Impact of a blood return system on mechanical thrombectomy-associated blood loss and hemodynamic outcomes in a pulmonary embolism registry
Authors: Toma C 
Published: October 2022

Abstract

Background
Mechanical thrombectomy can treat pulmonary embolism (PE) while eliminating the bleeding risks associated with thrombolytic-based therapies. In longer and more complex procedures, however, blood loss from aspiration-based mechanical thrombectomy can potentially limit thrombus removal.

Purpose
Assess a blood return system's ability to reduce mechanical thrombectomy procedure blood loss and characterize hemodynamic outcomes post-procedure.

Methods
This retrospective analysis of a prospective, multicentre, real-world registry enrolling intermediate- and high-risk PE patients treated with mechanical thrombectomy compared all patients enrolled prior to the availability of a blood return system with all patients whose treatment included use of a blood return system. Linear regression was used to model the blood return system's effect on estimated blood loss. The model was adjusted for patient characteristics and disease factors that may have been different between the treatment groups or related to blood loss.

Results
Complete case analysis was used to identify 319 patients prior to the availability of a blood return system (no blood return), and 50 patients who were treated using a blood return system through January 2022 (blood return). As shown in Table 1, the only significant differences in the summary statistics for the blood return group were 160 ml decreased estimated blood loss (292.5 to 132.5 ml; p&lt;0.01) and a 13.1 minute increase in thrombectomy time (47.9 to 61.0 minutes; p&lt;0.01).
Linear regression modeling revealed that use of a blood return system was associated with a 200 ml (69%) reduction (p&lt;0.01) in blood loss for the average patient and thrombectomy time (Figure 1A). Importantly, the addition of an interaction term between thrombectomy time and blood return showed blood loss reduction increased with thrombectomy time (Figure 1B). Post-procedure mean pulmonary arterial pressure decreased by 7.0 mmHg (33.0 to 26.0 mmHg) in the blood return group and 7.9 mmHg (32.1 to 24.2 mmHg) in the no blood return group. In patients with depressed baseline cardiac index (CI) &lt;2, CI improved by 0.3 L/min/m2 (1.8 to 2.1 L/min/m2) in the blood return group and 0.4 L/min/m2 (1.6 to 2.0 L/min/m2) in the no blood return group, demonstrating normalization of depressed CI in both groups. No hemodynamic outcomes differed significantly between groups (p&gt;0.05).

Conclusions
Treatment with aspiration mechanical thrombectomy in combination with a blood return system achieved equivalent hemodynamic outcomes compared with mechanical thrombectomy alone, while reducing 69% of procedure blood loss. The fact that blood return patients had equivalent hemodynamic improvements suggests these improvements are related to thrombus removal rather than aspiration-related blood loss. The association identified between blood loss and thrombectomy time indicates that thrombus removal is not limited by blood loss when a blood return system is used.

Funding Acknowledgement
Type of funding sources: Private company. Main funding source(s): Inari Medical