INNOCENT HEART MURMURS

 

 

Return to: 

Heart Diseases in Children - Main Page 

Pediatric Cardiology for Medical Professionals 

Pediatric Cardiology for Patients & Parents

 

 Heart murmurs is a common finding on routine examination of infants and children.   50% of normal children have an innocent heart murmur.

How to evaluate a murmur?

Search for symptoms or signs of congenital heart disease.  Patients with innocent heart murmurs should be free of such symptoms or signs.

Therefore, when history is obtained and during physical examination symptoms and signs which may point to heart disease should be identified.   The presence of symptoms and/or signs of heart disease will suggest the pathological nature of the heart murmur being investigated.

History

Abnormal findings indicating a pathological orgin of a heart murmur include:

Shortness of Breath (SOB):

This results from pulmonary edema due to increased pulmonary blood flow.  Fluid escaping the engorged pulmonary vasculature will interfere with normal gaseous exchange, resulting in hypoxia which precipitates tachypnea and SOB, particularly with exertion such as feeding.

Easy fatigue:

This results from pulmonary edema and poor cardiac output.

Failure to thrive (FTT):

Poor feeding secondary to pulmonary edema and poor cardiac output as well as increased caloric expenditure due to tachycardia and tachypnea will eventually lead to FTT.   This will initially manifest as poor weight gain, followed by poor length progression.

Cyanosis:

Cyanosis is bluish discoloration of the oral mucosa and nail beds.  This is caused by higher than normal concentration of deoxygenated hemoglobin which is blue in color.

Case Hgb concentration Oxygen saturation or % oxygenated Hgb % Deoxygenated Hgb Concentration of deoxygenated Hgb Findings
1 14 g/dl 95% 5% 0.7 g/dl Pink mucosa
2 14 g/dl 85% 15% 2.1 g/dl Cyanosis
3 6 g/dl 85% 15% 0.9 Pink mucosa
4 28 g/dl 95% 5% 1.4 g/dl Cyanosis

The level of deoxygenated hemoglobin in the blood is more important in determining the change in mucosa color.  As the examples shown in the above table a child with cyanotic congestive heart failure, however, with severe anemia may not be cyanotic, because the level of deoxygenated hemoglobin in the blood (case 3)is not high enough to give cyanosis.  On the other hand polycythemia (case 4) may be normally saturated by pulse oxymeter, however the small percentage of deoxygenated Hgb may be significant enough to cause cyanosis.

 

Physical examination

 

Abnormal findings indicating a pathological orgin of a heart murmur include:

Inspection

Cyanosis:

This is best determined by examining the patient in sunlight.  Artificial light may alter patient color.

Clubbing:

This is enlargement of the tips of digits caused by hypoxia to peripheral tissue due to poor cardiac output and/or cyanosis.  Peripheral tissue compensate by forming more capillaries to improve oxygenation, this results in swelling of the peripheries of digits.   Clubbing of digits at its mildest form is noted when the normally seen angle at the skin-nail junction, and its worse condition the digit assume a drum-stick appearance.   Clubbing is also seen in other diseases associated with tissue hypoxia such as lung diseases and hepatic and intestinal diseases such as Crohn's disease and ulcerative colitis due to anemia.  Familial clubbing is also known to occur.

palpation

Pulses:

Pulses are the result of difference between systolic and diastolic status of the vasculature.  Increase in the difference between systole and diastole results in a more pronounced pulse.

Normal pulse pressure Wide pulse pressure
Narrow pulse pressure

Pulses should be easily palpable and equal in their intensity throughout the body.   Generalized week pulses is suggestive of poor cardiac output either due to severe heart failure or severe aortic stenosis.  Better pulses in the upper upper extremities than the lower extremities is suggestive of coarctation of the aorta.   Bounding (also known as water hammer) pulses are seen in patients with a low diastolic pressure due to aortic regurgitation or presence of a systemic to pulmonary arterial connection such as patent ductus arteriosus, collaterals or a surgically placed shunt such as Blalock-Taussig shunt.

Liver edge:

Hepatomegaly may reflect a high right atrial pressure associated with congestive heart failure.

Precordium:

The precordium should be normally quiet.  Hyperdynamic circulation due to increase pulmonary blood flow or  RVH or LVH will cause prominence of the RV and/or LV impulses.  Palpable thrill is felt when the heart murmur is 4/6 or louder.   Prominent cardiac impulses or a thrill indicate pathology.

Auscultation

Heart Sounds:  Heart sounds in innocent heart murmurs are normal.   First heart sound should be audible.  Second heart sound should split in inspiration and become single in expiration.  Single second heart sound, or variation in splitting such as fixed splitting or reverse splitting, i.e. split in expiration and single in inspiration indicate pathology.

In addition the quality of the pulmonary component of the second heart sound (the second component) should be evaluated, a loud P2 indicate pulmonary hypertension.

Added sounds such as S4 is pathological.  S3 may be normal.

Murmurs:  Innocent heart murmurs are typically 2/6 or 1/6 in intensity, rarely they are 3/6, but never louder.  Innocent heart murmurs could be systolic and diastolic such as in venous hum, but never purely diastolic.  A typical innocent heart murmur is vibratory (or musical) in quality.  Harsh murmurs indicate pathology.

Maneuvers with auscultation

Supine, sitting and standing:  Increase pre-load in supine.........exaggerating flow murmurs

Valsalva maneuver:

Increase intensity of MVP

Decrease intensity of innocent heart murmurs

Respiratory cycle

Inspiration......increase blood flow to right heart

Expiration........increase blood flow to left heart

 

Features of innocent heart murmurs

The term innocent was first used by William Evans in 1943.  Also known as normal, functional, inorganic, innocuous, dynamic or benign.  More than 50% of all children have innocent heart murmurs.  Innocent heart murmurs are due to turbulent blood flow at the origin of the great vessels. It is better heard in children than in adults due to:

Thin chest wall in children

More angulated great vessels in children

More dynamic circulation in children

 

Types of innocent murmurs

Still’s murmur:

Due to blood flow across the aortic valve.  Heard best over the right upper sternal border.  It is a

systolic ejection murmur, vibratory, musical in quality.  Seen in infancy to adolescence

 

Physiologic systolic ejection murmur;

Second most common. Hear best at the left mid to upper sternal border.  Heard best with diaphragm due to high frequency

 

Supraclavicular arterial bruit:

Above and not below the clavicle.  Louder on right due to brachiocephalic arteries branching

 

Neonatal peripheral pulmonary stenosis(PPS):

Birth to 3-6 months.  Heard best at base of the heart, both axillae and the back.   Due to relative small size of branch pulmonary arteries and the angle of bifurcation of the PAs

Cervical venous hum;

Continuous hum.  Heard over right upper sternal border.  Better in sitting, disappear in supine and when pressure is applied to neck to reduce venous blood return.

Mammary soufflé:

Noted in lactating mothers, due to increase mammary blood flow.

 

Features of pathological murmurs

  1. All diastolic murmurs
  2. All pansystolic murmurs
  3. Late systolic murmurs
  4. Loud murmurs > 3/6
  5. Continuous murmurs
  6. Associated cardiac abnormalities

 

REFERENCES

1. How to distinguish between innocent and pathologic heart murmurs in children. Rosenthal, A. The pediatric Clinics of North America, Dec 1984, page 129.

2. Innocent Murmurs. Newburger, J W. Nadas’ Pediatric Cardiology, page 281.