Heart Murmur Auscultation: A Pattern-First Approach

Heart murmurs are one of the most commonly tested physical exam findings on USMLE Step 1. They appear across pathophysiology questions, diagnostic workups, and management decisions. Yet many students report murmurs as their weakest cardiovascular topic.

The root cause is almost always the same: students memorize murmur descriptions as isolated facts instead of learning the two underlying patterns that generate every murmur.

The Two Fundamental Patterns

Pattern 1: Timing — Systolic vs. Diastolic

This is your first branch point and it cuts the differential in half instantly.

Systolic murmurs (between S1 and S2): The ventricles are contracting. Blood is either being ejected forward through a stenotic semilunar valve or leaking backward through an incompetent AV valve.

• Aortic stenosis — Crescendo-decrescendo systolic murmur, best at the right upper sternal border, radiating to the carotids
• Pulmonic stenosis — Crescendo-decrescendo systolic murmur, best at the left upper sternal border
• Mitral regurgitation — Holosystolic (pansystolic) murmur, best at the apex, radiating to the axilla
• Tricuspid regurgitation — Holosystolic murmur, best at the left lower sternal border, increases with inspiration (Carvallo sign)
• Mitral valve prolapse — Mid-systolic click followed by a late systolic murmur

Diastolic murmurs (between S2 and S1): The ventricles are filling. Blood is either flowing forward through a stenotic AV valve or leaking backward through an incompetent semilunar valve.

• Mitral stenosis — Low-pitched diastolic rumble with opening snap, best at the apex, best heard with the bell in the left lateral decubitus position
• Aortic regurgitation — Early diastolic decrescendo blowing murmur, best at the left sternal border, sitting up and leaning forward

Key rule: diastolic murmurs are always pathologic. Systolic flow murmurs can be innocent (especially in children, pregnant women, and anemic patients).

Pattern 2: Maneuvers Change Murmurs Predictably

The USMLE loves asking how maneuvers affect murmurs. Rather than memorizing each combination, understand the two variables at play:

1. Preload (venous return / volume in the ventricle)
2. Afterload (resistance the ventricle pumps against)

Most murmurs get louder when more blood flows through the abnormal valve — i.e., increased preload or increased forward flow. The two critical exceptions are:

• Hypertrophic cardiomyopathy (HCM) — Gets louder with decreased preload (standing, Valsalva) because the septum and mitral valve get closer together, worsening the outflow obstruction
• Mitral valve prolapse (MVP) — Click moves earlier and murmur lengthens with decreased preload (standing, Valsalva) because less blood in the ventricle means the leaflet prolapses sooner

This means: if the question says the murmur gets louder with Valsalva or standing, the answer is either HCM or MVP. Everything else gets quieter with those maneuvers.

High-Yield Associations

• Young woman from Central America with dyspnea on exertion + diastolic rumble → Rheumatic mitral stenosis
• Elderly patient with syncope + crescendo-decrescendo systolic murmur + pulsus parvus et tardus → Calcific aortic stenosis
• IV drug user with fever + holosystolic murmur at LLSB increasing with inspiration → Tricuspid regurgitation (right-sided endocarditis)
• Marfan syndrome + early diastolic blowing murmur → Aortic root dilation → Aortic regurgitation
• Young athlete with syncope during exertion + systolic murmur that increases with Valsalva → Hypertrophic cardiomyopathy

The 30-Second Murmur Algorithm

1. Is it systolic or diastolic? (Cuts differential in half)
2. Where is it loudest? (Localizes the valve)
3. Does it radiate? (Aortic stenosis → carotids; mitral regurgitation → axilla)
4. What happens with maneuvers? (Valsalva louder = HCM or MVP; everything else = quieter)

Run this algorithm on every murmur question. With USMLAI's cardiology module, you can practice this sequence on hundreds of adaptive murmur vignettes until the algorithm becomes reflexive.