Computed tomography-derived myocardial extracellular volume as a prognosis predictor in patients with severe aortic stenosis

Abstract

Abstract Background Patients with severe aortic stenosis (AS) face a higher risk of mortality, but prognosis is still heterogeneous and tools for prioritizing intervention are needed. Myocardial extracellular volume (ECV), measured non-invasively in pre-TAVR computed tomography (CT), is a marker of fibrosis that may reflect the degree of irreversible damage. The aim of this study was to assess the prognostic value of CT- derived ECV (ECVCT) in patients with severe AS referred for TAVR-planning CT. Methods Consecutive patients with severe symptomatic AS undergoing TAVR-planning CT between April and December 2022 at single centre were prospectively included. CT was performed on a 192-slice dual-source 3rdgeneration scanner. ECVCT was acquired during TAVR-planning using an additional post-contrast low-radiation-dose prospective acquisition. ECVCT was calculated as the ratio of change in CT attenuation (Hounsfield units [HU]) of the septal myocardium and the left ventricle (LV) blood pool before and after contrast administration, according to the equation: ECVCT = (1 – hematocrit) x (DHUmyo/DHUblood) – Figure 1A. The primary endpoint was all-cause mortality. The secondary endpoint was a composite endpoint including all-cause mortality and heart failure hospitalization. Results A total of 138 patients were included (mean age 81 ± 7 years; 46% male; mean transaortic gradient 51 ± 15 mmHg; mean aortic valvearea 0.75 ± 0.19 cm2; mean LV ejection fraction (EF) by 2D echocardiogram 57 ± 11%). No patient had a clinical diagnosis of cardiac amyloidosis. Mean ECVCT was 33.9 ± 8.0%. During a median follow-up period of 386 days (IQR 332 – 464), there were 18 deaths (13%), 13 before intervention and 5 after intervention; the secondary endpoint occurred in 26 patients (19%), 17 of which before intervention and 9 after. Patients who attained the primary endpoint were significantly older [81 ± 7 vs. 85 ± 7 years, P = 0.011], had lower left ventricular ejection fraction [51 ± 11 vs. 58 ± 11%, P = 0.015], higher NTproBNP levels [4739 (IQR 2003 – 9970) vs. 751 (IQR 314 – 2541), P <0.001] and higher ECV values (39.9 ± 7.4% vs. 33.0 ± 7.7%, P <0.001). After adjustment for age, LVEF and NTproBNP levels, ECVCT remained an independent predictor of all-cause mortality (adjusted HR 1.09 per 1% ECV increase, 95%CI 1.02 – 1.17, p=0.005 – Figure 1B) and also the secondary endpoint (adjusted HR 1.07 per 1% ECV increase, 95%CI 1.01 – 1.13, p=0.002). Conclusions In this prospective observational cohort study, interstitial fibrosis assessed by CT-derived ECV was associated with poor outcomes in patients with severe AS. ECVCT values may be useful to identify a subgroup of patients with higher risk who may benefit from earlier intervention.