Blood Quality and Safety of Autologous Blood Return using a Continuous Aspiration Thrombectomy System for Pulmonary Embolism: Bench and Clinical Evidence from the ENGULF Trial

Autologous blood return during PE thrombectomy offers blood conservation benefits, yet comprehensive blood quality validation remains limited. We evaluated the safety and quality of returned blood using a novel 15Fr continuous aspiration thrombectomy system with integrated blood return capability (BRS) through bench and clinical validation in the ENGULF trial. We hypothesized that BRS-processed blood maintains quality suitable for safe transfusion.

Materials and Methods:

Bench: Five human blood donors underwent hematologic analysis comparing the 15Fr catheter + BRS under worst-case operating conditions against unfiltered blood and a predicate mechanical thrombectomy device with manual filtration system. Blood quality was assessed across 14 parameters in 4 categories (cell counts, blood chemistry, hemolysis, and coagulation) including RBC, WBC, platelets, hematocrit, potassium, bilirubin, LDH, plasma free hemoglobin, and MPV. Statistical comparisons used paired t-tests with p< 0.05.

Clinical: In the prospective, multicenter ENGULF trial, intermediate-risk PE patients underwent thrombectomy with the Hēlo System +/- BRS. Blood quality parameters included hemoglobin, hematocrit, RBC, WBC, platelets, potassium, and MPV at baseline and 48 hours post-procedure.

 

Results:

Bench: Both systems maintained parameters within normal limits. The BRS demonstrated statistically superior performance in hemolysis markers compared to the predicate device. Plasma free hemoglobin, an indicator of RBC damage, was statistically lower with BRS versus predicate (76.8±29.8 vs 111.0±60.8 mg/dL, p=0.006) as was LDH (129.9±28.4 vs 167.5±51.6 U/L, p=0.003). Thrombin activation was equivalent to baseline blood (p=0.401).  Fibrinogen showed no differences between systems.

Clinical: Among 40 BRS and 90 non-BRS patients (age 59.6/63.5, 50%/59% male), no significant differences were observed in any blood quality parameters between BRS and non-BRS patients or between baseline and 48-hour values (p >0.05). No change in MPV confirmed absence of systemic platelet activation.

Conclusion:

Both bench and clinical testing confirmed preserved blood quality without systemic platelet activation. This provides the first comprehensive evidence that blood returned during mechanical thrombectomy using a continuous aspiration source maintains high quality and is safe for autologous transfusion.