Why Heart Sounds and Murmurs Feature in OSCEs
Cardiac auscultation is one of the highest-yield OSCE skills. Examiners can test it directly (using a mannequin or audio recording), as part of a cardiovascular examination station, or through clinical reasoning questions. Candidates must be able to systematically describe what they hear, grade murmurs accurately, identify the likely valve lesion, and state relevant associated findings.
The Normal Heart Sounds
S1 — Mitral and Tricuspid Valve Closure
S1 marks the start of systole (ventricular contraction). It is caused by closure of the mitral (M1) and tricuspid (T1) valves. M1 closes just before T1, but normally they are heard as one sound. S1 is loudest at the apex and lower left sternal edge. It is the "lub" in "lub-dub."
S2 — Aortic and Pulmonary Valve Closure
S2 marks the end of systole (start of diastole). Caused by closure of the aortic (A2) and pulmonary (P2) valves. A2 closes just before P2. S2 is loudest at the upper sternal edges. It is the "dub" in "lub-dub."
Physiological Splitting of S2
On inspiration, venous return to the right heart increases → right ventricular systole is prolonged → P2 is delayed → A2 and P2 are heard as two separate sounds. This is normal. Expiration removes the split. Wide fixed splitting (split present throughout and does not vary with respiration) suggests an ASD. Paradoxical splitting (split on expiration, merges on inspiration) suggests LBBB or aortic stenosis.
Added Heart Sounds
S3 — Ventricular Gallop
Heard in early diastole, just after S2. Caused by rapid ventricular filling hitting a dilated or non-compliant ventricle. Pathological in adults >40 years. Suggests left ventricular failure, dilated cardiomyopathy, or mitral/aortic regurgitation. Normal (physiological) in children, athletes, and pregnancy. Low-pitched — best heard with the bell of the stethoscope at the apex with the patient in left lateral decubitus.
S4 — Atrial Gallop
Heard just before S1 (late diastole). Caused by atrial contraction forcing blood into a stiff, non-compliant ventricle. Suggests hypertensive heart disease, aortic stenosis, hypertrophic cardiomyopathy, or post-MI stiff ventricle. Always pathological. Low-pitched — bell at apex.
Auscultation Areas
| Area | Location | Valve Best Heard |
|---|---|---|
| Aortic | 2nd intercostal space, right sternal edge | Aortic valve |
| Pulmonary | 2nd intercostal space, left sternal edge | Pulmonary valve |
| Tricuspid | 4th/5th intercostal space, left sternal edge | Tricuspid valve |
| Mitral (apex) | 5th intercostal space, midclavicular line | Mitral valve |
Also auscultate the carotids (aortic stenosis radiation), axilla (mitral regurgitation radiation), and between the scapulae (PDA, coarctation).
Murmur Grading (Levine Scale)
| Grade | Description |
|---|---|
| 1 | Very faint, barely audible, requires perfect conditions |
| 2 | Quiet but clearly heard |
| 3 | Moderately loud, no thrill |
| 4 | Loud with a palpable thrill |
| 5 | Very loud, thrill present, audible with stethoscope partially off chest |
| 6 | Audible without stethoscope |
💡 Tip
In the OSCE, describe murmurs using a structured framework: timing (systolic/diastolic/continuous), location (apex/left sternal edge/aortic area), radiation, character (harsh/blowing/rumbling), grade (1–6), and any changes with inspiration/position.
Common Valvular Lesions
Aortic Stenosis (AS)
- Ejection systolic murmur (ESM) — crescendo-decrescendo
- Loudest at aortic area (2nd ICS RSE), radiates to carotids
- Best heard leaning forward in expiration
- Associated: slow-rising pulse, narrow pulse pressure, heaving non-displaced apex, soft S2, ejection click (if bicuspid valve)
- Causes: calcific degeneration (elderly), bicuspid aortic valve (young), rheumatic
Aortic Regurgitation (AR)
- Early diastolic murmur (EDM) — decrescendo, high-pitched, blowing
- Best heard sitting forward, end-expiration, with diaphragm at left sternal edge
- Associated: collapsing (waterhammer) pulse, wide pulse pressure, displaced hyperdynamic apex, Austin Flint murmur (mid-diastolic rumble)
- Causes: aortic root dilatation (Marfan's, hypertension, ankylosing spondylitis), rheumatic, bicuspid valve, infective endocarditis
Mitral Regurgitation (MR)
- Pansystolic murmur — constant throughout systole, does not vary
- Loudest at apex, radiates to axilla
- Associated: displaced hyperdynamic apex, quiet S1, S3
- Causes: mitral valve prolapse, rheumatic, ischaemia (papillary muscle dysfunction), dilated cardiomyopathy
Mitral Stenosis (MS)
- Mid-diastolic rumble (MDR) — low-pitched, best heard with bell in left lateral decubitus
- Loudest at apex; does not radiate
- Preceded by an opening snap (OS) — high-pitched, best heard at left sternal edge
- Associated: loud S1, malar flush, AF, signs of pulmonary hypertension
- Causes: almost always rheumatic fever
Distinguishing Systolic Murmurs
| Murmur | Timing | Character | Location | Radiation |
|---|---|---|---|---|
| Aortic stenosis | Ejection systolic (mid-systolic) | Harsh | Aortic area | Carotids |
| Mitral regurgitation | Pansystolic | Blowing | Apex | Axilla |
| Tricuspid regurgitation | Pansystolic | Blowing | LLSE | Increases with inspiration |
| VSD | Pansystolic | Harsh | LLSE | Precordium |
| Pulmonary stenosis | Ejection systolic | Harsh | Pulmonary area | Left shoulder |
| Innocent murmur | Ejection systolic | Soft | LLSE/pulmonary | No radiation |
Mark-Scheme Checklist
💡 Tip
Examiners credit: correct stethoscope position and technique → timing (systolic/diastolic) → location → character → grade → radiation → associated sounds (S3/S4, opening snap, ejection click) → effect of inspiration → dynamic manoeuvres if asked → correlation with pulse character → correct diagnosis with differential.
Frequently Asked Questions
"What is the difference between an ejection systolic and a pansystolic murmur and why does it matter?"
An ejection systolic (mid-systolic) murmur starts after S1, builds to a crescendo in mid-systole, then decrescendos and ends before S2. There is a brief gap between S1 and the start of the murmur because the semilunar valves (aortic/pulmonary) do not open until ventricular pressure exceeds aortic/pulmonary pressure. This pattern is characteristic of aortic stenosis and pulmonary stenosis, as well as innocent flow murmurs. A pansystolic (holosystolic) murmur starts immediately at S1 and continues throughout systole right up to S2 with a constant intensity. This is because the pressure gradient across mitral and tricuspid valves exists throughout systole. Pansystolic murmurs indicate mitral regurgitation, tricuspid regurgitation, or a ventricular septal defect. Differentiating these is a core OSCE skill.
"How do I describe a heart murmur in a structured way that scores full marks?"
Use the seven-point structured description: (1) Timing — systolic (ejection vs. pan) or diastolic (early, mid, late) or continuous; (2) Location — which auscultatory area is it loudest; (3) Radiation — where does it radiate (carotids, axilla, back); (4) Character — harsh, blowing, rumbling, musical; (5) Grade — 1 to 6 on the Levine scale; (6) Effect of respiration — does it increase on inspiration (right-sided: Carvallo's sign for tricuspid regurgitation); (7) Effect of posture/manoeuvres — does it change with leaning forward (AR louder), left lateral decubitus (MS louder), Valsalva (HCM louder, AS softer). Finishing your description with: "In summary, this is most consistent with..." followed by a confident diagnosis demonstrates examiner-level clinical reasoning.
"What are the peripheral signs of aortic stenosis and how do I detect them?"
Aortic stenosis produces a characteristic slow-rising (anacrotic) pulse with a small volume — feel the radial pulse and it rises slowly to its peak, unlike the brisk upstroke of a normal pulse. In severe AS, there is a narrow pulse pressure (typically <25 mmHg). The apex beat is non-displaced but heaving (sustained and forceful) due to pressure overload hypertrophy. S2 is soft or absent (the aortic component is diminished). An ejection click may precede the murmur in bicuspid aortic valve. An S4 gallop may be present (stiff LV). The classic triad of severe AS — angina, syncope, and dyspnoea — each has a specific survival implication (median survival: 5, 3, and 2 years respectively without surgery).
"What is the Austin Flint murmur and when would I hear it?"
The Austin Flint murmur is a mid-diastolic rumbling murmur heard at the apex in severe aortic regurgitation. It closely mimics the murmur of mitral stenosis but occurs in the absence of any mitral valve pathology. It is caused by the regurgitant jet of blood from the aortic valve striking the anterior leaflet of the mitral valve, causing it to vibrate and partially obstruct the mitral valve inflow during diastole. Distinguishing it from true mitral stenosis: in Austin Flint, S1 is normal or quiet and there is no opening snap; in mitral stenosis, S1 is loud and an opening snap precedes the murmur. The presence of an Austin Flint murmur implies severe aortic regurgitation and should prompt echocardiography.
"How does inspiration affect right-sided heart murmurs?"
Inspiration increases venous return to the right heart by reducing intrathoracic pressure. This increases right ventricular preload and output, making right-sided murmurs louder on inspiration. This phenomenon is called Carvallo's sign (or Rivero-Carvallo sign) and is positive for tricuspid regurgitation — the pansystolic murmur at the lower left sternal edge becomes noticeably louder during inspiration. Left-sided murmurs (aortic stenosis, mitral regurgitation) are not significantly affected by inspiration. In the OSCE, asking the patient to take a deep breath and noting whether the murmur becomes louder helps localise it as right- or left-sided. Tricuspid stenosis and pulmonary stenosis murmurs also increase on inspiration.
"What are the signs of a haemodynamically significant murmur compared to an innocent murmur?"
Innocent (flow) murmurs are common in children, pregnant women, and febrile or anaemic patients. They are soft (grade 1–2), ejection systolic, located at the pulmonary area or left sternal edge, with no radiation, no thrill, normal S1 and S2, no additional sounds, and no associated symptoms or peripheral signs. Haemodynamically significant murmurs have one or more of: grade 3 or above, pansystolic or diastolic timing, radiation, a palpable thrill, abnormal peripheral pulses (collapsing pulse in AR, slow-rising in AS), added sounds (S3, S4, opening snap), a displaced or abnormal apex beat, or symptoms (dyspnoea, angina, syncope, reduced exercise tolerance). Any diastolic murmur is pathological until proven otherwise. In the OSCE, listing these discriminating features demonstrates clinical reasoning beyond simple auscultation.
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