Normal Heart Sounds

The first heart sound (S1) is produced by closure of the atrioventricular valves—the mitral and tricuspid valves—at the start of ventricular systole.

The second heart sound (S2) occurs when the semilunar valves—the aortic and pulmonary valves—shut at the end of systole, once ventricular contraction has finished.

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Third Heart Sound (S3)

A third heart sound (S3) is heard about 0.1 seconds after S2. A helpful way to picture it is rapid ventricular filling pulling the chordae tendineae taut so they “twang” like a guitar string. When present, the rhythm may be described as a “gallop rhythm.”

An S3 can be normal in healthy young people aged 15–40 years, because their ventricles fill quickly due to good cardiac function. In older patients, an S3 can suggest heart failure, because the ventricles and chordae are stiff and weak and therefore reach their filling limit much sooner than usual. A comparison is tight hamstrings in an older, deconditioned person that suddenly tighten as they bend forward.

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Fourth Heart Sound (S4)

A fourth heart sound (S4) occurs immediately before S1. It is always abnormal and is relatively uncommon to hear. It indicates a stiff or hypertrophied ventricle and results from turbulent blood flow caused by atrial contraction against a non-compliant ventricle.

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Listening for Murmurs

Use the bell of the stethoscope to hear low-frequency sounds more clearly, and the diaphragm for high-frequency sounds. A memory aid is that a child’s high-pitched scream comes “from the diaphragm,” while a church bell produces a deep “bong.”

Listen systematically over the four valve areas:

• Pulmonary area – 2nd intercostal space, left sternal border
• Aortic area – 2nd intercostal space, right sternal border
• Tricuspid area – 5th intercostal space, left sternal border
• Mitral area – 5th intercostal space, mid-clavicular line (apex)

Also listen at Erb’s point: the 3rd intercostal space at the left sternal border, which is often the best location for hearing S1 and S2 clearly.

Manoeuvres to accentuate murmurs

• Roll the patient onto the left side to bring out mitral stenosis
• Sit the patient up, ask them to lean forward, and listen while they hold expiration to emphasise aortic regurgitation

Assessing a Murmur

The key murmur features can be recalled using “SCRIPT”:

• S – Site: where is it loudest?
• C – Character: soft / blowing / crescendo / decrescendo / crescendo–decrescendo
• R – Radiation: does it transmit to the carotids (aortic stenosis) or left axilla (mitral regurgitation)?
• I – Intensity: what grade is it?
• P – Pitch: high pitched or low, rumbling? (Pitch reflects velocity.)
• T – Timing: systolic or diastolic?

Grading Murmurs

Murmur grading is subjective, but helps convey severity and improves clinical presentations. If uncertain, it is usually grade 2 or 3.

• Grade I: barely audible
• Grade II: quiet
• Grade III: clearly audible
• Grade IV: clearly audible with a palpable thrill
• Grade V: audible with the stethoscope barely touching the chest
• Grade VI: audible with the stethoscope off the chest

How to Describe a Murmur (Exam Script)

You can use the following template in OSCEs and exam presentations:

“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 and Dilatation in Valve Disease

Valve pathology can drive either:

• Hypertrophy: thickening outward and inward into the chamber, or
• Dilatation: stretching and thinning of the myocardium (like inflating a balloon)

The chamber most affected is usually the one immediately upstream of the diseased valve (for example, the left ventricle in aortic disease, and the left atrium in mitral disease).

Stenotic valves → hypertrophy (pushing against obstruction)

• Mitral stenosis → left atrial hypertrophy
• Aortic stenosis → left ventricular hypertrophy

Regurgitant valves → dilatation (volume overload from backflow)

• Mitral regurgitation → left atrial dilatation
• Aortic regurgitation → left ventricular dilatation

Aortic Stenosis

Aortic stenosis is the commonest valvular heart disease and the most frequent reason for valve replacement surgery. It is narrowing of the aortic valve, reducing blood flow from the left ventricle into the aorta.

It produces an ejection systolic, high-pitched murmur because blood moves at high velocity through the narrowed valve. The murmur is crescendo–decrescendo, reflecting changes in flow speed during systole: slowest at the beginning and end, and fastest in the middle.

It typically radiates to the carotids because turbulence continues into the neck vessels.

Other features of aortic stenosis

• Palpable thrill in the aortic area
• Slow-rising pulse
• Narrow pulse pressure (small difference between systolic and diastolic pressures)
• Exertional syncope (lightheadedness/fainting during exercise) due to difficulty maintaining adequate cerebral blood flow

Causes of aortic stenosis

• Age-related idiopathic calcification (by far the most common)
• Bicuspid aortic valve
• Rheumatic heart disease

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Aortic Regurgitation

Aortic regurgitation is due to an incompetent aortic valve, allowing blood to leak back from the aorta into the left ventricle.

It classically causes an early diastolic, soft murmur.

It can also produce an Austin–Flint murmur, heard at the apex as a diastolic “rumbling” murmur. This occurs because regurgitant flow through the aortic valve passes over the mitral valve, making it vibrate.

Other signs of aortic regurgitation

• Palpable thrill in the aortic area
• Collapsing (water-hammer) pulse
• Wide pulse pressure
• Heart failure and pulmonary oedema

A collapsing pulse is described as forceful and then rapidly disappearing. It is typically felt at the radial artery with the patient’s arm raised straight upwards. It occurs because blood is ejected strongly from the left ventricle and then immediately falls back into the ventricle through the incompetent aortic valve.

Causes of aortic regurgitation

• Idiopathic age-related weakening
• Bicuspid aortic valve
• Connective tissue disorders (e.g., Ehlers–Danlos syndrome, Marfan syndrome)

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Mitral Stenosis

Mitral stenosis is narrowing of the mitral valve, restricting blood flow from the left atrium to the left ventricle.

It produces a mid-diastolic, low-pitched “rumbling” murmur because flow velocity across the valve is low. A loud S1 is typical because thickened valve leaflets need more force to close and then snap shut. An opening snap is heard after S2 and marks the onset of the murmur.

Other signs of mitral stenosis

• Tapping apex beat (a palpable, prominent S1)
• Malar flush
• Atrial fibrillation (irregularly irregular pulse)

Malar flush is redness over the upper cheeks and nose. It results from back pressure into the pulmonary circulation, leading to raised CO₂ and vasodilation.

Atrial fibrillation can occur because the left atrium must work harder to force blood through the narrowed valve, leading to strain and electrical instability.

Causes of mitral stenosis

• Rheumatic heart disease
• Infective endocarditis

TOP TIP: When assessing valve disease, look for clues to underlying causes. For example, in mitral stenosis, check for infective endocarditis signs such as splinter haemorrhages, Janeway lesions, Osler’s nodes, and splenomegaly, and offer fundoscopy for Roth spots. In aortic regurgitation, look for Marfan features such as tall stature, long limbs, arachnodactyly (long slender fingers), and a high-arched palate. This can strengthen your OSCE performance and presentations.

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Mitral Regurgitation

Mitral regurgitation is mitral valve incompetence that allows blood to flow backward from the left ventricle into the left atrium during ventricular systole. The regurgitant flow reduces effective forward output and causes blood to backlog in the left-sided chambers, leading to congestive cardiac failure. Mitral regurgitation is the second most common reason for valve replacement.

It produces a pan-systolic, high-pitched “whistling” murmur due to high-velocity flow across the incompetent valve. The murmur often radiates to the left axilla, and an S3 may be heard.

Other signs of mitral regurgitation

• Palpable thrill at the mitral area
• Heart failure and pulmonary oedema signs
• Atrial fibrillation (irregularly irregular pulse)

Causes of mitral regurgitation

• Age-related idiopathic valve weakening
• Ischaemic heart disease
• Infective endocarditis
• Rheumatic heart disease
• Connective tissue disorders (e.g., Ehlers–Danlos, Marfan syndrome)

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Tricuspid Regurgitation

Tricuspid regurgitation occurs when the tricuspid valve is incompetent, allowing blood to reflux from the right ventricle into the right atrium during right ventricular systole.

It causes a pan-systolic murmur. A split S2 is present because the pulmonary valve closes before the aortic valve, as the right ventricle empties more quickly than the left.

Other signs of tricuspid regurgitation

• Palpable thrill in the tricuspid area
• Raised JVP with giant C–V waves (Lancisi’s sign)
• Pulsatile liver (regurgitation transmitted into the venous system)
• Peripheral oedema
• Ascites

Causes of tricuspid regurgitation

• “Functional” regurgitation from pressure overload due to left-sided heart failure or pulmonary hypertension
• Infective endocarditis
• Rheumatic heart disease
• Carcinoid syndrome
• Ebstein’s anomaly
• Connective tissue disorders (e.g., Marfan syndrome)

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Pulmonary Stenosis

Pulmonary stenosis is narrowing of the pulmonary valve, restricting blood flow from the right ventricle into the pulmonary arteries.

It produces an ejection systolic murmur, loudest in the pulmonary area, and becomes louder with deep inspiration. There is a widely split S2, because the left ventricle empties faster than the right ventricle.

Other signs of pulmonary stenosis

• Palpable thrill in the pulmonary area
• Raised JVP with giant A waves (right atrium contracting against a hypertrophied right ventricle)
• Peripheral oedema
• Ascites

Pulmonary stenosis is usually congenital and may be associated with:

• Noonan syndrome
• Tetralogy of Fallot

Tetralogy of Fallot consists of four concurrent abnormalities:

• Ventricular septal defect (VSD)
• Overriding aorta
• Pulmonary valve stenosis
• Right ventricular hypertrophy

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Last updated Dec 2025