Regional myocardial oxygen consumption estimated by carbon-11 acetate and positron emission tomography before and after repetitive ischemia

Background. Preserved myocardial oxygen consumption estimated by carbon 11- acetate and positron emission tomography (PET) in myocardial regions with c hronic but reversibly depressed contractile function in patients with ische mic heart disease have been suggested to be caused by repeated short episod es of acute myocardial ischemia, To evaluate this hypothesis myocardial C-1 1-acetate PET imaging was performed before and after acute repetitive myoca rdial ischemia. Methods and Results, In open chest dogs (n = 8), the left anterior descendi ng coronary artery was occluded 4 times for 5 minutes alternating with 5 mi nutes of reperfusion, Before and after repetitive coronary occlusions, oxyg en 15 water/oxygen 15 carbon monoxide (blood flow), and C-11-acetate (oxyge n consumption) PET imaging were performed. Left ventricular regional systol ic wall thickening was measured with sonomicrometry. Forty-five minutes aft er the ischemic episodes, systolic ventricular wall thickening was decrease d by 90%, whereas myocardial blood flow was reduced by 21% compared with ba seline values (P < .05), Ninety minutes after the ischemic episodes, estima ted oxygen consumption was unaltered compared with the baseline level despi te a sustained 70% decrease in the regional contractile function (P < .05), Conclusions, Oxygen consumption estimated by C-11-acetate PET imaging is pr eserved after repeated episodes of acute myocardial ischemia despite a seve re impairment of contractile function.