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Abstract
Background Despite numerous echocardiographic screening studies of children in high incidence acute rheumatic fever (ARF)/rheumatic heart disease (RHD) communities, little is known about the prevalence of RHD in adults in these populations.
We sought to determine the prevalence of RHD in an urban area of South Auckland, New Zealand, where previous studies had shown the prevalence of RHD in children to be around 2%.
Methods A cross-sectional screening study was conducted between 2014 and 2016. Echocardiography clinics were conducted at an urban Pacific-led primary healthcare clinic in New Zealand. Eligible persons aged 16–40 years were recruited according to a stratified randomised approach. Echocardiograms were performed with a standardised image acquisition protocol and reported by cardiologists.
Results There were 465 individuals who underwent echocardiograms. The overall prevalence of RHD (define and borderline) was 56 per 1000 (95% CI 36 to 78 per 1000). Definite RHD was found in 10 individuals (4 of whom were already under cardiology review at a hospital clinic) with a prevalence of 22 per 1000 (95% CI 9 to 36 per 1000). Non-rheumatic cardiac abnormalities were found in 29 individuals.
Conclusions There is a high burden of both rheumatic and non-rheumatic cardiac abnormalities in this population. Rates described in New Zealand are as high as lower-middle-income countries in Africa. Addressing knowledge gaps regarding the natural history of RHD detected by echocardiography in adults is a priority issue for the international RHD community.
- echocardiography
- epidemiology
- global burden of disease
- mitral valve insufficiency
Data availability statement
Data are available on reasonable request. Data requests should be directed to the corresponding author.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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WHAT IS ALREADY KNOWN ON THIS TOPIC
Echocardiographic studies have shown the prevalence of rheumatic heart disease to be around 1% among New Zealand (NZ) Maori children and 2% among Pacific children.
While there have been numerous echocardiographic rheumatic heart disease (RHD) screening studies among children around the globe, less is known about population-based prevalence of RHD in adults from high-risk populations.
WHAT THIS STUDY ADDS
We found that 2% or 1 in every 50 Polynesian young adults in South Auckland had definite RHD.
For every RHD case previously diagnosed by routine clinical services, primary care-based echocardiographic screening detected another case. A further 6% of screened individuals also had non-rheumatic cardiac abnormalities.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
Acute rheumatic fever and RHD prevention and control activities in NZ must be targeted at young adults as well as children.
Portable echocardiography is feasible in primary care clinic settings and may improve access to cardiology services.
Background
Rheumatic heart disease (RHD) is a significant global health problem, particularly affecting low-income and lower-middle-income countries, where RHD is estimated to affect over 33 million adults and contribute to over 300 000 deaths annually.1 2 In 2018, the 71st World Health Assembly unanimously adopted a resolution calling for multisectoral action to accelerate RHD prevention and control activities.3
Current estimates of global RHD burden are drawn from numerous echocardiographic screening studies in children4 along with disease registries and cohort studies describing hospital presentations with severe RHD in high disease burden populations.5
There is a paucity of data regarding the prevalence of RHD in adolescents and young adults. Until recently, only a few population-based echocardiographic screening studies have examined adolescents and young adults,6–10 and these were conducted prior to the publication and subsequent widespread adoption of the World Heart Federation (WHF) consensus diagnostic criteria for RHD in 2012.11 Two more contemporary studies in Northern Australia and Timor-Leste have evaluated cohorts which included children and adolescents up to the age of 20 years, using abbreviated imaging protocols.12 13 The natural history of recurrent acute rheumatic fever (ARF) progressing to chronic RHD is such that the majority of global RHD burden occurs in adults. Knowledge of RHD prevalence and the full spectrum of RHD severity in adults living in high-burden ARF/RHD populations are, therefore, urgently needed to inform prevention and control programmes.
There is a high incidence of ARF and chronic RHD among Polynesian and Māori children and young people in South Auckland, New Zealand (NZ).14 15 Furthermore, in NZ, there are marked disparities in ARF and RHD burden, with virtually no cases occurring among people of NZ European ethnicity.16 Māori and Pacific peoples comprise 15% and 7% of NZ’s overall population, respectively, and approximately 35% of those under 15 years of age.17
In NZ, ARF episodes are recognised to occur in young adults as well as children.14 18 We hypothesised that the prevalence of RHD in adults would be at least as high as rates seen in a corresponding population of NZ school-aged children where RHD is known to be endemic.
Aims
We sought to determine: (1) the prevalence of RHD in adults in an urban, high-incidence ARF population and (2) The feasibility of portable echocardiographic screening for RHD in an urban primary healthcare setting.
Materials and methods
Study setting
This study was conducted in Otara, South Auckland, at a Pacific-led urban primary healthcare organisation where over 95% of enrolled clinic patients identify as Pacific peoples.
South Auckland, NZ, is an ethnically diverse urban area characterised by high levels of socioeconomic deprivation. The population of approximately 534 000 people is made up of 21% Pacific peoples and 16% NZ Māori.17
Participant selection, sample size and randomisation
The study population consisted of young adults aged 16–40 years who were enrolled at a Pacific primary healthcare clinic in Otara, South Auckland. Those who were not resident in South Auckland at the time of the study or who did not have a current address or telephone contact details were deemed ineligible.
Of the 1224 eligible patients, 724/1224 (59%) were female. The median age was 25 years (IQR 20–32 years). Pacific peoples made up 97% of the eligible population. A total of 1010/1224 identified as Samoan, 84/1224 were Tongan, 50/1224 Cook Island Māori, 34/1224 NZ Māori and the remaining 46 were from other Pacific nationalities. A total of 1224 eligible individuals were identified from clinic records and approached using a randomisation scheme.
An a priori power analysis was performed for sample size calculation, based on a known prevalence of definite RHD of around 1% in high-risk NZ children. With an alpha=0.05 and power=0.80, we determined a minimum sample size of 400 individuals would be required to estimate RHD prevalence comparing adults and children in South Auckland. Random numbers were assigned to the 1224 eligible patients, who were then approached by clinic staff in sequential order and invited by telephone and written information pamphlets to participate in the study. Pamphlets and consent forms were provided in Samoan, Tongan and Te Reo Māori and the clinic staff were fluent speakers of Pacific languages.
Enrolment procedures
Eligible individuals were telephoned by the clinic receptionist and invited writing in to attend for an echocardiogram appointment. Echocardiography clinics were undertaken between December 2014 and March 2016.
On arrival to the clinic, the coordinating investigator met with potential participants to discuss the study and written informed consent was obtained. Only 1 person out of the 466 approached declined to participate in the study.
A brief structured questionnaire was administered to ascertain demographic details, personal and/or family history of ARF/RHD, of type 2 diabetes, hypertension, other cardiac diseases and medication history. Where relevant, electronic clinical records were reviewed in order to clarify RHD status and severity for those who reported a history of ARF/RHD.
Height and weight were measured and body mass index (BMI) was calculated.
Echocardiography procedures
Echocardiograms were performed on a Vivid Q (GE, General Electric Corporation, Chicago, Illinois, USA) portable platform with a 3S 2.2 MHz transducer by highly experienced cardiac sonographers. Images were acquired and reported using standardised protocols previously used in NZ by this group of investigators.15 19
Two-dimensional and colour Doppler images were obtained in parasternal and apical views, with multiple colour sweeps of any mitral or aortic regurgitant jets identified. Pulse-wave Doppler interrogation of regurgitation jets was performed to assess peak velocity, duration through the cardiac cycle and spectral envelope. Valve leaflet morphology and thickness were assessed in parasternal long axis (mitral and aortic) and parasternal short axis views (aortic valve) using previously described methods.20 Images were electronically stored in Digital Imaging and Communications in Medicine format.
Left ventricular size and function were assessed by M mode. Additional images were obtained at the discretion of the sonographer.
Echocardiograms were reviewed by one investigator (NC-S) and studies showing any potential abnormalities were then reported by a panel of cardiologists (NJW, JS, TLG and RD), blinded to the participant’s demographic details and clinical history. RHD findings were classified as definite or borderline RHD according to WHF diagnostic criteria for RHD.11 Two cardiologists reviewed all potentially abnormal echocardiograms, with a third cardiologist called in to adjudicate in the event of a disagreement.
Non-rheumatic echocardiographic abnormalities were interpreted in the context of available clinical information and clinical follow-up recommendations were made by an adult cardiologist (RD).
Participant follow-up
Individuals with abnormal echocardiograms were invited to return to discuss results and follow-up recommendations with a study doctor (NC-S and RW). Participants were then referred to their primary care provider doctor or hospital cardiology services as appropriate. Benzathine penicillin secondary prophylaxis was recommended for the following groups: definite RHD <21 years, definite RHD >21 years if severe/post-RHD surgery, borderline RHD with strong family history of ARF/RHD <21 years.
Statistical methods
Overall RHD prevalence was calculated by the sum of clinically detected cases and those newly detected by echocardiography.
RHD prevalence was reported per 1000 population, with 95% CIs calculated for proportions. Statistical analyses were performed on SAS V.9.1.3 (SAS Institute).
Results
Demographics of study population
A total of 465 individuals were recruited and underwent echocardiography, representing 38% of the total 1224 eligible young adult patients enrolled at the clinic. Median age of those undergoing echocardiography was 28.0 years (IQR 20.7–34.9 years). Sixty-four per cent were female. Ninety-nine per cent of participants (460/465) identified as Pacific peoples. A total of 364 (78.3%) self-identified as Samoan, 44 (9.5%) were Tongan, 18 (3.9%) were Cook Islanders, 15 (3.2%) were NZ Māori 15 and 10 (2%) were Niuean.
Clinical history of ARF/RHD
Among the 465 individuals who underwent echocardiography, 8 (1.7% of the screened cohort) self-reported a history of ARF/ RHD. Of these eight, two were receiving regular benzathine penicillin injections and two had previously undergone heart valve surgery for RHD.
Family history of ARF/RHD was reported in 56/465 individuals (12%) and 31/465 (7%) reported a first-degree relative with ARF/RHD.
Comorbidities
Type 2 diabetes or pre-diabetes was reported by 33/465 (7%) of the cohort and 21/465 (4.5%) had hypertension.
Significant non-rheumatic cardiac disease occurred in four individuals (cardiac ablation procedure for Wolff-Parkinson-White syndrome, atrial myxoma surgery, non-ST elevation myocardial infarction, infective endocarditis).
The median BMI of participants was in the obese range. The median BMI of female participants was 35.3 (IQR 30.6–40.9) and the median BMI of male participants was 33.2 (IQR 27.1–38.9).
Echocardiographic prevalence of RHD
The overall prevalence of RHD (definite and borderline) was 56 per 1000 (95% CI 36 to 78 per 1000). Definite RHD was found in 10 individuals (4 of whom were already under cardiology review at a hospital clinic) with a prevalence of 22 per 1000, and Borderline RHD was found in 16 individuals <20 years of age (see table 1).
Prevalence of RHD detected by echocardiography in Polynesian young adults
Detailed description of valvular abnormalities
Among the 10 individuals with definite RHD, there were 5 females and 5 males. There was a wide spectrum of findings and disease severity. Five individuals had mixed disease involving the mitral and aortic valves (see table 2).
Clinical features of study participants with definite RHD
Of the eight individuals who reported a history of previously diagnosed ARF/RHD, three had normal echocardiograms, one had borderline RHD and four had definite RHD.
RHD clinical management and outcomes
Eight patients with RHD were referred to hospital cardiology clinics. Four individuals who were young, or with severe RHD and/or family history commenced BPG secondary prophylaxis as a result of participation in this study, as per NZ clinical guidelines for ARF diagnosis and management.21
There were 11 individuals with non-rheumatic abnormalities who were referred to hospital cardiology clinics for further evaluation, on the recommendation of the study cardiologist.
Prevalence of non-rheumatic echocardiographic abnormalities
Non-rheumatic echocardiographic abnormalities were identified in 29/465, 62 per 1000 (95% CI 33 to 73 per 1000) comprising: left ventricular hypertrophy with or without impaired function (n=12), mild structural variations of the mitral valve (including congenital prolapse) without other features of RHD (n=6), dilated aortic outflow tract (n=4), right heart dilatation (n=2), annular calcification (n=1), septal hypertrophy or hypokinesis (n=3) regional wall abnormality (n=1).
Discussion
Key findings
This study describes RHD prevalence in Polynesian adults living in an urban environment and high-income country and is also one of only a few publications to describe RHD prevalence in adults using the internationally accepted WHF diagnostic criteria.22 23 Our study, thus, addresses important knowledge gaps around burden of RHD in adults from high incidence ARF populations.
Among the screened cohort of 465 young adults, 5.6% had features of RHD on echocardiography and 2.2% met WHF criteria for definite RHD. In other words, up to 1 in 50 young adults of Pacific ethnicity in South Auckland may be living with RHD. These are disturbingly high rates, but are in keeping with the 1:150 incidence of ARF in NZ children living in socioeconomic deprivation14 and the high prevalence of RHD previously reported in NZ Pacific children.15 24
Four (0.9%) of the cohort of 465 individuals who underwent echocardiography also had a prior history of clinically diagnosed RHD. For every definite RHD case previously identified through routine clinical care pathways, echocardiographic screening detected an additional case of definite RHD.
Severity and clinical significance
The prevalence and severity of RHD described in this population is higher than reported in many other endemic RHD regions, even accounting for less stringent diagnostic criteria in earlier studies. Only in Uganda has adult RHD prevalence been described in adults using WHF criteria. Scheel et al found a similar prevalence rate of approximately 20 per 1000, however, disease severity was substantially lower in Uganda as compared with South Auckland, NZ (see table 3).22 Seven out of 10 individuals with definite RHD in our cohort had RHD graded as moderate or severe and 2 (0.4%) had previous RHD surgery.
Echocardiographic studies of RHD prevalence in adolescents and adults
Our findings contribute to improved understanding of the clinical significance and natural history of RHD. We found a higher prevalence of definite RHD in young adults (2%) as compared with schoolchildren (1%) using WHF criteria24 in keeping with ARF epidemiology in NZ, where ARF cases are reported in adolescents and young adults in addition to schoolchildren.16 Our finding that RHD prevalence in adults was modestly higher than childhood rates, coupled with the observation that four individuals with a prior clinical diagnosis of ARF/RHD had normal follow-up echocardiograms, highlights that RHD may take a variable course over time and may progress, remain stable or improve.25–27
We have reported borderline RHD prevalence strictly in accordance with the WHF criteria, which do not include a borderline RHD category for adults aged over 20 years; our findings are an important addition to the emerging data of the natural history of echocardiographically detected RHD and highlight a future research priority in high-risk populations where echocardiographic screening programmes are under consideration. Future longitudinal follow-up studies of adults >20 years with borderline RHD features would help to clarify the clinical significance of these findings and inform clinical practice guidelines for this group of individuals.
Non-rheumatic abnormalities
Use of a detailed echocardiographic protocol by experienced cardiac sonographers using high-quality portable machines, together with specialist cardiology review of all echocardiograms and blinded assessment by multiple reviewers for those with suspected abnormalities, enabled careful and unbiased evaluation for both rheumatic and non-rheumatic abnormalities. Overall, 12% of the cohort was found to have echocardiographic abnormalities, with similar proportions of rheumatic and non-rheumatic abnormalities (5.5% and 6.2%, respectively). High rates of non-rheumatic changes, particularly left ventricular dysfunction, are consistent with an echocardiographic study conducted in NZ Māori.28 Likely contributing factors include the high prevalence of non-communicable diseases (NCDs) including type 2 diabetes, obesity and hypertension in NZ Pacific and Māori populations.
Similarly high prevalence of non-rheumatic cardiac abnormalities could be anticipated in other resource-limited settings where RHD and high NCD burden coexist. To date, non-rheumatic abnormalities have only been described in a new Caledonian RHD screening study, where a similar spectrum of abnormalities to those found in NZ were noted,7 and more recently, in Northern Australia and Timor-Leste, where the prevalence of congenital abnormalities was around 2%.12 13 This may be due to limited capacity for detailed echocardiography reporting by expert cardiologists in many settings where RHD echocardiographic studies have been conducted. Programmes designed to detect RHD may not recognise non-rheumatic cardiac abnormalities. Our findings also emphasise the importance of considering RHD control alongside other NCD programmes in resource-limited settings.
Primary care setting
This study demonstrates the feasibility of echocardiographic RHD case detection in a primary care setting and we believe this is the first study of its kind to be conducted within an urban primary care clinic. Ease of access to community-based echocardiography enabled individuals to participate and attendance at hospital was not required. Individuals with a clinical diagnosis of ARF/RHD who had previously defaulted from follow-up were also provided with an opportunity to re-engage with clinical care. The primary care-based study setting also enabled participants with cardiac abnormalities to be linked seamlessly back to their primary care physician for ongoing care and follow-up.
Secondary prophylaxis of RHD in adults
There is currently a lack of consensus in international guidelines relating to recommendations around the initiation and duration of secondary prophylaxis for adults with newly diagnosed RHD, detected by either clinical means or echocardiographic screening (see table 4). Variable practice regarding continutation of secondary prophylaxis in adults, has recently been described amongst a cohort of adults ≥35 years in the Northern Territory of Australia. 29 The decreasing risk of ARF with increasing age in adults is an ongoing conundrum for secondary prophylaxis recommendations in those with mild RHD.
Recommendations regarding secondary penicillin prophylaxis for adults with ARF/RHD
Understandably, the main focus of ARF diagnosis and management guidelines is to provide guidance regarding diagnosis and threshold for initiation of secondary penicillin prophylaxis for patients who are diagnosed with ARF or RHD after presenting with clinical signs and symptoms,30 as opposed to the minority who are diagnosed via echocardiographic screening. In our study, treatment recommendations were made on a pragmatic and individualised basis. Secondary prophylaxis was initiated in four individuals with definite RHD including younger adults <21 years, older adults with severe disease and those with a strong family history of ARF/RHD. Other adults in whom prophylaxis may be warranted include parents of young children and school teachers who are likely to be exposed to group A Streptococcus, and women in childbearing years where progression of RHD confers increased risk of pregnancy complications.
Potential limitations
Seven per cent of the screened cohort reported a family history of ARF/RHD in a first-degree relative. While it is possible that individuals with a family history of ARF/RHD may have been more motivated to participate in this study, selection bias was mitigated by use of a consistent randomisation approach to recruit participants. Furthermore, the age, gender and ethnic make-up of those who underwent echocardiography were broadly very similar to the overall eligible patient population enrolled at the clinic. Our findings reflect RHD prevalence in an urban NZ setting of high socioeconomic deprivation and household crowding, and as such may not be generalisable to other settings in NZ or the Pacific Islands. The high BMI of many individuals in this cohort meant echocardiographic image acquisition was technically challenging, which may have led to an underestimation of the true burden of RHD.
Research in context
Evidence before this study
Since the mid-2000s, numerous echocardiographic screening studies have improved understanding of the global prevalence and spectrum of RHD. To date, these studies have focused almost entirely on paediatric populations. Few published studies have described RHD prevalence in adults according to internationally accepted WHF consensus diagnostic criteria. The prevalence of definite RHD in indigenous Māori and Polynesian children using the WHF criteria in NZ is around 1%, however, the prevalence of RHD in adults in NZ is unknown.
Added value of this study
This study found that 2% or 1 in every 50 Polynesian young adults in South Auckland had definite RHD. For every RHD case previously diagnosed by routine clinical services, primary care-based echocardiographic screening detected another case. A further 6% of screened individuals also had non-rheumatic cardiac abnormalities. NZ is a high-income country, but RHD prevalence in Polynesian young adults living in urban South Auckland is as high as Africa. The majority of RHD cases had moderate or severe disease, highlighting major deficiencies in existing healthcare services for underserved and socioeconomically deprived populations in NZ.
Implications of all the available evidence
ARF and RHD prevention and control activities in NZ must be targeted at young adults as well as children. Addressing knowledge gaps regarding the burden and natural history of echocardiographically detected RHD in adults (including those with borderline changes) is a priority issue for the international RHD community.
Data availability statement
Data are available on reasonable request. Data requests should be directed to the corresponding author.
Ethics statements
Patient consent for publication
Ethics approval
Ethical approval obtained by the New Zealand Health and Disability Ethics Committee (HDEC) Reference number 13/STH/189. Locality approval obtained by the Counties Manukau District Health Board. Participants gave informed consent to participate in the study before taking part.
Acknowledgments
Sincere appreciation is extended to the staff and families of South Seas Healthcare Trust, Otara, in particular Mrs Lavinia Filiai, Project Administrator. The investigators would like to thank the study sonographers: Fiona Lean, Megan Burrows, Suzanne Davy-Snow, Kerry Conway and Denise Fong. Karishma Sidhu provided statistical assistance.
References
Footnotes
Contributors RW and NJW conceived and designed the study. RW contributed to data acquisition, analysis and led writing of the study report. NC-S and ET led data acquisition and analysis and critically reviewed the report NJW, JS, TLG and RD reported study echocardiograms, provided expert cardiology advice and critically reviewed the report. BP contributed expertise in adult RHD management and critically reviewed the manuscript. AC contributed expertise in Pacific primary healthcare to the study design, facilitated data acquisition and critically reviewed the manuscript. RW is the overall guarantor for the study.
Funding This study was funded by the Health Research Council of New Zealand, Rheumatic Fever Partnership Grant (HRC 13/965).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.