title: Non-invasive cardiac stress testing before elective major non-cardiac surgery: population based cohort study.
abstract: OBJECTIVE
  To determine the association of non-invasive cardiac stress testing before elective intermediate to high risk non-cardiac surgery with survival and hospital stay.
  
  
  METHODS
  Population based retrospective cohort study.
  
  
  METHODS
  Acute care hospitals in Ontario, Canada, between 1 April 1994 and 31 March 2004.
  
  
  METHODS
  Patients aged 40 years or older who underwent specific elective intermediate to high risk non-cardiac surgical procedures.
  
  
  METHODS
  Non-invasive cardiac stress testing performed within six months before surgery.
  
  
  METHODS
  Postoperative one year survival and length of stay in hospital.
  
  
  RESULTS
  Of the 271 082 patients in the entire cohort, 23 991 (8.9%) underwent stress testing. After propensity score methods were used to reduce important differences between patients who did or did not undergo preoperative stress testing and assemble a matched cohort (n=46 120), testing was associated with improved one year survival (hazard ratio (HR) 0.92, 95% CI 0.86 to 0.99; P=0.03) and reduced mean hospital stay (difference -0.24 days, 95% CI -0.07 to -0.43; P<0.001). In an analysis of subgroups defined by Revised Cardiac Risk Index (RCRI) class, testing was associated with harm in low risk patients (RCRI 0 points: HR 1.35, 95% CI 1.05 to 1.74), but with benefit in patients who were at intermediate risk (RCRI 1-2 points: 0.92, 95% CI 0.85 to 0.99) or high risk (RCRI 3-6 points: 0.80, 95% CI 0.67 to 0.97).
  
  
  CONCLUSIONS
  Preoperative non-invasive cardiac stress testing is associated with improved one year survival and length of hospital stay in patients undergoing elective intermediate to high risk non-cardiac surgery. These benefits principally apply to patients with risk factors for perioperative cardiac complications.
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ontario M4N 3M5, Canada. d.wijeysundera@utoronto.ca
authors.forename: Duminda N
authors.initials: DN
authors.lastname: Wijeysundera
authors.forename: W Scott
authors.initials: WS
authors.lastname: Beattie
authors.forename: Peter C
authors.initials: PC
authors.lastname: Austin
authors.forename: Janet E
authors.initials: JE
authors.lastname: Hux
authors.forename: Andreas
authors.initials: A
authors.lastname: Laupacis
mesh_terms: D000328:Adult; D000368:Aged; D005080:Exercise Test / Q000379:methods* / Q000401:mortality; D005260:Female; D006331:Heart Diseases / Q000175:diagnosis* / Q000401:mortality; D006801:Humans; D007431:Intraoperative Complications / Q000401:mortality / Q000517:prevention & control*; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D009864:Ontario; D011300:Preoperative Care / Q000379:methods* / Q000401:mortality; D012189:Retrospective Studies; D013312:Stress, Physiological; D016019:Survival Analysis