Therapeutic Management of Low-Gradient Aortic Stenosis
First Assess the State of the Schrödinger Cat Before Making a Decision
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According to current guidelines,1–3 severe aortic stenosis (AS) is defined by a mean gradient >40 mm Hg, a peak aortic jet velocity >4 m/s, and an aortic valve area <1 cm2. However, the evaluation of AS severity is often rendered more complex by the concomitance of low gradient/velocity (ie, <40 mm Hg/<4 m/s) and small aortic valve area (ie, ≤1 cm2), which is also referred as discordant grading or low-gradient severe AS. In the Schrödinger experiment, the Copenhagen theoretical interpretation of quantum mechanics implies that after a while, the cat placed in a sealed box with a flask of poison, and a radioactive source, is simultaneously alive and dead, which is referred as quantum superposition and is, of course, impossible. Similarly, AS of a patient with low-gradient AS cannot be simultaneously severe and nonsevere.
See Article by Taniguchi
Discordance Between Echocardiographic Markers of AS
In the large CURRENT AS registry (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis; 3809 patients) published by Taniguchi et al4 in this issue of Circulation: Cardiovascular Interventions, 45% of the patients had a discordance between the aortic valve area (ie, small) and the mean gradient or the peak aortic jet velocity (ie, low). This percentage actually represents the average of the wide range of prevalence (25%–60%) of discordant grading reported in the literature.5–10
This discordant grading pattern with low gradient may occur in the 3 following situations: (1) low ejection fraction, (2) normal ejection fraction with low flow, and (3) normal ejection fraction with normal flow.11 In the first case scenario with low ejection fraction (ie, classical low flow), it is well known and accepted that the stenosis may be severe despite the presence of a low gradient/velocity.12–14 The second scenario, that is, …