Risk assessment of patients with low-gradient severe aortic stenosis (LG-SAS) despite preserved left ventricular ejection fraction (LVEF) remains challenging.

To evaluate the relationship between the Dimensionless Index (DI) – the ratio of the left ventricular outflow tract (LVOT) time-velocity integral to that of the aortic valve jet – and mortality in patients with LG-SAS and preserved LVEF.

In total, 755 patients with LG-SAS (defined by AVA≤1 cm² and/or AVAi≤0.6cm²/m² and mean aortic pressure gradient<40mmHg) and preserved LVEF≥50% and 593 patients with moderate AS were studied. Flow status was defined according to Stroke Volume Index≤35mL/m (low flow [LF]) or>35mL/m² (normal flow [NF]).

After adjustment for age, gender, body mass index, Charlson Comorbidity Index, history of hypertension, documented coronary artery disease, history of atrial fibrillation, AS-related symptoms, LVEF, indexed LV ventricular mass, aortic valve area (AVA), and aortic valve replacement (AVR) as a time dependent covariate, patients with LG-LF and DI<0.25 exhibited a considerable increased risk of death compared with patients with LG-NF and DI≥0.25 (adjusted HR 2.43 [95% CI: 1.62–3.65]; P<0.001), LG-NF and DI<0.25 (adjusted HR 1.83 [95% CI: 1.23–2.73]; P<0.001), and LG-LF and DI≥0.25 (adjusted HR 2.30 [95% CI: 1.43–3.69]; P<0.001). In contrast, patients with LG-LF and DI≥0.25, LG-NF and DI<0.25, and LG-NF and DI≥0.25 had similar outcome. In addition, among patients with LG-AS, only those with LG-LF SAS and DI<0.25 had a significant increased risk of mortality compared with patients with moderate AS (adjusted HR 2.27 [95% CI: 1.49–3.45]; P<0.001) (Fig. 1).

Among patients with LG severe AS and preserved LVEF, decreased DI<0.25 is a strong parameter in patients with LF to identify a subgroup of patients at higher risk of death who may derive benefit from aortic valve replacement.