Prognostic significance of elevated creatine kinase MB after coronary bypass surgery and after an acute coronary syndrome: results from the GUARDIAN trial.

OBJECTIVE: To determine if the correlation between magnitude of creatine kinase-myocardial band release after coronary artery bypass surgery and 6-month mortality is comparable to that of patients admitted with an acute coronary syndrome.
METHODS: The GUARDIAN trial tested the efficacy of cariporide, an Na+/H+ exchange inhibitor, on reduction of myocardial ischemia or death in high-risk patients. We compared 6-month survival in a cohort of 2332 GUARDIAN patients scheduled for coronary artery bypass surgery at entry with 4233 acute coronary syndrome patients stratified by level of creatine kinase-myocardial band release. Cumulative 6-month survival by creatine kinase-myocardial band categories was performed using life table analysis, adjusting for variables known to impact prognosis using Cox regression.
RESULTS: The 6-month mortality rates for coronary artery bypass surgery patients with peak creatine kinase-myocardial band ratios of <1, > or =1 and <5, > or =5 and <10, and > or =10 upper limits of normal (ULN) were 5.8, 2.8, 5.9, and 12.0%, respectively (P <.0001). The 6-month mortality rates for acute coronary syndrome patients with peak creatine kinase-myocardial band ratios of <1, > or =1 and <5, > or =5 and <10, and > or =10 ULN were 6.3, 9.8, 10.0, and 12.3%, respectively (P <.0001). Patients with coronary artery bypass surgery or acute coronary syndrome had similar adjusted 6-month survival estimates at normal creatine kinase-myocardial band levels and when the creatine kinase-myocardial band level was > or =10 ULN. Patients with coronary artery bypass surgery had significantly better survival at intermediate enzyme levels (> or =1 and <10 ULN; P <.001).
CONCLUSIONS: Modest elevations of creatine kinase-myocardial band release (> or =1 and <10 ULN) after coronary artery bypass surgery are not associated with adverse 6-month survival, in contrast to that seen in acute coronary syndrome patients. Routine creatine kinase-myocardial band sampling should be considered in all higher-risk patients undergoing coronary artery bypass surgery procedures to identify the sizable cohort of patients with creatine kinase-myocardial band release > or =10 ULN; these patients may benefit from postoperative angiotensin-converting enzyme inhibitor and beta-blocker therapy. Newer cardioprotective agents that reduce the number of patients with marked creatine kinase-myocardial band release are currently being tested in large randomized controlled clinical trials.