Ultrasound-Facilitated, Low-Dose Fibrinolysis for Acute PE

Study Questions:

What are safety and efficacy outcomes associated with ultrasound-facilitated, catheter-directed, low-dose fibrinolysis using the EkoSonic Endovascular System catheter for acute pulmonary embolism (PE)?


The SEATTLE II study was a prospective, single-arm, multicenter trial of acute PE; patients with evidence of massive or submassive PE were included. Patients had a right ventricular (RV)-to-left ventricular (LV) diameter ratio ≥0.9 by chest computed tomography (CT). Patients were administered 24 mg of tissue-plasminogen activator (t-PA) either as 1 mg/hr for 24 hours with a unilateral catheter or 1 mg/hr/catheter for 12 hours with bilateral catheters. The primary safety outcome was GUSTO-defined major and moderate bleeding within 72 hours of procedure initiation. The primary efficacy outcome was the change in chest CT-measured RV/LV diameter ratio within 48 hours of procedure initiation.


Of the 150 patients, 31 had massive and 119 had submassive PE. Mean RV/LV diameter ratio decreased from a baseline to 48 hours post-procedure by 0.42 (1.55 vs. 1.13, p < 0.001). Mean pulmonary artery systemic pressure (51.4 mm Hg vs. 36.9 mm Hg, p < 0.001) and modified Miller Index score (22.5 vs. 15.8, p < 0.001) also decreased post-procedure. Major bleeding occurred in one patient, while moderate bleeding occurred in 15 patients (10%). No patients suffered intracranial hemorrhage.


The authors concluded that use of an ultrasound-facilitated, catheter-directed, low-dose fibrinolysis strategy in patients with massive and submassive PE decreased RV dilation, reduced pulmonary hypertension, decreased anatomic thrombus burden, and minimized intracranial hemorrhage risk.


This single-arm study explores the safety and efficacy outcomes of a low-dose fibrinolysis strategy delivered using an ultrasound-facilitated catheter in the setting of acute massive or submassive PE. Current management strategies for massive and submassive PE include use of systemic fibrinolysis (full dose and “half” dose) and catheter-directed fibrinolysis. However, each of these strategies is associated with major bleeding risk, which may be mitigated by this study’s management approach. Whether use of an ultrasound-facilitated, catheter-directed, low-dose fibrinolysis strategy will improve clinical outcomes (not just surrogate markers) in ‘real-world’ acute massive and submassive PE patients remains to be described.

Clinical Topics: Anticoagulation Management, Dyslipidemia, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Pulmonary Hypertension and Venous Thromboembolism, Vascular Medicine, Lipid Metabolism, Pulmonary Hypertension, Computed Tomography, Echocardiography/Ultrasound, Nuclear Imaging

Keywords: Anticoagulants, Catheterization, Fibrinolysis, Hemorrhage, Hypertension, Pulmonary, Intracranial Hemorrhages, Pulmonary Embolism, Secondary Prevention, Thrombosis, Tissue Plasminogen Activator, Tomography, X-Ray Computed, Ultrasonography, Vascular Access Devices

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