The optimal threshold for defining prognostically relevant periprocedural myocardial injury (PMI) in patients with NSTEMI was found to be a post-PCI change in cardiac troponin I (cTnI) of >40%, along with an absolute postprocedural value of ≥5-times the 99th percentile of the upper reference limit (URL), according to a study published Feb. 19 in Circulation.

Using data from the AMIPE (Acute Myocardial Infarction, Prognostic and Therapeutic Evaluation) registry data, Matteo Armillotta, MD, et al., looked at 1,581 patients admitted to Orsola-Malpighi and Maggiore Hospitals in Bologna, Italy with NSTEMI undergoing PCI from January 2017 to April 2022. Among those, 1,412 patients (mean age, 72 years; 28% female) with stable or falling cTnI levels at baseline were included in the study and followed for one year.

Patients were categorized according to the Fourth Universal Definition of Myocardial Infarction into those experiencing PMI with vs. without type 4a MI and no PMI. PMI was defined as a cTnI increase of >20% with an absolute postprocedural value of ≥5-times the 99th percentile URL within 48 hours after PCI.

Results showed that 240 (17%) patients experienced PMI with type 4a MI, 288 (20.4%) had PMI without type 4a MI, and 884 (62.6%) did not experience PMI. Patients with PMI had an increased risk of adverse clinical outcomes; those with type 4a MI had the highest rates of the primary outcome of one-year all-cause mortality and the secondary outcome of major adverse cardiovascular events (MACE) defined as all-cause mortality, nonfatal reinfarction, urgent revascularization, nonfatal ischemic stroke and hospitalization for heart failure.

Of note, a post-PCI change in cTnI >20% but ≤40% showed similar outcomes to patients without PMI, while >40% was identified as the optimal threshold for diagnosing a prognostically relevant PMI. Patients exceeding this threshold had a significant four-fold increased risk of one-year all-cause mortality and three-fold increase of MACE.

The authors state periprocedural ischemic events were frequent in NSTEMI undergoing PCI which held prognostic implications.

"These findings may improve risk stratification, guide more tailored management strategies, and ultimately enhance outcomes for patients with NSTEMI undergoing PCI," the authors write.