Factors That Alter the Relationship Between Peak Postoperative CKMB and Troponin T After CABG

BACKGROUND: Peak postoperative creatine kinase MB fraction (CKMB) and Troponin T (TnT) levels have been measured after cardiac surgery to assess perioperative myocardial damage, evaluate myocardial protective strategies and predict adverse events. However, the relationship between peak levels of both enzymes has not been fully established in this setting. We compared peak levels of CKMB and TnT in patients after CABG to test the hypothesis that patient and operative characteristics influence the correlation between the values of these biomarkers. OBJECTIVE: To examine the relationship between peak levels of cTnT and CKMB following CABG in defined subsets of patients with pre-defined comorbidities to test the hypothesis that patient and operative characteristics influence the correlation between the values of these biomarkers. METHODS: Data were prospectively collected from 885 consecutive patients undergoing on-pump CABG at a single institution between July 2011 and June 2017. Peak values were selected from all serum levels of CKMB and TnT collected during the hospital stay following surgery. Clinical variables were collected based on definitions in the STS Adult Cardiac Surgery Database version 2.181. Analysis of covariance (ANCOVA) and linear regression models were used to statistically compare the slope of the linear relationship between peak postoperative CKMB and TnT for the patient cohort. Models were created to compare the slopes by pre-defined clinical variables including (1) age, (2) sex, (3) race, (4) current smoking status (5) hypertension, (6) dyslipidemia, (7) ejection fraction (EF), (8) diabetes, (9) renal dysfunction (GFR<60), (10) recent MI, preoperative use of (11) ACE-inhibitors, (12) beta-blockers, and (13) anticoagulants; and operative variables including (1) cross clamp time (< or > 70 min), (2) CPB time (< or > 100 min), and (3) intra-operative blood products transfusion. RESULTS: Overall, the correlation between peak postoperative CKMB and TnT was robust in patients undergoing CABG. However, the slope of the relationship was significantly lower in males, diabetics, patients with dyslipidemia, patients with hypertension, patients with lower EF, patients who received red blood cell transfusions, and patients receiving beta-blockers. The slope was significantly greater in patients with renal dysfunction, current smokers, patients with a recent MI, patients with longer cross clamp times, patients with longer CPB time, and patients receiving ACE inhibitors. CONCLUSION: The relationship between CKMB and TnT following CABG appears to be influenced by patient and operative characteristics. These data do not assess which enzyme more accurately reflects myocardial injury, but does suggest conclusions about myocardial damage may be affected by the biomarker selected in the presence of certain variables. Further study to assess the association between these biomarkers and patient outcomes is warranted.