Estimation of myocardial fibrosis by extracellular volume fraction measurement with cardiac CT in patients undergoing transcatheter aortic valve implantation

Introduction:

Previous studies have evaluated cardiac fibrosis by measuring extracellular volume fraction (ECV) mainly through MRI based T1-mapping. ECV evaluation through cardiac computed tomography (CT) is an evolving technique which might add important information about the extent of fibrosis. Serum level of Galectin-3, a marker of fibrosis, was shown to be correlated with the extent of fibrosis. We aimed to evaluate the feasibility, diagnostic performance, and clinical correlation of ECV measurement by cardiac CT in patients with severe aortic stenosis (AS) compared with normal subjects.

Methods:

Seventy-five consecutive patients with severe AS and 19 normal subjects were prospectively recruited and underwent a unique pre-contrast and post-contrast cardiac CT for estimation of ECV within the myocardium. Blood sample was obtained at the day of CT and serum level of Galectin-3 was measured by a dedicated laboratory. 2-D echocardiography was performed to evaluate the extent of cardiac damage.

Results:

Patients with AS were older (80.6 vs 57.2) and had more comorbidities compared with normal subjects. ECV was significantly higher in patients with AS compared with normal subjects (40% vs. 21.6% respectively,p<0.0001), and this difference remained significant after multivariate analysis. ECV correlated significantly with functional class (FC) at baseline, atrial volume, ejection fraction and AS echocardiographic staging (R=0.34,0.34,0.42,and 0.29 respectively;p<0.01 for all). ECV correlated with clinical outcomes including stroke, FC and hospitalizations due to heart failure at 6 and 12 months. ECV had a favorable receiver operating curve for the prediction of a combined clinical outcome of stroke/HF hospitalization/mortality at 12 months (fig 1). A borderline correlation between serum level of Galectin-3 and ECV was observed (p=0.07).

Conclusion:

CT estimation of ECV in patients with severe AS is feasible and associated with several functional echocardiographic parameters and clinical outcomes. Implementation of this novel technique might aid in the risk stratification process before TAVI.