FREQUENCY AND SIGNIFICANCE OF CARDIAC MURMURS IN THE FIRST YEAR OF LIFE

The frequency of cardiac murmurs in early infancy has been studied in a large series of unselected infants. In the immediate postnatal examination, a murmur was heard in 1.7 per cent. With repeated examinations, however, at 6 and at 12 months of age, the proportion of infants in whom a cardiac murmur was heard at some time rose to 7.0 per cent of 5,017 full-term singlebirth infants and to 9.9 per cent of 364 premature single-birth infants. Non-white infants had a significantly higher prevalence of murmurs than did white infants at both the 6 and 12 month examinations. Of the 71 full-term infants who had murmurs at the birth examination and were re-examined at both 6 and 12 months, 49 (69 per cent) had no murmurs at either of the later examinations. Of the 150 full-term infants who had murmurs heard for the first time at 6 months and were re-examined at 12 months, 90 (60 per cent) had no murmur at the 12-month examination. Of the total number of 353 murmurs heard in full-term infants, 166 were ultimately interpreted to be functional, and 25 to be organic murmurs. The remaining 162 were inconstantly present, and were probably all functional murmurs. In our experience, a murmur heard at birth carries a 1:12 probability of congenital heart disease; if it is again heard at 6 months, this chance is 1:3; and if the murmur persists to 12 months, the chance is 3:5 that congenital heart disease is present. When a murmur is first heard at 6 months, and persists until 12 months, the probability of congenital heart disease is 1:7; and when a murmur is first heard at 12 months, the probability falls to 1:50. Premature infants were found to be similar to full-term infants in all respects, insofar as their small numbers made comparisons possible. Finally, the relative rarity of cardiac murmurs in the newborn period has been demonstrated once more.