Primary percutaneous coronary intervention (PPCI) is an effective method for the clinical treatment of acute ST-segment elevation myocardial infarction (STEMI). For patients who miss the optimal time window, optimal management of these patients remains controversial.To compare the effects of different timing of percutaneous coronary intervention on the long-term prognosis of elderly patients with acute ST-segment elevation myocardial infarction (STEMI) with time from symptom onset > 12 hours.Elderly acute STEMI patients with time from symptom onset > 12 hours in the period from July 2021 to July 2022 in the Department of Cardiology, Affiliated Hospital of Hebei University, were randomly divided into four groups: group 1 (immediate invasive strategy, percutaneous coronary interventions (PCI) < 24 hours after symptoms onset, n = 80), group 2 (early invasive strategy, 24-< 72 hours after symptoms onset, n = 80), group 3 (delayed invasive strategy after symptoms onset, 72-< 168 hours after symptoms onset, n = 80), and group 4 (late PCI group after symptoms onset, ≥ 168 hours after symptoms onset, n = 80). Primary study end points were 12-month cardiac mortality, nonfatal myocardial infarction (MI), target-vessel revascularization, and heart failure-related rehospitalization.There were no significant differences between groups in cardiac mortality, nonfatal MI and target-vessel revascularization. During follow-up, heart failure-related rehospitalization was higher in group 1 than in the other groups (18.8% vs. 5.1% vs. 7.4% vs. 6.3%, p = 0.010). Compared with group 1, group 2, group 3 and group 4 had lower heart failure-related rehospitalization (HR = 0.250, 95% CI: 0.083-0.753, p = 0.014) (HR = 0.377, 95% CI: 0.146-0.971, p = 0.043) (HR = 0.320, 95% CI: 0.116-0.879, p = 0.027).For acute STEMI patients who missed the optimal time of PCI, immediate PCI did not reduce adverse clinical outcomes.Copyright: © 2024 Polish Society of Cardiothoracic Surgeons (Polskie Towarzystwo KardioTorakochirurgów) and the editors of the Polish Journal of Cardio-Thoracic Surgery (Kardiochirurgia i Torakochirurgia Polska).