A new study suggests that mortality at 1 year significantly increases after procedural myocardial infarction (pMI) and spontaneous myocardial infarction (spMI) with troponin peak >35x upper reference level (URL). Additional findings of the investigation, which enrolled 10,707 patients undergoing percutaneous coronary intervention (PCI), also suggests that for troponin levels <35x, only spMI had a relevant impact on mortality. “The key findings [of this study] indicate that both pMI and spMI with troponin elevation >35x URL were associated with a 4-fold or higher increase in mortality,” said the paper’s authors, led by Alessandro Spirito, MD from Bern University Hospital in Switzerland. “Our findings suggest that troponin elevations exceeding certain thresholds seem to be indicative of substantial myocardial injury and are associated with increased mortality, irrespective of whether the injury is due to spontaneous plaque rupture or erosion or to an iatrogenic mechanism.” Main findings Details of the investigation, which was published in the July 30 issue of the Journal of the American College of Cardiology, notes that among the patients undergoing PCI, 8,515 patients presented with chronic coronary syndrome (CCS) and 2,192 with spontaneous myocardial infarction (spMI). Among CCS patients, the research team found 913 (10.7%) had pMI. Here, troponin peaks >1-5x URL were observed in 53% of patients, while peaks of >5-35x were observed in 41% of patients. Troponin peaks of >35x were observed in 6% of patients. In patients with spMI, troponin peaks >1-5x URL were observed in 24% of patients, while peaks of >5-35x were observed in 38% of patients. Troponin peaks of >35x were observed in 37% of this patient group. Further findings revealed that mortality at 1 year was higher after pMI (7.7%; adjusted hazard ratio [HR]: 4.40; 95% confidence interval [CI]: 1.59-12.2) and spMI (8.5%; adjusted HR: 7.57; 95% CI: 5.44-10.5) with troponin peak >35x URL compared with no-MI (1.4%). The research team also found mortality was also increased after spMI with troponin peak >1-5x or >5-35x URL. Study implications “The findings of the current analysis have important implications. First, they confirm that prognostically relevant pMIs are relatively rare after PCI, occurring in only 0.6% of patients with CCS undergoing PCI,” explained the authors of the paper, which was also published Monday online. “Second, given that pMI with substantial myocardial damage has a similar prognostic relevance as spMI, their inclusion among the key endpoints of interventional clinical trials might be justified, and a separate assessment of these 2 types of events is probably the most appropriate choice.” The study’s implications form the focus of an accompanying editorial comment, in which Michael G. Nanna, MD and Sridhar Mangalesh, MBBS, questioned whether pMI is a valid endpoint for interventional trials. This line of enquiry was considered pertinent given their low incidences and the imprecise definitions that further complicated their measurement. Nanna and Mangalesh commended the study in defining clinically significant pMI, adding weight to the evidence of using optimal biomarker elevation after PCI to identify patients at higher risk. The two experts add that the results also endorse the routine measurement of troponin levels before and after PCI — a recommendation of multiple interventional societies that has yet to fully permeate many health systems. Study limitations The experts identified the study’s single-center design and the use of conventional troponin alone rather than a high-sensitivity troponin assay as factors limiting the finding’s generalizability. Absence of electrocardiographic findings, like new pathologic Q waves, imaging evidence of infarction and angiographic confirmation of vessel occlusion, that were unavailable and could not be incorporated into the study design were also critical. Whilst the present findings supported the threshold of >35x URL, which aligns with the Academic Research Consortium-2 (ARC-2) cutoff, the experts pointed out that varying definitions of pMI could lead to substantially different results depending on which definition was used. “A harmonized definition of pMI from leading professional societies, perhaps centered at a 35x URL troponin elevation as suggested in the present investigation, is a pressing necessity moving forward,” the experts concluded. “A unified definition will pave the way for integrating post-PCI troponin assessment into clinical practice and developing an immovable endpoint for future clinical trials in interventional cardiology.” Study set up 8515 patients with chronic coronary syndrome (CCS) and baseline troponin ≤1x URL or with and 2192 (708 (32.3) female) patients with acute spMI who underwent PCI were included. Out of the 8515 patients, 7602 had no MI (2,006 (26.4%) female) and 913 had experienced a procedural MI (263 [28.8%] female). PMI was defined as post-PCI troponin increase >1x URL in patients with CCS. SpMI comprised any acute coronary syndrome with elevated troponin. The 1-year risk of all-cause death was assessed after pMI and spMI across 3 strata of troponin elevation (>1-5x, >5-35x, and >35x URL), with CCS patients having post-PCI troponin ≤1x URL as a reference group. Conventional troponin I was measured using the Architect methodology (Abbott). Sources: Spirito A, Sartori S, Koshy AN, et al. Mortality After Procedural or Spontaneous Myocardial Infarction. J Am Coll Cardiol. 2024;84:467–477. Nanna MG, Mangalesh S. Searching for Meaning: Refining Troponin Thresholds to Align Risks Between Spontaneous and Procedural Myocardial Infarction. J Am Coll Cardiol. 2024;84:478–481. Image Credit: Richman – stock.adobe.com