Augmented Ultrasound-Facilitated, Catheter-Directed Fibrinolysis for PE

Patients with intermediate-high risk pulmonary embolism (PE) comprise a population at increased risk for clinical deterioration despite initially stable hemodynamics. The pathophysiology of hemodynamic deterioration in intermediate-high risk PE includes an abrupt increase in pulmonary vascular resistance, due to proximal as well as distal pulmonary artery occlusion, pulmonary hypertension, right ventricular (RV) pressure overload, and, ultimately, RV failure. While full-dose systemic fibrinolysis for PE has demonstrated efficacy for prevention of early morbidity and mortality, its net clinical benefit is attenuated by the risk of major bleeding, in particular intracranial hemorrhage. Catheter-directed therapies have been demonstrated to facilitate RV recovery while reducing the risk of major bleeding through use of lower-dose fibrinolysis or avoiding it altogether. Specifically, lower-dose regimens for ultrasound-facilitated, catheter-directed fibrinolysis result in sustained recovery of echocardiographically-determined RV function, reduction in Modified Miller Score (large-vessel pulmonary angiographic obstruction), functional status, and quality of life over the year following ultrasound-facilitated, catheter-directed fibrinolysis.

Recently, an upgrade to the output of the ultrasonic core catheter of the EKOS™ Endovascular System (EKOS+™) has demonstrated the ability to enhance fibrinolysis within a lower fibrinolytic dose range in preliminary studies (Boston Scientific Corporation, Maple Grove, MN). Compared with current EkoSonic™ system, a 50% increase in ultrasound power (measured in watts) with EKOS+™ resulted in a 130% increase in in vitro clot lysis compared with conventional catheter-directed fibrinolysis using the same dose of fibrinolytic drug.

SONIC-PE is multicenter, prospective single-arm study of 10 patients with bilateral PE treated with ultrasound-facilitated, catheter-directed lower-dose fibrinolysis (total dose 8 mg tPA given as 2 mg/hour/catheter over 2 hours) followed by 50 patients (total dose 6 mg tPA given as 3 mg/hour/catheter given over 1 hour) with the EKOS+™ system to determine its impact on the change in RV-to-LV diameter, refined Modified Miller Score, and distal pulmonary vascular blood volume as well as assess International Society on Thrombosis and Haemostasis (ISTH) major bleeding. The study will have an adaptive design component with transition to 8 mg tPA/2 hours if there is an excess of bleeding or observed lack of efficacy, as determined by an Independent Study Safety Monitor.