title: Use of clinically based troponin underestimates the cardiac injury in non-cardiac surgery: a single-centre cohort study in 51,701 consecutive patients.
abstract: OBJECTIVE
  Postoperative myocardial infarction causes hundreds of thousands of deaths annually, and "failure to rescue" is a leading cause of hospital mortality. Strategies to recognize cardiac injury are important to reduce the burden of cardiac-related morbidity. For these reasons, we chose to assess the association between postoperative troponin I elevations and 30-day in-hospital mortality and, secondarily, to compare the predictive value of regularly scheduled troponin estimates with troponin ordered in response to clinical indications.
  
  
  METHODS
  We carried out a retrospective cohort analysis of 51,701 consecutive patients throughout 2003 to 2009. All patients were from a single university referral hospital and included all non-cardiac non-transplant surgery patients requiring overnight admission. Logistic regression was used to assess the risk-adjusted associations between troponin I and 30-day in-hospital mortality.
  
  
  RESULTS
  The multivariable predictive model for death improved after troponin I was included. The receiver operating characteristic was 0.902 before troponin I vs 0.934 after troponin I (P<0.0001). The likelihood ratio for troponin was 3.0 (95% confidence interval 2.8 to 3.2) and evident in each surgical service. Increasing troponin I showed a dose-response associated with increased mortality, and compared with clinically based measurements, a regularly scheduled postoperative troponin protocol showed a threefold increase in the probability of detecting myocardial injury. However, troponin I was not found to improve the risk prediction model in the lowest risk patients (n=18,953; probability of death<0.02%) with one cardiac death.
  
  
  CONCLUSIONS
  Postoperatively elevated troponin I is associated with 30-day in-hospital mortality in a dose-dependent manner. A postoperative measurement protocol provides a threefold increase in the ability to detect myocardial injury. Conversely, in patients with a low mortality risk, cardiac injury is low; there is minimal improvement in the ability to detect cardiac injury, and the rescue rates from cardiac injury are excellent. These findings suggest that a surveillance protocol of troponin I would be optimal when limited to moderate to high-risk patients.
authors.affiliation: Department of Anesthesia and Pain Management, University Health Network, Toronto, ON, Canada. scott.beattie@uhn.ca
authors.forename: W Scott
authors.initials: WS
authors.lastname: Beattie
authors.forename: Keyvan
authors.initials: K
authors.lastname: Karkouti
authors.forename: Gordon
authors.initials: G
authors.lastname: Tait
authors.forename: Andrew
authors.initials: A
authors.lastname: Steel
authors.forename: Paul
authors.initials: P
authors.lastname: Yip
authors.forename: Stuart
authors.initials: S
authors.lastname: McCluskey
authors.forename: Michael
authors.initials: M
authors.lastname: Farkouh
authors.forename: Duminda N
authors.initials: DN
authors.lastname: Wijeysundera
mesh_terms: D015415:Biomarkers / Q000097:blood*; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D006335:Heart Injuries / Q000175:diagnosis* / Q000209:etiology / Q000401:mortality; D006801:Humans; D007431:Intraoperative Complications / Q000175:diagnosis* / Q000401:mortality; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D059035:Perioperative Period; D011183:Postoperative Complications / Q000401:mortality; D012372:ROC Curve; D012189:Retrospective Studies; D018570:Risk Assessment; D013514:Surgical Procedures, Operative / Q000009:adverse effects* / Q000401:mortality; D019210:Troponin I / Q000097:blood*
chemical_list: D015415:Biomarkers; D019210:Troponin I