Article Text
Abstract
Objective To determine the prevalence and clinical significance of heart murmurs detected during heart disease screening among apparently healthy schoolchildren.
Design Cross-sectional study.
Setting 32 elementary schools in Dongguan City of China.
Patients 81 213 schoolchildren aged 5–13 years from different elementary schools.
Main outcome measures The prevalence and clinical significance of heart murmurs among schoolchildren.
Results Murmurs were detected in 2193 schoolchildren (2.7%), of whom 215 had a structural heart disease (SHD). Of patients who had SHD, 198 children had congenital heart disease (CHD), 12 had mitral valve prolapse and 5 had rheumatic heart disease. In patients who had CHD, the most common diagnosis was a ventricular septal defect. With respect to sex, SHDs were equally distributed between males and females. Of the schoolchildren who had a murmur, 1797 (81.9%) had a murmur with the loudness of grade 1 or 2 and 396 (18.1%) had a murmur with the loudness of grades 3–6. The prevalence of SHD fell significantly with increasing age.
Conclusions The study suggested that apparently healthy schoolchildren with grade ≤2 cardiac murmurs are least likely to have underlying SHD, especially in those aged ≥10 years. However, echocardiography should be performed in younger schoolchildren with cardiac murmur grade ≥3.
- Cardiology
- Congenital Abnorm
- Screening
- Epidemiology
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What is already known on this topic?
Cardiac murmurs are common in asymptomatic apparently healthy schoolchildren.
Sending all murmurs for echocardiographic examinations is a poor use of resources.
The prevalence and clinical significance of cardiac murmurs heard during large-scale heart disease screening of schoolchildren are unknown.
What this study adds?
Our study can provide data to develop the evidence-based referral decision.
We should decrease the number of unneeded echocardiographic examinations in children with murmur grades ≤2 and older than 10 years.
Schoolchildren with cardiac murmur grades ≥3 and younger than 10 years of age should refer to the echocardiographic examinations.
Introduction
Cardiac murmurs are common in asymptomatic children and represent the most frequent reason for referral to a cardiologist.1 ,2 The reported prevalence of cardiac murmurs in apparently healthy children varies widely from 5% to 80% of screened population, depending on the group studied.3 ,4 The majority of cardiac murmurs in infants and children are normal or innocent.5 Most reports of the prevalence of cardiac murmurs come from early studies,6 ,7 pre-dating echocardiography and interventional cardiology, which have improved the accuracy of diagnosis of structural heart disease (SHD).8 There is little in published findings in the large-scale epidemiology survey that correlates cardiac murmurs with confirmed heart disease in the schoolchildren.
The importance of early detection of heart disease in asymptomatic schoolchildren has been adequately emphasised.9 ,10 Although most cardiac murmurs are innocent, a murmur may be the sole manifestation of serious heart disease in the schoolchildren.1 ,11 Up to 6 in every 1000 children born will have congenital heart disease (CHD) that requires cardiology intervention.12 Many of these conditions are first diagnosed following detection of a heart murmur incidentally. Identifying this small group of children is important as CHD can cause significant morbidity and may even lead to death without prompt and appropriate treatment.13 A number of studies have showed that there is no obvious advantage in delaying treatment of SHD beyond the teenage years and, in fact, such delay may increase the risk of diseases, such as supraventricular tachycardia, pulmonary hypertension and ventricular dysfunction.14
Numerous studies have identified clinical predictors of pathological murmurs,11 ,15 but the absence of abnormal findings does not always guarantee that the diagnosis of SHD can be excluded.11 ,16 Echocardiography remains the gold standard of formal diagnosis. Echocardiography is a highly accurate method for diagnosing and characterising SHD. The advent of high-quality, portable echocardiography systems means that it is possible to have on-site confirmation of the cause of murmurs in school-aged children.
This prospective study was undertaken to determine the prevalence and clinical significance of cardiac murmurs heard during heart disease screening of schoolchildren and the contribution of the heart disease screening to detection of SHD in school-aged children.
Methods
This was a cross-sectional survey of Dongguan primary-school-aged children conducted between November 2011 and November 2012. We aimed to survey all students attending every elementary school in Dongguan City, which is located in southern China. This study is part of the heart disease screening programme supported by the government of Dongguan City. Eight cardiologists and three echocardiographists, having completed subspecialty training in cardiology or echocardiography with a minimum of 5-year clinical experience, were recruited from the Fifth People’s Hospital of Dongguan to carry out this investigation.
All the students were given a questionnaire to be completed at home by their parents or guardians. The questionnaire included questions on cardiovascular and valvular disease risk factors, as well as any previous cardiovascular symptoms.
All the students underwent a detailed cardiovascular examination performed by a cardiologist (see box 1). The examinations were performed in a silent classroom by auscultation of mitral focus, pulmonary focus, aortic focus and tricuspid focus. Children with a definite or possible cardiac murmur were re-examined by a cardiologist who performed an echocardiogram in another silent classroom. A GE Vivid i portable ultrasound machine (General Electric, USA) was used, with either a 3.5 or 5.0 MHz phased array transducer. The echocardiogram permitted on-site confirmation either to reassure parents that the heart was normal or which heart disease was detected, to explain the nature of the abnormality. In children who needed, a catheter angiography was performed.
Comprehensive clinical assessment of cardiac murmur
History
Symptoms: shortness of breath, chest pain, syncope, palpitation, etc.
Past medical history: history of rheumatic fever, previous cardiac surgery
Family history: any history in the family with known structural heart disease or sudden death
Physical examination
General observation: cyanosis, dyspnoea, oedema, anaemia, scars of previous cardiac surgery, Osler's nodes, Janeway lesions, finger clubbing, etc.
Cardiovascular system: pulse, blood pressure, carotid pulse, jugular veins, precordial palpation, heart auscultation (include dynamic auscultation, such as bedside manoeuvres)
Respiratory system: pulmonary oedema, respiratory tract infection (high-output state), etc.
Gastrointestinal system: hepatomegaly, ascites, splenomegaly, etc.
Extremities: oedema
The characteristics of the murmurs were classified at the point of maximal intensity. Four principal areas (tricuspid area, pulmonary area, mitral area and aortic area) were auscultated with both the bell and the diaphragm of the stethoscope with the children in the supine, sitting and standing positions. However, we were not constrained by these areas; we also listened between and beyond these four areas. Loudness of the cardiac murmurs was graded from 1 to 6 according to Levine.17 For analysis, murmurs were classified as soft (grade 1 or 2) or loud (grades 3–6). Timing of murmurs was classified as systolic murmurs, diastolic murmurs and continuous murmurs. The systolic murmurs may be classified as holosystolic murmurs, ejection murmurs, early systolic murmurs and mid-to-late systolic murmurs. Shape was categorised into crescendo, decrescendo or plateau type. Changes with the Valsalva manoeuvre and respiration were recorded. Mitral valve prolapse (MVP) is considered as an acquired heart disease in this study according to a previous report.18
A history of acute rheumatic fever (ARF) also was interrogated. The children who had a history of ARF or who had thickening and/or insufficiency of the mitral and/or an aortic valve, without unexplained reasons and determined by echocardiography, were accepted as rheumatic heart disease (RHD).
Unless otherwise stated, data are presented as percentages. The statistical analysis was performed using SPSS V.17.0 for Windows. Comparison between groups was performed using χ2 test with a significance level of p<0.05.
Results
Our study included 81 213 of 81 231 schoolchildren (99.98%) enrolled in 32 different elementary schools over a 1-year period in Dongguan City, which is located in southern China. Despite multiple visits, not all enrolled students were available because of the absences (16 schoolchildren) and the refusal to the echocardiography examination (2 schoolchildren). However, no parent or guardian refused participation. In total, 38 190 (47%) were female and 43 023 (53%) were male with the age range between 5 and 13 years.
Of the 81 213 schoolchildren who underwent cardiac examination, 2193 (2.7%) were found to have a murmur. Of the schoolchildren who had a murmur, 1797 (81.9%) had a murmur with the loudness of grade 1 or 2 and 396 (18.1%) had a murmur with the loudness of grades 3–6 (see table 1).
All the schoolchildren who had a murmur underwent echocardiography, which confirmed an SHD in 215. The murmurs determined in 1978 schoolchildren were evaluated as innocent murmurs. Of the schoolchildren who had an SHD, 198 had a CHD, 12 had an MVP and 5 had an RHD (see table 2). With respect to sex, SHDs were equally distributed between males and females (see table 2).
The prevalence of SHD fell significantly with increasing age. The prevalence of SHD in those aged 5–7 years (3.4 per 1000) is significantly higher than those aged 11–13 years (1.7 per 1000) (see table 3; the SHD prevalence of 5–7 years group compared with 11–13 years group: χ2=14.62, p<0.01).
The distribution according to age and murmur grades in the 215 schoolchildren with SHD is summarised in table 3. Thirty-five (16.3%) schoolchildren with SHD had a murmur intensity of 2/6 or less. Most schoolchildren (83.7%) with SHD had murmur grades ≥ 3. Interestingly, the types of SHD in the schoolchildren with murmur grades ≤2 were mostly (data not shown due to space constraints) clinically non-significant congenital heart defects, which are anatomically defined cardiac malformations that have no functional clinical significance. They include small ventricular septal defects and trivial aortic or pulmonary valve stenosis only detectable with echocardiography and requiring no treatment.
Discussion
To the best of our knowledge, this is the largest epidemiological survey of the prevalence and clinical significance of cardiac murmurs in schoolchildren in China. It is a challenging work for the cardiologists to distinguish pathological murmurs from the far more common innocent murmurs accurately.2 ,19 ,20 Obviously, echocardiography remains the gold standard. However, screening echocardiography is not indicated for some reasons. First, echocardiography is a relatively expensive means for screening the population of schoolchildren with cardiac murmurs. Second, the current resolution of echocardiography can reveal details of cardiac function that may be physiological but interpreted as pathological, resulting in unnecessary therapy and anxiety of the schoolchildren's parents.
Sending all murmurs for echocardiographic examinations is a poor use of resources. One study has been designed to assess the cost-effectiveness of various strategies to evaluate cardiac murmurs in children. It showed that referring all children with murmurs for echocardiographic examinations detects pathological murmurs at $158 000 per additional case detected over referring all children with murmurs to a cardiologist.21 However, it is difficult to find a screening method detecting the minority with heart disease without wasting investigative energy and resources on the healthy majority. So when should we refer a child with a murmur to an echocardiographic evaluation? In other words, which part of children with cardiac murmurs should we refer to for echocardiographic evaluation? Our study can provide data to develop the evidence-based referral decision.
In our study, about 9 in 10 schoolchildren who were referred for evaluation of a murmur had a normal echocardiographic examination. Among the children with a murmur with the loudness of grade 1 or 2, most of them (97.4%) had an innocent murmur. Besides, the decreasing prevalence of CHD with increasing age was found in our study, which was also consistent with many other studies.11 ,22 ,23 This indicates that we should decrease the number of unneeded echocardiographic examinations in children with murmur grades ≤2 and with the age older than 10 years.
It shows that about 1 in 10 schoolchildren with a cardiac murmur was found to have some form of structural cardiac malformation, increasing to almost 1 in 2 (45.5%) schoolchildren with a cardiac murmur loudness grade ≥3. Additionally respecting to the fact that the prevalence of SHD increase significantly in the schoolchildren younger than 10 years, this study suggests that cardiac murmurs in schoolchildren with the loudness of grades 3–6 and those younger than 10 years of age should raise a high index of suspicion and should refer to the echocardiographic examinations. Given the incidence of murmurs in this population, adoption of these strategies would result in considerable cost savings.
Many asymptomatic children with grade 2/6 systolic murmurs and no other cardiac physical findings need no further workup after the initial history and physical examination. In the guidelines for management of patients with valvular heart disease, the American Heart Association/American College of Cardiology task force recommended that echocardiography is not recommended for patients who have a grade 2 or softer midsystolic murmur identified as innocent or functional by an experienced observer.24 This recommendation is consistent with our result.
Although screening echocardiography is associated with a high detection rate, it still has a 5% false-positive rate and cannot diagnose all cardiac abnormalities. Some studies showed that pulmonary valve stenosis and patent ductus arteriosus are the lesions most likely to be misdiagnosed by ultrasound studies relying on imaging alone.25 ,26
We must emphasise that echocardiography should not replace the cardiovascular examination, particularly in the developing countries. As valuable as echocardiography may be, the basic cardiovascular physical examination is still the most appropriate method of screening for cardiac disease. Murmurs are important because of the marked anxiety that people have about heart disease. The physician can do great harm by transmitting uncertainty to the family. Therefore, the approach should be to assess the child's health and cardiac status by a thorough history and physical examination, with particular attention to the characteristics of the murmurs. However, if in patients with heart murmurs transthoracic echocardiography proved to be inadequate, transoesophageal echocardiography, cardiac magnetic resonance or cardiac catheterisation may be indicated for better characterisation of heart murmurs depending on the specific clinical circumstances.24
Ideally, a skilled paediatric cardiologist will be able to separate out the innocent murmurs from those arising from a structural abnormality. However, some studies have showed that diagnostic accuracy of clinical assessment of heart murmurs by office-based paediatricians is suboptimal and educational strategies are needed to improve accuracy and reduce unnecessary referrals and misdiagnosis.25 However, this subject is beyond the scope of this paper. This paper focuses on the prevalence and clinical significance of heart murmurs detected during heart disease screening among apparently healthy schoolchildren. Further studies would be discussed in the future.
Acknowledgments
We thank the patients who participated in this research. We also thank the Social Security Bureau of Dongguan and the Education Bureau of Dongguan for supporting this work.
References
Footnotes
Contributors All authors have contributed substantially to the study, reviewed the analyses, approved the final version of the manuscript and share responsibility for the results. GK, JX, YW, JW, QL, QC, FY, WL and JC conceived and designed the study, and undertook data collection. GK and YC undertook analyses. GK drafted the manuscript. JX is the guarantor of this study.
Funding This work was supported by grant from Science and Technology bureau of Dongguan (grant number 2011105102001) and grant from the National Natural Science Foundation of China (grant number 81470447).
Competing interests None declared.
Patient consent Obtained.
Ethics approval The authors assert that all procedures contributing to this work comply with the Helsinki Declaration of 1975, as revised in 2008, and has been approved by the institutional committees (the Ethics Committees of Dongguan Affiliated Hospital of Medical College of Jinan University and the Fifth People’s Hospital of Dongguan).
Provenance and peer review Not commissioned; externally peer reviewed.