Fibrinogen Levels and Bleeding Risk in Patients Undergoing Ultrasound-Assisted Catheter-Directed Thrombolysis for Submassive Pulmonary Embolism

We sought to test the hypothesis that patients undergoing ultrasound-assisted catheter-directed thrombolysis (USAT) with standard alteplase and heparin dosing would not develop significant depletion of systemic fibrinogen, which may account for the lower risk of bleeding seen in contemporary trials. We also sought to compare the relative outcomes of individuals with submassive pulmonary embolism (PE) undergoing USAT and anticoagulation alone.Utilizing a single-center prospective registry, we identified 102 consecutive adult patients with submassive PE who were considered for USAT based on a standardized treatment algorithm between November 2016 and May 2019. Patients not receiving USAT therapy were treated with anticoagulation alone.Baseline characteristics were generally similar between groups (n = 51 in each group). Major bleeding rates were not significantly different between groups (2.0% vs 5.9% in USAT vs control, respectively; P=.62). Notably, no USAT patient experienced clinically significant hypofibrinogenemia (mean trough fibrinogen, 369.8 ± 127.1 mg/dL; minimum, 187 mg/dL). The mean trough fibrinogen of patients experiencing any bleeding event (major or minor) was 306.6 mg/dL (SE, 23.9 mg/dL) vs 380.3 mg/dL (SE, 20.4 mg/dL) in those without a bleeding event (P=.02).In this cohort analysis of patients undergoing USAT, there was no evidence for clinically significant depletion of fibrinogen or intracranial hemorrhage. Although our data suggest an association between lower fibrinogen levels and bleeding events, our results are not clear enough to suggest a clinically useful fibrinogen cut-off value. Further study is needed to determine the utility of routine fibrinogen monitoring in this population.