Abstract Body (Do not enter title and authors here): Introduction
Myocardial injury following elective percutaneous coronary intervention (PCI) is associated with reduced long-term survival. Ischemic changes on electrocardiogram (ECG) are an important component of the Universal Definition of Myocardial Infarction (MI), but their prognostic value in the setting of post-PCI myocardial injury remains uncertain.

Research Question
What is the incremental prognostic value of new ischemic ECG changes, or any ischemic ECG findings post-PCI, in patients with post-PCI myocardial injury?

Methods
Adults undergoing elective PCI between 2011 and 2020 without elevated pre-PCI cardiac biomarkers were included if they developed post-PCI myocardial injury, defined by peak CKMB concentration >99% of the upper reference limit. Baseline and post-PCI ECGs (within 24 hours) were reviewed for ischemic ECG findings (ST-segment abnormalities, T-wave abnormalities, and Q-waves), and compared to identify ischemic changes. Long-term mortality was determined from Social Security and National Death Index data. Relationships between ischemic ECG findings and long-term mortality were evaluated in Cox proportional hazards models adjusted for age, sex, and assay-normalized CKMB.

Results
Among 1,745 patients with myocardial injury following elective PCI, 883 (50.6%) had ≥1 ischemic ECG finding post-PCI, and 302 (17.3%) had new ischemic ECG changes from baseline. Median follow-up was 5.2 years with 138 deaths (7.9%). New ischemic ECG changes compared to baseline (n=302) were not associated with increased long-term mortality after multivariable adjustment (7.0% vs. 8.1%, aHR 1.06, 95% CI 0.66–1.71; Figure 1A). When only post-PCI ECGs were considered, the presence of any ischemic finding (n=883) was also not associated with higher mortality (8.5% vs. 7.3%, aHR 1.37, 95% CI 0.98–1.92). In an analysis of ischemic findings on post-PCI ECGs, the presence of any ST-segment depressions (n=105) was associated with increased long-term mortality (16.8% vs. 7.0%, aHR 2.84, 95% CI 1.84–4.38; Figure 1B). Post-PCI ST-segment elevations demonstrated similar but non-significant trends limited by few events.

Conclusion
Among patients with myocardial injury post-PCI, new ischemic ECG changes were not associated with increased mortality. Although the presence of post-PCI ST-segment depressions was associated with increased long-term mortality, other ischemic ECG abnormalities offered limited incremental prognostic value in patients with post-PCI myocardial injury.