HEART MURMURS
Auscultation is a critical component of the physical examination of the infant or child. A proper examination is conducted in a quiet environment so that the examiner’s attention is focused entirely on the auscultatory findings. In general, a “pediatric” stethoscope is not necessary, and in some cases “neonatal” stethoscopes with long tubing and a small head may be inferior to an “adult” stethoscope, which transmits sounds more reliably. It is important to examine all areas of the body and listen over the precordium in addition to the right side of the chest and both sides of the back. Finally, the examiner should note any changes in the heart sounds caused by respiration or a change in the patient’s position. Children should be examined in the supine and standing positions so that the effect of a change in position on murmurs can be appreciated.
In addition to noting the characteristics of any murmurs, the examiner should assess the patient’s overall clinical condition, measure the heart rate and blood pressure,
and palpate the pulses in all the four extremities. The strength of the precordial impulse and the presence or absence of a thrill should also be noted. Finally, the first and second heart sounds (S
1 and S
2) should be characterized. Split heart sounds and the effect of respiration on the S
2 should be noted. A split S
1 is normal. The S
2 normally splits variably with respiration.
A fixed split of the S2 is characteristic of atrial septal defect. Any additional sounds—for example, clicks—should also be noted.
Most murmurs in infants and children are innocent murmurs that are not caused by any structural abnormality or pathologic flow
(Table 24.1). The most common murmur in the newborn is a
pulmonary branch stenosis murmur resulting from the relatively small size of the branch pulmonary arteries at birth. This is a systolic ejection murmur heard over the precordium and also in the right side of the chest and both sides of the back. The presence of a systolic ejection murmur in the right and left axillae is characteristic of a pulmonary branch stenosis murmur. This type of murmur is generally inaudible after the age of 4 months.
The Still murmur is a vibratory, musical, or buzzing noise heard during ejection, generally along the left sternal border. It can be heard at any age and is more prominent during an increase in cardiac output (e.g., fever, exercise). The Still murmur is loudest when the patient is in a supine position and becomes attenuated or inaudible when the patient stands. Any ejection murmur that increases in intensity when the patient is standing is likely pathologic and should prompt further investigation.
A venous hum is commonly heard in younger children in the upright position. This murmur is a continuous blowing sound created by the flow of blood in the large veins from the neck into the thorax. The murmur of a venous hum can be abolished by compressing the jugular veins on the ipsilateral side or by turning the patient’s head. This murmur could be confused with a patent ductus arteriosus.
Physiologic changes, especially in the perinatal period, affect the clinical examination findings, especially the features of murmurs. At birth, because the pulmonary artery resistance is elevated, the right ventricular and left ventricular pressures are nearly equal. Therefore, little blood flows from the left ventricle to the right ventricle in an infant with a ventricular septal defect immediately after birth, so that the holosystolic murmur of ventricular septal defect is rare during the first several days of life. As the pulmonary vascular resistance decreases during the first week, the volume and velocity of the flow through the ventricular septal defect increase to produce the typical holosystolic, harsh murmur associated with ventricular septal defect. On the other hand, stenotic lesions (e.g., aortic stenosis, pulmonary stenosis) are associated with high-velocity, disturbed flow during the systolic ejection period and cause systolic ejection murmurs immediately after birth.
In the newborn, in whom the pulmonary resistance and right ventricular pressure are elevated, moderate tricuspid regurgitation is common. In this setting, the jet of tricuspid regurgitation produces at the lower left sternal border a holosystolic murmur that is indistinguishable from the typical murmur of a ventricular septal defect. As the pulmonary resistance decreases, the murmur of the tricuspid regurgitation becomes less intense, lower in pitch, and eventually inaudible, usually during the first day or two after birth.
In the normal newborn, systolic ejection murmurs can be caused by:
Patent ductus arteriosus
Peripheral pulmonary stenosis
Flow through the right ventricular outflow tract (pulmonary flow murmur)
Vibration in the left ventricular outflow tract (Still murmur)
In comparison with innocent murmurs, pathologic murmurs tend to be louder, usually grade 3 or higher, and harsher. Holosystolic murmurs are always pathologic, as are murmurs associated with systolic clicks or an abnormal S2. Further evaluation is recommended for all children with a:
Most studies have shown that a pediatric cardiology consultation is more cost-effective than echocardiography performed without consultation as an initial step in the evaluation of a heart murmur.
