Normal-flow low-gradient severe aortic stenosis (NF-LG-SAS), defined by aortic valve area (AVA)<1cm², mean pressure gradient (MPG) <40mmHg and indexed stroke volume (SVi)≥35ml/m², is the most prevalent form of low-gradient aortic stenosis (AS). However, the true severity of AS in these patients is controversial. The aim of this Doppler echocardiographic study was to investigate changes over time in the hemodynamic severity of patients with NF-LG-SAS features, and preserved ejection fraction (PEF).

We retrospectively identified in 2 academic centers 46patients who had 2 Doppler echocardiographic examinations without an intervening event. After a median follow-up of 26 (interquartile range [IQR] 18–52) months, progression was observed with increase in transaortic MPG (from 30 [27–34] to 43 [35–52]mm Hg; P<0.001), peak aortic jet velocity (from 3.53 [3.30–3.73] to 4.17 [3.78–4.48]m/s; P<0.001), and decrease in AVA (from 0.88 [0.82–0.94] to 0.71 [0.62–0.80]cm²; P<0.001). Annual rates of progression were, respectively, 5mm Hg/year, 0.26m/s/year, and −0.05cm²/year. EF slightly decreased from 65% (62–69) to 64% (57–66), P=0.04. At follow-up, 26patients (57%) acquired the features of classical high gradient severe AS (MPG≥40mm Hg and peak aortic jet velocity≥4.00m/s) (Table 1).

This study shows that most patients with NF-LG-SAS and PEF exhibit significant hemodynamic progression of AS severity parameters, with slight ejection fraction impairment. These findings suggest that NF-LG-SAS with PEF is an intermediate stage between moderate AS and classical high gradient severe AS.