Dobutamine challenge for low-gradient aortic stenosis.

Abstract

In adults with valvular aortic stenosis (AS), valve replacement is recommended in the presence of symptoms and severely reduced aortic valve area (AVA).1 In such patients, valve replacement improves symptoms and survival, even in the setting of left ventricular (LV) dysfunction. LV dysfunction in severe AS is usually due to afterload mismatch; valve replacement relieves the afterload excess imposed by the stenotic valve and improves LV performance. 2 However, a subset of patients with “ severe” AS, LV dysfunction, and low-transvalvular gradient has been reported to have a relatively high operative mortality and poor prognosis.2–4⇓⇓ This clinical scenario has been termed “low-flow, low-gradient AS.” Accurate assessment of AVA in such patients is difficult because (1) calculated AVA is directly proportional to forward stroke volume, and (2) the Gorlin constant varies at low-flow states. 5–7⇓⇓ Some patients with low-flow, low-gradient AS have a reduced AVA as a result of inadequate forward stroke volume rather than anatomic stenosis, a situation analogous to reduced anterior mitral leaflet excursion in dilated cardiomyopathy where there is not enough forward flow to fully open the valve. For example, Cannon et al 8 showed that some patients with low-gradient AS were found to have only mild AS at surgery despite a Gorlin AVA indicating critical AS. Obviously, surgical therapy is unlikely to benefit such patients because their primary pathology is a cardiomyopathy. On the other hand, patients with severe anatomic AS may benefit from valve replacement despite the increased operative risk associated with a low-flow, low-gradient hemodynamic state. The recent American College of Cardiology/American Heart Association (ACC/AHA) guidelines for managing valvular heart disease recommends hemodynamic evaluation of low-flow, low-gradient AS using dobutamine echocardiography to distinguish patients with fixed anatomic AS from those with flow-dependent (“ relative”) AS in patients with LV …