Implications of Alternative Definitions of Peri-Procedural Myocardial Infarction After Coronary Revascularization

Abstract

Background: Varying definitions of procedural myocardial infarction (PMI) are in widespread use.

Objectives: This study sought to determine the rates and clinical relevance of PMI using different definitions in patients with left main coronary artery disease randomized to percutaneous coronary intervention (PCI) versus coronary artery bypass grafting (CABG) surgery in the EXCEL (Evaluation of XIENCE versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization) trial.

Methods: The pre-specified protocol definition of PMI (PMI_Prot) required a large elevation of creatine kinase-MB (CK-MB), with identical threshold for both procedures. The Third Universal Definition of MI (types 4a and 5) (PMI_UD) required lesser biomarker elevations but with supporting evidence of myocardial ischemia, different after PCI and CABG. For the PMI_UD, troponins were used preferentially (available in 49.5% of patients), CK-MB otherwise. The multivariable relationship between each PMI type and 5-year mortality was determined.

Results: PMI_Prot occurred in 34 of 935 (3.6%) patients after PCI and 56 of 923 (6.1%) patients after CABG (difference -2.4%; 95% confidence interval [CI]: -4.4% to -0.5%; p = 0.015). The corresponding rates of PMI_UD were 37 (4.0%) and 20 (2.2%), respectively (difference 1.8%; 95% CI: 0.2% to 3.4%; p = 0.025). Both PMI_Prot and PMI_UD were associated with 5-year cardiovascular mortality (adjusted hazard ratio [HR]: 2.18 [95% CI: 1.13 to 4.23] and 2.87 [95% CI: 1.44 to 5.73], respectively). PMI_Prot was associated with a consistent hazard of cardiovascular mortality after both PCI and CABG (p_interaction = 0.86). Conversely, PMI_UD was strongly associated with cardiovascular mortality after CABG (adjusted HR: 11.94; 95% CI: 4.84 to 29.47) but not after PCI (adjusted HR: 1.14; 95% CI: 0.35 to 3.67) (p_interaction = 0.004). Results were similar for all-cause mortality and with varying PMI_UD biomarker definitions. Only large biomarker elevations (CK-MB ≥10× upper reference limit and troponin ≥70× upper reference limit) were associated with mortality.

Conclusions: The rates of PMI after PCI and CABG vary greatly with different definitions. In the EXCEL trial, the pre-specified PMI_Prot was associated with similar hazard after PCI and CABG, whereas PMI_UD was strongly associated with mortality after CABG but not after PCI. (EXCEL Clinical Trial [EXCEL]; NCT01205776).

Keywords: coronary artery bypass grafting surgery; coronary artery disease; left main disease; myocardial infarction; percutaneous coronary intervention; prognosis; revascularization.