In severe aortic stenosis, which haemodynamic parameter is used to distinguish 'truly severe' low-flow, low-gradient AS with reduced EF (paradoxical low-flow) from pseudo-severe AS?
- A Peak aortic velocity >4 m/s at rest regardless of EF
- B Aortic valve calcium score by CT <800 AU excludes severe AS
- C Dobutamine stress echo demonstrating AVA increase <0.2 cm² with increased flow (pseudo-severe) vs valve area remaining <1.0 cm² (truly severe) ✓
- D Brain natriuretic peptide (BNP) >500 pg/mL confirms true severity
Correct answer: C. Dobutamine stress echo demonstrating AVA increase <0.2 cm² with increased flow (pseudo-severe) vs valve area remaining <1.0 cm² (truly severe)
Explanation
In low-flow, low-gradient AS with reduced EF (LFLG-AS), the gradient is low due to poor LV contractility rather than truly mild stenosis. Dobutamine stress echo increases transvalvular flow: in truly severe AS, increased flow through a fixed stenotic valve maintains AVA <1.0 cm² while gradient rises; in pseudo-severe AS (moderate stenosis + poor LV function), increased flow opens the leaflets more, and AVA increases >0.2 cm². CT calcium score ≥1600 AU (women: ≥800 AU) is another approach for confirming severe AS in low-gradient AS per 2021 ESC guidelines.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.