Anaesthetic considerations and anticoagulation in pregnant patients with mechanical heart valves

Learning objectives.

By reading this article, you should be able to:

• •List the anticoagulation regimens recommended for use in pregnant patients with mechanical heart valves (MHVs).
• •Describe the significant maternal and fetal morbidity in pregnancies with MHVs.
• •Discuss the peripartum anaesthetic challenges in a pregnant patient taking therapeutic doses of anticoagulant drugs.
• •Highlight the need for a multidisciplinary team approach in the management of pregnant patients with MHVs.

Key points.

• •Pregnancy in patients with mechanical heart valves is associated with risks to the mother and fetus.
• •Counselling before pregnancy is vital to facilitate shared decision-making.
• •Pregnancies should be managed by a multidisciplinary team comprising an obstetrician, cardiologist, haematologist and anaesthetist.
• •Adverse events occur in 40% of pregnancies.
• •The risks of anaesthesia for emergency procedures during pregnancy should be considered.

Heart disease is the most common cause of maternal mortality in the UK.¹ Valvular heart disease occurring primarily from congenital heart disease or aortopathy in high-income countries and rheumatic heart disease in low-to-middle-income countries are responsible for high rates of complications in pregnancy.² Valve replacements in childhood and early adulthood are performed to limit complications and improve survival especially in moderate-to-severe stenotic or regurgitant valvular lesions.

Two types of prosthetic valves are used in clinical practice: biological (tissue) prosthetic heart valves (BHVs) and mechanical heart valves (MHVs).³ Biological heart valves do not require lifelong anticoagulation but have a finite lifespan and do undergo structural valve deterioration necessitating subsequent surgery. Mechanical heart valves are durable and do not typically need replacement. However, they carry a high risk of thromboembolic complications (TECs), and hence warrant indefinite anticoagulant therapy. A BHV is usually preferred in individuals of childbearing age who are planning pregnancy, but the risks and costs of repeating surgery may influence the decision to opt for a MHV.

The UK Obstetric Surveillance System study estimated the incidence of pregnant patients with MHVs to be 3.7 per 100,000 maternities.⁴ Vitamin K antagonists (VKAs) are the anticoagulants of choice in non-pregnant individuals with MHVs. However, as VKAs are teratogenic, other options must be considered during pregnancy. This paper discusses the options for anticoagulation in pregnant patients with MHVs; their impact on maternal and fetal outcomes; and the implications for labour analgesia, anaesthesia and peripartum care.

Maternal and fetal risks in pregnant patients with MHVs

Adverse maternal and fetal events are reported to occur in approximately 40% of pregnancies with MHVs.^4,5 Hence, the modified WHO (mWHO) risk stratification system considers pregnant patients with MHVs as extremely high risk (mWHO Class III).⁶

Maternal mortality ranges from 0.9% to 2.9% in pregnant patients with MHVs.⁷ Maternal morbidity in patients with MHVs is most commonly related to TECs and haemorrhage, the risk depending on the anticoagulation regimen used. In addition to the MHV, the prothrombotic state of pregnancy and systemic changes in coagulation and fibrinolytic pathways contribute to TECs.⁸ Thromboembolic complications affect 2.7–11.2% of pregnant patients with MHVs and can result in life-threatening MHV thrombosis.⁷ The risk of valve thrombosis is further increased with the mitral position of the MHV, multiple MHVs, ball-and-cage-type MHV, atrial fibrillation, severe left ventricular dysfunction, history of previous TEC, poor compliance with medications and smoking.⁹ Further, the increased hepatic and renal clearance in pregnancy affects the plasma concentrations of anticoagulants, potentially limiting the clinicians’ ability to titrate the anticoagulation regimen effectively.

Major maternal bleeding complicates 1.3–11% of pregnancies with MHVs and manifests as antepartum haemorrhage; postpartum haemorrhage (PPH) attributed to a higher Caesarean delivery (CD) rate; intra-abdominal bleeding after CD; and surgical wound haematomas requiring re-exploration, admission to critical care and prolonged hospital stay.^4,7 Other causes of morbidity and mortality in pregnant patients with MHVs include cardiac events (heart failure and arrhythmias) and stroke from intracranial thrombosis or haemorrhage, which are described in 7.7–10% and 1.4–7% of these pregnancies, respectively.^4,5,7

Fetal and neonatal complications are predominantly related to the use of VKAs in pregnancy. These complications include a 35.5% risk of miscarriage and fetal loss along with a 2.2% risk of embryopathy (nasal hypoplasia, stippled epiphyses, or both) in the first trimester or fetopathy (characterised by ocular and nervous system abnormalities) across the second and third trimesters.^7,10 All pregnant patients with MHVs, regardless of anticoagulation regimen, are at increased risk for preterm birth (up to 26.6%) and small-for-gestational-age infants (26.4%).⁷

Role of counselling before conception and the cardio-obstetrics (pregnancy heart) team

Given the significant maternal and fetal risks in pregnant patients with MHVs, the European Society of Cardiology (ESC) and the American Heart Association (AHA)/American College of Cardiology (ACC) recommend that these patients are cared for by a multidisciplinary cardio-obstetrics (‘pregnancy heart’) team, including an anaesthetist, high-risk obstetrician, cardiologist, haematologist and neonatologist in a specialised centre during pregnancy, and that all patients receive counselling before conception to discuss these risks and available treatment options.^6,11,12 During counselling before conception, the cardio-obstetrics team should:

• (i)Assess risk, focusing on cardiac, medical, social and environmental history.¹³
• (ii)Assess the functioning of the MHV and its thrombosis risk.
• (iii)Highlight the need for effective contraception when deferring pregnancy.
• (iv)Inform the risks and management options of an unplanned pregnancy, including termination.
• (v)Communicate the risks and benefits of available anticoagulation regimens, including the teratogenic effects of VKAs, and discuss the nature of intensive maternal and fetal surveillance during pregnancy.^6,11,14

Anticoagulation regimens for pregnant patients with MHVs

Vitamin K antagonists for all trimesters

Vitamin K antagonists (e.g. warfarin, acenocoumarol and phenocoumarol) have several advantages in pregnant patients. They are inexpensive, can be taken orally and are associated with the lowest TECs and maternal mortality of all anticoagulant regimens. International normalised ratio (INR) targets of 2–3 for aortic valves and 2.5–3.5 for mitral valves (depending on the risk factors), measured weekly, are recommended in pregnancy.^6,11 Limitations of VKAs include placental transfer introducing the risk of warfarin embryopathy and fetopathy, miscarriage, stillbirth and an anticoagulated fetus (deficient in vitamin K-dependent coagulation factors) susceptible to intracranial bleeding during childbirth.¹⁰

Heparin only for all trimesters

This regimen includes unfractionated heparin (UFH) or low-molecular-weight heparins (LMWHs), which have the advantage of not traversing the placenta and thus avoid the fetal risks associated with VKAs. For UFH, the dose has to be titrated i.v. or s.c. to achieve and maintain an activated partial thromboplastin time (aPTT) of twice the normal value. Giving and titrating UFH i.v. require hospitalisation and the need for ongoing i.v. access and monitoring. Using UFH s.c. is associated with a less predictable anticoagulant response because of poorer bioavailability from increased binding to plasma proteins, endothelial cells and macrophages compared with LMWHs.¹⁵ Prolonged use of UFH may also be associated with thrombocytopenia and osteoporosis. Hence, UFH i.v. is mainly used near the time of childbirth because of its short half-life. For LMWH, a twice-daily (therapeutic) dose-adjusted regimen initially based on maternal weight to maintain peak (4–6 h after the last dose) anti-Xa concentrations of 0.8–1.2 IU ml⁻¹ is recommended.^6,11 Data to support monitoring trough levels and sustaining concentrations ≥0.6 IU ml⁻¹ or more are limited.¹⁶ Compared with VKAs, disadvantages of LMWH include lack of established pregnancy-specific reference ranges to dose and monitor anti-Xa levels, the occurrence of TECs despite maintaining recommended anti-Xa levels, poor compliance with twice-daily dosing regimens, higher risk of maternal mortality and TECs and higher costs. Despite higher rates of maternal adverse event rates, better safety profile for the fetus of LMWH compared with VKAs and the ability to self-administer have resulted in its increased use in pregnancy, suggesting that prospective mothers may be willing to risk their well-being to avoid risks to their fetus.¹⁷

Sequential regimen

This regimen refers to using a VKA during the second and third trimesters whilst either LMWH or UFH is used in the first trimester. A VKA is changed to twice-daily LMWH (or titrated UFH) once pregnancy is confirmed, and after 12 weeks, a VKA is used. Although this regimen mitigates the effect of warfarin embryopathy, it does not reduce the risk of fetopathy and an anticoagulated fetus. Furthermore, TECs have been noted to occur on changing from one regimen to another.^5,6,9

Choice of anticoagulation regimen for pregnant patients with MHVs

There are no randomised trials comparing anticoagulation regimens during pregnancy. The best evidence comes from a meta-analysis, including approximately 2500 pregnancies in 1870 patients that provided summarised estimates of maternal mortality, TECs, live births and embryopathy or fetopathy (Table 1).⁷ Use of LMWH throughout pregnancy is associated with the highest rates of live births and no cases of embryopathy or fetopathy but a higher risk of maternal mortality and TECs, whilst the use of VKAs throughout pregnancy is associated with the lowest maternal mortality and TECs but a lower chance of live birth and a considerable risk of embryopathy and fetopathy. The rates of adverse maternal outcomes with the use of sequential regimens are between those of VKAs and LMWH used throughout pregnancy. The use of UFH throughout pregnancy appears to be associated with the highest maternal risk and lowest live births, although these risks have been estimated from a limited number of pregnancies. This meta-analysis also showed a significant difference in fetal outcomes with the use of <5 mg compared with >5 mg daily doses of warfarin (83.6% vs 43.9% livebirths and 2.3% vs 12.4% risk of embryopathy or fetopathy), suggesting that fetal risks of VKAs might depend on the dose.⁷ A thorough discussion of the risks, benefits and alternatives before proceeding with VKAs during pregnancy is integral to a patient’s care. The selection of the anticoagulation regimen should involve shared decision-making or the consideration of decision-analytic models that incorporate patients’ values and preferences.^10,18

Table 1.

Summary of maternal and fetal outcomes (percentage estimate 95% confidence intervals) with various anticoagulation regimens (modified from D'Souza and colleagues with permission from Oxford University Press).⁷ Estimates obtained through random-effects meta-analysis of findings from 2468 pregnancies. ∗Includes both unfractionated heparin and low-molecular-weight heparin in the first trimester and VKAs in the second and third trimesters. VKA, vitamin K antagonist.

Anticoagulation regimen during pregnancy	Maternal mortality	Maternal thromboembolic complications	Live births	Warfarin embryopathy and fetopathy
VKA throughout pregnancy	0.9 (0.1–1.6)	2.7 (1.4–4.0)	64.5 (48.8–80.2)	2.0 (0.3–3.7)
Sequential treatment∗	2.0 (0.8–3.1)	5.8 (3.8–7.7)	79.9 (74.3–85.6)	2.2 (0.2–4.3)
Low-molecular-weight heparin throughout pregnancy	2.9 (0.2–5.7)	8.7 (3.9–13.4)	92.0 (86.1–98.0)	Not applicable
Unfractionated heparin throughout pregnancy	Not estimable	11.2 (2.8–19.6)	11.2 (2.8–19.6)	Not applicable

Recommendations from the ESC (2018) and the AHA/ACC (2020) guidelines (Table 2) suggest using VKAs throughout pregnancy if the daily dose of warfarin is <5 mg and therapeutic levels of anticoagulation are achieved, although the flexibility of using a sequential regimen is also highlighted.^6,11 In cases where the daily warfarin dose to achieve therapeutic anticoagulation exceeds 5 mg, the ESC guidelines suggest a sequential regimen should be considered or LMWH may be considered for all three trimesters (where available, with appropriate peak and trough level monitoring) after informed consent from the patient. The ESC guideline also recommends that any changes in the anticoagulation regimen during pregnancy should be implemented in hospital.⁶

Table 2.

Summary of international recommendations for the management of anticoagulation in parturients with mechanical heart valves.^6,11 aPTT, activated partial thromboplastin time; INR, international normalised ratio; LMWH, low-molecular-weight heparin; UFH, unfractionated heparin; VKA, vitamin K antagonist.

Organisation	First trimester	Second and third trimesters
European Society of Cardiology 20186	Warfarin dose <5 mg day−1	Warfarin dose <5 mg day−1
	Continuation of VKA should be considered; monitor INR every one or two weeks or switch to dose-adjusted i.v. infusion of UFH (aPTT ≥2 control) or LMWH twice-daily regimen dose adjusted to weight may be considered.	Monitor INR every two weeks. VKA recommended for all women until 36 weeks.
	Give LMWH initially in-hospital with daily anti-Xa levels until target anti-Xa achieved, then weekly monitoring of post-dose anti-Xa level may be considered between 6 and 12 weeks.
	Target anti-Xa level 4–6 h post-dose 0.8–1.2 IU ml−1 (1–1.2 IU ml−1 for right-sided or mitral valve and 0.8–1.2 IU ml−1 for aortic valve). Monitor trough (pre-dose) anti-Xa level with dose adjustment to maintain trough level at >0.6 IU ml−1.
	Warfarin dose >5 mg day−1	Warfarin dose >5 mg day−1
	Monitor INR every two weeks. A switch to adjusted-dose i.v. UFH or LMWH should be considered between 6 and 12 weeks as stated.	VKA should be considered for all women until 36 weeks, or
	Continuation of VKA may be considered between 6 and 12 weeks after fully informed consent.	LMWH with anti-Xa level monitoring (both peak and trough levels) with dose adjustment may be considered in women after patient information and consent.
	Any changes in the anticoagulation regimen during pregnancy should take place in hospital.
American College of Cardiology/American Heart Association 202011	Warfarin dose ≤5 mg day−1	Warfarin dose ≤5 mg day−1
	Can continue warfarin in the first trimester after discussion of all the risks and benefits, or LMWH at least twice-daily regimen dose adjusted to weight and monitoring of post-dose anti-Xa level may be considered between 6 and 12 weeks. Target anti-Xa level 4–6 h post-dose 0.8–1.2 IU ml−1 with weekly monitoring.	Can be continued
	Warfarin dose >5 mg day−1	Warfarin dose >5 mg day−1
	LMWH at least twice-daily regimen dose adjusted to weight and weekly monitoring of post-dose anti-Xa level. Target anti-Xa level 4–6 h (post-dose) 0.8–1.2 IU ml−1 with weekly monitoring or switch to adjusted-dose UFH (aPTT ≥2 control as an i.v. infusion) if LMWH not available or cost prohibitive.	LMWH twice-daily regimen dose adjusted to weight and weekly monitoring of post-dose anti-Xa level may be considered. Target anti-Xa level 4–6 h post-dose 0.8–1.2 IU ml−1. For whom dose-adjusted LMWH is unavailable, warfarin can be continued.
		Low-dose aspirin 75 mg may be considered if needed for other indications (e.g. pre-eclampsia).

The AHA/ACC guidelines lean towards using LMWH (where available, with appropriate peak dose monitoring of anti-Xa levels) for all three trimesters in patients who need >5 mg warfarin to achieve therapeutic anticoagulation, although a sequential regimen is reasonable.¹¹ The use of LMWH throughout pregnancy in patients with MHVs seems to be increasing globally, highlighting that the choice of anticoagulation regimen is highly dependent on individual preferences.¹⁷

The AHA/ACC guidelines recommend using aspirin (in addition to the anticoagulation regimen) in this cohort only if needed for other indications (e.g. pre-eclampsia).¹¹ The ESC guidelines advise against the routine addition of aspirin to the anticoagulation regimen.⁶ This difference may result from the limited data on the efficacy and safety of adding aspirin to the anticoagulant in pregnant patients with MHVs.⁶ A decrease in mortality and TECs but a significant increase in haemorrhagic risk was noted with the combined use of aspirin and anticoagulant in non-pregnant individuals with MHVs.¹¹ The role of aspirin in lowering the risk of TECs, fetal growth restriction and preterm birth, especially in low-to-middle-income countries, needs to be explored further.¹⁹

Anaesthetic assessment of pregnant patients with MHVs

All pregnant patients with MHVs should have a consultation with an anaesthetist by 28 weeks’ gestation or as clinically indicated to discuss labour analgesia and anaesthesia, which is often dependent on the dose and timing of discontinuation of the anticoagulant. A clearly documented peripartum care plan is recommended, highlighting the anticoagulation regimen, mode of birth, analgesic and anaesthetic options, the preferred oxytocic agents and postoperative monitoring.^11,14 Box 1 summarises the key components of the anaesthetic assessment.

Box 1. Anaesthetic assessment of a parturient with an MHV.

• •Assess the aetiology of valve dysfunction; the type, location, number and sizes of MHVs; presence of any concurrent cardiac condition(s); history of previous embolic events (stroke); arrhythmia (atrial fibrillation); and experience with previous anaesthetic interventions.
• •Ascertain the presence, severity and progression of any cardiac symptoms during pregnancy (e.g. chest pain, fatigue, dyspnoea on exertion, paroxysmal nocturnal dyspnoea, haemoptysis, palpitations and syncope).
• •Evaluate the presence of other medical and obstetric conditions (e.g. pre-eclampsia and diabetes).
• •Review the anticoagulation regimen during pregnancy, including its therapeutic efficacy (e.g. international normalised ratio, activated partial thromboplastin time and anti-Xa levels) along with the cardiac medications the parturient may be taking (e.g. beta blockers or diuretics).
• •Document medication allergies (if any) and conduct an airway/spine examination.
• •Conduct a physical examination. Absence of ‘valve clicks’ and appearance of a new murmur could suggest valve thrombosis/obstruction.
• •Evaluate biomarkers (e.g. troponins and N-terminal pro-brain natriuretic peptide).
• •Review the baseline ECG and echocardiogram (transthoracic or transoesophageal) to assess valve area; valve mobility, presence or absence of valve thrombus and pannus (could suggest valve thrombosis); prosthetic valve regurgitation; and gradient across MHV.
• •Assess available imaging (e.g. cardiac CT or cardiac MRI).

Alt-text: Box 1

Peripartum management of anticoagulation in pregnant patients with MHVs

A planned vaginal birth is the preferred mode of delivery when possible (even with moderately impaired cardiac function) because of a lower risk of haemorrhage and shorter duration of hospital stay.⁶ The therapeutic anticoagulation regimen requires modification around childbirth to facilitate safe neuraxial analgesia or anaesthesia and decrease the risk of PPH and fetal bleeding (Fig 1).

Fig 1.

Anticoagulation in a pregnant patient with an MHV. ^aAmerican Heart Association (AHA) recommendation; ^bEuropean Society of Cardiology (ESC) recommendation ; ^cWarfarin dose <5 mg as per ESC and ≤5 mg as per AHA; LMWH - Low molecular-weight heparin - Target anti-Xa level 4–6 h post-dose 0.8–1.2 IU.ml⁻¹ with weekly monitoring. ESC also recommends monitoring trough (pre-dose) anti-Xa level and dose-adjustment to maintain trough level at >0.6IU ml⁻¹; UFH-unfractionated heparin (UFH) dose adjustment to attain activated partial thromoplastin time ≥2 control as an i.v. infusion; INR-international normalised ratio; ^dRisk assessment to be determined by the multidisciplinary team for the timimg and dose of UFH/LMWH considering the thrombotic and bleeding risks and recommendations for commencing anticogulation after the use of neuraxial anaesthia from the Association of Anaesthetists (AoA) or the American Society of Regional Anesthesia (ASRA) guidelines.

For pregnant patients using VKAs, the ESC guidelines recommend stopping VKAs at 36 weeks, whereas AHA guidelines recommend stopping them at least 1 week before the planned birth and transitioning to i.v. UFH or twice-daily LMWH regimen along with the recommended targets of aPTT/anti-Xa.^6,11 If using LMWH after 36 weeks, both guidelines advise that LMWH should be replaced by UFH i.v. at least 36 h before the planned birth. I.V. UFH needs to be discontinued 4–6 h before planned delivery.^6,11 In instances where cervical ripening/labour induction is expected to take 12–24 h, UFH should be continued for as long as is safely possible.

If a pregnant patient using a VKA presents in labour, a CD (using a general anaesthetic) is recommended to avoid bleeding risks from a vaginal birth in the anticoagulated fetus.^6,11 Consideration should be given to reversing VKA activity with four-factor prothrombin complex concentrate (PCC) and vitamin K. Giving PCC reduces the risk of maternal or fetal bleeding, although their use will not influence the mode of delivery (or anaesthesia in an emergency scenario), as there is a significant risk of fetal intracranial haemorrhage with vaginal birth.^10,20 Advantages of PCC over fresh frozen plasma include rapid correction of INR and fewer complications from fluid overload. Both regimens are potentially associated with increased risk of thrombosis.²⁰

Therapeutic LMWH should be substituted for UFH i.v. 36 h before planned birth as described earlier. Protamine has been used to reverse residual UFH activity (1 mg of protamine [100 IU]⁻¹ of UFH) and permit neuraxial analgesia/anaesthesia. However, it is seldom used for reversing UFH in patients with MHVs because of the potential risk of thrombosis and is reserved for emergent reversal in life-threatening haemorrhage. The benefit of protamine in reversing LMWH activity though is limited, and hence, its use is generally not recommended in patients receiving LMWH.²⁰

Neuraxial block in pregnant patients with MHVs

For patients with MHVs in labour, epidural analgesia is preferred, as it provides better pain relief and circumvents the need for general anaesthesia (GA) if an emergency CD is needed.²¹ Epidural catheters can be placed via an epidural, combined spinal–epidural or dural puncture epidural technique, although the latter is less commonly used in the UK.

The Association of Anaesthetists (AoA), the American Society of Regional Anesthesia (ASRA) and the Society for Obstetric Anesthesia and Perinatology have published guidelines for neuraxial block in patients taking anticoagulants.22, 23, 24 Treatment with a VKA should be changed to an LMWH or UFH regimen. For patients using VKAs, who present in labour or who need a CD, guidelines recommend an INR in the ‘normal’ range or ≤ 1.4 before performing a neuraxial block.^22,23 For a parturient receiving UFH, a minimum of 4 h without UFH is mandatory, with the aPTT within the normal range (and a normal platelet count) before a neuraxial block is attempted. For parturients receiving a therapeutic dosing of LMWH, a 24 h interval should elapse after the last dose of LMWH and the performance of neuraxial block.^21,22

Non-neuraxial labour analgesia techniques are usually used when the aforementioned stipulated time intervals have not been attained or for those patients who refuse a neuraxial block. Options include a 50:50% mixture of nitrous oxide: oxygen, opioids (including i.m. diamorphine or pethidine) and i.v. PCA (including fentanyl or remifentanil).

Intrapartum monitoring and antibiotics

Haemodynamic monitoring

In addition to non-invasive BP and pulse oximetry monitoring, temperature and fluid balance monitoring is recommended. Electrocardiography along with invasive BP monitoring using an arterial line may be necessary in individuals with myocardial dysfunction.

Antibiotics

The routine use of antibiotics for infective endocarditis prophylaxis in pregnant patients with MHVs during vaginal birth is not recommended by the ESC (because of limited evidence) and is not addressed in the AHA guidelines.^6,11 Decisions regarding the use of antibiotic prophylaxis for a vaginal birth should be based on individual risk factors and unit protocols. Both guidelines, however, do recommend giving antibiotics for pregnant patients with MHVs undergoing a dental procedure, and antibiotics are routinely used for a CD.

Anaesthetic considerations for caesarean delivery

In pregnant patients with MHVs, a CD is usually performed for an obstetric/fetal indication or if they present in labour while on VKAs and rarely for a cardiac indication (e.g. heart failure and ventricular dysfunction). Maintaining haemodynamic stability in the presence of MHVs is a priority irrespective of the type of anaesthesia utilised for CD.

Neuraxial anaesthesia was used in 64% of patients with MHVs in the UK Obstetric Surveillance System study.⁴ A spinal, epidural or a combined spinal–epidural anaesthesia technique using a local anaesthetic with an opioid (e.g. diamorphine or preservative-free morphine for postoperative analgesia) is commonly utilised to achieve a block to the T4 dermatome.

General anaesthesia is reserved in situations when time intervals since the last anticoagulant dose have not been adequate for safe neuraxial placement, those using VKAs in labour, for an emergency CD or in the presence of thrombocytopenia. A standard rapid-sequence induction technique with an anaesthetic agent, rapid-onset neuromuscular blocking agent, with or without a short-acting opioid can be used before tracheal intubation.

Oxytocic agents

Oxytocin, sublingual/oral or rectal misoprostol, prostaglandin F_2α or ergometrine can be used to maintain uterine tone in the absence of contraindications to their use.²⁵

Vasopressors

Phenylephrine is the vasopressor of choice to maintain systemic vascular resistance. Noradrenaline (norepinephrine) or ephedrine are other alternative vasopressors that can be utilised, although the latter is associated with maternal tachycardia and lower fetal umbilical artery pH compared with phenylephrine.²⁶

Monitoring and fluids

In addition to routine monitoring, invasive BP monitoring may be utilised to titrate vasopressors and facilitate blood tests and point-of-care testing. A central venous catheter or cardiac output monitoring is rarely necessary. Transthoracic echocardiography (in a conscious parturient) or transoesophageal echocardiography (in patients under GA) may be helpful in individuals with haemodynamic instability. Perioperative i.v. fluids are titrated to replace ongoing blood loss.

Postpartum care

Postoperative analgesia

Multimodal analgesia is usually provided with paracetamol and NSAIDs, which can be given with prophylactic doses of anticoagulants (in the absence of PPH).²⁴ The risks of bleeding need to be considered when giving regular NSAIDs to patients using therapeutic anticoagulation, and oral opioids may be used as necessary.²⁷ Use of a PCA is recommended for postoperative analgesia after GA.²⁸

High-dependency care

As the incidence of PPH is high and cardiac output usually peaks at 24–48 h after childbirth, individuals with MHVs are usually monitored in a high-dependency unit in the immediate postpartum period.

Lactation

Breastfeeding can be safely undertaken while using therapeutic doses of LMWH and VKAs.¹⁰

Anticoagulation

In the absence of PPH, UFH can be started i.v. 4 h after neuraxial anaesthesia or removal of the epidural catheter as per the AoA guidance.²² The ASRA guidance considers a 1-h interval sufficient.²³ For LMWH, a prophylactic (or even a therapeutic) dose can be given after 4 h of neuraxial block or catheter removal as per the AoA.²² If the neuraxial block was traumatic, AoA guidance recommends increasing this interval to 24 h for therapeutic LMWH. Recommendations from ASRA suggest delaying the postpartum prophylactic dose of LMWH for 12 h after neuraxial block (and 4 h after catheter removal). For therapeutic-dose LMWH, a 24 h interval after non-high-risk bleeding surgery and a 48–72 h interval after high-risk-bleeding surgery are recommended by ASRA.²³ Although these intervals relate to anticoagulation after neuraxial block, as the rate of PPH is high, maternity units may delay introducing therapeutic anticoagulation with UFH for 6–12 h and up to 24 h with therapeutic LMWH, especially after CD. This decision must involve the multidisciplinary team and be individualised, depending on the degree of surgical haemorrhage and the risk of MHV thrombosis. A prophylactic LMWH regimen with or without aspirin or UFH i.v. and titrated initially to a low-target nomogram (aPTT 50–70 s) for the first 24 h, followed by titration to a high-target nomogram (aPTT 55–85 s), may be used in the immediate postpartum period. The transition from UFH/LMWH to VKAs may be instituted in hospital 7 days after delivery.²⁰

The cardio-obstetrics team should continue to review the parturient postpartum in a dedicated outpatient follow-up clinic to ensure appropriate functioning of the MHV and compliance with appropriate dosing and monitoring of VKAs.

Special scenarios

Termination of pregnancy

Although medical termination with mifepristone/misoprostol up to 7 weeks’ gestation can be considered, this procedure may be associated with prolonged bleeding. Planned surgical dilatation and curettage may reduce this risk and the duration of interruption of anticoagulation, and it may be the preferred option for termination, thus requiring an anaesthetic intervention.⁶ Sedation or neuraxial anaesthesia (anticoagulation permitting) or GA can be safely used.

Thrombosed MHV

Thrombosed MHV can manifest as new-onset cardiac symptoms especially dyspnoea, fatigue or syncope. Urgent echocardiogram with input from a cardiologist is recommended. Echocardiogram features suggestive of MHV obstruction include an increase in velocity/gradient across the valve, decrease in valve area, increase in the pressure half-time and decrease in Doppler velocity index.¹¹ For pregnant patients with thrombosis involving right-heart MHVs, fibrinolysis with tissue plasminogen activator can be considered.^6,11 Surgery is recommended when anticoagulation fails, for haemodynamic instability or for patients with large non-obstructive thrombus complicated by embolism.

Stroke

Thrombotic and haemorrhagic strokes have been described in pregnant patients with MHVs. The lack of cardiac and neurology suites in some hospitals can often delay needed interventions. Close communication and collaboration between the cardio-obstetrics and neurology teams are paramount. Anaesthetists may be involved in the initial resuscitation, stabilisation and transfer to facilitate neuroimaging and to a critical care unit.²⁹

Conclusions

Multidisciplinary team involvement is integral to managing pregnant patients with MHVs to reduce maternal morbidity and mortality. As perioperative physicians, anaesthetists need to be consulted in a timely manner and should work collaboratively with obstetricians, cardiologists and haematologists to formulate individualised care plans. These plans should focus on risk stratification, assessment, haemodynamic monitoring, provision of safe analgesia and anaesthesia and preparation for obstetric and cardiovascular emergencies.

Declaration of interests

KB is a council member of the UK Maternal Cardiology Society and the obstetric anaesthetic lead for patients with heart disease in pregnancy at Saint Mary’s Hospital. NS and RD have no conflict of interest relevant to this publication.

Biographies

Kailash Bhatia FRCA EDRA DNB is a consultant anaesthetist at Saint Mary’s Hospital, Manchester, UK. His research interests include obstetric and regional anaesthesia.

Rohan D'Souza MD PhD FRCOG is a maternal–fetal medicine physician and associate professor of obstetrics and gynaecology with an interest in medical disorders in pregnancy and incorporating patients’ preferences into obstetric decision-making.

Nadine Shehata MD MSc FRCPC is a hematologist in the Medical Disorders of Pregnancy Program and the Head of the Transfusion Medicine Laboratory at Mount Sinai Hospital and professor in the Departments of Medicine, Laboratory Medicine and Pathobiology, Institute of Health Policy Management and Evaluation at the University of Toronto.

Matrix codes: 1A02, 2B01, 3B00

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