Translation of Methdology used in Human Myocardial Imaging to a Sheep Model of Acute Myocardial Infarction

Background: Pre-clinical investigation of stem cells for repairing damaged myocardium predominantly used rodents, however large animals have cardiac circulation closely resembling the human heart. The aim of this study was to evaluate whether SPECT/CT myocardial perfusion imaging (MPI) could be used for assessing sheep myocardium following an acute myocardial infarction (MI) and response to intervention. Method: 18 sheep enrolled in a pilot study to evaluate [99mTc]-sestamibi MPI at baseline, post-MI and after therapy. Modifications to the standard MPI protocols were developed. All data was reconstructed with OSEM using CT-derived attenuation and scatter correction. Standard analyses were performed and inter-observer agreement were measured using Kappa (). Power determined the sample sizes needed to show statistically significant changes due to intervention. Results: Ten sheep completed the full protocol. Data processed were performed using pre-existing hardware and software used in human MPI scanning. No improvement in perfusion was seen in the control group, however improvements of 15% - 35% were seen after intra-myocardial stem cell administration. Inter-observer agreement was excellent (К=0.89). Using a target power of 0.9, 28 sheep were required to detect a 10-12% change in perfusion. Conclusions: Study demonstrates the suitability of large animal models for imaging with standard MPI protocols and it’s feasibility with a manageable number of animals. These protocols could be translated into humans to study the efficacy of stem cell therapy in heart regeneration and repair.

Keywords:

myocardial perfusion imaging , SPECT/CT , ovine model , Mesenchymal stem cells