Background and Aims To identify the significance of the detection of a heart murmur on routine examination in asymptomatic neonates, including those hospitalised in the neonatal intensive care unit.

Methods The results of transthoracic echocardiograms performed from 1 June 2006 to 31 January 2007 in asymptomatic neonates aged up to 28 days were analysed. Echocardiographic studies were divided into three categories: normal cardiac anatomy, abnormal cardiac anatomy and functional abnormalities (patent ovale foramen, patent arterial duct, peripheral pulmonary artery stenosis, tricuspid/mitral regurgitation). All patients with abnormal echocardiograms were followed up in clinic, were managed appropriately and outcome data were collected prospectively. A total of 169 neonates were examined at a median age of 7 days (range 1–28 days).

Results Normal anatomy was found in 25 neonates (14.8%), functional abnormalities in 64 (37.9%), whereas 80 (47.3%) had abnormal echocardiograms. Ventricular septal defect was found in 51, atrial septal defect in 18 and pulmonary valve stenosis in five. Two neonates had aortic valve stenosis, one tetralogy of Fallot, one atrioventricular septal defect, one dilated cardiomyopathy and one term neonate had a persistently patent arterial duct requiring ligation. Significant heart disease defined as the need for medical (n  =  6) or surgical (n  =  5) therapy was found in 11 neonates, representing 6.5% of those referred for a murmur and 13.6% of those with abnormal echocardiograms.

Conclusions Almost half of asymptomatic neonates referred for echocardiography have structural heart disease. The presence of a heart murmur may be the first sign of significant heart disease even in the absence of associated symptoms.