Real-world outcomes of early unfractionated heparin use in NSTEMI patients with acute leukemia and severe thrombocytopenia.

6539 Background: Current AHA/ACC guidelines provide limited guidance for acute non-ST-segment elevation myocardial infarction (NSTEMI) management in patients with active hematologic malignancy and concurrent severe thrombocytopenia, as these individuals have been systematically excluded from randomized trials. Consequently, decisions regarding anticoagulation rely on expert opinion and limited observational data. We evaluated real-world outcomes in patients with acute leukemia, severe thrombocytopenia, and NSTEMI, comparing early unfractionated heparin use with no parenteral anticoagulation. Methods: We conducted a multicenter retrospective cohort study using the TriNetX Research Network to identify adults (≥18 years) with acute leukemia who experienced a first NSTEMI following leukemia diagnosis. Severe thrombocytopenia was defined as a platelet count < 50×10³/µL measured within 24 hours of NSTEMI. Patients with prior intracranial hemorrhage or on chronic anticoagulation were excluded. The primary exposure was unfractionated heparin administered within 24 hours of NSTEMI diagnosis versus no parenteral anticoagulation. Propensity score matching (1:1) was performed for demographics, cardiovascular risk factors and chronic co-morbidities. Primary efficacy outcomes were all-cause mortality at 30 days, 90 days, and 1 year. The primary safety outcome was major bleeding, defined as a composite of intracranial and gastrointestinal hemorrhage at 7 days, 30 days, and 90 days. Kaplan-Meier analysis, hazard ratios (HR), risk ratios (RR), and 95% confidence intervals (CI) were used to assess outcomes. Results: Among 1,734 patients who met the inclusion criteria, 639 received unfractionated heparin and 1095 did not. Following, PSM 528 patients remained in each group. Kaplan–Meier overall survival at 30 days, 90 days, and 1 year was significantly improved in patients receiving early unfractionated heparin (30-day HR = 0.78 0.64-0.96; 90-day HR = 0.77 0.64-0.92; 1-year HR = 0.75 0.64-0.87). Composite major bleeding events at 7 days, 30 days, and 90 days were similar between groups (7-day RR = 1.56 0.95-2.56; 30-day RR = 1.15 0.81-1.77; 90-day RR = 1.24 0.88-1.83). Conclusions: In this large real-world study of patients with acute leukemia, severe thrombocytopenia, and NSTEMI, early unfractionated heparin administration within 24 hours was associated with improved survival without an increased risk of major bleeding, addressing a critical evidence gap in this high-risk population. Overall Survival Timepoint Heparin (%)n=446 No Heparin (%)n=446 HR (95% CI) 30-day 66.9% 59.3% 0.78 0.64-0.96 90-day 55.3% 45.6% 0.77 0.64-0.92 1-year 36.9% 23.8% 0.75 0.64-0.87 Major Bleeding Timepoint Heparin (%)n=446 No Heparin (%)n=446 RR (95% CI) 7-days 7.6% 5% 1.56 0.95-2.56 30-day 10.9% 9.8% 1.19 0. 81-1.77 90-day 14.1% 11.6% 1.27 0.88-1.83