INNOCENT HEART MURMURS
DEFINITION:
Heart murmurs that occur in the absence of anatomical or
physiological abnormalities of the heart and therefore have no
clinical significance.
EPIDEMIOLOGY:
- incidence: 50% of children
- age of onset:
- heard most frequently from 3-8 years of age
- risk factors:
TYPES (5):
- mechanism: caused by vibration of the AV valves, ventricular
wall and/or the chordae tendinae (represents a LV outflow
murmur); also due to the friction of RBC's against cardiac
muscle
- most common in 3-8 year olds
- most common innocent murmur
2. Venous Hum
- mechanism: blood flows down from collapsed cervical veins to
dilated intrathoracic veins causing the venous walls to flutter
thus producing a low-pitched murmur
- most common in 3-8 year olds
- R-sided in 50%, L-sided in 30%, and bilateral in 20%
3. Pulmonary Ejection Murmur
- also called 'Pulmonary Flow Murmur', 'Basal Ejection
Systolic Murmur', or 'Physiologic Pulmonary Systolic Ejection
Murmur'
- mechanism: at the beginning of systole, blood above the
pulmonic valve is stationary but is then sheared away from the
artery walls when blood is ejected from the right ventricle
- most common in 3-8 year olds
4. Carotid Bruit
- also called 'Supraclavicular Arterial Bruit'
- mechanism: turbulance in the carotid arteries as the blood
is accelerated early in systole
- most common in 3-8 year olds
- bilateral in 62%, R-sided in 24%, and L-sided in 14%
5. Peripheral Pulmonary (Artery) Stenosis
- mechanism: when the right and left pulmonary arteries veer
off from the main pulmonary artery at sharp angles, turbulance
is produced during systole
- most common during the 1st year of life then disappears
PATHOPHYSIOLOGY:
- most innocent heart murmurs are produced by the forward flow
of blood forming turbulence in the chambers of the heart or the
great vessels and because the murmur intensity parallels the
ejection velocity of blood from the ventricles, innocent murmurs
usually occur during early-mid systole, are short in duration,
have a crescendo-decrescendo contour (ejection murmur), are <3/6
in intensity and are never diastolic
CLINICAL FEATURES:
- usually found on routine physical examination
2. Signs
- 1st half to 2/3rd's of systolic phase
- diamond-shaped, grade <3/6
- quality: low-pitched musical or vibratory in nature
- maximal: over 2nd-4th L intercostal space lateral to the
LLSB midway between the sternal border and apex
- radiat.: to the apex, aortic, and pulmonary areas
- loudest: in supine position, with exercise and fever
- dd: VSD, MI, Subaortic Stenosis
2. Venous Hum
- continous murmur, grade <3/6
- quality: low-pitched
- maximal: supraclavicular fossa
- radiat.: to the aortic and pulmonary areas
- loudest: standing with chin tilted up (disappears in
supine position with the head flexed, by compressing the
external jugular vein)
- dd: PDA, AVM
3. Pulmonary Ejection Murmur
- 1st half to 2/3rd's of systolic phase with peak at mid
systole finishing by S2
- diamond-shaped, grade <3/6
- quality: high-pitched blowing
- maximal: over pulmonic area (2nd L parasternal space)
- radiat.: to LLSB, L axillae, left side of neck and
slightly to the aortic area
- loudest: with high cardiac output (exercise, fever), and
in the supine position
- dd: ASD, PS, Hypertension (systemic or pulmonary)
4. Carotid Bruit
- early systolic lasting 1/3->1/4 of systolic phase
- diamond-shaped, grade <3/6
- quality: high-pitched blowing with systoic thrill over the
the carotid vessels
- maximal: over the carotid vessels or supraclavicular fossa
- radiat.: below the clavicle to the aortic or pulmonary
areas
- loudest: with high cardiac output (exercise, fever),
sitting (disappears when elbows are flexed and shoulders
hyperextended)
- dd: AS, Stenosis of Carotid Vessels, Intracranial AVM
5. Peripheral Pulmonary (Artery) Stenosis
- midsystolic and short
- diamond-shaped, grade <3/6
- quality: high-pitched blowing
- maximal: over pulmonic area (2nd L parasternal space)
- radiat.: along the pulmonary arterial tree so can be heard
over both axillae, the aortic area, and in the back
- dd: ASD, PDA, coarctation of the pulmonary artery
INVESTIGATIONS:
2. ECG
3. 2D-Echo
MANAGEMENT:
- no treatment, reassurance
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