Treatment of Chronic Deep Vein Thrombosis (DVT) and Post-Thrombotic Syndrome (PTS) With the EkoSonic® Endovascular System

To evaluate the efficacy of ultrasound accelerated thrombolysis using the EkoSonic® Endovascular System with standard infusion of thrombolytic drug for post-thrombotic syndrome from chronic venous occlusion.

The study is designed to evaluate the safety and efficacy of ultrasound accelerated thrombolysis using the EkoSonic® Endovascular System with standard infusion of a thrombolytic drug for PTS and chronic DVT. Clinical effectiveness will be evaluated using a standard measure of severity of post-thrombotic syndrome over a year.

Eligibility Criteria:
Key Inclusion criteria:

1. Male or female greater than or equal to (≥) 18 years of age and less than or equal to (≤) 75 years of age.
2. Proximal DVT (iliac vein, common femoral vein, deep femoral vein, and femoral vein) that was objectively diagnosed with duplex imaging and/or venography ≥ 6 months prior to study screening.
3. Persistent chronic DVT causing restrictive flow, as confirmed by imaging, within 60 days prior to the study procedure.
4. Villalta score ≥8 for the affected limb within 30 days prior to the study procedure.
5. Failed a minimum of 3 consecutive months of conservative treatment (therapeutic anticoagulation and compression stockings) according to the completed Adherence to Conservative Treatment Form.

Key Exclusion Criteria:

1. Treated with mechanical thrombectomy within 2 weeks of the study thrombolysis procedure.
2. Treated with thrombolysis drugs within 48 hours of the study thrombolytic procedure.
3. Life expectancy less than (\<) 1 year.
4. Body Mass Index (BMI) greater than (\>) 40 kilograms/square meter (kg/m\^2) or per Investigator's discretion participant is able tolerate the procedure and be compliant with post-procedure increased physical activity.
5. No flow in popliteal vein on duplex imaging
6. Isolated iliac vein only thrombus.
7. Thrombus extending ≥ 3 centimeters (cm) into the inferior vena cava (IVC). If central venous occlusion, consider computed tomography (CT) or magnetic resonance venography (MRV). For participants with bilateral DVT, it is recommended that central imaging be performed prior to treatment to evaluate the status of the IVC.
8. Active bleeding, recent (\<3 months) gastrointestinal (GI) bleeding, active peptic ulcer, severe liver dysfunction, and bleeding diathesis.
9. Recent (\<3 months) internal eye surgery or hemorrhagic retinopathy; recent (\<10 days) major surgery, cataract surgery, trauma, cardiopulmonary resuscitation (CPR), obstetrical delivery, or other invasive procedure.
10. History of stroke or intracranial/intraspinal bleed, tumor, vascular malformation, or aneurysm.
11. Active cancer (metastatic, progressive, or treated within the last 6 months). Participants with non-melanoma primary skin cancers are eligible to participate in the study.
12. Hemoglobin \<9.0 milligrams/deciliter (mg/dL) within 24 hours prior to the procedure
13. International normalized ratio (INR) ≥1.5 nanograms/deciliter (ng/dL) within 24 hours prior to the procedure.
14. Platelet count \<100,000 cells/cubic millimeter (cells/mm\^3) or \>700,000 cells/mm\^3 within 24 hours prior to the procedure.
15. Creatinine outside the normal range for the treating institution and considered clinically significant by the Investigator.
16. Uncontrolled hypertension, defined as systolic \>175 millimeters of mercury (mmHg) and a diastolic \>110 mmHg.
17. Use of clopidogrel, ticlopidine, or other thienopyridine antiplatelet drug within 7 days of the study procedure.
18. In the judgment of the clinician, the participant is at high risk for catastrophic bleeding.