German researchers have demonstrated the value of PET and SPECT imaging for monitoring the ability of circulating progenitor cells injected in the coronary arteries to preserve the integrity of myocardial tissue following recanalization.
Twenty-six patients with occlusive coronary artery disease took part in the randomized placebo-controlled double-blinded study. FDG-PET and technetium-99m tetrofosmine-SPECT were performed about eight days after coronary interventions to image relative changes in myocardial perfusion and glucose metabolism. Segments were classified as normal, perfusion-metabolism mismatch, or scar.
After another two days, patients were randomly selected to receive either repeated intracoronary infusions of progenitor cells (69±14x106 CPC) in the recanalized vessel or the same procedure with placebo serum. Cells had previously been harvested from the patients' venous blood and cultured ex vivo in an endothelial-specific medium.
FDG-PET and SPECT imaging repeated three months later found a significant decline in the number of segments of myocardial perfusion-metabolism mismatch among patients who received the progenitor cell infusion compared with controls.
In the CPC group, 48.5% of the segments diplaying a perfusion-metabolism mismatch on baseline scans were normal on follow-up studies. About 9% turned into scar, and 42.4% remained a mismatch. Among patients receiving a placebo, 12.5% of the segments normalized, 20.8% evolved into scar, and 66.7% retained a perfusion-metabolism mismatch.
The study was published in the April issue of the Journal of Nuclear Medicine (2008;49:557-563)
PET and SPECT were uniquely capable of measuring the physiological response to the progenitor cell infusion, said first author Dr. Kai Kendziorra, a nuclear medicine specialist at the University of Leipzig.
"The results shown by these imaging modalities provide the evidence needed to expand the use of CPC treatment." he said in a release from the Society of Nuclear Medicine.
Earlier research had shown that when a patient's progenitor cells are activated by growth factors, the result is increased cell division, which is vital to the tissue repair process. In this study, progenitor cells developed from circulating blood were also found to be capable of repairing hibernating myocardium.
Kendziorra noted that PET and SPECT may also play a role before coronary interventions to help select patients who would benefit from CPC administration.
"Early detection of hibernating myocardial tissue via noninvasive imaging modalities such as PET and SPECT will help us to assess a patient's myocardial metabolism and blood flow," he said. "Subsequent early coronary recanalization and CPC administration may lead to treatment-specific normalization and reduce the risk of cardiac events over longer periods."
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