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Physiology · Cardiovascular

Murmurs and the hemodynamics of valve disease !

  • Mechanism
  • Exam priority: medium

A murmur is the sound of blood flowing turbulently through a narrow valve, a valve that does not close, or an abnormal opening.

Updated 2026-11-01

See it in 3D: Mitral anterior leaflet · Aortic non-coronary cusp · Chordae tendineae · Interventricular septum · Left ventricle

What it is

Blood flows silently while flow stays laminar. When it races through a narrow opening or leaks back through an incompetent valve, it turns turbulent and vibrates: that is the murmur. When in the cycle it sounds tells you which valve fails and whether it is stenosis or regurgitation.

How it works, step by step

  1. Flow turns turbulent when the Reynolds number rises: high velocity, a narrow orifice, thin blood (anemia).
  2. Turbulence vibrates the walls and the chest; the stethoscope hears it as a murmur.
  3. Stenosis: the chamber needs more pressure to force blood through; a pressure gradient appears across the valve.
  4. Regurgitation: part of the volume goes back to the chamber it came from and adds to the next filling (volume overload).
  5. Pressure overload causes concentric hypertrophy; volume overload causes dilation with eccentric hypertrophy.
  6. Over time left atrial pressure rises, the lungs congest and atrial fibrillation may appear.

Cardiac cycle (Wiggers diagram)

Cardiac cycle (Wiggers diagram) Pressure (mmHg)040801200–25 mmHg detail: atrium and ventricle01020LV volume (mL)50120ECGHeart sounds0200400600800Time (ms)AortaLVdicrotic notchacvLALVEDV 120ESV 50PQRSTS1S2AOACMCMO1234567

HR 75/minCycle 800 msSystole ≈ 300 msSV 70 mLEF 58%

Tap a number (phase), a dot (valve) or a sound.

1 Atrial systole · 2 Isovolumetric contraction · 3 Rapid ejection · 4 Reduced ejection · 5 Isovolumetric relaxation · 6 Rapid filling · 7 Diastasis (slow filling).

MC mitral closure · AO aortic opening · AC aortic closure · MO mitral opening.

  • Aorta
  • Left ventricle (LV)
  • Left atrium (LA)
  • LV volume
  • ECG
  • S1 and S2
  • Ventricular systole
  • Ventricular diastole
  • Valve events (MC, AO, AC, MO)
Find S1 and S2: anything between them is systolic; after S2, diastolic.

Left-ventricular pressure–volume loop

Left-ventricular pressure–volume loop: Aortic stenosis, EDV 115 mL, ESV 51 mL 050100150200250060120180240LV volume (mL)LV pressure (mmHg)ESPVREDPVREaFillingEjectionIsovol. contr.Isovol. relax.MOMCAOAC

EDV 115 mLESV 51 mLSV 64 mLEF 56%ESP 206 mmHgLV peak ≈ 222 mmHg

Aortic stenosis

Aortic stenosis: the LV must build a very high systolic pressure to push through the narrow valve (the aorta sees much less); the loop is tall, SV tends to fall and concentric hypertrophy stiffens filling.

Tap a corner of the loop (MC, AO, AC, MO) to see the valve event.

  • Current loop
  • Normal loop
  • ESPVR (contractility, Ees)
  • EDPVR (passive filling)
  • Ea (arterial afterload)
  • Stroke volume (SV)
Compare aortic stenosis with the mitral and aortic regurgitation presets.

Classic murmurs (where and why)

LesionTimingBest heardKey hemodynamics
Aortic stenosisMidsystolic ejection2nd right intercostal space, radiates to carotidsLV–aorta gradient; weak, late pulse; concentric hypertrophy
Aortic regurgitationEarly diastolic decrescendoLeft sternal borderWide pulse pressure; large stroke volume; LV dilation
Mitral regurgitationHolosystolicApex, radiates to axillaNo true isovolumetric phase; large left atrium
Mitral stenosisOpening snap and diastolic rumbleApex, left lateral decubitusLA–LV gradient; large atrium; pulmonary congestion
Ventricular septal defectHolosystolicLower left sternal borderLeft-to-right shunt; small defects sound louder

Clinical notes

  • A diastolic murmur is always pathological; a soft systolic one in a healthy child or a pregnant woman may be a high-flow functional murmur.
  • In aortic stenosis the triad of angina, syncope and dyspnea marks severe disease.
  • Rheumatic fever after streptococcal pharyngitis damages the mitral valve most of all.

Test yourself

Think of the answer, then tap the question to see it.

Why does aortic stenosis cause a systolic murmur and aortic regurgitation a diastolic one?

The aortic valve should be open in systole (stenosis obstructs forward flow) and closed in diastole (regurgitation lets blood fall back from the aorta into the ventricle).

What happens to a mitral regurgitation murmur when the patient squeezes both hands hard?

It gets louder: handgrip raises afterload, so blood finds it easier to go back into the left atrium than out into the aorta.

Why does chronic aortic regurgitation widen the pulse pressure?

The ventricle ejects a large volume (high systolic) and blood runs back in diastole (low diastolic).

Why can a small VSD be louder than a large one?

A small hole keeps a high pressure gradient between the ventricles and a fast, turbulent jet; in a large defect the pressures equalize and the jet slows.

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See it in 3D

The structures of Durgical's 3D anatomy where it happens.

← All of physiology

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: 19.3 Cardiac Cycle (OpenStax (Rice University), 2022); Aortic Stenosis (StatPearls (NCBI Bookshelf), 2024); Mitral Regurgitation (StatPearls (NCBI Bookshelf), 2026); Rheumatic Heart Disease (StatPearls (NCBI Bookshelf), 2023); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 23). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).

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Representative model, for educational purposes only.