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FIGURE 5. (A) Reconstructed midventricular functional PET images after LAD occlusion at 3 and 24 h (protocol II). Top 3 images were obtained after first *Cu-ATSM injection, 3 h after coronary occlusion, and bottom 3 were obtained after second injection, 24 h later. Horizontal long-axis view is shown, with septum on left, apex on top, and lateral free wall on right. Uptake of tracer is reduced in apical region at both 3 h and 24 h after LAD occlusion, indicating sustained hypoperfusion (perfusion image counts per pixel per minute). In contrast, retention of *Cu-ATSM (counts per pixel per minute) in apex is higher at 3 h after occlusion than at 24 h. This increase in retention at 3 h can clearly be seen after tracer retention is normalized to tracer uptake (*Cu-ATSM retention/perfusion [no units]), indicating hypoxic but viable tissue. No increase in retention is observed 24 h after normalization. Absence of *Cu-ATSM retention in this region 24 h after occlusion is consistent with necrosis, as was confirmed through postmortem TTC staining of heart. (B) Reconstructed midventricular short-axis functional PET images (counts per pixel per minute) show myocardial tracer activity after bolus injection of *Cu-ATSM (protocol III). Under resting conditions, tracer activity in anterior region is diminished, consistent with hypoperfused but normoxic myocardium. In contrast, during DOB, anterior myocardium shows increased tracer activity despite diminished perfusion to this region, suggesting hypoxia.
