Abstract Body (Do not enter title and authors here): Introduction Patients with reperfusion injury following myocardial infarction (MI) are at a higher risk of heart failure. Reactive oxygen species (ROS) activity can further damage cardiomyocytes and compromise heart function. Imaging methods are needed to assess ROS in vivo to investigate targeted adjunctive therapies. Our group developed a novel ROS-activated PET radiotracer [18F]ROStrace to fill this gap. In this study, we measured [18F]ROStrace fractional uptake rate (FUR) and for the first time compared it with histologic assessment of infarct and myocardium specimens. We hypothesized that [18F]ROStrace FUR was increased in the infarct and that [18F]ROStrace FUR was supported by [18F]ROStrace analogue dihydroethidium (DHE) staining.
Methods MI was induced in five swine, followed by reperfusion after 90 minutes. In vivo LGE CMR imaging and [18F]ROStrace and [82]Rb PET were performed at ~3-4 days after infarction. A terminal procedure was then performed. DHE and 4′,6-diamidino-2-phenylindole (DAPI) staining was done. Two swine received injections of DHE in the right and left coronary arteries to assess ROS. ROS activity was determined from [18F]ROStrace by computing the [82]Rb myocardial blood flow (MBF) corrected FUR. The linear relationship between infarct and MVO size, and MBF-corrected [18F]ROStrace FUR were calculated using the Pearson’s r.
Results There was a strong and positive correlation between infarct and MVO size (r=0.9, p=0.04). The MBF-corrected ROStrace FUR at baseline was 0.07±0.06 ml/g, infarct was 0.15 ± 0.05 ml/g, and remote was 0.09 ± 0.05 ml/g. We observed a significant difference between ROS in the infarct and remote region (p=0.01), which is also seen in the increased DHE staining in the infarct. We also observed increased DAPI staining in the infarct region compared to free wall due to the presence of inflammatory cells, thus increasing the number of nuclei.
Conclusion [18F]ROStrace is increased in the infarct during the subacute period post-MI compared to healthy and remote myocardium and supported by histological assessment. This work may lead to the use of in vivo [18F]ROStrace PET to support development of therapeutic strategies targeting ROS to reduce MI.