Mrs. Z. brings her healthy, thriving 9-month-old son to you because a physician in a walk-in clinic said that he heard a “heart murmur.” Mrs. Z. is worried and upset, and wants to know if this is serious. “Does my child have a ‘heart condition’?” What do you do?

In fact, most kids will have a heart murmur heard at some time in their lives. It’s important to determine whether the murmur is innocent or a sign of cardiac disease, but in children the vast majority are benign — the prevalence of significant cardiac disease is only about 0.4%.¹ A thorough history and a good physical exam are, as always, essential. I won’t attempt to be comprehensive here, but will focus on what’s important for the generalist to know. I’ve included further reading references for anyone interested.²

Feeding signs

In taking a history the following points are important to note: overall general health of the child, colour (e.g. cyanosis), cough/wheeze/dyspnea, exercise intolerance, palpitations and diaphoresis during feeding. One pearl I learned from a pediatric cardiologist is that the most vigorous exercise for an infant is feeding. If an infant takes an inordinate amount of time to feed with frequent breaks, this could be a sign of heart failure. Similarly, an infant in heart failure (tachypnea, tachycardia, cardiomegaly and hepatomegaly) may present with wheezing. Chest pain in children and adolescents is almost never a sign of cardiac disease.

Physical examination in this population is often piecemeal rather than systematic, as pediatricians like to proceed from the least invasive aspect of the exam to the more invasive. Although it may be piecemeal, it should always be comprehensive.

In the physical examination, pay attention to the growth curve, which is a very sensitive indicator of disease in infants and children. In an infant who’s failing to thrive, a cardiac murmur has more significance than in a healthy, thriving baby. Are there any dysmorphic features? In a child with trisomy 21, there’s a very high probability that the cardiac murmur heard on routine physical examination is significant. A number of other syndromes (Williams’s, Marfan’s, Noonan’s and Turner’s) are also associated with pathologic cardiac murmurs.

Observe the child before pulling out your stethoscope. Is the child tachypneic? Is he febrile (high cardiac output may cause a murmur)? Is she pale (anemia can result in a murmur)? Is the precordium quiet with no impulse or thrill when you put your hand on the chest wall? Is there hepatomegaly? Auscultation can sometimes be difficult in a crying infant or child and requires some patience.

Listen carefully

It’s useful to try and relate what you hear to the cardiac cycle (see diagram).³

Listen carefully to S1 and S2. S1 represents closure of the atrioventricular valves and normally isn’t split. S2 consists of aortic (A2) and pulmonic (P2) valve closures. There is normally an appreciable split between A2 and P2, due to the fact that there’s lower resistance in the pulmonary vasculature, which results in slower closure of the pulmonic valve. A fixed split in S2 is pathognomonic for an atrial septal defect (ASD). There may be a third heart sound after S2 representing rapid filling of the ventricles (see diagram). An ejection click may be heard with closure of either the aortic or pulmonic valve if they’re stenotic — this may be mistaken for a split S1. Following auscultation, don’t forget to check the blood pressure and the pulses. An infant with absent femoral pulses requires immediate referral to a pediatric cardiologist (aortic coarctation). It’s also important to auscultate with the child sitting as well as supine; a benign murmur often changes in intensity with such manoeuvres.³

Systolic murmurs may occur throughout systole from S1 to S2 (pansystolic) and represent regurgitation through the atrioventricular valves or from a high pressure (e.g. left ventricle) to a low-pressure area (right ventricle) through a ventricular septal defect (VSD). A systolic ejection murmur begins after S1 and represents flow in the great vessels. Diastolic murmurs are sometimes difficult to appreciate but are always pathologic, with the exception of a venous hum (see below).

Keys to differentation

Murmurs can be classified according to their loudness and associated features such as a thrill or precordial heave. Grade 1 is hardly audible; Grade 2 is audible; Grade 3 is loud with no palpable thrill; Grade 4 is loud with a thrill; Grades 5 and 6 are loud enough to be heard with the stethoscope barely touching or not touching the chest wall at all. Pathologic murmurs are usually Grade 3 or higher.

The classic innocent murmur is the Still murmur, heard usually between the ages of 3-6 months; the murmur is often heard at the left sternal border and its intensity is grade 2-3. In newborns or premature infants, a systolic murmur heard best in the upper left sternal border and radiating to the back is a pulmonary flow murmur; it’s related to the sharp angle of the bifurcation between left and right pulmonary arteries; it may be grade 1-2 in intensity and resolves by the age of 3-6 months. A carotid bruit may be heard at any age in the right supraclavicular area and over the carotids; it may be 2-3 in intensity. Another dramatic murmur that can be worrisome if you’re not familiar with it is the venous hum. This is a systolic-diastolic murmur heard maximally in the supraclavicular region. It may have an intensity of 1-3 and the diastolic component may suggest true pathology. The key to differentiate this from a pathologic murmur is to note its disappearance or decreased intensity when either turning the head or compressing the jugular vein.

An analysis of pediatric cardiologist consultations over a year in one tertiary care centre found that four diagnoses accounted for 91% of cardiac murmurs: patent ductus arteriosis (PDA), ventricular septal defect (VSD), innocent murmur and pulmonary branch murmur of infancy.⁴ Keep in mind that most pediatric murmurs heard in primary care are innocent.

A good history and physical exam should enable the physician to determine which murmurs require further investigation or referral. There are some excellent audio programs available to improve ausculatory skills — they’re worth the investment.⁵