Procedural myocardial infarction (PMI) rates during PCI and CABG and outcomes following PMI vary according to definition, according to two studies published Sept. 28 in the Journal of the American College of Cardiology.

In an analysis of data from the EXCEL trial, John Gregson, PhD, et al., examined and compared rates and prognostic implications of PMI during PCI and CABG, based on the prespecified protocol definition of PMI (PMIProt) vs. the Third Universal Definition of Myocardial Infarction (UDMI). The study's primary outcome was cardiovascular mortality.

The study consisted of 1,835 patients from the EXCEL trial: 935 who received PCI and 923 who received CABG. PMIProt occurred in 34 patients (3.6%) after PCI and 56 patients (6.1%) after CABG (difference, –2.4%; 95% confidence interval [CI], –4.4% to –0.5%; p=0.015). Based on the Third UDMI definition, PMI occurred in 37 PCI patients (4%) and 20 CABG patients (2.2%) (difference 1.8%; 95% CI, 0.2% to 3.4%; p=0.025). Both definitions were associated with five-year cardiovascular mortality (adjusted hazard ratio [HR], 2.18; 95% CI, 1.13 to 4.23 for PMIProt vs. adjusted HR, 2.87; 95% CI, 1.44 to 5.73 for Third UDMI).

According to the researchers, the consistent hazard after PCI and CABG supports the EXCEL trial's use of PMIProt and its conclusions that PCI and CABG provide similar three- and five-year rates of major adverse cardiovascular events for revascularization of patients with left main coronary artery disease. The researchers conclude that additional research is needed to "determine whether alternative PMI definitions have even higher diagnostic accuracy and greater prognostic utility than those assessed in the present analysis."

In another study, Hironori Hara, MD, et al., used data from the SYNTAX Extended Survival trial to examine PMI rates, based on five different definitions, and their association with 10-year all-cause mortality and impact on composite endpoint of major cardiac or cerebrovascular events at five years in the original trial. The researchers used PMI definitions from the SYNTAX, ISCHEMIA, and EXCEL trials; the Fourth UDMI; and the SCAI definition. The researchers looked at 1,652 patients (91.8%) from the SYNTAX Extended Survival trial, including 857 patients who received PCI and 795 who received CABG.

Based on SYNTAX and Fourth UDMI definitions, the results show PMI rates of 2.7% and 3%, respectively, for PCI vs. 2.4% and 2.1%, respectively, for CABG. According to the ISCHEMIA definition, the PMI rate was 6% in the PCI arm and 8.8% in the CABG arm. Using the SCAI and EXCEL definitions, PMI rates were the same at 5.7% in patients receiving PCI vs. 16.5% among those receiving CABG. There was a stronger PMI-associated mortality based on the SYNTAX and Fourth UDMI definitions vs. EXCEL or SCAI definitions. In addition, most PMI events based on the ISCHEMIA, SCAI and EXCEL definitions were driven by CK-MB >10-times the upper limit of normal. Regardless of the definition used, PMI following PCI was associated with all-cause 10-year mortality, whereas the PMI after CABG was associated with mortality for one year.

The researchers conclude that PMI rates are "highly dependent on their definition." Given the different outcomes based on PMI definition, the authors note that researchers and clinicians "need to be aware of the tremendous impact of the actual definition of PMI on global outcome" and that "large patient-level data will be required to ascertain the impact of PMI on mortality."

"There might need to be acceptance that the same [PMI] definition cannot be fit to both" PCI and CABG Donald E. Cutlip, MD, FACC, writes in an accompanying editorial comment. He notes that the SYNTAX trials support use of the UDMI definition following CABG but not PCI and that biomarking thresholds also are clinically meaningful. "If we cannot find definitions that fit these purposes, then perhaps it is time to remove [PMI] from primary composite endpoints," he concludes.

Clinical Topics: Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention, Atherosclerotic Disease (CAD/PAD), Aortic Surgery, Interventions and Coronary Artery Disease

Keywords: Coronary Artery Disease, Percutaneous Coronary Intervention, Prognosis, Myocardial Infarction, Heart, Coronary Artery Bypass, Cardiology

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