Submassive Pulmonary Embolism Experience With EKOS

Inclusion Criteria: 1. Acute symptomatic PE confirmed by CT, with filling defect in at least one main or segmental pulmonary artery. 2. RV dysfunction as evidenced by RV/LV ratio \> 0.9 on echo 3. Ability to give informed consent or Legally Authorized Representative (LAR) is able to give consent 4. PE symptom duration \< 21 days 5. Age \>18 years 6. And, a MBS baseline measurement above 3 plus at least one of the following: O2 sat \< 90% RA, or inability to maintain a HR \<100, or inability to maintain a Systolic Bp \> 100. Whichever measurement is chosen for inclusion criteria in addition to the MBS will also be used in determination of therapeutic endpoint (i.e. O2 Sat., HR\<100 or BP \>100).. Exclusion Criteria: 1. Stroke or transient ischemic attack (TIA), head trauma, or other active intracranial or intraspinal disease within one year 2. Recent (within one month) or active bleeding from a major organ 3. Hemoglobin (Hgb) \< 8.0 4. Platelets \< 60 thousand/µL 5. Major surgery within seven days 6. Clinician deems high-risk for catastrophic bleeding 7. History of heparin-induced thrombocytopenia (HIT) 8. Pregnancy 9. Catheter-based pharmacomechanical treatment for pulmonary embolism within 3 days of study enrollment 10. Systolic blood pressure less than 80 mm Hg despite vasopressor or inotropic support 11. Cardiac arrest (including pulseless electrical activity and asystole) requiring active cardiopulmonary resuscitation (CPR) 12. Evidence of irreversible neurological compromise 13. Life expectancy \< 30 days 14. Use of thrombolytics or glycoprotein IIb/IIIa antagonists within 3 days prior to inclusion in the study