There is a shortage of data concerning the natural history of patients with moderate aortic stenosis (AS). The aim of this study was to assess the effect of moderate AS on mortality in the general population and in the subgroups of patients with moderate AS and reduced ejection fractions (EF) and patients with moderate AS and low aortic valve gradients. The study was not designed to address the applicability of treatment in this population.

Outcomes were compared between patients with moderate AS and a propensity-matched cohort (1:3 ratio) without AS. The primary outcome was survival until end of follow-up.

Among approximately 40,000 patients who underwent echocardiographic evaluations between 2011 and 2016, 952 had moderate AS. Median follow-up duration was 181 weeks (interquartile range, 179–182 weeks) for the entire cohort and 174 weeks (interquartile range, 169–179 weeks) for the propensity-matched groups. Propensity matching successfully balanced most preexisting clinical differences. Increased mortality was observed in the group of patients with moderate AS before propensity matching and persisted following propensity matching (median survival 4.1 vs 5.2 years, P = .008). Survival rates and corresponding standard errors at 1, 2, 3, and 5 years were 80 ± 1% versus 82 ± 0.7%, 70 ± 1.5% versus 74 ± 0.8%, 62 ± 1.7% versus 66 ± 0.9%, and 47 ± 2.4% versus 52 ± 1.3%, respectively. A survival difference was similarly observed for the subgroup analyses of moderate AS and reduced ejection fraction (P = .028) and moderate AS and low aortic valve gradients (P = .039).

Moderate AS is associated with increased mortality. The increased mortality was also observed in the subgroups of patients with either reduced ejection fraction or low aortic valve gradients.