When cardiac MR (CMR) is nondiagnostic, impractical or contraindicated, photon-counting computed tomography (PCCT) provides an assessment of ventricular geometry, function and myocardial fibrosis/PCCT-derived extracellular volume (ECV), that is comparable to CMR, while enabling angiography, in patients with left ventricular hypertrophy (LVH), according to results from the MYO-AMY cohort study published April 2 in JACC: Cardiovascular Imaging.

Between July 2024 and December 2025, this prospective study included 182 consecutive adults with LVH: 72 patients with hypertrophic cardiomyopathy (HCM), 47 with transthyretin amyloid cardiomyopathy (ATTR-CM) and 63 with secondary LVH.

All patients underwent PCCT including late iodine enhancement (LIE) images and quantification of ECV. Of note, 83 patients (46%) also underwent CMR within 12 months (median interval, −12 days). Agreement was evaluated for morphofunctional parameters, ECV measurements and LIE compared with late gadolinium enhancement (LGE).

Study results showed that PCCT differentiated etiologies through distinctive tissue patterns. Patients with ATTR-CM were found to have the highest LV mass index (median, 104 g/m2), the most extensive LIE (median, 17/17 segments) and the highest level of ECV (median, 47%). HCM was characterized as showing patchy fibrosis (median 4 enhanced segments) with an intermediate level of ECV (31%), while secondary LVH was characterized by little to no enhancement (median, 0 segments) and the lowest level of ECV at 28%.

In patients who also underwent CMR, PCCT showed strong correlations with CMR for LVEF and for ECV (p<0.001 for all). There was strong agreement between the extent of LIE and LGE (r=0.998; p<0.001), and segment-wise agreement was 99-100%. Additionally, researchers observed excellent accuracy for PCCT detecting CMR-LGE (area under the curve, 0.994; sensitivity 99%; specificity 100%), as well as excellent inter-reader agreement for global PCCT-derived ECV.

“PCCT may offer incremental advantages because it directly counts and energy-discriminates photons and can apply low-energy thresholds that suppress electronic noise,” write study authors Carmelo De Gori, MD, et al. “Our larger prospectively enrolled series confirms [previous study results’] high diagnostic accuracy but shows that performance depends on the pattern and distribution of fibrosis.”