Background: Right ventricular (RV) extracellular volumes (ECVs), as a surrogate for histologic fibrosis, have not been sufficiently investigated. Purpose: To evaluate and compare RV and left ventricular (LV) ECVs obtained with dual-layer spectral detector CT (DLCT) in chronic thromboembolic pulmonary hypertension (CTEPH) and investigate the clinical importance of RV ECV. Materials and Methods: Retrospective analysis was performed on data from 31 patients with CTEPH (17 were not treated with pulmonary endarterectomy [PEA] or balloon pulmonary angioplasty [BPA] and 14 were) and eight control subjects who underwent myocardial delayed enhancement (MDE) DLCT from January 2019 to June 2020. The ECVs in the RV and LV walls were calculated by using iodine density as derived from spectral data pertaining to MDE. Statistical analyses were performed with one-way repeated analysis of variance with the Tukey post hoc test or the Kruskal-Wallis test with the Steel-Dwass test and linear regression analysis. Results: The PEA- and BPA-naive group showed significantly higher ECVs than the PEA- or BPA-treated group and control group in the septum (28.2% 6 2.9 vs 24.3% 6 3.6, P =.005), anterior right ventricular insertion point (RVIP) (32.9% 6 4.6 vs 25.3% 6 3.6, P,.001), posterior RVIP (35.2% 6 5.2 vs 27.3% 6 4.2, P,.001), mean RVIP (34.0% 6 4.2 vs 26.3% 6 3.4, P,.001), RV free wall (29.5% 6 3.3 vs 25.9% 6 4.1, P =.036), and mean RV wall (29.1% 6 3.0 vs 26.1% 6 3.1, P =.029). There were no significant differences between the PEA- or BPA-treated group and control subjects in these segments (septum, P =.93; anterior RVIP, P =.38; posterior RVIP, P =.52; mean RVIP, P =.36; RV free wall, P =.97; and mean RV, P =.33). There were significant correlations between ECV and mean pulmonary artery pressure (PAP) or brain natriuretic peptide (BNP) in the mean RVIP (mean PAP: R = 0.66, P,.001; BNP: R = 0.44, P =.014) and the mean RV (mean PAP: R = 0.49, P =.005; BNP: R = 0.44, P =.013). Conclusion: Right ventricular and right ventricular insertion point extracellular volumes could be noninvasive surrogate markers of disease severity and reverse tissue remodeling in chronic thromboembolic pulmonary hypertension.
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