Clinical significance of reduced regional myocardial glucose uptake in regions with normal blood flow in patients with chronic coronary artery disease

OBJECTIVES. The objective of this study was to assess the clinical significance of reduced regional fluorine-18 (18F) fluorodeoxyglucose uptake with normal flow in patients with chronic coronary artery disease. BACKGROUND. In patients with ischemic left ventricular dysfunction, 18F-fluorodeoxyglucose uptake may be reduced in some myocardial regions despite normal flow. The significance of this finding is unclear and has not been investigated systematically. METHODS. Twenty-three patients with coronary artery disease and impaired ventricular function (mean ejection fraction [+/- 1 SD] 28 +/- 10%) underwent positron emission tomography with 18F-fluorodeoxyglucose and oxygen-15-labeled water at rest, exercise thallium-201 tomographic imaging with rest reinjection and gated magnetic resonance imaging to measure end-diastolic wall thickness and systolic wall thickening. RESULTS. Of 168 regions with normal flow (> or = 0.7 ml/g per min), 125 (74%) had normal 18F-fluorodeoxyglucose uptake (98 +/- 10%), and the remaining 43 (26%) showed moderately reduced 18F-fluorodeoxyglucose uptake (69 +/- 8%). Systolic wall thickening was absent at rest in 14% of regions with normal 18F-fluorodeoxyglucose uptake compared with 32% of regions with reduced 18F-fluorodeoxyglucose uptake (p < 0.01). Reversible thallium abnormalities were observed in 45 (36%) of 125 regions with normal 18F-fluorodeoxyglucose uptake compared with 27 (63%) of 43 regions with reduced 18F-fluorodeoxyglucose uptake (p < 0.01). This difference was accounted for by a higher proportion of partially reversible defects in regions with reduced 18F-fluorodeoxyglucose uptake compared with regions with normal 18F-fluorodeoxyglucose uptake (42% vs. 18%, respectively, p < 0.01). CONCLUSIONS. Thus, regions with moderately reduced 18F-fluorodeoxyglucose uptake with normal flow occur commonly in patients with ischemic left ventricular dysfunction. The majority of these regions show impaired systolic function at rest and exercise-induced thallium abnormalities that are only partially reversible. These observations suggest that such regions represent an admixture of fibrotic and reversibly ischemic myocardium.