title: Threshold values for preserved viability with a noninvasive measurement of collateral blood flow during acute myocardial infarction treated by direct coronary angioplasty.
abstract: BACKGROUND
  Quantitative measures of myocardial perfusion defect severity from acute (99m)Tc-sestamibi tomographic images (nadir) have correlated closely with collateral and residual antegrade blood flow during acute myocardial infarction. The purpose of this study was to determine whether a viability threshold could be identified from this measure in patients with acute myocardial infarction treated in a homogeneous manner with successful reperfusion therapy.
  
  
  RESULTS
  The study group consisted of 61 patients with acute myocardial infarction with a risk area of >6% LV treated with primary angioplasty between 120 and 240 minutes after symptom onset. All patients were injected with 20 to 30 mCi of (99m)Tc-sestamibi before primary angioplasty and imaged after the procedure. Acute myocardium at risk (MAR) and subsequent infarct size (IS) were quantified by a threshold program. Severity (nadir) from the acute image was the lowest ratio of minimal/maximum counts from 5 short-axis slices. Infarct location was anterior in 22 and inferior in 39 patients. MAR was 33+/-15% LV and IS was 13+/-15% LV: 23 patients had no infarction despite MAR similar to those with infarction. Receiver-operator characteristic curve analysis identified a nadir value of 0.26 as providing the best separation of patients with and without infarction (sensitivity, 74%; specificity, 74%). This nadir threshold varied by infarct location: anterior defect, 0.21; inferior defect, 0.31. The sensitivity and specificity for absent infarction for these values were anterior, 69% and 67%, and inferior, 88% and 84%, respectively.
  
  
  CONCLUSIONS
  In a time frame in which the presence of residual blood flow is important, the severity of the acute (99m)Tc-sestamibi defect can be used to predict whether infarction will develop despite successful reperfusion.
authors.affiliation: Mayo Clinic and Mayo Foundation, Rochester, MN 55905, USA. christian.timothy@mayo.edu
authors.forename: T F
authors.initials: TF
authors.lastname: Christian
authors.forename: P B
authors.initials: PB
authors.lastname: Berger
authors.forename: M K
authors.initials: MK
authors.lastname: O'Connor
authors.forename: D O
authors.initials: DO
authors.lastname: Hodge
authors.forename: R J
authors.initials: RJ
authors.lastname: Gibbons
mesh_terms: D000368:Aged; D015906:Angioplasty, Balloon, Coronary / Q000379:methods*; D003097:Collateral Circulation; D003326:Coronary Circulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging* / Q000628:therapy*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011877:Radionuclide Imaging; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi; D014057:Tomography, X-Ray Computed
chemical_list: D017256:Technetium Tc 99m Sestamibi