Introduction

The management of cardiac disease in pregnancy is important, as there are significant risks of maternal and fetal morbidity and mortality from cardiac diseases. In the 2006–08 triennium, cardiac disease was the leading cause of death with 53 deaths (2.31 per 100,000 maternities).¹ These were the highest number and rate of cardiac deaths in pregnancy since the 1985–87 period, with increases recorded in the last three triennia. Fifty-one per cent of these deaths had substandard care, and most had acquired heart disease such as myocardial infarction and ischaemic heart disease, aortic dissection and cardiomyopathy.

There are significant cardiovascular changes in pregnancy which can strain the heart and mimic symptoms of cardiac disease. There is a 40% increase in cardiac output, which is due to a 25% increase in both stroke volume and heart rate. This is accompanied by a 1250–1500 mL increase in blood volume due to a 40–50% increase in plasma volume and 20% increase in red cell mass. There is a reduction in total peripheral resistance but no change in the cardiac venous pressure of the superior vena cava circulation. There is a fall in blood pressure up to 20 weeks gestation and then it gradually returns to pre-pregnancy levels by term. Cardiac output increases to 8 L/minute in the first stage of labour and 9 L/minute in the second stage. It increases by 60–80% immediately after delivery but returns to pre-labour levels within 1 hour of delivery. By 3 months postpartum cardiac output, stroke volume and peripheral vascular resistance have returned to pre-pregnancy levels. The hyperdynamic circulation of pregnancy can lead to innocent cardiac murmurs in pregnancy.

Principles of management

The management of pregnant women with cardiac diseases must be by a multidisciplinary team comprising an obstetrician, a cardiologist with experience of cardiac disorders in pregnancy, an obstetric anaesthetist, a specialist midwife and a haematologist (for those at high risk of thromboembolism, such as women with mechanical heart valves). Those with congenital heart disease should have fetal echocardiography by a fetal cardiologist at 19–22 weeks because of the increased risk of congenital heart disease in the fetus.

All pregnant women recently arrived in the UK should have a cardiovascular assessment in primary/secondary care. Those with already diagnosed disease should have pre-conception assessment and counselling in order to assess disease status, discuss pregnancy risks and management and optimize disease state and medication (and/or contraception) prior to attempting to conceive. The patients are then seen in the first trimester (along with those with new presentations), when a plan of care is made. They should be seen regularly thereafter and a decision taken at about 32–34 weeks regarding timing, place and mode of delivery, and care during delivery and thereafter.² Although cardiac disease may deteriorate in the late second and third trimester, the greatest risk is at delivery and in the postpartum period when raised blood pressure and sudden changes in cardiac output and blood volume secondary to uterine contractions, vasodilatation and haemorrhage place additional strain on the heart. The aim is to minimize these changes.

A thorough history and clinical examination should be undertaken, and usually an ECG, echocardiogram and pulse oximetry would be required. Holter (24-hour) ECG or longer is useful in arrhythmias and palpitations. Other investigations that might become necessary include exercise testing, cardiac MRI and chest x-ray.

The risk associated with pregnancy is determined by the type of cardiac disease, the presence of cyanosis and pulmonary hypertension, and is often assessed using risk stratification tools such as the New York Heart Association (NYHA) classification of heart disease (Table 8.1), the World Health Organization (WHO) classification of maternal cardiovascular risk (Table 8.2) and the Cardiac Disease in Pregnancy (CARPREG) risk score. The last of these uses the presence of four groups of risk factors to predict maternal risk. The risk factors are (1) prior cardiac event such as heart failure, stroke, arrhythmia or transient ischaemic attack; (2) baseline NYHA functional class > II or cyanosis; (3) left heart obstruction (mitral valve area < 2 cm², aortic valve area < 1.5 cm², peak LV outflow tract gradient > 30 mmHg by echocardiography); and (4) reduced systemic ventricular systolic function (ejection fraction < 40%). For each risk factor present, a point is assigned, with a 5% maternal risk if 0 point, 27% if 1 point and 75% if > 1.

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