Heart murmur

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Chapter 21 HEART MURMUR

Theodore X. O’Connell

General Discussion

As many as 90% of children will have an audible heart murmur at some time, yet the incidence of structural congenital heart disease is estimated to be less than 1% of all live births. A murmur may be heard in 60% of healthy newborn babies. As such, the physician must determine which patients require further evaluation.

Features of concern in infants include feeding intolerance, failure to thrive, respiratory symptoms, or cyanosis. In older children, chest pain (especially with exercise), syncope, exercise intolerance, or a family history of sudden death in young people should raise the physician’s level of suspicion. Other features that increase the likelihood of cardiac pathology include malformation syndromes, increased precordial activity, decreased femoral pulses, abnormal second heart sounds, clicks, a loud or harsh murmur, and increased intensity of the murmur when the patient stands.

The clinical diagnosis of a normal or innocent murmur should occur in the setting of an otherwise normal history, physical examination, and appearance. The innocent systolic murmurs are soft (grade 1 or 2) and ejection in quality. Normal murmurs are never solely diastolic. The intensity of an innocent murmur is grade 3 or less and, consequently, is never associated with a palpable thrill. Most murmurs, both innocent and organic, may be accentuated by fever, anemia, or increased cardiac output.

The pathologic systolic murmur occurs early in systole and can be quite loud. Diastolic murmurs are much less common in children, and the presence of a diastolic murmur indicates that structural heart disease is present and warrants referral. Continuous precordial murmurs in infants are also generally pathologic, with the exception of the venous hum. The venous hum should resolve in the supine position or with gentle compression of the jugular vein. Patients with venous hums do not require pediatric cardiology referral.

Holosystolic murmurs occur when a regurgitant atrioventricular valve is present or in association with most ventricular septal defects. Ejection murmurs may arise from narrowing of the semilunar valves or outflow tracts. Innocent murmurs are almost exclusively systolic ejection in nature. They are generally soft, never associated with a palpable thrill, and vary considerably with positional changes. Early systolic murmurs are associated exclusively with small muscular ventricular septal defects. Mid-to-late systolic murmurs are often heard in association with mitral valve prolapse.

Diastolic murmurs may be associated with regurgitation of the aortic or pulmonary valves, stenosis of an atrioventricular valve, or increased flow across an atrioventricular valve. Early diastolic murmurs arise from either aortic or pulmonary valve insufficiency. Mid-diastolic murmurs occur because of either increased flow across a normal tricuspid valve or mitral valve or normal flow across an obstructed or stenotic tricuspid or mitral valve. Late diastolic or crescendo murmurs are caused by stenotic or narrowed atrioventricular valves.

Specific Lesions

Most innocent heart murmurs in healthy term infants are related to peripheral pulmonary stenosis, which is reduced in two thirds of cases by 6 weeks of age and in most others by 6 months. The murmur is soft (grade 1 or 2), ejection in quality, and best heard anteriorly at the left upper sternal border with characteristic transmission to the axillae and back bilaterally. No associated signs or symptoms of heart disease are present. The murmur of atrial septal defect may mimic this murmur but is generally heard in later infancy or childhood. Pathologic peripheral pulmonary stenosis is typically more severe, has a louder murmur, and does not regress over time. If peripheral pulmonary stenosis is suspected in the term infant, close follow-up is indicated. If the murmur intensifies or persists after 6 months of age, cardiology referral is indicated.

Isolated ventricular septal defects are the most common congenital heart defect identified through the first three decades of life. Infants with ventricular septal defect can present in different ways, and presentation is determined by the size of the defect and the status of the pulmonary vascular resistance. Most commonly the murmur is detected at 2 to 6 weeks of age. The infant with a small ventricular septal defect may have a loud murmur but appears healthy with normal growth and no cardiac symptoms. The precordial activity is normal, and there typically is no palpable systolic thrill. The infant with a moderate-sized ventricular septal defect often has poor weight gain and may have dsypnea and diaphoresis, particularly with feedings. The murmur is loud, is frequently associated with a systolic thrill, is harsh and holosystolic, and obscures the first and second heart sounds. A prominent third heart sound or diastolic flow murmur can be heard at the cardiac apex. The infant with a large ventricular septal defect has significant clinical symptoms such as feeding problems, failure to thrive, and irritability. The murmur is soft, short, and early systolic. There is a marked right ventricular heave with a loud and single second heart sound. A prominent third heart sound and diastolic rumble are common, and hepatomegaly is usually present. Cardiology referral is indicated for children with suspected ventricular septal defect.

Tetralogy of Fallot refers to a spectrum of abnormalities characterized by a large ventricular septal defect and right ventricular outflow tract obstruction. It is the most common form of cyanotic congenital heart disease and is associated with a higher incidence of extracardiac anomalies and malformation syndromes. The clinical presentation depends on the severity of right ventricular outflow tract obstruction. If the degree of right ventricular outflow tract obstruction is severe, the infant can present with severe cyanosis as the patent ductus arteriosus closes. The right ventricular impulse is increased, there may be a systolic thrill, and the second heart sound is typically single. The murmur can be loud, is ejection in quality, and diminishes in intensity and length when the degree of obstruction increases. If tetralogy of Fallot is suspected, pulse oximetry should be performed. A chest radiograph may demonstrate a boot-shaped heart. Prompt cardiology referral is indicated.

In pulmonary valve stenosis, the intensity of the murmur depends on the severity of obstruction. The right ventricular impulse is prominent, and there may be a systolic thrill at the left upper sternal border. An ejection sound is characteristic and is recognized by its high-pitched clicking quality, which varies with respiration. The pulmonic component of the second heart sound is delayed and soft. The murmur is often loud, ejection in quality, and best heard at the left upper sternal border. Cardiology referral is indicated.

Isolated atrial septal defects are rarely diagnosed in the neonate. Young children with atrial septal defects often have a thin habitus. Precordial palpation reveals a prominent hyperdynamic right ventricular impulse. Wide, fixed splitting of the second heart sound is the auscultatory hallmark. The murmur is usually grade 2 or 3, systolic ejection in quality, and heard best at the left upper sternal border. A mid-diastolic flow rumble is present. Pulse oximetry should be normal. Cardiology referral is indicated.

Aortic stenosis is much more common in males. Most infants with this lesion are otherwise healthy, with appropriate growth and development, unless severe aortic stenosis is present. The left ventricular impulse can be normal in mild obstruction or increased in more moderate obstruction. A systolic thrill is common and may be appreciated in the suprasternal notch and over both carotid arteries. The murmur is maximal in the second right interspace, with radiation to the right and into the neck. The intensity of the murmur is variable. A louder, longer, late-peaking murmur generally is indicative of more significant obstruction. Cardiology referral is indicated, with more urgent referral in the neonate or young infant.

The hallmark clinical feature of coarctation of the aorta is absent or weak femoral pulses. The diagnosis can be confirmed when a higher measured blood pressure is observed in the arm compared with the leg. A systolic ejection click may be heard if there is an associated bicuspid aortic valve. The murmur is generally soft, ejection in quality, and audible at the left upper sternal border and over the left back. Urgent cardiology referral is indicated.

The most common innocent murmur in children is the vibratory Still’s murmur. The murmur is typically audible between ages 2 and 6 years, but it may be present as late as adolescence or as early as infancy. The murmur is low to medium in pitch, confined to early systole, generally grade 2, and maximal at the lower left sternal edge and extending to the apex. The murmur is generally loudest in the supine position and often changes in character, pitch, and intensity with upright positioning. The most characteristic feature of the murmur is its vibratory quality.

Key Physical Findings

Vital signs, including heart rate, respiratory rate, and blood pressure

Growth parameters plotted on a growth chart

General assessment of overall appearance

Dysmorphic features or extracardiac anomalies

Assessment for cyanosis

Signs of respiratory distress such as tachypnea, retractions, grunting, or nasal flaring

Cardiac examination

• Inspection and palpation for precordial bulge, substernal heave, or palpable precordial thrill

• Auscultation

Auscultation should be performed with the patient in the supine, sitting, and standing positions

The first heart sound, which reflects closure of the mitral and tricuspid valves, is typically single and is best heard at the left lower sternal border

The second heart sound, which reflects closure of the aortic and pulmonary valves, is split, varies with respiration, and is best heard at the left upper sternal border

Third and fourth heart sounds can be normal in the child, are typically low in frequency, and are best heart at the cardiac apex

Murmurs should be described by their intensity, timing, location, and radiation. Any variability of the murmur with a change in position or a maneuver should be described

Dynamic maneuvers, including respiration, Valsalva, exercise, and postural changes, may provide important diagnostic information.

• Assessment of the peripheral pulses for rate, rhythm, and character (especially the femoral pulses). After the brachial pulses have been palpated, the right brachial pulse should be palpated simultaneously with the femoral pulse

• Assessment of capillary refill time

Abdominal examination for liver character and size

Extremity examination for pallor or clubbing

Suggested Work-Up

The evaluation of a pediatric heart murmur is based on a thorough history and physical examination, described above. Echocardiography or pediatric cardiology consultation should be based on the suspected cause of the murmur.

1. Frommelt M.A. Differential diagnosis and approach to a heart murmur in term infants. Pediatr Clin North Am. 2004;51:1023–1032.

2. Harris J.P. Evaluation of heart murmurs. Pediatr Rev. 1995;12:490–493.

3. McConnell M.E., Adkins S.B., Hannon D.W. Heart murmurs in pediatric patients: when do you refer? Am Fam Physician. 1999;60:558–565.

4. Pelech A.N. Evaluation of the pediatric patient with a cardiac murmur. Pediatr Clin North Am. 1999;46:167–187.

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