Feasibility of using synthetic myocardial extracellular volume fraction derived from blood CT attenuation for the differentiation of heart failure

To evaluate the feasibility of using synthetic extracellular volume (sECV) fraction—calculated from synthetic hematocrit (sHCT) derived via blood CT attenuation—as an alternative for conventional ECV in differentiation heart failure (HF). This study prospectively included 120 patients undergoing calcium scoring (CS), coronary CT angiography (CCTA), and late enhancement (LE) imaging (5 min after CCTA), with HCT measured within 24 h. Conventional ECV (cECV) was calculated using serum HCT. An additional retrospective cohort of 207 patients with CS and HCT was analyzed. Linear regression was used to derive sHCT from blood CT attenuation in the left ventricle (LV), right ventricle (RV), and ascending aorta (AO), enabling calculation of sHCT fractions (sECV LV , sECV RV , sECV AO ). Among 64 HF and 56 nonHF patients, cECV was significantly higher in HF cases (36.83 ± 5.75 vs. 30.34 ± 4.88, P < 0.001; AUC = 0.82). The sECV LV , sECV RV and sECV AO showed strong correlations with cECV (R²=0.96, 0.97, and 0.93). HF patients had higher sECV LV (36.79 ± 6.11% vs. 30.42 ± 5.09%, P < 0.001), sECV RV (36.49 ± 6.10% vs. 30.19 ± 4.99%, P < 0.001), and sECV AO (36.87 ± 6.37% vs. 30.23 ± 5.31%, P < 0.001) than nonHF patients. The AUCs for detecting HF using sECV LV , sECV RV and sECV AO were 0.80, 0.79, and 0.80, respectively. Delong test indicated no significant differences among cECV and sECV fractions (all P > 0.05). All ECV fractions showed moderate negative correlations with left ventricular ejection fraction (all P < 0.05). Synthetic ECV fractions derived from cardiac CT are feasible and demonstrate diagnostic performance comparable to conventional ECV fraction in identifying HF.