Size-adjusted aortic valve area: refining the definition of severe aortic stenosis

Severe aortic valve stenosis (AS) is defined by an aortic valve area (AVA) <1 cm² or an AVA indexed to body surface area (BSA) <0.6 cm/m², despite little evidence supporting the latter approach and important intrinsic limitations of BSA indexation. We hypothesized that AVA indexed to height (H) might be more applicable to a wide range of populations and body morphologies and might provide a better predictive accuracy.

In 1298 patients with degenerative AS and preserved ejection fraction from three different countries and continents (derivation cohort), we aimed to establish an AVA/H threshold that would be equivalent to 1.0 cm² for defining severe AS. In a distinct prospective validation cohort of 395 patients, we compared the predictive accuracy of AVA/BSA and AVA/H. Correlations between AVA and AVA/BSA or AVA/H were excellent (all R² > 0.79) but greater with AVA/H. Regressions lines were markedly different in obese and non-obese patients with AVA/BSA (P < 0.0001) but almost identical with AVA/H (P = 0.16). AVA/BSA values that corresponded to an AVA of 1.0 cm² were markedly different in obese and non-obese patients (0.48 and 0.59 cm²/m²) but not with AVA/H (0.61 cm²/m for both). Agreement for the diagnosis of severe AS (AVA < 1 cm²) was significantly higher with AVA/H than with AVA/BSA (P < 0.05). Similar results were observed across the three countries. An AVA/H cut-off value of 0.6 cm²/m [HR = 8.2(5.6–12.1)] provided the best predictive value for the occurrence of AS-related events [absolute AVA of 1 cm²: HR = 7.3(5.0–10.7); AVA/BSA of 0.6 cm²/m² HR = 6.7(4.4–10.0)].

In a large multinational/multiracial cohort, AVA/H was better correlated with AVA than AVA/BSA and a cut-off value of 0.6 cm²/m provided a better diagnostic and prognostic value than 0.6 cm²/m². Our results suggest that severe AS should be defined as an AVA < 1 cm² or an AVA/H < 0.6 cm²/m rather than a BSA-indexed value of 0.6 cm²/m².