Low-gradient, low ejection fraction aortic stenosis (AS) represents about 5–10% of all cases of severe AS and is the most challenging subgroup of patients to manage.1 2 The term low-gradient, low ejection fraction AS is usually applied to patients with a mean gradient <30 mm Hg (or 40 mm Hg), an aortic valve area (AVA) <1 cm², and an ejection fraction (EF) <35% (or 40%).1^–7 Low EF in such patients may be caused by severe low-flow AS with inadequate compensatory left ventricular hypertrophy, called afterload mismatch, but also by another myocardial disease (such as extensive fibrosis, associated cardiomyopathy or myocardial infarction (MI)),5 in which case, AS is not the primary problem. The essential difficulty for clinicians is to distinguish true severe low-flow AS, responsible for low EF, from pseudo-severe AS comprising mild-to-moderate AS associated with another cause of left ventricular dysfunction (LVD). A very low gradient may be seen in true severe low-flow AS, while the decreased AVA seen in pseudo-severe AS reflects poor opening of the aortic valve directly related to low transvalvular flow. For the clinician, the two main questions in low-gradient, low ejection fraction AS are: How severe is the AS? Which patients can benefit from surgery?

HOW SEVERE IS THE AORTIC STENOSIS?

Determining the true severity of low-gradient, low ejection fraction AS may be a challenging problem. Physical examination is often misleading with a soft systolic ejection murmur despite severe AS. Echocardiography is the key examination for visualising the aortic valve, and measuring the maximum aortic velocity, pressure gradient, valve resistance, AVA and EF. As initially reported by deFilippi …