Normal-flow low-gradient severe aortic stenosis (NF-LG-SAS), defined by aortic-valve area<1cm², mean gradient <40mmHg and indexed stroke volume>35ml/m², is the most prevalent form of low-gradient aortic stenosis (AS). However, the true severity of AS and the management of NF-LG-SAS is controversial. The aim of this study was to evaluate the outcome of patients with NF-LG-SAS compared to patients with moderate AS (MAS), who are considered to be suitable for conservative management.

A total of 520patients were included in this study: 154 with NF-LG-SAS and 366 with MAS (aortic-valve area between 1.0 and 1.3cm²). On Cox multivariate analysis, after adjustment for covariates of prognostic importance, NF-LG-SAS patients did not exhibit an excess risk of mortality compared to MAS patients, under medical management (P=0.45) and under medical and surgical management (P=0.70), even after further adjustment for aortic-valve replacement (AVR) (P=0.56). The 6-year cumulative incidence of AVR (performed in accordance with current guidelines) was comparable between the two groups (39±4% for NF-LG-SAS and 35±3% for MAS, P=0.10). After propensity score matching (n=226), NF-LG-SAS patients and MAS patients also had comparable outcomes under medical (P=0.41), and under medical and surgical management (P=0.52) (Fig. 1).

This study shows that NF-LG-SAS have a comparable outcome to that of MAS when AVR was performed during follow-up according to guidelines, mostly at the stage of high-gradient AS. Rigorous echocardiographic assessment to rule out measurement errors and close follow-up are essential in NF-LG-SAS to detect progression to true severe AS.