Extracellular Volume Remodeling After Transcatheter Aortic Valve Implantation: Factors Associated With Indexed Extracellular Volume Worsening

Background Data remain limited regarding whether extracellular volume (ECV) measured by computed tomography (CT) changes after transcatheter aortic valve implantation (TAVI), and which clinical factors may be associated with its temporal evolution. Aims The aim of this study was to evaluate changes in ECV after TAVI and to identify factors associated with these changes. Methods This retrospective, single‐center, hypothesis‐generating study included consecutive patients with severe aortic stenosis (AS) who underwent TAVI at Osaka University Hospital between March 2023 and January 2025 and had cardiac CT with delayed enhancement performed before the procedure and at 6‐month follow‐up. Left ventricular mass index (LVMi), indexed ECV, and indexed cellular volume were assessed by CT. Results Fifty‐five patients were included in the final analysis. At 6 months after TAVI, LVMi decreased significantly, with a median relative reduction of 21%. Both indexed ECV and indexed cellular volume decreased significantly, with median relative reductions of 15% and 22%, respectively. Because the reduction in indexed cellular volume exceeded that in indexed ECV, the ECV fraction increased significantly at follow‐up. An increase in indexed ECV at 6 months was observed in 16.4% of the cohort and was associated with worsening aortic regurgitation. Conclusions At 6 months after TAVI, CT‐derived indexed ECV was significantly reduced, suggesting early modification of the myocardial interstitium. In contrast, suboptimal hemodynamic relief may be associated with less favorable remodeling.