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(Circulation. 2006;113:604-606.)
© 2006 American Heart Association, Inc.

Editorial

Assessment of Low-Gradient Aortic Stenosis With Dobutamine

Paul A. Grayburn, MD

From the Department of Internal Medicine, Division of Cardiology, Baylor University Medical Center, Dallas, Tex.

Correspondence to Paul A. Grayburn, MD, Baylor University Medical Center, Baylor Heart and Vascular Institute, 621 N Hall St, Suite H030, Dallas, TX 75226. E-mail paulgr@baylorhealth.edu

Key Words: Editorials • echocardiography • stenosis • surgery • valves

An extract of the first 250 words of the full text is provided, because this article has no abstract.

	Introduction

 
Low-gradient aortic stenosis (AS) has been a vexing problem for cardiologists since its original description in 1980 by Carabello et al.¹ In that study, 3 of 4 patients with low-gradient AS died at surgery, and the other patient had persistent severe heart failure postoperatively. Subsequent studies showed that although operative mortality is high, most patients survive aortic valve replacement (AVR), and some have dramatic improvement in symptoms and left ventricular (LV) function.^2,3 The challenge facing clinicians is how to accurately distinguish those patients who will benefit from AVR from those who will not. The American College of Cardiology/American Heart Association guidelines for valvular heart disease recommend hemodynamic evaluation of low-gradient AS with dobutamine echocardiography to distinguish patients with fixed anatomic AS from those with flow-dependent ("relative") AS in patients with LV dysfunction.⁴ In the latter case, aortic valve area (AVA) is spuriously low because there is not enough forward flow to fully open the leaflets.^5–7 To understand how dobutamine infusion helps sort out the dilemma of low-gradient AS, it is useful to revisit the hemodynamic principles that govern the relationship between AVA, flow, and gradient.

Article p 711

	The Gorlin Formula

 
In 1951, Gorlin and Gorlin proposed the "hydraulic orifice equation" for calculation of valve area in valvular stenosis.⁸ The Gorlin formula was based on the fundamental equation: equation

in which valve area (A) is equal to transvalvular flow (F), divided by transvalvular velocity (V). In AS, the Gorlin formula is used to calculate AVA as: equation

Because transvalvular flow occurs during systole . . . [Full Text of this Article]

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