Single-session mechanical thrombectomy for iliofemoral deep vein thrombosis using a dual mechanism of action device combining basket and rotational thrombectomy

Abstract

Objective

Interventional treatments for acute iliofemoral deep vein thrombosis (DVT) remain controversial after publication of the Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis (ATTRACT) study. Interventions have been shown to reduce post-thrombotic syndrome severity and improve quality of life in DVT patients, but have been accompanied by risk of major bleeding from thrombolytics. We describe thrombus removal using a novel combined basket-rotational thrombectomy device that minimizes the need for thrombolytics or repeat procedures.

Methods

The aim of this prospective, nonrandomized, multicenter, first-in-human study of 19 patients with acute iliofemoral DVT was to evaluate the safety and performance of the Pounce venous thrombectomy system ≤12 months after treatment. The primary performance end point was defined as procedural success through achievement of Society of Interventional Radiology (SIR) grade II lysis in treated vessels with freedom from procedural adverse events. Secondary end points included venous disease severity assessments using the Villalta scale and the Venous Clinical Severity Score, patient quality-of-life measurement using the Venous Insufficiency Epidemiological and Economic Study-Quality of Life questionnaire, and calf circumference measurements taken at baseline, 24 hours, and 1 month.

Results

The primary end point of complete or near-complete thrombus removal (Society of Interventional Radiology grade II or III) was achieved in all patients. All study device-related safety end points were met, with no major bleeding or device-related adverse events. Of the 19 patients treated, 16 (84.2%) did not receive thrombolytics during the procedure. Post-thrombotic syndrome (Villalta scale >4) was identified in 17 of 19 patients (89.5%) at baseline, 4 of 13 patients (30.8%) available for follow-up at 6 months, and 2 of 11 patients (18.2%) at 12 months. The median Venous Clinical Severity Score decreased (P < .001) from 8.5 (interquartile range [IQR], 7-10) at baseline to 4 (IQR, 2-4) at 1 month after the procedure and was similar at 6 months (2; IQR, 2-5) and 12 months (2; IQR, 1.5-3) after the procedure. The median Venous Insufficiency Epidemiological and Economic Study-Quality of Life questionnaire score improved (P < .001) by 62.7 from baseline (19.3; IQR, 10.8-34.5) to 1 month (82.0; IQR, 65.8-89.0) after the procedure, and remained high at 6 months (88.4; IQR, 61.9-93.3) and 12 months (93.7; IQR, 81.0-96.6). Median Venous Insufficiency Epidemiological and Economic Study-Quality of Life questionnaire score improved (P < .001) by 60.0 from baseline (27.5; IQR, 11.0-50.5) to 1 month (87.5; IQR, 80.5-93.0) after the procedure, and remained high at 6 months (88.0; IQR, 58.8-95.0) and 12 months (90.0; IQR, 84.0-97.0). The median calf circumference decreased (P = .089) from 39 cm (IQR, 35-47.8 cm) at baseline to 36 cm (IQR, 32.5-40.5 cm) at 24 hours after the procedure and was 34.5 cm (IQR, 33.2-38.5 cm) at 1 month.

Conclusions

The Pounce device is safe and effective for removal the of thrombus in patients with acute iliofemoral DVT. Initial results demonstrate improvements in venous disease severity and patient quality of life.

Article Highlights.

• •Type of Research: Multicenter prospective cohort study
• •Key Findings: Single-session thrombectomy using the Pounce mechanical thrombectomy device demonstrated safety in this first in human study. Patient outcomes were encouraging with the primary end point of complete or near-complete thrombus removal as defined by the Society of Interventional Radiology criteria being achieved in all patients. Clinical outcome measures were good with an overall post-thrombotic syndrome rate of 18.2% at 12 months, suggesting potential in this small study for mechanical thrombectomy providing clinically effective outcomes.
• •Take Home Message: The Pounce device is safe and effective for the removal of iliofemoral thrombus in patients with acute deep vein thrombosis.

The treatment of venous disease is gaining importance among endovascular specialists. Although the endovascular management of peripheral arterial disease has progressed rapidly in the past two decades, endovascular management of venous disease is at a relatively early stage.¹ Deep vein thrombosis (DVT) is associated with acute complications, such as pulmonary embolism, and longer term complications, notably post-thrombotic syndrome (PTS).² The 2021 guidelines from the European Society of Vascular Surgery recommend consideration of early thrombus removal strategies for selected patients with symptomatic iliofemoral DVT.³ However, several large trials of interventional techniques have shown conflicting results, with improvement in clinical outcomes, but at the cost of significantly increased major bleeding4, 5, 6 driven principally by the use of thrombolytic agents.⁷

Current endovascular treatment methods involve catheter-directed thrombolysis (CDT); pharmacomechanical CDT (PCDT), which combines pharmacologic thrombolysis and mechanical thrombectomy; percutaneous mechanical thrombectomy, which removes thrombus using a mechanical mode of action; balloon venoplasty; iliac vein stenting; and manual aspiration.⁸ Percutaneous mechanical thrombectomy devices can be used without thrombolytics or with thrombolytics when lytic agents are not contraindicated.⁹ It is clear from the aforementioned studies that interventional therapies for DVT could be improved by decreasing the bleeding risk associated with use of thrombolytics.

Vetex Medical Ltd. (Galway, Ireland) developed the Pounce, a device that facilitates mechanical-only thrombus disruption and removal in a single session and offers the potential benefit of minimizing the use of thrombolytics. The device, which obtained clearance from the U.S. Food and Drug Administration in December 2020 and CE marking in May 2021, is now offered by (Surmodics, Inc., Eden Prairie, MN). Venous Thrombus Extraction (VETEX) was a multicenter, first-in-human study to evaluate the safety and performance of the Pounce venous thrombectomy system for ≤12 months after the index procedure.

Methods

Study design

This prospective, nonrandomized, multicenter, first-in-human study assessed the safety and performance of the Pounce system for removal of thrombus in acute iliofemoral DVT. The study was sponsored by Vetex Medical Ltd. and approved by the competent authorities and ethics committees for each of the investigational centers. All study procedures were performed in accordance with the protocol, good clinical practice guidelines, the Declaration of Helsinki, and applicable regulations. All patients provided written informed consent before enrolling in the study. Data were collected on case report forms and monitored independently against source data.

The study was designed to include a minimum of five patients who did not require thrombolytics during the first one or two passes of the Pounce system, if deemed clinically appropriate. Follow-up care of patients after the procedure consisted of standard of care regarding the use of compression stockings and anticoagulation.

Study population

Patients >18 years of age with acute iliofemoral DVT confirmed by color Doppler ultrasound examination and magnetic resonance venography or computed tomography venography who had a symptom duration of ≤14 days were eligible for enrollment. Exclusion criteria included an existing stent in the treatment vein, a prior history of PTS in the index leg, hypotension, active cancer, or bleeding. Eligibility criteria for the study are available on https://www.clinicaltrials.gov/ (identifier, NCT03489135).

Device description

The Pounce Venous Thrombectomy System (Surmodics, Inc.), is a novel device intended for mechanical declotting and controlled and selective infusion of physician specified fluids, including thrombolytics, in the peripheral vasculature. The device includes a spring-tension cobalt-chromium basket designed to disrupt and collect thrombus and an extraction screw designed to macerate and remove the thrombus. A constant-force spring in the handle of the device is designed to allow the basket to maintain wall apposition and predictable radial force within the device's indicated vessel diameter range (6-16 mm). With a pullback motion from the operator, the basket separates organized thrombus from the vein wall and feeds it into the extraction screw, aided by suction force created by the extraction screw's rotation. The extraction screw runs the length of the catheter, facilitating transport of thrombotic material from the basket to a collection container outside the body. If desired, operators may infuse thrombolytic agents via a port in the outer sheath lumen (Fig 1).

Fig 1.

Pounce venous thrombectomy system, which includes a spring-tension basket and extraction screw with suction for collection and removal of thrombus. Additional ports on the catheter/device allow infusion of thrombolytics, if needed.

Procedural techniques

Percutaneous access was gained in the ipsilateral leg under ultrasound guidance and a 10F introducer sheath was placed into the popliteal vein. A 0.018″ guidewire was placed, the Pounce system was prepared in accordance with the instructions for use, and the vessel was treated under fluoroscopic guidance (Fig 2). As per the instructions for use, the vessel was treated with up to three passes of the device. Adjunctive therapies were performed according to standard clinical practice. Intravascular ultrasound (IVUS) use was encouraged but not mandated.

Fig 2.

Example of prethrombectomy (L) and (R) post-thrombectomy venogram.

Definitions and end points

The primary performance end point for the study was defined as procedural success through the preparation and use of the device to achieve Society of Interventional Radiology (SIR) grade II lysis (50%-95% thrombus removal) or above, with freedom from procedural adverse events. SIR grading was determined by the treating physician after the procedure using fluoroscopic images and subsequently evaluated by an independent core laboratory (Syntropic CoreLab, Columbus, OH). Based upon venography, residual thrombus of ≤5% was considered complete and >5% to 55% was considered near-complete thrombus removal.

The core laboratory used software (PIE Medical Imaging, Maastricht, the Netherlands) to precisely measure and calculate the area of thrombus before the procedure and compare with measurements after the procedure.

Secondary end points included venous disease severity assessments using calf circumference measurements, Villalta score, Venous Clinical Severity Score (VCSS), and patient-reported quality-of-life assessments using the Venous Insufficiency Epidemiological and Economic Study-Quality of Life questionnaire (VEINES QOL/Sym).

Thrombectomy time was defined as the time from the introduction of the Pounce thrombectomy system to removal of the access sheath, including time used for imaging while using the device.

Baseline and follow-up assessments

Pretreatment imaging assessments included computed tomography venography or magnetic resonance venography and a color Doppler ultrasound examination. In addition to recording standard baseline assessments, quality-of-life assessments (VEINES-QOL/Sym), venous disease severity scoring (Villalta score and VCSS), and calf circumference measurements were also evaluated at baseline (days −4 to 0). Quality-of-life and disease questionnaires were assessed at 1, 6, and 12 months after the procedure and calf circumference measurements at 24 hours and 1 month after the procedure. Adverse events and concomitant medications were also collected at each time point.

Statistical methods

Descriptive statistics are presented as counts and percentages for categorical variables and median with interquartile range (IQR) for continuous variables, rounded to one decimal place. Kruskal-Wallis tests were used to assess the difference in each of these four outcomes across timepoints, with Mann-Whitney U tests used for pairwise comparison. However, such tests do not account for clustering of outcomes within patients. Linear mixed models, including a random intercept, were used to account for this clustering, with further adjustment for body mass index, age, and gender in each model. Shapiro-Wilks tests were applied to the residuals of these models to assess their normality assumption. All analyses were performed in R v4.0 (R Core Team, Vienna, Austria).

Results

Between November 2018 and March 2020, a total of 19 patients were enrolled and treated at centers in the UK (n = 8), Germany (n = 6), Ireland (n = 2), and Bulgaria (n = 3). Fig 3 presents patient disposition. Physical examination was performed at 24 hours after the procedure or on discharge (if <24 hours), and at 1 month (35 ± 10 days) after the procedure. Quality of life was assessed at baseline (day −4 to day 0), 1 month (35 ± 10 days), 6 months (±14 days), and 12 months (±14 days) after the procedure. Duplex ultrasound imaging scans were performed before the index procedure, within 24 hours or before discharge, and at 1 month. All patients completed the primary study end point of SIR grade II or III thrombus removal and no procedural adverse events. Fifteen patients completed follow-ups to 12 months. One patient was lost to follow-up after 24-hour follow-up and discharge. After completion of 1-month follow-up visits, one patient withdrew consent and two other patients exited the study; the latter two patients completed the study under an initial protocol which limited follow-up to 1 month. The 12-month Villalta and VCSS data could not be collected on four patients owing to coronavirus disease 2019-related limitations on office visits.

Fig 3.

Patient disposition. ∗Owing to coronavirus disease 2019-related restrictions on office visits, Villalta and Venous Clinical Severity Score (VCSS) data were not collected from four subjects.

Patient characteristics

A summary of patient baseline characteristics, including disease severity, is provided in Table I. The median age of patients was 58.0 years (IQR, 34.0-69.0 years), 73.7% were female, and 73.7% of treatments were performed in the left leg. PTS of any grade (Villalta score ≥5) was identified in 89.5% of patients, with severe PTS (Villalta score ≥15) identified in 57.9% of patients.

Table I.

Baseline characteristics

Characteristic	Median [IQR]) or number (%) (n = 19)
Age, years	58.2 [34.7-68.0]
Gender
Female	14 (73.7)
Male	5 (26.3)
BMI (kg/m2) (n = 18)	28.5 [24.1-31.1]
Index leg
Left	14 (73.7)
Right	5 (26.3)

Symptom severity per Villalta score (n = 19)
None or minimal (score 0-4)	2 (10.5)
Mild (score 5-9)	5 (26.3)
Moderate (score 10-14)	1(5.3)
Severe (score ≥15)	11 (57.9)

BMI, Body mass index; IQR, interquartile range.

Procedural characteristics

Table II provides index procedure characteristics. All 19 patients treated had successful completion of treatment, with 16 (84.2%) receiving no thrombolytics during the procedure. An inferior vena cava filter was placed in five patients (26.3%) at the physician's discretion, all of which were subsequently removed. Adjunctive procedures included stenting in 14 patients (73.7%).

Table II.

Index procedure characteristics

Characteristic	No. (%) or median [IQR] (n = 19)
Complete or near complete thrombus removala	19 (100)
IVC filter used
Yes	5 (26.3)
No	14 (73.7)
Device passes	3 [2-3]
Thrombolytics used during procedure
Yes	3 (15.8)
No	16 (84.2)
Stenting after thrombectomy
Yes	14 (73.7)
No	5 (26.3)
Chronic component to thrombus noted
Yes	12 (63.2)
No	7 (36.8)
Thrombectomy time includes imaging assessmentsb (n = 18) (mins)	23 [11.2-32.5]
Procedure time (minutes) including adjunctive therapies (venoplasty, stenting, etc)c	66 [45.5-86.0]

IVC, Inferior vena cava; IQR, interquartile range.

^aComplete = SIR grade III (>95%) and near complete = SIR grade II (50%-95%). Independently adjudicated by a CoreLab.

^bIntroduction of the Pounce Venous Thrombectomy System to final removal (includes imaging assessments - information recorded by sponsor).

^cStarting from the introduction of the Pounce Venous Thrombectomy System and finishing at the time of removal of the access sheath.

Thrombectomy time was a median of 23 minutes (IQR, 11.2-32.5 minutes) with a median of 3 passes (IQR, 2-3 passes) of the device to achieve thrombus removal. Total procedure time, including adjunctive therapies such as venoplasty and stenting, was a median of 66 minutes (IQR, 45.5-86.0 minutes). The presence of chronic thrombus was noted upon completion of the procedure in 12 patients (63.2%).

Stents were placed after clot removal in 14 of 19 patients (73.7%) after identification of outflow obstruction by the operator. A summary of stents used per patient is provided in Table III. IVUS examination was used in 11 of 19 of the patients to aid procedure and assess clot reduction. The numbers are too small to allow for analysis of additional benefit from the use of IVUS examination.

Table III.

Stent type length and diameter for 14 of 19 patients in whom stents were placed. Veniti (Boston Scientific), ABRE (Medtronic), Venovo (BD), Blueflow (Plus Medica), Protégé (Medtronic)

Patient	Stent brand	Stent diameter, mm	Stent length, mm
1	Veniti Abre	14 14	120 150
2	Veniti Blueflow	16 12	60 60
3	Veniti Abre	14 14	120 120
4	Protégé	14	60
5	Protégé	12	80
6	Abre Abre	14 14	120 150
7	Veniti	16	120
11	Venovo	n/a	n/a
12	Veniti	14	120
13	Veniti	16	120
14	Venovo	14	160
15	Veniti Venovo	16 14	120 160
16	Abre x2	14 14	60 150
17	Venovo	14	120

End points

Investigators assessed that SIR grade III thrombus removal (complete) was achieved in 7 of 19 patients (36.8%) and SIR grade II thrombus removal (near complete) was achieved in 12 of 19 patients (63.2%). Subsequently, the independent core laboratory adjudicated 12 of 18 patients (66.7%) to SIR grade III and 6 of 18 patients (33.3%) to SIR grade II. One patient was excluded from core laboratory analysis owing to insufficient imaging.

In evaluating the difference between investigator and core laboratory for the primary goal of SIR grade II or above the investigators scored this in 19 of 19 patients and the core laboratory in 18 of 18. For the specific grading, investigators were found to be more conservative than the core laboratory were found to give a lower SIR grading than the core laboratory with investigators grading 12 of 19 as SIR grade II and 7 of 19 as SIR grade III vs the core laboratory, where 6 of 18 were graded as SIR grade II and 12 of 18 as SIR grade III. Because the disagreement was not material to the primary end point, there was no communication or resolution of disagreement.

There were no device-related or major bleeding adverse events. All the device-related safety end points were met, with no reports of symptomatic pulmonary embolism, recurrent DVT, transfusion, periprocedural bleeding, clinically significant hemolysis, device-related serious adverse events, or device-related complications. There were no procedure-related adverse events; therefore, the primary performance end point was achieved in all 19 patients.

Impact on quality of life

Clinical outcomes are presented in Table IV and Fig 4. The presence of PTS as determined by a Villalta score of ≥5 was identified in 3 of 17 (17.6%), 4 of 13 (30.8%), and 2 of 11 (18.2%) patients at 1, 6, and 12 months of follow-up, respectively. None of the 11 patients available for Villalta assessment at 12 months developed moderate or severe PTS (Villalta score >9). Of the two patients who had PTS at 12 months, one had been stented and one had not.

Table IV.

Venous disease scoring, quality of life outcomes, and calf circumference

Variable	Baseline	24 Hours	1 Month	6 Months	12 Months	P value
Villalta Score	15.0 (7.0-18.5)		2.0 (1.0-3.0)	3.0 (1.0-5.0)	2.0 (0.5-3.0)	<.001
PTS			3/17 (18)	4/13 (31)	2/11 (18)
VCSS	8.5 (7.0-10.0)		4.0 (2.0-4.0)	2.0 (2.0-5.0)	2.0 (1.5-3.0)	<.001
VEINES QOL Score	19.3 (10.8-34.5)		82.0 (65.8-89.0)	88.4 (61.9-93.3)	93.7 (81.0-96.6)	<.001
VEINES Sym Score	27.5 (11.0-50.5)		87.5 (80.5-93.0)	88.0 (58.8-95.0)	90.0 (84.0-97.0)	<.001
Calf circumference, cm	39.0 (35.0-47.8)	36.0 (32.5-40.5)	34.5 (33.2-38.5)			.089

PTS, Post-thrombotic syndrome.

Descriptive statistics (median and interquartile range for continuous, count and percentage for categorical). The P values are from Kruskal-Wallis tests for continuous variables and Fisher's exact test for categorical variables, comparing levels across timepoints. PTS defined as a Villalta Score of greater than 4 points at the time of assessment.

Fig 4.

Boxplot of each outcome over time, with Mann-Whitney test P values. VEINES, Venous Insufficiency Epidemiological and Economic Study-Quality of Life questionnaire.

The VCSS decreased (P < .001) from a median of 8.5 (IQR, 7-10) at baseline to a median of 4 (IQR, 2-4) at 1 month after the procedure. The median VCSS was similar at 6 months (2; IQR, 2-5) and 12 months after the procedure (2; IQR, 1.5-3). The median VEINES QOL improved (P < .001) by 62.7 from baseline (19.3; IQR, 10.8-34.5) to 1 month (82.0; IQR, 65.8-89.0) after the procedure and remained high at 6 months (88.4; IQR, 61.9-93.3) and 12 months (93.7; IQR, 81.0-96.6). Median VEINES Sym improved (P < .001) by 60.0 from baseline (27.5; IQR, 11.0-50.5) to 1 month (87.5; IQR, 80.5-93.0) after the procedure and remained high at 6 months (88.0; IQR, 58.8-95.0) and 12 months (90.0; IQR, 84.0-97.0). The median calf circumference measurements decreased (P = .089) from 39 cm (IQR, 35-47.8 cm) at baseline to 36 cm (IQR 32.5-40.5 cm) at 24 hours after the procedure and were 34.5 cm (IQR, 33.2-38.5 cm) at the 1-month follow-up.

Results from a linear mixed model for each outcome assessment over time are presented in the Supplementary Table, online only. The model accounts for within- and between-patient clustering, age, body mass index, and gender. All Shapiro-Wilk P values were >.05, suggesting the normality assumption for these linear mixed models was valid. There was a decrease of 5.19 in average VCSS from baseline to 1 month after the procedure (95% confidence interval [CI], −3.91 to −6.46; P < .001), and this change was similar comparing baseline to 6 months after the procedure (5.44 mean reduction; 95% CI, −4.1 to −6.78; P < .001) and 12 months after the procedure (6.48 mean reduction; 95% CI, −5.05 to −7.9; P < .001). There was an increase of 51.88 in average VEINES QOL score from baseline to 1 month after the procedure (95% CI, 40.12-63.64; P < .001), and this change was similar comparing baseline to 6 months (50.98 increase; 95% CI, 38.72-63.24; P < .001) and 12 months (57.29 increase; 95% CI, 44.77-69.81; P < .001) after the procedure. There was an increase of 52.11 in average VEINES Sym score from baseline to 1 month post-procedure (95% CI, 39.40-64.83; P < .001), and this change was similar comparing baseline to 6 months (42.66 increase; 95% CI, 29.37-55.94; P < .001) and 12 months (53.10 increase; 95% CI, 39.52-66.68; P < .001) after the procedure. There was a reduction of 4.81 cm in average calf circumference from baseline to 24 hours after the procedure (95% CI, −7.17 cm; P < .001), with a similar change from baseline to 1 month after the procedure (4.63 cm reduction; 95% CI, −7.16 cm; P < .001).

Discussion

In this first-in-human study, the Pounce venous thrombectomy system was demonstrated to be safe and effective. A minimum of SIR grade II thrombus removal was achieved in all 19 patients (100%), with SIR grade III (complete thrombus removal) achieved in most patients. Notably, a chronic component was identified in the majority of patients (63%), demonstrating thrombus of mixed morphology despite symptom duration of only ≤14 days. This finding is consistent with previous reports that have found symptom duration to be of little value in predicting the actual composition of venous thrombi.¹⁰

In this study, thrombus removal was achieved without use of intraprocedural thrombolytics in most patients (84.2%), which suggests this device may provide effective clinical treatment with reduction in the risk and cost associated with thrombolytic use. These prospective results are similar to a retrospective study performed by Koksoy et al¹¹ to evaluate the Cleaner PCDT device during the treatment of acute (≤14 days) and subacute (15-28 days) DVT. In the Koksoy study, grade II removal or better was achieved in 32 of 33 patients with acute DVT (97.6%) with concomitant use of tissue plasminogen activator during the thrombectomy procedure. Results from the VETEX study demonstrate excellent performance of the Pounce system in the absence of thrombolytics.

These initial results are in keeping with those published in the Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis (ATTRACT) trial for thrombus removal; however, the clinical outcomes are better than those seen in ATTRACT, albeit it with small numbers.⁷ No patients in the VETEX study developed moderate or severe PTS and only 2 of 11 patients had mild PTS (Villalta score 5-9) at 12 months. These encouraging data suggest that modern treatment may improve the results seen in previous trials of DVT intervention. In the VETEX study, improvement over ATTRACT results may have been due to the higher stenting rate observed in VETEX; however, the 12-month patency rates in the VETEX study were also higher than those reported by the ATTRACT investigators in the subgroup data from patients who underwent duplex ultrasound imaging.¹² It is possible that the higher rate of stent placement in this study accounts for some of this difference, but small numbers preclude firm conclusions.

Major bleeding is the most frequent complication of endovascular thrombus removal.¹³ The ATTRACT Trial reported major bleeding ranging in treated patients with iliofemoral DVT from 0.5% with anticoagulation alone to 1.5% with PCDT plus anticoagulation.^7,13 There were no major bleeding complications or device-related adverse events observed in the VETEX study. All study device-related safety end points were met with no occurrence of prespecified events. All adverse events were adjudicated by an independent clinical events committee.

Scorings observed at the 1-month follow-up were indicative of outcomes observed in subsequent follow-up at 6 and 12 months. This aligns with findings observed by Kahn et al.¹⁴ These evaluations were accompanied by reductions in calf circumference of 3.0 cm and 4.5 cm, respectively, at 24 hours and 1 month after the procedure (Table IV and Fig 3). These results resemble the findings of other studies, whereby removal of thrombus using mechanical and/or pharmacomechanical methods reduced symptoms.^7,8 These data also suggest that early outcomes provide a good indication of long-term success, with results at 1 month predicting 12-month outcomes.

Finally, the results seen in the VETEX study were achieved with a median of three passes of the device per patient, despite the device's relatively small (10F) size. This finding suggests that the novel combination of a wall-to-wall basket for thrombus capture and an extraction screw operating within the basket may add an element of efficiency to debulking thrombus from large veins.

This study is limited by the small sample size and nonrandomized nature of the assessment, which limits the broad applicability of conclusions and therefore further data is needed to evaluate the clinical value of mechanical thrombectomy devices such as the pounce system. In addition only 11 of the 19 patients were able to complete all follow-up visits owing to the impact of the coronavirus disease 2019 pandemic, which further limits the power of the study for firm conclusions.

Conclusions

The VETEX study provides initial evidence that the Pounce venous thrombectomy system is safe and effective for removal of thrombus in acute iliofemoral DVT patients. The primary performance end point of this study was achieved in all patients with no device-related adverse events or device malfunctions and minimal use of thrombolytics. Initial results demonstrate quality-of-life improvements and reduction in disease state scoring. Future studies with larger sample size are needed to confirm the results of the VETEX study.

Author Contributions

Conception and design: SB, NT, GO, ML

Analysis and interpretation: SB, NT, GO, ML

Data collection: SB, LB, MK, IP, SW

Writing the article: SB, GO, ML

Critical revision of the article: SB, NT, LB, GO, MK, IP, SW, ML

Final approval of the article: SB, NT, LB, GO, MK, IP, SW, ML

Statistical analysis: SB

Obtained funding: Not applicable

Overall responsibility: SB

Funding

Sponsored by Vetex Medical Ltd. (Galway, Ireland), who were supported by a grant from the European Union’s Horizon 2020 research and innovation program under grant agreement No 874205.

Disclosures

S.B. acknowledges Consulting/Speakers fees from Surmodics and Vetex. M.L. acknowledges consulting fees from Vetex and Surmodics. G.S. acknowledges stock options in Vetex.

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From the American Venous Forum

Supplementary Data

.

Supplementary Table (online only).

Model results from linear mixed models

Model	Timepoint	Estimate	95% CI	P value
VCSS	Baseline	8.87	7.66 to 10.09	<.001
	1 month	−5.19	−6.46 to −3.91	<.001
	6 month	−5.44	−6.78 to −4.1	<.001
	12 month	−6.48	−7.9 to −5.05	<.001
VEINES QOL Score	Baseline	19.25	10.14 to 28.35	<.001
	1 month	51.88	40.12 to 63.64	<.001
	6 month	50.98	38.72 to 63.24	<.001
	12 month	57.29	44.77 to 69.81	<.001
VEINES Sym Score	Baseline	26.11	15.61 to 36.62	<.001
	1 month	52.11	39.40 to 64.83	<.001
	6 month	42.66	29.37 to 55.94	<.001
	12 month	53.10	39.52 to 66.68	<.001
Calf circumference, cm	Baseline	41.19	37.54 to 44.85	<.001
	24 hours	−4.81	−7.17 to −2.44	<.001
	1 month	−4.63	−7.16 to −2.1	<.001

CI, Confidence interval.

Estimates display average levels at baseline and mean change to each timepoint, adjusting for age, BMI and gender. All Shapiro-Wilk P values were greater than .05, suggesting the Normality assumption for these linear mixed models was valid