Pregnant women may have a pre-existing cardiomyopathy or may develop cardiomyopathy of pregnancy (peripartum cardiomyopathy, PPCM).
The causes of pre-existing cardiomyopathy are diverse and include infection, systemic disease such as sarcoidosis, infiltrative disease such as amyloid, toxins such as alcohol and cocaine, ischaemic heart disease, obesity-related and congenital cardiomyopathies. Of this group, the most commonly encountered in the antenatal clinic is hypertrophic cardiomyopathy (HCM), with a prevalence of about 1 in 500, though restrictive and dilated cardiomyopathies may also be seen.
The aetiology of PPCM is unknown, but viral or autoimmune myocarditis, or an exaggerated response to the haemodynamic stresses of pregnancy, have been suggested. Predisposing factors seem to be multiple pregnancy, smoking, family history, prolonged use of β-agonists, diabetes and hypertension. The classic criteria for diagnosis of PPCM are:
1. Development of cardiac failure in the last month of pregnancy or within 5 months of delivery.
2. Absence of other aetiology for cardiac failure.
3. Absence of cardiac disease prior to the last month of pregnancy.
4. Echocardiography criteria have subsequently been added: ejection fraction < 45% and/ or fractional shortening < 30%, and end-diastolic dimension > 2.7 cm/m2 body surface area.
It has been suggested that the definition should be extended to include cardiac failure developing within the third trimester of pregnancy for which no other cause can be found. The incidence of PPCM is estimated to be 1 in 3000 pregnancies.
Functionally, patients with HCM have thickened myocardium and may have outflow obstruction, while those with PPCM have a dilated cardiomyopathy.
Problems and special considerations
Patients with HCM have a hypertrophied left ventricle and interventricular septum which may cause outflow obstruction and myocardial ischemia due to a mismatch between oxygen supply and demand. Mitral regurgitation is often present. Any factors that increase myocardial contractility (β-agonists, circulating catecholamines) or decrease preload or afterload (vasodilatation, hypovolaemia) will cause an increase in left ventricular outflow obstruction. Tachycardias reduce the time for diastolic filling, and atrial arrhythmias are particularly poorly tolerated.
The obstructive component of HCM varies considerably. Women with minimal obstruction usually tolerate pregnancy well, although the more severe the degree of left ventricular hypertrophy the greater the risk of myocardial ischaemia, particularly in response to the stress of pregnancy and delivery.
Patients with dilated cardiomyopathy have reduced myocardial contractility. The left ventricle is hypokinetic, ejection fraction is reduced and there is usually mitral and/or tricuspid regurgitation. Pressures in the right side of the heart are raised, and cardiac or pulmonary artery catheterisation usually confirms pulmonary hypertension. Any factors that depress myocardial contractility or increase afterload will further compromise cardiovascular stability.
Women with PPCM usually present with the classic signs of left ventricular or congestive cardiac failure. There is a high associated risk of embolic phenomena.
Management options
Hypertrophic cardiomyopathy
Women with HCM have usually been diagnosed before pregnancy, and baseline cardiological investigations should be available. If β-blocking drugs are being used they should be continued during pregnancy.
Serial cardiological investigations (electrocardiography (ECG), echocardiography) should be performed during pregnancy. Tachycardias should be treated with suitable β- blockers, and esmolol has been recommended for use in the acute situation. Cardioversion may be required to terminate supraventricular tachycardia; amiodarone is recommended for ventricular tachycardias. Nitrates should not be used to treat angina because the consequent vasodilatation and afterload reduction further aggravates left ventricular outflow obstruction.
There is no indication to deliver women by caesarean section unless there are obstetric reasons to do so or unless the maternal condition deteriorates. Continuous ECG and arterial blood pressure monitoring should be used throughout labour and delivery and continued into the early postnatal period.
Traditionally, regional analgesia has been considered contraindicated because of the risk of acute reduction in afterload. However, provision of high-quality analgesia is beneficial, particularly for preventing pain-induced tachycardia. Intrathecal opioid analgesia is not accompanied by sympathetic blockade but is of limited efficacy in advanced labour. Epidural or combined spinal-epidural analgesia, using low-dose (< 0.1% bupivacaine) epidural local anaesthetic with fentanyl, offers good analgesia with minimum haemodynamic disturbance.
Maintenance of adequate hydration - intravenously if necessary - is important. Phenylephrine is preferable to ephedrine for treatment of hypotension because the a effects of phenylephrine on myocardial contractility and heart rate are less than those of the mixed a and β effects of ephedrine.
Dilated cardiomyopathy/PPCM
The majority of cases of PPCM present in the peripartum or immediate postpartum period. Treatment includes use of positive inotropes such as digoxin (and parenteral inotropes such as dopamine and dobutamine in the acute situation), oxygen and diuretics, vasodilators to reduce afterload (but not angiotensin-converting enzyme inhibitors before delivery), bed rest and anticoagulants (because of the risk of thromboembolic disease). Intra-aortic balloon pumps, left ventricular assist devices and heart or heart-lung transplantation may be required in severe cases that fail to respond to maximal medical therapy.
If PPCM presents antenatally, delivery is indicated as soon as the woman’s condition has been optimised. Caesarean section may be necessary unless conditions are favourable for induction of labour.
Regional analgesia and anaesthesia are thought to be beneficial for the patient with dilated cardiomyopathy, since the cardiodepressant effects of most general anaesthetic drugs are avoided, and afterload is beneficially reduced. Hypotension should be treated with drugs with predominantly β activity, which stimulate myocardial contractility (ephedrine) rather than pure a-agonists (phenylephrine), which increase systemic vascular resistance. The immediate postpartum period is a particularly risky time owing to autotransfusion and the risk of fluid overload.
PPCM is thought to have a mortality rate approaching 10% at 2 years and has a high recurrence rate, and some authorities consider further pregnancies to be contraindicated following PPCM. Others suggest that another pregnancy can be considered if there is no residual cardiomegaly by 6 months postpartum. Case series suggest that if left ventricular function is still impaired 1 year after delivery, there is a ~20% risk of death in the next pregnancy.
Key points
• Hypertrophic cardiomyopathy is usually inherited, and presents with variable left ventricular outflow obstruction.
• Treatment is directed at reduction of myocardial contractility and increasing preload and afterload.
• Tachyarrhythmias and myocardial ischaemia are particular hazards.
• Peripartum cardiomyopathy usually presents in the peripartum or early postpartum period.
• Treatment is symptomatic and is directed at maintaining myocardial contractility and reducing afterload.
Further reading
Blauwet LA, Cooper LT. Diagnosis and management of peripartum cardiomyopathy. Heart 2011; 97: 1970-81.
Herrey AS. Pregnancy in inherited and acquired cardiomyopathies. Best Pract Res Clin Obstet Gynaecol 2014; 28: 563-77.
Hilfiker-Kleiner D, Haghikia A, Nonhoff J, et al. Peripartum cardiomyopathy: current management and future perspectives. Eur Heart J 2015; 36: 1090-7.
Lewey J, Haythe J. Cardiomyopathy in pregnancy. Semin Perinatol 2014; 38: 309-17.