Still casting its long shadow: rheumatic heart disease in Australia and New Zealand

New Zealand and Australia share the ignominy of being affluent industrialised countries with rates of acute rheumatic fever (ARF) that are among the highest in the world and similar to those found in less developed countries.1 Rheumatic fever is generalised inflammatory illness mediated by antibodies mounted in response to infections with the group A streptococcal (GAS) bacterium. The acute illness mainly affects the heart, joints, skin and brain, but the initial illness and in particular recurrent episodes of ARF cause rheumatic heart disease (RHD) with lasting damage to the heart. ARF is a disease associated with poverty and overcrowding. Rates in most affluent countries have decreased markedly since the beginning of the 20th century following improvements in living conditions and access to health care. ARF and RHD are largely preventable with antibiotic treatment of GAS infections. The most concerning aspect of ARF and CHD is how they reflect major health inequalities in both countries. In Australia, rates of ARF in Aboriginal and Torres Strait Islanders are 200–300-fold higher than in non-Indigenous Australians, and in New Zealand (NZ) rates for Māori and Pacific peoples were 10.0 and 20.7 times higher than NZ Europeans, respectively. In New Zealand ARF is a notifiable disease, but in Australia is only notifiable in Western Australia, the Northern Territory and Queensland. Reports from 2002 in Australia reveal that the 58 cases of rheumatic fever in the Northern Territory and in 27 from Central Australia were in Aboriginal Australians with incidence rates in 5–14-year-old children in these regions of 346/100 000 and 365/100 000, respectively. In stark contrast, there were no reported cases of ARF in non-indigenous children living in the area.2 Recent data from NZ report a total of 1552 index admissions for ARF between 1993–2009.3 Over that period, rates of ARF increased by 79% and 73% for Māori and Pacific children, whereas in Non Māori/Pacific children the incidence fell by 71%. Māori and Pacific children accounted for 92% of new cases of ARF between 2000 and 2009, although 2006 census figures show that children from these ethnic groups make up only 30% of all NZ children. This study confirmed that ARF incidence in NZ is also strongly linked to socioeconomic deprivation assessed using a geographical area-based index based on variables including income, employment, telephone access, transportation, education, home ownership and education. The index is arranged in deciles where decile 1 represents the least disadvantaged and decile 10 the most disadvantaged domicile.4 Almost 90% of all index cases of ARF in children aged 5–14 years were in the top five deciles with 48% occurring in decile 10. For decile 10, Pacific children the annual incidence was 109 per 100 000, and for decile 9/10 Māori and Pacific children the incidence rates were 64.9 and 96.0 per 100 000, respectively.3 The risk of being admitted to hospital before the age of 15 for a child living in a region of high socioeconomic disadvantage (NZDep2006 decile 10) was calculated at one in 150. Rheumatic heart disease (RHD) is not a notifiable disease making it more difficult to determine its overall prevalence. In Australia, the prevalence of RHD has steadily increased since 2000 with RHD diagnosed in almost 2% of Aboriginal population in the Northern Territory and in 3.2% of Aboriginal people aged 35–44 years. Equivalent prevalence rates in NZ are unknown; however, 74% of the 225 women undergoing valve replacement surgery in an Auckland database were Maori or Pacific Island women with RHD.5 Pregnancy is a particularly high-risk time for women with heart disease, either congenital or acquired. The increased cardiac work of pregnancy with increases in stroke volume, heart rate and 30–50% increase in cardiac output (CO) place additional stress on a heart that is already compromised. Cardiac decompensation during pregnancy places women at higher risk of maternal and fetal morbidity and mortality. The most common valvular lesion in RHD, mitral stenosis (MS) is particularly aggravated as the increased CO further increases the pressure gradient across the mitral valve and tachycardia shortens diastolic filling time so that decompensation is common even in women with mild to moderate MS with reasonable functional status pre-pregnancy. Most reviews of RHD in pregnancy6 focus on the prevalence of this disease in women from the developing countries and comment that in ‘Western’ countries congenital heart disease is the predominant cardiac disease in pregnant women. It is lamentable that the legacy of high rates of childhood rheumatic fever in Australia and NZ contradicts these international perceptions. In addition, the strong association of risk factors leading to socioeconomic disadvantage with RHD further contributes to a woman's risk of developing pregnancy complications. North American7 and European7, 8 investigators have devised risk scores to predict which women with underlying cardiac conditions are at risk of developing maternal cardiac and fetal complications during pregnancy (Table 1). These tools were developed using data from large cohorts of women with congenital heart disease, and it is not clear how they perform in women with RHD. Indeed, there are limited published studies that report pregnancy outcomes in women with RHD. Silverside and co-workers9 reported maternal and fetal outcomes in 80 pregnancies in 74 women with rheumatic mitral stenosis (MS) in Toronto between 1986 and 2000. The women all either reported functional New York Heart Association (NYHA) class 1 (n = 71) or class II (n = 9) during pregnancy and women were judged to have mild MS in 42 pregnancies, moderate in 29 pregnancies and severe in nine pregnancies. Maternal cardiac events were reported in 28 pregnancies (35%) with the most frequent events being pulmonary oedema (n = 25) and arrhythmias (n = 9). The risk of cardiac complications increased as the degree of MS worsened, with cardiac events reported in 26% of pregnancies with mild MS (n = 11), 38% with moderate MS (n = 11) and 67% with severe MS (n = 6). Similarly, increasing severity of MS was associated with higher rates of adverse fetal outcomes, mainly prematurity and its complications: 21% (n = 9) adverse fetal events in pregnancies to women mild MS, 38% (n = 11) with moderate MS and 44% (n = 4) with severe MS. No maternal deaths were reported. A smaller study from Brazil10 reported maternal cardiac complications and fetal outcome in 45 pregnancies in 41 women with MS. Data are incomplete for the cohort but pre-pregnancy functional status was available in 39 women, of whom 23 (59%) were NYHA class I, 14 (36%) NYHA class II and 2 (5.1%) NYHA class III. Deterioration of functional cardiac status to class III or IV, the most common maternal complication, occurred in almost half of the women and was more frequent in women with NYHA class II or III than class I (OR 2.7 (95%CI 1.4–5.3)). As with the Toronto group, the rate of maternal complications increased with increased severity of MS. Maternal cardiac complications occurred in 95% of pregnancies (n = 18/19) to women with mitral valve area (MVA) <1 cm2, in 46% of pregnancies (n = 5/11) to women with MVA 1–1.5 cm2 and in only one of the 12 (8%) with MVA >1.5 cm2. Emergency balloon mitral valvotomy was performed in over one third of the women (n = 16) during pregnancy for worsening functional cardiac status, and emergency cardiac surgery was required in three women (6.7%). There was one maternal death. Low birth weight and preterm delivery were the most frequent fetal complications occurring in 29% (n = 10/34) and 24% (n = 10/42) respectively but did not appear to be predicted by increasing severity of maternal cardiac disease, although the data are incomplete, and the study may be underpowered to detect a difference. The Auckland group have published data reporting long-term outcomes in young women with prosthetic heart valves5 and maternal and fetal complications in a cohort of 31 women with mechanical heart valves treated with therapeutic dose enoxaparin during pregnancy,11 the majority of whom had rheumatic valvular disease. The study by Sartain and co-workers12 in this issue of the Journal is the first to report pregnancy outcomes in a cohort of Australian women with RHD. The group reported obstetric and cardiac outcomes from a retrospective case note analysis of 95 pregnancies in 54 women, 52 of whom were Indigenous Australians. Functional cardiac status using NYHA was recorded pre-pregnancy with any deterioration during pregnancy. Echocardiography was used to assess severity of RHD using parameters including valve area, ejection pulmonary hypertension. Use of cardiac medications and anticoagulants was recorded. Mitral valve disease, alone or with aortic valve disease was present in 97% of women (mitral valve alone; n = 62, mitral and aortic valve; n = 30) and three women had RHD affecting the aortic valve. Mitral stenosis (MS) was present in 41 women and was classified as severe in only one woman. The authors used a modification of the cardiac problems in pregnancy (CARPREG) cardiac risk developed by Siu and co-workers7 (Table 1). Primary cardiac complications (acute pulmonary oedema, arrhythmias, stroke, cardiac arrest or death) and secondary cardiac events (decline in NYHA status by ≥ 2 categories, transfer to cardiac surgical hospital or need for cardiac intervention) occurred in seven pregnancies but only in women assigned a cardiac risk score of >1 (7 of 19 pregnancies). No cardiac complications developed in the 70 women assigned a modified risk score of 0. Decisions regarding mode of delivery in women with cardiac disease are keenly debated with most centres advising that obstetric indications are used to determine whether vaginal delivery is the goal or elective caesarean section is required. Of note in this series, only two of 31 caesarean sections were carried out for ‘cardiac’ indications. This retrospective study provides introductory data that are somewhat reassuring in that the majority of pregnant women with RHD had uncomplicated pregnancies and deliveries. Its publication is very timely given the RHD in pregnancy study of the Australasian Maternity Outcomes Surveillance System13 will begin enrolling women later this year. This major trans-Tasman research collaboration that has received funding from the National Health and Medical Research Council from Australia and the NZ Health Research Council is a prospective survey of maternal and fetal outcomes in women from Australia and New Zealand with RHD. A qualitative study is also planned, using individual interviews and focus groups to explore aspects of women's journeys through pregnancy, in particular to determine barriers to engagement with care in the aim of identifying improvements of provision of pregnancy care. The results of these studies will provide important information on the long-term impact of ARF and RHD in our populations and strengthen the resolve to continue to address ways to reduce the impact of this preventable disease. In conjunction with allocation of major funding towards primary and secondary prevention programmes for ARF by governments of Australia and NZ, perhaps we can look to the future with more optimism that the glaring health inequalities caused by ARF and RHD for Aboriginal and Torres Strait Islanders in Australia and Maori and Pacific people in NZ will be diminished and ultimately eradicated.

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