Coronary calcifications and myocardial flow reserve in heart transplant patients: a longitudinal study

Cardiac allograft vasculopathy (CAV) is an immune-mediated pathology unique to heart transplant (HT) recipients characterized by diffuse concentric intimal thickening and progressive luminal narrowing of the coronary vasculature, leading to myocardial ischemia and graft dysfunction, and remains a major cause of death beyond the first post-transplant year.1 Multiple studies have demonstrated that positron emission tomography (PET) myocardial perfusion imaging (MPI) with integrated myocardial blood flow (MBF) quantification can be used to diagnose CAV noninvasively and provide prognostication in HT recipients.2 PET MPI is routinely performed with low dose computed tomography for attenuation correction (CTAC), from which coronary artery calcium (CAC) can be visually estimated, which has been linked to higher risk of subsequent death or re-transplantation.3 In this study, we analysed longitudinal trends in myocardial flow reserve (MFR) and CAC and evaluated the prognostic significance of their abnormalities in HT patients. Patients who underwent 82-Rubidium PET MPI for post-transplant monitoring at a single centre between May 2008 and March 2022 were retrospectively included. Dynamic rest-stress 82-Rubidium PET MPI was performed as previously described.4 MFR was determined as the ratio of hyperaemic (stress) MBF to resting MBF, with