The Obstetrician & Gynaecologist 2007;9:1:15-20
doi: 10.1576/toag.9.1.015.27291
Copyright © 2007 by the Royal College of Obstetricians and Gynaecologists.
Cardiac disease in pregnancy. Part 1: congenital heart disease
Emily Gelson, BS MB BCh, Clinical Fellow in Pregnancy and Heart Disease1,
Mark Johnson, PhD MRCP MRCOG, Reader in Obstetrics and Obstetric Medicine2,
Michael Gatzoulis, MD PhD MRCP, Professor of Cardiology, Congenital Heart Disease3 and
Anselm Uebing, MD, Fellow in Adult Congenital Heart Disease4
1. Chelsea and Westminster Hospital, 369 Fulham Road, London SW10 9NH, UK Email: e.gelson{at}imperial.ac.uk (corresponding author)
2. Chelsea and Westminster Hospital, London, UK
3. Adult Congenital Heart Disease Unit, Royal Brompton and Harefield NHS Trust and; National Heart and Lung Institute, Imperial College, London SW3 6NP, UK
4. Adult Congenital Heart Disease Unit, Royal Brompton and Harefield NHS Trust and; National Heart and Lung Institute, Imperial College, London, UK
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Abstract
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Key content:- Heart disease is now the most common indirect cause of maternal death in the United Kingdom.
- Neonatal morbidity and mortality from fetal growth restriction and prematurity are markedly increased in women with heart disease.
- Women with congenital heart disease should ideally have a planned pregnancy managed by a multidisciplinary team which includes obstetricians, cardiologists, anaesthetists, neonatologists and midwives.
Learning objectives:
- To understand the changes to cardiovascular physiology during pregnancy.
- To recognise the risk factors for poor pregnancy outcome in cardiac disease.
- To understand the general management principles for women with cardiac disease in pregnancy.
Ethical issues:
- Should we be recommending termination of pregnancy in women with high risk cardiac lesions?
- How do we manage women who become pregnant against medical advice?
- What is the role of surrogacy in women with high risk cardiac lesions?
Please cite this article as: Gelson E, Johnson M, Gatzoulis M, Uebing A. Cardiac disease in pregnancy. Part 1: congenital heart disease. The Obstetrician & Gynaecologist 2007;9:15–20.
Keywords acquired heart disease / congenital heart disease / neonatal outcome / pregnancy / prepregnancy counselling / risk assessment
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Introduction
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The incidence of heart disease during pregnancy in the UK has remained constant at 0.9% over several decades.1 However, the severity and the risk it poses during pregnancy appears to be increasing. Heart disease has re-emerged as one of the leading causes of maternal mortality (2.2 per 100 000) and is now the most common indirect cause of maternal death in the UK.2 Pregnancy not only poses a risk of maternal mortality but also of serious morbidity such as heart failure, stroke and cardiac arrhythmia. The fetus is not spared: neonatal morbidity and mortality from fetal growth retardation and prematurity are markedly increased.3 In Part 1 of this article we review congenital heart disease in pregnancy and in Part 2 we look at acquired heart disease.
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Congenital heart disease
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In the developed world, congenital heart disease is now more common in pregnant women than acquired heart disease. Among pregnant women with heart disease, the proportion with heart disease of congenital origin has risen in two decades from 5% to almost 80%.4 This reflects advances in cardiac surgery and medication, meaning that 85% of the 7 in 1 000 infants with congenital heart disease now survive to adulthood and reproductive maturity.5
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Physiological changes in normal pregnancy
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During normal pregnancy there are dramatic alterations in cardiovascular physiology initiated by a fall in systemic vascular resistance to 30–70% of its preconception value by 8 weeks of gestation.6 The mechanism responsible for triggering such widespread vasodilatation is unclear, but increased circulating levels of estrogens, vasodilatory peptides or factors such as nitric oxide and calcitonin-gene related peptide (CGRP) have all been suggested as possible causes.The fall in systemic vascular resistance results in fluid retention and an increased blood volume. Since there is a relatively greater expansion in plasma volume this results in a fall in haematocrit and plasma osmolality. The increase in cardiac output is secondary to a greater stroke volume and higher heart rate. It rises to a peak between 20–24 weeks of gestation and remains stable until term. Arterial blood pressure falls until mid pregnancy, gradually returning to prepregnancy levels late in the second trimester. Prolonged volume overload results in progressive physiological left ventricular hypertrophy.
Labour, particularly the second stage, is associated with a further increase in cardiac output. Pain induces a sympathetic response, causing an increase in heart rate. Stroke volume is augmented by auto-transfusion during contractions. Following delivery the return of uterine blood into the systemic circulation results in a further increase in cardiac output. Stroke volume, heart rate and cardiac output remain high for 24 hours post delivery, with rapid intravascular volume shifts in the first 2 weeks postpartum. Thus, the later stages of labour and early postpartum period are periods of high risk of pulmonary oedema.7
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Management principles
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Women with congenital heart disease should ideally have a planned pregnancy managed by a multidisciplinary team which includes obstetricians, cardiologists, anaesthetists, neonatologists and midwives. This requires close collaboration between tertiary cardiac and high-risk obstetric services. Effective management involves prepregnancy counselling and risk assessment, close fetal and maternal monitoring during pregnancy, a detailed management plan for labour and delivery and close surveillance in the immediate postpartum period.
Prepregnancy counselling
Prepregnancy counselling enables the impact of pregnancy on pre-existing heart disease to be explained to the woman and her family to allow them to make informed choices. The risks to the mother and fetus should be discussed and the likelihood of congenital heart disease in the fetus outlined (Box 1). Any medical, interventional or surgical treatments that can improve pregnancy outcome should be considered.
Labour and delivery
The appropriate timing for delivery is crucial to balance maternal and neonatal morbidity and mortality. A clear plan of management for labour and delivery should be established in advance, clearly documented and widely disseminated. In general, vaginal delivery with low dose epidural anaesthesia is the mode of choice (Box 2 shows cardiac indications for caesarean section). Labour requires careful monitoring of both mother and fetus. Preload and blood pressure should be monitored carefully and blood loss minimised. Women should be nursed in the left lateral position. Forceps or ventouse delivery can be used to shorten maternal expulsive effort in the second stage. Antibiotic prophylaxis should be given during labour and delivery for all women except those with repaired patent ductus arteriosus (PDA), isolated ostium secundum atrial septal defects and mitral valve prolapse without regurgitation.
In the management of the third stage, bolus doses of oxytocin should be avoided as they can cause severe hypotension. Low dose oxytocin infusions are safer. Ergometrine should also be avoided in most cases as it can cause acute hypertension. Uterine compression sutures can be helpful in the management of uterine atony at caesarean section. The safety of misoprostol is yet to be determined.
Careful haemodynamic monitoring postpartum is typically required for 24–72 hours, but this should be extended to 10–14 days in women with pulmonary hypertension. Multidisciplinary follow-up should take place 6 weeks after delivery.
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Specific lesions and maternal and fetal risk
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Risk to the mother from congenital heart disease appears to be determined by the ability of her cardiovascular system to adapt to pregnancy. Different congenital cardiac lesions carry specific mortality risks,7 dependent on current haemodynamic status, previous operations and anatomical features.8 Pregnancy also poses the risk of serious maternal morbidity. In 2001, a large prospective study of pregnancy outcomes in women with congenital heart disease reported a 13–23.5% rate of primary cardiac events.3 Pulmonary oedema and/or cardiac arrhythmia account for the majority of events, with thromboembolism, angina, hypoxaemia and infective endocarditis also reported. Predictors of primary maternal cardiac events are:9- prior cardiac event
- prior arrhythmia
- New York Heart Association (NYHA) functional class >II
- left heart obstruction
- myocardial dysfunction.
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Low risk lesions
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Small left-to-right shunts
In pregnancy, increased cardiac output and blood volume are counterbalanced by a decrease in peripheral vascular resistance. Left-to-right shunting in women with atrial septal defects (ASDs), ventricular septal defects and PDA is, therefore, reduced. In the absence of pulmonary hypertension, pregnancy, labour and delivery are well tolerated.10 Women with ASDs are at risk of atrial arrhythmias and paradoxical emboli. As such, there is a low threshold for heparin prophylaxis. Labour needs to be managed carefully as acute blood loss or vasodilatation (from regional anaesthesia) can affect the degree and direction of intracardiac shunting acutely, reducing left ventricular output.
Coarctation of the aorta
Coarctation of the aorta (Figures 1 and 2) occurs in 6–8% of patients with congenital heart disease. The majority of cases are diagnosed in infancy or childhood and are either surgically corrected or treated by balloon dilatation or stent implantation. Women with repaired coarctation of the aorta are expected to reach childbearing age. In contrast, native coarctation is encountered much less frequently. Pregnancy is usually well tolerated in women with adequately repaired coarctation.11 It is essential to assess cardiac status before conception, excluding and appropriately managing complications such as re-coarctation, aneurysm at the site of repair, an associated bicuspid aortic valve or systemic hypertension. In both corrected and native coarctation, pregnancy poses the risk of aortic dissection and rupture and resistant hypertension. Poorly controlled hypertension can lead to adverse neonatal outcomes (such as growth restriction, placental abruption and premature delivery) and maternal outcomes (including pre-eclampsia, hypertensive crisis and rupture of an intracranial aneurysm). As such, it needs to be tightly controlled with beta-blockers as the first line agent. There is a small risk of intrauterine growth restriction with beta-blockers and fetal growth should be monitored regularly and assessed by ultrasound.
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Figure 1
Magnetic resonance imaging of severe aortic coarctation before (left) and after (right) primary stent implantation in an adult patient. Note the aneurysmal dilatation in the ascending aorta. (With kind permission from Dr SV Babu-Narayan and Dr R Mohiaddin, CMR Unit, Royal Brompton and Harefield NHS Trust, London, UK.
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Figure 2
Magnetic resonance imaging of woman with mild residual coarctation and aneurysm at the site of previous coarctation repair. The maximum diameter of the aneurysm was 33 mm. (With kind permission from Dr PJ Kilner and Dr R Mohiaddin, CMR Unit, Royal Brompton and Harefield NHS Trust, London UK.
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Tetralogy of Fallot
Tetralogy of Fallot (ToF) is the most common form of cyanotic congenital heart disease. It is characterised by a non-restrictive ventricular septal defect, aortic override, pulmonary stenosis and right ventricular hypertrophy. In developed countries, ToF is usually corrected surgically in infancy, well before pregnancy is contemplated, and it is generally accepted that pregnancy in women with repaired ToF is well tolerated in this context.12 However, complications such as arrhythmias and right ventricular failure do occur, particularly in the presence of residual shunts, right ventricular outflow obstruction and pulmonary hypertension. Careful assessment, including echocardiography, is advisable before pregnancy. Many women with ToF will have significant pulmonary regurgitation and, therefore, can become symptomatic during pregnancy, occasionally needing diuretic treatment or admission for bed rest. Regular cardiac review throughout pregnancy for all women with repaired or unrepaired ToF is advised.
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Moderate risk lesions
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Transposition of the great arteries
Complete transposition of the great arteries (TGA) (Figure 3) can be repaired using Mustard rerouting, in which the tricuspid valve and the right ventricle support the systemic circulation. Although survival rates for this procedure are favourable, a number of potential long term complications exist. These include systemic right ventricle failure, tricuspid regurgitation, sinus node dysfunction, arrhythmias and baffle obstruction (venous pathway obstruction). Pregnancy is well tolerated following an uncomplicated repair; right ventricular dysfunction and/or atrial arrhythmia, may however, still occur.13 In women with long term complications, pregnancy is poorly tolerated with an increased risk of cardiac complications.14 Many women with corrected TGA are on ACE inhibitors, which should ideally be stopped before conception as they are associated with fetal nephrotoxicity and congenital malformations.15 Since 1975, complete repair has been carried out using the Jatene procedure, in which the left ventricle remains the systemic ventricle. The outcome of pregnancy in these women remains to be seen but recent case reports are promising.16
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Figure 3
Cardiac magnetic resonance imaging of a patient with transposition of the great arteries and atrial switch operation. A baffle (small arrows) is created in the atria to redirect blood from the left atrium (LA) into the systemic right ventricle (RV). Systemic venous blood returns to the subpulmonary left ventricle (LV). The systemic right ventricle (RV) is markedly enlarged, squashing the left ventricle. (With kind permission from Dr Philip Kilner, CMR Unit, Royal Brompton and Harefield NHS Trust, London UK.
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Cyanotic heart disease without pulmonary hypertension
Cyanotic heart disease without pulmonary hypertension is caused by uncorrected transposition of the great arteries, truncus arteriosus, uncorrected ToF with pulmonary stenosis/atresia, univentricular heart, tricuspid atresia and Ebstein's anomaly with ASD. During pregnancy the fall in systemic vascular resistance and rise in cardiac output exacerbates any right-to-left shunting, worsening pre-existing cyanosis and hypoxia. Maternal complications depend mainly on ventricular function and include haemorrhage, paradoxical embolism and heart failure. The effects on the fetus are marked, with a high incidence of spontaneous miscarriage and a 30–50% risk of premature delivery and low birthweight. The degree of maternal hypoxaemia is the most important predictor of neonatal outcome.17 Admission for bed rest and oxygen therapy is an effective method of maintaining maternal oxygen saturation and fetal oxygenation and growth.
Fontan procedure
Fontan-type procedures have become recognised as the definitive palliative procedure available for complex cyanotic heart defects characterised by a single functional ventricle. Atrial separation divides the systemic and pulmonary circulations and with the construction of atriopulmonary connections blood enters the pulmonary circulation without pulsatile ventricular flow. Increasing numbers of women with a Fontan circulation are reaching childbearing age. The main concern regarding pregnancy is the ability to augment, maintain and adjust cardiac output and heart rate. There is also a tendency towards atrial arrhythmias, which are poorly tolerated. However, recent studies suggest that the maternal risks of pregnancy are low in NYHA class I–II women, provided ventricular function is good.18
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High risk lesions
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Marfan syndrome
Marfan syndrome is an inherited disorder of connective tissue. The risk of thoracic aortic aneurysm leading to aortic dissection, rupture or both is increased in pregnancy. This is the result of haemodynamic stress and is dependent on aortic root diameter. With an aortic root smaller than 4 cm, the overall maternal mortality during pregnancy is 1%. This increases to as much as 25% as the aortic root diameter expands beyond 4 cm.19 In this situation, pregnancy should be postponed until aortic arch replacement.20 In the event of an unplanned pregnancy the option of termination should be discussed. Aortic root diameter should be monitored throughout pregnancy with serial echocardiograms and if aortic root dilatation occurs, prophylactic beta blockade is advised and hypertension should be treated aggressively.
Pulmonary vascular disease
Pregnancy in the presence of pulmonary hypertension of any cause remains high risk. Fixed pulmonary vascular resistance prevents any increase in pulmonary blood flow matching the increased cardiac output. Pregnancy is poorly tolerated, with a risk of worsening cyanosis and hypoxia, arrhythmias, heart failure and death. The majority of complications occur at term or during the first postpartum week. Maternal mortality depends on the underlying cause, with a 36% maternal mortality in Eisenmenger syndrome, 30% in primary pulmonary hypertension and 56% in secondary pulmonary hypertension.21 Women should be advised of these risks when contemplating pregnancy. In the event of an unplanned pregnancy a termination should be offered. Those who elect to continue require close cardiovascular monitoring and bed rest from the third trimester with monitoring for up to 14 days postpartum. Fetal morbidity and mortality are considerable, with premature delivery and restricted fetal growth occurring in 50% of cases and only 15–25% of pregnancies reaching term. Anticoagulation, oxygen therapy and pulmonary vasodilators (nitric oxide or prostacyclin) may improve outcome.22
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Neonatal outcome
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The rate of neonatal complications is significantly increased in women with heart disease. They include preterm birth, being small for gestational age, respiratory distress syndrome, intraventricular haemorrhage and death. Maternal predictors of adverse neonatal outcome are obstetric risk factors, multiple gestation, smoking and anticoagulation.23 The children of a mother with congenital heart disease are also at increased risk of inheriting a congenital heart disease. The overall risk of inheriting polygenic cardiac disease is quoted at 3–5%, compared with a 1% risk in the general population.24 The risk is, in fact, dependent on the parent's condition, being 3% in common conditions such as ToF and as high as 10% with ASD, coarctation of the aorta and aortic stenosis.25 Marfan syndrome is an autosomal dominant condition and, therefore, has a 50% recurrence rate in offspring.
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Conclusion
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Cardiac disease in pregnancy is a leading cause of maternal and neonatal morbidity and mortality. Congenital heart disease now accounts for the majority of disease. Effective management is based upon prepregnancy counselling and risk assessment, close fetal and maternal monitoring during pregnancy, a detailed management plan for labour and delivery and close surveillance in the immediate postpartum period.
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References
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Abstract
Introduction
