Where to Listen
Auscultation Positions
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Best Heard
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Sound Type
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Radiation
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Tip
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Aortic
Pulmonic
Tricuspid
Mitral
Section 1
1
The Rule · Systolic vs Diastolic
→ Companion deep-dives
This is the one rule that decodes every murmur question. Burn it in.
Think about what the heart is doing in each phase:
❤
Systole = ventricles squeezing. Blood is being pushed OUT through the semilunar valvesAortic and pulmonic valves. They sit between the ventricles and the great vessels. They open during systole to let blood out. (aortic, pulmonic). The AV valvesMitral (left) and tricuspid (right). They sit between atria and ventricles. They're CLOSED during systole to prevent backflow. (mitral, tricuspid) should be SHUT.🔑Systole = Semilunar opens, AV Shuts. In diastole it's reversed. Same valves, opposite jobs.
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Diastole = ventricles relaxing/filling. Blood flows IN through the AV valves (mitral, tricuspid). The semilunar valves should be SHUT.
So when do you hear a murmur?
When blood goes where it shouldn't. Either a valve that should be open is too narrow (stenosis), or a valve that should be closed is leaking (regurgitation).
SYSTOLIC MURMURS
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Semilunar valve STENOSIS
Valve should open wide but can't
Valve should open wide but can't
AV valve REGURGITATION
Valve should be closed but leaks
Valve should be closed but leaks
↓
DIASTOLIC MURMURS
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AV valve STENOSIS
Valve should open wide but can't
Valve should open wide but can't
Semilunar valve REGURGITATION
Valve should be closed but leaks
Valve should be closed but leaks
A valve that should be closed during systole is leaking. Which valve and what's the pathology?
Section 2
2
The Big Four · Battle Cards
These are the four murmurs that show up on every board exam. Know them cold.
SYSTOLIC
Aortic Stenosis
Semilunar stenosis · exit door stuck
Timing
Systolic
Character
Crescendo-decrescendo
Quality
Harsh
Location
Right 2nd ICS
Radiation
Carotids
Cause
Calcification (elderly) / bicuspid (young)
🔎 Crescendo-decrescendo + radiates to carotids
SYSTOLIC
Mitral Regurgitation
AV regurgitation · door leaks backward
Timing
Systolic
Character
Holosystolic
Quality
Blowing
Location
Apex
Radiation
Left axilla
Cause
MVP, rheumatic, post-MI papillary rupture
🔎 Holosystolic + blowing at apex
DIASTOLIC
Aortic Regurgitation
Semilunar regurgitation · exit door leaks back
Timing
Early diastolic
Character
Decrescendo
Quality
Blowing
Location
Left sternal border
Classic Sign
Wide pulse pressureSystolic BP goes UP (more volume in ventricle) and diastolic BP goes DOWN (blood leaks back). The gap between systolic and diastolic widens · e.g. 170/50. This is pathognomonic for significant AR.
Cause
Bicuspid valve, Marfan, endocarditis, syphilis
🔎 Early diastolic + wide pulse pressure
DIASTOLIC
Mitral Stenosis
AV stenosis · filling door stuck
Timing
Mid-to-late diastolic
Character
Low-pitched rumble
Quality
Rumbling
Location
Apex (left lateral decubitus)
Classic Sign
Opening snap
Cause
Rheumatic fever (almost always)
🔎 Opening snap + rumble + rheumatic hx🔑Mitral Stenosis snap-to-S2: Shorter interval = Sicker valve. High LA pressure slams it shut faster.
Notice the pattern:
| Aortic Stenosis | Mitral Regurg | Aortic Regurg | Mitral Stenosis | |
|---|---|---|---|---|
| When | Systolic | Systolic | Diastolic | Diastolic |
| Shape | Cresc-decresc | Holosystolic | Decrescendo | Rumble |
| Sound | Harsh | Blowing | Blowing | Rumbling |
| Where | RUSB | Apex | LSB | Apex |
A blowing, holosystolic murmur best heard at the apex that radiates to the left axilla. What is it?
Section 3
3
Maneuvers · What Changes What (and WHY)
Before the table, understand the two levers:
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Preload = how much blood is IN the ventricle before it squeezes. More blood in = more volume for the murmur to push through = most murmurs get louder.
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Afterload = resistance the ventricle pushes AGAINST. Higher afterload = harder to eject forward = more blood leaks backward through a regurgitant valve.
The Maneuvers:
| Maneuver | What It Does | Most Murmurs | HOCM | MVP |
|---|---|---|---|---|
| Squatting | ↑ Preload AND ↑ AfterloadCompresses veins in the legs → more blood returns to heart (preload up). Also compresses arteries → more resistance to push against (afterload up). | ↑ Louder | ↓ Softer | ↓ Softer (click later) |
| Standing / Valsalva | ↓ PreloadStanding = blood pools in legs, less returns to heart. Valsalva = bearing down increases intrathoracic pressure, reducing venous return. Both decrease preload. | ↓ Softer | ↑ Louder | ↑ Louder (click earlier) |
| Hand grip | ↑ AfterloadIsometric exercise (squeezing) increases systemic vascular resistance → more resistance for the ventricle to push against. Preload doesn't change much. | MR/AR ↑ louder | ↓ Softer | , |
| Leg raise | ↑ Preload | ↑ Louder | ↓ Softer | ↓ Softer |
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The universal shortcut: Most murmurs get louder with more blood in the heart (preload up). HOCM and MVP are the opposites · they get louder with LESS blood. If a question says "louder with Valsalva/standing" → think HOCM or MVP.🔑HOCM craves emptiness. Give it a full ventricle and it goes quiet. Valsalva/standing = board code for HOCM.
A systolic murmur gets LOUDER when the patient stands up. What's your top diagnosis?
Section 4
4
HOCM · The Exception Boards Love
Hypertrophic Obstructive CardiomyopathyThe ventricular septum is abnormally thick (usually genetic, autosomal dominant). During systole, the thick septum and the mitral valve leaflet create a dynamic obstruction in the LVOT (left ventricular outflow tract). The obstruction gets WORSE when the ventricle is less full. is a systolic murmur that breaks every rule you just learned.
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HOCM = crescendo-decrescendo systolic murmur, best heard at the left sternal border. It does NOT radiate to the carotids (that's AS).
WHY HOCM is backwards:
In HOCM, the septum is too thick. During systole, the thick septum and the anterior mitral leaflet get pulled together (SAMSystolic Anterior Motion of the mitral valve. The Venturi effect from rapid blood flow through the narrowed LVOT sucks the mitral leaflet toward the septum, worsening the obstruction. It's a vicious cycle.), creating a dynamic obstruction.
Less blood in ventricle
(Valsalva, standing, dehydration)
(Valsalva, standing, dehydration)
↓
Ventricle is smaller
↓
Septum and mitral leaflet are closer together
↓
More obstruction → murmur gets LOUDER
The opposite of every other murmur. Less blood = more obstruction = louder.
More blood (squatting, leg raise) = ventricle bigger = septum and leaflet farther apart = less obstruction = softer.
🔑 HOCM is the needy murmur · give it less attention (less blood) and it gets louder. Give it more and it calms down.⚠ Board Trap: HOCM vs Aortic Stenosis
Both are systolic crescendo-decrescendo. The board question will try to trick you into picking the wrong one.
How to tell them apart:
• AS radiates to carotids. HOCM does NOT.
• AS gets louder with squatting (more blood). HOCM gets softer.
• HOCM gets louder with Valsalva. AS gets softer.
• If a question mentions Valsalva making the murmur louder → HOCM. Always.
How to tell them apart:
• AS radiates to carotids. HOCM does NOT.
• AS gets louder with squatting (more blood). HOCM gets softer.
• HOCM gets louder with Valsalva. AS gets softer.
• If a question mentions Valsalva making the murmur louder → HOCM. Always.
⚠ Board Trap: Young Athlete Sudden Death
If a question describes a young athlete who collapses during exercise, think HOCM. Exercise = dehydration + decreased preload + increased catecholamines = worsened obstruction. This is the #1 cause of sudden cardiac death in young athletes. Family history of sudden death is the giveaway.
WHY does hand grip make the HOCM murmur softer?
Section 5
5
The Rogues Gallery · Flip the Cards
Tap a card to flip it and see the board-level board lock for each murmur villain.
Aortic Stenosis
"The Calcified Killer"
Timing: Systolic crescendo-decrescendo
Location: RUSB → carotids
Origin: Calcified (old) or bicuspid (young)
Triad: Syncope · Angina · HF
Tap to flip →
Board Board Lock
Crescendo-decrescendo at RUSB radiating to carotids. Narrow pulse pressure. Delayed and diminished carotid upstroke (pulsus parvus et tardus).
Maneuvers: louder with squatting, softer with Valsalva and standing.
Maneuvers: louder with squatting, softer with Valsalva and standing.
SAd SyncopE: Syncope · Angina · HF (in that order as disease worsens)
Mitral Regurgitation
"The Back-Flow Bandit"
Timing: Holosystolic blowing
Location: Apex → left axilla
Cause: MVP, rheumatic, papillary rupture
Hallmark: Constant from S1 to S2
Tap to flip →
Board Board Lock
Holosystolic = ALL of systole, same intensity. Blood leaks from LV → LA the whole time ventricle squeezes. Blowing quality. Radiates toward the axilla because the LA is posterolateral.
Louder with hand grip (raises afterload, more backflow).
Louder with hand grip (raises afterload, more backflow).
Holosystolic = blame an AV valve leaking backward. MR = apex/axilla. TR = LLSB/inspiration.
Aortic Regurgitation
"The Wide Pulse Phantom"
Timing: Early diastolic decrescendo
Location: LSB (lean forward)
Cause: Bicuspid, Marfan, endocarditis, syphilis
Sign: Wide pulse pressure · water-hammer pulse
Tap to flip →
Board Board Lock
Diastolic because blood pours BACK into the LV when aortic valve should be shut. Wide pulse pressure: systolic goes UP (extra regurgitant volume), diastolic goes DOWN (blood escapes aorta).
Austin Flint: regurgitant jet hits the anterior mitral leaflet → mid-diastolic rumble mimicking MS.
Austin Flint: regurgitant jet hits the anterior mitral leaflet → mid-diastolic rumble mimicking MS.
BP 170/50 on boards = think AR immediately. Width > 40 = significant AR.
Mitral Stenosis
"The Rheumatic Rumbler"
Timing: Mid-to-late diastolic rumble
Location: Apex (left lateral decubitus)
Cause: Rheumatic fever (almost always)
Sign: Opening snap before the rumble
Tap to flip →
Board Board Lock
Opening snap: stiff leaflets pop open under LA pressure. The snap-to-S2 interval tells you severity: shorter interval = higher LA pressure = worse stenosis.
Atrial fibrillation is a classic complication (chronically dilated LA).
Atrial fibrillation is a classic complication (chronically dilated LA).
MS on boards = rheumatic by default. Opening snap + rumble = you've found your target.
MVP
"The Click Trickster"
Timing: Mid-systolic click +/- murmur
Location: Apex
Cause: Myxomatous degeneration, Marfan, connective tissue
Maneuver trick: Click moves EARLIER with standing
Tap to flip →
Board Board Lock
Less volume = floppy leaflets prolapse sooner = click moves earlier. Squatting (more volume) = click moves later. This is the opposite of most murmurs.
Click + late systolic murmur at apex in a young woman with palpitations = MVP until proven otherwise.
Click + late systolic murmur at apex in a young woman with palpitations = MVP until proven otherwise.
Standing makes the click EARLIER. Squatting makes it LATER. More volume = it takes longer to prolapse.
HOCM
"The Needy Obstructor"
Timing: Systolic crescendo-decrescendo
Location: LSB (no carotid radiation)
Cause: Autosomal dominant septal hypertrophy
Special power: LOUDER with less blood
Tap to flip →
Board Board Lock
Dynamic obstruction: thick septum + SAM (systolic anterior motion of mitral valve). Less volume = ventricle smaller = septum and leaflet closer = worse obstruction = LOUDER.
Young athlete + sudden death + family history + Valsalva louder = HOCM. Period.
Young athlete + sudden death + family history + Valsalva louder = HOCM. Period.
Louder with Valsalva/standing. Softer with squatting/hand grip/leg raise. The only murmur that works backwards.
Diagnostic Decision Tree · Tap nodes to light them up
Hear a murmur? Start here.
Murmur heard
↓
SYSTOLIC?
DIASTOLIC?
↓
Systolic branch
Crescendo-decrescendo
Holosystolic
Mid-systolic click
↓
RUSB/carotids?
↓
Aortic Stenosis
↓
LSB only → HOCM
Apex → axilla?
↓
Mitral Regurg
↓
LLSB/inspir → TR
Apex · young?
↓
MVP
Diastolic branch
Early diastolic decrescendo
Mid-late diastolic rumble
↓
LSB + wide PP → AR
Apex + opening snap → MS
Clinical Context · What You're Actually Dealing With
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Loading...Fetching clinical images
Section 6
6
Decision Tree: Which Murmur?
What is the timing of the murmur?
Section 7
7
Quiz · 4 Murmurs Walk Into a Clinic
4 patients, 4 murmurs. The stethoscope is in your hand. Try not to send anyone home with the wrong valve.