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Common causes of cardiac murmurs in infants and children

Common causes of cardiac murmurs in infants and children
Literature review current through: Jan 2024.
This topic last updated: Jan 27, 2023.

INTRODUCTION — Heart murmurs are common in infants and children. Being able to distinguish a murmur associated with heart disease from a benign etiology is important for diagnosis and management (table 1).

Common causes of heart murmurs in infants and children will be reviewed here. The approach to evaluating cardiac murmurs, identifying newborns with critical heart disease, and evaluating children with suspected heart disease are discussed separately:

(See "Approach to the infant or child with a cardiac murmur".)

(See "Identifying newborns with critical congenital heart disease".)

(See "Suspected heart disease in infants and children: Criteria for referral".)

Individual congenital heart defects are also discussed separately.

PREVALENCE OF HEART MURMURS AND RELATIONSHIP TO CARDIAC PATHOLOGY — Evaluation of a murmur is the most common reason for referral to a pediatric cardiologist [1,2]. While the reported prevalence of congenital heart disease is approximately 1 percent, a majority of children have innocent murmurs at some time during childhood [3,4]. One-third to three-quarters of children have an innocent murmur noted at some time between age 1 and 14 years, the most frequent of which is an innocent Still murmur [5-7]. In a cross-sectional study of >80,000 schoolchildren (age 5 to 13 years) in China, heart murmurs were detected in 3 percent [8]. Structural heart disease was found in 10 percent of the children with murmurs, with ventricular septal defect (VSD) being the most common lesion. The prevalence of structural heart disease declined with increasing age.

In a study of nearly 8000 first-time echocardiograms performed at a single pediatric center, cardiac pathology was noted in 20 percent of studies performed for evaluation of murmur (n = 4800) [9]. The diagnostic yield of echocardiography in this setting differed according to the expertise of the ordering clinician; cardiac pathology was detected in 32 percent of echocardiograms ordered by cardiologists compared with only 15 percent of those ordered by noncardiologists.

In another study of 222 patients referred to a pediatric cardiologist for a murmur, the prevalence of cardiac pathology was 33 percent [10]. The most common lesions were VSDs, pulmonary valve stenosis, and atrial septal defects (ASDs). The majority of children had innocent murmurs, including Still murmur (44 percent), benign flow murmurs (16 percent), venous hum (11 percent), and physiologic peripheral pulmonary stenosis (PPS; 6 percent). The cardiologist detected no murmur in 2 percent of referred patients.

Features that help distinguish pathologic lesions from innocent murmurs are discussed in greater detail separately. (See "Approach to the infant or child with a cardiac murmur", section on 'Distinguishing pathologic from innocent murmurs'.)

COMMON CAUSES OF MURMURS

Neonates and infants

Timing of onset — Murmurs present in the first six hours of life are usually associated with a valve problem, either regurgitation (tricuspid valve or mitral valve) or stenosis (aortic valve or pulmonary valve). Murmurs detected after six hours of age may also be due to valve pathology or may represent shunt lesions that appear as pulmonary vascular resistance falls (atrial and ventricular septal defect [ASD and VSD], patent ductus arteriosus [PDA], peripheral pulmonary stenosis [PPS]).

Patent ductus arteriosus — The ductus arteriosus closes in approximately 90 percent of full-term neonates by 48 hours of age. Prolonged patency of the ductus arteriosus occurs most commonly in premature infants and those born at altitude [11]. The murmur of PDA (figure 1) can be characterized as follows:

Location – It is best heard at the left upper sternal border.

Timing and quality – It is typically continuous throughout both phases of the cardiac cycle, is crescendo-decrescendo in shape, and has a rough machinery-type quality (movie 1).

Other sounds – Frequently, there are multiple clicks audible throughout the murmur, which likely arise from wave-like expansion of the pulmonary artery. In infants with a large left-to-right shunt, there can be a diastolic rumble at the apex representing "relative mitral stenosis" caused by an increased volume traversing the mitral valve. In premature infants, there often is only a systolic murmur. In children with persistent large PDAs and elevated pulmonary artery pressure, the second heart sound (S2) is loud and single and there may be no audible murmur (movie 2).

The clinical features and diagnosis of PDA are discussed in greater detail separately. (See "Clinical manifestations and diagnosis of patent ductus arteriosus (PDA) in term infants, children, and adults" and "Patent ductus arteriosus (PDA) in preterm infants: Clinical features and diagnosis".)

Tricuspid regurgitation — Tricuspid regurgitation in newborns is most commonly seen in neonates with low Apgar scores and is associated with transient papillary muscle dysfunction due to birth asphyxia. Tricuspid regurgitation also occurs in pulmonary atresia and Ebstein anomaly. (See "Ebstein anomaly: Clinical manifestations and diagnosis".)

The murmur of tricuspid regurgitation can be characterized as follows:

Location – It is best heard at the left lower sternal border

Timing and quality – It is typically holosystolic and has a blowing quality

In neonates with birth asphyxia, the murmur typically becomes softer in the first few days of life associated with normal pulmonary vasodilation in the neonatal transition period, reduction in right ventricular systolic pressure, and return of normal papillary muscle function. (See "Physiologic transition from intrauterine to extrauterine life", section on 'Circulatory changes'.)

Ventricular septal defects — VSD murmurs can be characterized as follows:

Location – They are usually best heard at the left lower sternal border. Patients with subpulmonic (outlet) VSDs (figure 2) can have maximum intensity of the murmur higher on the left sternal border.

Timing and quality – The size and type of the VSD determine the characteristics of the murmur:

Small muscular VSDs – A small defect in the muscular portion of the interventricular septum produces a characteristic high-frequency, short systolic murmur that does not extend to S2, because the defect closes as the ventricle contracts (movie 3). Many of these defects spontaneously fully close in the first year of life. (See "Isolated ventricular septal defects (VSDs) in infants and children: Anatomy, clinical features, and diagnosis", section on 'Small ventricular septal defect'.)

Other VSDs – Membranous, malalignment, and moderate or large muscular VSDs (figure 2) produce a holosystolic harsh murmur (movie 4). If there is a large amount of left-to-right shunting, an apical diastolic murmur may be heard. This represents "relative mitral stenosis" caused by the increased pulmonary venous return that crosses the mitral valve.

Other sounds – An apical third heart sound (S3) may be heard if there is a large left-to-right shunt. In the setting of a loud systolic murmur, the quality of S2 helps distinguish between a small or large VSD (a single loud S2 suggests a large defect) (algorithm 1). (See "Isolated ventricular septal defects (VSDs) in infants and children: Anatomy, clinical features, and diagnosis".)

VSDs are the most common causes of murmurs detected in the newborn nursery [12]. The murmur associated with a VSD occurs as pulmonary vascular resistance decreases in the neonatal transition period and, therefore, is not typically present in the first few hours of life. In small defects, the intensity of the murmur becomes louder as pulmonary vascular resistance decreases during the neonatal period and early infancy, resulting in a larger pressure gradient between the ventricles. In large defects, the murmur intensity may increase due to increased left-to-right shunting. (See "Physiologic transition from intrauterine to extrauterine life", section on 'Circulatory changes'.)

The clinical features and diagnosis of VSDs in infants and children are discussed in detail separately. (See "Isolated ventricular septal defects (VSDs) in infants and children: Anatomy, clinical features, and diagnosis".)

Peripheral pulmonary stenosis — The PPS murmur is a common functional murmur that occurs in early infancy as pulmonary vascular resistance decreases. The PPS murmur can be characterized as follows:

Location – It is heard best at the upper left or right sternal border with radiation to the axillae and back

Timing and quality – It is typically a grade 1 to 2, medium- to high-pitched midsystolic ejection murmur

The PPS murmur is caused by turbulent flow in the proximal pulmonary arteries associated with their relative size or angle of take-off from the main pulmonary artery [13]. This murmur usually resolves by age 6 to 12 months.

Pulmonary stenosis — The murmur of pulmonary stenosis (PS) can be characterized as follows:

Location – It is heard best at the left upper sternal border.

Timing and quality – It is a midsystolic ejection murmur that is harsh in quality (movie 5). If cardiac output is normal, the murmur becomes louder the greater the degree of obstruction; however, if there is right ventricular dysfunction, the murmur can be soft despite the presence of moderate or severe obstruction.

Other sounds – Greater degrees of valve obstruction are associated with less intense pulmonary component of S2. The murmur is accompanied by a variable early systolic ejection click that is more prominent in expiration. The ejection click is not present with more severe obstruction, because of limited valve excursion.

The clinical features and diagnosis of PS are discussed in greater detail separately. (See "Pulmonic stenosis in infants and children: Clinical manifestations and diagnosis".)

Aortic stenosis — The murmur produced by aortic valve stenosis (AS) can be characterized as follows:

Location – It is loudest at the right upper sternal border that radiates to the carotid arteries.

Timing and quality – It is a harsh midsystolic ejection murmur (movie 6). The intensity depends on the severity of obstruction and the cardiac output. Moderate to severe AS produces a loud murmur when cardiac output is normal and a soft murmur when cardiac output is reduced. The timing of the murmur also depends on the severity of obstruction; in severe AS, the murmur peaks later in systole.

Other sounds – The murmur is accompanied by an early, constant systolic click that is best heard at the apex (movie 7). The click becomes softer or is absent as stenosis increases due to decreased mobility of the valve.

Thrill – A systolic thrill may be palpable in the suprasternal notch even in patients with only mild to moderate obstruction. The presence of such a thrill helps to distinguish this murmur from PS. A precordial thrill at the right upper sternal border is required for assignment of a grade 4 murmur (table 2).

AS in pediatric patients is most commonly associated with a bicuspid aortic valve (see 'Bicuspid aortic valve' below), but, as an isolated lesion, it is rarely diagnosed in infancy. The clinical features and diagnosis of AS in children are discussed in greater detail separately. (See "Valvar aortic stenosis in children".)

Coarctation of the aorta — The murmur of coarctation of the aorta (CoA) (figure 3) can be characterized as follows:

Location – It is best heard on the back between the scapulae, which is near the region of the aortic isthmus where coarctation typically occurs. Occasionally, the murmur may be heard in the left infraclavicular region, which is close to the distal portion of the transverse arch.

Timing and quality – The murmur produced by the narrowing itself is systolic murmur with the intensity directly related to the degree of obstruction and cardiac output. Patients with longstanding, significant CoA develop collateral arteries to bypass the obstruction, and these create a continuous murmur in the lateral portion of the chest.

Additional findings that are suggestive of CoA include weak femoral pulses, systemic hypertension, or systolic pressure gradient >10 mmHg between the right arm and leg. The clinical manifestations and diagnosis of CoA are discussed in greater detail separately. (See "Clinical manifestations and diagnosis of coarctation of the aorta".)

Other congenital heart lesions — Murmurs are audible in many other congenital heart disease lesions (table 3):

Patients with tetralogy of Fallot typically have a systolic murmur caused by PS. (See "Tetralogy of Fallot (TOF): Pathophysiology, clinical features, and diagnosis" and 'Pulmonary stenosis' above.)

A soft, outflow systolic murmur is heard in pulmonary atresia with intact ventricular septum, hypoplastic left heart syndrome, or truncus arteriosus. In all of these lesions, the cardiac output crosses a single semilunar valve and the volume of blood flow causes the associated murmur. Some patients with truncus arteriosus also have a diastolic murmur of truncal valve regurgitation. (See "Pulmonary atresia with intact ventricular septum (PA/IVS)" and "Hypoplastic left heart syndrome: Anatomy, clinical features, and diagnosis" and "Truncus arteriosus".)

Pulmonary atresia is often associated with a systolic murmur caused by tricuspid regurgitation. (See 'Tricuspid regurgitation' above.)

Tricuspid atresia is usually associated with a murmur when accompanied by PS and VSD. (See 'Pulmonary stenosis' above and 'Ventricular septal defects' above and "Tricuspid valve atresia".)

The tricuspid valve in Ebstein anomaly is nearly always regurgitant and produces a systolic murmur at the left lower sternal border. (See 'Tricuspid regurgitation' above and "Ebstein anomaly: Clinical manifestations and diagnosis".)

Children >1 year — Murmurs detected after infancy most often represent innocent murmurs but can also be produced by semilunar valve stenosis, atrioventricular valve regurgitation, or ASDs. Other congenital heart lesions are unlikely to present at this age unless access to medical care was limited during infancy.

Innocent Still murmur — The innocent Still murmur is characterized as follows:

Location – It has maximum intensity at the left lower sternal border or between the left lower sternal border and apex, with minimal radiation.

Timing and quality – It is a systolic murmur with a characteristic vibratory or musical quality (movie 8). It is louder in the supine than in the sitting position, is louder in hyperdynamic states (fever, anxiety), and usually is grade 1 or grade 2 in intensity.

This murmur usually resolves by early adolescence, if not sooner. The anatomic basis for the murmur has not been definitively determined.

Cervical venous hum — A cervical venous hum is another common innocent murmur in children. It is characterized as follows:

Location – It is heard best at the left or right upper sternal borders or infraclavicular or supraclavicular regions.

Timing and quality – It is a continuous murmur that is loudest when the patient is sitting with the head extended (movie 9). It becomes softer or absent when the patient is supine, with rotation or flexion of the head, or when applying light pressure over the jugular vein with the patient in a sitting position. The alteration of the murmur's intensity with these maneuvers aids in distinguishing the murmur from a PDA.

Atrial septal defect — The murmur associated with an ASD can be characterized as follows:

Location – The systolic murmur is heard best at the left upper sternal border; the diastolic murmur, if present, is best heard at the left lower sternal border.

Timing and quality – The systolic murmur is usually soft (grade 1 to 2) (movie 10) and represents "relative stenosis" created by increased flow across the pulmonary valve due to right ventricular volume overload from left-to-right shunting. If the pulmonary annulus dilates along with the right ventricle, the murmur is softer or absent. If there is a large amount of left-to-right shunting, there may be a soft diastolic murmur created by increased flow across the tricuspid valve (movie 11).

Other sounds – In some patients, the only abnormality on cardiac examination is a fixed and widely split S2 (movie 10) [10].

Symptoms associated with ASDs are uncommon in childhood, and the cardiac findings can be subtle. As a consequence, some ASDs are not detected until adulthood [14]. The clinical features and diagnosis of ASDs are discussed in greater detail separately. (See "Isolated atrial septal defects (ASDs) in children: Classification, clinical features, and diagnosis".)

Mitral regurgitation — The murmur of mitral regurgitation (MR) is characterized as follows:

Location – It is heard best at the apex and radiates to the axilla.

Timing and quality – It is usually holosystolic and blowing in quality (movie 12). In patients with mitral valve prolapse, the murmur may occur in mid- or late systole (movie 13). With moderate or severe regurgitation, there can be an apical diastolic murmur of "relative mitral stenosis" due to the increased volume crossing the mitral valve. The intensity of the murmur depends on ventricular function so that, in patients with reduced function, the murmur is softer.

Other sounds – A midsystolic click may be heard in patients with mitral valve prolapse (movie 13). With severe MR, an S3 may be heard.

MR can occur as a consequence of the following acute or chronic cardiac conditions, which are discussed in greater detail separately [15]:

Acute rheumatic fever (see "Clinical manifestations and diagnosis of rheumatic heart disease")

Mitral valve prolapse (see "Mitral valve prolapse: Clinical manifestations and diagnosis")

Myocarditis or endocarditis (see "Clinical manifestations and diagnosis of myocarditis in children" and "Infective endocarditis in children")

Cardiomyopathy and chronic heart failure (see "Heart failure in children: Etiology, clinical manifestations, and diagnosis" and "Definition and classification of the cardiomyopathies")

Kawasaki disease (see "Cardiovascular sequelae of Kawasaki disease: Clinical features and evaluation")

Coronary artery anomalies (anomalous origin of the left coronary artery from the main pulmonary artery) (see "Congenital and pediatric coronary artery abnormalities")

Trauma (ruptured chordae tendineae) (see "Initial evaluation and management of blunt cardiac injury")

Bicuspid aortic valve — Bicuspid aortic valve is the most common congenital heart lesion, with an estimated prevalence of 0.5 to 2 percent. The characteristic finding in bicuspid aortic valve is an ejection click:

Ejection click – The ejection sound is an early, constant systolic click best heard at the apex (movie 7). It may be difficult to distinguish the ejection click from a split first heart sound (S1).

Associated murmurs – Bicuspid aortic valves can be associated with AS with its characteristic murmur (movie 6). Bicuspid aortic valves can also be associated with aortic regurgitation. This diastolic murmur is best heard at the left upper sternal border, is decrescendo in shape, and is blowing in quality (movie 14). The murmur is usually easier to hear with the patient sitting rather than supine. The extent of radiation of the murmur usually correlates with severity, with mild limited to the left upper sternal border, moderate audible also at the left midsternal border, and severe regurgitation audible to the left lower sternal border.

The clinical features and diagnosis of bicuspid aortic valve are discussed in greater detail separately. (See "Clinical manifestations and diagnosis of bicuspid aortic valve in adults".)

Pericarditis — A pericardial friction rub occurs when inflamed visceral and parietal pericardial surfaces rub against each other; the rub is typically absent if there is a large pericardial effusion. A friction rub can be characterized as follows:

Location – It is usually heard best at the left sternal border during inspiration with the patient sitting and leaning forward.

Timing and quality – It is generally present in both systole and diastole. The sound has a scratching quality similar to rubbing two pieces of sandpaper together (movie 15).

Viral infection and postpericardiotomy syndrome are the most common etiologies of pericarditis in children, though there are many other etiologies. (See "Acute pericarditis: Clinical presentation and diagnosis" and "Post-cardiac injury syndromes".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or email these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient education" and the keyword[s] of interest.)

Basics topic (see "Patient education: Heart murmurs (The Basics)")

SUMMARY

Prevalence – Heart murmurs are common in infants and children, with approximately one-third to three-quarters of children having an innocent murmur noted at some time between age 1 and 14 years. Only a minority of patients with murmurs have heart disease. The association of murmurs with underlying heart disease is higher in infancy and decreases with age during childhood and adolescence. Being able to distinguish a murmur associated with heart disease from a benign etiology is important for diagnosis and management (table 1). (See 'Prevalence of heart murmurs and relationship to cardiac pathology' above and "Approach to the infant or child with a cardiac murmur", section on 'Distinguishing pathologic from innocent murmurs'.)

Causes – Common causes of murmurs vary by age.

Neonates and infants – Murmurs present in the first six hours of life are usually associated with valve pathology. Murmurs detected after six hours of age may also be due to valve pathology or may represent shunt lesions that appear as pulmonary vascular resistance falls. Specific causes of murmurs in neonates and infants include (see 'Neonates and infants' above):

-Patent ductus arteriosus (PDA) (movie 1) (see 'Patent ductus arteriosus' above and "Clinical manifestations and diagnosis of patent ductus arteriosus (PDA) in term infants, children, and adults")

-Tricuspid regurgitation (see 'Tricuspid regurgitation' above)

-Ventricular septal defects (VSDs) (movie 4 and movie 3) (see 'Ventricular septal defects' above and "Isolated ventricular septal defects (VSDs) in infants and children: Anatomy, clinical features, and diagnosis")

-Peripheral pulmonary stenosis (PPS) (see 'Peripheral pulmonary stenosis' above)

-Aortic stenosis (movie 6) (see 'Aortic stenosis' above and "Valvar aortic stenosis in children")

-Coarctation of the aorta (CoA) (see 'Coarctation of the aorta' above and "Clinical manifestations and diagnosis of coarctation of the aorta")

-Other congenital heart lesions (see 'Other congenital heart lesions' above)

Children >1 year old – Murmurs detected after infancy most often represent innocent murmurs but can also be produced by semilunar valve stenosis, atrioventricular valve regurgitation, or atrial septal defects (ASDs). Specific causes include (see 'Children >1 year' above):

-Innocent Still murmur (movie 8) (see 'Innocent Still murmur' above)

-Cervical venous hum (movie 9) (see 'Cervical venous hum' above)

-ASD (movie 10) (see 'Atrial septal defect' above and "Isolated atrial septal defects (ASDs) in children: Classification, clinical features, and diagnosis")

-Mitral regurgitation (MR) (movie 12) (see 'Mitral regurgitation' above)

-Bicuspid aortic valve (movie 7) (see 'Bicuspid aortic valve' above)

-Pericarditis (movie 15) (see 'Pericarditis' above and "Acute pericarditis: Clinical presentation and diagnosis")

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