Summary
Background
Rheumatic heart disease (RHD) is an important public health issue, particularly in the Pacific region, but its true burden is unknown.
Objectives
To evaluate the prevalence of rheumatic heart disease (RHD) in young adults from New Caledonia, based on echocardiography, and to evaluate the accuracy of dynamic criteria, focusing on mitral valve (MV) leaflet motion.
Methods
Blind analysis of echocardiography by three cardiologists; diagnosis of RHD required at least one dynamic criterion (exaggerated or restricted MV leaflet motion); subjects with morphological criteria (MV leaflet thickening), but without dynamic criteria, were considered as borderline.
Results
There were 834 subjects from three socioeconomic groups, aged 18–22 years: 699 had normal echocardiography; 93 (11.5%) had physiological regurgitation; nine (0.9%) had borderline RHD; and five (0.59%) had RHD. The prevalence of RHD in New Caledonia was thus estimated at 5.9 per 1000 (95% confidence interval 2.6–12.2). The RHD cases were of Pacific ethnicity. Physiological regurgitation was more frequent in Pacific subjects (13.7%) than in non-Pacific subjects (6.9%; P < 0.0001). RHD was more prevalent in the lowest socioeconomic group. No disagreement occurred between the three reviewers concerning analysis of dynamic criteria; all disagreements were related to morphological criteria.
Conclusions
The prevalence of echocardiographically diagnosed RHD in adults in New Caledonia is estimated at 5.9 per 1000; it occurs most frequently in Pacific subjects and those with low incomes. Dynamic criteria were more accurate and reproducible than standard morphological criteria.
Résumé
Contexte
La valvulopathie rhumatismale (VR) est une importante question de santé publique, particulièrement dans la région Pacifique, mais son vrai fardeau est inconnu.
Objectifs
Évaluer la prévalence de la VR chez l’adulte jeune en Nouvelle Calédonie, basé sur l’échocardiographie et évaluer la précision du critère dynamique, se concentrant sur les mouvements des feuillets de la valve mitrale (VM).
Méthode
Analyse en aveugle des échocardiographies par trois examinateurs ; le diagnostic de VR requérant au moins un critère dynamique (mouvement exagéré ou restrictif d’un feuillet de la VM) ; les sujets avec des critères morphologiques (épaississement de feuillet de la VM), mais sans critère dynamique, sont considérés comme borderline .
Résultats
Sur les 834 sujets des trois groupes socio-économiques, âgés de 18 à 22 ans : 699 avaient une échocardiographie normale ; 93 (11,5 %) avaient une fuite physiologique ; neuf (0,9 %) une VR borderline ; et cinq (0,59 %) une VR avérée. La prévalence de la VR en Nouvelle Calédonie a été ainsi estimée à 5,9 pour mille (95 %, intervalle de confiance 2,6–12,2). Les cas de VR sont de l’ethnicité Pacifique. Les fuites physiologiques étaient plus fréquentes chez les sujets du Pacifique (13,7 %) que chez les sujets non-Pacifique (6,9 % ; p < 0,0001). La VR était plus importante dans le groupe socio-économique le plus défavorisé. Aucun désaccord n’est survenu par les trois examinateurs concernant l’analyse du critère dynamique ; l’ensemble des désaccords étaient relatif aux critères morphologiques.
Conclusions
La prévalence de la VR diagnostiquée échocardiographiquement est estimée chez l’adulte en Nouvelle Calédonie à 5,9 pour mille ; sont plus touchés les sujets d’éthnicité Pacifique et ceux à bas niveau socio-économique.
Background
Rheumatic heart disease (RHD) is an important public health issue worldwide and particularly in the Pacific region . In many countries, school-based echocardiographic screening for RHD is being conducted . These and other studies suggest that the prevalence of RHD increases steadily during the teenage years, peaking in young adults . However, by not including older adolescents and young adults, school-based RHD screening programmes may underestimate the true burden of RHD in the population. Unfortunately, screening of adults is notoriously difficult, mainly because of low participation rates, but at least one study (in Nicaragua) has managed to screen for RHD in an adult population .
Echocardiography is a very sensitive tool for the screening of RHD, compared with cardiac auscultation . The echocardiographical criteria required for the diagnosis of RHD have been debated , although the recent publication of the World Heart Federation criteria for echocardiographical diagnosis of RHD provides an evidence-based foundation for future research and practice . The diagnosis of RHD requires the presence of Doppler criteria confirming pathological valvular regurgitation, and a range of morphological criteria.
Morphological criteria can be separated into static criteria, analysed on frozen two-dimensional images (thickening and/or retraction of the valve leaflets and/or subvalvular apparatus), and dynamic criteria, assessed by frame-by-frame analysis (excessive or restricted mobility of valve leaflets). We hypothesized that any significant chordal and/or subvalvular mitral valve (MV) apparatus shortening or retraction should translate into a limitation of MV leaflet tip motion, which could be accurately and highly reproducibly assessed with a dynamic analysis of two-dimensional echocardiography images, focusing on the position of the MV leaflet tips with regard to the MV annulus plane throughout the cardiac cycle.
Since 2007, echocardiography has been used as a screening tool for RHD in 10-year-old school children in New Caledonia . Although a list of criteria and recommendations for RHD diagnosis were established by the coordinator of the programme (Agence Sanitaire of New Caledonia), the final diagnosis of RHD is confirmed by the cardiologists participating in the programme, on the basis of their own expertise. Using this method, the prevalence of RHD in 10-year-old children has been found to be approximately 13 per 1000 (unpublished data from Agence Sanitaire of New Caledonia).
Because the prevalence of RHD in adults in New Caledonia is unknown, we conducted a prospective echocardiographical screening study to evaluate the prevalence of RHD among young adults (aged 18–22 years) from New Caledonia. Our secondary aims were to identify high-risk subgroups as screening targets for future prevention programmes and to evaluate the accuracy and reproducibility of the echocardiographical criteria we used for the diagnosis of RHD, putting special emphasis on the dynamic analysis of MV leaflet motion.
Methods
Study design and participants
New Caledonia is administratively divided into three provinces: North, South and Islands. The population is 246,000, with two-thirds living in Nouméa and its suburbs in the South Province . The population of New Caledonia includes people of Pacific ethnicity (Melanesians, 44%; Polynesians, 14% [composed of Wallisians, Futunians and French Polynesians]) and non-Pacific ethnicity (Caucasians, 34%; Asians, 8%).
The population of people aged 18–22 years is estimated as being 13,500 in the South Province , and they can be divided into three distinct groups: 6480 (48%) are students; 3645 (27%) are workers or apprentices; and 3375 (25%) are non-schooled and unemployed (this is the lowest socioeconomic group, who frequently live in tribal villages or shanty towns) .
Sampling
Based on an anticipated RHD prevalence of 30 per 1000, the minimum sample size required was 1250 for a 95% confidence interval (CI) of ± 10 per 1000.
We aimed to sample the three groups roughly according to their distribution in the population, as reported in the 2009 census supplied by Institut de la Statistique et des Études Économiques (ITSEE) . The group of students (group 1, n = 596) was composed of subjects randomly selected from an enrolment list obtained from universities; the group of workers (group 2, n = 335) was composed of subjects randomly selected from a list of apprentices in the Chamber of Commerce of Nouméa or from the Department of Occupational Medicine of New Caledonia; the group of out-of-school and unemployed subjects (group 3, n = 339 subjects) was planned to be composed of subjects recruited using purposive sampling by our local social workers’ network.
Ethics approval was obtained from the Public Health Authorities of the South Province. Information about the study and RHD was provided to the institutions involved and to sampled subjects. Written informed consent was obtained from all participants before screening was performed.
Vital status on 31st December 2012 was checked in the national register; no patient with RHD died during the follow-up period (median 2.3 years).
Screening procedure
Personal or familial past history of acute rheumatic fever or RHD was recorded by asking the participants. The subject’s ethnic group was defined by the subject. Cardiac auscultation was not performed.
All echocardiographical examinations were performed by a single operator (investigator 1), between May and December 2010, in either an infirmary or a dedicated classroom, using a Vivid i™ (GE Healthcare, Freiburg, Germany) portable cardiac ultrasound machine and a multifrequency 3S adult probe (1.9–3.8 MHz).
A standard protocol was used for the acquisition, recording and storage of echocardiographical data. Imaging was performed in standard parasternal long and short axis, and apical four-chamber views. Depth, sector size and gain were optimized to achieve maximal frame rate and resolution; a second harmonic frequency was used if needed. Colour Doppler was used with the highest aliasing velocity allowed by the machine; pulsed and continuous Doppler were used to assess velocity and the spectral envelope of transvalvular flow and regurgitations.
Reading of echocardiograms
A blind and separate analysis was performed by the three investigators, reviewing stored images directly on the echocardiography machine; in case of disagreement, the final diagnosis was established by consensus between the investigators. Each reader was asked to categorize each echocardiogram as normal, physiological regurgitation, borderline RHD or definite RHD, according to predefined criteria established by our group in 2009, before the World Heart Federation RHD criteria were published and became the gold standard for RHD screening in 2012 ( Table 1 ). In contrast to the World Heart Federation criteria, we required the presence of at least one dynamic criterion to accept the diagnosis of definite RHD; in the absence of abnormal MV leaflet motion, or even in the presence of one or several static morphological criteria (leaflet thickening and/or subvalvular apparatus retraction), the case was labelled as ‘borderline RHD’.
| RHD diagnosis categories a | |
| Normal echocardiography | No valvular regurgitation and no MS |
| Physiological regurgitation | Valvular regurgitation, without all four Doppler criteria and without morphological criteria |
| Borderline RHD | Pathological valvular regurgitation, with at least one morphological static criterion, but without dynamic criteria |
| No valvular regurgitation, with morphological criteria, but without dynamic criteria | |
| Definite RHD | Pathological regurgitation and at least one dynamic criterion or MS |
| Criteria | |
| Doppler criteria (the diagnosis of pathological valvular regurgitation [e.g. non-physiological] required all four criteria) | Holosystolic (MR) or holodiastolic (AR) jets (with homogeneous spectral envelope on at least three consecutive cardiac cycles) |
| Peak velocity ≥ 3.5 m/s | |
| Seen in two views | |
| Regurgitation jet length ≥ 2 cm (in at least one view) | |
| Morphological criteria | |
| Static criteria: MV | Retraction or thickening of chordal/subvalvular apparatus |
| AMVL thickening ≥ 3 mm | |
| Static criteria: AV | Thickening of aortic cusp |
| Coaptation defect | |
| Dynamic criteria: MV | Decreased mobility of PMVL, with normal mobility of AMVL: false prolapse of AMVL (leading to a posterior direction of MR jet) |
| Decreased mobility of AMVL tip (dog-leg or MS aspect) | |
| Excessive mobility of AMVL or PMVL: valve prolapse due to chordal elongation or chordal rupture | |
| Dynamic criteria: AV | Restricted motion in opening |
| Cusp prolapse | |
| Mitral stenosis (mean gradient ≥ 4 mmHg) |
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