Positron emission tomography detects tissue metabolic activity in myocardial segments with persistent thallium perfusion defects

Abstract

Positron emission tomography with 13N-ammonia and 18F-2-deoxyglucose was used to assess myocardial perfusion and glucose utilization in 51 myocardial segments with a stress thallium defect in 12 patients. Myocardial infarction was defined by a concordant reduction in segmental perfusion and glucose utilization, and myocardial ischemia was identified by preservation of glucose utilization in segments with rest hypoperfusion. Of the 51 segments studied, 36 had a fixed thallium defect, 11 had a partially reversible defect and 4 had a completely reversible defect. Only 15 (42%) of the 36 segments with a fixed defect and 4 (36%) of the 11 segments with a partially reversible defect exhibited myocardial infarction on study with positron tomography. In contrast, residual myocardial glucose utilization was identified in the majority of segments with a fixed (58%) or a partially reversible (64%) thallium defect. All of the segments with a completely reversible defect appeared normal on positron tomography. Apparent improvement in the thallium defect on delayed images did not distinguish segments with ischemia from infarction. Thus, positron emission tomography reveals evidence of persistent tissue metabolism in the majority of segments with a fixed or partially resolving stress thallium defect, implying that markers of perfusion alone may underestimate the extent of viable tissue in hypoperfused myocardial segments.

Myocardial Glucose Metabolism Assessed by Positron Emission Tomography and the Histopathologic Findings of Microvessels in Syndrome X

“…[5][6][7][23][24][25] PET is a non-invasive tool for evaluating myocardial metabolism, as well as myocardial perfusion, in vivo. 19,20 In the present study, focal or diffuse fasting FDG uptake, which strongly suggested anaerobic metabolism, was observed in all 24 patients and to our knowledge, this is the first clinical report demonstrating that the fasting FDG uptake by the myocardium is significantly increased in syndrome X. The lower ejection fraction of the left ventricle in patients with diffuse FDG uptake relative to that in patients with focal uptake suggests causal consequences between alteration of the myocardial metabolism and ventricular function.…”

“…More recently, the development of positron emission tomography (PET) has resulted in better evaluation of the coronary microcirculation and metabolic condition of the myocardium. [19][20][21][22] Based on these facts, the present study was designed to assess myocardial metabolism by PET using F-18 fluorodeoxyglucose (FDG), and to characterize the small vessels histopathologically in an endomyocardial biopsy in order to investigate the pathophysiology of syndrome X.…”

Metabolic responses of hibernating and infarcted myocardium to revascularization. A follow-up study of regional perfusion, function, and metabolism.

“…[1][2][3][4] By the conventional resting glucose-loaded methodology, FDG uptake in normal myocardium is enhanced, so the tracer is seen in all viable tissue, and the glucose avidity of postischemic myocardium may be hidden. In contrast, with fasting protocols, increased FDG uptake is associated with postischemic or hibernating myocardium, whereas normal tissue is characterized by very low FDG uptake.9"10 Thus, use of the fasting methodology in this study permitted analysis of the level of FDG activity within areas where perfusion had been restored after revascularization.…”

Regional left ventricular wall thickening. Relation to regional uptake of 18fluorodeoxyglucose and 201Tl in patients with chronic coronary artery disease and left ventricular dysfunction.

“…As an alternative to`01T1 scintigraphy, metabolic imaging using positron emission tomography (PET) also may be used for the detection of viable myocardium. 3,[15][16][17][18][19] In particular, the identification of viable myocardium from PET studies is based on the presence of either normal '8fluorodeoxyglucose (FDG) uptake or FDG: blood flow mismatch,15 whereas the identification of viable myocardium from`01T1 scintigraphy is based on the presence of either normal`'TI uptake or reversiblè "Tl defects (after either redistribution or reinjection). "1 The accuracy of these criteria to predict an improvement in regional function after revascularization has been evaluated, for both PET and`'Tl scintigraphy with rest-reinjection, in a relatively small number of patients.3,1'"'2 '19 The results of these studies indicate that the current PET and 2"T1 criteria used to identify viable myocardium are quite accurate but not perfect, as they may underestimate viability in up to 22% of the myocardial segments classified as nonviable.…”