Q-Bank Breakdown: Aortic stenosis — Why Every Answer Choice Matters

Aortic stenosis (AS) is one of those Step “bread-and-butter” diagnoses that feels easy—until the question writers start swapping in near-identical murmurs, pulse findings, and cardiomyopathy patterns. The trick isn’t just recognizing AS; it’s knowing why every other answer choice is wrong in that specific vignette.

Tag: Cardiovascular > Valvular Heart Disease

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The vignette (Q-bank style)

A 72-year-old man presents with progressive exertional dyspnea and intermittent chest pressure for 6 months. He had a syncopal episode while climbing stairs last week. Vitals: BP 138/76, HR 86. On exam, carotid pulses are delayed and diminished. Cardiac auscultation reveals a harsh crescendo–decrescendo systolic murmur best heard at the right upper sternal border that radiates to the carotids. The murmur is softer with Valsalva. ECG shows left ventricular hypertrophy.

Which of the following is the most likely diagnosis?

A. Hypertrophic obstructive cardiomyopathy (HOCM)
B. Aortic stenosis
C. Mitral regurgitation
D. Aortic regurgitation
E. Pulmonic stenosis

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Correct answer: B. Aortic stenosis

Why AS fits this vignette

This stem basically drops the classic triad and the classic exam:

1) Symptoms: the SAD triad

• Syncope (especially exertional)
• Angina
• Dyspnea/heart failure symptoms

These happen because AS creates fixed outflow obstruction → the heart can’t appropriately increase cardiac output with exercise.

2) Murmur pattern: crescendo–decrescendo systolic at the RUSB radiating to carotids

• Location: right upper sternal border (aortic area)
• Radiation: carotids (big clue)
• Timing: systolic ejection murmur

3) Pulses: pulsus parvus et tardus

• “Parvus” = small amplitude
• “Tardus” = delayed upstroke
  This is a high-yield physical finding tied to severe AS.

4) Maneuvers: softer with Valsalva

• Valsalva decreases preload → less flow across the stenotic valve → AS murmur decreases
• This is also how you separate it from HOCM (which gets louder with Valsalva)

5) Downstream effect: LVH on ECG

AS → pressure overload → concentric LV hypertrophy.

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High-yield AS facts (Step 1 + Step 2)

Etiologies by age

Hemodynamics to remember

• AS increases afterload → LV pressure rises
• Compensatory concentric hypertrophy maintains EF early
• Eventually → diastolic dysfunction, ischemia (even without CAD), HF

Management (high yield for Step 2)

• Definitive treatment: valve replacement (SAVR or TAVR) when symptomatic severe AS or reduced EF
• Avoid nitrates/diuretics in a way that drops preload too much in severe AS (can precipitate syncope/hypotension)
• Key concept: severe symptomatic AS is a “do not miss” because once symptoms appear, mortality rises sharply without valve intervention

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Now crush the distractors (why each one is wrong)

A. Hypertrophic obstructive cardiomyopathy (HOCM)

Why it’s tempting: Also causes exertional syncope and systolic murmur.

Why it’s wrong here:

• HOCM murmur is best at the left lower sternal border (not RUSB).
• Maneuver tells the story: HOCM gets louder with Valsalva/standing (less preload → more obstruction).
  • In this vignette, murmur is softer with Valsalva, supporting AS.
• Carotid pulse in HOCM can show bisferiens (spike-and-dome), not classic parvus et tardus.

HOCM hallmarks you should recall

• Young athlete with syncope, family history of sudden death
• Harsh systolic murmur that increases with decreased preload
• Asymmetric septal hypertrophy; systolic anterior motion (SAM) of mitral valve

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C. Mitral regurgitation (MR)

Why it’s tempting: Systolic murmur + dyspnea is a common pairing.

Why it’s wrong here:

• MR is holosystolic (pan-systolic), not crescendo–decrescendo.
• Best heard at the apex and typically radiates to the axilla, not the carotids.
• MR often produces signs of volume overload (possible S3) rather than classic carotid upstroke abnormalities.

High-yield MR associations

• MVP (myxomatous degeneration), ischemic papillary muscle dysfunction/rupture, rheumatic disease, endocarditis

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D. Aortic regurgitation (AR)

Why it’s tempting: Aortic valve disease; can cause exertional dyspnea.

Why it’s wrong here:

• AR classically has an early diastolic decrescendo blowing murmur along the left sternal border.
• Pulse findings are the opposite of AS:
  • AR → bounding pulses, wide pulse pressure
  • AS → weak/delayed pulses, relatively narrow pulse pressure
• AR may have Austin Flint murmur (low-pitched diastolic rumble at apex) in severe cases.

High-yield AR causes

• Aortic root dilation (Marfan, tertiary syphilis, aortitis), bicuspid valve, endocarditis

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E. Pulmonic stenosis (PS)

Why it’s tempting: Another systolic ejection murmur with crescendo–decrescendo shape.

Why it’s wrong here:

• PS is loudest at the left upper sternal border, often with radiation to the back.
• You’d look for right ventricular heave, signs of right-sided pressure overload, and possibly cyanosis depending on severity/associated congenital disease.
• The vignette screams left-sided pathology: LVH on ECG, carotid pulse abnormalities, murmur radiating to carotids.

High-yield PS association

• Congenital (e.g., Noonan syndrome), often presents earlier in life

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Rapid-fire “murmur differentiators” table (worth memorizing)

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Exam-day takeaway (what the question is really testing)

When a stem gives you:

• SAD symptoms (syncope, angina, dyspnea),
• RUSB systolic ejection murmur radiating to carotids,
• pulsus parvus et tardus, and
• murmur decreases with Valsalva,

…it’s not just “pick aortic stenosis.” It’s “prove it by beating HOCM, MR, AR, and PS using timing, location, radiation, pulse findings, and maneuvers.”