|Year : 2014 | Volume
| Issue : 2 | Page : 74-79
Clinical screening for heart disease in apparently healthy Nigerian school children
CS Yilgwan, OO Ige, F Bode-Thomas
Department of Paediatrics, University of Jos, Jos University Teaching Hospital, Jos, Nigeria
|Date of Web Publication||3-Oct-2014|
Department of Paediatrics, University of Jos, Jos University Teaching Hospital, PMB 2076, Jos
Source of Support: None, Conflict of Interest: None
Background: Heart diseases of childhood are of public health importance, especially in developing countries. Community-based studies are important in ascertaining the burden of disease. We set out to clinically evaluate the prevalence of heart disease among primary school children in Hwolshe electoral Ward, Jos, Plateau State.
Subjects and Methods: A total of 418 primary school pupils were selected by multistage sampling from three schools in Hwolshe ward of Jos South Local Government Area, Plateau State. They were studied for the prevalence of heart disease using clinical examination, followed by chest radiography, electrocardiography and echocardiography (echo) in those with clinical signs of heart disease.
Results: The 418 subjects were aged 6-12 (mean 9.0 ± 1.95) years. 252 (55.5%) were girls. Significant tachycardia and pulse irregularity were present in 1 (0.24%) and 3 (0.72%) children respectively. None had hypertension - according to the seventh Joint National Committee criteria. 4 (0.96%) had audible murmurs of which 3 (0.72%) were pathologic. These three subjects were subsequently confirmed by echo to have congenital heart disease (CHD) - two ventricular septal defects and one atrial septal defect. The heart disease prevalence was therefore, 0.72%. All three identified cases of CHD had associated cardiac dysrhythmias: Wandering atrial pacemaker, first degree heart block, and incomplete right bundle branch block, respectively. No case of rheumatic heart disease was identified.
Conclusions: Prevalence of heart disease by clinical screening in Jos South school children is approximately 0.72%. Careful cardiac auscultation as part of compulsory health screening at primary school entry and exit will help detect asymptomatic children with heart disease and facilitate treatment before the onset of complications.
Keywords: Clinical screening, heart disease prevalence, primary school children
|How to cite this article:|
Yilgwan C S, Ige O O, Bode-Thomas F. Clinical screening for heart disease in apparently healthy Nigerian school children. Nig J Cardiol 2014;11:74-9
|How to cite this URL:|
Yilgwan C S, Ige O O, Bode-Thomas F. Clinical screening for heart disease in apparently healthy Nigerian school children. Nig J Cardiol [serial online] 2014 [cited 2019 Dec 10];11:74-9. Available from: http://www.nigjcardiol.org/text.asp?2014/11/2/74/142085
| Introduction|| |
Heart diseases significantly contribute to the health burden of children in both developed and developing countries. , Although the overall prevalence of structural heart diseases (SHD) in developing countries is unknown; it is generally accepted that congenital heart diseases (CHD) account for 8-12/1000 live births, and that they have the greatest effect on childhood mortality and morbidity among all congenital anomalies. , Acquired heart diseases (AHD) are also a major public health problem in developing countries, especially in Africa where the epidemiological factors responsible for many AHD are still prevalent. , The major determinants of AHD in children such as poverty, malnutrition, overcrowding, poor housing, and poor or uncoordinated healthcare, are all present in Nigeria. ,,
Unsuspected heart disease has been demonstrated to be a major cause of sudden death in school children, especially where routine screening is not the norm. , Sudden cardiac death could result from diseases such as cardiomyopathies, CHD, and arrhythmias (primary or secondarily generated arrhythmias from CHD or AHD). , Screening programs have therefore been incorporated into the school health services of some countries as a means of early detection of lesions with potential of impacting negatively on the health and by extension the school performance of children.  In Japan for instance, children in their first year of elementary and junior high schools are required by law to be screened for heart disease as part of the school health program.  This is because of the high incidence of sudden death observed in school children engaged in competitive sports. A further benefit is the chance of detection of heart diseases that might only become symptomatic in adulthood. For example, delayed diagnosis and treatment of atrial septal defect (ASD) could result in such complications as congestive cardiac failure (CCF) and Eisenmenger syndrome, while its repair at an older age is associated with higher surgical risk or higher risk of an inoperable lesion. 
No such policy exists in Nigeria and many other developing countries. Only two Nigerian studies have evaluated the prevalence of heart disease in school children and both focused on rheumatic fever (RF) and/or rheumatic heart disease (RHD). Ogunbi et al. in 1978  found a RHD prevalence of 0.08% among Lagos school children, while Sadoh et al. in 2013  reported a prevalence of 0.34% from Benin City. No Nigerian study has reported on the prevalence of CHD among school children.
We therefore set out to clinically evaluate the prevalence of heart disease (congenital or acquired) in primary school children in Hwolshe electoral Ward of Jos South Local Government Area (LGA), Plateau State, Nigeria, with a view to detecting previously undiagnosed heart disease and offering treatment where possible. This may present the only opportunity for detecting less severe lesions, but which have potential for complications or progression if appropriate measures are not taken early enough.
| Subjects and methods|| |
This cross-sectional survey was done among school children aged 6-12 years in Hwolshe, Jos South LGA, between December 2009 and March 2010. The ward has six primary schools (two private and four public schools) and an estimated total school enrolment of 4000. The schools were selected proportionately by multistage sampling. The primary schools were first classified into public and private schools after which simple balloting was used to select three schools, two public, and one private school. The registers of the selected schools were then used as the sampling frames to recruit subjects into the study. Proportionate allocation was given to each class depending on the population of school children in each class (from primary one to six). For lack of information on a similar published study from Nigeria or the West African sub region (as at the commencement of study) for a guide on sample size, 50% prevalence was assumed which gave the largest sample size for the chosen error margin of 0.05. The minimum sample size was thus calculated to be 381.  After making an allowance of 10% for possible nonresponders, 420 pupils comprising 220 pupils from the two public schools and 200 from the private school were invited to participate in the study. 418 children were eventually enrolled in the study because their parents gave informed consent.
Written approval was obtained from the Plateau State Primary Education Board and the Jos South Local Government Education Authority. Furthermore, each school Headmaster was personally informed and given the written approval obtained from the overseeing authorities. An information sheet on the nature and procedures of the study was sent along with a written consent form to parents of all the selected children. Subsequently, informed written consent was obtained from each parent or guardian willing to let their ward participate in the study. The study protocol was approved by the Ethics Committee of the Jos University Teaching Hospital, Jos, Nigeria.
A self-administered questionnaire was used in obtaining basic information from the parents. These included: Personal biodata, symptoms of cardiac disease if any, drug history, past medical history, social and family history. Each subject's socio-economic class was determined using the criteria developed by Olusanya et al. 
All enrolled children underwent general physical examination and focused cardiovascular examination, including careful cardiac auscultation in a quiet room by three residents in pediatrics with confirmation by one of the investigators (CSY) so as to increase the degree of specificity. Pupils with abnormal cardiovascular findings were further assessed by means of chest radiography (chest X-ray [CXR]), electrocardiography (ECG) and two-dimensional color flow echocardiography (echo). All echo were performed according to the guidelines of the American Society of Echocardiography, using a Logiq 5 Expert ultrasound system (model number 5149094, GE Medical Systems, Tokyo, Japan, 2006). The ECG and chest radiographs were interpreted according to standard methods. ,,
Data analysis was done using Epi Info Version 3.5.2 (CDC, Atlanta, Georgia, USA). P < 0.05 were considered as statistically significant.
| Results|| |
General characteristics of the subjects
A total of 418 pupils aged from 6 to 12 years participated in the study of which 232 (55.5%) were females. The mean age was 9.0 ± 1.95 years and did not differ significantly between males and females (8.9 ± 1.82 years and 9.1 ± 2.05 years, respectively) (P = 0.13). The girls were taller and heavier, but only their weight was significantly higher than that of their male counterparts [Table 1]. The two sexes were also similar with respect to their mean pulse and respiratory rates, and their systolic and diastolic blood pressures [Table 1].
|Table 1: General characteristics of 418 primary school children screened for heart disease|
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Only 1 (0.24%) of the 418 children examined had significant tachycardia (≥95 th percentile for age and sex)  while 3 (0.72%) had an irregular pulse. None had hypertension using the seventh Joint National Committee  criteria, while 4 (0.96%) had audible murmurs. However, only 3 (0.72%) of these murmurs were considered pathologic. The fourth child had an associated febrile illness and a murmur that apart from satisfying the clinical criteria for an innocent murmur was no longer audible after treatment of the febrile illness.  Furthermore, his echo was found to be completely normal.
Only one child had an abnormal CXR, consisting of: Cardiomegaly, plethoric lung fields and prominent main pulmonary artery [Figure 1]. ECG evaluation of the three children with pathologic murmurs showed incomplete right bundle branch block in one child, first degree heart block in another and a wandering atrial pacemaker in the third [Figure 2].
|Figure 1: Chest radiograph of a 9-year-old boy with atrial septal defect. Note the prominent pulmonary conus, cardiomegaly (cardio-thoracic ratio = 0.68), right atrial enlargement and bilaterally increased vascular markings|
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|Figure 2: Electrocardiography tracing of a 6-year-old girl with ventricular septal defect. Note the variable heart rate (71 to 115/min, varying P-wave morphology and duration, and beat to beat variation in PR-interval - all pointing to a wandering atrial pacemaker|
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Further evaluation by means of echo [Table 2] showed that all three children with pathologic heart murmurs had congenital cardiac abnormalities. Two of these, both females, aged 6 and 8 years respectively had small perimembranous ventricular septal defects (VSD) that were not hemodynamically significant [Figure 3]. The third, a 9-year-old boy, was found to have a large (1.5 cm) secundum type ASD [Figure 4]. Other observed echo abnormalities in this child include dilatation of the right heart chambers and moderate tricuspid incompetence with peak gradient of 46 mm Hg [Figure 5]. The prevalence of heart disease and CHD in this study was therefore 0.72%. No case of AHD, including RHD was identified.
|Figure 3: Two-dimensional echocardiogram of an 8-year-old girl, showing a small perimembranous ventricular septal defect measuring 0.45 cm|
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|Figure 4: Echocardiogram of the subject with atrial septal defect (ASD) showing dilatation of right heart chambers and ASD (arrow) on two-dimensional echo (la = left atrium, ra = right atrium, rv = right ventricle, lv = left ventricle)|
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|Figure 5: Echocardiogram of the subject with atrial septal defect showing tricuspid regurgitation with peak velocity of 3.4 m/s and peak pressure gradient of 46.16 mm Hg|
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|Table 2: Summary of findings in three school children with heart disease|
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| Discussion|| |
The prevalence of heart disease in school going children varies considerably from region to region. These variations depend partly on the methodology used. In the present study, the prevalence of heart disease diagnosed primarily by clinical examination was found to be 0.72% (approximately 7/1000), similar to that reported by two previous similar studies from South Africa (0.7%) and Egypt (0.6%), respectively. , In contrast to these studies however, we found only CHD but no case of RHD. Anabwani and Bonhoeffer  also identified both RHD and CHD among school children in Kenya.
Our findings are also in contrast to the two previous studies of heart disease in Nigerian school children which found RHD prevalence's of 0.08% and 0.34% of school children in Lagos and Benin City respectively. , The notable absence of RHD in the present study is unusual considering the fact that the age group studied is within the peak age incidence of Group A β hemolytic streptococcal throat infection and RF. Besides, the risk factors for RF such as poor housing, overcrowding and poverty are still rife in the country.  Recent hospital-based studies suggest a continuing high prevalence of RHD in the northern parts of Nigeria but declining prevalence in the South. ,, This has been buttressed by the report a recent clinical screening of 1764 primary school children in the South of Nigeria, and which demonstrated a very low prevalence of RHD.  It remains to be seen whether these observations will be borne out by future echo screening studies.
One possible reason for the absence of RHD in our study could be the relatively small sample size and the type of screening method used.  Although the Egyptian study utilized similar methodology, the larger sample size (>8000) and the inclusion of absentee children (through home visits) are likely to have increased the chances of identifying children with RHD. 
Despite the limitation, our heart disease prevalence rate of 0.72% is much higher than the 0.4% reported from Pakistan by Abbasi et al.,  who found equal proportions of CHD and RHD. Although that study included both primary and junior secondary school pupils, the exclusion of girls aged 14 years and above, and those with advanced Tanner stage maturity (due to religious restrictions) could explain their lower prevalence - especially since RHD is known to be more prevalent in girls.
Anabwani and Bonhoeffer  and Misra et al.  have reported much higher prevalence rates (2.88% and 1.3% from Kenyan and Indian school children, respectively) and these authors utilized echo as their primary screening tools - in contrast to the present study, which was based primarily on clinical examination, with echo only used for confirmation. Marijon et al.  in an epidemiologic study of RHD in 4000 Mozambican and Cambodian school children demonstrated that echo is 10 times more sensitive than clinical screening in identifying structural heart lesions (in this case subclinical RHD). This has subsequently been confirmed by other studies. ,
Another reason why our study may have underestimated the prevalence of heart disease is that we sampled only pupils who were present in school and so might have missed pupils with significant long-standing or severe illness. These sick children are often absent, and even likely to have dropped out-of-school.  Over 30 years ago, Jaiyesimi  documented that up to 67% of Nigerian children with RHD dropped out-of-school, crippling their ability to realize their full potential. For those who did not drop out, poor school performance due to frequent absenteeism and recurrent hospitalization were common. Other researchers have tried to overcome this limitation by home visits to absentee children, including those listed as having heart disease in school records.  Therefore, although the present survey provides some information on the prevalence of heart disease in Nigerian school children, a larger community survey preferably using echo which is a much more sensitive screening method would be very helpful, especially if out-of-school children are also included since our primary school enrolment rate is low. ,
All the children diagnosed with heart disease in this study were being identified for the first time. The boy with the ASD had had recurrent cough and fast breathing and was managed as a case of asthma, with no improvement. Children with acyanotic CHD are often mis-diagnosed as asthma as both conditions often present with recurrent cough and breathing difficulties. Furthermore, many health workers lack basic skills of cardiovascular examination and have a low index of suspicion for heart disease in children, leading to mis-diagnoses and late referrals. Many parents do not visit qualified practitioners, but would rather patronize chemist and pharmacy shops because of limited financial resources and the poorly regulated medical practice.  Other families are unaware of their children's illness or its severity because they lack access to proper health information. Thus, many parents/care givers of children with heart diseases seek qualified medical help only during emergencies. All these further compound such children's problems and often delay the diagnosis until complications have set in.
Two out of three children diagnosed with CHD had small VSDs that were not hemodynamically significant. Whether these were originally larger defects that had reduced in size over time is a subject for debate. However, these pupils had never been symptomatic. Most studies done in school children had demonstrated a predominance of VSD over other types of CHD.  VSD is known to be the commonest CHD the world over with a high potential of spontaneous closure as the child grows older.  Although the VSDs detected in this study were not hemodynamically significant, the two girls with VSD are at a higher risk of developing infective endocarditis (which is higher with smaller lesions) than their peers.  This further underscores the importance of school screening and the need for education and prophylaxis against bacterial endocarditis for those at risk.
In contrast, the ASD detected was large sized with associated dilatation of right heart chambers and development of tricuspid incompetence from dilatation of the valve ring. The child eventually had surgical closure of the ASD at the age of 10 years. ASD are often asymptomatic in infancy and are usually repaired between 2 and 4 years of age.  There is no obvious advantage in delaying repair beyond the 4 th birthday as that could lead to long-standing volume overload on the right atrium and ventricle, and predispose to complications such as arrhythmias, CCF and Eisenmenger syndrome later in life.  Fortunately for this boy, his lesion was discovered in the course of this screening exercise and was surgically corrected before the onset of these complications. This case exemplifies the role of school health screening for heart disease in the early diagnosis and possible treatment of heart lesions to prevent continuation into adulthood and the setting in of complications.
Each of the three children found to have SHD had an associated dysrhythmia. These associations underscore the relevance of ECG as an adjunctive investigation tool in the management of children with SHD. Rhythm disorders have been shown to predispose to sudden cardiac events especially in children with asymptomatic structural heart defects like the ones identified in the course of the present study. ,
| Conclusion|| |
Our study underscores the importance of school heart screening in asymptomatic children. We advocate for the introduction of cardiac examination or at least cardiac auscultation as part of school health screening at primary school entry and at exit. We believe that this will help detect asymptomatic children having lesions with a potential for complications later in life. It will also help to reduce the burden and morbidity associated with undetected heart disease in school age children. It will entail raising awareness of heart disease among health workers especially those involved in the school health program. We also recommend larger community-based echo screening studies including out-of-school children so as to ascertain the true burden of pediatric heart diseases in our community.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]