Heart Murmurs — Bone Wizardry

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Before We Start

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You're listening to a patient's heart. You hear a systolic murmur. No other info yet.

Quick — which valve problem is the MOST COMMON cause of a systolic murmur?

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The Rule — Systolic vs Diastolic

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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.

💜 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

AV valve REGURGITATION
Valve should be closed but leaks

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DIASTOLIC MURMURS

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AV valve STENOSIS
Valve should open wide but can't

Semilunar valve REGURGITATION
Valve should be closed but leaks

🔑 Systolic = Stenosis of Semilunar OR Regurg of AV. Just remember: in systole the ventricle is Squeezing — so the exit doors (semilunar) are the ones that get stuck.

A valve that should be closed during systole is leaking. Which valve and what's the pathology?

2

The Big Four — Battle Cards

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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

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?

3

Maneuvers — What Changes What (and WHY)

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Before the table, understand the two levers:

💡 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.

💡 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

💡 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.

A systolic murmur gets LOUDER when the patient stands up. What's your top diagnosis?

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HOCM — The Exception Boards Love

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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.

💥 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)

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Ventricle is smaller

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Septum and mitral leaflet are closer together

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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.

⚠ 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?

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Quiz — 4 Murmurs Walk Into a Clinic

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4 patients, 4 murmurs. The stethoscope is in your hand. Try not to send anyone home with the wrong valve.