title: Prognostic value of PET myocardial perfusion imaging in obese patients.
abstract: OBJECTIVE
  This study sought to determine and compare the prognostic and incremental value of positron emission tomography (PET) in normal, overweight, and obese patients.
  
  
  BACKGROUND
  Cardiac rubidium 82 (Rb-82) PET is increasingly being used for myocardial perfusion imaging (MPI). A strength of PET is its accurate attenuation correction, thereby potentially improving its diagnostic accuracy in obese patients. The prognostic value of PET in obese patients has not been well studied.
  
  
  METHODS
  A total of 7,061 patients who had undergone Rb-82 PET MPI were entered into a multicenter observational registry. All patients underwent pharmacologic Rb-82 PET and were followed for cardiac death and all-cause mortality. Based on body mass index (BMI), patients were categorized as normal (<25 kg/m(2)), overweight (25 to 29.9 kg/m(2)), or obese (≥30 kg/m(2)). Using a 17-segment model and 5-point scoring system, the percentage of abnormal myocardium was calculated for stress and rest patients categorized as normal (0%), mild (0.1% to 9.9%), moderate (10% to 19.9%), and severe (≥20%).
  
  
  RESULTS
  A total of 6,037 patients were followed for cardiac death (median: 2.2 years) and the mean BMI was 30.5 ± 7.4 kg/m(2). A total of 169 cardiac deaths were observed. PET MPI demonstrated independent and incremental prognostic value over BMI. Normal PET MPI conferred an excellent prognosis with very low annual cardiac death rates in normal (0.38%), overweight (0.43%), and obese (0.15%) patients. As well, both moderately and severe obese patients with a normal PET MPI had excellent prognosis (0.20% and 0.10%, respectively). The net reclassification improvement of PET was 0.46 (95% confidence interval [CI]: 0.31 to 0.61), and appeared similar in the moderately and severe obese patients which were 0.44 (95% CI: 0.12 to 0.76) and 0.63 (95% CI: 0.27 to 0.98), respectively.
  
  
  CONCLUSIONS
  Rb-82 PET has incremental prognostic value in all patients irrespective of BMI. In the obese population, where other modalities may have reduced diagnostic accuracy, cardiac PET appears to be a promising noninvasive modality with prognostic value.
authors.affiliation: Department of Medicine (Cardiology), University of Ottawa Heart Institute, Ottawa, Ontario, Canada; Department of Radiology, University of Ottawa, Ottawa, Ontario, Canada. Electronic address: bchow@ottawaheart.ca.
authors.forename: Benjamin J W
authors.initials: BJ
authors.lastname: Chow
authors.affiliation: Division of Cardiovascular Medicine and Division of Nuclear Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Sharmila
authors.initials: S
authors.lastname: Dorbala
authors.affiliation: Division of Cardiovascular Medicine and Division of Nuclear Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Marcelo F
authors.initials: MF
authors.lastname: Di Carli
authors.affiliation: Departments of Cardiology, Internal Medicine, and Nuclear Medicine, Niagara Falls Memorial Medical Center, Buffalo, New York.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Merhige
authors.affiliation: Department of Center for Health Research, Geisinger Medical Center, Danville, Pennsylvania.
authors.forename: Brent A
authors.initials: BA
authors.lastname: Williams
authors.affiliation: Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Emir
authors.initials: E
authors.lastname: Veledar
authors.affiliation: Department of Radiology and Department of Imaging, Weill Cornell Medical College, New York, New York.
authors.forename: James K
authors.initials: JK
authors.lastname: Min
authors.affiliation: Department of Biostatistics, Boston University Biostatistics and Harvard Clinical Research Institute, Boston, Massachusetts.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Pencina
authors.affiliation: Department of Medicine (Cardiology), University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
authors.forename: Yeung
authors.initials: Y
authors.lastname: Yam
authors.affiliation: Department of Medicine (Cardiology), University of Ottawa Heart Institute, Ottawa, Ontario, Canada; Cardiovascular Research Methods Centre, University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Medicine (Cardiology), University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
authors.forename: Sai Priya
authors.initials: SP
authors.lastname: Anand
authors.affiliation: Department of Medicine (Cardiology), University of Ottawa Heart Institute, Ottawa, Ontario, Canada; Department of Radiology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Terrence D
authors.initials: TD
authors.lastname: Ruddy
authors.affiliation: Department of Imaging, Cedars-Sinai Medical Center, Los Angeles, California.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Berman
authors.affiliation: Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Leslee J
authors.initials: LJ
authors.lastname: Shaw
authors.affiliation: Department of Medicine (Cardiology), University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
authors.forename: Rob S
authors.initials: RS
authors.lastname: Beanlands
mesh_terms: D000368:Aged; D015992:Body Mass Index; D003326:Coronary Circulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000150:complications / Q000000981:diagnostic imaging* / Q000401:mortality / Q000503:physiopathology; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D009765:Obesity / Q000150:complications* / Q000175:diagnosis / Q000401:mortality; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011379:Prognosis; D012042:Registries; D012307:Risk Factors; D012414:Rubidium Radioisotopes; D012720:Severity of Illness Index; D013997:Time Factors; D014481:United States
chemical_list: D012414:Rubidium Radioisotopes
keywords: cardiac death; obesity; positron emission tomography; prognosis