Which factor is a known contributor to underestimation of aortic stenosis severity in LFLG AS?

• A. Reduced LVEF and stroke volume
• B. Increased LV contractility
• C. Elevated LVOT gradient
• D. High arterial pressure (afterload)

Answer: (A)

When the left ventricle is weak and stroke volume is low, the flow across the aortic valve diminishes. The pressure gradient across the valve depends on how much blood is moving through it; with low flow, the mean gradient can be modest even if the valve is truly narrowed. This makes a severe stenosis appear less severe if you rely on gradient alone, which is a hallmark of low-flow, low-gradient aortic stenosis with reduced ejection fraction. In this situation, the valve area can still indicate severe narrowing (≤1.0 cm²) while the gradient is deceptively small.

Increasing LV contractility would push more blood through the valve and raise the gradient, not cause underestimation. A high LVOT gradient is not the main driver of underestimating aortic valve stenosis severity, since it reflects subvalvular conditions rather than the valve itself. While high afterload can reduce forward flow, the most established contributor to underestimation in this context is the combination of reduced LV systolic function and the resulting low stroke volume.