Acute or Subacute Iliofemoral Vein Thrombosis: Aspiration for Flow Restoration Versus Standard Anticoagulation (IF-FLOW)

Vascular Surgery Department of Beijing Tsinghua ChangGung Hospital

This trial is a prospective, multicenter, randomized controlled, superiority study. According to the inclusion and exclusion criteria for clinical research subjects, 104 patients with acute deep vein thrombosis involving the iliac and femoral veins were recruited. Qualified subjects were randomly (1:1) assigned to either the experimental group or the control group. The experimental group received thrombus aspiration, with or without balloon dilation, stent implantation, and other accompanying surgical treatments, combined with standard anticoagulant therapy, while the control group received only standard anticoagulant therapy. The efficacy and safety of the experimental group in treating acute iliac and femoral vein thrombosis were compared. The main efficacy endpoint of this study is the 24 month postoperative composite endpoint, with the following hierarchical order: 1. in-hospital mortality or treatment upgrade; 2. Recurrent venous thrombosis or newly developed pulmonary embolism of the target lesion within 24 months; 3. Severity of Villalta score at 24 months; 4. Change in VEINES score after 24 months. Simultaneously observe other secondary efficacy endpoints and safety endpoints. Clinical follow-up was conducted before discharge, 30 days after surgery, 6 months after surgery, 12 months after surgery, and 24 months after surgery.

Study Overview

• Status: Not yet recruiting
• Conditions: Postthrombotic Syndrome; Deep Vein Thrombosis of Lower Limb
• Intervention / Treatment: Procedure: Thrombosis aspiration

Detailed Description

This is a prospective, multicenter, randomized controlled, superiority clinical trial. A total of 104 patients with acute or subacute iliofemoral deep vein thrombosis (DVT) are planned to be enrolled. Participants will receive either thrombus aspiration combined with standard anticoagulant therapy or standard anticoagulant monotherapy according to the randomization principle. The trial aims to verify the efficacy and safety of thrombus aspiration plus standard anticoagulant therapy versus standard anticoagulant therapy alone in the treatment of acute or subacute iliofemoral deep vein thrombosis.

Clinical follow-up assessments will be conducted at pre-discharge, 30 days, 6 months, 12 months, and 24 months after the procedure.

The hierarchical composite endpoint at 24 months post-procedure is defined as the primary efficacy endpoint.

Secondary efficacy endpoints include: immediate post-procedure thrombus clearance success rate (intervention group only), 30-day thrombus recurrence rate, Villalta score, VEINES-QOL/Sym quality of life questionnaire for venous insufficiency, and concomitant treatment (excluding treatment escalation).

Secondary safety endpoints include: major bleeding events within 30 days post-procedure, serious adverse events related to aspiration therapy and concomitant endovascular therapy, and serious adverse events other than major bleeding associated with anticoagulant therapy.

The trial is designed to evaluate the efficacy and safety of thrombus aspiration combined with standard anticoagulant therapy versus standard anticoagulant monotherapy for acute or subacute iliofemoral deep vein thrombosis.

Eligible subjects who meet the inclusion and exclusion criteria of the clinical trial will be randomly assigned (1:1) to either the intervention group (thrombus aspiration + standard anticoagulant therapy) or the control group (standard anticoagulant therapy). Physicians will conduct follow-up of subjects via outpatient visits, telephone interviews, and other means, with simultaneous efficacy and safety evaluations performed throughout the follow-up period.

of primary efficacy.

The hierarchical composite endpoint indicators are, in order: in-hospital death or treatment escalation, recurrent venous thrombosis of the target lesion or new-onset pulmonary embolism within 24 months, severity of the Villalta score at 24 months, and change in the VEINES score at 24 months. Monte Carlo simulation was used for sample size estimation. First, a fixed sample size was assumed, and 3,000 simulations were performed based on this sample size and the estimated parameters (see the table above). Statistical power was calculated as the proportion of rejecting the null hypothesis across the 3,000 simulations, and the assumed sample size was adjusted according to the obtained power.

Assuming the incidence of each hierarchical endpoint in the two groups is as shown in the table above, hypothesis testing was performed for superiority using a Z-test based on normal approximation. The simulation results indicate that with a one-sided α of 0.025, a total sample size of 88 patients (randomly assigned 1:1 to the experimental and control groups) provides approximately 85% statistical power to meet the requirement for superiority inference of the primary endpoint. Accounting for an approximately 15% dropout rate (5% due to withdrawal, loss to follow-up, or missed visits [excluding in-hospital death], and 10% due to missing Villalta and VEINES scores at 24 months), the final sample size is 104 patients.

Determination of Randomization Allocation Subjects were randomly assigned at a 1:1 ratio to the experimental group (thrombus aspiration combined with standard anticoagulant therapy) or the control group (standard anticoagulant therapy).

Stratified block randomization was adopted for group allocation in this trial, with stratification by participating study centers, and random allocation sequences were generated at a 1:1 ratio. After subjects signed the informed consent form, investigators at each sub-center completed randomization allocation via the randomization system.

Treatment Regimen

1. Treatment Allocation Investigators at each sub-center screened eligible subjects randomly in accordance with the above criteria. Subjects were allocated at a 1:1 ratio to either the experimental group or the control group.

   1.1 Experimental Group (Thrombus Aspiration Therapy) Subjects in the experimental group received thrombus aspiration therapy, and concomitant additional surgical procedures (e.g., catheter-based thrombus aspiration) were allowed based on clinical conditions. All subjects concurrently received standard anticoagulant pharmacotherapy.

   Thrombus Aspiration: Thrombus removal was performed only using thrombus aspiration catheters based on direct negative pressure principle. Combination with other mechanical thrombectomy devices/system principles is prohibited, including but not limited to: stent retrievers, pharmacomechanical thrombectomy (e.g., AngioJet catheter), mechanical thrombectomy devices (e.g., Aspirex). Thrombus aspiration was terminated when target vessels achieved complete recanalization with no residual thrombus (thrombus burden score = 0) as assessed by study physicians.

   If significant venous stenosis or occlusion remained after thrombus removal, balloon angioplasty and/or stent implantation were recommended for venous lesions with diameter stenosis ≥50% or lesions presenting obvious collateral circulation on angiography.

   Standard Anticoagulant Pharmacotherapy: All patients in the experimental group received a standard anticoagulant regimen. Coagulation parameters were monitored regularly during treatment to maintain anticoagulant effects within a safe therapeutic window.

   1.2 Control Group (Standard Anticoagulant Pharmacotherapy) Subjects in the control group received standard anticoagulant pharmacotherapy as the conventional treatment for acute or subacute iliofemoral deep vein thrombosis. Patients in the control group were not allowed to receive thrombus aspiration or any additional volume-reducing surgical interventions, and were managed with medication only.

   Standard Anticoagulant Pharmacotherapy: Control patients were administered standard anticoagulant therapy in accordance with clinical guidelines, including but not limited to low molecular weight heparin, warfarin, or direct oral anticoagulants (DOACs). Coagulation function, hepatic and renal function were closely monitored throughout treatment to ensure the safety of anticoagulation.

   Treatment Duration and Monitoring: Anticoagulant therapy was continued until the predefined study endpoint. Regular clinical examinations including hematological tests and imaging assessments were performed to evaluate therapeutic efficacy and safety profiles.

   1.3 Permitted Adjunct Endovascular Therapy Inferior Vena Cava (IVC) Filter: Physicians in both experimental and control groups could decide on IVC filter implantation and subsequent retrieval based on clinical judgment and individual patient conditions.

   Catheter-Directed Thrombolysis (CDT): For experimental patients receiving thrombus aspiration, intraoperative and postoperative catheter-directed thrombolysis was permitted to optimize thrombectomy efficacy, with a maximum treatment duration within 24 hours after the index procedure.

   Concomitant Additional Surgical Therapy: Experimental patients undergoing thrombus aspiration could receive other concomitant surgical interventions as clinically indicated. Following percutaneous catheter thrombus aspiration, balloon angioplasty and/or stent implantation were recommended for venous lesions with diameter stenosis ≥50% or obvious collateral circulation on angiography.

2. Treatment During Follow-up

A unified standard anticoagulant regimen was adopted for both the experimental group (thrombus aspiration plus standard anticoagulant therapy) and the control group (standard anticoagulant therapy) throughout the follow-up period. Direct oral anticoagulants are recommended as follows:

Rivaroxaban: Factor Xa inhibitor. Recommended dosage: 15 mg twice daily for 21 days, followed by a maintenance dose of 20 mg once daily.

Dabigatran: Direct thrombin inhibitor. Recommended dosage: 150 mg twice daily. The minimum duration of anticoagulant therapy was 3 months. For special populations, investigators could administer equivalent alternative anticoagulant regimens based on individual patient conditions and the above recommendations.

All implemented anticoagulant strategies, including the specified study regimen, guideline-equivalent alternative regimens, or clinically adjusted individualized anticoagulant schemes, shall be documented in detail in the Case Report Form (CRF).

• Study Type: Interventional
• Enrollment (Estimated): 104
• Phase: Not Applicable

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age 18-80, gender unrestricted;
• Diagnosed as acute or subacute proximal deep venous thrombosis of the lower extremities through lower extremity venous ultrasound or enhanced CT of the lower extremity veins, with involvement of at least the common iliac vein, external iliac vein, or common femoral vein;
• The subjects met the criteria for standard anticoagulation therapy combined with thrombus aspiration along with standard anticoagulation therapy;
• The patient fully understands and voluntarily signs a written informed consent form;
• Willing and able to comply with all the visit, treatment, and assessment procedures specified in the study protocol.

Exclusion Criteria:

• Bilateral deep iliofemoral vein thrombosis;
• Femoral edema or femoral white swelling;
• Inferior vena cava thrombosis;
• History of deep vein thrombosis with a diagnosis of moderate to severe post-thrombotic syndrome;
• The affected limb has previously had a venous stent implanted;
• There are anatomical abnormalities affecting the intervention pathway, such as hypoplasia or dysplasia of the inferior vena cava, or other malformations of the iliac or inferior vena cava;
• Presence of active major bleeding or clinically significant bleeding risk (hemoglobin <80g/L or platelet count <50×109/L);
• Severe coagulation dysfunction, with an international normalized ratio >1.7;
• Uncontrolled severe hypertension (systolic blood pressure >180 mmHg or diastolic blood pressure >105 mmHg after medication);
• Severe renal impairment, with a glomerular filtration rate <30 mL/min/1.73m²;
• Any interventional treatment for the target deep vein thrombosis within 30 days prior to enrollment;
• Female patients in pregnancy or lactation;
• Known history of allergies to drugs used during the study (such as contrast agents, anticoagulants, etc.);
• Active malignant tumor;
• In the judgment of the researchers, there are any other comorbidities, conditions, or poor adherence that may affect the study evaluation or place the patient at high risk.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
No Intervention: Standard anticoagulation group; only standard anticoagulant therapy
Experimental: Thrombosis aspiration group; thrombus aspiration, with or without balloon dilation, stent implantation, and other accompanying surgical treatments, combined with standard anticoagulant therapy	Procedure: Thrombosis aspiration; Thrombus aspiration, with or without balloon dilation, stent implantation, and other accompanying surgical treatments, combined with standard anticoagulant therapy

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Postoperative hierarchical composite endpoint at 24 months.	This trial employs a superiority design using the win ratio method for the hierarchical composite endpoint of primary efficacy. The hierarchical composite endpoint indicators are, in order: in-hospital death or treatment escalation, recurrent venous thrombosis of the target lesion or new-onset pulmonary embolism within 24 months, severity of the Villalta scale at 24 months, and change in the Venous Insufficiency Epidemiological and Economic Study-Quality of Life/Symptoms (VEINES--QOL/Sym）score at 24 months.	24-month post-operation

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Thrombosis recurrence rate	Thrombosis recurrence rate	30 days post-operation
Villalta Scale	Villalta Scale 1. Scale Composition The scale consists of 5 clinical signs and 5 subjective symptoms, each rated from 0 to 3 points: 0 = Absent, 1 = Mild, 2 = Moderate, 3 = Severe 1.1 Subjective Symptoms (5 items) Lower limb pain Lower limb aching and distending discomfort Lower limb heaviness Leg cramp Skin pruritus 1.2 Clinical Signs (5 items) Lower limb edema Calf skin pigmentation Subcutaneous lipodermatosclerosis / skin induration Lower limb varicose veins Skin ulceration 2. Scoring Rules Total score = Sum of scores of all 10 items Total score range: 0-30 points 3. Severity Grading Criteria (Clinically accepted, applicable for clinical trial protocol) 0-2 points: No post-thrombotic syndrome (No PTS) 3-4 points: Mild PTS 5-9 points: Moderate PTS ≥ 10 points: Severe PTS Note: If active venous ulceration is present, it is directly classified as severe PTS, regardless of the total score.	30 days, 6 months, 12 months, and 24 months postoperatively
VEINES-QOL/Sym Score	Venous Insufficiency Epidemiological and Economic Study-Quality of Life/Symptoms (VEINES-QOL/Sym) Scale (A total of 25 items, each scored from 1 to 5 points). The 25 items belong to the following categories: Physical Function Social Life and Daily Activities Work and Housework Emotional and Psychological Status Distress over Lower Limb Appearance Rating scale: = No impact at all; = Mild impact; = Moderate impact; = Marked impact; = Severe impact Scoring Method The total score is the sum of all 25 items, ranging from 25 to 125 points. A higher score indicates a greater impact of venous disease on quality of life.	30 days, 6 months, 12 months, and 24 months postoperatively
Postoperative massive hemorrhage	Postoperative massive hemorrhage	30 days
Immediate Postoperative Thrombus Clearance Success Rate (Experimental Group Only)	Proportion of subjects achieving Grade II / Grade III thrombus clearance immediately after procedure among all subjects in the experimental group. Thrombus Burden Assessment Common iliac vein □Score 0 □Score 1 □Score 2 □Score 3 External iliac vein □Score 0 □Score 1 □Score 2 □Score 3 Common femoral vein □Score 0 □Score 1 □Score 2 □Score 3 Superficial femoral vein (proximal) □Score 0 □Score 1 □Score 2 □Score 3 Superficial femoral vein (distal) □Score 0 □Score 1 □Score 2 □Score 3 Popliteal vein □Score 0 □Score 1 □Score 2 □Score 3 Immediate Postoperative Thrombus Clearance Grade; Grade I Clearance (<50%); Grade II Clearance (50%～95%); Grade III Clearance (95%～100%) Note 1: Score 0: No residual thrombus (<50% stenosis/occlusion); Score 1: Partial thrombus (50%～90% occlusion); Score 2: Partial occlusion (90%～95% occlusion); Score 3: Complete occlusion (95%～100% occlusion). Note 2: Thrombus clearance rate formula: (Preoperative score - Postoperative score) / Preoperative score × 100%	Immediately after procedure

Collaborators and Investigators

• Sponsor: Weiwei Wu

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2026
• Primary Completion (Estimated): April 30, 2028
• Study Completion (Estimated): April 30, 2030

Study Registration Dates

• First Submitted: April 16, 2026
• First Submitted That Met QC Criteria: May 1, 2026
• First Posted (Actual): May 7, 2026

Study Record Updates

• Last Update Posted (Actual): May 7, 2026
• Last Update Submitted That Met QC Criteria: May 1, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Vascular Diseases; Cardiovascular Diseases; Embolism and Thrombosis; Venous Insufficiency; Thrombosis; Venous Thrombosis; Postthrombotic Syndrome
• Other Study ID Numbers: 26439-4-01

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No