P4734Electron microscopy reveals evidence of perinuclear clustering of mitochondria in cardiac biopsy proven allograft rejection

Background Despite improved efficacy of immunosuppression therapy, allograft rejection continues to be a significant risk, especially early after transplantation. Endomyocardial biopsy (EMB) is the standard tool with a recognized role in the surveillance of posttransplant cardiac rejection and is based on optical microscopy analysis. However, this method presents technical limitations. Purpose In this work we focus on the analysis of new ultrastructural findings in cardiac biopsy specimens. Methods This study include heart transplanted patients from a single center who were referred for EMB as a scheduled routine screening. Participants were divided into 2 groups: patients transplanted without allograft rejection (n=5), and patients with biopsy-proven allograft rejection (n=5). Rejection episodes were assessed according to the International Society for Heart and Lung Transplantation (ISHLT) consensus report. Results We detected by electronic microscopy a significative increase in the number of mitochondria (p<0.0001) and dense bodies in the rejection group (p<0.05). But the most significative finding was the presence of local accumulations of mitochondria close to the nuclear envelope, pressing and shaping the morphology of this membrane in all rejection samples. We found these perinuclear clustering of mitochondria in a 68±27% of the total cardiac nucleus observed from rejection samples. We not observed this phenomenon in non-rejection samples, thus reflecting an excellent sensitivity and specificity. Perinuclear clustering of mitochondria Conclusion We observed by electron microscopy a specific phenomenon, perinuclear clustering of mitochondria, in endomyocardial biopsies from patients with cardiac rejection that affects to the architecture of the nuclear membrane. This ultrastructural approach might complement and improve the diagnosis of rejection. Acknowledgement/Funding National Institute of Health [PI16/01627, PI17/01925, PI17/01232], “Consorcio Centro de Investigaciόn Biomédica en Red, M.P.”, and FEDER

Temporal changes in left ventricular strain with the development of rejection in paediatric heart transplant recipients

Introduction:Myocardial strain measurements are increasingly used to detect complications following heart transplantation. However, the temporal association of these changes with allograft rejection is not well defined. The aim of this study was to describe the evolution of strain measurements prior to the diagnosis of rejection in paediatric heart transplant recipients.Methods:All paediatric heart transplant recipients (2004–2015) with at least one episode of acute rejection were identified. Longitudinal and circumferential strain measurements were assessed at the time of rejection and retrospectively on all echocardiograms until the most recent negative biopsy. Smoothing technique (LOESS) was used to visualise the changes of each variable over time and estimate the time preceding rejection at which alterations are first detectable.Results:A total of 58 rejection episodes were included from 37 unique patients. In the presence of rejection, there were decrements from baseline in global longitudinal strain (−18.2 versus −14.1), global circumferential strain (−24.1 versus −19.6), longitudinal strain rate (−1 versus −0.8), circumferential strain rate (−1.3 versus −1.1), peak longitudinal early diastolic strain rate (1.3 versus 1), and peak circumferential early diastolic strain rate (1.5 versus 1.3) (p<0.01 for all). The earliest detectable changes occurred 45 days prior to rejection with simultaneous alterations in myocardial strain and ejection fraction.Conclusions:Changes in graft function can be detected non-invasively prior to the diagnosis of rejection. However, changes in strain occur concurrently with a decline in ejection fraction. Strain measurements aid in the non-invasive detection of rejection, but may not facilitate earlier diagnosis compared to more traditional measures of ventricular function.