title: Risk stratification among diabetic patients undergoing stress myocardial perfusion imaging.
abstract: BACKGROUND
  Previous studies have suggested that diabetic patients undergoing single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) are at greater risk for cardiac events than non-diabetic patients with both normal and abnormal imaging results. However, the impact of stress modality on outcomes in this patient group has not been examined.
  
  
  METHODS
  The data on all patients undergoing exercise stress or vasodilator stress SPECT MPI from 1996 to 2005 were reviewed. After excluding patients based on our predefined criteria, we subcategorized the study population into diabetic patients and non-diabetic patients. Among the diabetic patients, we identified patients with known coronary artery disease (CAD) and no known CAD. All studies were interpreted using the 17-segment ASNC model. The presence, extent, and severity of perfusion defects were calculated using the summed stress score (SSS), and patients were classified into normal (SSS < 4), mildly abnormal (SSS 4-8), and moderate-severely abnormal (SSS > 8) categories. The annualized cardiac event rate including cardiac death and non-fatal myocardial infarction was calculated over a mean follow-up period of 2.4 ± 1.4 years with a maximum of 6 years.
  
  
  RESULTS
  The cardiac event rate was statistically significantly lower in diabetic patients undergoing exercise stress MPI when compared to the diabetic patients undergoing pharmacological stress MPI across all three perfusion categories (1.3% vs 3.4%, 2.3% vs 5.7%, 4.2% vs 10.7%, respectively). Diabetic patients with no known CAD, who underwent exercise stress MPI had significantly lower cardiac events across all three perfusion categories as compared to the remainder of the diabetic population. Ability to perform exercise stress test was the strongest multivariate predictor of favorable outcome, whereas ejection fraction < 50%, abnormal perfusion imaging on SPECT MPI, and increasing age stood out as independent predictors of adverse outcome in the diabetic patients. Within the abnormal perfusion category, the annualized cardiac event rate among patients undergoing exercise stress SPECT MPI was not statistically different between the diabetic and non-diabetic cohorts.
  
  
  CONCLUSIONS
  Diabetic patients undergoing exercise SPECT MPI have a significantly better prognosis than those undergoing pharmacological stress, more similar to patients without diabetes. In patients with diabetes exercise stress test MPI identifies low risk patients and provides precise risk stratification.
authors.affiliation: Division of Cardiovascular Medicine, University of Miami Miller School of Medicine, 1600 NW 10th Avenue, Miami, FL 33136, USA. abhijitghatak@yahoo.com
authors.forename: Abhijit
authors.initials: A
authors.lastname: Ghatak
authors.forename: Santosh
authors.initials: S
authors.lastname: Padala
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Katten
authors.forename: Donna M
authors.initials: DM
authors.lastname: Polk
authors.forename: Gary V
authors.initials: GV
authors.lastname: Heller
mesh_terms: D000368:Aged; D003324:Coronary Artery Disease / Q000150:complications / Q000000981:diagnostic imaging*; D048909:Diabetes Complications / Q000000981:diagnostic imaging*; D003920:Diabetes Mellitus / Q000473:pathology*; D018572:Disease-Free Survival; D005080:Exercise Test / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000000981:diagnostic imaging*; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D011379:Prognosis; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012984:Software; D017256:Technetium Tc 99m Sestamibi; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi