Mastering Heart Murmurs for the USMLE: Types, Mnemonics, and Diagnosis

Heart murmurs are a classic topic on USMLE Step 1 and Step 2 CK, frequently appearing in clinical vignettes and physical exam questions. Understanding murmur timing, auscultation location, and key differentiating features is essential for success. This guide provides a high-yield breakdown of heart murmurs, their causes, and how to interpret them on exams.

Types of Heart Murmurs

Heart murmurs are categorized based on their timing in the cardiac cycle:

1. Systolic Murmurs (Occur Between S1 and S2)

Murmur	Cause	Auscultation Location	Key Feature
Aortic Stenosis	Calcification, Bicuspid AV	Right 2nd ICS	Crescendo-Decrescendo, radiates to carotids
Mitral Regurgitation	Valve prolapse, LV dilation	Apex (5th ICS MCL)	Holosystolic, radiates to axilla
Tricuspid Regurgitation	RV dilation, endocarditis	Lower left sternal border	Holosystolic, louder with inspiration
VSD	Congenital defect	Lower left sternal border	Harsh, holosystolic
Hypertrophic Cardiomyopathy	LV outflow obstruction	Left sternal border	Increases with Valsalva, decreases with squatting

2. Diastolic Murmurs (Occur Between S2 and S1)

Murmur	Cause	Auscultation Location	Key Feature
Aortic Regurgitation	Aortic root dilation, endocarditis	Left sternal border	Early diastolic, decrescendo
Mitral Stenosis	Rheumatic fever	Apex (5th ICS MCL)	Opening snap, mid-diastolic rumble
Tricuspid Stenosis	Rheumatic disease	Lower left sternal border	Diastolic rumble, louder with inspiration

Mnemonic: "MR. PASS and MVP" vs. "MS. ARD"

• Systolic Murmurs → MR. PASS MVP

  • Mitral Regurgitation

  • Physiologic murmur

  • Aortic Stenosis

  • Systolic

  • Mitral Valve Prolapse

• Diastolic Murmurs → MS. ARD

  • Mitral Stenosis

  • Aortic Regurgitation

  • Diastolic

Heart Murmur Diagnosis: Key Features for the USMLE

Feature	Diagnosis
Crescendo-Decrescendo Murmur	Aortic Stenosis
Holosystolic Murmur Radiating to Axilla	Mitral Regurgitation
Holosystolic Murmur at Left Sternal Border	VSD or Tricuspid Regurgitation
Early Diastolic Decrescendo Murmur	Aortic Regurgitation
Mid-Diastolic Rumble with Opening Snap	Mitral Stenosis

Clinical Cases & Exam Clues

1. USMLE Question Example 1:

   • A 75-year-old man presents with exertional dyspnea, chest pain, and syncope. Physical exam reveals a harsh, crescendo-decrescendo systolic murmur at the right upper sternal border that radiates to the carotids.

   • Diagnosis: Aortic Stenosis

   • Exam Clue: "Syncope + harsh systolic murmur" → Think Aortic Stenosis

2. USMLE Question Example 2:

   • A 30-year-old woman with a history of rheumatic fever presents with dyspnea and palpitations. Physical exam reveals a diastolic murmur with an opening snap at the apex.

   • Diagnosis: Mitral Stenosis

   • Exam Clue: "Opening snap + diastolic murmur" → Think Mitral Stenosis

Heart Murmurs & Maneuvers: USMLE Tips

Maneuver	Effect	Conditions Affected
Valsalva Maneuver	↓ Preload → Increases Hypertrophic Cardiomyopathy murmur	HCM murmur increases
Squatting	↑ Preload & Afterload → Decreases HCM murmur	AS murmur increases
Handgrip	↑ Afterload → Increases MR, AR, VSD murmur	MR & AR murmurs increase

USMLE Key Takeaways

1. Systolic vs. Diastolic Mnemonic: MR. PASS MVP vs. MS. ARD

2. Key Murmur Features:

   • Aortic Stenosis: Crescendo-Decrescendo, radiates to carotids

   • Mitral Regurgitation: Holosystolic, radiates to axilla

   • Aortic Regurgitation: Early diastolic decrescendo

   • Mitral Stenosis: Mid-diastolic rumble with opening snap

3. USMLE Clues: "Syncope + Harsh Murmur" → Aortic Stenosis

4. Murmuers & Maneuvers:

   • Valsalva = HCM louder

   • Squatting = AS louder

   • Handgrip = MR/AR louder

Final Thoughts

Heart murmurs are a high-yield topic for the USMLE, and recognizing their key features can help you tackle exam questions efficiently. Focus on murmur timing, auscultation location, and response to maneuvers to make quick and accurate diagnoses.

For more high-yield USMLE topics, visit King of the Curve for adaptive Q-banks, science visuals, and gamified learning!

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