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Practical practice points
1. A spectrum of cardiac disease exists that modifies the approach to peripartum care.
2. Vaginal delivery is preferred unless there is a fetal, obstetric, or cardiac indication for cesarean section.
3. Care needs to be taken in the third stage to avoid postpartum hemorrhage, hypotension, and pulmonary edema.
4. Communication between the woman and all members of the intrapartum team is of paramount importance to ensure a satisfactory outcome.
5. A multidisciplinary team will significantly reduce the risk associated with delivery of these women.
Introduction
Cardiac disease in pregnancy is an important cause of maternal morbidity and mortality and has featured increasingly and prominently in the Confidential Enquiries into Maternal and Child Health over the last 20 years. Cardiac disease is the leading indirect cause of death in these patients, with most adverse events and cardiovascular stress peaking in the peripartum period. Advances in reproductive medicine and a rise in the number of women with adult congenital heart disease (CHD) becoming pregnant have added to the burden of cardiac disease in pregnancy. Key questions that arise in the peripartum period are when, how, and where delivery should be undertaken and what risk that poses.
Central to the optimum peripartum management of women with cardiac disease is careful planning by the multidisciplinary team so that the woman and those caring for her are prepared for any complications that might arise. Planning for delivery should be commenced relatively early in the antenatal period, with a written record of the plan placed in the woman’s handheld notes in case preterm delivery occurs unexpectedly. Women with high-risk lesions should be delivered in a tertiary center with a multidisciplinary team of specialist midwives, obstetricians, anesthetists, obstetric physicians, and cardiologists available. In contrast, the European Society of Cardiology (ESC) recommends that women with mild unrepaired CHD and those who have undergone successful cardiac surgical repair with minimal residua can be managed in the same way as normal pregnant women.[1]
Significance of cardiac disease in the peripartum period
Not all women with cardiac disease are at an increased risk during the peripartum period. Some lesions are considered high risk, while others are medium or low risk, and a few confer no greater risk compared with a completely healthy pregnant woman. It is important to assess each pregnancy and make a risk assessment for that pregnancy when planning peripartum care.
Lesions that carry a high maternal and fetal risk include:
1. Pulmonary hypertension, including Eisenmenger syndrome
2. Severe aortic stenosis or other left ventricular outflow obstruction (even if asymptomatic)
3. Any valvar lesion where the New York Heart Association functional status is level III or IV
4. Maternal cyanosis
5. Any lesion resulting in a low ventricular ejection fraction (<40%)
6. Marfans syndrome with a dilated aortic root (>4.5 cm).[1]
Congenital cardiac disease that has been repaired is usually low risk if the woman is not cyanosed and has good ventricular function with no history of heart failure and/or intractable arrhythmia. The univentricular circulation (e.g. Fontan) confers a moderate risk to the mother but can usually be managed safely by vaginal delivery with regional anesthesia.[2]
Most other cardiac lesions are low risk and require little or no modification to standard care in the peripartum period. Clinically, patients with stenotic cardiac lesions tend to become more symptomatic as the pregnancy progresses and their Doppler echocardiographic gradients are expected to increase (often double) by the second trimester.
Obstetric issues
Timing of delivery
For most women, it is appropriate to await spontaneous onset of labor. Women with moderate to severe cardiac disease may require delivery at a tertiary center to ensure access to the full multidisciplinary team, if needed during labor. This will entail careful planning to ensure the woman is able to reach the tertiary center promptly when labor starts. Ideally, this will involve finding accommodation for the woman and her partner close to the tertiary center while awaiting labor. The provision of on-site or nearby “hotel facilities” may avoid the need for admission to a hospital bed simply to await events. Tertiary centers may provide a convenient place for the woman and her family to stay, from where she can easily attend the maternity unit for regular check-ups and access the delivery suite; induction may then be prevented and the likelihood of vaginal delivery enhanced. If this is not possible, then induction to ensure labor at the tertiary center may be considered but the risks of induction should be carefully weighed up in conjunction with the woman and her family.
If the woman’s condition worsens during pregnancy, early delivery for maternal benefit may be necessary. In such cases, the benefit to the woman needs to be balanced with the risk to the neonate from prematurity. Care should always be taken to consider the risk to the woman of remaining pregnant as distinct to the total risk of the pregnancy because delivery will be a time of peak risk even with early delivery. It should always be recognized that early delivery in the absence of a deterioration of maternal condition may not significantly decrease the total risk to the woman, and too early a delivery may risk a disabled baby that the father may be left to care for on his own. Steroids should be given if delivery is planned before 34 weeks of gestation, although in cases of severe impairment of cardiac function the associated fluid retention can precipitate cardiac failure and the use of prophylactic diuretics should be considered.
Induction of labor should be performed with care. Prostaglandin E2 can be used for induction, as can artificial rupture of the membranes followed by intravenous oxytocin. There is about a 1% risk of uterine hyperstimulation with prostaglandins, which may precipitate acute fetal hypoxia. This is usually treated with use of beta-sympathomimetic agents but these can cause tachycardia and arrhythmia. Hyperstimulation may necessitate urgent delivery with its attendant risks. Consideration should therefore be given to nonpharmacological methods of cervical ripening such as use of an intracervical Foley catheter. With oxytocin, special care needs to be taken with regard to the volume of intravenous fluid given during labor because oxytocin can cause water retention owing to its antidiuretic effects. Oxytocin should be given via a syringe driver in a small volume of saline, for example 10 IU in 50 ml, starting at 0.6 ml/h (2 mIU/minute).
Mode of delivery
ESC guidelines on the management of women with cardiovascular disease recommend vaginal delivery as the preferred mode of delivery.[1]
When considering whether there needs to be any recommendation to alter mode of delivery for women with cardiac disease, it is helpful to consider the rises in cardiac output above late pregnancy levels that occur during the three stages of labor. In early labor, there is a rise of around 15% compared with the late antenatal period, increasing to approximately 25% during contractions.[3] These changes may be partly mediated by pain and anxiety [4,5] and may be reduced by analgesia.[6]
During active pushing in the second stage, cardiac output rises to approximately 50% above prelabor levels.[3] This increase may be significantly reduced by regional analgesia.[6] Thus, it is important to consider the length of time pushing during the second stage (“the active second stage”) separately to the time spent in the second stage with regional analgesia without active pushing (“the passive second stage”) if recommendations are to be made as to an artificial time limit on cardiac grounds.
It is very important to recognize that the peak rise in cardiac output occurs in the third stage of labor, with increases of 60% compared with prelabor levels reported shortly after vaginal delivery by some authors despite regional analgesia.[6] This is thought to be caused by autotransfusion of blood from the uteroplacental bed after delivery of the baby. The process of autotransfusion occurs whatever the mode of delivery, and measurements of cardiac output following cesarean section are reported to show significant increases from predelivery levels at 15 and 30 min postdelivery of around 30% and 20%, respectively,[7] with 11% reported during cesarean section under regional analgesia.[3] It is crucial to safe management to appreciate the risk involved in the third stage regardless of mode of delivery.
Vaginal delivery
Labor should be conducted with the woman sitting upright or in the lateral decubitus position to avoid aortocaval compression. Delivery itself is best performed with the woman sitting upright and her feet supported on foot rests. If the woman needs to lie on her back it is important to use a wedge to minimize aortocaval compression, which decreases venous return from the lower limbs, and to minimize elevation of her legs, which may increase venous return—the aim is to maintain cardiovascular stability. The method of fetal monitoring during labor will depend on the risk of fetal compromise and the care plan should include a recommendation for either intermittent auscultation or continuous electronic fetal monitoring.
Every woman should have an individualized care plan for delivery; as part of this plan, consideration should be given as to whether there is any need to limit the length of the active second stage by performing an instrumental vaginal delivery. Active pushing may be poorly tolerated by women with limited exercise tolerance and these women may require an assisted delivery. In women with severe cardiac disease who have been advised to avoid resistance exercise, active pushing should be limited or avoided. In such cases, effective regional analgesia is extremely helpful in allowing the fetal head to descend to the perineum without active pushing prior to instrumental vaginal delivery.
The woman’s care plan for labor should indicate whether administration of oxytocin for stimulation of slow progress in labor is acceptable should the need arise. Oxytocin should be given via a syringe driver in a small volume of saline, for example 10 IU in 50 ml starting at 0.6 ml/h (2 mIU/min) to avoid vasodilatation. Oxytocin causes fluid retention and care should be taken to avoid fluid overload.
Antibiotic prophylaxis against infective endocarditis is not routinely required for vaginal delivery.[1]
Cesarean delivery
The ESC guideline recommends that cesarean delivery is generally reserved for obstetric indications. Cesarean section is associated with increased risks of hemorrhage, postpartum infection, puerperal fluid shifts, and metabolic demands.[8] In a large prospective study in Canada of 566 women, there was no association between the type of delivery and the rate of peripartum cardiac events (3% vs 4% for vaginal vs cesarean delivery; p=0.46).[7] However, studies in women with pulmonary vascular disease or a previous history of myocardial ischemia suggest a doubling of maternal mortality in association with cesarean section.[9] In a systematic 18 year overview from 1978 to 1996, Weiss et al. found a 2.5-fold (95% confidence interval 1.1, 5.2) increase in maternal mortality in women with pulmonary vascular disease undergoing cesarean section.[10]
Any decision to avoid vaginal delivery on cardiac grounds should be individualized to the woman depending on her cardiac status at the time of delivery, but there are some conditions in which cesarean section would generally be considered [1]:
women with Marfan syndrome and aortic root diameter of >45 mm
women with acute or chronic aortic dissection
women with severe heart failure
women with mechanical heart valve prostheses who are usually on oral anticoagulation; to prevent a prolonged switch to low-molecular-weight heparin during induction if the cervix is unfavorable.
Third-stage management
During the third stage of labor, there are two counterbalancing effects on cardiovascular physiology. As the placenta delivers and the uterus contracts (either spontaneously or in response to uterotonics), there is an increase in intravascular volume of approximately 500 ml. At around the same time, there is hemorrhage associated with delivery, which has an average volume of 500 ml. The hemodynamic effects may be reduced during delivery of the placenta by sitting the woman up and avoiding raising the legs. In women with severe disease, judicious use of furosemide may be required to prevent pulmonary edema.
In healthy women, oxytocin causes a small reduction in arterial blood pressure 30 s after a 10 IU intravenous bolus, followed by an increase in cardiac output (60 s after 5–10 IU and 120 s after 5 IU).[11] The initial change is due to peripheral vasodilatation with the increase in cardiac output secondary to autotransfusion, as described above. Oxytocin also has a direct effect on the heart, causing decreased cardiac contractility and heart rate (HR).[12] These effects may be catastrophic in women with cardiac disease, but are minimized when oxytocin is given by slow intravenous infusion. In contrast, the alternative oxytocic commonly used in normal women, ergometrine, causes peripheral vascular constriction and coronary vasospasm and should therefore be avoided in women with hypertension or myocardial ischemia. Carboprost (prostaglandin F2a) and misoprostol are both potent synthetic prostaglandins that are effective in causing tonic uterine contractions. Carboprost given intravascularly can cause bronchospasm, and both carboprost and misoprostol are contraindicated in myocardial ischemia. Misoprostol is not currently licensed for use in the third stage of labor and there are some concerns about its adverse effects of shivering (frequent) and hyperpyrexia (rare but serious) in women with cardiac disease; it should therefore only be used where it is considered that the benefit outweighs the risks. Further studies to clarify its risk/benefit ratio are justified. Some obstetricians have used mechanical maneuvers to reduce postpartum hemorrhage, such as bimanual compression (in the short term), uterine compression sutures, and intrauterine balloons, rather than using pharmacological oxytocics; this approach also warrants further study.
Postpartum hemorrhage is not uncommon in women with cardiac disease, both because the use of uterotonics is often avoided for the reasons described above and for hematological reasons such as the use of heparin thromboprophylaxis and/or platelet dysfunction in the presence of mechanical heart valves. Such women often tolerate hypovolemia poorly and it is of the utmost importance that attention be given to hemostasis both at cesarean section and for any perineal trauma. Postpartum hemorrhage in the face of significant cardiac compromise may have catastrophic consequences.
Anesthesia in the peripartum period
It is generally accepted that most women can be delivered safely with regional anesthesia. Much of the supporting evidence is from the American Society of Anesthesiologists. NYHA Class I and II women have a very low risk of complications and are ideally suited to vaginal delivery with regional anesthesia/analgesia. Women with significant cardiac disease fall outside this spectrum, and general anesthesia, though traditionally viewed as higher risk, may be more suitable for selected patients. The risk of failed intubation (~1 in 250) is always uppermost in the anesthetist’s mind, but should not preclude general anesthesia if this is deemed a safer option for delivery. Many anesthetic trainees have a limited exposure to obstetric general anesthesia, and every opportunity should be exploited to ensure that the technique is mastered, including medical simulation.[13] Very few absolute rules apply and often the anesthetic choice is a culmination of opinion, ability, clinical condition, maternal preference, and perceived risk.
There are few absolute indications/contraindications for either regional or general anesthesia. Before any choice is made, it should be clearly established whether the cardiac lesion results in normal or abnormal circulation, and the method should be selected with this in mind.
Traditionally, general anesthesia has been the preferred method of anesthesia for cesarean section in women with heart disease, although more recent opinion is that regional anesthesia is suitable in many cases. However, the choice for women with severe disease remains controversial.[14,15] In a UK series of over 250 cardiac cases reported to a voluntary registry, 39% of cesarean sections were performed under general anesthesia, over three times the average rate for high-risk women without heart disease. Whatever method is chosen for an operative delivery, a locally adapted version of the World Health Organization Surgical Safety Checklist should be completed and a clear plan agreed of the approach to anesthesia, operative delivery, and postoperative care.[16]
Regional anesthesia/analgesia
The term “regional anesthesia” describes dense neural blockade such as that required for a pain-free operative delivery. As well as producing sensory and motor blockade, epidural and spinal anesthesia cause autonomic paralysis. This can lead to profound vasodilatation and hypotension in normal individuals, let alone those affected by cardiac disease. “Regional analgesia,” on the other hand, describes pain relief rather than complete neural blockade. Effective relief of labor pain can be achieved with minimal hemodynamic effect [17] by using weaker drug combinations than those used for anesthesia. While analgesia and anesthesia merge in a continuous spectrum, the two are not synonymous.
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