Why is this study important?

Thrombectomy for the treatment of intermediate-risk pulmonary emboli (IPE) has seen widespread adoption despite limited clinical trial data regarding its use. A known problem with thrombectomy is blood loss. In some cases, this can result in post-procedure anemia, intraprocedural hemodynamic instability, and procedure stoppage. Given the known association between blood loss and worse long-term outcomes in percutaneous coronary intervention patients, intraprocedural blood loss may have a tremendous impact on procedural outcomes. The Hēlo Blood Return System (BRS) enables autologous transfusion via filtered blood reinfusion with continuous aspiration mechanical thrombectomy. It is hoped that returning a significant portion of lost blood will mitigate these potential consequences. 

What question was the study supposed to answer?

ENGULF is a prospective, multicenter, single-arm Pivotal Investigational Device Exemption (IDE) trial evaluating the Hēlo thrombectomy system (Endovascular Engineering). Conducted at 19 U.S. hospitals with 40 operators across interventional cardiology, interventional radiology, and vascular surgery participated. Co‑primary endpoints were 48‑hr major adverse events (MAE) and 48‑hr RV/LV ratio reduction. Secondary assessments included procedural efficiency, single‑pass success, and blood loss. This analysis compared 40 BRS patients with 90 non-BRS patients with respect to intraprocedural blood loss and its impact. 

What did the study show?

BRS significantly reduced median blood loss (10cc vs 340cc, p<0.001). All BRS procedures completed without adjunctive therapy vs 5 non-BRS interventions for blood loss. The ability to complete the procedure with a single pass across the heart was significantly higher with BRS (88% vs 72%, p=0.02). The MAE rate was 0% (0/40) in BRS versus 1.1% (1/90) in non-BRS. Blood quality parameters showed no differences (all p > 0.05), indicating no platelet activation or hemolysis. Hemodynamic efficacy (RV/LV reduction) was higher with BRS at 28% versus 25% in non-BRS (p=0.5). Modified Miller reduction was significantly higher with BRS at 22% versus 15% in non-BRS (p<0.001). No corking, device malfunctions, or unanticipated adverse events occurred in either cohort.

Perspective

The trial demonstrates device efficacy and safety comparable to what was seen with prior IDE trials such as EXTRACT‑PE (Indigo) and FLARE (FlowTriever). More exciting is the performance of the BRS. In a field with multiple devices claiming to do the same thing better, the Hēlo BRS is potentially a major step forward. This novel system seems to allow the use of a larger-bore system (15 Fr crossing profile with a 24 Fr expandable clot engagement funnel) without the trade-off of increased blood loss.