Aortic stenosis (AS) remains a common and important clinical entity and, when severe, is associated with significant morbidity and mortality. Fortunately, definitive surgical therapies have been developed that have significantly altered the natural history of this disease. The clinical challenge is to accurately assess AS severity and identify patients who are most likely to benefit from aortic valve replacement. Both the American and European cardiac societies define severe AS as that associated with an aortic valve area (AVA) of 40 mm Hg, and a peak transvalvular flow velocity of >4.0 m/s.1,2 Moderate AS is defined as an AVA of 1.0 to 1.5 cm2, a mean gradient of 25 to 40 mm Hg, and a peak velocity of 3.0 to 4.0 m/s, whereas mild AS is associated with less significant abnormalities in these parameters. The classification of stenotic severity, however, is not always so straightforward, and patients are frequently encountered for whom the clinical data are conflicting, including those with AVA in the severe range but with low transvalvular gradient (<40 mm Hg) and low transvalvular flow (<35 mL/m2). These patients with low-flow low-gradient AS (LFLG AS) account for a significant proportion of patients who present for evaluation of severe aortic stenosis. Article see p 27 The majority of patients with LFLG AS have reduced left ventricular ejection fraction (LVEF <50%) and have either severe AS and resultant LV failure (“true AS”) or lesser degrees of AS and an unrelated cardiomyopathy (“pseudo-AS”). These 2 entities can often be distinguished through the use of an inotropic challenge3; however, a significant minority of patients with LFLG AS have low transvalvular flow (<35 mL/m 2 ) despite preserved LVEF and have been referred to as having “paradoxical …