The effect of warfarin dosage on maternal and fetal outcomes in pregnant women with prosthetic heart valves

Maternal exposure to heparin products and risk of birth defects in the National Birth Defects Prevention Study

BACKGROUND

Heparin and low-molecular-weight heparin are the preferred anticoagulants during pregnancy as they do not cross the placenta. Although research on the safety of heparin products has been reassuring, previous studies have considered birth defects as a single outcome or by larger organ system and have not examined associations with specific birth defects.

METHODS

We analyzed data from the National Birth Defects Prevention Study, a multisite, population-based case-control study from 1997 to 2011. We used unconditional logistic regression with Firth's penalized likelihood to calculate adjusted odds ratios (ORs) and profile likelihood 95% confidence intervals (CIs) for defects with at least five exposed cases. For defects with 3-4 exposed cases, we estimated crude ORs and exact 95% CIs.

RESULTS

Of the 42,743 women in our analysis, 117 (0.4%) case and 44 (0.4%) control mothers reported using a heparin product in early pregnancy. The adjusted ORs ranged from 0.9 to 3.9 and were elevated for anorectal atresia (OR = 2.0, 95% CI = 0.8-4.3), longitudinal limb deficiency (3.5, 1.3-7.8), transverse limb deficiency (1.8, 0.6-4.3), atrioventricular septal defect (3.9, 1.4-9.0), and secundum atrial septal defect (2.2, 1.2-3.8).

CONCLUSIONS

We observed elevated associations for some birth defects, although heparin is a rare exposure, which limited our ability to evaluate many associations. Future studies that can explore specific birth defects and adequately control for confounding by indication are needed. Given that women with an indication for heparin products during pregnancy often need to take medication, one must remain mindful of the underlying risk of a birth defect that exists regardless of medication use.

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.

Mechanical Heart Valves, Pregnancy, and Bleeding: A Systematic Review and Meta-Analysis

Anticoagulant therapy is essential in pregnant women with mechanical heart valves to prevent valve thrombosis. The risk of bleeding complications in these patients has not gained much attention. This systematic review and meta-analysis investigate the prevalence of bleeding peri-partum and post-partum in women with mechanical heart valves and also investigate whether bleeding risk differed across anticoagulant regimens or according to delivery mode. The present study was conducted according to The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement. Studies reporting bleeding prevalence in pregnant women with mechanical heart valves receiving anticoagulant therapy were identified through PubMed and Embase on December 08, 2021. Data on bleeding complications, delivery mode, and anticoagulation therapy were extracted. A total of 37 studies were included, reporting 423 bleeding complications in 2,508 pregnancies. A meta-analysis calculated a pooled prevalence of 0.13 (95% confidence interval [CI]: 0.09-0.18) bleeding episodes per pregnancy across anticoagulant regimens. The combination of unfractionated heparin (UFH) and vitamin K antagonist (VKA) and single VKA therapy showed the lowest risk of bleeding (8 and 12%). Unexpectedly, the highest risk of bleeding was found in women receiving a combination of low-molecular-weight-heparin (LMWH) and VKA (33%) or mono-therapy with LMWH (22%). However, this could be dose related. No difference in bleeding was found between caesarean section versus vaginal delivery (p = 0.08). In conclusion, bleeding episodes are common during pregnancy in women with mechanical heart valves receiving anticoagulant therapy. A combination of UFH and VKA or VKA monotherapy showed the lowest risk of bleeding.

Society for Maternal-Fetal Medicine Consult Series #61: Anticoagulation in pregnant patients with cardiac disease

Pregnancy in individuals with a mechanical heart valve has been classified as very high risk because of a substantially increased risk of maternal mortality or severe morbidity. Lifelong therapeutic anticoagulation is a principal component of the medical management of mechanical heart valves to prevent valve thrombosis. Anticoagulation regimens indicated outside of pregnancy for patients with mechanical valves should be continued during pregnancy with the possibility of modifications based on the type of valve, the trimester of pregnancy, individual risk tolerance, and circumstances around the time of delivery. The purpose of this document is to provide recommendations regarding the management of anticoagulation for common cardiac conditions complicating pregnancy, including mechanical heart valves, atrial fibrillation, systolic heart failure, and congenital heart disease.

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.

Pregnancy outcome in women with mechanical prosthetic heart valvesat their first trimester of pregnancy treated with unfractionated heparin (UFH) or enoxaparin: A randomized clinical trial

Introduction: Pregnancy increases the risks of thromboembolism for the mother and fetus in patients with mechanical heart valves. The results of some studies have indicated that low molecular weight heparin (LMWH), in comparison with unfractionated heparin (UFH), leads to a lower incidence rate of thrombocytopenia and a decrease in bleeding.

Methods: The present randomized clinical trial involved 31 pregnant women with mechanical heart valves at their first trimester (0-14 weeks) of pregnancy. To perform the study, the patients were divided into two groups, i.e. group A (LMWH group-16 patients) and group B (UFH group-15 patients). The birth weight, mode of delivery, and gestational age at birth as well as the maternal and fetal complications were compared between the two groups.

Results: The mean age of mothers in the UFH and LMWH groups was 32.67±9.11 and 31.50±5.81years, respectively (P value > 0.05). Although the rate of maternal and fetal complications was higher in the UFH group as compared with the LMWH group, the observed difference was not significant (P value > 0.05).

Conclusion: LMWH can be regarded as a safer therapy for both the mother and fetus due to its lower number of refill prescriptions and fewer changes in the blood level.

High-Versus Low-Dose Warfarin-Related Teratogenicity: A Case Report and Systematic Review

OBJECTIVE

The optimal anticoagulant therapy during pregnancy in women with mechanical heart valves remains controversial. This study highlights a case of high-dose warfarin ingestion throughout pregnancy and performed a systematic review to assess rates of teratogenicity with high versus low warfarin dosing (≤5 mg daily).

METHODS

A literature search for all case reports and available literature was conducted in PubMed, Medline, and EMBASE up to December 2016 using medical subject heading terms "mechanical prosthetic valves," "pregnancy," "oral anticoagulants," "warfarin," "coumarins," "heparin, low-molecular-weight," and "thromboembolism." To be included, warfarin had to be administered anytime between 6 and 12 weeks of gestation with the dose being specified. The Newcastle-Ottawa Scale was used to assess quality of the cohort data.

RESULTS

The woman in the studied case received the highest reported warfarin doses throughout pregnancy (14.5-16.5 mg daily) and delivered a baby with no evidence of teratogenicity to the current age of 5 years. The study identified 23 case reports, with all demonstrating warfarin teratogenicity regardless of high-dose (n = 12) or low-dose (n = 11) warfarin. Twelve cohort studies identified a warfarin teratogenicity rate of 5.0%, with rates of 2.4% and 10.5% with low- and high-dose warfarin, respectively. Risk of bias was moderate (median Newcastle-Ottawa Scale score of 6) for all of the cohort studies.

CONCLUSION

Although a lower prevalence of warfarin-induced teratogenicity is reported with low-dose warfarin, a safe "cut-off" dose is misleading. Teratogenic risk with warfarin is unpredictable, mandating individual decisions regardless of the dose.

Safety and efficacy of adjusted-dose enoxaparin in pregnant patients with increased risk for venous thromboembolic disease

OBJECTIVE

To assess the efficacy and safety of anti-Xa guided dose-adjusted low molecular weight heparin (LMWH) thromboprophylaxis in at-risk pregnant women.

METHODS

This single-center retrospective study was conducted at a quaternary hospital in Johannesburg, South Africa. We analyzed clinical and laboratory data for pregnant patients referred between January 1, 1999, and May 1, 2017, with an increased risk of venous thromboembolic disease (VTED) and treated with prophylactic LMWH adjusted according to anti-Xa levels. The efficacy endpoint was pregnancy-related VTED and/or pregnancy loss despite anti-Xa guided dose-adjusted LMWH thromboprophylaxis.

RESULTS

We reviewed data for 113 consecutive pregnant patients with 151 pregnancies referred for prophylactic LMWH. Prevalence of pregnancy-related VTED was 1.3% (95% confidence interval [CI] 0.1-4.7), which is lower than that reported in the literature for fixed-dose thromboprophylaxis in similar at-risk groups. One venous thromboembolism event occurred in the antenatal period (despite adequate prophylaxis) and the second in the postpartum period (related to prolonged labor). Prevalence of pregnancy-related bleeding was 2% (95% CI 0.4-5.7) with all bleeding events considered to be minor and unrelated to LMWH therapy.

CONCLUSION

This study demonstrated the efficacy and safety of anti-Xa dose-adjusted LMWH thromboprophylaxis in at-risk pregnant patients.

State of the Art Management of Mechanical Heart Valves During Pregnancy

PURPOSE OF THE REVIEW

To review the management of women with mechanical heart valves during pregnancy, from preconception counseling through delivery with a summary of the latest guidelines.

RECENT FINDINGS

The hypercoagulability of pregnancy combined with the imperfect choices of anticoagulant agents contribute to a high risk of complications in pregnant women with mechanical heart valves. Valve thrombosis remains a major concern, much of which occurs during the first trimester transition to heparin-based products. The safest method of anticoagulation, with the best balance of maternal and fetal risk, is use of low-dose vitamin K antagonists, but only if therapeutic anticoagulation can be achieved with warfarin doses of ≤ 5 mg/day. Management of mechanical heart valves in pregnancy remains fraught with difficult decisions involving balancing of maternal and fetal risks as well as a high risk of maternal and fetal complications. Preconception counseling and planning is imperative. A risk-benefit discussion with the patient will help guide the choice of anticoagulation and outline the plan for safe delivery options. A multidisciplinary approach to management is advisable with close follow-up and care in a tertiary center.

Low-dose warfarin maternal anticoagulation and fetal warfarin syndrome

Fetuses exposed to warfarin during pregnancy are at an increased risk of developing an embryopathy known as fetal warfarin syndrome or warfarin embryopathy. The most consistent anomalies are nasal hypoplasia and stippling of vertebrae or bony epiphyses. Management of pregnant patients on anticoagulation is challenging. Current guidelines suggest the use of warfarin if the therapeutic dose is ≤5 mg/day. We report the case of a newborn with signs of warfarin embryopathy born from a mother anticoagulated with warfarin due to mechanical mitral and aortic heart valves. Warfarin was required at the dose of 5 mg/day and was withheld without medical advice between weeks 8 and 10 with no other anticoagulation. The newborn presented with skeletal abnormalities and a ventricular septal defect that have not required specific treatment during the first year of life. Low-dose warfarin is associated with a lower risk of warfarin-related fetopathy but the risk of embryopathy seems unchanged.

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.

Heart Disease and Pregnancy

Cardiac disease remains a major cause of morbidity and mortality in pregnant and post-partum women, although progress has been made, with specialist joint obstetric-cardiology clinics providing an integrated, safe and personalised service to these women. As a result, fewer non-specialist cardiologists are managing women in pregnancy with cardiovascular disease. The aim of this review is to provide a brief overview of current knowledge and practice in the field, with an emphasis on the major physiological changes which occur during pregnancy, focussing on progress through the trimesters, clinical assessment in pregnancy, management of delivery (concentrating on managed vaginal delivery), drug treatment, key conditions and risk assessment. The latter factor is particularly important in terms of being able to identify high-risk women earlier and to counsel them appropriately. Pregnant women with cardiovascular conditions can, with appropriate knowledge and counselling, be managed safely in specialist multidisciplinary services, but there is a need for cardiologists to understand the key changes and risks involved in pregnancy, delivery and the post-partum period.

Life associated with fear and worry: A major concern among the cardiac valve-replaced patients

BACKGROUND

Few attempts were made for alleviating the physical/psychological problems among the cardiac valve-replaced patients and no comprehensive study was done based on the experiences of such patients. This study was undertaken to describe the stressful experiences of the heart valve-replaced patients.

MATERIALS AND METHODS

In this qualitative study performed during 2012-2013 with a content analysis approach, 13 patients from Tehran and Kashan therapeutic centers participated. The study sampling was accomplished with purposeful sampling using a semi-structured interview that continued until data saturat ion. All interviews were recorded, and were immediately handwritten word by word and finally typewritten. Description and analysis of the data were done by Graneheim and Lundman content analysis.

RESULTS

One hundred and seventy-five primary codes were derived among the 680 codes taken from the participants interviewed. Using abstract and deep perception of the categories, 14 subcategories and 5 themes were derived. The themes are as follows: worry of care conditions, worry of life with the ongoing condition of having prosthetic cardiac valve, worry regarding the instability in life, fear of hospital, and fear of unknown factors. Each theme consisted of special subsidiary themes with specific functions.

CONCLUSIONS

The main themes of fear and worry about on losing the valve were identified and introduced in the cardiac valve-replaced patients. As the nature and function of these themes are different in different societies, recognition and discrete definition of them are necessary for care planning and promotion.

The experiences of "difficult life" in heart valve replaced patients

Background:

Several reports, however, not comprehensive, have been presented about the experiences of patients with replaced heart-valve.

Objectives:

This study explores the experiences of the patients with heart valve replacement.

Patients and Methods:

A qualitative research with a content analysis approach was carried out on the patients with cardiac valve replacement during the year 2012 and 2013. A purposeful sampling using a semi-structured interview and open-ended questions (with the main question of "What problems did you have after the valve replacement?" followed by the exploratory questions) were performed until the data saturation. All interviews were recorded, then transcribed and typed. The data analysis was done according to Grancheim and Lundmen content analysis using the MAXQDA software.

Results:

Of 22 interviews taken from 13 participants, 430 codes were taken. Out of them, after deleting the similar items, 162 initial, 18 subcategory, and 5 subsidiary themes (problematic exposure with valve replacement, continuity of some difficulties, aggravation of life problems, insufficient support, and following a perceived care) were extracted. Based on the abstract and deep perception of the categories, the main theme of "difficult life" was explored.

Conclusions:

Aggravation and the continuity of some physical problems, and insufficient support after the valve replacement make the life difficult for the patients. Identification of these problems is necessary for planning and improvement of the patients' care, life quality, and survival through consultations, rehabilitation and education.

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

Thromboembolism in pregnancy is an important clinical issue. Despite identification of maternal and pregnancy-specific risk factors for development of pregnancy-associated venous thromboembolism, limited data are available to inform on optimal approaches for prevention. The relatively low overall prevalence of pregnancy-associated venous thromboembolism has prompted debate about the validity of recommendations, which are mainly based on expert opinion, and have resulted in an increased use of pharmacological thromboprophylaxis in pregnancy and postpartum. A pragmatic approach is required in the absence of more robust data. Anticoagulation management of pregnant women with mechanical prosthetic heart valves is particularly challenging. Continuation of therapeutic anticoagulation during pregnancy is essential to prevent valve thrombosis. Warfarin, the most effective anticoagulant, is associated with adverse fetal outcomes, including embryopathy and stillbirth. Fetal outcome is improved with therapeutic-dose low-molecular-weight heparin, but there may be more thromboembolic complications. More intensive anticoagulation, targeting higher trough anti-Xa levels, may reduce the risk of valve thrombosis.

Limited dose warfarin throughout pregnancy in patients with mechanical heart valve prosthesis: a meta-analysis

The continuation of warfarin throughout pregnancy in patients with a mechanical valve prosthesis is a valid anticoagulation regimen, provided that warfarin dose does not exceed 5 mg/day. Two decades after being introduced, the efficacy and safety of this regimen merit evaluation. We performed a systematic review for cases published between January 1991 and January 2013. We compiled our prospective data on 55 pregnancies and calculated pooled estimates (95% confidence interval) of adverse foetal and maternal outcomes. Events were expressed as proportions of total pregnancies, except embryopathy and maternal death, which were related to the number of live births and number of patients, respectively. There were 494 eligible pregnancies reported in 11 studies. The rate of embryopathy was 0.9% (0.4-2.4%) and most of the 13.4% (8.4-24.7%) foetal losses were due to the 12.8% (7.7-22.7%) rate of spontaneous abortion. No maternal mortality was encountered (0-1.3%) but 0.6% (0.3-2%) prosthetic valve thrombosis, 1.8% (1.1-3.6%) total thromboembolic events and 3.4% (2-5.1%) major maternal bleeding events were recorded. Foetal loss, spontaneous abortions and foetal embryopathy dropped to 8.1% (2.9-13.7%), 7.3% (3.1-11.8%) and 0.6% (0.1-2.1%) among the 344 pregnancies (69.6%) observed in the 6 prospective studies (54.5%). Prosthetic valve thrombosis (0.6%; 01-2%), total thromboembolic (2.3%; 1.2-4.6%) and major bleeding events (2.9%; 1.8-6%) remained comparable with overall results. Foetal embryopathy and prosthetic valve thrombosis were not robust on sensitivity analysis, regardless of the study design. A prospective subgroup of 96 patients (19.4%) received smaller warfarin dose, through targeting a lower international normalized ratio (INR) between 1.5 and 2.5. The associated rate of foetal loss (2.1%; 0.5-6.9%) was significantly lower than that observed in the remaining patients targeting a higher INR between 2.5 and 3.5 (16.1%; 13.1-34.4%). Adverse maternal outcomes were also fewer but rates remained comparable. Limited dose warfarin throughout pregnancy was associated with improved foetal outcomes, without jeopardizing maternal safety. Foetal outcomes were better when patients were followed up prospectively or receiving smaller warfarin doses through targeting a lower INR than recommended (1.5-2.5). Large randomized controlled trials are mandatory to evaluate our findings.