CT pericoronary adipose tissue density predicts adverse clinical outcomes after cardiac transplantation

Abstract Background Coronary allograft vasculopathy (CAV) is a common cause of heart transplant failure. Coronary Computed Tomography Angiography (CCTA) is used to assess for luminal stenoses in patients with suspected CAV, but additional non-invasive markers are needed to detect early disease and guide the use of treatments that can prevent or slow CAV progression. Purpose We tested the hypotheses that: 1) coronary artery inflammation assessed by pericoronary adipose tissue (PCAT) density and/or total vessel volume-to-myocardial mass ratio (V/M) measured by CCTA could improve the ability to detect CAV in heart transplant patients; and 2) these semi-automated quantitative CCTA metrics would be associated with adverse clinical outcomes. Methods In this retrospective observational cohort study, PCAT density, V/M, and lesion composition were measured in consecutive CCTAs from patients who underwent heart transplantation at a single site between 2010 to 2021. These parameters were incorporated into predictive models for CAV as defined by International Society for Heart & Lung Transplant criteria, and evaluated against long-term clinical outcomes. Results A total of 126 CCTAs were analysed from 94 patients after heart transplant (mean age 49 [SD 14.5] years, 40% female) without CAV (n=86) and with CAV (n=40). PCAT density was higher in transplant patients with CAV (-73.0 HU [SD 9.26]) than without CAV (-77.9 HU [SD 8.23]), and age and sex-matched controls (n=12; -86.19 HU, [SD 5.38]), p<0.001 for both. Unlike patients with atherosclerotic coronary artery disease (n=32), CAV lesions were predominately non-calcified, comprised of mostly fibrous or fibrofatty tissue. V/M was lower in patients with CAV than without (32.4 mm3/g vs. 44.4 mm3/g, p<0.001). PCAT density and V/M improved the ability to predict CAV from AUC 0.78 to 0.87 on receiver operating characteristic analysis (Figure A) when added to donor age and donor/recipient hypertension status (p<0.0001). PCAT density above -66 HU was associated with a greater incidence of all-cause mortality (OR 16.6 95%CI 2.88-109.98, p<0.01; Figure B, box-plot) and the composite endpoint of death, CAV progression, acute rejection, and coronary revascularisation (OR 6.3 95%CI 1.6-32.9, p=0.01) over 5.25 (SD 2.1) years. Conclusions Heart transplant patients with CAV have higher PCAT density and lower V/M than those without. Patients with very high PCAT density on CT had markedly increased incidence of all-cause mortality and major adverse clinical events. These semi-automated metrics could be a useful addition to standard clinical CCTA reporting for diagnosis and monitoring of CAV.Diagnostic Benefit of CTCA MetricsPCAT is predictor of Future Mortality