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What is a heart murmur?

A heart murmur is the sound produced when blood flowing through the heart is turbulent. The flow of blood is usually smooth, however, abnormalities may cause turbulence, which creates a sound (murmur).

Causes of heart murmurs

Blood flowing through an abnormal narrowing (e.g. aortic stenosis, mitral stenosis, pulmonary stenosis)

 

Blood flowing in the wrong direction through the heart, and mixing with blood flowing in the normal direction (e.g. mitral regurgitation, tricuspid regurgitation)

 

An abnormal connection between two different parts of the heart (e.g. atrial septal defect, patent ductus arteriosus). Blood flows across this abnormal connection causing either:

1. Mixing of blood going in different directions

2. Too much blood flowing into another heart chamber 

 

Blood flowing faster through the heart (e.g. functional murmurs in sepsis and thyrotoxicosis)

 

Transmitted heart murmurs

A structural defect in the heart will result in turbulent blood flow, creating a murmur. Blood flow remains turbulent after it passes across the structural defect and thus the murmur will continue to be heard in the direction that turbulent blood is flowing. Therefore some murmurs are transmitted from the primary structural defect in the direction the blood is flowing.

Examples of murmurs that are transmitted

  • Aortic stenosis – radiates to the carotid arteries
  • Mitral regurgitation – radiates to the axilla

Cardiac cycle

Systole

1. Ventricles contract

2. Aortic and pulmonary valves open to allow blood to flow through – narrowing of either the aortic or pulmonary valve causes a systolic murmur

3. Mitral and tricuspid valves close shut to prevent blood flowing backwards through these valves – backwards flow of blood (regurgitation) through the mitral or tricuspid valves causes a systolic murmur

 

Diastole

1.  Ventricles and atria relax at the start of diastole (early diastole)

2. Aortic and pulmonary valves shut to prevent blood from flowing backwards through these valves – abnormal backflow of blood through the aortic or pulmonary valves causes an early diastolic murmur

3. Atria contract towards the end of diastole (mid or late-diastole)

4. Mitral and tricuspid valves open to allow blood flow to ventricles – narrowing of mitral or tricuspid valve causes a mid, late or end-systolic murmur


Heart sounds

S1 (first heart sound)

  • Caused by the closure of the mitral and tricuspid valves
  • Denotes the start of systole
  • Peripheral pulse will be felt at the same time or just after S1

 

S2 (second heart sound)

  • Caused by the closure of the aortic and pulmonary valves
  • Denotes the end of systole and start of diastole
  • The pulmonary valve may close just after the aortic valve:
    • Closure of the pulmonary valve just after the aortic valve is prolonged during inspiration, or in defects which cause more blood to be pumped out of the right ventricle.
    • Therefore S2 may not always be heard as one discrete sound but may be muffled or have two discrete sounds

Identifying the cause of a heart murmur

When during the cardiac cycle is the murmur heard?

Systole

  • Aortic and pulmonary stenosis
  • Mitral and tricuspid regurgitation
  • Mitral valve prolapse gives a systolic murmur with an opening click

 

Early diastole

  • Aortic and pulmonary regurgitation

 

Mid/late-diastole

  • Mitral and tricuspid stenosis

 

What are the characteristics of the murmur?

Systolic murmurs

Ejection systolic (crescendo-decrescendo)

  • Aortic and pulmonary stenosis

 

Pansystolic

  • Mitral and tricuspid regurgitation

 

Other causes of ejection systolic murmurs

Aortic sclerosis and hypertrophic obstructive cardiomyopathy (HOCM):

  • Both are loudest in the aortic valve area, during expiration
  • Aortic stenosis radiates to the carotids, whereas HOCM and aortic sclerosis do not

 

Atrial septal defects and pulmonary stenosis:

  • Both are loudest in the pulmonary region
  • Atrial septal defects cause wide and fixed splitting of S2 whereas pulmonary stenosis does not

 

Is the murmur heard loudest using the bell or the diaphragm of the stethoscope?

 

High pitched murmurs

  • Loudest with the diaphragm

 

Low pitched murmurs (e.g. mitral regurgitation)

  • Heard better with the bell

 

Where is the murmur heard the loudest?

Usually, murmurs are heard loudest in the region of the valve affected.

 

Aortic area

  • 2nd intercostal space right sternal edge

 

Pulmonary area

  • 2nd intercostal space left sternal edge

 

Tricuspid area

  • 4th intercostal space left sternal edge

 

Mitral area

  • Cardiac apex (usually 5th intercostal space in the left midclavicular line)

 

Do any manoeuvres exaggerate the murmur?

 

Aortic valve

  • Sitting forward brings the aortic valve closer to the chest wall, thus aortic murmurs are heard louder while sitting forward

 

Mitral valve

  • Left lateral decubitus position brings the apex closer to the chest wall, thus mitral valve murmurs are heard loudest in this position.

 

Heard loudest on inspiration or expiration?

 

Inspiration

  • Intrathoracic pressure reduces, so more blood flows into the right heart chambers
  • Right-sided valve lesions (pulmonary and tricuspid valves) are heard loudest during inspiration

 

Expiration

  • Intrathoracic pressure increases, forcing pulmonary vessels to constrict, so blood is forced from pulmonary veins into the left atrium and through the left side of the heart
  • Left-sided heart valve lesions (aortic and mitral valves) are heard loudest during expiration

 

Does the murmur radiate?

Some murmurs may radiate depending on the direction the turbulent blood flows.

Aortic stenosis

  • Radiates to the carotid artery

 

Mitral regurgitation

  • Radiates to the axilla

 

Aortic regurgitation

  • Radiates to the left sternal edge (usually heard best at the left sternal edge and not in the aortic valve region)

 

Pulmonary stenosis

  • Radiates to the left shoulder/ infra-clavicular region

 

Other features on peripheral examination?

  • Pulse character and pulse pressure (the difference between the systolic and diastolic blood pressure)
  • Location of apex beat
  • Jugular venous pressure (JVP) abnormalities
  • Signs of heart failure

Aortic stenosis

Typical description

  • Ejection systolic murmur
  • Heard loudest over aortic area
  • Radiates to carotid arteries
  • Loudest on expiration and sitting forward
  • Slow rising pulse with narrow pulse pressure
  • Non-displaced, heaving apex beat (if present indicates left ventricular hypertrophy)
  • Reduced or absent S2 (sign of moderate-severe aortic stenosis)
  • Reverse splitting of S2 – aortic valve closes after pulmonary valve (due to the longer time required for blood to exit the left ventricle)

 

Causes

  • Degenerative age-related calcification (commonest cause)
  • Bicuspid aortic valve (important cause in a young person with aortic stenosis)

Mitral regurgitation

Typical description

  • Pansystolic murmur
  • Heard loudest over mitral area
  • Radiates to axilla
  • Heard loudest using the bell of the stethoscope
  • Loudest on expiration in the left lateral decubitus position
  • Displaced, hyperdynamic apex beat

 

Causes

  • Degenerative
  • Left ventricular dilatation (the space between the left atrium and ventricle becomes dilated meaning the mitral valve is no longer able to close this gap)
  • Ruptured chordae tendinae
  • Papillary muscle rupture
  • Rheumatic heart disease
  • Infective endocarditis
  • Mitral valve prolapse
  • Connective tissue disease e.g. Marfan syndrome, Ehlers-Danlos syndrome

Aortic regurgitation

  • After ventricular systole, the aortic valve closes to prevent blood from flowing back into the left ventricle from the aorta
  • In aortic regurgitation, blood flows back/regurgitates into the left ventricle after ventricular systole
  • This causes a sudden, abrupt drop in blood pressure after ventricular contraction, and thus a sudden drop in arterial pressure with a subsequent collapse of arterial vessel walls
  • This gives the characteristic collapsing pulse and accounts for the associated findings listed below

 

Typical description

  • Decrescendo early diastolic murmur
  • Heard loudest at left sternal edge (the direction that turbulent blood flows) – sometimes heard loudest over the aortic area
  • Collapsing pulse (i.e. water hammer pulse with wide pulse pressure)
  • Displaced, hyperdynamic apex beat
  • Austin Flint murmur (sign of severe aortic regurgitation) – low pitched rumbling mid-diastolic murmur heard best at the apex
    • Caused by the regurgitated blood through the aortic valve mixing with blood from the left atrium, during atrial contraction.

 

Associated findings

  • Corrigan’s sign – visible distention and collapse of carotid arteries in the neck
  • De Musset’s sign – head bobbing with each heartbeat
  • Quincke’s sign – pulsations are seen in the nail bed with each heartbeat when nail bed is lightly compressed
  • Duroziez’s sign – stethoscope placed over femoral arteries. When gentle pressure is applied proximal to the stethoscope a systolic murmur is heard; when gentle pressure is applied distal to the stethoscope a diastolic murmur is heard (as blood flows backwards)
  • Traube’s sign – ‘Pistol shot’ sound heard when stethoscope placed over the femoral artery during systole and diastole
  • Muller’s sign – Uvula pulsations are seen with each heartbeat

 

Causes

  • Ascending aortic arch dissection
  • Infective endocarditis
  • Chest trauma
  • Prosthetic aortic valve failure
  • Connective tissue disease (e.g. Marfan syndrome, Ehlers-Danlos syndrome)
  • Rheumatological disorders
    • Seronegative spondyloarthropathies (e.g. ankylosing spondylitis)
    • Takayasu arteritis, rheumatoid arthritis, SLE
  • Syphilis

Mitral stenosis

Narrowing of the mitral valve causes less blood to be ejected from the left atrium during systole, therefore left atrial pressure increases.

This causes:

  • A ‘snapping sound’ ie. opening click when the mitral valve opens
  • Mitral valve closes against high left atrial pressure, causing a loud S1 and a tapping apex beat (ie. a palpable closing mitral valve)

 

Signs of pulmonary hypertension may be present:

  • Malar flush
  • Right sternal heave
  • Graham Steel murmur – early decrescendo murmur heard in the pulmonary area due to pulmonary incompetence

 

Typical description

  • Low-pitched, rumbling mid-diastolic murmur with an opening click (click heard in mid-diastole when the mitral valve opens)
  • Heard loudest over the apex
  • Loudest in left lateral decubitus position on expiration
  • Low-volume pulse which may be irregularly, irregular (atrial fibrillation is common in mitral stenosis)
  • Loud first heart sound with tapping apex beat (due to a palpable closing of the mitral valve)

 

Causes

  • Rheumatic heart disease (commonest cause of mitral stenosis worldwide)
  • Congenital
  • Left atrial myxoma
  • Connective tissue disorders
  • Mucopolysaccharidosis

 

NB: Two-thirds of patients with mitral stenosis are female


Mitral valve prolapse

Typical description

  • Mid-systolic click (prolapse of the mitral valve into left atrium)
  • Followed by a mid or late-systolic murmur
  • Heard loudest at the apex
  • Loudest in expiration

 

Causes

The most common valvular abnormality (prevalence is about 5%).

Can occur alone, or in association with:

  • Rheumatic heart disease
  • Connective tissue disorders – Marfan syndrome, Ehlers Danlos syndrome, osteogenesis imperfecta
  • Ebstein anomaly
  • Associated with an atrial septal defect and patent ductus arteriosus
  • Systemic lupus erythematosus

 


Tricuspid regurgitation

Tricuspid regurgitation causes blood to flow from the right ventricle to right atrium during ventricular systole. This causes an increase in right atrial pressure and hence elevated venous pressures.

 

Typical description

  • Pansystolic murmur
  • Heard loudest over the tricuspid region
  • Loudest during inspiration
  • Large ‘v-waves’ in JVP – caused by the right atrial filling of blood against a closed tricuspid valve
  • Visible/palpable hepatic pulsations
  • Signs of right-sided heart failure:
    • Right ventricular heave
    • Peripheral oedema
    • Hepatomegaly
    • Ascites

 

Causes

  • Right ventricular dilatation (e.g. secondary to pulmonary stenosis or pulmonary hypertension)
  • Rheumatic fever
  • Infective endocarditis (IV drug users are at high risk of endocarditis affecting the tricuspid valve)
  • Carcinoid syndrome
  • Congenital (e.g. atrial septal defect, AV canal, Ebstein anomaly)
    • Ebstein anomaly i.e. congenital isolated tricuspid regurgitation –abnormal attachment of tricuspid valve leaflets causes the tricuspid valve to displace downwards into the right ventricle

Pulmonary stenosis

Typical description

  • Ejection systolic murmur
  • Heard loudest over pulmonary area
  • Loudest during inspiration
  • Radiates to left shoulder/ left infraclavicular region
  • Prominent ‘a waves’ in JVP
  • Widely split S2 – blood from the ventricles takes longer to pass through a narrow pulmonary valve, so pulmonary valve closure occurs much later than aortic valve closure
  • In severe pulmonary stenosis, the murmur is longer and may obscure the sound of A2
  • P2 may be soft and inaudible
  • Right ventricular dilatation can lead to:
    • Right ventricular heave
    • Tricuspid regurgitation
    • Peripheral signs of right-sided heart failure (e.g. peripheral oedema, ascites etc)

 

Causes

  • Congenital
    • Turner’s, Noonan’s and Williams syndromes
    • Tetralogy of Fallot – pulmonary stenosis, right ventricular hypertrophy, ventricular septal defect and overriding aorta
  • Rheumatic fever
  • Carcinoid syndrome

Pulmonary regurgitation

Typical description

  • Early decrescendo murmur
  • Heard loudest over the left sternal edge
  • Loudest during inspiration
  • Usually due to pulmonary hypertension – known as a Graham Steell murmur when associated with mitral stenosis

Tricuspid stenosis

Typical description

  • Mid-diastolic murmur (rarely audible)
  • Loudest at 3rd-4th intercostal space, left sternal edge
  • Loudest during inspiration
  • Signs of right atrial enlargement
    • Raised JVP with giant ‘a waves’
    • Peripheral oedema, ascites

 

Causes

  • Rheumatic fever (most common)
  • Congenital disease
  • Infective endocarditis

Differentiating murmurs: Summary table

Lesion Heart Cycle Character Breathing Location Radiates Associations
Aortic Stenosis Systolic Ejection systolic Expiration 2nd intercostal space right sternal edge Neck (carotids) Slow-rising, narrow pulse pressure
Pulmonary Stenosis Systolic Ejection systolic Inspiration 2nd intercostal space left sternal edge Left shoulder/infra-clavicular Right-sided heart failure (RV heave, tricuspid regurgitation, raised JVP)

Widely split S2

Mitral Regurgitation Systolic Pansystolic Expiration Apex Axilla
Tricuspid Regurgitation Systolic Pansystolic Inspiration Left sternal edge Large ‘v-waves’ in JVP, hepatic pulsations
Mitral Valve Prolapse Mid systolic + opening click Expiration Apex
Aortic Regurgitation Early diastolic Decrescendo Expiration Left sternal edge (or 2nd intercostal space right sternal edge) Left sternal edge Collapsing pulse, wide pulse pressure. Corrigan’s, Quincke’s, de-Musset’s, Duroziez’s, Austin Flint murmur
Pulmonary Regurgitation Early diastolic Decrescendo Inspiration 2nd intercostal space left sternal edge Right-sided heart failure
Mitral Stenosis Mid/late diastolic Expiration Apex
Tricuspid Stenosis Mid/late diastolic Inspiration Left sternal edge

 


 

Editor

Andrew Gowland