Comprehensive non-invasive assessment of cardiac allograft vasculopathy and myocardial involvement in heart transplant patients using cardiac computed tomography

• CT-derived extracellular volume (ECV CT ) is elevated in heart transplant recipients reflecting myocardial fibrosis with associations to rejection and cardiac allograft vasculopathy. • ECV CT shows excellent correlation with MRI-derived ECV measurements. • CT enables combined assessment of cardiac allograft vasculopathy (CAV) and myocardial fibrosis in a single exam. CT-derived extracellular volume (ECV CT ) is elevated in heart transplant recipients reflecting myocardial fibrosis with associations to rejection and cardiac allograft vasculopathy. ECV CT shows excellent correlation with MRI-derived ECV measurements. CT enables combined assessment of cardiac allograft vasculopathy (CAV) and myocardial fibrosis in a single exam. Cardiac graft rejection and allograft vasculopathy (CAV) are major causes of morbidity and mortality in heart transplant (HT) patients. While endomyocardial biopsy and invasive coronary angiography remain diagnostic gold standards, their invasiveness highlights the need for safer, noninvasive alternatives. Cardiac computed tomography (CT) has emerged as a promising modality for evaluating both coronary and myocardial status. The primary aim of this study is to evaluate CT-measured extracellular volume (ECV CT ) in HT patients compared to a control group and identify its clinical determinants. The secondary objective is to explore the association between ECV CT and CAV severity. In a reference HT center, we conducted a retrospective cohort study of 163 patients comprising 80 HT patients and 83 age- and sex-matched controls without structural heart disease studied with a standardized CT protocol. Twenty-two control patients had concomitant cardiac CT and magnetic resonance (CMR) to validate ECV CT measurements. Determinants of ECV CT including rejection history, CAD-RADS, CAV and cardiovascular risk factors were studied. Median ECV CT was significantly higher in HT patients (34%, IQR 30–38) compared to controls (29%, IQR 27–31; p < 0.001). ECV CT was highly correlated with MR-ECV (r = 0.88, p < 0.001). In HT recipients, elevated ECV CT was independently associated to hypertension, smoking, presence of CAV, elevated CAD-RADS scores and a history of graft rejection, whereas in controls only higher coronary artery calcium scores correlated with increased ECV CT. ECV CT is increased in HT patients compared to controls and associated with rejection history and CAV. ECV CT emerges as a promising noninvasive tool for the simultaneous assessment of myocardial alterations and CAV in HT patients showing strong concordance with CMR and high reproducibility. Further multicenter studies are warranted to confirm its role in transplant surveillance protocols.