title: Association of myocardial enzyme elevation and survival following coronary artery bypass graft surgery.
abstract: BACKGROUND
  Several small studies have suggested that cardiac enzyme elevation in the 24 hours following coronary artery bypass graft (CABG) surgery is associated with worse prognosis, but a definitive study is not available. Also, the long-term prognostic impact of small increases of perioperative enzyme has not been reported.
  
  
  OBJECTIVE
  To quantify the relationship between peak post-CABG elevation of biomarkers of myocardial damage and early, intermediate-, and long-term mortality, including determining whether there is a threshold below which elevations lack prognostic significance.
  
  
  METHODS
  Studies (randomized clinical trials or registries) of patients undergoing CABG surgery in which postprocedural biomarker and mortality data were collected and included. A search of the PubMed database was performed in July 2008 using the search terms coronary artery bypass, troponin, CK-MB, and mortality.
  
  
  METHODS
  Studies evaluating mortality and creatine kinase (CK-MB), troponin, or both were included. One study investigator declined to participate and 3 had insufficient data.
  
  
  METHODS
  Two independent reviewers determined study eligibility. The principal investigator from each eligible study was contacted to request his/her participation. Once institutional review board approval for the use of these data for this purpose was obtained, we requested patient-level data from each source. Data were examined to ensure that cardiac markers had been measured within 24 hours after CABG surgery, key baseline covariates, and mortality were available.
  
  
  RESULTS
  A total of 18,908 patients from 7 studies were included. Follow-up varied from 3 months to 5 years. Mortality was found to be a monotonically increasing function of the CK-MB ratio. The 30-day mortality rates by categories of CK-MB ratio were 0.63% (95% confidence interval [CI], 0.36%-1.02%) for 0 to <1, 0.86% (95% CI, 0.49%-1.40%) for 1 to <2, 0.95% (95% CI, 0.72%-1.22%) for 2 to <5, 2.09% (95% CI, 1.69%-2.57%) for 5 to <10, 2.78% (95% CI, 2.12%-3.58%) for 10 to <20, and 7.06% (95% CI, 5.46%-8.96%) for 20 to ≥40. Of the variables considered, the CK-MB ratio was the strongest independent predictor of death to 30 days and remained significant even after adjusting for a wide range of baseline risk factors (χ(2) = 143, P < .001; hazard ratio [HR] for each 5 point-increment above the upper limits of normal [ULN] = 1.12; 95% CI, 1.10-1.14). This result was strongest at 30 days, but the adjusted association persisted from 30 days to 1 year (χ(2) = 24; P < .001; HR for each 5-point increment above ULN = 1.17; 95% CI, 1.10-1.24) and a trend was present from 1 year to 5 years (χ(2) = 2.8; P = .10; HR for each 5-point increment above ULN = 1.05; 95% CI, 0.99-1.11). Similar analyses using troponin as the marker of necrosis led to the same conclusions (χ(2) = 142 for 0-30 days and χ(2) = 40 for 30 days to 6 months, both P < .001; HR for each 50 points above the ULN = 1.28; 95% CI, 1.23-1.33 and 1.15; 95% CI, 1.10-1.21, respectively).
  
  
  CONCLUSIONS
  Among patients who had undergone CABG surgery, elevation of CK-MB or troponin levels within the first 24 hours was independently associated with increased intermediate- and long-term risk of mortality.
authors.affiliation: Mount Sinai Cardiovascular Institute, New York, New York 10029, USA. michael.domanski@mssm.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Domanski
authors.forename: Kenneth
authors.initials: K
authors.lastname: Mahaffey
authors.forename: Vic
authors.initials: V
authors.lastname: Hasselblad
authors.forename: Sorin J
authors.initials: SJ
authors.lastname: Brener
authors.forename: Peter K
authors.initials: PK
authors.lastname: Smith
authors.forename: Graham
authors.initials: G
authors.lastname: Hillis
authors.forename: Milo
authors.initials: M
authors.lastname: Engoren
authors.forename: John H
authors.initials: JH
authors.lastname: Alexander
authors.forename: Jerrold H
authors.initials: JH
authors.lastname: Levy
authors.forename: Bernard R
authors.initials: BR
authors.lastname: Chaitman
authors.forename: Samuel
authors.initials: S
authors.lastname: Broderick
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mack
authors.forename: Karen S
authors.initials: KS
authors.lastname: Pieper
authors.forename: Michael E
authors.initials: ME
authors.lastname: Farkouh
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood*; D002986:Clinical Trials as Topic; D001026:Coronary Artery Bypass / Q000401:mortality*; D052279:Creatine Kinase, MB Form / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011379:Prognosis; D012042:Registries / Q000706:statistics & numerical data; D012306:Risk; D013997:Time Factors; D016896:Treatment Outcome; D014336:Troponin / Q000097:blood*
chemical_list: D015415:Biomarkers; D014336:Troponin; D052279:Creatine Kinase, MB Form