Heart disease – why is maternal mortality increasing?

Authors


Dr E Gelson, Academic Department of Obstetrics and Gynaecology, Imperial College London, Chelsea and Westminster Hospital, 369 Fulham Road, London SW10 9NH, UK. Email egelson@imperial.ac.uk

The most recent triennial confidential enquiry confirmed that heart disease is the most common cause of maternal death in the UK. The maternal mortality rate associated with heart disease is 2.27 per 100,000 maternities double that reported in 1990.1 The incidence of heart disease during pregnancy in the UK has remained constant at 0.9% over several decades.2 However, the severity of heart disease and the risk it poses during pregnancy appear to be increasing in a wide range of healthcare settings. This commentary examines why mortality rates have risen and makes recommendations as to how this trend can be reversed.

Ischaemic heart disease is now the most common cause of cardiac death in the pregnant population in the developed world. This is likely due to increased maternal age; smoking; the adoption of a sedentary lifestyle and poor diet leading to greater rates of obesity, diabetes and hypertension.3–6 Acute myocardial infarction accounts for the majority of deaths and is most commonly due to coronary atherosclerosis, but coronary artery dissection and consequent occlusion are also relatively frequent. There is a high incidence of recognised risk factors for atherosclerosis in pregnant women suffering an acute myocardial infarction during pregnancy and the postpartum period, which should be targeted both for intervention and for identification.6 Hyperlipidaemia, hypertension and diabetes should be optimally controlled preconception and smoking cessation and weight loss strongly encouraged. Women with multiple risk factors should be identified, alerting obstetricians to the possibility of ischaemic heart disease and lowering thresholds for the investigation of symptoms. When myocardial infarction is suspected or diagnosed, cardiac catheterisation with acute phase intervention (thrombolysis and/or coronary angioplasty) should not be withheld; these procedures are relatively safe in the pregnancy,7 although larger studies are required to determine their specific risk to benefit ratios. Following the acute phase, secondary prevention (such as optimal blood pressure control, aspirin and statins [see below]) should be instituted. Many cardiac medications can be used without undue risk in pregnancy, for example beta blockers, digoxin, aspirin, diuretics and hydralazine. ACE inhibitors are known to have teratogenic effects in the first trimester and should therefore best be avoided during early pregnancy.8 Exposure in the second and third trimesters can lead to marked fetal hypotension and decreased fetal renal blood flow. Where ACE inhibitors must be continued, the lowest possible dose should be used and amniotic fluid levels and fetal growth should be monitored carefully. Statins have been identified as potential teratogens on the basis of theoretical considerations. However, epidemiological data suggest this to be unfounded. Given the scarcity of available data, it is still advisable to avoid statins during the first trimester,9 but in situations of known ischaemic heart disease or severe hyperlipidaemia, their use during the second and third trimesters may be considered.

The latest UK enquiry highlighted aortic dissection as another important cause of maternal death.1 The combination of increased blood flow and pregnancy-induced structural changes in the aorta are likely to contribute to this increased risk.10 The precise mechanism remains unclear, as the structural changes in the aorta specifically and in the maternal systemic vascular bed during pregnancy in general have not been studied in any detail. This increased risk of dissection during pregnancy is even greater in women with pre-existing heart conditions such as Marfan syndrome, bicuspid aortic valve with ascending aortopathy, coarctation of the aorta11 and perhaps tetralogy of Fallot.12 Intrinsic abnormalities of the aortic wall, abnormal flow patterns with increased shear stress and/or abnormal aortic pulsatility are all additional risk factors for aortic dissection. The long-term effects of pregnancy on the aorta and the extent that this is reversed following delivery in the presence of any of these pre-existing risk factors remains unknown. Anecdotal experience would suggest that pregnancy accelerates the rate of dilatation and consequently the need for operative intervention. Even if research does eventually define the mechanisms responsible for pregnancy-related aortic dissection, identifying every single pregnant woman who will dissect will remain challenging. For the time being, attention should be focused on identifying women with predisposing conditions, recommending appropriate and timely interventions to modify their risks (i.e. valve sparing aortic root replacement in women with Marfan syndrome and more than mild aortic root dilatation before conception). During pregnancy, antenatal visits should be more frequent to diagnose and treat hypertension at lower levels than usual, aiming to keep the blood pressure below 130/90 and to observe closely for symptoms or signs of aortic dissection (sudden onset of severe chest pain, radiating to the back, often with syncope, dyspnoea, dysphagia, a new diastolic murmur, an asymmetrical peripheral pulse and/or different blood pressure recordings between the two arms and the legs).

The rates of maternal death related to structural congenital heart disease have declined progressively in recent years, suggesting that management may have improved, partly through increased awareness. However, advances in cardiac medicine and surgery over the past few decades have led to a dramatic increase in the incidence of congenital heart disease in the adult population with 85% of infants with congenital heart disease now surviving into adult life.13,14 The prevalence of congenital heart disease at birth remains constant at about 7 per 1000 live infants, that is this is a very common inborn condition. Furthermore, the complexity of women with congenital heart disease is increasing; it is estimated that approximately 1600 people with complex congenital heart disease enter adulthood every year in the UK alone.15 Women with a previous Fontan operation, pulmonary arterial hypertension and even hypoplastic left heart syndrome now survive to adulthood and are choosing to get pregnant, posing additional challenges to the profession not only in terms of numbers but also complexity of the underlying lesion and the reparative surgery employed. Congenital heart disease is now by far the most common cause of heart disease in pregnancy in the developed world.15. Given the heterogeneity of congenital heart disease and the dynamic nature of surgical and catheter therapies, there are real limitations for developing prospective and appropriate pregnancy management protocols. Recent longitudinal prospective16,17 and cohort studies18–21 combined with professional recommendations22,23 have provided some management guidelines, but the evidence base must be expanded and improved if we are to continue to improve outcomes. Seamless transition from paediatric to adult congenital heart disease services is an important step in the management of future pregnancy enabling timely prepregnancy counselling and appropriate contraception advice.24

The latest confidential enquiry1 reported the first two deaths in the UK due to rheumatic heart disease since the 1991–1993 enquiry. Both deaths were in recent immigrants, underlining the fact that rheumatic heart disease remains prevalent in many developing countries. The level of immigration to the UK and other developed countries means that we are experiencing a re-emergence of these conditions, with the numbers of pregnant women with rheumatic heart disease bound to increase over the coming years. In the same way that we keep the possibility of malaria and other less common tropical infections at the forefront of our minds in those who have recently travelled to high-risk areas who present with suspicious symptoms, we should be mindful of the possibility of rheumatic heart disease in women who have moved to the UK from areas where rheumatic fever remains endemic. Such women should be advised to have a complete cardiovascular examination by an appropriately trained doctor at booking. Only with diagnostic vigilance for heart disease coupled with a low threshold for investigation of symptoms and appropriate cardiac care can clinicians prevent a further increase in cardiac maternal mortality.25

We must learn from our own experience. In the most recent UK confidential enquiry of the deaths associated with heart disease, two-thirds were in women who were overweight or obese. Care was considered substandard in nearly half the cases and in two-thirds of these the assessor thought that different care might have prevented death. Increasing numbers of deaths are occurring in women with previously undiagnosed heart disease but with recognised risk factors. The presence of these risk factors must be highlighted in the antenatal clinic so that the occurrence of cardiac symptoms (palpitations, chest pain, severe shortness of breath) will prompt early referral to the maternal medicine clinic for assessment and investigation. Women with pre-existing heart disease should be assessed preconceptually and risk factors for cardiac complications should be identified (prior cardiac event, baseline New York Heart Association class >II, cyanosis, left heart obstruction, reduced systemic left ventricular function and significant pulmonary regurgitation)13,14 and used to guide the intensity of antenatal and postnatal care. The immediate postnatal period is particularly high risk for the development of pulmonary oedema and heart failure and management in critical care settings should be advocated in the presence of pulmonary arterial hypertension, severe obstructive valve lesions and impaired ventricular function.

Initiatives such as the European Registry on Pregnancy and Heart Disease and the UK obstetric surveillance system are likely to improve our understanding of cardiac complications and their prognosis. However, if we are to improve the management of pregnancy complicated by heart disease, we need to focus our research efforts on understanding how heart disease impacts on the physiological cardiovascular adaptations during pregnancy and what the impact of pregnancy is on the natural history of the underlying heart condition. Combining the information from the registry with the results of such basic physiological studies will allow us to develop appropriate interventions, the impact of which can be tested in prospective multicentre studies. Ultimately, we should be able to improve pregnancy outcomes for both women with pre-existing and acquired heart disease. Until then, we must concentrate on raising the profession’s awareness of the possibility of heart disease in pregnant women and support management protocols based on the best evidence currently available to us.22,23

Disclosure of interests

None.

Contribution of authors

E.G. and M.R.J. wrote the commentary. M.A.G. and P.S. edited the commentary.

Ethics approval

Not required.

Funding

None.

Acknowledgement

None.

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