Moderator: Dr. Ronald S. Winokur
Experts: Dr. Stephen Black, Dr. Kush Desai, Dr. Erin Murphy
Iliac vein recanalization and stenting have increased in utilization, but specific challenges should be considered to optimize clinical outcomes and prevent serious complications. To help guide decision-making, this group of experts will address essential considerations such as stent migration, stent fracture, and stent thrombosis. Additional considerations related to the differences between non- thrombotic iliac vein lesions (NIVL), acute deep vein thrombosis, and post-thrombotic venous reconstruction will be addressed.
Will you perform venous recanalization and iliac vein stenting procedures in patients with poor inflow from post-thrombotic change in the femoropopliteal segment? What if both the femoropopliteal and profunda femoral vein are post-thrombotic?
Dr. Kush Desai: Evaluation and sub-stratification of the quality of the inflow remains one of the most important elements of planning a deep venous intervention, particularly in post-thrombotics, and one of the most fraught with variability. Though various classification systems are in place, they are all subjective. We are sorely in need of an objective metric to evaluate inflow, helping us determine which patients will have a durable result following recanalization.
With our current level of understanding, I tend to focus on the profunda femoris vein. I believe this is the key determinant to achieving durable stent patency. Certainly, a good quality femoral inflow can be helpful, but it is not necessary, as I have several patients that have patent stents solely relying upon the profunda. However, if the profunda is post-thrombotic, regardless of the status of the femoral vein, my feeling is that such patients have poorer long-term patency.
Dr. Stephen Black: I think that poor inflow is the single biggest cause of the failure of stents in modern practice; therefore, I try and avoid it if I can. The Catch-22 is that these patients are often the ones with the worst symptoms, and therefore I do end up needing to treat on occasion. If I do, the patients need to be fully prepared for the potential for failure and a significant chance of needing multiple re-interventions to maintain stent patency. This can be quite demoralizing for both patient and physician. We still do not have great answers for poor inflow.
ACCESS PTS (Mark Garcia) showed promise, but we have not been able to replicate these results in our practice consistently. Endophlebectomy and fistula remains challenging and often morbid operation.
Therefore, in patients with both profunda and femoral vein involvement you really have to have significant symptoms to justify intervention given the high chance of failure.
Dr. Erin Murphy: Inflow disease often accompanies post-thrombotic iliac vein occlusive disease and is the primary cause of stent failure in post-thrombotic patients. In my practice, I routinely evaluate the femoral and profunda inflow vessels prior to stenting with ultrasound. Isolated post-thrombotic changes in the femoral vein are often tolerable without limiting stent candidacy.
Profunda inflow disease is more concerning and is rarely seen in isolation. Instead, profunda disease is often a marker for two-vessel inflow disease, which portends a guarded stent prognosis. Severe two-vessel inflow disease is a contraindication for stenting unless patients are candidates for endophlebectomy. Less severe disease may be manageable in experienced centers with caution.
What procedural modifications do you implement if you perform procedures in these patients with poor inflow? Will you change your anticoagulation regimen post-procedure?
Dr. Desai: Mostly, it is about patient selection. I tend to start all post-thrombotic patients on low molecular weight heparin before intervention. If I find myself in a situation where I underestimated the degree of profunda femoris disease in my pre-procedural evaluation, I will attempt to improve it with angioplasty. Only in situations where I can restore reasonable inflow from the profunda would I proceed to placing a stent.
Dr. Black: In patients with poor inflow, you have to focus on being really tight technically to preserve the inflow from the profunda in particular. Often this requires early repeat venoplasty of the inflow vessels to support patency. In these patients, very focused early ultrasound surveillance can allow targeted re-intervention. Anticoagulation is crucial, and mostly that the patient understands they have to be compliant. We don’t specifically alter what we give them but are very clear that re-intervention, especially in the first six weeks, is likely. I have found that in a good cohort, if you do early repeat venoplasty they can settle down as the inflow improves.
Having said all this, given we have no clear test for what could be described as adequate I still get surprised by some patients who block with what on paper is great inflow and others who stay open despite having horrible looking vessels.
Overall though, we know that whatever you do, it is hard to compensate for genuinely poor inflow.
Dr. Murphy: Isolated inflow disease in the common femoral vein can almost always be treated by landing stents precisely at the femoral-profunda confluence under IVUS guidance. It is important to confirm that no tissue flaps remain over the confluence post-stenting. Venoplasty may be used for post-thrombotic scarring in the femoral vein with variable results. At times, I will additionally perform venoplasty of the origin of the profunda vein. It should be acknowledged that venoplasty is an adjunct procedure to improve inflow potentially but is not a reliable means to convert a patient with inadequate inflow into an operative candidate.
If inflow disease is severe but limited to the CFV and profunda-femoral confluence, an endophlebectomy may be warranted in combination with stenting to achieve desired results.
In all circumstances, post-thrombotic inflow disease, whether occlusive or non- occlusive, is a considerable risk factor for future stent occlusion. In my practice, these patients are kept on indefinite anticoagulation.
What is your strategy to optimize the placement of stents intraprocedurally? Do you use specific anatomic landmarks or provide a standard distance from the point of maximal compression identified on intravascular ultrasound (IVUS)?
Dr. Desai: Optimization of stent placement is a matter of using IVUS and fluoroscopy/venography in a coordinated manner. Using IVUS, I identify my landing zones, along with the anatomy that I want to avoid stenting across (confluence of the iliacs, profunda femoris inflow). I then use the markers on IVUS to fluoroscopically plan my stent placement; in the case of a complete obstruction from the profunda to the confluence, I will plan to have the iliac stent end in the caudal external iliac vein, have my stent junction above the inguinal ligament/within the pelvis, and terminate the common femoral stent just above the dominant profunda inflow. In my view, it really is about using your imaging techniques in a coordinated, complementary way.
Dr. Black: Elimination of technical errors during stent placement is a combination of detailed pre-operative imaging (Duplex and MRV) and intraoperative IVUS. The combination of IVUS with consistent bony landmarks to provide a sense check helps ensure you eliminate the two most common technical causes of stent failure – those being missed inflow or missed outflow disease. Gerry O’Sullivan published a nice paper (“Aiming for the Bottom Corner: How to Score a Field Goal When Landing Venous Stents in May-Thurner Syndrome”) describing the consistent bony landmarks that you should be aware of – the spinous processes in full AP are a very consistent marker for the confluence of the common iliac veins, and the lesser trochanter for the confluence of the femoral and profunda veins.
Dr. Murphy: I utilize IVUS to guide all intraprocedural decisions, including the precise identification of the profunda-femoral confluence, determination of a healthy stent landing zone above this point, and precise identification of the iliac confluence. Venography is an adjunctive imaging technique but lacking in precision. While some interventionalists utilize the lesser trochanter as a marker for the profunda vein, the profunda can come in higher than this point. If multiple vessels are seen joining/leaving the CFV at the level of the confluence, review of pre-operative ultrasound as well as selective venography of the profunda can be confirmatory. It is essential to protect the profunda as coverage of the profunda orifice may result in eventual unsalvageable stent occlusion.
Conversely, landing too high in a diseased CFV risks leaving septations between the stent edge and the profunda. CFV disease below the stent, even if not perceived to be flow-limiting, can also result in stent thrombosis in a low-pressure system.
At the iliac confluence, precise identification can limit jailing of the contralateral vein and limit missed cranial disease. Stents must land just cranial to any compression points, often just into but not across the confluence. When disease is limited to the CIV, as in many non-thrombotic patients, I routinely take stents into the straight part of the external iliac vein caudally.
What strategies do you implement to prevent against stent migration or stent fracture complications? Are there specific stent placement locations that you avoid?
Dr. Desai: Stent migration is a problem that seems to occur, thus far, only in treatment of non-thrombotic iliac vein lesions. Avoiding stent migration is a matter of proper patient selection (i.e. symptoms that we can reasonably expect to resolve with an iliac vein stent, as well as a lesion that fixed and of clear significance), sizing per device guidelines (i.e. slight oversizing with respect to the normal reference vessel), and using stents of sufficient length to extend around the curve of the iliac vein. A recently published systematic review found short stents that were less than 14 mm in size tended to migrate. In general, if we select patients that truly need a stent and follow the above sizing/ length guidance, migration should be minimized.
With respect to fracture, there is recent work to suggest that the ligament is not the cause; rather, it is the pubic ramus. Further, stent fracture appears to occur in extension, not flexion. Certainly, there is more to come on this, but there are device designs on the market currently tested with the intent to minimize fracture. In general, I avoid any stent joints below the ligament; I try to confine them to the pelvis. This is because stent joints can be a point of mechanical failure/distraction of stents with motion.
Dr. Black: Stent migration – as we have shown in a recently published review – is really a factor of undersizing stents.1 In particular short stents (60 mm or less) and small diameter (14mm or less) are the greatest risk. I avoid this by virtually always anchoring the stent in the external iliac vein (i.e. going round the bend in the pelvis) and typically never use less than a 120mm stent. Migration is really a major risk in NIVL patients and so this is the group to take particular care. First and foremost by only treating patients who actually need a stent and secondly making sure you have a properly sized and well anchored stent.
Stent fracture appears to be largely a problem for closed-cell stents and is reported extremely infrequently in open-cell or woven stents. However, the most common area to see fractures was adjacent to the femoral head just beneath the ligament. It is very important to avoid stent overlap in these areas, and therefore if I do extend the stent below the ligament, I make sure that I have the stent overlap sitting above the ligament in the EIV.
Dr. Murphy: Stent migration is almost exclusively seen in patients undergoing stenting for non- thrombotic disease. Further, it is associated with 1) unindicated stent placement, 2) use of short stents landed in the common iliac vein, and 3) smaller diameter stents than indicated. Patient selection relies on thorough pre-operative history, exam, and imaging. Intraoperative imaging can also aid in all three realms.
I assess any perceived compression points under Valsalva and breath hold maneuvers. Resolution of the perceived compression with these maneuvers more likely indicates an anatomical compression instead of a pathologic one that requires stenting. At this time, vein diameter is best assessed from an average of the minor and major diameters in the CIV and EIV. I select a stent size that will be oversized by 2 mm compared to the vein diameter in the majority of the stented segment. I advise against shorter length stents, and I never use less than a 100-120 mm. Stents should ideally transverse around the curvature of the pelvis and land in a healthy straight segment of iliac vein. Of note, landing in the curve can lead to further complications, including jailing of distal flow and stent erosion. Stent fracture is most likely when stents overlap on a turn or under the inguinal ligament.
References
- Mohamed Hosny Sayed, Murtaza Salem, Kush R Desai, Gerard J O'Sullivan, Stephen A Black, "A review of the incidence, outcome, and management of venous stent migration," J Vasc Surg Venous Lymphat Disord. 2022 Mar;10(2):482-490.doi: 10.1016/j.jvsv.2021.07.015.
