S1 and S2

The first heart sound (S1) is caused by the closing of the atrioventricular valves (the tricuspid and mitral valves) at the start of the systolic contraction of the ventricles.

The second heart sound (S2) is caused by the closing of the semilunar valves (the pulmonary and aortic valves) once the systolic contraction is complete.

3rd Heart Sound (S3)

A third heart sound (S3) is heard roughly 0.1 seconds after the second heart sound. I think of it as rapid ventricular filling causing the chordae tendineae to pull to their full length and twang like a guitar string. This can be normal in young (15-40 years) healthy people because the heart functions so well that the ventricles easily allow rapid filling. In older patients it can indicated heart failure, as the ventricles and chordae are stiff and weak so they reach their limit much faster than normal. Picture this like tight hamstrings in an old de-conditioned patient sharply tightening as they start to bend over.

4th Heart Sound (S4)

A fourth heart sound (S4) is heard directly before S1. This is always abnormal and relatively rare to hear. It indicates a stiff or hypertrophic ventricle and is caused by turbulent flow from an atria contracting against a non-compliant ventricle.

Listening to Murmurs

Auscultate with the bell of your stethoscope to better hear low pitched sounds and the diaphragm to listen to high pitched sounds. To remember this think of a childs high-pitched screaming from their diaphragm vs a church bell giving a deep “bong”.

Listen over the 4 valve areas in turn for murmurs:

  • Pulmonary: 2nd I.C.S left sternal border
  • Aortic: 2nd I.C.S right sternal border
  • Tricuspid: 5th I.C.S left sternal border
  • Mitral: 5th I.C.S mid clavicular line (apex area)

Listen to “Erb’s point”. This is in the third intercostal space on the left sternal border and is the best area for listening to heart sounds (S1 and S2).

Special manoeuvres can be used to emphasise certain murmurs:

  • Patient on their left hand side (mitral stenosis)
  • Patient sat up, learning forward and holding exhalation (aortic regurgitation)

Assessing a Murmur (SCRIPT mnemonic)

  • SSite: where is the murmur loudest?
  • CCharacter: soft / blowing / crescendo (getting louder) / decrescendo (getting quieter) / crescendo-decrescendo (louder then quieter)
  • RRadiation: can you hear the murmur over the carotids (AS) or left axilla (MR)?
  • IIntensity: what grade is the murmur?
  • PPitch: is it high pitched or low and grumbling? Pitch indicates velocity.
  • TTiming: is it systolic or diastolic?


Murmur Grade

Grading a murmur is quite subjective but is helpful is assessing the severity of the defect and will make you sound clever. If in doubt it is probably grade 2 or 3.

  1. Difficult to hear
  2. Quiet
  3. Easy to hear
  4. Easy to hear with a palpable thrill
  5. Can hear with stethoscope barely touching chest
  6. Can hear with stethoscope off the chest


Describing a Murmur

You can use this script for describing a murmur in your exams. If you practice it during your OSCE practice sessions it will become second nature and you will sound very slick when presenting to your examiner.

“This patient has a harsh / soft / blowing, Grade …systolic / diastolic murmur, heard loudest in the aortic / mitral / tricuspid / pulmonary area, that does not / radiates to the carotids / left axilla. It is high / low pitched and has a crescendo / decrescendo / crescendo-decrescendo shape. This is suggestive of a diagnosis of mitral stenosis / aortic stenosis


Hypertrophy vs Dilatation

Valvular heart disease can cause hypertrophy (thickening both outwards and into the chamber) or dilatation (thinning and expanding – think of blowing up a balloon) of the myocardium in different heart areas.

When pushing against a stenotic valve the muscle has to try harder resulting in hypertrophy:

  • Mitral stenosis causes left atrial hypertrophy.
  • Aortic stenosis causes left ventricular hypertrophy.

When a leaky valve allows blood to flow back into a chamber it stretches the muscle resulting in dilatation:

  • Mitral regurgitation causes left atrial dilatation.
  • Aortic regurgitation causes left ventricular dilatation.

Mitral Stenosis

This is a narrow mitral valve making it difficult for the left atrium to push blood through to the ventricle.

It is caused by:

  • Rheumatic Heart Disease
  • Infective Endocarditis

It causes a mid-diastolic, low pitched “rumbling” murmur due to a low velocity of blood flow. There will be a loud S1 due to thick valves requiring a large systolic force to shut, then shutting suddenly. You can palpate a tapping apex beat due to loud S1.

It is associated with:

Malar flush. This is due to back-pressure of blood into the pulmonary system causing a rise in CO2 and vasodilation.

Atrial fibrillation. This is caused by the left atrium struggling to push blood through the stenotic valve causing strain, electrical disruption and resulting fibrillation.

Mitral Regurgitation

Mitral regurgitation is when an incompetent mitral valve allows blood to lead back through during systolic contraction of the left ventricle. It results in congestive cardiac failure because the leaking valve causes a reduced ejection fraction and a backlog of blood that is waiting to be pumped through the left side of the heart.

It causes a pan-systolic, high pitched “whistling” murmur due to high velocity blood flow through the leaky valve. The murmur radiates to left axilla. You may hear a third heart sound.


  • Idiopathic weakening of the valve with age
  • Ischaemic heart disease
  • Infective Endocarditis
  • Rheumatic Heart Disease
  • Connective tissue disorders such as Ehlers Danlos syndrome or Marfan syndrome

Aortic Stenosis

Aortic stenosis is the most common valve disease you will encounter. It causes an ejection-systolic, high pitched murmur (high velocity of systole). This has a crescendo-decrescendo character due to the speed of blood flow across the value during the different periods of systole. Flow during systole is slowest at the very start and end and fastest in the middle.

Other signs:

  • The murmur radiates to the carotids as the turbulence continues up into the neck
  • Slow rising pulse and narrow pulse pressure
  • Patients may complain of exertional syncope (light headedness and fainting when exercising) due to difficulty maintaining good flow of blood to the brain


  • Idiopathic age related calcification
  • Rheumatic Heart Disease

Aortic Regurgitation

Aortic regurgitation typically causes an early diastolic, soft murmur. It is also associated with a Corrigan’s pulse. A Corrigan’s pulse is also called a collapsing pulse and is a rapidly appearing and disappearing pulse at carotid as the blood is pumped out by the ventricles and then immediately flows back through the aortic valve back into the ventricles. Aortic regurgitation results in heart failure due to a back pressure of blood waiting to get through the left side of the heart.

It can also cause an “Austin-Flint” murmur. This is heard at the apex and is an early diastolic “rumbling” murmur. This is caused by blood flowing back through the aortic valve and over the mitral valve causing it to vibrate.


  • Idiopathic age related weakness
  • Connective tissue disorders such as Ehlers Danlos syndrome or Marfan syndrome

Last updated November 2018