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.
Up to 5% of newborns will have a murmur,3,4 and up to 50% of children and adolescents may have a murmur at some time in their life.5 Although up to 50% of newborns with murmurs may have an underlying cardiac abnormality,3,4 only 30% of children referred to pediatric cardiologists have a pathologic murmur.6
Pathologic murmurs can have many etiologies, but the differential diagnosis can be narrowed by characteristics of the murmur (eg, loud, holosystolic).1,2 Congenital heart disease (CHD) is the major cause of pathologic murmurs in infancy. Cardiomyopathies are a diverse group of diseases of the myocardium, typically inherited, that may can cause murmurs. Acquired heart disease is due to an infectious, inflammatory, ischemic, or toxic insult. An acquired heart disease that affects the valves or otherwise creates turbulent blood flow may cause a murmur.
Evaluation
The first step in evaluating a patient with a murmur is to determine if there are cardiac signs or symptoms.1 In newborns and infants, heart disease can present with cyanosis, cardiogenic shock, murmur, or heart failure. Heart failure can manifest as respiratory stress, fatigue or diaphoresis with feedings, or poor growth. In children and adolescents, cardiac disease manifests as dyspnea, chest pain with exertion, exertional syncope, heart failure, or sudden cardiac death. Any child with signs or symptoms of cardiac disease should be evaluated further in consultation with a pediatric cardiologist.7
CHARACTERIZING MURMURS
For some cardiac conditions, an asymptomatic murmur may be the only presenting sign. Characterizing the murmur may suggest a benign or pathologic etiology as certain characteristics are more common in pathologic murmurs.1 Benign murmurs tend to be soft, systolic (ie, grade 1/6 or 2/6), and musical or vibratory in nature.1,2 A moderate murmur (ie, grade 3/6) may be benign or pathologic. Pathologic murmurs are loud (ie, grade 4/6 or more), holosystolic (eg, those that begin in systole and extend into diastole, obscuring the second heart sound) and diastolic, and have an abnormal second heart sound or a click or friction rub. Murmurs with a harsh or mechanical quality should be evaluated by a pediatric cardiologist.8
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