Contemporary Endovascular Therapies in Treatment of Acute Iliofemoral Deep Vein Thrombosis (CLEAR-DVT)


Guy's and St Thomas' NHS Foundation Trust




Deep Vein Thrombosis


Device: Contemporary endovascular venous intervention by Zelante pharmacomechanical thrombolysis

Study type


Funder types



IRAS 254427

Details and patient eligibility


The goal of this initial proof of principle single arm cohort trial is to determine if contemporary endovascular venous intervention, compared with a 1:1 propensity-matched medical therapy arm of the ATTRACT trial, significantly reduces the 2-year occurrence of Post Thrombotic Syndrome (PTS) in subjects with symptomatic proximal Deep Vein Thrombosis (DVT).

Full description

A single arm cohort will serve as a proof of principle study, and be the foundation for a larger subsequent prospective, Randomised Clinical Trial (RCT). The aim of this initial single arm cohort is to both validate that contemporary catheter directed therapy performed by experienced operators has significant efficacy and safety at 10 days, 30 days, 6 months, 12 months, and 2 years (details below). If a strong signal of efficacy and safety is found in the initial single arm cohort at 30 days and 6 months, this will provide objective evidence to move forward with a larger multicentre, prospective, RCT. If the results of the initial single arm proof of principle cohort do not show efficacy, or there is a safety issue, a larger prospective, RCT will not be performed.


65 estimated patients




16 to 75 years old


No Healthy Volunteers

Inclusion criteria

  • Patient age 16 years to 75 years.
  • Onset of acute DVT symptoms of 14 days or less in the study limb.
  • DVT located in the common and/or external iliac, or common femoral vein
  • Consent to participate in this research study and be willing to commit to study requirements including completion of questionnaires and follow-up visits.

Exclusion criteria

  • In the index leg: established PTS, or previous symptomatic DVT within the last 2 years.
  • In the contralateral (non-index) leg: symptomatic acute DVT a) involving the iliac and/or common femoral vein; or b) for which thrombolysis is planned as part of initial therapy.
  • Limb-threatening circulatory compromise.
  • Pulmonary embolism defined as either massive (Systolic blood pressure < 90 mmHg and/or patient on IV vasoactive medication to support blood pressure), or intermediate high risk pulmonary embolism (PE), as defined by the European Society Guideline on management of PE. Low risk PE and/or intermediate low risk PE can be enrolled.
  • Inability to tolerate contemporary venous intervention procedure due to severe dyspnea or acute systemic illness.
  • Allergy, hypersensitivity, or thrombocytopenia from heparin, Recombinant tissue plasminogen activator (rtPA), or iodinated contrast, except for mild-moderate contrast allergies for which steroid pre-medication can be used.
  • Haemoglobin < 9.0 mg/dl, INR > 1.6 before starting anticoagulation, or platelets < 100,000/ml. Moderate renal impairment in diabetic patients (estimated glomerular filtration rate < 60 ml/min) or severe renal impairment in non-diabetic patients (estimated glomerular filtration rate < 30 ml/min).
  • Active bleeding, recent (< 3 mo) GI bleeding, severe liver dysfunction, bleeding diathesis.
  • Recent (< 3 mo) internal eye surgery or haemorrhagic retinopathy; recent (< 10 days) major surgery, cataract surgery, trauma, cardiopulmonary resuscitation, obstetrical delivery, or other invasive procedure.
  • History of stroke or intracranial/intraspinal bleed, tumor, vascular malformation, aneurysm.
  • Active cancer (metastatic, progressive, or treated within the last 6 months). Exception: patients with non-melanoma primary skin cancers are eligible to participate in the study.
  • Severe hypertension on repeated readings (systolic blood pressure > 180 mmHg or diastolic blood pressure > 105 mmHg). This can be treated, and blood pressure must be stable before venous access is obtained (systolic blood pressure <140 mmHg).
  • Pregnant (positive pregnancy test, women of childbearing potential must be tested).
  • Recently (< 1 mo) had thrombolysis or is participating in another investigational device or drug study that may convolute study results.
  • Life expectancy < 2 years or chronic non-ambulatory status.
  • Inability to provide informed consent or to comply with study assessments (e.g. due to cognitive impairment or geographic distance).
  • Inferior vena cava (IVC) thrombus. Significant thrombus of the IVC, by definition, thrombus extending more than one centimeter above the IVC - common iliac vein confluence will be a cause for exclusion.
  • Inability to obtain access of the enrolled ipsilateral popliteal vein using ultrasound guided micro-puncture technique.
  • History of, or active heparin induced thrombocytopenia (HIT).

Trial design

65 participants in 1 patient group

Acute Iliofemoral DVT
Suitable patients would be invited to take part in this trial as part of standard of care.
Device: Contemporary endovascular venous intervention by Zelante pharmacomechanical thrombolysis

Trial contacts and locations



Central trial contact

Stephen Black; Audrey Hau

Data sourced from

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