Ticagrelor vs. Clopidogrel in ACS Patients Underwent PCI: An Analysis Based on Systemic Immune-inflammation Risk Stratification.

OBJECTIVE: The systemic immune-inflammation index (SII) is an established prognostic marker in coronary artery disease. This study investigated the association between SII and 1-year prognosis in patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI), and explored its potential utility in informing P2Y12 inhibitor selection. METHODS: A total of 15,123 consecutive ACS patients undergoing PCI between January 2021 and December 2022 were enrolled. Patients were stratified into high- and low-inflammation groups based on the optimal SII cut-off derived from receiver operating characteristic analysis. The primary endpoint was 12-month ischemic events, defined as a composite of cardiac death, myocardial infarction, and stroke. Propensity-score matching was performed to compare ticagrelor-based versus clopidogrel-based dual antiplatelet therapy within each group. RESULTS: The optimal SII cut-off was 651 × 109/L. Elevated SII was associated with increased ischemic events (HR 1.86; 95% CI: 1.52-2.28; p < 0.0001) and all-cause mortality (HR 2.44; 95% CI: 1.90-3.13; p < 0.0001). In the low-SII group (1,422 matched pairs), ticagrelor was associated with increased bleeding risk (HR 2.15; 95% CI: 1.60-2.88; p < 0.0001) without association with ischemic benefit. In the high-SII group (1,299 matched pairs), ticagrelor was associated with reduced ischemic events (HR 0.52; 95% CI: 0.33-0.83; p = 0.006), cardiac death (HR 0.45; 95% CI: 0.23-0.86; p = 0.015), and all-cause mortality (HR 0.40; 95% CI: 0.23-0.70; p = 0.001) without association with increased major bleeding. CONCLUSION: The SII is associated with 12-month post-PCI ischemic and mortality risk and demonstrates potential as a candidate biomarker for risk stratification, with exploratory observations of ticagrelor benefit in high-SII and clopidogrel adequacy in low-SII patients.