Results

During the study period, 7763 babies were live born at the hospital (fig 1). Of these, 559 were admitted to the neonatal intensive care unit, including two babies who became symptomatic before routine newborn examination, three known to have cardiac malformations antenatally, and five premature babies who were diagnosed during their stay in intensive care (other than patent ductus arteriosus associated with prematurity).

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Figure 1

Flow diagram showing progress of all infants included in the study.

Of 7204 neonates who underwent routine examination, 46 (0.6%) were found to have a murmur (fig 1). All underwent echocardiography which confirmed a cardiac malformation in 25 and a structurally normal heart with physiological findings that would account for the presence of a murmur (such as patent ductus arteriosus or mild physiological pulmonary artery branch stenosis) in eight. Thirteen babies had normal hearts. All 25 babies with cardiac malformations were asymptomatic—15 had a ventricular septal defect, three had coarctation of the aorta, one had aortic valve stenosis, two had an atrial septal defect, one had pulmonary stenosis and three had tetralogy of Fallot (table 1).

A further 32 babies from the same birth cohort presented with congenital cardiac malformations after the routine neonatal examination and before the age of 1 year (table 1). Review of the hospital records of these infants confirmed that none had had a murmur at the time of neonatal examination. This identified 25 of 67 cases (37%) of structural heart disease diagnosed during infancy. The sensitivity of the examination for detection of congenital heart disease which became apparent during infancy was 44% (95% CI 31–58%), the specificity was 99.7%, and the positive predictive value was 54% (95% CI 39–69%) (table 2). The high specificity is simply a reflection of the low prevalence in the denominator population.

Discussion

Although congenital heart disease is present at birth, there are often no signs and most babies are asymptomatic. Detection of a murmur on routine examination may be a clue to the presence of heart disease and offers the possibility of early, presymptomatic diagnosis. Auscultation is, therefore, part of routine neonatal examination and is recommended in Health for All Children.5There is, however, a widespread misconception that murmurs are common in neonates, and that most are innocent or “physiological.” This may explain why there seems to be reluctance to make early referral for definitive diagnosis of heart disease.22

Most neonatal examinations in the United Kingdom are performed by senior house officers who may see up to 20 babies a day, in conditions that are not ideal for auscultation. Given these limitations it is not surprising that the prevalence of murmurs in this study is less than in previous reports. However, this study does reflect real life and its methodology did not change the system it studied. The prevalence of murmurs is consistent with the only previous published study relying on junior medical staff for detection of murmurs.18 We found that murmurs were detected in 0.6% of babies undergoing routine examination. Fifty four per cent of babies with murmurs had a structural cardiovascular malformation. Most importantly, 9% of babies with murmurs required early cardiac surgery and were detected before they became symptomatic. This fact, if nothing else, would support the proposition that all babies with murmurs should undergo early paediatric cardiological assessment.

Early assessment of murmurs has been recommended,23 but does not always happen. Abu-Harb et al found that 10 of 26 babies with obstructive left heart malformations who had been sent home, despite a murmur at neonatal examination, presented in heart failure before six weeks of age.6 Similarly, Beebeet al found that 57% of neonates dying from cardiovascular malformations after discharge from hospital had had a murmur before discharge.24 Thus given that murmurs are rare, and that many are a clue to the presence of asymptomatic heart disease, it seems appropriate to refer all such babies for early definitive diagnosis.

In this study the detection of a murmur at routine neonatal examination led to the diagnosis of 37% of all cases of congenital heart disease presenting in infancy. Another 15% presented before examination while 48% had no murmur and were diagnosed later in infancy. Routine neonatal examination thus has a sensitivity of 44% and the presence of a murmur has a positive predictive value of 54%. Ascertainment of heart disease was limited to infancy to ensure consistency with the methodology of other recent epidemiological studies.1-3 22 Although neonatal auscultation does not perform particularly well as a screening test, it still offers the only real opportunity of early detection of heart disease. It should, however, be more widely recognised that about half of babies with congenital heart disease will have no signs when examined soon after birth. The low prevalence of murmurs in this study does not mean that murmurs went undetected, but rather that potentially serious heart disease may produce no physical signs early in life. Even in studies with a higher prevalence of murmurs there was no significantly greater detection of heart disease.19

The birth prevalence of congenital heart disease diagnosed in infancy in this study (9.3 per 1000 life births) is higher than in most large series.1-4 This may be explained by a high prevalence of small ventricular septal defects as a result of the easy availability of early echocardiography. Two recent studies using neonatal echocardiography found a prevalence of ventricular septal defect as high as 20 and 53 per 1000 live births.25 26 In both studies most babies were asymptomatic and most defects were small with early spontaneous closure rates of 76 and 89%, respectively.

This study has shown that a prevalence of murmurs of six in 1000 babies undergoing routine neonatal examination by junior paediatricians. About half of murmurs were due to underlying structural cardiac malformation and this examination led to recognition of 37% of all heart disease diagnosed in infancy. Identification and treatment of heart disease before development of symptoms offers the prospect of an improved outcome. Early referral of all asymptomatic babies with murmurs is recommended. The absence of a murmur does not exclude the presence of potentially serious heart disease.