Heart murmurs are common in childhood. Any murmur associated with cardiac signs or symptoms should be referred to a pediatric cardiologist for further evaluation. A benign murmur typically can be differentiated from a pathologic murmur based on its characteristics. Between 1% and 5% of newborns and infants will have a murmur, and up to 50% of those will be due to a structural defect. Congenital heart disease is the most common diagnosis in newborns and infants with a murmur, but a majority of congenital heart disease lesions diagnosed in asymptomatic infants and children will be minor and resolve with time. Although up to 50% of children will have a murmur at some time in their life, less than 30% of murmurs referred to pediatric cardiologists are pathologic. In older children, undiagnosed congenital heart disease is much less common than cardiomyopathies and acquired valvular disease, which are important causes of pathologic murmurs. Echocardiography is the preferred imaging modality for evaluating murmurs.

Case 1. JH is a 3-day-old patient seen in your clinic for a routine post-nursery visit. She has gained 20 g since discharge and a repeat transcutaneous bilirubin level is low. On examination, you note a grade 3/6 holosystolic murmur heard best at the left lower sternal border.

A murmur is the sound of turbulent blood flow heard on heart auscultation.^1,2 Turbulent blood flow may be caused by normal physiologic flow acceleration or by a structural defect. Murmurs are common in childhood. Although the prevalence of pathologic murmurs changes with age, most pediatric murmurs are benign. The clinical challenge is differentiating pathologic from benign murmurs.