# 18F-Fluorodeoxyglucose positron emission tomography for detection of acute cellular rejection after heart transplantation: A single–center retrospective study

## TL;DR

This study explores whether 18F-FDG PET/CT can detect heart transplant rejection without invasive biopsies.

## Contribution

The study demonstrates that FDG uptake metrics can detect acute cellular rejection after heart transplantation.

## Key findings

- FDG uptake metrics (CMV, SUVmax, TLG) were significantly higher during acute cellular rejection.
- 18F-FDG PET/CT showed significant increases in metabolic parameters at the time of rejection.
- No cases of antibody-mediated rejection were observed in the study population.

## Abstract

Although histopathological evaluation of myocardium is essential for detecting both acute cellular rejection (ACR) and antibody-mediated rejection (AMR) following heart transplantation, indeterminate results and complication risks associated with repeated endomyocardial biopsies remain serious problems. We investigated the clinical utility of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) to detect rejection.

This retrospective single–center study reviewed the clinical data of heart-transplant recipients at our institution between 2008 and 2022. Patients who underwent 18F-FDG PET/CT scans post-transplant were enrolled. Scans were performed following a high-fat, low-carbohydrate diet initiated 24 hours before imaging and an 18-hour fasting period. FDG uptake was represented as cardiac metabolic volume (CMV), maximum standard uptake value (SUVmax), and total lesion glycolysis (TLG).

During the study period, 132 18F-FDG PET/CT scans in 40 heart-transplant recipients were identified. Age at transplant was 53 [43-62] years old, and 29 patients (73%) were male. We found 10 scans at the time of significant ACR. No patients experienced AMR. At the time of ACR, CMV (88.2 [22.5-275.8] vs 0.0 [0.0-7.3] ml, p < 0.001), SUVmax (9.21 [6.87-16.0] vs 2.98 [2.49-4.48], p < 0.001) and TLG (365.3 [78.3-1,908.7] vs 0.0 [0.0-25.8] g, p < 0.001) were significantly higher compared to those without rejection. From baseline to the time of ACR, significant increases of CMV, SUVmax, and TLG (p < 0.001 for all) were also found.

FDG uptake was significantly elevated at the time of ACR. 18F-FDG PET/CT may represent a promising non–invasive diagnostic adjunct for detecting ACR following heart transplantation.