Objective To explore the frailty development trajectory and its influencing factors in elderly patients with acute coronary syndrome (ACS) after percutaneous coronary intervention (PCI). Methods Using a convenience sampling method, 234 elderly ACS patients were enrolled as the research subjects. Baseline data were collected using a self⁃designed general information questionnaire. Frailty, activities of daily living, sleep quality, social support, and depression were assessed at 1 day, 6 months, and 12 months post‑PCI using the Tilburg Frailty Indicator (TFI) scale, Barthel index, Pittsburgh sleep quality index (PSQI), Social Support Rating Scale (SSRS), and 5‑Item Geriatric Depression Scale (GDS‑5). Latent class growth modeling (LCGM) was applied to fit the frailty development trajectory of elderly patients with ACS after PCI, and multivariate Logistic regression model was used to identify factors influencing frailty development trajectory. Results Three potential categories of frailty development trajectories in elderly ACS patients after PCI were identified as follows: non‑frailty slow‑decline group (42.7%), a low‑frailty stable‑maintenance group (20.9%), or high‑frailty slow‑worsening group (36.4%). Statistically significant differences were observed in age, sex, educational level, Barthel index score, PSQI score, SSRS score, and GDS‑5 score between the three groups (P<0.05). Multivariate Logistic regression analysis results revealed that age >70 years, elevated PSQI score and elevated GDS‑5 score were risk factors for frailty development of elderly ACS patients after PCI, while elevated Barthel index score and elevated SSRS score were protective factors (P<0.05). Conclusion Frailty development after PCI in elderly ACS patients exhibits marked heterogeneity and is influenced by age, activities of daily living, sleep quality, social support, and depressive symptoms. Early identification of high‑risk patients and targeted interventions should be emphasized in clinical practice.  

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