Murmur basic to advanced
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1. What is a Murmur?
A heart murmur is an audible vibration produced by turbulent blood flow. Three mechanisms generate turbulence:
- Accelerated flow through a normal or abnormal orifice (e.g., high-output states, stenotic valves)
- Flow into a dilated chamber or vessel downstream of a narrowing (post-stenotic dilation)
- Backward (regurgitant) flow through an incompetent valve, VSD, or PDA
The duration of a murmur depends on how long a pressure difference exists between two cardiac structures. That pressure gradient determines the velocity, turbulence, and resulting frequency and intensity of the sound. - Harrison's Principles of Internal Medicine 22E
2. Cardiac Cycle: The Framework
Understanding timing requires knowing the cardiac cycle:
| Phase | Valves Open | Valves Closed |
|---|---|---|
| Systole (S1 → S2) | Aortic, Pulmonic | Mitral, Tricuspid |
| Diastole (S2 → S1) | Mitral, Tricuspid | Aortic, Pulmonic |
- S1 = closure of mitral and tricuspid valves (onset of systole)
- S2 = closure of aortic (A2) and pulmonic (P2) valves (onset of diastole)
First step in characterizing any murmur: identify S1 vs. S2. In tachycardia where this is difficult, palpate the carotid pulse simultaneously - it closely follows S1.
3. Grading (Levine Scale, Grade 1-6)
| Grade | Description |
|---|---|
| 1/6 | Faint; appreciated only by careful auscultation in a quiet room |
| 2/6 | Soft but readily audible |
| 3/6 | Moderately loud; NOT accompanied by a palpable thrill |
| 4/6 | Loud; accompanied by a palpable thrill |
| 5/6 | Very loud; heard with stethoscope partly off the chest; thrill present |
| 6/6 | Audible without a stethoscope at all; thrill present |
Key threshold: A thrill first appears at grade 4. Any murmur with a thrill is at minimum 4/6.
Clinical rule: Grades ≥ III/VI, holosystolic, or late systolic murmurs warrant echocardiography. Any diastolic or continuous murmur also warrants echo. - Harrison's 22E, Tintinalli's Emergency Medicine
4. Murmur Characteristics to Describe
Every time you hear a murmur, characterize it by all 8 attributes:
| Attribute | Examples |
|---|---|
| Timing | Systolic, diastolic, continuous |
| Duration | Early, mid, late, holo/pan |
| Intensity | Grade 1-6 |
| Quality/Pitch | Harsh, blowing, rumbling, musical |
| Configuration | Crescendo, decrescendo, crescendo-decrescendo (diamond), plateau |
| Location | RUSB, LUSB, LLSB, apex |
| Radiation | To neck (AS), axilla (MR), back |
| Response to maneuvers | Inspiration, Valsalva, standing, squatting |
5. Murmur Types - The Master Diagram
Figure: (A) Presystolic murmur of MS/TS in sinus rhythm. (B) Holosystolic murmur of MR/TR/VSD. (C) Aortic ejection murmur with ejection click. (D) Pulmonic stenosis murmur spilling through A2. (E) Aortic/pulmonary diastolic decrescendo. (F) Long diastolic murmur of MS after opening snap. (G) Short mid-diastolic murmur after S3. (H) Continuous PDA machinery murmur. - Harrison's 22E
6. SYSTOLIC Murmurs
A. Midsystolic (Ejection) Murmurs
- Timing: Begin just after S1, crescendo-decrescendo ("diamond") shape, end before S2
- Mechanism: Outflow tract obstruction or increased ejection flow
Aortic Stenosis (AS)
- Where: Right upper sternal border (RUSB, 2nd intercostal space)
- Radiation: To carotids bilaterally
- Quality: Harsh, crescendo-decrescendo
- Associated findings: Pulsus parvus et tardus (slow-rising, low-amplitude carotid pulse), soft/absent A2, S4, sustained apical impulse
- Gallavardin effect: The murmur sounds higher-pitched and more musical at the apex - can mimic MR
- Key point: The murmur does NOT reliably reflect severity in severe AS with low-output states (the murmur can become soft as CO falls)
Pulmonary Stenosis (PS)
- Where: Left upper sternal border (LUSB)
- Radiation: To left shoulder/back
- Quality: Harsh, crescendo-decrescendo; murmur spills through A2 (delayed P2)
- Associated: Pulmonic ejection click (decreases with inspiration - unique to pulmonic), wide split S2
Hypertrophic Obstructive Cardiomyopathy (HOCM/HCM)
- Where: LLSB and apex; does NOT radiate to neck
- Quality: Harsh, crescendo-decrescendo
- Classic distinguishing feature: Murmur INCREASES with Valsalva and standing (decreased preload reduces LV volume, worsening obstruction); DECREASES with squatting and passive leg raise
Innocent/Benign ("Still's") Murmur
- Who: Children, adolescents, high-output states (pregnancy, anemia, fever, thyrotoxicosis)
- Character: Grade 1-2, soft, vibratory or musical, midsystolic
- Location: Mid-LLSB, best heard supine
- No radiation, no associated cardiac findings - disappears with Valsalva or sitting up
B. Holosystolic (Pansystolic) Murmurs
- Timing: Begin with S1 and continue through all of systole to S2 (plateau configuration)
- Mechanism: Persistent large pressure gradient throughout systole between two chambers
Mitral Regurgitation (MR)
- Where: Apex
- Radiation: To left axilla (posterior leaflet prolapse/flail) OR to base/neck (anterior leaflet flail - can mimic AS)
- Quality: High-pitched, blowing, holosystolic plateau
- Associated: S3 (severe MR), hyperdynamic apex
- In MVP: Murmur is late systolic, preceded by a nonejection click; with standing the click moves earlier (toward S1) and murmur gets louder; with squatting the opposite occurs
Tricuspid Regurgitation (TR)
- Where: Lower left sternal border (LLSB) or xiphoid
- Key feature: Increases with inspiration (Carvallo's sign) - more blood returns to right heart
- Associated: Pulsatile liver, prominent v waves in JVP
Ventricular Septal Defect (VSD)
- Where: LLSB (3rd-4th interspace)
- Quality: Harsh, holosystolic
- Radiation: Often across the precordium
- Thrill: Common even with smaller defects
C. Late Systolic Murmurs
Mitral Valve Prolapse (MVP)
- Character: Mid-to-late systolic murmur at the apex, often preceded by one or more mid-systolic clicks
- Dynamic changes: A critical distinguishing feature:
- Standing / Valsalva strain phase → click moves earlier toward S1, murmur becomes louder and longer
- Squatting / passive leg raise → click moves later toward S2, murmur becomes softer and shorter
- This is because MVP timing depends on LV volume: smaller LV = earlier prolapse
7. DIASTOLIC Murmurs
All diastolic murmurs are pathologic until proven otherwise.
A. Early Diastolic (Decrescendo, High-Pitched)
Aortic Regurgitation (AR)
- Where: Left sternal border (3rd-4th interspace), lean forward, breath held in expiration
- Quality: High-pitched, blowing, decrescendo - best with diaphragm
- Radiation: Along left sternal border
- Associated signs (all due to wide pulse pressure):
- Corrigan's (water-hammer) pulse - bounding, collapsing
- De Musset's sign - head bobbing
- Quincke's sign - capillary pulsations in nail beds
- Hill's sign - popliteal SBP > brachial SBP by ≥20 mmHg
- Austin Flint murmur - mid-diastolic rumble at apex (regurgitant jet vibrates anterior mitral leaflet, mimicking MS)
Pulmonary Regurgitation (PR)
- Graham-Steell murmur: High-pitched early diastolic murmur at LUSB in pulmonary hypertension (elevated PA pressure causes PR)
B. Mid-Diastolic (Rumbling, Low-Pitched)
Mitral Stenosis (MS)
- Where: Apex, patient in left lateral decubitus position
- Quality: Low-pitched, rumbling, mid-diastolic with presystolic accentuation (in sinus rhythm, just before S1 as atrium contracts)
- Best heard with: Bell of stethoscope with light pressure
- Associated findings:
- Loud S1 (valve closes from a wide-open position)
- Opening snap (OS) - high-pitched, best heard medial to apex; the shorter the S2-OS interval, the more severe the stenosis (higher LA pressure closes the gap)
- Left atrial enlargement → AF → presystolic accentuation disappears
- Cause: Rheumatic fever (most common worldwide), mitral annular calcification
- Symptoms: Exertional dyspnea, orthopnea, hemoptysis, systemic emboli
Tricuspid Stenosis (TS)
- Similar to MS but at LLSB; increases with inspiration
8. CONTINUOUS Murmurs
Patent Ductus Arteriosus (PDA)
- Character: Begins in systole, continues through S2, into diastole - the classic "machinery murmur"
- Why: Because the aorta-to-PA pressure gradient persists throughout the cardiac cycle (aortic pressure always exceeds pulmonary in normal anatomy)
- Where: Left infraclavicular area / LUSB
- Waxes and wanes with the cardiac cycle (louder in systole when aortic pressure peaks, quieter in diastole)
- Guyton: "The murmur is much more intense during systole, when the aortic pressure is high, and much less intense during diastole, when the aortic pressure falls low" - Guyton & Hall Medical Physiology
- Complication: Progressive pulmonary hypertension → Eisenmenger syndrome (reversal of shunt, cyanosis)
9. Dynamic Auscultation - Bedside Maneuvers
These are high-yield for exams and clinical practice.
| Maneuver | Physiology | Most Murmurs | HCM | MVP |
|---|---|---|---|---|
| Valsalva (strain phase) | Decreases venous return → ↓ preload → ↓ LV volume | Softer | Louder | Louder, longer |
| Standing | Decreases venous return → ↓ preload | Softer | Louder | Louder, earlier click |
| Squatting | Increases preload AND afterload → ↑ LV volume | Louder | Softer | Softer, later click |
| Passive leg raise | Increases venous return → ↑ preload | Louder | Softer | Softer |
| Inspiration | Increases right heart filling | Right-sided louder | - | - |
| Expiration | Increases left heart filling | Left-sided louder | - | - |
| Post-PVC | Longer filling time → ↑ SV next beat | Semilunar stenosis louder; AV regurgitation unchanged | - | - |
| Amyl nitrite | Decreases afterload → ↓ BP | AS, PS, HCM louder; MR, AR softer | Louder | Variable |
| Isometric exercise (handgrip) | Increases afterload → ↑ BP | MR, VSD, AR louder; AS softer | Softer | Softer |
The HCM rule: Any maneuver that decreases LV volume increases the HCM murmur. The opposite decreases it. MVP follows the same directional rule.
10. Summary Table - All Key Murmurs
| Condition | Timing | Location | Quality | Radiation | Key Feature |
|---|---|---|---|---|---|
| Aortic Stenosis | Mid-systolic | RUSB | Harsh, crescendo-decrescendo | Carotids | Pulsus parvus et tardus; soft A2 |
| Mitral Regurgitation | Holosystolic | Apex | Blowing, plateau | Axilla | S3; hyperdynamic apex |
| MVP | Late systolic | Apex | Variable + click | Axilla | Click moves earlier with standing |
| Pulmonic Stenosis | Mid-systolic | LUSB | Harsh | Left shoulder | Ejection click ↓ with inspiration; wide split S2 |
| VSD | Holosystolic | LLSB | Harsh | Across precordium | Thrill common |
| Tricuspid Regurgitation | Holosystolic | LLSB/xiphoid | Blowing | - | ↑ with inspiration (Carvallo's) |
| HCM | Mid-systolic | LLSB | Harsh | - | ↑ with Valsalva/standing |
| Aortic Regurgitation | Early diastolic | LLSB (lean forward) | Blowing, decrescendo | - | Wide pulse pressure; Austin Flint |
| Mitral Stenosis | Mid-diastolic | Apex (left lateral) | Low rumble | - | Loud S1, OS, presystolic accentuation |
| PDA | Continuous | LUSB/infraclavicular | Machinery | - | Persists through S2 |
11. Clinical Approach - Decision Flowchart
Practical decision rules:
- Soft midsystolic (grade 1-2) murmur, asymptomatic, no cardiac signs, normal ECG/CXR → No further workup needed
- Grade ≥ III/VI systolic, holosystolic, or late systolic → Echocardiography
- Any diastolic or continuous murmur → Always pathologic → Echo + cardiology referral
- New murmur + fever → Think endocarditis
- New murmur + acute dyspnea → Emergency - could be acute MR (papillary muscle rupture post-MI), acute AR (endocarditis, aortic dissection) → emergent echo
12. Innocent vs. Pathologic - Quick Checklist
Features suggesting INNOCENT:
- Grade 1-2, midsystolic
- Soft, vibratory, or musical
- LLSB in children
- Disappears with Valsalva, sitting, or standing
- No radiation, no associated clicks/extra sounds
- Asymptomatic patient, normal ECG
Red flags suggesting PATHOLOGIC:
- Diastolic or continuous
- Grade ≥ 3 or associated thrill
- Holosystolic or late systolic
- Radiation to neck or axilla
- Associated S3, S4, click, opening snap
- Any cardiac symptoms (dyspnea, syncope, chest pain, edema)
- Abnormal ECG or CXR
Sources: Harrison's Principles of Internal Medicine 22E (2025) | Guyton & Hall Textbook of Medical Physiology | Tintinalli's Emergency Medicine | Schwartz's Principles of Surgery 11E | Goldman-Cecil MedicineThat's the complete murmur guide, structured from first principles to advanced clinical application. Here's a quick orientation to what's covered:
Sections at a glance:
- What causes murmurs - the 3 turbulence mechanisms
- Cardiac cycle - the timing framework everything hangs on
- Levine grading scale - 1-6 with the thrill threshold
- 8 attributes to describe any murmur
- Master diagram from Harrison's 22E showing all murmur waveform patterns
- Systolic murmurs - AS, PS, HCM, innocent murmurs, MR, TR, VSD, MVP
- Diastolic murmurs - AR (with all peripheral signs), PR, MS, TS
- Continuous murmurs - PDA machinery murmur
- Dynamic maneuvers table - the HCM/MVP rule is the highest-yield exam topic here
- Master summary table - all murmurs in one place
- Diagnostic flowchart from Harrison's
- Innocent vs. pathologic checklist
The two things most students get wrong early on:
- Confusing timing (HCM murmur is systolic, not diastolic despite being due to obstruction)
- The MVP/HCM maneuver rule: decreased LV volume = louder murmur for both; just remember Valsalva and standing do that, while squatting reverses it
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