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Low-flow, low-gradient (LFLG) severe aortic stenosis (AS), despite preserved LVEF, that is, paradoxical LFLG, is one of the most challenging entities in valvular heart disease.1 Hachicha et al were the first to report that patients with small aortic valve area (AVA) and preserved LVEF may concomitantly have an LF and thus often low gradient.1 This new entity is defined as an AVA ≤1.0 cm2 or indexed AVA ≤0.6 cm2/m2, a mean pressure gradient (MPG) <40 mm Hg, an LVEF ≥50% and a stroke volume index (SVi) <35 mL/m2. The most recent European2 and American3 guidelines have recognised paradoxical LFLG AS as an important entity that deserves particular attention and recommend surgery as class IIa indication for surgery if the severity and the relationship with symptoms are confirmed. Recent studies however reported some conflicting results with regard to the natural history and outcomes of paradoxical LFLG AS (online supplement) reflecting the patient heterogeneity and the complexity of this entity.
Refining the concept of paradoxical LFLG AS
It is frequently assumed that normal LVEF implies normal LV systolic function and normal transvalvular flow and, consequently, high transvalvular gradient in the presence of severe AS. However, this common belief has been challenged by several recent studies, which reported that many (20%–50%) patients with AS and normal LVEF, paradoxically, have reduced SVi and thus a low cardiac output and transvalvular flow rate (online supplement). This LF state makes assessment of AS severity more complex because standard resting echocardiography or catheterisation parameters (peak jet velocity, MPG and AVA) may not reflect the true severity of stenosis. Indeed, the gradient, which is highly flow dependent, may be ‘pseudo-normalised’ and thus underestimate the severity of the stenosis.
Initially, this paradox was explained by the concept that patients with severe AS often have pronounced concentric LV remodelling with impaired …
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