Low-Gradient Aortic Stenosis — RACP Adult Medicine MCQ

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HardCardiologyLow-Gradient Aortic StenosisRACP Adult Medicine

A 55-year-old man with known severe aortic stenosis (AVA 0.6 cm²) and LVEF 30% has a mean gradient of only 25 mmHg (low-flow, low-gradient AS). How is the severity confirmed?

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Correct answer: C — Repeat echocardiography in 6 months

Low-flow, low-gradient aortic stenosis (LVEF <50%, mean gradient <40 mmHg, AVA <1.0 cm²) poses a diagnostic challenge: is the valve truly stenotic (severe AS with reduced flow) or is the low gradient due to pseudo-severe AS (moderate AS that appears severe because the weakened LV cannot open the valve fully)? Dobutamine stress echocardiography differentiates: TRUE severe AS shows increased gradient (>40 mmHg) with persistent small AVA at higher flow rates (contractile reserve); PSEUDO-severe AS shows increased AVA (>1.0 cm²) at higher flow rates. CT aortic valve calcium scoring can also help (calcium score >2000 AU in men or >1200 AU in women supports severe AS). This distinction is critical as true severe AS benefits from valve replacement while pseudo-severe AS does not.

Reference: CSANZ – 2022 – Valvular Heart Disease Guidelines; ESC – 2021 – VHD Guidelines