No clear guidelines exist for unfractionated heparin (UFH) monitoring in adult patients on veno-arterial extracorporeal life support (VA-ECLS) for refractory cardiogenic shock. In this study, we sought to compare outcomes between anti-factor Xa (FXa) and activated partial thromboplastin time (aPTT) strategies for UFH monitoring during VA-ECLS.

This is a single-center, retrospective review of VA-ECLS patients who received UFH in the cardiothoracic intensive care unit between July 2019 and November 2023. Standard protocol for UFH titration was aPTT goal of 45-60 sec (n = 52) before September 2021, then transitioned to FXa goal of 0.1-0.2 U/mL (n = 50) thereafter. Inverse probability of treatment weighting was used to balance baseline differences between cohorts.

In adjusted analyses, 89.3% of FXa patients and 76.0% of aPTT patients achieved goal range for their respective assay. Total UFH duration (4.0 vs 4.0 days, p = .239) and maximum weight-adjusted UFH dose (9.3 vs 9.4 U/hr/kg, p = .823) remained comparable between adjusted FXa and aPTT cohorts. Moreover, in-hospital mortality (50.3% vs 33.9%, p = .133), major bleeding events (20.6% vs 11.2%, p = .292), and thromboembolic events (30.1% vs 30.1%, p = .998) were not significantly different. Extracorporeal circuit thrombosis and cannula site bleeding were the most frequent events in both groups. Multivariate logistic regression found the FXa strategy was not a significant risk factor for the composite outcome of major bleeding or thromboembolism (OR [95% CI]: 1.539 [0.575, 4.116], p = .393).

In adult VA-ECLS patients at our institution, bleeding and thromboembolic complications occurred at a similar rate regardless of which UFH monitoring strategy was utilized. Further studies in larger and more institutionally diverse cohorts are warranted.