What are the criteria for determining when a heart murmur is pathological or requires further evaluation in infants?

From the Guidelines

To determine if a heart murmur in an infant is pathological or requires further workup, focus on specific clinical features, and any murmur with concerning features should prompt referral for echocardiography and pediatric cardiology evaluation, as recommended by the 2017 AHA/ACC guidelines 1. When evaluating a heart murmur in an infant, it is crucial to consider the characteristics of the murmur, including its intensity, quality, timing, and location. Pathological murmurs are typically grade 3/6 or louder, harsh in quality, diastolic or continuous in timing, associated with thrills, or heard best at the upper left sternal border or back. Additional concerning features include cyanosis, abnormal pulses, hepatomegaly, failure to thrive, respiratory distress, or abnormal heart sounds like clicks or gallops. Some key points to consider when evaluating a murmur in an infant include:

• The intensity of the murmur, with louder murmurs being more concerning
• The quality of the murmur, with harsh or diastolic murmurs being more likely to be pathological
• The presence of associated symptoms, such as cyanosis or respiratory distress
• The family history of congenital heart disease or sudden cardiac death In contrast, innocent murmurs are usually soft (grade 1-2/6), systolic, without radiation, and vary with position or respiration. They typically disappear when the infant is calm. According to the ACC/AHA guidelines for the clinical application of echocardiography 2, serial evaluations by echocardiography are recommended in the presence of inflammatory diseases that may result in abnormalities in the proximal or distal coronary circulation, myocarditis, myocardial infarction, and pericardial effusion. The 2017 AHA/ACC guidelines provide a comprehensive framework for evaluating heart murmurs in infants, including the definition of innocent and pathological murmurs, and the recommended approach to evaluation and management 1. Early detection of pathological murmurs is crucial, as some congenital heart defects may not cause immediate symptoms but can lead to complications if left untreated. When in doubt about a murmur's significance, it is safer to refer for specialist assessment rather than monitoring without investigation.

From the Research

Evaluation of Heart Murmurs in Infants

To determine if a murmur is pathological or requires further workup in infants, several factors should be considered:

• Historical elements that suggest pathology, including family history of sudden cardiac death or congenital heart disease, in utero exposure to certain medications or alcohol, maternal diabetes mellitus, history of rheumatic fever or Kawasaki disease, and certain genetic disorders 3
• Physical examination findings, such as vital signs, age-appropriate exercise capacity, respiratory or gastrointestinal manifestations of congestive heart failure, and a thorough cardiovascular examination, including features of the murmur, assessment of peripheral perfusion, and auscultation over the heart valves 3
• Red flags that increase the likelihood of a pathologic murmur, including a holosystolic or diastolic murmur, grade 3 or higher murmur, harsh quality, an abnormal S2, maximal murmur intensity at the upper left sternal border, a systolic click, or increased intensity when the patient stands 3

Referral to a Pediatric Cardiologist

Referral to a pediatric cardiologist is recommended for:

• Patients with any other abnormal physical examination findings 3
• Patients with a history of conditions that increase the likelihood of structural heart disease 3
• Patients with symptoms suggesting underlying cardiac disease 3
• Newborns with a murmur, as neonatal murmurs have higher rates of pathology than in older children 4

Diagnostic Tests

• Electrocardiography and chest radiography are not typically recommended for the evaluation of heart murmurs in infants, as they rarely assist in the diagnosis 3
• Echocardiography provides a definitive diagnosis and is recommended for the evaluation of any potentially pathologic murmur, as well as for the evaluation of neonatal heart murmurs 3
• Pulse oximetry screening is recommended for all infants to detect underlying critical congenital heart disease 4