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Am Fam Physician. 2022;105(3):250-261

Patient information: See related handout on what parents should know about heart murmurs in children, written by the authors of this article.

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial relationships.

Up to 8.6% of infants and 80% of children have a heart murmur during their early years of life. The presence of a murmur can indicate conditions ranging from no discernable pathology to acquired or congenital heart disease. In infants with a murmur, physicians should review the obstetric and family histories to detect the possibility of congenital heart pathologies. Evaluation by a pediatric cardiologist is indicated for newborns with a murmur because studies show that neonatal murmurs have higher rates of pathology than in older children, and neonatal murmur characteristics are more difficult to evaluate during examination; referral is preferred over echocardiography. All infants, with or without a murmur, should have pulse oximetry screening to detect underlying critical congenital heart disease. In older children, most murmurs are innocent and can be followed with serial examinations if there are no findings of concern. Findings in older children that warrant referral include diastolic murmurs, loud or harsh-sounding murmurs, holosystolic murmurs, murmurs that radiate to the back or neck, or signs or symptoms of cardiac disease. Referral to a pediatric cardiologist is indicated when a pathologic murmur is suspected. Electrocardiography, chest radiography, and other tests should not be reflexively performed as part of all murmur evaluations because these tests can misclassify a murmur as innocent or pathologic, and they are not cost-effective. Emerging technologies include phonocardiography interpretation of murmurs and artificial intelligence algorithms for differentiating innocent from pathologic murmurs.

Heart murmurs are a common finding in children and the most frequent cause for referral to a pediatric cardiologist.14 The lifetime incidence of murmurs in children is high, with most children experiencing a murmur. Most murmurs are transient and of minor clinical significance.5,6

RecommendationSponsoring organization
Do not repeat echocardiography in patients who are stable and asymptomatic with a murmur or click, where a previous examination revealed no significant pathology.American Society of Echocardiography

Despite the high prevalence of murmurs and the frequency with which physicians encounter them, evidence shows that physicians’ cardiac auscultation skills are suboptimal.79 In one study, physician examination had a 79.7% sensitivity and 88.5% specificity for discerning pathologic from innocent murmurs (positive predictive value = 87%; negative predictive value = 81.8%).10 However, there is variation based on specialty and training level.11,12

Heart Murmur Physiology and Terms

Murmurs result from perturbations in blood flow from pressure gradients or velocity changes that cause turbulent blood flow and vibration.1316 The vibration is transmitted through the pericardium and chest wall and into the stethoscope. When the vibratory component is strong enough, a tactile vibration on the chest wall is noticeable as a cardiac thrill.

Murmur intensity increases with increasing cardiac output and decreases in the presence of pericardial effusions, decreased cardiac output, or increases in subcutaneous tissue (e.g., obesity). The ability to hear a murmur and feel a thrill depends on the clinician’s sensory abilities.9,17,18

Innocent murmurs are commonly referred to as flow murmurs, physiologic murmurs, or functional murmurs. In contrast, pathologic murmurs are associated with congenital or acquired structural heart disease and often require medical or procedural interventions.

Incidence

Between 0.6% and 8.6% of infants who are asymptomatic with no apparent signs of a congenital syndrome have a heart murmur. Most of these murmurs are innocent; however, 37% of murmurs in infants with no apparent signs of congenital syndromes are diagnosed with congenital heart disease, and 2.5% of infants with a murmur have a critical lesion requiring procedural interventions early in life.19

Beyond infancy, innocent murmurs are more common, occurring in 20% to 80% of children.6,20 Innocent murmurs should disappear as the child transitions into adulthood.21 Pathologic murmurs beyond infancy are uncommon, with only 1% of childhood murmurs associated with structural heart disease that require intervention.2

History

INFANTS

The first step in evaluating an infant with a heart murmur is to review the obstetric and family histories. Although most congenital heart disease is not caused by a known genetic abnormality, the probability of congenital heart disease is higher in children who have siblings or other family members with congenital heart disease.22 Table 1 lists factors to consider when taking a history for an infant with a heart murmur.14,2227

Personal history
History of acute rheumatic fever, multisystem inflammatory syndrome in children, or Kawasaki disease
Family history
Congenital heart diseaseDepending on etiology, high rates within families, with siblings having increased risk of 3 to 24 times higher than the general population
Hypertrophic cardiomyopathyDepending on etiology, first-degree relatives should generally have an echocardiography screening
Sudden unexplained deathCould be a sign of undiagnosed congenital heart disease or a genetic cardiomyopathy
Genetic syndrome/association/sequence
AneuploidyTrisomy 21 associated with a variety of cardiac pathologies (endocardial cushion-related pathology)
Turner syndrome associated with aortic valve and root anomalies
Connective tissue pathologiesMarfan syndrome associated with aortic aneurysm and root dilatation
≥ 3 minor structural anomalies or one major anomaly3 minor anomalies carry a 90% risk of a major anomaly, including structural heart disease in conditions such as Noonan syndrome, Pierre Robin sequence, osteogenesis imperfecta, VACTERL association, CATCH 22 syndrome, CHARGE syndrome, and others
Inborn errors of metabolism or lysosomal storage diseasesCommon comorbidities include aortic and mitral valve disease, depending on the exact disease; phenylketonuria is strongly associated with congenital heart disease
Exposure to teratogenic medications
Lithium, valproic acid and other antiepileptic drugs; mycophenolate mofetil (Cellcept), warfarin (Coumadin), angiotensin-converting enzyme inhibitors, retinoic acid, vitamin A derivatives (not topical)U.S. Food and Drug Administration labeling contains prevalence and extent of associations that vary for each medication
Nonsteroidal anti-inflammatory drugsThird trimester exposures associated with an odds ratio of 15 for premature closure of the ductus arteriosus
Prenatal factors
First-trimester maternal infectionsConotruncal (lesions that lead to abnormal ventriculo-arterial alignment) and obstructive defects are more likely; rubella is associated with persistent ductus arteriosus and pulmonary artery stenosis
Maternal diabetes mellitus (especially preexisting diabetes)3% to 5% of infants of patients who have diabetes and aortic, vascular, or endocardial problems
Maternal obesityPrevalence rate ratios of aortic arch defects and transposition of the great arteries were doubled in offspring of patients with a body mass index > 40 kg per m2; atrial septal defects and persistent ductus arteriosus prevalence rate ratio increase with maternal body mass index
Prenatal diagnosticsAny diagnostic concern based on prenatal sonography of the heart (intracardiac foci in isolation do not constitute a concern)

OLDER CHILDREN

History in a child with a murmur should include the personal and family history in Table 114,2227 and questions about the signs and symptoms listed in Table 2.14,25,28,29 In older children, the probability of a murmur being the first sign of congenital heart disease is low.30,31

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