title: Utility of myocardial perfusion imaging in patients with low-risk treadmill scores.
abstract: OBJECTIVE
  The purpose of this study was to determine whether a previously validated clinical score (CS) could identify patients with a low-risk Duke treadmill score who had a higher risk of adverse events and, therefore, in whom myocardial perfusion imaging would be valuable for risk stratification.
  
  
  BACKGROUND
  Current American College of Cardiology/American Heart Association guidelines recommend using a standard exercise test without imaging as the initial test in patients who have an interpretable electrocardiogram and are able to exercise.
  
  
  METHODS
  We studied 1,461 symptomatic patients with low-risk Duke treadmill scores (> or =5) who underwent myocardial perfusion imaging. The CS was derived by assigning one point to each of the following variables: typical angina, history of myocardial infarction, diabetes, insulin use, male gender, and each decade of age over 40 years. A CS cutoff > or =5 or <5 was used to categorize patients as high risk (n = 303 [21%]) or low risk (n = 1,158 [79%]). Perfusion scans were categorized as low, intermediate, or high risk on the basis of the global stress score (GSS).
  
  
  RESULTS
  High-risk scans were more common in patients with a high-risk CS (26.4% vs. 9.5%, p < 0.0001). The CS and GSS were significant independent predictors of cardiac death. However, in patients with a low CS, seven-year cardiac survival was excellent, regardless of the GSS (99% for normal scans, 99% for mildly abnormal scans, and 99% for severely abnormal scans). In contrast, patients with a high CS had a lower seven-year survival rate (92%), which varied with GSS (94% for normal scans, 94% for mildly abnormal scans, and 84% for severely abnormal scans; p < 0.001).
  
  
  CONCLUSIONS
  In symptomatic patients with low-risk Duke treadmill scores and low clinical risk, myocardial perfusion imaging is of limited prognostic value. In patients with low-risk Duke treadmill scores and high clinical risk, annual cardiac mortality (>1%) is not low, and myocardial perfusion imaging has independent prognostic value.
authors.affiliation: Division of Cardiovascular Diseases and Department of Internal Medicine, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, USA
authors.forename: Indu G
authors.initials: IG
authors.lastname: Poornima
authors.forename: Todd D
authors.initials: TD
authors.lastname: Miller
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Christian
authors.forename: David O
authors.initials: DO
authors.lastname: Hodge
authors.forename: Kent R
authors.initials: KR
authors.lastname: Bailey
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Gibbons
mesh_terms: D000368:Aged; D002637:Chest Pain / Q000209:etiology; D003324:Coronary Artery Disease / Q000150:complications / Q000000981:diagnostic imaging*; D004417:Dyspnea / Q000209:etiology; D005080:Exercise Test; D005260:Female; D006334:Heart Function Tests / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D019275:Radiopharmaceuticals; D018570:Risk Assessment; D013794:Thallium Radioisotopes; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D019275:Radiopharmaceuticals; D013794:Thallium Radioisotopes