Aims: The aimof the present investigationwas to determine the long-termprognostic association of post-procedural cardiac enzyme elevation within the randomised Synergy between Percutaneous Coronary Intervention (PCI) with TAXUS and Cardiac Surgery (SYNTAX) Trial. Methods: 1800 patients with unprotected left main or de novo three-vessel coronary artery disease were randomised to undergo coronary artery bypass graft (CABG) surgery or PCI. Per protocol patients underwent post-procedural blood sampling with creatine kinase (CK), and the cardiac specific MB iso-enzyme (CK-MB) only if the preceding CK ratiowas = 2x the upper limit of normal (ULN). An independent chemistry laboratory evaluated all collected blood samples. Results: Post-procedural CK sampling was available in 1629 of 1800 patients (90.5%). As per protocol, CK-MB analyses were undertaken in 474 of 491 patients (96.5%) in the CABG arm, and 53 of 61 patients (86.9%) in the PCI arm. Within the CABG arm, despite the limitations of incomplete data, a post-procedural CK-MB ratio <3/>= 3 ULNseparated 4-year mortality into low-and high-risk groups (2.3% vs. 9.5%, p = 0.03). Additionally, in the CABG arm, a post-procedural CK-MB ratio = 3 ULN was associated Conclusion: Cardiac enzyme elevations post-CABG or post-PCI are associatedwith an adverse long-termmortality; the causes of which are multifactorial. (C) 2013 Elsevier Ireland Ltd. All rights reserved.