High-Risk Non-ST Elevation Acute Coronary Syndrome Outcomes in Patients Treated with Unfractionated Heparin Monitored Using Anti-Xa Concentrations versus Activated Partial Thromboplastin Time

BACKGROUND: While the activated partial thromboplastin time (aPTT) is the most widely used assay to monitor unfractionated heparin (UFH), providing a general measure of the extent of anticoagulation, it does not reliably correlate with the blood concentration of heparin or its antithrombotic effect. While cost and availability have limited the widespread use of UFH in hospitals, monitoring UFH with heparin levels has been shown to reduce both the number of monitoring tests and the time to a therapeutic range. OBJECTIVES: To compare outcomes in patients with non-ST elevation acute coronary syndrome (ACS) treated with weight-based UFH monitored with anti-Xa concentrations versus aPTT. METHODS: A retrospective chart review was completed in patients admitted with high-risk ACS and compared to the UFH arm of the SYNERGY trial. The primary outcome included the clinical endpoint of all-cause death or non-fatal myocardial infarction until time of hospital discharge. Safety endpoints evaluated included incidence of stroke and major bleeding. RESULTS: The primary endpoint occurred in 6.3% of patients in the study cohort compared to 6.5% of patients in the heparin arm of the SYNERGY trial at 48 hours (P = .006). Bleeding was reduced in the study cohort with a significant decrease in GUSTO severe bleeding (P = .007). Additionally the study cohort had significantly fewer patients with an absolute drop in hemoglobin or hematocrit. Thrombolysis in Myocardial Infarction (TIMI) major and minor bleeding, rate of transfusion, and platelet counts were similar between groups. CONCLUSIONS: Outcomes for high-risk ACS patients receiving heparin monitored by anti-Xa concentrations are noninferior to heparin monitored by aPTT.