Periprocedural myocardial infarction after percutaneous coronary intervention (PCI) remains a debated entity, especially in the era of high-sensitivity cardiac troponin assays, which frequently detect biomarker rises even when clinically meaningful ischemia is absent. This review critically examines the main contemporary frameworks used to define these events, including the Fourth Universal Definition of Myocardial Infarction (UDMI), the Academic Research Consortium (ARC)-2 consensus, and the Society for Cardiovascular Angiography and Interventions (SCAI) definition, comparing biomarker thresholds, requirements for objective evidence of ischemia, and procedural criteria. We discuss how differences among definitions shape reported event rates and contribute to heterogeneity in event adjudication across studies. Key pathophysiologic mechanisms of myocardial injury during PCI are summarized, including side-branch compromise, distal embolization, microvascular dysfunction, and mechanical complications. Particular attention is given to the limitations of current criteria, such as incomplete assay standardization, variability in sampling timing, inconsistent reliability of ancillary criteria, including electrocardiography and imaging, and an uneven relationship between biomarker elevation and subsequent outcomes. Finally, we outline priorities for future updates, including harmonization of biomarker thresholds, greater emphasis on relative biomarker dynamics, and structured adjudication that integrates biomarkers with objective ischemic evidence. These steps may improve diagnostic specificity, reduce misclassification, and strengthen the clinical and trial relevance of periprocedural ischemic endpoints.