Primary pulmonary hypertension is associated with an extremely high maternal mortality (40-60%) and is one of the few remaining maternal conditions in which pregnancy is considered absolutely contraindicated.
Secondary pulmonary hypertension may occur as a result of chronic pulmonary disease (e.g. connective tissue disease) or congenital heart disease such as severe aortic or mitral stenosis, or, more usually, chronic left-to-right shunt, and tends to have a lower mortality rate. These conditions are also associated with high maternal mortality, particularly left-to- right shunt leading to Eisenmenger’s syndrome (reversal of the shunt when pulmonary pressures exceed systemic pressures).
Although women are advised against pregnancy and termination is offered, many do not heed this advice.
Problems and special considerations
Pulmonary artery pressures may be close to systemic arterial pressures and are associated with a high pulmonary vascular resistance. There is right ventricular hypertrophy and a relatively fixed low cardiac output. Increases in pulmonary vascular resistance, decreases in systemic vascular resistance or falls in cardiac output can all have catastrophic and potentially fatal consequences. In Eisenmenger’s syndrome, peripheral vasodilatation increases shunt across the heart and thus worsens hypoxaemia and leads to a low cardiac output state.
The increased cardiac output that occurs during pregnancy is poorly tolerated, since it causes further increase in pulmonary artery and right ventricular pressures, and volume overload. Right ventricular dilatation and tricuspid regurgitation may occur, and left ventricular function and cardiac output may become increasingly impaired. The major haemodynamic changes occurring during parturition and the puerperium can prove fatal. Major haemorrhage causing hypovolaemia, or autotransfusion with the third stage of labour causing volume overload, are both poorly tolerated.
Preterm delivery and fetal growth restriction are both likely and perinatal mortality is increased, particularly in the presence of cyanosis.
Management options
Close antenatal monitoring is essential, and women with pulmonary hypertension are frequently admitted for inpatient care in the third trimester of pregnancy or even earlier - most women resting more in hospital than is possible at home. Beta-blockers, diuretics and pulmonary vasodilators may be used for symptom relief. Prophylactic anticoagulation is controversial, but prophylactic heparin is often given in addition to simple antithromboembolism measures such as graduated compression stockings. Care must be taken to avoid prolonged immobility in hospital. The risks of aortocaval compression if women adopt supine or semi-supine positions are not confined to labour, and the lateral position should be adopted for any antenatal examinations of mother or fetus.
Pulmonary hypertension itself is not considered an indication for caesarean section, though it may be required should maternal condition deteriorate or if there is fetal compromise. Recent data from a large European registry of pregnancies and cardiac disease reported that nearly two-thirds of deliveries in women with pulmonary hypertension were by caesarean section, although a third of these were unplanned. The advantages of choosing to deliver by caesarean section include avoiding a prolonged second stage and the adverse effects of bearing down, and also avoiding uncontrolled vaginal haemorrhage. Continuous oxygen therapy may be beneficial for both mother and fetus. The mother may describe ‘funny spells’, and these should be taken seriously as potential indicators of episodes of severe pulmonary hypertension. Induction of labour is an option if the cervix is favourable, but is associated with a higher rate of operative delivery than spontaneous labour.
For delivery, maternal monitoring should include electrocardiography and invasive right atrial and arterial blood pressure measurement. Use of a pulmonary artery catheter is more controversial and has been associated with an increased risk of thrombosis; other methods of cardiac output monitoring have been used intraoperatively. Scrupulous care must be taken to avoid accidental injection of air, because of the risk of systemic embolism in women with shunts. Episodes of hypotension should be treated promptly with fluids or vasopressors to stop an increase in right-to-left flow.
Oxygen is a readily available and easily administered pulmonary vasodilator and should be given continuously throughout labour and delivery. Hypoxia, hypercarbia and acidosis all tend to increase pulmonary artery pressure and pulmonary vascular resistance. Prolonged labour, use of systemic opioids and inadequate hydration are all, therefore, risk factors for these women.
Regional analgesia has been used successfully. Epidural infusions or intermittent boluses of low concentrations of local anaesthetic and opioid (0.0625-0.1% bupivacaine with fentanyl 2.0-2.5 μg/ml; alternatively opioid alone) provide good analgesia without compromising haemodynamic stability. Combined spinal-epidural analgesia is a suitable alternative but offers little advantage over low-dose epidural analgesia, except possibly more profound analgesia if opioids alone are used. Use of air to identify the epidural space should be avoided because of the risk of air embolism.
Although general anaesthesia has traditionally been recommended for women with pulmonary hypertension, regional anaesthesia has been successfully used for both Eisenmenger’s syndrome and primary pulmonary hypertension. It is imperative to use a slow titration technique and invasive central monitoring if regional anaesthesia is chosen.
General anaesthesia offers potentially greater haemodynamic stability, and the opportunity to minimise oxygen consumption by eliminating the work of breathing and maximising arterial oxygen saturation. It also facilitates transoesophageal echocardiography and the administration of inhaled pulmonary vasodilators such as 100% oxygen, nebulised prostacyclin or nitric oxide; use of the latter two has been described, although their place in improving oxygenation is still uncertain. However, the cardiodepressant effects of general anaesthesia with associated reduction in cardiac output are still hazards for these women, as is the potentially increased risk of thromboembolism. A high-dose opioid ‘cardiac’ general anaesthetic provides maximal haemodynamic stability. There is no particular advantage in elective ventilation postoperatively, but high-dependency or intensive care nursing is mandatory.
Postoperative and post-delivery analgesia can be provided by patient-controlled intravenous opioids or by epidural or intrathecal opioids. Intensive care admission should be planned, and invasive monitoring must be continued for several days; women with pulmonary hypertension are frequently successfully delivered, only to die during the first 2 weeks after delivery because of acute increases in pulmonary vascular resistance coupled with volume overload. Mortality is associated with pulmonary hypertensive crises, thromboembolism or refractory right heart failure.
Key points
• Pregnancy is extremely hazardous for women with pulmonary hypertension.
• Maternal mortality may be as high as 60%.
• The physiological changes of normal pregnancy are poorly tolerated by women with pulmonary hypertension.
• Hypovolaemia and any increase in pulmonary vascular resistance must be avoided.
• Cautious use of regional analgesia for vaginal delivery, with full invasive cardiovascular monitoring, is recommended.
• Both general and epidural anaesthesia have been used for operative delivery; both have significant risks.
Further reading
Curry R, Swan L, Steer PJ. Cardiac disease in pregnancy. Curr Opin Obstet Gynecol 2009; 21: 508-13.
Lane CR, Trow TK. Pregnancy and pulmonary hypertension. Clin Chest Med 2011; 32: 165-74.
Rex S, Devroe S. Anesthesia for pregnant women with pulmonary hypertension. Curr Opin Anaesthesiol 2016; 29: 273-81.
Sliwa K, van Hagen IM, Budts W, et al.; ROPAC investigators. Pulmonary hypertension and pregnancy outcomes: data from the Registry Of Pregnancy and Cardiac Disease (ROPAC) of the European Society of Cardiology. Eur J Heart Fail 2016; 18: 1119-28.