Association of Admission Immature Platelet Fraction with Long-Term Mortality Following Primary Percutaneous Coronary Intervention for STEMI.

BACKGROUND: Immature platelet fraction (IPF) reflects thrombopoietic activity and platelet reactivity and has been associated with adverse cardiovascular outcomes. However, its prognostic value in patients undergoing primary percutaneous coronary intervention (PPCI) for ST-elevation myocardial infarction has not been systematically evaluated. METHODS: We analyzed 1,713 consecutive PPCI patients from a prospective single-center registry (July 2019-April 2026). Patients were stratified into IPF tertiles: low (≤3.0%), mid (3.0-5.1%), and high (>5.1%). The primary endpoint was long-term all-cause mortality, estimated using the Kaplan-Meier method and compared by the log-rank test. All effect estimates were derived from multivariable Cox proportional hazards regression adjusted for age, ejection fraction, sex, hypertension, diabetes mellitus, chronic renal failure, and prior coronary artery disease. Prespecified sensitivity analyses comprised a 3-year truncated analysis and a postdischarge landmark analysis. RESULTS: Among 1,713 PPCI patients (median age: 64 years, 20.9% female), median IPF was 4.2%. Over a median potential follow-up of 3.0 years, 233 deaths (13.6%) occurred. Kaplan-Meier estimated 3-year all-cause mortality increased stepwise across tertiles: 9.1, 10.2, and 18.2% in the low, mid, and high IPF groups, respectively (log-rank p < 0.001). In-hospital mortality showed a nonsignificant trend (2.1, 2.6, and 3.9%; p = 0.157). On multivariable Cox regression, IPF as a continuous variable was not independently associated with long-term mortality (hazard ratios [HR]: 1.039 per 1% increase, 95% confidence intervals [CI]: 0.998-1.081, p = 0.066), whereas the high IPF tertile was independently associated with a 51% higher hazard of death compared with the low tertile (HR: 1.51, 95% CI: 1.08-2.12, p = 0.017). The association persisted in the 3-year truncated analysis (HR: 1.78, 95% CI: 1.23-2.58, p = 0.002) and in the postdischarge landmark analysis (HR: 1.52, 95% CI: 1.04-2.21, p = 0.03). CONCLUSION: High admission IPF (>5.1%) was independently associated with increased long-term mortality after PPCI. Because IPF is automatically reported as part of the admission complete blood count at no additional cost, it may help identify patients who warrant closer postdischarge surveillance. However, external validation in independent cohorts is required before IPF can be incorporated into routine risk stratification.