Background
There is increasing use of portable echocardiography as a screening test for rheumatic heart disease (RHD). The prevalence of valvular regurgitation in healthy populations as determined using portable echocardiography has not been well defined. Minimal echocardiographic criteria for RHD have recently been clarified, but the overlap of normal and abnormal valvular regurgitation warrants further study. The aim of this study was to determine the spectrum of echocardiographic findings using portable echocardiography in children from a population with low prevalence of RHD.
Methods
Screening echocardiography was conducted in 396 healthy students aged 10 to 12 years using portable echocardiographic equipment. Echocardiograms were assessed according to 2012 World Heart Federation criteria for RHD. The prevalence of physiologic valvular regurgitation was compared with that found in previous studies of children using large-platform machines.
Results
Physiologic mitral regurgitation (MR) was present in 14.9% of subjects (95% CI, 11.7%–18.7%) and pathologic MR in 1.3% (95% CI, 0.6%–2.9%). Two percent (95% CI, 1.0%–3.9%) had physiologic aortic regurgitation, and none had pathologic aortic valve regurgitation. Physiologic tricuspid regurgitation was present in 72.7% of subjects (95% CI, 68.1%–76.9%) and physiologic pulmonary regurgitation in 89.6% (95% CI, 85.7%–91.8%). After cardiology review, no cases of definite RHD were found, but 0.5% of patients (95% CI, 0.1%–1.8%) had pathologic MR meeting World Heart Federation criteria for borderline RHD. Two percent (95% CI, 1.4%–4.6%) of the cohort had minor forms of congenital heart disease.
Conclusions
The spectrum of physiologic cardiac valvular regurgitation in healthy children as determined using portable echocardiography is described and is within the range of previous studies using large-platform echocardiographic equipment. The finding of two children with pathologic-grade MR, likely representing the upper limit of physiologic regurgitation, has implications for echocardiographic screening for RHD in high-prevalence regions.
Echocardiography is more sensitive and specific than cardiac auscultation for the diagnosis of rheumatic heart disease (RHD). The World Health Organization recommends screening for RHD in high-risk populations. The recent availability of compact portable echocardiography has led to growing use of this technology for RHD screening in a number of countries, including Cambodia and Mozambique, Tonga, Nicaragua, Fiji, New Zealand, and Australia. The 2012 standardized World Heart Federation (WHF) consensus diagnostic criteria for RHD now provide a uniform approach to the echocardiographic diagnosis of RHD and enable comparison between studies.
Characteristic RHD findings consist of left-sided valvular regurgitation and morphologic valve abnormalities. However, many normal valves in children and adults have minor degrees of regurgitation, and it is likely that these physiologic regurgitant jets may occasionally be of sufficient length to meet criteria to be labeled pathologic.
To inform and refine RHD diagnostic criteria, more information is needed about the background prevalence of left-heart valvular regurgitation and other echocardiographic findings in healthy low-incidence rheumatic fever pediatric populations.
Aims
The aim of this study was to define the spectrum of echocardiographic findings in children from a population with a low prevalence of RHD using portable echocardiography. We hypothesized that the prevalence of typical RHD valve abnormalities (defined as the combination of typical morphologic echocardiographic features and pathologic-grade regurgitation of mitral and/or aortic valve) in the low-risk population would be close to zero. We sought to determine the frequency of physiologic and pathologic mitral and aortic regurgitation and congenital abnormalities in healthy school-aged children to provide useful reference data for RHD screening programs.
Methods
Study Design and Participants
Children were selected from a school community in a high–socioeconomic status urban area where no cases of acute rheumatic fever (ARF) had occurred for >10 years (Diana Lennon, Regional Rheumatic Fever Register coordinator, personal communication). The demographic makeup of the school population was predominantly Caucasian/New Zealand European (72%). Twenty-two percent were Asian and 4% were Polynesian (New Zealand Maori and Pacific Peoples).
Ten- to 12-year-olds were targeted, an age group comparable with that used in a screening study using portable echocardiography conducted in 2007 and 2008 in South Auckland, a New Zealand community with a high incidence of ARF. In this community, the ethnic makeup is predominantly New Zealand Maori and Pacific Peoples, but the key determinant of ARF and RHD burden is socioeconomic deprivation. We targeted 10- to 12-year-olds because this is the peak incidence period for ARF and also because in the New Zealand health and education system, this age group was most readily accessible for a population-based screening approach.
Ethical approval for the study was obtained from the Regional Ethics Committee.
Educational sessions were conducted by the study nurse in school classrooms, which included explanation about the process of undergoing echocardiography. Information booklets were distributed to parents and caregivers, and written informed consent was obtained from all participants’ parents or caregivers.
A sample size of 400 was planned to detect a minimum 5% difference in the observed rate of isolated mild mitral regurgitation (MR) between high-incidence and low-incidence ARF populations, assuming that the prevalence of RHD was 3% in the high-risk group and 0.1% in the low-risk group and that pathologic-grade MR was present in 10% of high-risk students. These estimates were based on analysis of data from a previous RHD screening study conducted in South Auckland, a high-incidence ARF population, in 2007 and 2008.
Four hundred dix of 587 eligible students (69%) consented. Ten consenting students were not screened, because of school absence. Of the 396 children screened, 190 (48%) were female.
School Screening Procedures
Echocardiography was conducted at the school, in a private screened area, by a team of experienced cardiac sonographers using a standardized scanning protocol. Vivid E, with a 3S 2.2-MHz transducer (GE Healthcare, Little Chalfont, United Kingdom), and M-Turbo, with a 5-1 transducer (SonoSite Inc, Bothell, WA), were used. Both of these portable echocardiographic machines permit two-dimensional imaging, color Doppler flow imaging, and spectral Doppler velocimetry. These machines are “laptop” size, not “handheld” devices. Two-dimensional and color Doppler images were obtained in standard parasternal and apical four-chamber views of left heart structures, with careful attention to record color sweeps across any mitral or aortic regurgitant jets. Pulse-wave Doppler interrogation of regurgitant jets was undertaken to assess velocity, spectral envelope, and duration through the cardiac cycle. The minimal Nyquist limit was set at >0.68 cm/sec to avoid aliasing and potential elongation of color regurgitant jets.
Valve leaflet morphology was assessed in parasternal long-axis (mitral and aortic valve) and parasternal short-axis (aortic valve) views. A variable 2.5- to 5-MHz probe was used for all studies. Height and weight were measured, and where indicated, echocardiographic measurements were interpreted as Z scores adjusted for body surface area. Digital images were electronically stored in Digital Imaging and Communications in Medicine format.
Pediatric Cardiologic Assessment and Clinical Management
Any student with abnormal results on screening echocardiography was referred to Starship Children’s Hospital, in Auckland, for evaluation by a pediatric cardiologist and detailed echocardiography using a large-platform iE33 machine (Philips Medical Systems, Andover, MA). These echocardiograms were reported by a panel of pediatric cardiologists. Two cardiologists independently assessed each echocardiogram. If their reports were discordant, a third independent assessment was sought, and the majority opinion determined case classification and clinical management. The final classification was based on the large-platform hospital echocardiogram whenever this occurred.
The reading pediatric cardiologists were blinded to the demographic backgrounds of individual children whose echocardiograms they were reporting but were aware that the echocardiograms were being reported as part of research activities.
Criteria for the Diagnosis of RHD
RHD classification was based on the 2012 evidence-based consensus WHF diagnostic criteria for RHD ( Table 1 ). By these criteria, RHD is classified as definite or borderline according to the combination of echocardiographic features of RHD (left-sided pathologic valvular regurgitation and/or characteristic morphologic changes of valve leaflets). The presence of absence of a cardiac murmur is not included in WHF RHD criteria, because of the acknowledged limited sensitivity of cardiac auscultation.
|
|
|
|
|
∗ Congenital MV anomalies must be excluded. Furthermore, inflow obstruction due to nonrheumatic mitral annular calcification must be excluded in adults.
† Combined AR and MR in high-prevalence regions and in the absence of CHD in regards is rheumatic.
‡ A regurgitant jet should be measured from the vena contracta to the last pixel of regurgitant color (blue or red).
§ AMVL thickness should be measured during diastole at full excursion. Measurement should be taken at the thickest portion of the leaflet, including focal thickening, beading, and nodularity. Measurement should be performed on a frame with maximal separation of chordae from the leaflet tissue. Valve thickness can be assessed only if the images were acquired at optimal gain settings without harmonics and with a frequency ≥ 2.0 MHz.
|| Abnormal thickening of the AMVL is age specific and defined as follows: ≥3 mm for individuals aged ≤20 years, ≥4 mm for individuals aged 21 to 40 years, and ≥5 mm for individuals aged >40 years. Valve thickness measurements obtained using harmonic imaging should be cautiously interpreted, and a thickness up to 4 mm should be considered normal in those aged ≤20 years.
¶ Restricted leaflet motion of either the AMVL or the PMVL is usually the result of chordal shortening or fusion, commisural fusion, or leaflet thickening.
Regurgitation was graded according to severity. Physiologic regurgitation was differentiated from pathologic regurgitation according to all the criteria listed in Table 1 . Mitral valve (MV) closing volume was differentiated from physiologic-grade MR if the regurgitant jet had a low-velocity color mosaic, did not extend beyond the valve leaflets in systole, and was seen in only one plane. An MV closing volume was thus classified as normal.
Statistical Analysis
Standardized data collection forms were used. Results were entered in an Access database (Microsoft Corporation, Redmond, WA) and analyzed using SAS version 9.1.3 (SAS Institute Inc, Cary, NC). For qualitative variables, proportions along with 95% CI were calculated (the calculator used to calculate 95% CIs and prevalence ratio was downloaded from http://ww.pedro.org.au/wp-content/uploads/CIcalculator.xls ).
Methods
Study Design and Participants
Children were selected from a school community in a high–socioeconomic status urban area where no cases of acute rheumatic fever (ARF) had occurred for >10 years (Diana Lennon, Regional Rheumatic Fever Register coordinator, personal communication). The demographic makeup of the school population was predominantly Caucasian/New Zealand European (72%). Twenty-two percent were Asian and 4% were Polynesian (New Zealand Maori and Pacific Peoples).
Ten- to 12-year-olds were targeted, an age group comparable with that used in a screening study using portable echocardiography conducted in 2007 and 2008 in South Auckland, a New Zealand community with a high incidence of ARF. In this community, the ethnic makeup is predominantly New Zealand Maori and Pacific Peoples, but the key determinant of ARF and RHD burden is socioeconomic deprivation. We targeted 10- to 12-year-olds because this is the peak incidence period for ARF and also because in the New Zealand health and education system, this age group was most readily accessible for a population-based screening approach.
Ethical approval for the study was obtained from the Regional Ethics Committee.
Educational sessions were conducted by the study nurse in school classrooms, which included explanation about the process of undergoing echocardiography. Information booklets were distributed to parents and caregivers, and written informed consent was obtained from all participants’ parents or caregivers.
A sample size of 400 was planned to detect a minimum 5% difference in the observed rate of isolated mild mitral regurgitation (MR) between high-incidence and low-incidence ARF populations, assuming that the prevalence of RHD was 3% in the high-risk group and 0.1% in the low-risk group and that pathologic-grade MR was present in 10% of high-risk students. These estimates were based on analysis of data from a previous RHD screening study conducted in South Auckland, a high-incidence ARF population, in 2007 and 2008.
Four hundred dix of 587 eligible students (69%) consented. Ten consenting students were not screened, because of school absence. Of the 396 children screened, 190 (48%) were female.
School Screening Procedures
Echocardiography was conducted at the school, in a private screened area, by a team of experienced cardiac sonographers using a standardized scanning protocol. Vivid E, with a 3S 2.2-MHz transducer (GE Healthcare, Little Chalfont, United Kingdom), and M-Turbo, with a 5-1 transducer (SonoSite Inc, Bothell, WA), were used. Both of these portable echocardiographic machines permit two-dimensional imaging, color Doppler flow imaging, and spectral Doppler velocimetry. These machines are “laptop” size, not “handheld” devices. Two-dimensional and color Doppler images were obtained in standard parasternal and apical four-chamber views of left heart structures, with careful attention to record color sweeps across any mitral or aortic regurgitant jets. Pulse-wave Doppler interrogation of regurgitant jets was undertaken to assess velocity, spectral envelope, and duration through the cardiac cycle. The minimal Nyquist limit was set at >0.68 cm/sec to avoid aliasing and potential elongation of color regurgitant jets.
Valve leaflet morphology was assessed in parasternal long-axis (mitral and aortic valve) and parasternal short-axis (aortic valve) views. A variable 2.5- to 5-MHz probe was used for all studies. Height and weight were measured, and where indicated, echocardiographic measurements were interpreted as Z scores adjusted for body surface area. Digital images were electronically stored in Digital Imaging and Communications in Medicine format.
Pediatric Cardiologic Assessment and Clinical Management
Any student with abnormal results on screening echocardiography was referred to Starship Children’s Hospital, in Auckland, for evaluation by a pediatric cardiologist and detailed echocardiography using a large-platform iE33 machine (Philips Medical Systems, Andover, MA). These echocardiograms were reported by a panel of pediatric cardiologists. Two cardiologists independently assessed each echocardiogram. If their reports were discordant, a third independent assessment was sought, and the majority opinion determined case classification and clinical management. The final classification was based on the large-platform hospital echocardiogram whenever this occurred.
The reading pediatric cardiologists were blinded to the demographic backgrounds of individual children whose echocardiograms they were reporting but were aware that the echocardiograms were being reported as part of research activities.
Criteria for the Diagnosis of RHD
RHD classification was based on the 2012 evidence-based consensus WHF diagnostic criteria for RHD ( Table 1 ). By these criteria, RHD is classified as definite or borderline according to the combination of echocardiographic features of RHD (left-sided pathologic valvular regurgitation and/or characteristic morphologic changes of valve leaflets). The presence of absence of a cardiac murmur is not included in WHF RHD criteria, because of the acknowledged limited sensitivity of cardiac auscultation.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
