The Mortality Burden of Untreated Aortic Stenosis

Quick Takes

  • In a very large study using a natural language processing (NLP) algorithm to define aortic stenosis (AS) severity based on echocardiography reports in 595,120 patients, all degrees of AS severity (mild, mild-to-moderate, moderate, moderate-to-severe, and severe) were associated with increased 4-year all-cause mortality.
  • There were low 4-year rates of aortic valve replacement among patients with moderate-to-severe (36.7%) or severe AS (60.7%).

Study Questions:

What are the mortality rates associated with the entire severity spectrum of untreated aortic stenosis (AS)?


A natural language processing (NLP) algorithm was used to define AS severity associated with 1,669,536 echocardiography reports from 1,085,850 patients >18 years of age performed at 24 institutions during 2016–2022; classifying AS as none, mild, mild-to-moderate, moderate, moderate-to-severe, or severe. All-cause mortality was derived from hospital records, and outcomes were evaluated using Kaplan-Meier estimates through 4 years after the index echocardiogram (the first echocardiogram with the most severe degree of AS in the case of multiple echocardiograms). The primary endpoint was all-cause untreated mortality, censoring at the time of treatment of AS or last documented clinical encounter; the secondary endpoint was time to treatment of AS with aortic valve replacement (AVR).


Among 595,120 patients with available AS severity assessment, 70,778 (11.9%) had some degree of AS (5.8% mild, 1.0% mild-to-moderate, 2.4% moderate, 0.6% moderate-to-severe, 2.0% severe) and 524,342 (88.1%) had no AS. Some element of discordance in the assessment of AS severity was present in 22.9% of cases with moderate AS and in 69.8% of cases with moderate-to-severe AS.

The Kaplan-Meier estimates (95% confidence interval) of 4-year unadjusted, untreated, all-cause mortality associated with AS were: no AS 13.5% (13.3%-13.7%), mild AS 25.0% (23.8%-26.1%), mild-to-moderate AS 29.7% (26.8%-32.5%), moderate AS 33.5% (31.0%-35.8%), moderate-to-severe AS 45.7% (37.4%-52.8%), and severe AS 44.9% (39.9%-49.6%). Kaplan-Meier estimates of 4-year observed treatment rates were: no AS 0.2% (0.2%-0.2%), mild AS 1.0% (0.7%-1.3%), mild-to-moderate AS 4.2% (2.0%-6.3%), moderate AS 11.4% (9.5%-13.3%), moderate-to-severe AS 36.7% (31.8%- 41.2%), and severe AS 60.7% (58.0%-63.3%). After adjustment, all degrees of AS severity were associated with increased mortality.


High mortality rates were observed across the entire severity spectrum of untreated AS, and low rates of AVR were observed among patients with severe AS. The authors conclude that earlier diagnosis, intensification of follow-up, and potentially earlier treatment of AS might be needed.


This very large study using an NLP algorithm of echocardiography reports suggests that any degree of AS is associated with excess all-cause mortality (adjusted 4-year estimate 25% among patients with mild AS, progressively increasing to 44% and 42% among patients with moderate-to-severe and severe AS). The observed low rates of intervention among patients with severe (60.7% at 4 years) or moderate-to-severe AS (36.7% at 4 years) is in keeping with multiple past studies, suggesting the ‘undertreatment’ of AS.

This study does not address patient symptoms or whether there was clinical agreement with the NLP-derived assessment of AS severity (incongruously, AVR was performed in 0.2% of patients with no AS and in 1% of patients with mild AS). Although this study is provocative and could add to concerns that less-than-severe AS might be associated with excess mortality, of greatest interest will be results from ongoing prospective clinical trials designed to test whether earlier intervention for AS is clinically beneficial.

Clinical Topics: Noninvasive Imaging, Valvular Heart Disease, Echocardiography/Ultrasound

Keywords: Aortic Valve Stenosis, Echocardiography, TCT23, Transcatheter Cardiovascular Therapeutics

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