Photon-counting computed tomography for tissue characterization in patients with hypertrophic cardiomyopathy or amyloidosis

Background Photon-counting computed tomography (CT) is gaining prominence in cardiac imaging, but its potential for tissue characterization in patients with a hypertrophic phenotype remains to be explored, particularly in comparison with the current gold standard, cardiac magnetic resonance (CMR) imaging. Methods Consecutive patients with hypertrophic cardiomyopathy (HCM) or amyloid transthyretin cardiomyopathy (ATTR-CM) followed in the outpatient clinic of a referral center for cardiomyopathies were referred to a photon-counting CT as part of a research protocol. A subgroup of these patients underwent also a CMR scan within 3 months from the date of the CT scan, when deemed clinically indicated. Results Patients with HCM (n=22) were younger than those with ATTR-CM (n=22; p=0.001), while the percentages of men and women did not differ (p=0.966). On CT scan, patients with HCM had lower values of LV mass (p=0.028) and higher LV ejection fraction (p=0.023), while the extracellular volume (ECV) was lower in patients with HCM (p<0.001). The values of iodine density (a measure of the amount of contrast within the myocardial tissue) did not differ between HCM and ATTR-CM (p=0.101). A subgroup of patients (n=27; n=16 with HCM, n=11 with ATTR-CM) underwent also a CMR scan. Patients with HCM displayed tight correlations between LV mass values from CT and CMR (p<0.001, beta=0.869), and maximal wall thickness (p<0.001, beta=0.969), but no significant correlations between ECV values from the two techniques (p=0.275), or between iodine density and CMR-derived ECV (p=0.274). Patients with ATTR-CM showed significant correlations between LV mass values (p<0.001, beta=0.956) and maximal LV wall thickness (p<0.001, beta=0.990) from CT and CMR, but not between ECV values from the two techniques (p=0.139). Conversely, patients with ATTR-CM displayed a close correlation between iodine density and CMR-derived ECV (p=0.016, beta=0.894). Conclusions Photon-counting CT demonstrated strong agreement with CMR for structural parameters (LV mass, maximal wall thickness), supporting its utility for morphologic evaluation. Furthermore, photon-counting CT may hold promise for tissue characterization in patients with ATTR-CM, given the strong concordance between iodine density and CMR-derived ECV.