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Dimensionless Index in AS — EECC MCQ

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HardHeart FailureDimensionless Index in ASEECC

A 70-year-old man with HFrEF (LVEF 30%) and moderate aortic stenosis (AVA 1.1 cm², mean gradient 25 mmHg) asks whether his AS could be worsening his HF. The cardiology fellow measures the dimensionless index (DI). What is this parameter?

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Correct answer: C — The dimensionless index (velocity ratio) is the ratio of LVOT VTI to aortic valve VTI; a DI <0.25 suggests severe AS and is flow-independent, making it valuable when LVEF is reduced and gradients are low

The dimensionless index (DI, also called velocity ratio) is the ratio of the LVOT VTI (or peak velocity) to the aortic valve VTI (or peak velocity). It is equivalent to the ratio of LVOT area to AVA by the continuity equation, but importantly does NOT require LVOT diameter measurement (which is a major source of error in AVA calculation). A DI <0.25 is consistent with severe AS. Its key advantage in HFrEF is that it is flow-independent — in low-flow states where gradients are misleadingly low and AVA may appear small due to incomplete valve opening (pseudo-severe AS), the DI remains accurate. The 2025 ESC VHD Guidelines recommend the DI alongside dobutamine stress echo and CT calcium scoring for evaluating low-flow, low-gradient AS.

Reference: ESC/EACTS (2025): VHD Guidelines; ASE/EACVI Echo Guidelines