doi: 10.1161/01.CIR.0000153388.41229.CB
(Circulation. 2005;111:e20-e22.)
© 2005 American Heart Association, Inc.
Clinician Update |
Innocent Murmurs
From the Department of Pediatrics, Division of Pediatric Cardiology, School of Medicine, State University of New York-Stony Brook, Stony Brook, New York.
Correspondence to Thomas Biancaniello, MD, Department of Pediatrics, Division of Pediatric Cardiology, SUNY-Stony Brook School of Medicine, Stony Brook, NY 11794-8111. E-mail tbiancan{at}notes.cc.sunysb.edu
A 7-year-old boy visited his primary care physician for his annual school physical. The child had been in perfect health. He reported no cardiovascular symptoms. The boy’s physical examination was normal except for a 2 to 3/6 systolic ejection murmur not previously heard at the lower left sternal border. How should a clinician distinguish between innocent murmurs and pathological murmurs, and what factors should be evaluated? If the primary care physician is unsure whether the murmur is innocent, then referral to a pediatric cardiologist is the next step.
Murmurs are common findings in infants and children. Most murmurs in infants and children originate through normal flow patterns with no structural or anatomic abnormalities of the heart or vessels and are referred to as "innocent," "physiological," or "normal" murmurs. "Innocent" is the preferred term because it strongly conveys that nothing is abnormal, as opposed to the older term "functional," which is not always understood clearly by parents and patients as being "normal." Although murmurs may be heard in virtually anyone, they are most commonly heard in children. Virtually all children will have a murmur sometime while they are growing up. Conversely, murmurs may be created by abnormal flow patterns in the heart and vessels resulting from congenital heart abnormalities, valve disease, or other acquired conditions. In evaluating the infant or child with a murmur, the clinician must make a complete assessment of the cardiovascular system—not just listen to the murmurs—because there are some serious cardiovascular abnormalities that may have no murmurs.
Looking for clues of heart disease, the clinician must obtain a focused history from the patient’s parents. For infants, this history will include birth history, feeding patterns, breathing difficulties, color changes, growth pattern, and activity levels. Changes in feeding patterns, particularly a progressively longer time to complete the feeding, may be an early sign of congestive heart failure. For children, parents should be asked about activity capacity: Can the child keep up with peers while playing vigorously? Have there been complaints of shortness of breath, palpitations, or chest pain? Chest pain is a common complaint, but a cardiac cause is found in less than 1% of children complaining of chest pain.1 Syncope occurs in about 15% of children before they reach 21 years of age,2 and it is most often not the result of primary heart problems; however, the practitioner will want to know whether syncope has occurred and under what circumstances so cardiac causes can be excluded. Although not commonly associated with cardiac disease in childhood, syncope and chest pain may be manifestations of serious cardiac conditions such as aortic stenosis or hypertrophic cardiomyopathy, which are common causes of sudden unexpected death in childhood.3 If these symptoms are present, particularly if they are related to exercise or there is a positive family history of hypertrophic cardiomyopathy, then they should be evaluated carefully.
Obtaining a thorough family medical history is extremely important in assessing a child because congenital heart defects occur more commonly in families in which a first-degree relative has been born with a heart defect.4 In addition, hypertrophic cardiomyopathy, a primary muscle disorder of the heart, is an inherited autosomal dominant condition that may result in sudden unexpected death, especially during or after vigorous exercise, in young people.5 Obtaining a history of this condition or of sudden unexplained death in young people with first-degree relatives who have a heart defect entails a search for hypertrophic cardiomyopathy, which may be silent.
Physical examination of a child includes an assessment of general appearance, color, respiratory effort, and vital signs, including heart rate, respiratory rate, and blood pressure. The vital signs should be evaluated by comparing them with age-established norms. The neck should be evaluated for prominence of vessels and abnormal pulsation and listened to for bruits. The chest should be auscultated for abnormal breath sounds. The pulses in the arms and legs should be checked. If the pulses are not equal, then coarctation of the aorta may be present and 4 extremity blood pressures should be obtained.
Examination of the heart begins with observation and palpation of the chest for abnormal impulses and thrills. Auscultation begins with listening for the normal sounds of the valves closing and for S1 and S2. It is important not to focus on murmurs initially. Atrial septal defect accounts for about one third of the congenital defects first detected in adulthood.6 This is because the characteristic murmur, a pulmonary flow murmur, also is one of the most common childhood innocent murmurs. The key to diagnosis is appreciating the wide fixedly split-second heart sound resulting from right volume overload. This will not be easily appreciated if the clinician focuses on murmurs before defining the heart sounds. Gallop sounds also may be present, signaling difficulty in keeping up with the demands placed on the heart. Conversely, isolated S3 gallop sounds may be heard in healthy adolescents.
When murmurs are heard, they should be defined by the following characteristics:
- Timing—when during the cardiac cycle they occur
- Location—where in the heart they may originate, keeping in mind that vibrations are transmitted in both directions along a column of blood
- Quality or pitch—how they sound, which is important in differentiating normal flow murmurs from abnormal
- Intensity or loudness—not necessarily defining the severity, but changes in intensity may help determine the type of murmur being heard
- Ejection or nonejection clicks—presence or absence
Innocent murmurs are murmurs produced by normal flow. Changing the flow should therefore change the intensity of the murmur. Characteristically, maneuvers that decrease the flow of blood returning to the heart through the venous system will decrease the intensity of flow murmurs, suggesting that the murmur is flow related or innocent. Changing the child’s position from supine to sitting, then to standing, and finally to squatting during the examination will change the flow and is useful in helping to define innocent murmurs. The child may be asked to push out the abdomen or bear down to perform a Valsalva maneuver, which reduces venous blood flow to the heart and the intensity of innocent murmurs. An examiner can coax even a young toddler into doing this by placing a hand on the child’s abdomen and asking the child to push it out.
The following are the classic types of innocent or flow murmurs:
- Still’s murmurs.7 These murmurs are low-pitched sounds heard at the lower left sternal area. They are musical or have a relatively pure tone in quality or may be squeaky. These most commonly occur between age 3 and adolescence. Because they are low pitched, they are heard best with the bell of the stethoscope. They are related to flow, and they can change with position alteration and then can decrease or disappear with the Valsalva maneuver. No clicks are present.
- Pulmonary flow murmurs. These are high-pitched, harsher murmurs heard at the upper left sternal border. Because they are high pitched, they are heard best with the diaphragm of the stethoscope. They are flow dependent and also will change with position alteration and decrease or disappear with the Valsalva maneuver. These murmurs originate from the right ventricular outflow tract and radiate along the pulmonary arteries and thus may be well heard in the back and axilla bilaterally. They are differentiated from pulmonic stenosis by their quality and from valvar pulmonic stenosis by the absence of an ejection click. Pulmonary flow murmurs can occur at any age, but they are common particularly in adolescents or in children with pectus excavatum. They are prominent in high-flow situations, such as when a child has a fever or is anemic, because flow increases in these situations. In infants, these sounds may be most prominent in the back or axilla because turbulence occurs when the blood flows from the larger main pulmonary artery to the smaller, less well-developed distal pulmonary arteries. In fetal life, the main pulmonary artery transports about 90% of the blood to the ductus arteriosus and only about 10% to the distal pulmonary arteries. The main pulmonary artery is thus large, whereas the distal pulmonary arteries are relatively smaller and come off at more acute angles than they do later as the child’s chest grows. An analogy from nature would be the noise that is created as a large stream narrows into smaller streams. This innocent murmur has been termed "benign peripheral pulmonary stenosis of the newborn" to differentiate it from true anatomic obstructions to distal pulmonary arteries that occur in pathological conditions such as congenital rubella syndrome.
- Systemic flow murmurs (supraclavicular systemic bruits). These are harsh high-pitched murmurs caused by normal blood flow into the aorta and into the head and neck vessels and are heard best high up in the chest and above the clavicles. They are also heard best with the diaphragm of the stethoscope. No ejection click is associated with these murmurs. They are transmitted to the arch vessels and are heard when listening over the carotid arteries of the neck. It has been said that because of these sounds "all children have carotid bruits"; however, the sounds differ in quality from true carotid bruits and are not associated with aortic outflow pathology.
- Venous hums. These are low-pitched continuous murmurs made by blood returning from the great veins to the heart. They are heard best with the bell of the stethoscope. By changing the position of the patient’s head or by pressing in the area of the major neck veins, the flow may be changed and these murmurs will change or disappear. Having the child look down or to the side while listening will often make these murmurs or sounds disappear. They are differentiated from the murmurs of patent ductus arteriosus in that they are louder in diastole, when maximal flow occurs in the venous system, and are often heard bilaterally. Venous hums are sensitive to posture and head and neck position, whereas the murmur of patent ductus is not.
Although an ECG is usually part of the evaluation and may be helpful, further testing is not needed in the overwhelming majority of infants and children to distinguish between normal or pathological hearts. It has been shown that a competent pediatric cardiologist can determine with a high degree of certainty whether there is heart disease.8 Because of the characteristics of the sounds and the maneuvers that can be used to facilitate identifying them as flow-related phenomenon, these murmurs can be correctly identified without further testing.
After concluding that the murmur or murmurs (a child may have more than one kind) are innocent, the practitioner should explain the findings to the parents and child. The practitioner should emphasize during the discussion that murmurs simply mean sounds or noises and that in and of themselves they are not synonymous with abnormalities of the heart. The clinician should stress that although a large percentage of infants and children have murmurs, less than 1% are born with the congenital heart defects that are the most common cause of heart disease in children. Parents should not be promised that their children will outgrow these murmurs because this is not necessarily true; adults can have innocent murmurs as well. Assurances should be given that because the heart is normal, whether or not the murmur disappears or changes is of no consequence. In addition, because flow changes the murmur, with growth and the changing configuration of chest and heart dynamics, murmurs may change, disappear, and reappear at various times—further evidence that the murmurs are indeed flow related and innocent.
 |
References |
|---|
 Top References |
|---|
- Driscoll DJ, Glicklich LB, Gallen WJ. Chest pain in children: a prospective study. Pediatrics. 1976; 57: 648–651.
[Abstract/Free Full Text]
- Ruckman RN. Cardiac causes of syncope. Pediatr Rev. 1987; 9: 101–108.
[Abstract/Free Full Text]
- Gillette PC, Garson A Jr. Sudden cardiac death in the pediatric population. Circulation. 1992; 85: I-64–I-69.[Medline]
[Order article via Infotrieve]
- Ferencz C, Rubin JD, McCarter RJ, Brenner JI, Neill CA, Perry LW, Hepner SI, Downing JW. Congenital heart disease: prevalence at livebirth. The Baltimore-Washington Infant Study. Am J Epidemiol. 1985; 121: 31–36.
[Abstract/Free Full Text]
- Maron BJ, Roberts WC, McAllister HA, Rosing DR, Epstein SE. Sudden death in young athletes. Circulation. 1980; 62: 218–229.
[Abstract/Free Full Text]
- Brickner ME, Hillis LD, Lange RA. Congenital heart disease in adults. N Engl J Med. 2000; 342: 256–263.
[Free Full Text]
- Still GF. Common Disorders and Diseases of Childhood. London, Frowde, Hodder & Stoughton, 1909.
- Newberger JW, Rosenthal A, Williams RG, Fellows K, Miettinen OS. Noninvasive tests in the initial evaluation of heart murmurs in children. N Engl J Med. 1983; 308: 61–64.[Abstract]
Related Article:
-
Issue Highlights
Circulation 2005 111: 245.[Full Text]
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||