Low-flow, low-gradient aortic stenosis: an understanding is still a long way off

Low-gradient (LG) aortic stenosis (AS) is estimated to account for at least one-third of all presentations in patients with suspected severe AS. Even though frequently encountered in clinical practice, patients with LG-AS are less likely to be referred for aortic valve replacement (AVR) compared to those with high-gradient (HG) AS, despite evidence to suggest a survival benefit with AVR over conservative management1. At least part of this therapeutic inertia is no doubt secondary to the ongoing diagnostic challenge associated with the correct adjudication of stenosis severity in patients presenting with discordant markers of AS severity on initial transthoracic echocardiography. Current society guidelines advocate a stepwise integrated approach for the diagnosis of LG-AS, utilising dobutamine stress echocardiography (DSE) and/or computed tomography calcium score, in patients with an aortic valve area <1 cm2 and a mean gradient <40 mmHg2. These additional diagnostic modalities are intended to classify patients into 1 of 2 dominant patterns in LG-AS: classical low-flow, LG-AS (cLFLG-AS), in patients with a depressed left ventricular ejection fraction (LVEF; <50%), and paradoxical LFLG-AS (pLFLG-AS), in those with a normal...