Extracellular volume by cardiac CT and the haemodynamic progression of aortic stenosis

Introduction

The rate of aortic stenosis (AS) progression is a major determinant of myocardial damage and adverse clinical outcomes. Sustained pressure overload drives diffuse myocardial fibrosis, which can be quantified non-invasively by computed tomography (CT)-derived extracellular volume (ECV). However, data on ECV changes and AS progression rate are limited.

Methods

Retrospective analysis of patients undergoing cardiac CT for transcatheter aortic valve implantation (TAVI) planning (April 2024–April 2025). A standardized 5-minute delayed dual-energy acquisition was used for ECV quantification. AS progression was evaluated in patients with classical high-gradient severe AS and at least two echocardiographic examinations separated by ≥6 months. AS progression was defined as the annualized change in AS maximum velocity (ΔVmax/year). Rapid progression was defined as ΔVmax > 0.30 m/s/year.

Results

Among 248 patients with available ECV quantification, 134 fulfilled criteria for AS progression analysis. Median age was 80 years [76–84], and 45.5% were male. The median annualized AS progression rate was 0.32 m/s/year [0.15–0.63], and the median ECV was 29.9% [27.0–32.3]. AS progression rate was significantly associated with ECV (Spearman ρ = 0.33, p < 0.001).

In linear regression, ΔVmax/year was associated with higher ECV (β = 2.60; p = 0.001). This association remained statistically significant after adjustment for baseline Vmax (β = 2.39; p = 0.009), for final Vmax (β = 2.79; p = 0.001), and after multivariable adjustment(β = 2.52; p = 0.001). Sensitivity analyses addressing non-linearity using inverse hyperbolic sine transformation and log-shifted progression confirmed consistent associations across all models (all p < 0.001).

When stratified by ECV quartiles, a stepwise increase in progression was observed, with median ΔVmax/year ranging from 0.23 m/s/year in the lowest quartile to 0.54 m/s/year in the highest quartile (p = 0.001). After categorizing patients as rapid (ΔVmax ≥ 0.30 m/s/year) or slow progressors, ECV remained independently associated with rapid progression (OR 1.20 per 1% increase in ECV, 95% CI 1.07–1.34; p = 0.001).

Conclusion

In patients with classical high-gradient AS, higher haemodynamic progression rates were consistently associated with greater myocardial fibrosis measured by CT-derived ECV. ECV identified patients with rapid haemodynamic progression across all approaches, supporting its role as a potential integrative marker of cumulative myocardial injury and a candidate for improving surveillance and timing of intervention.QuartilesREGLINEAR