Symptomatic Low-Gradient Severe Aortic Stenosis With Preserved Left Ventricular Ejection Fraction

Abstract

Accurate assessment of aortic stenosis (AS) severity is one of the more technically demanding studies in echocardiography. This is reflected in the Intersocietal Accreditation Commission for Echocardiography standards that specify that AS gradients must be measured from at least 3 different transducer positions and with a nonimaging, dedicated, continuous-wave Doppler transducer (Pedhoff). The standards do not specify the measurement of any other valvular lesion. Submission and review of AS cases is required for laboratory accreditation by that body. Given the complexity in echocardiographic assessment, the determination that a patient has severe AS (defined as a valve area ≤1 cm2 or an indexed area ≤0.6 cm2/m2) but a mean gradient <40 mm Hg despite a preserved left ventricular (LV) ejection fraction (LVEF) is often met with skepticism by our interventional colleagues. Low-gradient severe AS resulting from decreased LV systolic function can be assessed by dobutamine protocols intended to increase the flow across the valve and to distinguish true AS from pseudo-AS.1 Such is usually not the case in patients with preserved LVEF. Article see p 622 Work by a group in Quebec has highlighted the existence of paradoxical low-gradient severe AS (LGSAS) in patients with preserved LVEF but paradoxically low stroke volume.2 The low stroke volume is presumably attributable to a small LV cavity that has been infringed on by LV hypertrophy and decreased myocardial function that has not yet resulted in a decreased LVEF. Milano et al3 performed intraoperative myocardial biopsies on patients undergoing aortic valve replacement (AVR) for AS and demonstrated that those patients with moderate fibrosis had much poorer long-term outcome despite normal LVEF compared with patients with no or mild fibrosis. Other groups have confirmed fibrosis and myocardial dysfunction in these patients with magnetic resonance imaging to assess …