Abstract
Background
Pediatric heart murmurs are common and may be innocent or associated with cardiac pathology and risk of sudden cardiac arrest.
Aim of review
The aim of this article is to review the common pediatric heart murmurs including evaluation, indications for pediatric cardiology referral, and patient and family education.
Key scientific concepts of review
The first step in the evaluation of a heart murmur is to take a thorough and systematic history, including history of present illness, symptoms and signs of cardiovascular disease, and prenatal, past medical, family, and social history. The systematic cardiovascular examination includes vital signs, inspection, palpation, and auscultation. The seven characteristics of a heart murmur include timing, shape, location, radiation, intensity, pitch, and quality. The normal first heart sound S 1 occurs from mitral and tricuspid valve closure. The normal second heart sound S 2 occurs from aortic and pulmonary valve closure. Innocent murmurs such as the Still, pulmonary flow, supraclavicular murmurs, and venous hum do not require treatment. Pathologic murmurs are caused by structural heart disease and necessitate referral to a pediatric cardiologist. Systolic ejection murmurs may be caused by aortic stenosis, pulmonary stenosis, hypertrophic obstructive cardiomyopathy, or coarctation of the aorta. Holosystolic murmurs may be caused by ventricular septal defect, mitral regurgitation, mitral valve prolapse, or tricuspid regurgitation. Diastolic murmurs are pathologic and include murmurs caused by aortic regurgitation, pulmonary regurgitation, mitral stenosis, or tricuspid stenosis. The most common pathologic continuous murmur is caused by patent ductus arteriosus. Referral of a patient with a murmur to pediatric cardiology is indicated by age, murmur characteristics, associated symptoms and findings consistent with possible cardiovascular disease, and family and genetic history. Parental anxiety about the upcoming cardiology visit may be decreased through discussion with the clinician.
Highlights
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Heart murmurs are produced by turbulent blood flow.
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Pediatric heart murmurs are common and may be innocent or associated with pathology.
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Murmurs are evaluated with history and physical examination including auscultation.
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Murmurs vary with timing, shape, location, radiation, intensity, pitch, and quality.
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Pathologic murmurs may be systolic ejection, holosystolic, diastolic, or continuous.
1
Introduction
Murmurs are extra sounds that occur when blood flows through heart valves and arteries. Murmurs are common in childhood and are the most frequent reason for referral to a cardiologist. They may appear after birth or during childhood, adolescence, or adulthood. Murmurs may be classified as innocent (also known as functional or benign) or pathologic. Innocent heart murmurs are harmless sounds created by the flow of blood through an otherwise structurally normal heart and are the most common murmurs, occurring in 33 % to 75 % of children between ages 1 and 14 years [ ]. In contrast, a pathologic murmur is an abnormal heart sound created by the flow of blood in a structurally abnormal heart.
Pathologic murmurs are rare but may create a diagnostic dilemma for primary care providers in diagnosing a child who has structural heart disease or the risk of sudden cardiac arrest. Therefore, it is important for pediatric providers to have a systematic method of evaluating each child. This includes a comprehensive patient history and cardiovascular physical examination. Pediatricians care for children throughout growth and maturation and must be familiar with associated changes in the cardiovascular system.
The purpose of this article is to review the common pediatric heart murmurs including evaluation, indications for pediatric cardiology referral, and methods of discussion with patients and families.
2
History
The first step in the evaluation of a heart murmur is to take a thorough and systematic history ( Table 1 ) [ ]. The clinician seeks to understand the patient’s symptoms and risk factors for cardiovascular disease. The American Academy of Pediatrics and American Heart Association have published national standards for cardiovascular screening [ , , ].
| History of the present illness | Prenatal history |
| When was the murmur first detected? | Uncontrolled gestational diabetes c |
| Any previous murmur detected? | Maternal infections d |
| Any associated cardiovascular symptoms? a | Maternal exposure to drugs or other toxins d |
| Infants | Family history e |
| Cyanosis | Mother or father: congenital heart disease |
| Diaphoresis | Any family member: heart procedures or surgery |
| Failure to thrive | Any immediate family member: |
| Feeding intolerance | Died of heart problems |
| Respiratory distress | Unexpected sudden death, age < 50 y |
| Tachypnea | Any relative with: |
| Children, adolescents, or adults | Arrhythmogenic right ventricular dysplasia |
| Chest pain | Brugada syndrome |
| Dizziness | Catecholaminergic polymorphic ventricular tachycardia |
| Dyspnea | Hypertrophic cardiomyopathy |
| Exercise intolerance | Long QTc syndrome |
| Palpitations | Marfan syndrome |
| Seizure | Pacemaker or defibrillator at age < 50 y |
| Syncope | Short QTc syndrome |
| Past medical history | Social history (recommendation) f |
| Preexisting cardiovascular disease | Diet (eat better) |
| Hypertension | Physical activity (≥ 60 min/d) |
| Hyperlipidemia | Tobacco or illicit drug use (quit) |
| Anemia b | Sleep (age 13–18 y, 8–10 h/night; younger, > 8–10 h) |
| Thyroid dysfunction b | Body weight (body mass index <25 kg/m 2 ) |
| Diabetes b | Cholesterol (screen every 5 y from age 9–11 y) g |
| Fever b | Blood sugar control |
| Blood pressure (routine check age ≥ 3 y) h |
a Chest pain or syncope at any age and a new murmur in a teenager are important abnormal symptoms or signs of potential cardiovascular pathology [ , ].
b Conditions associated with hyperdynamic state may predispose to murmurs.
c Uncontrolled gestational diabetes may place the child at higher risk for developing congenital heart disease or left ventricular hypertrophy because insulin may function as a fetal growth factor.
d Maternal infections and exposure to drugs or other toxins may increase risk of developing cardiovascular disease.
e Family history is important because cardiovascular diseases may be inherited, including with autosomal dominant inheritance.
f Recommendations adapted from the American Heart Association Life’s Essential 8 key measures for improving cardiovascular health [ ]. Some of these factors may be part of the past medical history (e.g., body weight, cholesterol, blood sugar, and blood pressure). They might not be directly pertinent to a heart murmur but are important for assessing a child’s cardiovascular risk factors.
g Cholesterol screening: if there is a family history of high cholesterol or early heart attacks or stroke, screening may start at age 2 y.
h Blood pressure screening: if patient has risk factors, begin screening earlier than age 3 y.
The history of the present illness gives the provider important information about whether the child with the heart murmur is symptomatic. When evaluating infants, a prenatal or pregnancy history may identify neonates with an elevated cardiovascular risk profile. Past medical history may identify preexisting cardiovascular disease or secondary diseases that may be associated with heart murmurs. The family history is important because many forms of cardiovascular disease may be genetically inherited or associated with common environmental or lifestyle factors; when a condition with autosomal dominant inheritance is identified in the family history, the child is screened because there may be a 50 % risk, depending on the penetrance, of cardiovascular disease inherited from the parents. The social history is important for assessing older children and teenagers with heart murmurs as they become more independent and begin to make their own lifestyle choices.
3
Systematic cardiovascular examination
The systematic physical examination includes vital signs, inspection, palpation, and auscultation. A complete set of vital signs may include the heart rate, respiratory rate, systolic and diastolic blood pressure levels, and pulse oximetry measurements. The normal values of heart rate and blood pressure change with maturation. If the child has hypertension or coarctation of the aorta is suspected, then upper (right arm) and lower limb (right or left leg) blood pressures may be measured. With normal physiology, blood pressure is greater in the lower than upper limbs. When the blood pressure is >20 mmHg greater in the upper than lower limbs, the presence of coarctation of the aorta may be suspected.
Inspection of the patient begins with observation of the physical features and may focus on signs associated with genetic or congenital anomalies, general appearance, respiratory status, and assessment of noncardiac systems such as the skin, mouth, nails, and limbs. Inspection may show dysmorphic features, failure to thrive, tachypnea, pale color, clubbing, cyanosis, or edema [ ]. Observed abnormalities may increase the index of suspicion for the presence of cardiac disease.
Cardiovascular palpation is a multistep, important part of the cardiac examination. Peripheral and central pulses are palpated to assess heart rate, rhythm, and effectiveness of systemic perfusion. Palpation of the precordium may determine the point of maximal impulse, which typically is palpable in healthy patients at the left fourth to fifth intercostal space and midclavicular line. In hearts with structural abnormalities or congestive heart failure, the point of maximal impulse may be shifted, or vibratory sensations known as thrills may be present. Palpation of the liver may reveal hepatomegaly. Auscultation is the most important skill for defining a heart murmur.
4
The cardiac cycle
Auscultation of a murmur depends on a clear understanding of the normal cardiac cycle and generation of the heart sounds in normal cardiac physiology [ , ]. Pathologic murmurs may occur throughout the cardiac cycle and are characterized by the timing variants within the cycle [ ].
A simple way to describe the cardiac cycle is to consider blood flow, pressure, and volume on the left side of the heart [ ]. During diastole, blood flows from the left atrium through the mitral valve to the left ventricle; this flow occurs passively early in diastole and actively upon atrial contraction later in diastole. As a result, blood fills and builds pressure in the left ventricle. The first heart sound (S 1 ) is defined as the sound made by closure of the atrioventricular valves (mitral and tricuspid valves), which occurs at the beginning of systole and after filling of the ventricles. As systole begins, isovolumetric ventricular contraction occurs, creating increased pressure in the ventricles without a volume change. After the ventricles develop sufficient pressure to open the semilunar valves (aortic and pulmonary valves), the ejection phase of systole begins. After the ventricular volume is ejected and ventricular pressure decreases, the next diastole begins, and the second heart sound (S 2 ) is made from closure of the aortic and pulmonary valves.
5
Characteristics of heart murmurs
There are seven characteristics of a heart murmur that enable systematic description of the murmur: timing, shape, location, radiation, intensity, pitch, and quality ( Table 2 ). The timing of the murmur indicates the phase of the cardiac cycle when the murmur is heard: systolic, diastolic, or continuous. Murmur shape is a description of the intensity of the murmur over time within the cardiac cycle, such as the crescendo-decrescendo shape of an ejection murmur that is most intense during early ventricular ejection of systole and dissipates as ejection ends.
| Characteristic |
|---|
| Timing |
| Systolic |
| Diastolic |
| Continuous |
| Shape |
| Crescendo |
| Crescendo-decrescendo |
| Decrescendo |
| Holosystolic |
| Location |
| Aortic valve: right ICS 2, sternal border |
| Pulmonary valve: left ICS 2, sternal border |
| Tricuspid valve: left ICS 4, sternal border |
| Mitral valve: left ICS 5, midclavicular line |
| Radiation |
| Intensity (Levine grade) |
| 1. Barely audible |
| 2. Soft but easily audible; S 1 and S 2 louder than murmur |
| 3. Moderately loud; no thrill. Murmur louder than S 1 and S 2 |
| 4. Louder; palpable thrill present |
| 5. Audible with stethoscope barely on chest |
| 6. Audible without stethoscope on chest |
| Pitch |
| Low |
| Medium |
| High |
| Quality |
| Blowing |
| Harsh |
| Honking |
| Machinery-like |
| Musical |
| Rumbling |
| Vibratory |
| Whooping |
The location of the heart murmur is the anatomic place where the murmur is best heard, such as the murmurs of the aortic valve that may be loudest at the right second intercostal space and sternal border ( Table 2 ) [ ]. The position of the patient also is important because of associated changes in preload, and a murmur may be more prominent in the supine or seated position. When the position of the patient is changed, innocent murmurs commonly dissipate, but pathologic murmurs typically persist.
Radiation of the murmur refers to the site where the murmur sound may travel within the cardiovascular system. A murmur of aortic stenosis may radiate to the carotid arteries and be heard in the neck bilaterally. Intensity refers to the loudness of a heart murmur and is graded according to the Levine scale (1, barely audible; 6, audible without stethoscope on chest) ( Table 2 ) [ , ].
Pitch is the perception of the frequency of sound and is commonly classified as low, medium, or high. Pitch is determined by the pressure gradient across the pathologic lesion. A large gradient causes a high pitched murmur, while a low pressure gradient causes a low pitched murmur. Quality refers to the unique characteristics of the murmur, such as a harsh, blowing, or vibratory murmur.
6
Normal heart sounds
The first heart sound (S 1 ) is produced by the closure of the mitral and tricuspid valves and is best heard at the apex (near midclavicular line) and left lower sternal border. It is described as a high-pitched, short, and sharp “lub” sound (similar to hub). Some conditions may cause splitting of S 1 , such as Ebstein anomaly and right bundle branch block, but it is very uncommon to have S 1 splitting in normal children [ , ]. Listening tips for S 1 include using the diaphragm of the stethoscope, listening at the left fifth intercostal space and midclavicular line, and paying close attention to the pulse at the heart during the onset of systole while listening for S 1 , coinciding with mitral and tricuspid valve closure [ , ].
The second sound (S 2 ) has two components that are associated with closure of the aortic valve (A 2 ) and pulmonary valve (P 2 ). The S 2 is best heard at the left upper sternal border and is described as a “dub” sound [ ]. Physiologic splitting of S 2 is a normal variant in young children and is best heard during inspiration because of changes in cardiac output during the normal respiration cycle [ ]. During inspiration, the diaphragm drops, and intrathoracic pressure is decreased, causing increased flow of air into the lungs, venous blood return to the right side of the heart, and flow through the pulmonary valve. This causes delayed closure of the pulmonary valve, which causes P 2 to be delayed and occur after A 2 [ ]. The splitting of S 2 is a result of the increased separation in time between A 2 and P 2 . In contrast, expiration is associated with increased intrathoracic pressure, decreased systemic venous return, and lower workload on the right heart; the A 2 and P 2 components of S 2 are heard as a single, unsplit sound because the aortic and pulmonary valves close more closely in time ( Fig. 1 ) [ , ].
7
Abnormal heart sounds
7.1
Widely split and fixed second heart sound (S 2 )
The widely split and fixed S 2 occurs when differences in pressure cause the pulmonary valve to stay open longer than normal relative to the aortic valve. This may occur as a result of volume overload from an atrial septal defect or partial anomalous pulmonary venous return, pressure overload from pulmonary regurgitation, electrical delay from right bundle branch block, or early aortic closure with mitral regurgitation [ ]. A split and fixed S 2 is a classic presentation for a child with an atrial septal defect because the increased volume of blood that flows into the right ventricle causes the pulmonary valve to close later than normal during inspiration and expiration. The widely split and fixed S 2 may be observed in some normal children with physiologic variation ( Fig. 1 ).
7.2
Single or narrowly split second heart sound (S 2 )
The single or narrowly split S 2 may be heard in patients with aortic or pulmonary valve replacement, pulmonary hypertension associated with earlier closure of the pulmonary valve because of increased back pressure on the valve, or aortic stenosis because the aortic valve may remain open longer. A single S 2 may signify the presence of only one semilunar valve in complex congenital heart disease such as pulmonary atresia, aortic atresia, or truncus arteriosus. The single S 2 may also occur when A 2 or P 2 may be dominant because of valvular pathology, replacement, or congenital orientation of the valve, such as transposition of the great arteries, severe pulmonary or aortic stenosis, or valve replacement [ , ]. Narrowing of S 2 also may be observed in a normal child.
7.3
Paradoxical split of second heart sound (S 2 )
In a paradoxical split of S 2 , the split of S 2 narrows or disappears during inspiration and widens during expiration. This is the opposite of what is normally heard and represents pathology that causes more marked shifts in A 2 or P 2 in conditions such as severe aortic stenosis, left bundle branch block, or Wolff-Parkinson-White syndrome type B [ , ]. The paradoxical split of S 2 may be heard optimally with the diaphragm of the stethoscope by timing the sound with respect to the respiratory cycle and by comparing the sound between inspiration and expiration [ , ].
7.4
Third heart sound (S 3 )
The third heart sound (S 3 ), also known as a ventricular gallop or protodiastolic gallop, is a low-frequency vibration sound in early diastole, which is the end of the early passive or rapid diastolic filling period of the right or left ventricle [ ]. It is best heard at the apex or left lower sternal border. The S 3 commonly may be heard in normal children and young adults but is considered abnormal when it is heard in patients with ventricular dilation or decreased compliance [ ]. Patients with an S 3 are evaluated for dilated cardiomyopathy. The S 3 may be heard optimally with the bell of the stethoscope for low-frequency sounds, the patient lying in left lateral decubitus position to bring the heart closer to the chest wall, and the examiner listening at the apex of the heart, typically at the left fifth intercostal space and midclavicular line. The S 3 may create a rhythm that mimics the sound of the syllable “ y” in the word Kentucky or a galloping horse ( Fig. 1 ) [ , ].
7.5
Fourth heart sound (S 4 )
The fourth heart sound (S 4 ), also known as an atrial gallop or presystolic gallop, occurs immediately before the normal S 1 and is best heard at the apex. The S 4 is associated with active atrial contraction at the end of diastole. The S 4 is pathologic and may be indicative of decreased ventricular compliance [ ]. The S 4 may be best heard with the bell of the stethoscope for low-frequency sounds, the patient lying in left lateral decubitus position to bring the heart closer to the chest wall, and the examiner listening at the apex of the heart, typically at the left fifth intercostal space and midclavicular line. The S 4 may be best heard by applying light pressure with the stethoscope, and it may create a rhythm that mimics the syllable “ ten” in the word Tennessee ( Fig. 1 ) [ ].
8
Innocent murmurs
Innocent murmurs are not associated with harmful conditions and do not require treatment. They often are described as musical or vibratory and soft, grade 1 to 2 murmurs. They usually are systolic, low-pitched, short murmurs heard at the left upper and lower sternal border. The four common innocent heart murmurs are the systolic Still’s, pulmonary flow, supraclavicular innocent murmurs, and diastolic venous hum ( Table 3 ) [ ].
