The dimensionless index (DI) represents the ratio of the LV outflow tract (LVOT) time-velocity integral to that of the aortic valve jet. Other indices are needed to refine the assessment of AS severity in these challenging patients. 5 However, none of these proposed criteria are pathognomonic in patients with LG SAS and preserved LVEF. 1 Among these factors, flow status is of paramount importance indeed, patients with low-flow (LF) LG SAS may have a poor outcome if left untreated (after careful confirmation of the severity of the stenosis) 4, whereas patients with normal-flow (NF) SAS may have a better outcome, similar to patients with moderate AS. 1 Decision-making should also integrate flow status, MPG, ventricular function, size and wall thickness, degree of valve calcification, blood pressure, and functional status to increase the likelihood of SAS in these patients.
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2, 3 As indicated by current guidelines, the diagnosis of SAS in this setting remains challenging and requires careful exclusion of measurement errors. 1 However, up to 40% of patients having AS and a low transvalvular gradient (<40 mm Hg) are in the severe range in terms of AVA, the so-called entity low-gradient (LG) SAS-despite preserved left ventricular (LV) ejection fraction (LVEF). Hence, among patients with LG SAS and preserved left ventricular ejection fraction, calculation of dimensionless index in routine echocardiographic practice may be useful in patients with low flow to identify a subgroup of patients at higher risk of death who may derive benefit from aortic valve replacement.Īccording to current guidelines, severe aortic stenosis (SAS) is classically defined by a transvalvular mean pressure gradient (MPG) >40 mm Hg or peak aortic jet velocity (Vmax) >4 m/s, a condition commonly associated with a reduced aortic valve area (AVA ≤1.0 cm 2 or AVA indexed to body surface area ≤0.6 cm 2/m 2). Dimensionless index <0.25 showed incremental prognostic value in patients with LG–low-flow SAS but not in LG–normal-flow SAS. In this study based on 755 patients with LG SAS (defined by aortic valve area ≤1 cm 2 or aortic valve area indexed to body surface area ≤0.6 cm 2/m 2 and mean aortic pressure gradient <40 mm Hg) and preserved left ventricular ejection fraction, we demonstrated that decreased dimensionless index below the threshold value of 0.25 was strongly related to long-term mortality in patients with LG–low-flow SAS but was not in patients with LG–normal-flow SAS. In these patients, the dimensionless index-the ratio of the left ventricular outflow tract time-velocity integral to that of the aortic valve jet-may improve risk stratification.
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The management of low-flow low-gradient (LG) severe aortic stenosis (SAS) with preserved left ventricular ejection fraction requires careful confirmation of stenosis severity. Customer Service and Ordering Information.Stroke: Vascular and Interventional Neurology.
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Journal of the American Heart Association (JAHA).Circ: Cardiovascular Quality & Outcomes.Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB).