Background Cardiac murmurs are common in the neonatal period and in early infancy. Once detected, they cause considerable anxiety, both to parents and doctors. The discriminating value of a murmur indicating an underlying cardiac condition is not clearly known.

Aims To evaluate the reliability of a murmur in the detection of an underlying cardiac abnormality.

Methods The neonatal services at this level 3 unit, have a policy of performing echocardiograms for all murmurs detected during the newborn period or at the 6 weeks check. The results of echocardiograms are entered on a database. This database was queried from 1 September 2003 to 30 August 2009 to extract the results for murmurs and thus to establish the sensitivity, specificity, the positive (PPV) and negative predictive values (NPV) of a murmur to detect an underlying cardiac condition.

Results A total of 633 babies underwent echocardiogram because of murmurs during this period. They included 502 (79%) babies detected to have a murmur at the newborn period and 131 (21%) babies found to have a murmur at the 6 week check. Echocardiograms were performed between 0–75 days of age at a median of 25 days. Of the 633 babies, 390 (61.6%) had an audible murmur at the time of the echocardiogram. Of these, 29 (7%) were found to have no abnormality and 361 (93%) were found to have either a major or minor abnormality that could explain the murmur. Minor abnormalities included branch pulmonary artery stenosis, small arterial duct or minor valvular regurgitations. Of the 243 babies without murmurs at the time of the echocardiogram, in 219 (90%) cases the echocardiogram was normal and in the remaining 24 (10%) an abnormality was detected. The sensitivity and specificity of a murmur to predict an abnormality on echocardiogram was 93.8% and 88.3%, respectively. The PPV and NPV were 0.93 and 0.9, respectively.

Conclusions In babies and very young infants, murmurs fairly accurately predict an underlying abnormality. The authors found that very few babies with murmurs had normal echocardiograms, though not all the abnormalities were of clinical significance. The reason to continue doing echocardiograms for murmurs in early infancy is justified.