A heart murmur is a sound produced due to turbulent blood flow within the heart.

Heart murmurs are heard by auscultation with a stethoscope as part of the cardiovascular examination. 

The cardiac cycle

The cardiac cycle refers to a series of physiological events making up a single heartbeat. The cycle involves contraction (systole) and relaxation (diastole) of the atria and ventricles to effectively pump blood. 

The cardiac cycle starts with the atria and ventricles in diastole. Blood enters the right atrium (from the vena cava) and the left atrium (from the pulmonary vein). At this point, the mitral and tricuspid valves are open. This allows blood to flow freely into the right ventricle and left ventricle from the atria. The aortic and pulmonary valves are shut, which prevents an abnormal backflow of blood into the ventricles from the aorta and pulmonary artery.

The next stage of the cycle is atrial systole, contraction of the atria to finish “filling” the ventricles with blood. 

Ventricular systole occurs as the ventricles contract, increasing the pressure within the ventricles. The increased pressure causes the closure of the mitral and tricuspid valves, this prevents regurgitation of blood from the ventricles into the atria. 

At this point, the volume of blood within the ventricles remains constant as the aortic and pulmonary valves have not yet opened. This phase of ventricular systole is called isovolumetric contraction.

Eventually, the pressure within the ventricles exceeds the pressure in the pulmonary artery and aorta causing the pulmonary and aortic valves to open. Blood is ejected from the ventricles during ventricular ejection phase.

The ventricles then begin to relax following contraction (ventricular diastole). The drop in pressure within the ventricle causes the aortic and pulmonary valves to close, to prevent backflow (regurgitation) of blood into the ventricles.

Figure 1. An overview of the cardiac cycle.1

For more information, see the Geeky Medics guide to the electrical conduction system of the heart

Normal heart sounds

Normal heart sounds are caused by the closure of heart valves.

First heart sound (S1)

The first heart sound (S1) is caused by the closure of the mitral and tricuspid valves. It marks the start of ventricular systole, and a peripheral pulse is felt at the same time (or shortly after) S1.

Second heart sound (S2)

The second heart sound (S2) is caused by the closure of aortic and pulmonary valves. It marks the end of ventricular systole, and the 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 (split S2).

Heart sounds and the cardiac cycle

Figure 2. A Wiggers diagram showing the events of the cardiac cycle.2

How to approach heart murmurs

It is important to have a structured approach to interpreting heart murmurs.

If a murmur is heard during auscultation, consider the following questions:

  • When during the cardiac cycle is the murmur heard?
  • What are the characteristics of the murmur? What is the intensity (Table 1)?
  • Is the murmur heard loudest using the bell or the diaphragm of the stethoscope?
  • Where is the murmur heard the loudest?
  • Do any manoeuvres exaggerate the murmur?
  • Heard loudest on inspiration or expiration?
  • Does the murmur radiate?

Table 1. The Levine scale for grading cardiac murmurs according to intensity.3

OneVery faint. Heard by an expert in optimum conditions
TwoHeard by a non-expert in optimum conditions
ThreeEasily audible, no thrill
FourA loud murmur, with a thrill
FiveVery loud, often heard over a wide area, with thrill
SixExtremely loud, heard without a stethoscope

thrill is a palpable vibration caused by turbulent blood flow through a heart valve. Thrills may be felt when palpating the anterior chest wall during a cardiovascular examination.

Aortic stenosis

Aortic stenosis (AS) refers to a tightening of the aortic valve at the origin of the aorta.

Aortic stenosis is associated with an ejection systolic murmur heard loudest over the aortic valve. The murmur is described as having a crescendo-decrescendo’ quality (it appears as diamond-shaped on a phonogram). The murmur of aortic stenosis commonly radiates to the carotid arteries.


Causes of aortic stenosis include:

  • Calcification of the aortic valves: this is the most common cause of AS in developed countries, typically occurring in elderly adults.
  • Congenital abnormality of the aortic valve: the aortic valve is normally composed of three cusps (known as a tricuspid valve), but in some cases, individuals have only two cusps (known as a bicuspid valve) which predisposes them to the development of AS as well as aortic regurgitation.
  • Rheumatic heart disease: a rare cause of AS in developed countries.

Clinical features

Typical features of an aortic stenosis murmur include:

  • Ejection systolic murmur heard loudest over the aortic area
  • Radiates to the carotid arteries
  • Loudest on expiration and when the patient is sitting forwards

Other clinical features of aortic stenosis may include:

  • Slow rising pulse with narrow pulse pressure
  • Non-displaced, heaving apex beat (if present indicates left ventricular hypertrophy)
  • Reduced or absent S2 (a 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)

Mitral regurgitation

Mitral regurgitation (MR) occurs when there is backflow (regurgitation) of blood from the left ventricle into the left atria (through the mitral valve) during ventricular systole.

Mitral regurgitation is associated with a pansystolic murmur heart loudest over the mitral area and radiating to the axilla.


Mitral regurgitation can be either acute or chronic.

Causes of mitral regurgitation include:

  • Infective endocarditis
  • Acute myocardial infarction with rupture of papillary muscles
  • Rheumatic heart disease
  • Congenital defects of the mitral valve
  • Cardiomyopathy

Clinical features

Typical features of mitral regurgitation murmur include:

  • A pansystolic murmur heard loudest over mitral area
  • Radiation of the murmur to the axilla
  • Heard loudest using the bell of the stethoscope
  • Loudest on expiration in the left lateral decubitus position

Other clinical features may include:

  • Displaced, hyperdynamic apex beat

Aortic regurgitation

Aortic regurgitation (AR) occurs when there is backflow of blood from the aorta into the left ventricle during ventricular diastole. 

Aortic regurgitation is associated with an early diastolic murmur heard loudest at the left sternal edge 


Aortic regurgitation can be either acute or chronic. Chronic AR is often asymptomatic.

AR can occur due to a disease process affecting the valve itself, or due to dilatation of the aortic root.

Diseases affecting the valve include:

  • Congenital bicuspid aortic valve
  • Rheumatic heart disease
  • Infective endocarditis

Causes of aortic root dilatation include:

  • Aortic dissection: can result in acute aortic regurgitation
  • Connective tissue diseases (e.g. Marfan’s)
  • Aortitis

Typical clinical features

Typical features of an aortic regurgitation murmur include:

  • Decrescendo early diastolic murmur
  • Heard loudest at left sternal edge (the direction that the turbulent blood flows) sometimes heard loudest over the aortic area
  • Austin Flint murmur: a low pitched rumbling mid-diastolic murmur heard best at the apex. This is caused by the regurgitated blood through the aortic valve mixing with blood from the left atrium, during atrial contraction. An Austin Flint murmur is a sign of severe aortic regurgitation.

Other clinical features of aortic regurgitation may include:

  • Collapsing pulse (a ‘water hammer pulse’ with wide pulse pressure)
  • Displaced, hyperdynamic apex beat
Eponymous clinical signs of aortic regurgitation

There are many eponymous clinical signs associated with aortic regurgitation. These include:

  • 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 the nail bed is lightly compressed
  • 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

Mitral stenosis

Mitral stenosis (MS) is narrowing of the mitral valve, which results in decreased filling of the left ventricle during systole and increased left atrial pressure (due to incomplete left atrial emptying).

Mitral stenosis is associated with a low-pitched, rumbling, mid-diastolic murmur heard loudest over the apex. 


Rheumatic heart disease is the most common cause of mitral stenosis.

Other rarer causes include:

  • Congenital
  • Left atrial myxoma
  • Connective tissue disorders
  • Mucopolysaccharidosis

Clinical features

Typical features of a mitral stenosis murmur include:

  • Low-pitched, rumbling mid-diastolic murmur with an opening click (click heard in mid-diastole when the mitral valve opens)
  • Murmur is heard loudest over the apex
  • Loudest in left lateral decubitus position on expiration

Other clinical features of mitral stenosis may include:

  • A 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)
  • A malar flush (plum-red discolouration of the cheeks)

Mitral valve prolapse

mitral valve prolapse occurs when the mitral valve leaflets prolapse into the left atrium during systole. 

Mitral valve prolapse is associated with a combination of a mid-systolic click and mid to late-systolic murmur.


Mitral valve prolapse is the most common valvular abnormality with a prevalence of approximately 5%.

The exact underlying cause of mitral valve prolapse is unknown. Primary mitral valve prolapse is caused by myxomatous degeneration of the mitral valve and is associated with connective tisuse diseases. Secondary mitral valve prolapse occurs when a ‘normal’ valve prolapses.

Typical clinical features

Typical features of a mitral valve prolapse murmur include:

  • 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

Tricuspid regurgitation

Tricuspid regurgitation occurs when there is backflow of blood from the right ventricle into the right atrium during ventricular systole. This causes an increase in right atrial pressure and elevated venous pressures.

Tricuspid regurgitation is associated with a pansystolic murmur heard loudest over the tricuspid region. 


Causes of tricuspid regurgitation include:

  • Right ventricular dilatation (e.g. secondary to pulmonary stenosis or pulmonary hypertension)
  • Rheumatic fever
  • Infective endocarditis (intravenous drug users are at high risk of endocarditis affecting the tricuspid valve)
  • Carcinoid syndrome
  • Congenital (e.g. atrial septal defect, AV canal, Ebstein anomaly)

The Ebstein anomaly (i.e. congenital isolated tricuspid regurgitation) is abnormal attachment of tricuspid valve leaflets causes the tricuspid valve to displace downwards into the right ventricle.

Typical clinical features

Typical features of a tricuspid regurgitation murmur include:

  • Pansystolic murmur
  • Heard loudest over the tricuspid region
  • Loudest during inspiration

Other clinical features of tricuspid regurgitation may include:

  • Large ‘v-waves’ visible in the jugular veins: 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

Pulmonary stenosis

Pulmonary stenosis (PS) refers to narrowing of the pulmonary valve. It is commonly associated with other congenital heart defects.


Causes of pulmonary stenosis include:

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

Typical clinical features

Typical features of a pulmonary stenosis murmur include:

  • Ejection systolic murmur heard loudest over pulmonary area
  • Loudest during inspiration
  • Radiates to left shoulder/left infraclavicular region
  • In severe pulmonary stenosis, the murmur is longer and may obscure the sound of A2

Other clinical features of pulmonary stenosis may include:

  • Prominent ‘a waves’ in the jugular veins
  • 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
  • P2 may be soft and inaudible
  • Right ventricular dilatation can lead to a right ventricular heave, tricuspid regurgitation and peripheral signs of right-sided heart failure (e.g. peripheral oedema, ascites etc)

Pulmonary regurgitation

Pulmonary regurgitation (PR) occurs when there is backflow of blood from the pulmonary artery into the right ventricle during ventricular diastole. Pulmonary regurgitation is rare.


Causes of pulmonary regurgitation include:

  • Pulmonary hypertension
  • Infective endocarditis
  • Congenital valvular heart disease

Typical clinical features

Pulmonary regurgitation is usually asymptomatic.

Typical features of a pulmonary regurgitation murmur include:

  • 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

Tricuspid stenosis (TS) refers to narrowing of the tricuspid valve.

Tricuspid stenosis is associated with a soft diastolic murmur loudest at 3rd – 4th intercostal space at the left sternal edge


Causes of tricuspid stenosis include:

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

Clinical features

Typical features of a tricuspid stenosis murmur include:

  • Mid-diastolic murmur (rarely audible)
  • Loudest at 3rd-4th intercostal space at the left sternal edge
  • Loudest during inspiration

Other clinical features of tricuspid stenosis may include:

  • Raised JVP with giant ‘a waves’
  • Peripheral oedema, ascites


Heart mumur phonogram
Figure 3. An overview of heart murmurs using a phonogram.4

Table 2. A table summarising the key differences between different heart murmurs.

LesionCardiac cycleCharacterBreathingLocationRadiation
Aortic stenosisSystolicEjection systolicExpiration2nd intercostal space right sternal edgeCarotid arteries
Pulmonary stenosisSystolicEjection systolicInspiration2nd intercostal space left sternal edgeLeft shoulder/infra-clavicular
Mitral regurgitationSystolicPansystolicExpirationApexAxilla
Tricuspid regurgitationSystolicPansystolicInspirationLeft sternal edge 
Mitral valve prolapseMid systolic + opening click ExpirationApex 
Aortic regurgitationEarly diastolicDecrescendoExpirationLeft sternal edge (or 2nd intercostal space right sternal edge)Left sternal edge
Pulmonary regurgitationEarly diastolicDecrescendoInspiration2nd intercostal space left sternal edge 
Mitral stenosisMid/late diastolic ExpirationApex 
Tricuspid stenosisMid/late diastolic InspirationLeft sternal edge 


Dr Chris Jefferies


  1. GeekyMedics
  2. OpenStax College. Diagram describing the phases of the human cardiac cycle. License: [CC-BY]. Available from: [LINK]
  3. adh30/DanielChangMD/DestinyQx. Wiggers diagram. License: [CC-BY-SA]. Available from: [LINK]
  4. Innes, A, Dover, A, Fairhurst, K. Macleod’s Clinical Examination – 14th Edition. Published in 2013. 
  5. Madhero88. Phonocardiograms from normal and abnormal heart sounds. License: [CC-BY-SA]. Available from: [LINK]