Differential F-18-2-deoxyglucose uptake in viable dysfunctional myocardiumwith normal resting perfusion - Evidence for chronic stunning in pigs

Background-Viable, chronically dysfunctional myocardium can have normal or reduced resting flow. We previously produced hibernating myocardium with re duced resting flow in pigs with a chronic stenosis and hypothesized that hi bernation is preceded by chronic stunning with normal resting perfusion. Methods and Results-Pigs instrumented with a proximal left anterior descend ing coronary artery (LAD) stenosis were studied 1 or 2 months later in the closed-chest anesthetized state. Stenosis severity increased from 74+/-5% a t 1 month to 83+/-6% at 2 months and was accompanied by anteroapical hypoki nesis (wall motion score, 2.1+/-0.1 at 1 month and 1.5+/-0.3 at 2 months; n ormal=3). Resting perfusion was similar in normal and dysfunctional regions , but the deposition of F-18-2-deoxyglucose (FDG) varied. At 1 month, suben docardial FDG deposition by excised tissue counting was similar in each reg ion (0.034+/-0.006 mL . g(-1) . min(-1) LAD region versus 0.032+/-0.004 mL . g(-1) . min(-1) in normal regions, P=NS). At 2 months, subendocardial FDG deposition was increased (0.084+/-0.025 mL . g(-1) min(-1) LAD region vers us 0.042+/-0.017 mL . g(-1) . min(-1) in normal regions, P<0.05). Increases in FDG uptake were inversely related to LAD subendocardial flow reserve du ring adenosine (3.5+/-0.6 at 1 month versus 1.4+/-0.2 at 2 months, P<0.01). Conclusions-These data indicate a progression of physiological adaptations in pigs with viable, chronically dysfunctional myocardium. As coronary flow reserve decreases, fasting FDG uptake increases. Flow at rest remains norm al, consistent with "chronic stunning," and contrasts with reduced flow and increased FDG characteristic of hibernating myocardium in similarly instru mented pigs after 3 months. This temporal progression of adaptations suppor ts the hypothesis of a transition from a physiological phenotype of stunnin g to hibernation.