Myocardial viability assessment by PET: (82)Rb defect washout does not predict the results of metabolic-perfusion mismatch.
PET is a sensitive technique for the identification of viable myocardial tissue in patients with coronary disease. Metabolic assessment with (18)F-FDG is considered the gold standard for assessment of viability before surgical revascularization. Prior research has suggested that viability may be assessed with washout of (82)Rb between early and late resting images. Our objective was to determine whether assessment of myocardial viability with (82)Rb washout is reliable when compared with PET using (18)F-FDG.


METHODS
We performed PET for 194 patients referred for PET (18)F-FDG/(82)Rb to assess viability for clinical indications. We included 151 patients with resting defects >10% of the left ventricle (LV) (n = 159 defects). Patients with smaller resting (82)Rb defects (<10% LV) were excluded for the purpose of this study. PET images acquired with (82)Rb and (18)F-FDG defined viability by the mismatch between metabolism and perfusion ((18)F-FDG >125% of (82)Rb uptake in the (82)Rb defect). Evidence of viability with (82)Rb was assessed by the presence of (i) severity: (82)Rb counts in the defect >50% of (82)Rb in the normal zone of the resting PET images; (ii) washout: decrease of (82)Rb counts in the defect from early to late resting (82)Rb images <17% between the first 90-s image and the final 300-s image; or (iii) combined severity and washout criteria, which required positive criteria for (i) and (ii) to indicate viability.


RESULTS
Prevalence of viability by (18)F-FDG/(82)Rb criteria was 50% (n = 79). Severity criteria yielded a sensitivity of 76% and a specificity of 17%, washout criteria yielded a sensitivity of 81% and a specificity of 23%, and both criteria had a sensitivity of 63% and a specificity of 32%. Positive and negative predictive values were poor for all criteria. No correlation existed between (82)Rb washout and (18)F-FDG-(82)Rb mismatch (r(2) = 0.00). Multiple receiver-operating-characteristic plots showed very poor discrimination despite varying criteria for viability by (82)Rb (severity from 50% to 60% of normal zone, washout from 12% to 17%).


CONCLUSIONS
(82)Rb washout from early to late resting images, combined with quantitative severity of the resting (82)Rb defect, did not yield results equivalent to PET (18)F-FDG-(82)Rb mismatch and may not accurately assess myocardial viability.
Stankewicz
Mark A
MA
Carlyle Fraser Heart Center, Emory Crawford Long Hospital, Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30308, USA.
Mansour
Craig S
CS
Eisner
Robert L
RL
Churchwell
Keith B
KB
Williams
Byron R
BR
Sigman
Steven R
SR
Streeter
James
J
Patterson
Randolph E
RE
D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000378:metabolism; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D017682:Myocardial Stunning / Q000150:complications / Q000000981:diagnostic imaging* / Q000378:metabolism; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012414:Rubidium Radioisotopes / Q000493:pharmacokinetics; D012680:Sensitivity and Specificity; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology / Q000378:metabolism
D019275:Radiopharmaceuticals; D012414:Rubidium Radioisotopes