Evaluation of coronary artery disease and extracellular volume in cardiac amyloidosis using photon counting CT

Abstract Background In cardiac amyloidosis (CA) protein misfolding and consecutive storage into the extracellular myocardial compartment is causing left ventricular hypertrophy and heart failure. Small vessel disease caused by CA and concomitant coronary artery disease (CAD) are also present in CA, potentially worsening heart failure. Photon counting CT (PCCT) with improved spatial resolution may be used for the imaging work up of CA, assessing the extracellular volume (ECV) and CAD. Purpose The aim of this study was to compare ECV measurements obtained from PCCT to the imaging reference cardiac magnetic resonance imaging (CMR) and to evaluate CAD in a CA cohort. Materials and Methods Thirty CA patients (mean age 77.5 +/- 7.9 years) who underwent clinically indicated coronary CT angiography (CCTA) on a first-generation PCCT were included. CCTA included a late phase CCTA for the evaluation of ECV. ECV was derived using two different techniques: (I) a single-energy (SE) and (II) a dual-energy (DE) technique. Both methods were compared with CMR-derived ECV. Statistical analysis included repeated-measures analysis of variance (RM-ANOVA) with Bonferroni-adjusted pairwise comparisons. Correlations between methods were assessed using Pearson’s correlation coefficient. Results Among the three methods, CMR exhibited the highest mean ECV value (42.93 ± 10.14), followed by the SE method (42.5 ± 9.1), while the DE method yielded the lowest ECV values (40.7 ± 9.2). Therefore, ECV values using the DE method were significantly lower (MDiff =-2.24, p =0.04). No significant difference was observed between CMR and the SE method (MDiff=0.43, p = 1.00). A significant difference was found between the DE and SE methods (MDiff =-1.82, p 0.001). Despite these differences, all methods demonstrated excellent positive correlations. The strongest correlation was observed between the DE and SE methods (r = 0.98, p 0.001), indicating high consistency in their measurements. Comparatively, the correlation between CMR and DE (r = 0.892, p 0.001) was slightly stronger than that between CMR and SE methods (r = 0.882, p 0.001). CAD was present in 29 (97.0%) CA patients with a mean Agatston score of 1086 ± 1398 (range 0 – 6848.5). Despite this high mean plaque burden and 14 (47.6%) patients presenting with atrial fibrillation (AF) at the time of CCTA, image quality was preserved in 29 (97.0%) patients with 17 (57.6%) of the patients having non-obstructive CAD. Conclusion Compared to the imaging reference standard CMR, ECV derived from the DE and SE methods via PCCT demonstrated excellent positive correlations with CMR. The DE method exhibited minor differences compared to CMR, which were clinically not relevant. CAD with an extensive burden of calcified plaque was highly prevalent in CA, however, 57.6% of patients presented with non-obstructive CAD. Therefore, PCCT is a valuable tool for imaging the myocardial structure and CAD in CA.Evaluation of ECV and CAD by PCCT