Frequency and Prognosis of Alternative Definitions of Occlusion Myocardial Infarction Across the Whole Spectrum of Acute Coronary Syndromes

Background Occlusion myocardial infarction (OMI) refers to a myocardial infarction caused by a persistent or transient, complete or near-complete coronary artery occlusion. Multiple definitions have been proposed, yet their frequency and comparative prognostic relevance remain unclear. Objectives This study sought to evaluate the frequency and prognosis of previously proposed OMI definitions across the whole spectrum of acute coronary syndromes (ACS) from the MATRIX trial. Methods Five alternative OMI definitions were assessed: 1) culprit artery (CA) TIMI flow grade 0; 2) CA-TIMI flow grade 0-1; 3) CA-TIMI flow grade 0-2; 4) CA-TIMI flow grade 0-2 or TIMI flow grade 3 with cardiac troponin >30× upper reference limit; and 5) CA-TIMI flow grade 0-2 or CA-TIMI flow grade 3 with cardiac troponin >100× upper reference limit. The endpoint of interest was 1-year all-cause mortality. Results Among 6,558 patients with ACS, OMI frequency ranged from 37.8% for definition 1 to 76.1% for definition 4. OMI was independently associated with higher 1-year mortality according to definitions 1-4 (adjusted HR: 2.08 [95% CI: 1.56-2.78], 1.97[1.47-2.63], 1.70 [1.25-2.32], 1.47 [1.01-2.12], respectively) but not according to definition 5 (adjusted HR: 1.26 [0.90-1.75]). OMI definitions exclusively based on impaired CA flow (ie, definitions 1-3) improved discrimination, reclassification, and model fit when added to the conventional STE/NSTE-ACS classification. One-year mortality did not differ among patients with NSTE-ACS with OMI definition 1 or 2 compared with ST-segment elevation MI (STEMI) patients. Conclusions OMI defined by impaired CA flow confers prognostic implications beyond the presence or absence of ST-segment elevation in a broad ACS population and identifies patients without ST-segment elevation with 1-year mortality similar to that of STEMI.