Trends in Unprotected Left Main Percutaneous Coronary Intervention and Clinical Outcomes.

Importance: Unprotected left main percutaneous coronary intervention (LM PCI) is recognized as a reasonable strategy for patients who have coronary artery disease with low anatomic complexity. However, recent trends in its procedural volume, patient characteristics, and procedural techniques and their association with clinical outcomes have not been well described, making it important to confirm the safety of LM PCI in contemporary clinical practice. Objectives: To examine temporal trends in the use and in-hospital outcomes of unprotected LM PCI in Japan. Design, Setting, and Participants: This retrospective cohort study used prospectively collected data from the nationwide, multicenter Japanese Percutaneous Coronary Intervention registry including approximately 1100 PCI-capable institutions across Japan. Data were restricted to the period after the registry's 2019 update to ensure consistency in definitions. Temporal trends in PCI procedures were analyzed from January 2019 through December 2023. Patients with prior coronary artery bypass grafting, recent cardiogenic shock, cardiac arrest within 24 hours of treatment, restenosis, or balloon angioplasty alone were excluded. Exposures: Calendar year of PCI (2019-2023). Main Outcomes and Measures: The primary outcome was in-hospital mortality. Multivariable logistic regression was used to assess temporal trends and whether differences were explained by baseline or procedural characteristics. Results: Among 851 468 included procedures (mean [SD] patient age, 74.1 [10.2] years; 78.1% men), unprotected LM PCI accounted for 9490 of 182 739 PCI procedures in 2019 (5.2%) and 8583 of 164 332 in 2023 (5.2%). From 2019 to 2023, mean (SD) patient age increased from 73.4 (10.1) to 74.6 (10.1) years, and patients were more likely to have heart failure (increasing from 1676 of 9058 cases in 2019 [18.5%] to 1704 of 8200 [20.8%] in 2023). Unadjusted in-hospital mortality increased from 148 cases in 2019 (1.6%) to 157 in 2023 (1.9%), but this was not significant after adjusting for patient characteristics (adjusted odds ratio for 2023 vs 2019: 1.08; 95% CI, 0.85-1.37). From 2019 to 2023, further adjustment for procedural factors, including increased use of radial access (from 5789 cases [63.9%] to 5985 cases [73.0%]) and mechanical circulatory support (from 828 cases [9.1%] to 941 cases [11.5%]), did not alter the association between year and mortality. Conclusions and Relevance: In a nationwide Japanese PCI registry, unprotected LM PCI consistently accounted for 5% of PCI procedures. Although unadjusted in-hospital mortality rose modestly over time, the findings indicate this was largely explained by increasing patient complexity, with risk-adjusted outcomes remaining stable, supporting the continued role of LM PCI as a safe revascularization option in contemporary practice.