Murmur explain in easy way possible

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Here is a complete, easy-to-understand explanation of heart murmurs, straight from the textbooks:

Heart Murmur - Made Simple

What is a Heart Murmur?

Your heart makes two normal sounds every beat - lub (S1) and dub (S2). Think of these as the "doors" of your heart valves closing.

A murmur is an extra whooshing, swishing, or rumbling sound heard between those two normal sounds, caused by turbulent (rough/swirling) blood flow.

Think of it like this: a smooth-flowing river is quiet, but water rushing through a narrow spot or over rocks makes noise. Same idea with blood in your heart.

Why Does Turbulence Happen?

There are three main reasons blood becomes turbulent enough to make a sound:

Blood flows too fast through a normal opening (like in fever, anemia, pregnancy, or exercise)
Blood is squeezed through a narrowed opening (stenosis - like a stiff valve)
Blood leaks backwards through a valve that doesn't close properly (regurgitation)

(Harrison's Principles of Internal Medicine, 22E)

Types of Murmurs - By Timing

The most important thing about a murmur is WHEN in the heartbeat it happens:

1. Systolic Murmur (heard during the "lub" - contraction phase)

Happens between S1 and S2
The most common type
Can be innocent (harmless) OR due to valve disease
Examples: Aortic stenosis, mitral regurgitation

2. Diastolic Murmur (heard during the "dub" - relaxation phase)

Happens between S2 and the next S1
Almost always means something is wrong
Examples: Aortic regurgitation (leaky aortic valve), mitral stenosis

3. Continuous Murmur (heard through the whole beat - both systole AND diastole)

Goes right through the heartbeat without stopping
Example: Patent Ductus Arteriosus (PDA) - a blood vessel that should close after birth stays open

Here is what they look like on paper:

A = presystolic, B = holosystolic, C = aortic ejection, D = pulmonic stenosis, E = aortic/pulmonary diastolic, F = mitral stenosis, G = short mid-diastolic, H = continuous (PDA)

(Harrison's Principles of Internal Medicine, 22E - Fig. 44-1)

Grading - How Loud Is It?

Doctors grade murmurs from 1 to 6:

Grade	What It Means
1/6	Very faint - hard to hear even with a stethoscope
2/6	Soft but easy to hear
3/6	Moderate - clearly audible
4/6	Loud + you can feel a vibration ("thrill") on the chest wall
5/6	Very loud - heard with stethoscope barely touching chest
6/6	Extremely loud - heard even without a stethoscope

Innocent vs. Pathologic (Harmful) Murmurs

Innocent (Harmless) Murmurs

No structural problem with the heart
Common in children and young adults
Usually soft (grade 1-2/6), mid-systolic
Disappear or change with body position
The heart is otherwise completely normal
No treatment needed

Pathologic (Worrying) Murmurs

Signs that a murmur may be serious (Harriet Lane Handbook):

Loud (grade ≥3/6) or harsh
Diastolic murmur (almost always abnormal)
Accompanied by symptoms: chest pain, fainting, shortness of breath
Present with abnormal heart sounds or a "click"
The patient has cyanosis (bluish skin)
Abnormal pulses

Common Causes at a Glance

Murmur	Cause	When Heard
Aortic Stenosis	Stiff aortic valve	Systolic (harsh, diamond-shaped)
Mitral Regurgitation	Leaky mitral valve	Systolic (holosystolic)
Aortic Regurgitation	Leaky aortic valve	Diastolic (early, blowing)
Mitral Stenosis	Stiff mitral valve	Diastolic (low rumble)
PDA	Open fetal vessel	Continuous ("machinery" sound)

What Happens Next? - The Approach

(Harrison's Principles of Internal Medicine, 22E - Fig. 243-1)

In short:

Soft, mid-systolic, no symptoms in a young person → likely innocent, no further testing needed
Loud, diastolic, or continuous murmur → get an echocardiogram (ultrasound of the heart)
Any symptoms (chest pain, fainting, breathlessness) → needs full cardiac evaluation

The Bottom Line

A murmur is just a sound - it tells you that blood flow is turbulent somewhere. Most murmurs in healthy young people are completely harmless. When a murmur is loud, happens during diastole, or comes with symptoms, it points to a real valve or structural problem that needs investigation.

(Harrison's Principles of Internal Medicine 22E; Harriet Lane Handbook 23E; Braunwald's Heart Disease)

In table format

Here is the full heart murmur explanation reorganized into tables:

Heart Murmurs - Table Summary

1. What Causes a Murmur?

Cause	Simple Explanation	Example
Blood flows too fast	Like water rushing through a pipe at high pressure	Fever, anemia, pregnancy
Narrowed opening (Stenosis)	Like squeezing a garden hose - makes a whoosh	Aortic stenosis, mitral stenosis
Backward leakage (Regurgitation)	Valve doesn't close fully, blood leaks back	Mitral regurgitation, aortic regurgitation
Abnormal hole/vessel	Blood shunts where it shouldn't	VSD, Patent Ductus Arteriosus

2. Types by Timing

Type	When It Occurs	What It Sounds Like	Significance
Systolic	Between S1 (lub) and S2 (dub)	Whoosh during contraction	Can be innocent OR pathologic
Diastolic	Between S2 (dub) and next S1	Rumble/blow during relaxation	Almost always pathologic
Continuous	Throughout entire heartbeat - crosses S2	Machinery-like sound	Pathologic (e.g. PDA)
Presystolic	Just before S1, at end of diastole	Brief rumble	Seen in mitral/tricuspid stenosis (with sinus rhythm)

3. Grading (Loudness Scale 1-6)

Grade	Description	Can You Feel It?
1/6	Very faint, hard to hear	No
2/6	Soft but clearly audible	No
3/6	Moderately loud	No
4/6	Loud	Yes - thrill present
5/6	Very loud, heard with stethoscope barely touching	Yes
6/6	Heard without stethoscope	Yes

4. Innocent vs. Pathologic

Feature	Innocent (Harmless)	Pathologic (Worrying)
Grade	1-2/6	≥ 3/6
Timing	Mid-systolic only	Holosystolic, late systolic, or diastolic
Sound quality	Soft, blowing	Harsh, rough
Symptoms	None	Chest pain, fainting, breathlessness, cyanosis
Heart sounds	Normal S1 and S2	Abnormal sounds, clicks present
Pulses	Normal	Abnormally strong or weak
Who gets it	Children, young adults	Any age
Treatment needed	No	Yes - investigate further

5. Common Murmurs by Valve

Valve Problem	Type	When Heard	Classic Sound	Best Heard At
Aortic Stenosis (AS)	Systolic ejection	Mid-systolic	Harsh, crescendo-decrescendo	Right upper sternal border
Aortic Regurgitation (AR)	Diastolic	Early diastolic	High-pitched blowing	Left sternal border
Mitral Stenosis (MS)	Diastolic	Mid-to-late diastolic	Low rumble	Apex
Mitral Regurgitation (MR)	Systolic	Holosystolic (all of systole)	Blowing, high-pitched	Apex, radiates to axilla
Tricuspid Regurgitation (TR)	Systolic	Holosystolic	Blowing	Lower left sternal border
Pulmonic Stenosis (PS)	Systolic	Mid-systolic	Harsh	Left upper sternal border
Patent Ductus Arteriosus (PDA)	Continuous	Both systole + diastole	"Machinery" murmur	Left upper sternal border
VSD	Systolic	Holosystolic	Harsh, loud	Left lower sternal border

6. What to Do When a Murmur is Found

Murmur Characteristics	Action
Soft (grade 1-2), mid-systolic, no symptoms, young patient	No further workup needed
Loud (≥ grade 3), holosystolic, or late systolic	Echocardiogram
Any diastolic or continuous murmur	Echocardiogram + cardiac consult
Any murmur + symptoms (chest pain, syncope, dyspnea)	Echocardiogram + cardiac consult
Any murmur + abnormal ECG or chest X-ray	Echocardiogram + cardiac consult

7. Memory Aid - "STALQR" for Describing Any Murmur

Letter	What to Assess	Example
S	Site (where is it loudest?)	Apex, RUSB, LUSB
T	Timing (systolic/diastolic/continuous?)	Holosystolic
A	Amplitude/Grade (1-6?)	Grade 3/6
L	Length/Duration	Whole of systole
Q	Quality (harsh/blowing/rumbling?)	Harsh, rough
R	Radiation (where does it spread?)	To axilla, to carotid

(Sources: Harrison's Principles of Internal Medicine 22E; Harriet Lane Handbook 23E; Braunwald's Heart Disease; Fuster and Hurst's The Heart 15E)

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