Background: Early data on use of catheter-directed therapies (CDT) for treatment of Intermediate or High-Risk pulmonary embolism (PE) show improvement in pulmonary artery systolic pressures (PAsP) and RV/LV ratios. Occasionally a paradoxical rise in PAsP was observed with CDT utilizing ultrasound-assisted thrombolysis (USAT). It is unclear whether this pattern is seen with CDT utilizing mechanical aspiration. Objectives: To investigate and compare the changes in PAsP between those who underwent CDT with USAT to those with mechanical aspiration. Methods: A retrospective analysis of those diagnosed with Intermediate or High-Risk PE who underwent CDT using USAT or mechanical aspiration from 7/2013 to 3/2023. The primary outcome was comparison of PAsP changes between the two modalities. Secondary outcomes include length of stay, mortality, and bleeding complications. Results: A total of 142 patients were analyzed, of which 93 underwent USAT and 49 underwent mechanical thrombectomy. The mechanical thrombectomy group had significantly lower post-intervention PAsP than the USAT group (42.2 ± 13.4 mmHg vs 54.5 ± 15.2 mmHg, p