underlying valvular disorders. Management of valvular heart diseases has undergone considerable innovation and advancement with newer techniques, approaches and devices being employed. The decision regarding the management of anticoagulation, especially in patients with prosthetic valves, raises distinct questions and challenges. In this review, we describe the management of common valvular heart diseases encountered during pregnancy, role of percutaneous catheter based therapeutic interventions, the importance of a team-based approach, and the challenges given existing gaps in the literature.

ABO O gene frequency increase in the US might be causing increased maternal mortality

Maternal mortality rate has increased in the United States over the past 30 years from 16 deaths per 100,000 births to 28 deaths per 100,000 births while the rest of the world is experiencing declining rates. Increasing obesity and c-section rates in the US have been cited as contributing factors needing remediation, and because of the two to three fold difference in maternal mortality rates in non-Hispanic black women compared to white women, inequality and implicit racial bias has been targeted as well for remediation. Using an epidemiologic approach, a hypothesis here brought to bear is that US immigration policy changes over the past 50 years have brought changes in the gene pool that have caused increasing obstetric hemorrhage and other causes of maternal death. ABO gene frequencies have changed in the US during this time such that ABO O, a gene associated with hemorrhage and mortality in pregnancy, has increased in frequency in the US thus increasing population maternal mortality rate. Using mendelian randomization logic, noting the increase in ABO O gene in the US population over the past 30 years and the association of ABO O gene with both hemorrhage and lower longevity, the increase in frequency of the ABO O gene in the past 30 years in the US population might be causative of an increase in maternal mortality rate. Consequences of this hypothesis would include recognition of the role of ABO gene and thus ABO blood group in prediction of risk of obstetric hemorrhage. Thus those at risk on this basis would be under high surveillance and would have medications and treatment strategies readily available. While research on ABO gene and pregnancy has been done, much of the research is being done in countries other than the US, and given the increasing mortality in the US as well as the role that ABO gene may have in that, further research needs to be done in US populations to quantify risk for all adverse events in pregnancy related to ABO blood type including hemorrhage as well as inter-related causes including pre-eclampsia, cardiovascular disease, thromboembolic disease and infection.

Effectiveness and safety of thromboprophylaxis with enoxaparin for prevention of pregnancy-associated venous thromboembolism

Essentials Thromboprophylaxis is offered to women considered to be at risk from pregnancy-associated venous thromboembolism (PA-VTE) but there is a suggestion that standard doses of low-molecular-weight heparin may not be effective. We conducted a large observational cohort study reviewing maternal outcomes in women who received extended thromboprophylaxis with enoxaparin for prevention of PA-VTE. We report a low rate of breakthrough VTE in women, the majority of whom received standard doses of enoxaparin. High rates of postpartum hemorrhage are reported in our cohort. Our data do not strongly support a move to increase doses of thromboprophylaxis for prevention of PA-VTE and raise the possibility that higher doses may increase bleeding complications and limit women's access to neuraxial analgesia/anesthesia.

BACKGROUND

Low-molecular-weight heparin is used to prevent pregnancy-associated venous thromboembolism (PA-VTE), but there are limited data to inform which women require thromboprophylaxis in pregnancy and debate about which low-molecular-weight heparin dose is effective and safe.

AIMS

To evaluate the efficacy and rate of complications using enoxaparin for thromboprophylaxis in a cohort of women at risk of PA-VTE managed between 1999 and 2014 at National Women's Hospital, a tertiary obstetric referral center in Auckland, New Zealand.

METHODS

A retrospective, observational study of women who received thromboprophylaxis with enoxaparin for prevention of PA-VTE while under the care of the obstetric or maternal fetal medicine team.

RESULTS

A total of 172 pregnancies in 123 women were identified. A single daily dose of 40 mg enoxaparin was used in 94.8% of pregnancies. Two breakthrough PA-VTEs occurred (1.2% [95% confidence interval, 0.32-4.14]). Postpartum hemorrhage ≥500 mL was reported in 36.6% of births and postpartum hemorrhage ≥1000 mL in 9.3% of births. Only four women were transfused. Neuraxial analgesia/anesthesia was used in 52.4% of births, including 39.6% of vaginal births.

CONCLUSION

Use of standard doses enoxaparin thromboprophylaxis in our cohort was effective at preventing PA-VTE. Neuraxial analgesia/anesthesia was used frequently during labor and birth;, using higher doses of enoxaparin may limit access to this. Postpartum hemorrhage was common and higher doses of thromboprophylaxis may increase obstetric bleeding complications. These data do not suggest an urgent need to consider higher doses of enoxaparin for thromboprophylaxis in this clinical setting.

Anticoagulation for pregnant women with mechanical heart valves: a systematic review and meta-analysis

Aims

To review maternal and foetal outcomes in women with mechanical heart valves (MHVs) treated with vitamin-K antagonists (VKAs), first-trimester heparin followed by VKAs (sequential treatment), low molecular weight heparin (LMWH) and unfractionated heparin (UFH) during pregnancy, in order to inform practice.

Methods and results

Medline, Embase and Central were searched from inception until February 2016. Two reviewers independently screened 1786 titles, reviewed 110 full-texts and extracted data and assessed risk-of-bias from 46 articles. Pooled incidence (95% confidence intervals) was calculated for maternal and foetal outcomes. Included studies had a moderate or high risk-of-bias. With VKAs, sequential treatment and LMWH, maternal mortality occurred in 0.9% (0.4–1.4), 2.0% (0.8–3.1) and 2.9% (0.2–5.7), thromboembolic complications in 2.7% (1.4–4.0), 5.8% (3.8–7.7) and 8.7% (3.9–13.4), livebirths in 64.5% (48.8–80.2), 79.9% (74.3–85.6) and 92.0% (86.1–98.0) and anticoagulant-related foetal/neonatal adverse events (embryopathy or foetopathy) in 2.0% (0.3–3.7), 1.4% (0.3–2.5) and 0%, respectively. When UFH is used throughout pregnancy, 11.2% (2.8–19.6) suffered thromboembolic complications. Foetal loss and adverse events occurred with first-trimester warfarin doses ≤ 5 mg/day, although there were more livebirths [83.6% (75.8–91.4) vs. 43.9% (32.8–55.0)] and fewer foetal anomalies [2.3% (0.7–4.0) vs. 12.4% (3.3–21.6)] with lower doses than with warfarin > 5 mg/day.

Conclusions

VKAs are associated with fewest maternal complications but also with fewest livebirths. Sequential treatment does not eliminate anticoagulant-related foetal/neonatal adverse events. LMWH is associated with the highest number of livebirths. The safety of UFH throughout pregnancy and first-trimester warfarin  ≤ 5 mg/day remains unconfirmed.

Anticoagulation for the Pregnant Patient with a Mechanical Heart Valve, No Perfect Therapy: Review of Guidelines for Anticoagulation in the Pregnant Patient

Heart valve replacement with a mechanical valve requires lifelong anticoagulation. Guidelines currently recommend using a vitamin K antagonist (VKA) such as warfarin. Given the teratogenic effects of VKAs, it is often favorable to switch to heparin-derived therapies in pregnant patients since they do not cross the placenta. However, these therapies are known to be less effective anticoagulants subjecting the pregnant patient to a higher chance of a thrombotic event. Guidelines currently recommend pregnant women requiring more than 5 mg a day of warfarin be switched to alternative therapy during the first trimester. This case report highlights a patient who was switched to alternative therapy during her first pregnancy and suffered a devastating cerebrovascular accident (CVA). Further complicating her situation was during a subsequent pregnancy; this patient continued warfarin use during the first trimester and experienced multiple transient ischemic attacks (TIAs). This case highlights the increased risk of thrombotic events in pregnant patients with mechanical valves. It also highlights the difficulty of providing appropriate anticoagulation for the pregnant patient who has experienced thrombotic events on multiple anticoagulants.

Consensus Document of the Italian Association of Hospital Cardiologists (ANMCO), Italian Society of Pediatric Cardiology (SICP), and Italian Society of Gynaecologists and Obstetrics (SIGO): pregnancy and congenital heart diseases

The success of cardiac surgery over the past 50 years has increased numbers and median age of survivors with congenital heart disease (CHD). Adults now represent two-thirds of patients with CHD; in the USA alone the number is estimated to exceed 1 million. In this population, many affected women reach reproductive age and wish to have children. While in many CHD patients pregnancy can be accomplished successfully, some special situations with complex anatomy, iatrogenic or residual pathology are associated with an increased risk of severe maternal and fetal complications. Pre-conception counselling allows women to come to truly informed choices. Risk stratification tools can also help high-risk women to eventually renounce to pregnancy and to adopt safe contraception options. Once pregnant, women identified as intermediate or high risk should receive multidisciplinary care involving a cardiologist, an obstetrician and an anesthesiologist with specific expertise in managing this peculiar medical challenge. This document is intended to provide cardiologists working in hospitals where an Obstetrics and Gynecology Department is available with a streamlined and practical tool, useful for them to select the best management strategies to deal with a woman affected by CHD who desires to plan pregnancy or is already pregnant.

Management of venous thromboembolism secondary to ovarian hyperstimulation syndrome: A case report documenting the first use of a superior vena caval filter for upper limb venous thromboembolism in pregnancy, and the difficulties and complications relating to anticoagulation in antenatal and peri-partum periods

The management of venous thromboembolism and subsequent pulmonary embolism in pregnancy remains hugely challenging. In this case, we report the first use of a superior vena caval filter in pregnancy as an adjunct to pharmacological anticoagulation. This is the first reported use of a superior vena caval filter in pregnancy. We discuss the complexities of managing thromboembolism in pregnancy and the peri-partum period.

Erythrocyte-platelet interaction in uncomplicated pregnancy

Maternal and fetal requirements during uncomplicated pregnancy are associated with changes in the hematopoietic system. Platelets and erythrocytes [red blood cells (RBCs)], and especially their membranes, are involved in coagulation, and their interactions may provide reasons for the changed hematopoietic system during uncomplicated pregnancy. We review literature regarding RBC and platelet membrane structure and interactions during hypercoagulability and hormonal changes. We then study interactions between RBCs and platelets in uncomplicated pregnancy, as their interactions may be one of the reasons for increased hypercoagulability during uncomplicated pregnancy. Scanning electron microscopy was used to study whole blood smears from 90 pregnant females in different phases of pregnancy. Pregnancy-specific interaction was seen between RBCs and platelets. Typically, one or more platelets interacted through platelet spreading and pseudopodia formation with a single RBC. However, multiple interactions with RBCs were also shown for a single platelet. Specific RBC-platelet interaction seen during uncomplicated pregnancy may be caused by increased estrogen and/or increased fibrinogen concentrations. This interaction may contribute to the hypercoagulable state associated with healthy and uncomplicated pregnancy and may also play a fundamental role in gestational thrombocytopenia.