Effect Of Pharmacomechanical Catheter-Directed Thrombolysis On Pulmonary Segmental Artery Occlusions- Insights From The CTPA Core Laboratory Analysis Of The RESCUE Trial.

Purpose: The RESCUE study was an IDE trial evaluating the effect of Pharmacomechanical Catheter-directed thrombolysis (PM-CDT) with the Bashir Endovascular Catheter in patients with acute intermediate-risk pulmonary embolism (PE). This study reports the post hoc analysis of the core laboratory data assessing the effect of PM-CDT on segmental pulmonary arteries (PA) occlusions.

Materials and Methods: A substantial reduction in distal vascular volume in patients with acute PE is a significant predictor of 30- and 90-day mortality. The likely cause of this reduction is total and subtotal occlusions of the segmental PA branches. To date the effect of PM-CDT on the total and subtotal occlusions of these branches is not known. We used the baseline and 48-hour post treatment contrast-enhanced chest computed tomography pulmonary angiography (CTPA) of patients enrolled in the RESCUE trial with symptomatic PE and right-ventricular-to-left-ventricular diameter (RV/LV) ratio ≥ 0.9. The core-laboratory assessed data from the RESCUE trial was used and the primary endpoint of this analysis was the change in the number of segmental PA branches with total or subtotal occlusions after 48 hours compared to baseline before PM-CDT.

Results: 106 patients enrolled across 18 United States sites were used for this analysis. The total dose of recombinant tissue plasminogen activator (r-tPA) was 14 mgs in bilateral PE and 7 mgs in unilateral PE over 5 hours, delivered via the expanded Bashir catheter.  At 48 hours post therapy, the number of segmental PA that had total or subtotal occlusions decreased from 31.9% to 8.7% (p < 0.0001) a 72.5% reduction. This reduction was also noted in the proximal PA branches with a reduction from 28.7% to 11.0% (p < 0.0001) a 61% reduction. The reduction in segmental artery occlusion correlated significantly with magnitude of reduction in RV/LV ratio (p=0.0021).

Conclusion: In this prospective study of intermediate-risk PE, PM-CDT with the Bashir catheter and low- dose tPA was associated with a marked reduction in total and subtotal occlusion of segmental pulmonary arteries. Future randomized controlled studies should consider assessment of this outcome to better evaluate the mechanism of right ventricular off-loading in these patients.