carbon-11-acetate and Myocardial-Infarction

The recovery of function in myocardium defined as viable by (18)F-FDG PET may differ from that defined by dobutamine stress echocardiography (DSE). The aim of this study was to investigate the difference in the oxidative metabolic response between myocardial segments with preserved contractile reserve (CR) and those without CR, in segments with and without preserved glucose metabolism (GM), using (11)C-acetate PET.. Twenty patients with previous myocardial infarction (left ventricular ejection fraction, 37.1% +/- 16.5%) underwent dynamic (11)C-acetate PET at rest and during dobutamine (7.5 microg/kg/min) infusion. GM was evaluated using (18)F-FDG PET and CR was evaluated using DSE. Dysfunctional segments were divided into 3 groups: group A (n = 26) with preserved CR and GM, group B (n = 15) without CR but with preserved GM, and group C (n = 41) without CR and without preserved GM.. Resting oxidative metabolism (k mono = monoexponential clearance rate) was preserved in group A and group B (0.052 +/- 0.011/min vs. 0.051 +/- 0.012/min, P = not significant) but was reduced in group C (0.040 +/- 0.015/min) (P < 0.03 vs. group A and group B). The change in k mono, as a measure of the metabolic response to low-dose dobutamine, was significantly higher in group A (0.018 +/- 0.012) than that in group B (0.0075 +/- 0.0096, P < 0.03) and group C (0.0080 +/- 0.012, P < 0.005).. Viable segments based on (18)F-FDG PET have preserved resting oxidative metabolism. However, segments without CR but with preserved GM show a reduction in the oxidative metabolic response to low-dose dobutamine infusion. The decrease in CR may be related to the reduction in the metabolic response to inotropic stimulation despite preservation of tissue viability on (18)F-FDG PET.

Topics: Acetates; Carbon; Female; Glucose; Heart; Humans; Male; Metabolic Clearance Rate; Middle Aged; Myocardial Infarction; Myocardial Stunning; Myocardium; Oxygen; Radionuclide Imaging; Radiopharmaceuticals

The purpose of this study was to validate the calculation of myocardial oxidative metabolism rate using a parametric clearance rate constant (k(mono)) image.. Fifteen subjects (seven volunteers, eight patients) were studied. Dynamic PET was acquired after intravenous injection of 700 MBq of [(11)C]acetate. The clearance rate constant of [(11)C]acetate (k(mono)) was calculated pixel by pixel to generate the parametric k(mono) image. The k(mono) values from this image and those calculated from the dynamic image were compared in the same regions of interest (ROIs).. Two different methods showed an excellent correlation except in the very low range. Regression equations were y=0.99x+0.0034 (r(2)=0.86, P<.001) and y=1.16x-0.0077 (r(2)=0.87, P<.001) in normal volunteer and patient groups, respectively, and y=1.07x-0.0019 (r(2)=0.87, P<.001) when combined.. Both methods exhibited similar values of k(mono). Parametric k(mono) image may result in better visual understanding of regional myocardial oxidative metabolism.

Topics: Acetates; Adult; Aged; Carbon; Female; Heart; Humans; Image Interpretation, Computer-Assisted; Male; Metabolic Clearance Rate; Middle Aged; Myocardial Infarction; Myocardium; Oxygen; Oxygen Consumption; Radionuclide Imaging; Radiopharmaceuticals; Reproducibility of Results; Sensitivity and Specificity