Outcome of Normal‐Flow Low‐Gradient Severe Aortic Stenosis With Preserved Left Ventricular Ejection Fraction: A Propensity‐Matched Study

BACKGROUND: Normal‐flow, low‐gradient severe aortic stenosis (NF‐LG‐SAS), defined by aortic valve area <1 cm(2), mean gradient <40 mm Hg, and indexed stroke volume >35 mL/m(2), is the most prevalent form of low‐gradient aortic stenosis (AS). However, the true severity of AS and the management of NF‐LG‐SAS are controversial. The aim of this study was to evaluate the outcome of patients with NF‐LG‐SAS compared with moderate AS (MAS) and with high‐gradient severe‐AS (HG‐SAS). METHODS AND RESULTS: A total of 154 patients with NF‐LG‐SAS, 366 with MAS (aortic valve area between 1.0 and 1.3 cm(2)), and 1055 with HG‐SAS were included. On multivariate analysis, after adjustment for covariates of prognostic importance, NF‐LG‐SAS patients did not exhibit an excess risk of mortality compared with MAS patients under medical management (hazard ratio=1.13 [95% CI, 0.82‐1.56]; P=0.45) and under medical and surgical management (hazard ratio 1.06 [95% CI, 0.79‐1.43]; P=0.70), even after further adjustment for aortic valve replacement (hazard ratio=1.09 [95% CI, 0.81‐1.48]; P=0.56). The 6‐year cumulative incidence of aortic valve replacement (performed in accordance with guidelines) was comparable between the 2 groups (39±4% for NF‐LG‐SAS and 35±3% for MAS, P=0.10). After propensity score matching (n=226), NF‐LG‐SAS and MAS patients also had comparable outcomes under medical (P=0.41) and under medical and surgical management (P=0.52). NF‐LG‐SAS had better outcomes than HG‐SAS patients (adjusted hazard ratio 1.84 [95% CI, 1.18‐2.88]; P<0.001). CONCLUSIONS: This study shows that patients with NF‐LG‐SAS have a comparable outcome to those with MAS when aortic valve replacement is performed during follow‐up according to guidelines, mostly at the stage of HG‐SAS. Rigorous echocardiographic assessment to rule out measurement errors and close follow‐up are essential to detect progression to true severe AS in NF‐LG‐SAS.