Indications, technical aspects, and outcomes of stent placement in chronic iliofemoral venous obstruction

Abstract

Background

Iliofemoral venous stent placement (IVS) has evolved to a well-established endovascular treatment modality for chronic iliofemoral venous obstruction (CIVO). Dedicated venous stents gained approval from the US Food and Drug Administration in 2019 and solidified IVS as a defined intervention with clear indications, contraindications, risks, benefits, and procedural management principles. This review focuses on the indications, technical aspects and outcomes of stenting for CIVO. Other aspects pertaining to IVS are covered in other articles that are a part of this series.

Methods

This study conducted a literature search limited to English articles. Three search strategies were used, and references were managed in Covidence software. Four investigators screened and evaluated articles independently, excluding meta-analyses, clinical trial protocols, and nonrelevant studies. Eligible studies, focused on clinical outcomes and stent patencies, underwent thorough review.

Results

The literature search yielded 1704 studies, with 147 meeting eligibility criteria after screening and evaluation. Exclusions were based on duplicates, irrelevant content, and noniliac vein stent placement.

Conclusions

Successful IVS for CIVO relies on meticulous patient selection, consistent use of intravascular ultrasound examination during procedures and attention to the technical details of IVS.

Iliofemoral venous stent placement (IVS) has progressed remarkably over the past three decades. It has transitioned from off-label stents beginning in the early 1990s to the US Food and Drug Administration (FDA) approval of dedicated venous stents in 2019. Although controversies remain, IVS has overall become a well-delineated intervention with known indications and contraindications, risks and benefits, and general principles of periprocedural management. This review reports on the current state of IVS in patients with symptomatic chronic iliofemoral venous obstruction (CIVO), which represents the most common indication for IVS. The technical aspects of IVS as well as clinical, quality of life (QOL), and stent-related outcomes are evaluated. Recommendations on periprocedural care and follow-up where evidence does exist are provided. We believe this article will serve as a convenient practical guide for physicians considering IVS for patients with CIVO.

CIVOs can be grouped as being nonthrombotic iliac vein lesions (NIVLs), post-thrombotic obstruction, or a combination of the two. NIVLs are a focal obstruction of the common iliac vein, external iliac vein, or both from an external compression. The term nonthrombotic iliac vein lesion encompasses lesions as described by May and Thurner¹ and lesions in other locations as noted by other authors.² Post-thrombotic obstruction as the name suggests is a sequela of a prior episode of deep vein thrombosis (DVT), usually occurring ≥6 months after the index episode of DVT, and the stenosis is typically more diffuse than the focal stenosis observed in NIVL. A history of an acute DVT is not always known to the patient. Both NIVL and post-thrombotic obstruction can be symptomatically silent owing to compensatory mechanisms, with clinical manifestations occurring when such mechanisms become overwhelmed. Symptomatic post-thrombotic obstruction goes by another term, namely, post-thrombotic syndrome (PTS). Given that a NIVL can lead to the development of DVT in the involved extremity and consequent post-thrombotic obstruction, the concomitant presence of NIVL and PTS can be found, although the combination is less common than the individual entities.³

In 2019, Venovo (BD Peripheral Intervention, Tempe, AZ) became the first venous stent approved by the FDA. There are currently three more FDA-approved stents with venous indications: the Venous Wallstent (Boston Scientific, Marlborough, MA), the Abre (Medtronic Vascular, Plymouth, MN), and the Zilver Vena (Cook, Limerick, Ireland). At least two more stents are currently under the FDA review process.

There are several other stents with venous indications in Europe including sinus-Obliquus, sinus-Venous, sinus-XL and sinus-XL Flex (Optimed, Ettlingen, Germany), Blueflow (Plus Medica GmbH, Dusseldorf, Germany), and BeYond (Bentley InnoMed GmbH, Hechingen, Germany).

Increasing awareness, a better understanding of the pathophysiology of CIVO, improvements in diagnosis, and advancements in stent placement technology would likely contribute to the future growth of IVS.

METHODS

The literature search was limited to articles published in English. We used three search strategies to capture original research articles on techniques and outcomes of the iliac vein stent placement published before March 2023 in the PubMed, Embase, Scopus, and the Cochrane library databases. The first search strategy was ((“venous stent”) AND (“iliac vein” OR “Iliofemoral vein”)). The second search strategy was (Venovo OR Vici OR Wallstent OR Zilver OR Abre OR Optimed OR DUO) AND (“iliac vein” OR “iliofemoral vein”)). The third strategy was (“nitinol stent” OR “bare metal stent” OR “elgiloy stent”) AND (“iliac vein” OR “Iliofemoral vein”)). All references obtained from the three search strategies were combined and exported into the Covidence software (Melbourne, Australia). Four investigators (W.T., H.B., P.K., and M.S.) independently screened the titles and abstracts and evaluated the articles for inclusion and exclusion criteria. Meta-analyses, clinical trial protocols, reviews, case reports, editorials, letters, commentaries, and abstracts were excluded. Studies devoted to venous stent placement in the setting of acute venous thrombosis and noniliac vein stent placement were excluded. Articles with the primary end point of clinical, QOL, and/or stent-related outcomes were eligible. All full-text articles were read before final inclusion. Data extraction was performed independently by three investigators (H.B., P.K., and M.S.). Each article was reviewed independently by at least two investigators. Any disagreements were resolved by a third investigator. All variables that were extracted from each study along with the list of studies are noted in Table I.

Table I.

Outcomes after iliac vein stenting

Study	Study design	Indication	Patients	Extremities	Stent(s) used	No. of stents used	Primary patency
							3-Month primary patency	1-Year primary patency	1- to 3-Year primary patency	>3-Year primary patency
Alsheekh et al4	Retrospective	NIVL	844	1216	Wallstent		99.20
Arendt et al5	Retrospective	NIVL	51	51	Wallstent; Other: S.M.A.R.T.	59
Bajwa et al6	Technique	Mixed	112	130	Abre; Venovo; Zilver; Optimed; Other: Vici, Sinus-Venous, XL Flex, Obliquus			88.00
Barbati et al7	Retrospective	PTS	48		Venovo; Other: sinus-Venous, sinus XL venous	281	97.90	77.10	70.00	61.00
Souto Barros et al8	Prospective	Mixed	79	79	Wallstent		95.80	88.50	86.90	85.00
Bi et al9	Retrospective	Mixed	28		Other: Luminexx			93.30
Bondarev S et al10	Retrospective	Mixed	59		Wallstent; Combination of Stents; Other: S.M.A.R.T.
Chait J et al11	Retrospective	NIVL	1645	2004	Wallstent	2681
Dake et al12	Prospective	Mixed	170		Venovo	219	93.50	88.60	84.00
de Wolf et al13	Prospective	Mixed	75		Other: Sinus venous	112	99.00	92.00
Han et al14	Retrospective	NIVL	158	158	Wallstent; Other: E-Luminexx	168
Hays et al15	Retrospective	NIVL	100		Wallstent; Other: Smart Control, Palmaz XL, Zilver SE, Protege	200		87.00
Huang et al16	Retrospective	Mixed	65	65	self-expanding BMS	75	95.60	92.40	90.70
Jayaraj et al17	Technique	Mixed	95		Wallstent; Combination of Stents; Other: Wallstent-Z stent combination	3468				72.00
Jayaraj et al18	Retrospective	PTS	368	368	Wallstent; Zilver	368		78.00
Khairy et al19	Retrospective	Mixed	376		Wallstent; Zilver; Other: Sinus venous, Veniti Vici, Bard Luminex, Sinus Obliquus	620			100.00	80.00
Kibrik et al20	Retrospective	NIVL	192	259	Wallstent	259
Kibrik et al	Retrospective	NIVL	3518		Wallstent
Lakhanpal et al21	Retrospective	Other	82		Venovo, Wallstent	76
Lichtenberg et al22	Retrospective	Mixed	80	86	Venovo	116		98.00
Liu et al23	Retrospective	Mixed	139		Other: Smart Control (nitinol)
Mabud et al24	Retrospective	Mixed	406		WALLSTENT, Wallflex, S.M.A.R.T, Palmaz, Zilver, VIABAHN, Protege, other	1094		83.00	78.90	78.60
Moeri et al25	Retrospective	PTS	150	150	braided and laser cut nitinol stents	390
Montminy et al26	Retrospective	Mixed	152		Other: N/A
Morris et al27	Retrospective	Mixed	207	207	Abre, Wallstent, Vici, Venovo, Zilver	207
Murphy et al28	Prospective	Mixed	200	166	Abre	302		88.00
Neglén et al29	Retrospective	Mixed	94	102	Wallstent	118		82.00
Notten et al30	Prospective	Other	32		N/A
O'Sullivan et al31	Prospective	Mixed	35	35	Zilver	45		85.20
Pappas et al32	Retrospective	NIVL	367		Wallstents
Powell et al33	Retrospective	Mixed	167	167	Wallstent; Venovo	234
Raju et al34	Retrospective	Mixed	292	304	Wallstent	304		97.00	71.00
Raju et al35	Retrospective	Mixed	4026	938	Wallstent	332
Raju et al2	Retrospective	Mixed	1009	1009	Wallstent	1009
Raju et al36	Retrospective	Mixed	504	528	Wallstent	528
Raju et al37	Technique	Mixed	345	345	Wallstent
Raju et al38	Retrospective	Other	274	274	Wallstent	274
Rizvi et al39	Retrospective	NIVL	210	268	Wallstent	268		98.30	97.90
Ruihua et al40	Retrospective	PTS	81	81	Venovo, Wallstent, E-Luminexx	261			81.50
Ruiz et al41	Retrospective	Other	84		Nitinol stent, stainless-steel wall stent and combination	85		72.30
Saleem et al42	Retrospective	Mixed	42	45	Wallstent, zenith stent	45		46.00
Salem et al43	Retrospective	Mixed	58	58	Zilver			91.40		60.30
Sebastian et al44	Retrospective	PTS	136	136	Dedicated venous nitinol stents
Sebastian et al45	Retrospective	PTS	120	120	Wallstents and "dedicated venous stents" but not specified	324
Sebastian et al46	Prospective	PTS	60		Sinus-obliquus, sinus-venous, sinus-XL flex	114
Sebastian et al47	Prospective	Mixed	379	379	Depending on the affected venous segment, the following self-expandable nitinol stents were used: for the IVC, sinus-XL stent or Venovo Venous Stent; for common iliac vein with May-Thurner compression, sinus-Obliquus; for iliac veins or common femoral veins, sinus-XL flex or Zilver Vena Stent or Venovo Venous Stent or Vici Venous Stent or Abre Venous Self-Expandable Stent or Blueflow Venous Stent; for femoral veins, sinusSuperflex or Blueflow Venous Stent. In patients with acute DVT and NIVL	834
Sebastian et al48	Prospective	PTS	60	60	Other: Sinus-Venous hybrid oblique self-expanding nitinol stent	114	93.10	83.00
Shammas et al49	Prospective	Mixed	50	50	Venovo	57		88.30
Slonim et al50	Retrospective	Other	25	25	Wallstent, Palmaz	27
Tran et al51	Retrospective	NIVL	389	389	Wallstent	389
van Vuuren et al52	Retrospective	Mixed	200	200	Sinus-venous stent	415		68.00
Attaran et al53	Retrospective	Mixed	155	155	Wallstent	155
Aurshina et al54	Retrospective	Mixed	1381		Wallstent
Guo et al55	Retrospective	NIVL	838		Wallstent; Other: E-Luminexx				94.40
Gwozdz et al56	Prospective	Other	136	404	Venovo
Hofmann et al57 2023	Prospective	Mixed	243	243	Zilver	365		89.90
Hong et al58	RCT	NIVL	256		Zilver; Other: Venastent
Stuck et al59 2017	Retrospective	Other	93	93	Other: Self-expanding nitinol stents			79.00	72.00
Sulakvelidze et al60	Retrospective	PTS	200	200	Wallstent; Venovo	208
Tang et al61	Prospective	Other	71	71	Venovo; Other: Sinus Obliquus	94	94.60	85.20
Tang et al62	Prospective	NIVL	60	71	Venovo			92.40	87.10
Tosenovsky et al63	Prospective	Other	109	118	Other
Ye et al64	Retrospective	Other	205	224	Wallstent					98.70
Ye et al65	Retrospective	Other	110	118	Wallstent; Zilver; Other: SmartControl, Protege, and Luminexx.				70.00
Yin et al66	Retrospective	PTS	122	122	Other: EverFlex, Lifestent, Wallstent				68.90
Zhang et al67	Retrospective	PTS	154	154	Wallstent
Zhou et al68	Retrospective	Other	127		Wallstent			81.90	70.40
Köksoy et al69	Prospective	NIVL	26		Wallstent
Huang et al70	Retrospective	NIVL	71	105	Venovo, Sinus-Obliquus/Sinus-Venous, Abre			91.00	90.00
Ignatyev et al71	Prospective	Mixed	75		Wallstent
Jayaraj et al17 2019	Retrospective	NIVL	202		Combination of Stents
Kölbel et al72	Retrospective	PTS	59		Wallstent				67.00
Moini et al73	Retrospective	Mixed	188		Sinuous-Venous, Sinuous-Obliquus, Sinuous-XL, Wallstent, S.M.A.R.T.
Ahmed et al74	Retrospective	NIVL	45		Wallstent; Other: S.M.A.R.T.
Le et al75	Retrospective	Mixed	111		Wallstent; Other: S.M.A.R.T.
Liu et al23	Retrospective	NIVL	120		Other
Morris et al27	Retrospective	Mixed	207		Venovo, Zilver Vena, Abre, Veniti Vici
Pappas et al32	Retrospective	NIVL	379		Wallstent
Santoshi et al76	Retrospective	Other	227		Wallstent
Yang et al77	Retrospective	NIVL	50		Other: nitinol stent
Alsheekh et al78	Retrospective	NIVL	173		Wallstent
Li et al79	Retrospective	Mixed	53		Wallstents and E-luminexx Stents			70.80
Lurie et al3	Retrospective	Mixed	462		Wallstent
Murphy et al28	Retrospective	Other	71		Wallstent, Z-stents			59.00	58.00	52.00
Raju et al80	Retrospective	Mixed	1085		n/a
Shiferson et al81	Retrospective	Other	172		Wallstent
Arendt et al5	Retrospective	Other	266		n/a
Ma et al82	Retrospective	Other	n/a		n/a
Murphy et al83	Technique	Mixed		1737	Wallstent; Other: Z-stent
Raju et al36	Retrospective	Mixed		217	Combination of stents				69.00
Snow et al84	Retrospective	Mixed	2673		Abre; Wallstent; Venovo	3116
Jayaraj et al85	Retrospective	Mixed	535		Wallstent; combination of stents; Other: Z stent					70.00
Lichtenberg et al86	Retrospective	Mixed	48		Venovo; Other: sinus-obliquus venous and sinus-venous		98.00	94.00
Nazarian et al87	Retrospective	Mixed	55		Combination of stents			59.00		59.00
Jayaraj et al88	Retrospective	Mixed	578		Wallstent	578				70.00
Lichtenberg et al89	Retrospective	Mixed	80		Venovo
Mandel et al90	Retrospective	NIVL	203		Wallstent	242
Neglén et al91	Retrospective	Other	139		Wallstent	139
Robertson et al92	Prospective	NIVL	161		Wallstent, Venovo, Vici
Tran et al51	Technique	Mixed	150		Wallstent, Vici, Venovo, Protégé EV3, Zilver Vena
Jayaraj et al93	Retrospective	Mixed		464	Wallstent; Other: Z stent
Lichtenberg et al94	Retrospective	Mixed	67		Other: blueflow Venous Stent plus medica			79.80
Marston et al95	Retrospective	PTS	106		Wallstent in 44% of cases; nitinol stents in remainder		74.50	63.90	58.50
Rollo et al96	Retrospective	Other	31		Wallstent; Absolute Pro			66.00
van Vuuren et al97	Prospective	PTS	369	425	Sinus XL, Sinus XL-flex, Sinus Venous, Sinus Obliquus, Vici, Zilver Vena, Venovo
Lin et al98	Retrospective	PTS	87		n/a
Menez et al99	Retrospective	Mixed	95		Zilver, Optimed Sinus Flex XL, Wallstent			74.00
Saleem et al48	Retrospective	Mixed	80	80	Wallstent, Z-stent
Xu et al100	Prospective	Mixed	49	49	Venovo; Zilver	58		93.80
Chait et al101	Technique	NIVL	1061		Wallstent	1513
Coelho et al102	Retrospective	Mixed	367		n/a
Cooke et al103	Retrospective	Mixed	737		Wallstent
Cooke et al104	Retrospective	Mixed	872	1422	Wallstent
de Graaf et al105	Retrospective	Mixed	40	80	Zilver; Other: sinus XL, sinus Venous, sinus XL-flex, AndraStent		100	79	70
de Wolf et al13	Retrospective	Mixed	63	63	Wallstent; Zilver; Other: Sinus-XL, Andrastent XL	194	87.60	74.30
Drabkin et al106	Retrospective	NIVL	30		Wallstent; Other: S.M.A.R.T.	40	89.30	63.90
Endo et al107	Retrospective	Mixed	62		Wallstent; Zilver	65		70.00
Espitia et al108	Retrospective	Mixed	377		Wallstent; Other: Optimed Sinus XL flex, Veniti, Everflex, Venovo, Abre, Zilver Vena, Protege, Covidien				99.30
Gagne et al109	Retrospective	Mixed	67	77	Wallstent	126		100		97
George et al110	Retrospective	Mixed	38	44	Other: Niti stents, E-Luminexx	79			94
Grilli et al111	Retrospective	Mixed	183	212	Other: Protégé	376	94.00	88.60	86.90
Guillen et al112	Retrospective	PTS	52	45	Other: Protege GPS Self-Expanding Peripheral System, Sinus-XL Flex Stent or Sinus Superflex-635				66.70
Gagne et al113	Retrospective	Mixed	100	100	Wallstent	97

DVT, Deep vein thrombosis; IVS, inferior vena cava; N/A, not applicable; NIVL, nonthrombotic iliac vein lesion; PTS, post-thrombotic syndrome; RCT, randomized controlled trial.

Values are percent.

Iliofemoral venous stenting

Indications

Symptomatic CIVO that significantly impairs QOL despite conservative therapy is the primary indicator for intravascular ultrasound (IVUS) interrogation with intent to treat. Edema is the most common clinical manifestation, which also include lower extremity pain, tiredness, heaviness, venous claudication, and venous ulcers. Conservative therapy includes the regular use of compression stockings, leg elevation when feasible, regular walking for exercise as tolerated, and antithrombotic therapy when appropriate. IVS is not indicated in patients who are asymptomatic, minimally symptomatic, or those who are symptomatic but have not attempted conservative therapy.

Evaluation and diagnosis

Diagnosis of CIVO involves the initial use of duplex ultrasound and cross-sectional imaging followed by intraoperative confirmation with IVUS examination. Details pertaining to the diagnosis of CIVO are covered in a separate article that is also a part of this series.

Anesthesia

There is significant variation in the anesthesia used for IVS procedures across practices, ranging from conscious sedation with local anesthesia to general anesthesia. Two recent large series have demonstrated the safety and efficacy of performing these procedures in an outpatient setting.^54,114 During IVS, angioplasty is the procedural component associated with the most pain. There must be sufficient pain control to allow for predilation and postdilation angioplasty to achieve optimal expansion of the stent, which is important in the mitigation of venous hypertension and clinical improvement.

Access

Access for IVS is usually performed with the patient in the supine position. This position is generally better tolerated, often requiring less profound sedation, and affords easier access to an alternative vein if necessary clinically. A prone position is used when popliteal vein access is required. Such access is seldom needed for NIVL lesions, but may be required in acute DVT interventions or when there is a chronic venous occlusion. So, in most cases, femoral access (including both common femoral and femoral veins) is the typical site of access. When there is a concern for disease extension into the common femoral vein, femoral or popliteal vein access may be more suitable, allowing for easier stent placement across the inguinal ligament into the common femoral vein. Introducer sheaths of 9F to 11F diameters are the usual choices in IVS.

Intraoperative anticoagulation

The pre-access or postaccess antithrombotic regimen also demonstrates variability across practices. Often, full heparinization to achieve an activated clotting time of >250 seconds is used, but alternatives like enoxaparin and bivalirudin have also been used.

Venography and IVUS examination

Venography is used as the initial diagnostic tool to visualize the extent and nature of the venous obstruction. Signs of CIVO on venogram may include pancaking of the common iliac vein, prestenotic dilatation, collaterals, contrast thinning and stagnation, and retrograde flow in the internal iliac vein. Venography is followed by the use of IVUS examination for a more detailed and accurate assessment. Several published studies have demonstrated consistently the superior diagnostic precision of IVUS examination over venography.^{26,112,115,116} IVUS examination provides a high-resolution real-time image of the vessel lumen, allowing for precise measurement of the degree of stenosis and assessment of the vessel wall. This level of detail is crucial in guiding the intervention and ensuring optimal stent placement. The most accurate visualization of iliofemoral stenosis is with IVUS examination.^112,117 Venography fails to detect a hemodynamically significant stenosis in one-quarter of limbs¹¹² and misses the exact location of the maximal stenosis in two-thirds of limbs compared with IVUS examination.¹⁰⁹ Venography identified the exact location of the iliocaval junction and the most appropriate location of the landing zone in only 15% and 26% cases, respectively.¹¹² IVUS examination is the gold standard for the diagnosis of CIVO, with venography used to complement it by providing flow-related characteristics, as long as there are no contraindications to the performance of venography.

Historically a luminal area decrease of >50% compared with an adjacent normal vein segment, usually the external iliac vein, or a contralateral segment has been used as the criteria for confirmatory diagnosis of CIVO. However, this technique is fraught with problems owing to the existence of multifocal disease, long segment stenosis (Rokitansky lesion), or bilateral disease. Another commonly accepted diagnostic criterion is a luminal area stenosis of >61% by IVUS examination for NIVL and of >50% for symptomatic post-thrombotic obstruction, which were reported to be a better predictor of symptomatic improvement after IVS.¹⁰⁹ However, more recent data have shown that the concept of 50% stenosis has a limited role in the diagnosis and/or treatment of CIVO owing to a continuous increase in venous pressure with stenosis without a critical stenosis point, as is noted in arterial stenosis.^118,119 These diagnostic challenges can be surmounted with the use of IVUS-determined absolute normal luminal diameter or area (12 mm/125 mm², 14 mm/150 mm² and 16 mm/200 mm² for the common femoral, external iliac, and common iliac veins, respectively) to confirm stenosis and stent correction for values below these absolute numbers. The importance of IVUS examination in the diagnosis and treatment of CIVO should be underscored. In fact, a recent study examining the role of IVUS examination noted that it changed the treatment plan in more than one-half of patients, and in one-quarter of them, more stents were deployed than would have been had venography alone been used.¹¹² Additionally, the use of IVUS examination was found to improve the early and mid-term (3-year) primary patency rates after iliac vein stenting.⁵¹

Stent types

Since the 1990s, IVS has been shown to be safe and effective for treating deep venous obstruction.⁸⁷ There is no evidence that balloon angioplasty alone effectively treats venous obstruction.¹²⁰ All four stents approved by the FDA for treating CIVO have demonstrated high safety and efficacy (Table I).

Abre

The Abre Venous Self-Expanding Stent System (Medtronic, Santa Rosa, CA), approved by the FDA in 2020 for treating iliofemoral venous outflow blockage, is characterized by an open cell design. Designed with a configuration featuring three points of connection between cells, the Abre stent was built to prioritize flexibility and conformity. Additionally, it incorporates a triaxial shaft design, augmenting stent deployment and delivery.¹²⁰ This stent system was evaluated in the ABRE Study by Murphy et al.²⁸ The ABRE Study, a single-arm, multicenter prospective study involving 200 patients, demonstrated that the Abre venous stent effectively addresses symptomatic iliofemoral venous obstruction. Patients exhibited noteworthy improvements in the revised Venous Clinical Severity Score (rVCSS) and Villalta scores, as well as enhancements across QOL measures. The study reported a primary patency rate of 88.0% at the 12-month mark, coupled with a favorable safety profile. Within the 30-day postprocedure window, only four major adverse events (2.0%), were recorded. Over a 12-month follow-up period, no instances of stent fractures or migrations were reported.

Venovo

The Venovo Venous Stent (BD, Franklin Lakes, NJ) is designed for the treatment of iliac and femoral vein obstruction. It received FDA approval in 2019. It is distinguished by its distinctive design that is suited for venous anatomy. It provides flexibility, radial strength, and compression resistance, making it appropriate for both nonthrombotic and post-thrombotic iliac vein lesions. Various studies have shown that the stent's structure adds to its long-term effectiveness and safety. For instance, VERNACULAR was a prospective, nonrandomized, international multicenter single arm study of the Venovo venous stent that led to its FDA approval in 2019. The Venovo stent was effective in the treatment of obstructive iliofemoral vein lesions and met the prespecified primary outcome measures through 12 months. At 3 years, primary patency was 84%, reintervention rates were low, standardized QOL and pain measures improved from baseline, and there was no stent migration or fractures.¹² Lichtenberg et al²² reported that the Venovo venous stent showed satisfactory patency rates associated with reasonable clinical improvement and low device-related complications throughout a 6-months-follow-up in both NIVL and PTS. Over a 6-month follow-up period, the Venovo venous stent demonstrated good patency rates and clinical improvement with few complications in NIVL and PTS.⁸⁹ Primary patency was 98%, whereas secondary patency reached 100% at 6 months.⁸⁹ NIVL limbs had a primary patency rate of 97%, and PTS had a rate of 96%. Stent re-occlusion occurred in three patients at 34, 59, and 156 days after the procedure.⁸⁹ Two of them were treated successfully with endovascular mechanical thrombectomy and stent-in-stent implantation.⁸⁹ Fifty-one percent of cases showed a clinical improvement of ≥2 point in the revised VCSS.⁸⁹ Shammas et al⁴⁹ found that iliac vein stent placement with the Venovo venous stent is effective, with excellent procedural and long-term follow-up, and with symptom improvement in most patients.

Wallstent

The Wallstent (Boston Scientific) is a self-expanding metallic (elgiloy) wire braided stent. The FDA approved the Wallstent in March 2020. This approval broadened the indications for using the Wallstent to widen a constricted segment of the iliofemoral vein. The Wallstent has exhibited its adequacy in venous stenting, with remarkable clinical results and excellent patency rates across multiple studies over the years.^71,121 It is important to note that patients' VCSS and CIVIQ scores show that IVS with Wallstent not only ameliorates symptoms, but also significantly improves their QOL.⁷¹ Gagne et al¹¹³ reported in a retrospective study of 77 limbs who had Wallstent placement for CIVO, the primary patency was 87% and assisted primary patency 95% at 72 months.

Zilver Vena

Cook Medical (Zilver Vena) (Cook Medical, Bloomington, IN) The Zilver Vena Venous Self-Expanding Stent is a flexible, slotted-tube stent built of nitinol (nickel-titanium) that is used to treat symptomatic iliofemoral venous outflow blockage. Its purpose is to exert an outward radial push on the vessel's inner lumen, restoring patency in the stented region. The stent is preloaded in a 2.3-mm (7.0F) delivery catheter. The largest prospective study to date on a dedicated venous stent, the VIVO clinical study, shed light on the safety and effectiveness of Zilver Vena venous stents in treating iliofemoral venous outflow obstruction. After 1 year, the study revealed impressive primary, primary-assisted, and secondary patency rates, highlighting the positive outcomes of Zilver Vena stent placement even more.⁵⁷

Stents available outside the United States

Optimed Sinus-Obliquus venous stent

The Optimed Sinus-Obliquus venous stent (Optimed GMBH) has a hybrid design, featuring a closed cell oblique segment, an open cell design mid-segment, and an anchor ring at the distal end. This unique configuration helps to prevent jailing of the contralateral iliac vein. Clinical trials have demonstrated notable efficacy and a low incidence of device-related complications in both nonthrombotic iliofemoral venous lesions (NIVLs) and PTS cases.^61,62 patients demonstrated significant improvement in Villalta score and VCSS.61, 62, 122 The stent, has exhibited excellent rates of short-term patency for chronic iliac vein compression, including NIVL and post-thrombotic obstruction.

Optimed Sinus-XL venous stent

The Optimed Sinus-XL venous stent (Optimed GMBH) features a closed cell design, providing higher radial resistive force. This stent offers enhanced support while maintaining patency. Clinical evidence suggests a lower occurrence of stent patency loss compared with arterial stents described in the literature.123, 124, 125

Optimed Sinus-XL Flex venous stent

The Optimed Sinus-XL Flex venous stent (Optimed GMBH) is characterized by an open cell design, offering added flexibility. Available in larger diameters, this stent provides a versatile solution. Notably, clinical data suggest a lower incidence of stent patency loss compared with arterial stents described in literature.103, 104, 105

Blueflow venous stent

The Blueflow (Plus Medica GmbH) Venous Stent has a closed cell design that makes it ideal for addressing venous outflow obstructions in the lower limbs. It is a braided stent with flexibility in adapting to the venous anatomy, especially at vital locations such as the inguinal ligament. The Blueflow Venous Stent (Plus Medica GmbH) placement resulted in a significant improvement in VCSS composite scores for 86.1% of patients. Additionally, there was a decrease in the median CEAP classification from 3 (venous edema) to 2 (varicose veins).^25,124,126

BeYond stent

The BeYond stent Bentley InnoMed GmbH is designed with a mix of a closed cell design at the ends and an open cell design throughout¹²⁷

Open vs closed cell design types

The physical properties of a stent, such as dimension, construction material, and stent design, may influence the outcome and complications after the stent placement; some of these factors were highlighted in the research of Dabir et al.¹²⁸ The Abre, Venovo, and Zilver Vena are open-cell nitinol stents, whereas the Wallstent is a closed cell stent made of elgiloy. Interestingly, in NIVL cases, where the compression is between an artery and bone, both open cell and closed cell venous stents seem to perform equally well in patency and symptom improvement after 1 year.¹²⁸ Notably, instances of stent fracture were infrequent, underscoring the robust performance of both design types.

Stent selection and stent placement

Technique of stenting

After IVUS confirmation, vein stent placement consists of several important steps to achieve an optimal outcome. Predilation, stent placement, postdilatation, completion IVUS examination, and venography make up these steps.

Balloon sizing and predilation

Assessing the appropriate angioplasty balloon diameter is the opening act of predilation. This metric is typically guided by the size of the stent to be used. Predilation serves to create an adequate channel to allow for adequate stent expansion after deployment. If this factor is not pursued routinely, it is possible that even after postdilation, some stents may not fully expand to the expected size, resulting in residual venous hypertension.

Stent sizing and deployment

The goal of stenting is to exclude all areas of stenosis; the stent should extend from an area of good inflow to an area of good outflow. Selecting an appropriately sized stent is discussed in a previous article. One approach is to use the inflow channel lumen area. This dimension is estimated using IVUS examination and represents the luminal area of the native vein just below the anticipated termination of the stent. This measurement determines the size of the caudal stent, with the cranial stent being approximately 2 mm larger. When multiple stents are used, it is imperative to ensure adequate overlap of the two stents to prevent shelving and angulation of the two stents. This overlap is usually about 2 to 3 cm. The angioplasty balloon is typically the size of the caudal stent. Managing the inferior vena cava (IVC) confluence when the stenosis is at or close to the confluence can be challenging. The stent is extended into the IVC with the least distance possible, but no more than several millimeters into the IVC. For the Wallstent, a supplemental Z stent can be used to overcome the iliocaval confluence choke point effect.¹⁸

Postdilation

This process expands the stent to its rated luminal area/diameter, thereby correcting the stenosis and mitigating the venous hypertension as a result of the stenosis. This procedure is typically done with the same angioplasty balloon used for predilation. If there is residual stent compression on the completion IVUS, then a larger angioplasty balloon may have to be used to ensure that the stent is expanded fully.

Completion IVUS examination and venogram

Whereas the completion IVUS examination helps to ensure the adequacy of stenting, the completion venogram helps to characterize flow parameters across the deployed stent. The latter can be skipped if there are contraindications to venography.

Simultaneous bilateral stenting

There is no role for routine bilateral vein stent placement, and this decision should be guided by the specifics of each case. One report of patients with bilateral symptoms noted that there was symptomatic improvement in both legs with correction of the obstruction only in the more symptomatic leg in 95% of patients and that only 5% of patients required a contralateral stent over a median follow-up of 20 months.⁸⁸

Residual symptoms after stenting

In patients with QOL -impairing residual leg edema and other venous-like symptoms after stenting, an evaluation of superficial venous disease may be beneficial. Recent reports also suggested that complex decongestive therapy can be of help. In one study of the 118 limbs with CEAP clinical class C4 to C6 disease, 43 (36%) required complex decongestive therapy after stenting for persistent QoL-impairing symptoms with improvement following such therapy.

Postprocedure antithrombotic therapy

Antithrombotic therapy is an important consideration in postoperative management, and which may influence patient outcomes and stent patency. To date, no prospective study has addressed this issue. Not surprisingly, the approach to antithrombotic therapy varies widely, encompassing from no therapy to the use of a single antiplatelet agent or anticoagulation, as well as combinations thereof. Given that there is no consensus on the use of antithrombotic agents, the following represent general guidelines.

Antithrombotic therapy for NIVLs

In general patients undergoing stenting for NIVL do not require anticoagulation. Exceptions to this include, patients already on anticoagulation pre procedure, in those with a history of unprovoked VTE or thrombophilia, in patients on hormonal therapy, or in instances of early severe in-stent restenosis (ISR) on post procedure duplex ultrasound. Otherwise, aspirin 81 mg alone is adequate on a long-term basis.

Antithrombotic therapy for post-thrombotic obstruction

For patients undergoing stenting with post-thrombotic obstruction, anticoagulation for 3-4 months is generally recommended till endothelialization of the stent occurs which may take 8-12 weeks. Exceptions to this would include situations noted above. Here again ASA 81 mg is occasionally used alongside the anticoagulation and may be continued long-term (Table II).

Table II.

Anticoagulation strategies

First author and year	Postoperative antithrombotic medication	Overall duration of anticoagulation, months	Postoperative antithrombotic classification
Alsheekh et al4 2020	Clopidogrel (Plavix)	≥3 months	Antiplatelets
Arendt et al5 2021	Warfarin and rivaroxaban	1 month to ≥12 months	DOACs and VKA
Baccellieri et al129 2021	Unspecified anticoagulation	2 weeks to 12 months	DOACs
Bajwa et al6 2019	Warfarin	3 month to ≥12 months	VKA
Barbati et al7 2020	Rivaroxaban	9-21 months	DOACs
Bi et al9 2019	Warfarin or dipyramidole	3-6 months	VKA and AP
Binkert et al130 1998	Acenocoumarol	6-12 months	VKA
Dake et al12 2021	Acetylsalicylic acid, clopidogrel, rivaroxaban, apixaban	Unspecified	DOACs and AP
deWolf et al13 2015	Coumadin	6 months	VKA
Han et al14 2022	Unspecified anticoagulation	Unspecified
Hays et al15 2021	Apixaban, rivaroxaban and dabigataran, warfarin, clopidogrel, aspirin	1 month - 3 month	DOACs, VKA and AP
Hoshino et al131 2023	Unspecified antiplatelets and anticoagulant	1 month to ≥12 months
Huang et al16 2018	Warfarin	≥12 months	VKA
Jayaraj et al17 2019	DOACs, aspirin, cilostazol		DOACs and AP
Jayaraj et al18 2020	DOACs, warfarin, cilostazol and aspirin	1-6 months	DOACs, VKA and AP
Jayaraj et al18 2021	DOACs, warfarin, cilostazol and aspirin	6 months	DOACs, VKA and AP
Khairy et al19 2017	Coumarin and clopidogrel	6-12 months	VKA and AP
Kibrik et al20 2018	Clopidogrel and aspirin	3 months	Antiplatelets
Kibrik et al132 2022	Clopidogrel and Aspirin	3 months	Antiplatelets
Lakhanpal et al21 2021
Lamont et al133 2002	Warfarin	6 months	VKA
Lichtenberg et al134 2020	VKA or DOACs	6-12 months	DOACs and VKA
Mabud et al24 2020	Warfarin or rivaroxiban (or other DOACs)	Unspecified	DOACs and VKA
Moeri et al25 2020	Rivaroxaban, apixaban	Unspecified	DOACs
Montminy et al26 2019
Morris et al27 2021	Warfarin, rivaroxaban, apixaban	2 weeks-6 months	DOACs and VKA
Murphy et al28 2022	Warfarin, DOACs, antiplatelet	6-12 months	DOACs and AP
Neglen et al29 2000	Aspirin (± anticoagulants)	Indefinitely	VKA
O'Sullivan et al31 2013	Warfarin	3 months to ≥12 months	VKA
O'Sullivan et al135 2021	Unspecified anticoagulation	6 months
Pappas et al32 2022	Rivaroxaban, apixaban, N-acetylcysteine	3 months	DOACs and AP
Powell et al33 2023	DOACs, aspirin	Unspecified	DOACs and AP
Raju et al136 2002	Aspirin and warfarin	Unspecified	VKA and AP
Raju et al34 2008	Aspirin and warfarin	Unspecified	VKA and AP
Raju et al137 2019	Aspirin and cilostazol	Unspecified	Antiplatelets
Rizvi et al39 2018	Clopidogrel	3 months	Antiplatelets
Ruihua et al40 2017	Warfarin	6 months to ≥12 months	VKA
Ruiz et al41 2023	Warfarin, DOACs, ASA, clopidogrel	2 weeks - 6 months	DOACs, VKA and AP
Saleem et al42 2022	Aspirin, apixaban, rivaroxiban and cilostazol	≥12 months	DOACs and AP
Salem et al43 2022	Clopidogrel and DOACs	3-6 months	DOACs and AP
Sebastian et al44 2019	VKA or DOACs	3 months	DOACs and VKA
Sebastian et al45 2020	VKA or DOACs, ASA or clopidogrel	3 months	DOACs, VKA and AP
Sebastian et al47 2020	Unspecified anticoagulants	3-12 months
Sebastian et al48 2021	DOACs, VKA and antiplatelets	6-12 months	DOACs, VKA and AP
Tran et al138 2020	Aspirin, clopidogrel, rivaroxiban, apixaban	3 months	DOACs and AP
vanVuuren et al139 2018	Warfarin	6 months	VKA
Attaran et al53 2019	ASA, clopidogrel, VKA, DOACs	3 months to ≥12 months	DOACs, VKA and AP
Aurshina et al54 2020	Clopidogrel	3 months	Antiplatelets
Gavrilov et al140 2020	Clopidogrel	3 months	Antiplatelets
Guo et al55 2020	Warfarin	6 months	VKA
Gwozdz et al56 2021	Warfarin, DOACs	6 months to ≥12 months	DOACs and VKA
Hofmann et al57 2023	Unspecified anticoagulants and antiplatelet	6 months to 12 months
Hong et al58 2022	Rivaroxiban	3 months	DOACs
Korff et al141 2022	DOACs, warfarin, aspirin	Unspecified	DOACs, VKA and AP
Stuck et al59 2017	Rivaroxiban and VKA	3 months to ≥12 months	DOACs and VKA
Stuck et al142 2018	Rivaroxiban and VKA	3 months to ≥12 months	DOACs and VKA
Sulakvelidze et al60 2023	Rivaroxiban and apixaban, clopidogrel, dabigitran, ASA	3 months	DOACs and AP
Tang et al61 2021	Warfarin and DOACs, clopidogrel, Rivaroxiban	Unspecified	DOACs, VKA and AP
Ye et al65 2014	Warfarin	6 months to ≥12 months	VKA
Yin et al66 2015	Warfarin	6 months to ≥12 months	VKA
Zhang et al67 2021	Rivaroxiban, warfarin	12 months	DOACs and VKA
Zhou et al68 2021	Warfarin, rivaroxiban	12 months	DOACs and VKA
Kusiak et al143 2019
Koksoy et al69 2018	Warfarin	6 months	VKA
Langwieser et al144 2016	Rivaroxaban, clopidogrel	6 months	DOACs and AP
Huang et al70 2021	Rivaroxaban, clopidogrel	3 months to ≥12 months	DOACs and AP
Ignatyev et al71 2019	Warfarin or rivaroxaban, ASA	6 months	DOACs, VKA and AP
Jayaraj et al17 2019	DOACs, ASA, cilostazol	1.5 - 6 months	DOACs and AP
Kolbel et al72 2009	Warfarin	6 months to ≥12 months	VKA
Moini et al73 2020	Warfarin	unspecified	VKA
Ahmed et al74 2016	LMWH	2 weeks
Le et al75 2018	Warfarin, rivaroxaban, ASA, clopidogrel	6 months to ≥12 months	DOACs, VKA and AP
Morris et al27 2022	Warfarin, DOACs	6 months to ≥12 months	DOACs and VKA
Yang et al77 2021	Rivaroxiban	3-12 months	DOACs
Li et al79 2023	Rivaroxiban, warfarin	Unspecified	DOACs and VKA
Shiferson et al81 2019	Clopidogrel	3 months	Antiplatelets
Murphy et al145 2017	Aspirin, unspecified anticoagulation	≥12 months
Raju et al36 2014	Aspirin	1.5 months to ≥12 months	Antiplatelets
Jayaraj et al85 2021	DOAC, warfarin, cilostazol, aspirin	≥12 months	DOACs, VKA and AP
Lichtenberg et al86 2019	DOACs,	6-12 months	DOACs
Maleux et al146 2016	LMWH	1 month
Nazarian et al87 1996	Warfarin	3-6 months	VKA
Speranza et al147 2022	Aspirin	Unspecified	Antiplatelets
Jayaraj et al148 2022	DOAC or warfarin, cilostazol, aspirin	6 months to ≥12 months	DOACs, VKA and AP
Lichtenberg et al89 2020	VKA	6-12 months	VKA
Mandel et al90 2018	Clopidogrel	3 months	Antiplatelets
Neglen et al149 2000	Aspirin	≥12 months	Antiplatelets
Robertson et al92 2023	Apixaban or rivaroxiban, clopidogrel	6 months	DOACs and AP
Jayaraj et al150 2022	Aspirin, cilostazol, DOAC, or warfarin	6 months	DOACs, VKA and AP
Marston et al95 2021	Warfarin, factor Xa inhibitor	10 days – 1 month	DOACs and VKA
Rollo et al96 2017	Clopidogrel, aspirin, DOACs	Unspecified	DOACs and AP
van Vuuren et al97 2017	VKA	6 months	VKA
Juhan et al151 2001	VKA	6 months	VKA
Lin et al98 2020	Rivaroxaban, apixaban, warfarin, clopidogrel and aspirin	3 months to ≥12 months	DOACs, VKA and AP
Menez et al99 2019	Aspirin, warfarin or DOACs	3-6 months	DOACs, VKA and AP
Pappas et al32 2022	LMWH	Unspecified
Xu et al100 2021	Rivaroxiban, aspirin	6 months to ≥12 months	DOACs and AP
Chait et al11 2020	Clopidogrel	3 months	Antiplatelets
Chait et al101 2022	Rivaroxiban, aspirin	Unspecified	DOACs and AP
Chen et al152 2019	Aspirin	12 months	Antiplatelets
Cooke et al103 2022	Rivaroxiban, aspirin	3 months to ≥12 months	DOACs and AP
Daugherty et al153 2015	Aspirin, clopidogrel, warfarin	1 month to ≥12 months	VKA and AP
deGraaf et al105 2015	Warfarin	6 months	VKA
DeWolf et al154 2013	Acenocoumarol or phenprocoumon	6 months	VKA
Drabkin et al106 2021	Apixaban, rivaroxiban, warfarin, Aspirin	Unspecified	DOACs, VKA and AP
Endo et al107 2018	Warfarin	Unspecified	VKA
Espitia et al108 2023	Aspirin, clopidogrel, DOACs	3 months to ≥12 months	DOACs and AP
Gagne et al113 2019	Clopidogrel, aspirin, unspecified anticoagulants	6 months to ≥12 months
George et al110 2014	Warfarin	Unspecified	VKA
Grilli et al111 2021	DOACs, clopidogrel, aspirin	≥1 month	DOACs and AP
Guillen et al155 2020	VKA, DOACs, aspegic	2 months	DOACs, VKA and AP
Gutzeit et al121 2011	Warfarin	6 months	VKA

AP, Antiplatelet; DOAC, direct oral anticoagulant; LMWH, low-molecular-weight heparin; VKA, vitamin K agonist.

Complications

Major complications are uncommon following IVS for CIVO. Acute low back pain, which is more of a procedural sequelae than complication, occurs in almost every patient after IVS, usually lasting 1 to 2 weeks but sometimes up to several weeks in duration, and typically of sufficient severity to require analgesic for relief.156, 157, 158 A large retrospective study found no difference between Wallstents, Venovo, and Abre stents in postoperative back pain.⁸⁴ Bleeding and hematoma can occur after the IVS procedure, typically at the vascular access site, and which can almost always be controlled with compression alone and rarely requires exploration. Attention to hemostasis and vigilant post-procedural monitoring will decrease these bleeding events.¹⁵⁷

Stent embolization is a serious complication in IVS for CIVO. While potentially preventable and uncommon, stent embolization has continued to occur after IVS. Improper stent sizing is the single most important factor responsible for stent migration.¹⁵⁹ One report identified length of stents less than 60 mm and stent diameter of 14 mm or less were associated with this complication, underscoring the importance of correct stent sizing during IVS.¹⁶⁰

Another serious complication following IVS is acute stent thrombosis. The diagnosis is suspected when a patient presents with sudden leg pain and swelling after IVS and mandates urgent attention. Duplex US and CTV may help with clinical confirmation. Stent patency can usually be restored with catheter thrombolysis, mechanical thrombectomy, balloon angioplasty, and if clinically indicated, stent placement. The majority of early stent thrombosis are due to technical difficulties such as residual stenosis, kinking, or angulation.¹¹³ A subgroup study from the Swiss Venous Stent registry revealed that IVS for PTS, stent placement in the common femoral vein, and post-thrombotic disease of the inflow veins are linked with a greater risk of stent thrombosis.⁴⁴

Follow-up

Follow-up post stenting is generally lifelong. The post-procedural follow-up typically includes clinical and QOL assessments with Duplex US of the stent at specific intervals. Clinical assessment generally includes the VCSS. QOL assessment is through the CIVIQ 14 or CIVIQ 20 instrument or the VEINES QoL assessment. Such follow-up is generally pursued within 4 weeks post stent placement, then at 3-, 6- and 12-months post intervention and then yearly. Closer follow-up may be required in the setting of concern for clinical recurrence and/or stent malfunction.

With regards to metrics used to evaluate the stent with Duplex US, one report suggested combination of peak flow velocity >10 cm/s and the presence of respiratory phasicity may rule out 94% of in-stent obstructions.⁴⁵ Flow channel diameters on Duplex US can also be used to assess for stent compression or in-stent restenosis or both.^18,148 Additionally, stent occlusion can also be diagnosed on Duplex US.¹⁷ Recent data has shown that a contrast-enhanced Duplex US has a higher sensitivity and specificity compared with standard Duplex US.¹⁶¹ Duplex US demonstrated good agreement with computed tomography venography to detect in-stent restenosis. In symptomatic patients CTV can be used together with Duplex US. An early report demonstrated that automated quantitative imaging can be used to detect CTV changes in the water content of fat-containing tissues, which may become an objective measurement of edema resolution after IVS.¹⁶²

Clinical outcomes

Overall, IVS is a low morbid procedure¹⁴⁹ that is most commonly performed as an outpatient procedure.²⁰ IVS in CIVO has high technical success rates,^10,129 excellent symptom relief,^28,57 and durable long-term patency.^22,113,43 The immediate (within 3 months), short-term (1 year), intermediate (1-3 years), and long-term (>3 years) primary patency rates after IVS are reported in Table I. Only one underpowered retrospective study with a significant selection bias failed to demonstrate benefits of IVS compared with conservative management.⁸¹ This anecdotal evidence should not abolish several decades of experience and the results of many other studies reporting favorable outcomes after IVS that is usually undertaken in patients who fail conservative treatment. Across a 10-year period, 13% of patients require re-intervention to correct new or previously missed inflow, outflow, or in-stent defects found on routine surveillance or target workup for residual or recurrent symptoms of CVI.³⁴ Clinical improvement is achieved in more than two-thirds of patients at 12 to 18 months in these cases. Primary patency rates vary across different indications with NIVL having the best outcomes. Multiple stents used and presence of PTS were associated with less favorable outcomes with lower long-term patency.⁴⁵ The severity of stenosis is also correlated with outcomes. Patients with iliofemoral occlusion have the lowest primary patency rates (<80% in 3 years).^12,34,95 One study suggested female gender may be associated with superior outcomes after the IVS.⁷⁴ Owing to the lack of data on the IVS outcomes 10 years and beyond, younger individuals should have a higher threshold for IVS in CIVO.

QoL outcomes

QoL should be routinely assessed since the fundamental purpose of the IVS procedure for CIVO is improving a person's QOL. Multiple studies have shown improvement in a patient's QOL after IVS.^{8,13,28,49,57,59,71,89,95,113}

Stent patency

Venous stents have generally exhibited superior performance. For instance, a secondary patency rate of approximately 90% has been consistently reported in the literature for NIVL lesions treated with Wallstent. Additionally, studies have indicated that patency rates for nonocclusive and occlusive PTS are around 80% and 70% respectively.^17,37 In a recent study published, a secondary patency of 90% was observed in patients with NIVL, reinforcing the robust performance of venous stents. Similarly, previous studies have reported comparable patency rates.¹⁸

Although the majority of studies support favorable venous stent patency, it is crucial to acknowledge that there are instances where patency rates have been reported lower than expected. These anomalies, as shown in Table I, underscore the importance of considering various factors that may influence stent performance.

A clear picture of patients' venous health emerges following IVS through examination of clinical outcomes. Numerous studies have shown clinical improvements in VCSS, Villalta, CEAP and CIVIQ-20 scores, along with excellent symptom improvement.^{28,49,57,59,71,89,95}

Reinterventions

Reinterventions should only be pursued in patients with QOL-impairing recurrence of symptoms. It should not be pursued for a given amount of ISR and/or stent compression, because these conditions have not been found to be an indicator for recurrence of symptoms.¹⁴⁸

ISR

ISR is a recurring stenosis within the implanted stent. Saleem and Raju¹⁶³ observed ISR was as high as 74% by 3 months, but stabilized thereafter. This study suggested that the stent inflow luminal area and shear rate were significant risk factors for ISR.¹⁶³ To address ISR, many procedures have been used, including balloon angioplasty with or without cutting and the possible use of medicines coated onto balloons or stents.

Stent compression

External factors cause stent compression. Saleem and Raju¹⁶³ suggested that stent compression was associated with asymmetric stent sizing. To address stent compression, measures such as adding more stents, lengthening existing ones, or using custom stent types may be used. These strategies may enhance stent functionality and alleviate pressure-related issues.

DISCUSSION

Despite extensive literature, the precise prevalence of CIVO is not yet established clearly. Research, initiated by pioneers like Ehrich and Krumbhaar,¹⁶⁴ Negus et al,¹⁶⁵ May and Thurner,¹ and, more recently, Kibbe et al,¹⁶⁶ has expanded our understanding of CIVO significantly. The diagnosis of an iliofemoral stenosis across modalities such as physical examination, ultrasound examination, computed tomography scan, magnetic resonance imaging, and venography is imprecise. IVUS examination is highly accurate in the diagnosis of CIVO, but it is an invasive procedure and the use of IVUS examination is not universal.

Individuals with CIVO, despite conservative care, endure persistent edema and other venous-like symptoms that can significantly impact their QOL. This condition is the primary indication for IVS. Occasionally, preoperative imaging is negative for CIVO, and, in these symptomatic patients, IVUS examination with intent to treat may be appropriate if CIVO is confirmed intraoperatively.

The pivotal role of IVUS examination during IVS is reinforced during this review. IVUS examination not only precisely determines the severity and exact location of the stenosis, but also assists with stent selection and guides the precise placement of the stent.

There are currently several stents approved for venous indications. Reports reviewed during this study showed that these stents, with different physical characteristics, had excellent outcomes after IVS. Although these reports point to the availability of several excellent stents at the present time, they also underscored the importance of the proper patient selection, standardized implantation techniques, and careful follow-ups that are required components of these prospective trials.

This review suggested critical knowledge gaps in IVS for CIVO. One example is optimal pharmacological therapy after IVS in CIVO. Another is why some patients with CIVO become symptomatic, whereas others do not. The relationships of CIVO with superficial venous disease, deep vein reflux, acute DVT, and PTS remain poorly understood.

Limitations

There are numerous limitations to this review that could limit the generalizability of our findings and conclusions. There is significant heterogeneity in study designs and outcome reporting of the studies reviewed. Most of the literature on IVS in CIVO was retrospective, with only a few prospective studies and just two randomized controlled trials.^167,168 The presence of superficial venous disease, deep vein reflux, and prior DVT was not specified clearly in some studies, and these concurrent venous pathologies, if present, might have impacted the outcomes. The number of stents and the number of extremities in which stents were placed were not reported consistently. It is frequently difficult to determine whether IVS was undertaken with a unilateral or bilateral approach, which could also affect the outcome. Heterogeneity was also present in terms of the practice setting, such as an outpatient surgery center vs a hospital. Although most studies on IVS were performed in the United States, some were conducted in nations across the globe from Germany to Iran to Japan, representing a diversity of stent types, patient demographics, and practice patterns. As we found in our own research and practice, race and ethnicity have a significant impact on outcomes after IVS.^169,170 There was nonuniformity in postoperative pharmacological strategies, and postoperative care and surveillance. Preoperative medical management in many studies was not well-described. Follow-up of patients was not reported consistently. Many studies did not report the percentage of patients who were followed at each follow-up period, resulting in possible attrition bias. Although IVUS is important during IVS, the extent of IVUS use in some studies was not described fully.^{26,51,109,112,171} Despite these limitations, review of these many published reports provided important clinical insights of IVS among these CIVO patients.

CONCLUSIONS

There are currently several excellent stents approved with venous indications. Salutary outcomes from IVS for CIVO can be achieved with proper patient selection, routine use of IVUS during IVS, attention to the technical details of IVS, and close follow-up postoperatively.

Author Contributions

Conception and design: HB, PK, MES, WT

Analysis and interpretation: HB, PK

Data collection: HB, PK, MSi

Writing the article: HB, PK, MES, MSi, WT

Critical revision of the article: HB, PK, MES, MSi, WT

Final approval of the article: HB, PK, MES, MSi, WT

Statistical analysis: HB

Obtained funding: Not applicable

Overall responsibility: WT

Disclosures

None.