Randomized Trial Comparing Standard Versus Ultrasound-Assisted Thrombolysis for Submassive Pulmonary Embolism: The SUNSET sPE Trial

Objectives: The aim of this trial was to determine whether ultrasound-assisted thrombolysis (USAT) is superior to standard catheter-directed thrombolysis (SCDT) in pulmonary arterial thrombus reduction for patients with submassive pulmonary embolism (sPE).

Background: Catheter-directed therapy has been increasingly used in sPE and massive pulmonary embolism as a decompensation prevention and potentially lifesaving procedure. It is unproved whether USAT is superior to SCDT using traditional multiple-side-hole catheters in the treatment of patients with pulmonary embolism.

Methods: Adults with sPE were enrolled. Participants were randomized 1:1 to USAT or SCDT. The primary outcome was 48-hour clearance of pulmonary thrombus assessed by pre- and postprocedural computed tomographic angiography using a refined Miller score. Secondary outcomes included improvement in right ventricular-to-left ventricular ratio, intensive care unit and hospital stay, bleeding, and adverse events up to 90 days.

Results: Eighty-one patients with acute sPE were randomized and were available for analysis. The mean total dose of alteplase for USAT was 19 ± 7 mg and for SCDT was 18 ± 7 mg (P = 0.53), infused over 14 ± 6 and 14 ± 5 hours, respectively (P = 0.99). In the USAT group, the mean raw pulmonary arterial thrombus score was reduced from 31 ± 4 at baseline to 22 ± 7 (P < 0.001). In the SCDT group, the score was reduced from 33 ± 4 to 23 ± 7 (P < 0.001). There was no significant difference in mean thrombus score reduction between the 2 groups (P = 0.76). The mean reduction in right ventricular/left ventricular ratio from baseline (1.54 ± 0.30 for USAT, 1.69 ± 0.44 for SCDT) to 48 hours was 0.37 ± 0.34 in the USAT group and 0.59 ± 0.42 in the SCDT group (P = 0.01). Major bleeding (1 stroke and 1 vaginal bleed requiring transfusion) occurred in 2 patients, both in the USAT group.

Conclusions: In the SUNSET sPE (Standard vs. Ultrasound-Assisted Catheter Thrombolysis for Submassive Pulmonary Embolism) trial, patients undergoing USAT had similar pulmonary arterial thrombus reduction compared with those undergoing SCDT, using comparable mean lytic doses and durations of lysis.