Relation of Dimensionless Index to Long-Term Outcome in Aortic Stenosis With Preserved LVEF

Abstract

Objectives: The aim of this study was to assess the role of the dimensionless index (DI) in a registry of patients with aortic stenosis (AS) to objectively establish prognostic DI thresholds for various degrees of AS severity.

Background: DI is a classic marker of severity in AS that does not rely on the estimation of the left ventricular outflow tract (LVOT) cross-sectional area. Although DI estimation is straightforward, its outcome implications have never been tested in the context of routine clinical practice.

Methods: This analysis includes 488 patients with preserved (≥50%) ejection fraction and no or minimal subjective symptoms, diagnosed with ≥ mild AS. DI was computed as the ratio of the LVOT time-velocity integral to that of the aortic valve jet, and on the basis of the correlation with peak aortic jet velocity, the population was divided into 3 groups: DI <0.20, DI 0.20 to 0.25, and DI >0.25.

Results: The 5-year survival free of events (death or need for aortic valve replacement) was 56 ± 3% for DI >0.25, 41 ± 6% for DI 0.20 to 0.25, and 22 ± 5% for DI <0.20 (p for trend <0.001). The risk of events increased linearly with DI <0.25 (adjusted hazard ratio [HR]: 1.14; 95% confidence interval [CI]: 1.05 to 1.29) per 0.05 DI decrement; p = 0.015). On multivariable analysis, compared with patients with DI >0.25, those with DI 0.20 to 0.25 and those with DI <0.20 incurred an excess risk of events (adjusted HR: 1.65; 95% CI: 1.20 to 2.27 for DI 0.20 to 0.25 vs. DI >0.25, and adjusted HR: 2.62; 95% CI: 1.90 to 3.63 for DI <0.20 vs. DI >0.25). The association of DI and outcome was consistent in subgroups, with no interaction between DI outcome prediction and LVOT diameter, body surface area, or index stroke volume (all p for interaction ≥0.10) CONCLUSIONS: Our results demonstrate that the DI is a simple and reliable marker of AS severity with clear prognostic implications. DI <0.25 is associated with an excess risk of events after diagnosis; therefore, this cutoff should be used for AS severity assessment and for therapeutic decisions.

Keywords: aortic stenosis; dimensionless index; echocardiography; outcome.