Overview of Venous Stenting
In the past ten years, medical professionals have increasingly turned to the use of stents, small tube-like devices, to treat conditions affecting our veins. One such condition is iliocaval venous obstruction (ICVO), where blood flow is blocked in the large veins that carry blood from your lower body back to your heart. Traditional treatment involved surgery, but now stents offer a less invasive alternative.
ICVO can lead to continuous problems with your veins, such as chronic venous insufficiency (which means your leg veins struggle to send blood back to your heart) and chronic venous hypertension (high blood pressure in the veins). Symptoms include leg pain when walking, ongoing swelling, sores or ulcers, and other complications of post-thrombotic syndrome (chronic symptoms that occur after having deep vein thrombosis). Women and people with a previous history of deep vein reflux, a condition where blood flows backward in the veins, seem to be more prone to contracting ICVO.
In cases where ICVO is especially severe, just using compression stockings and exercise, typical home remedies for swelling in the limbs, can become less effective and may even make symptoms worse. Stenting has proven to be a reliable treatment for ICVO as it can reduce symptoms in most patients. Medical studies involving over 1500 patients have found that using stents for venous problems is both safe and effective, with improvements in pain, sores, and leg swelling reported, and very low complication rates.
The early versions of stents used for ICVO were made of a self-expanding braid composed of cobalt, chromium, and nickel alloy. But, they had some issues related to their size, the pressure they exerted, and their capacity to resist being crushed or fractured. Also, placement of these stents could be a bit inaccurate due to a phenomenon called foreshortening (shrinking in length when expanded).
Newer designs of venous stents, approved by the US Food and Drug Administration (FDA), have addressed these problems by improving their resistance to being crushed. Except for a recent recall of two stents due to problems with deployment, these new stents have shown promising results in terms of efficacy and safety. Most importantly, these stents have significantly improved the healing of ulcers.
As per the current medical guidelines, the use of stents to treat ICVO is recommended as the primary treatment in patients with skin changes, healed or active ulcers. Aimed at improving patient outcomes, stent technology continues to evolve to provide better treatment options for venous conditions.
Why do People Need Venous Stenting
Deep venous thrombosis (DVT) is a condition where a blood clot forms in a deep vein, usually in the leg. For patients with a recent case of DVT, a procedure known as thrombolysis may be performed to break down these clots. Following this, inserting a tiny mesh tube called a stent into a blood vessel (iliac stenting) helps improve blood flow and reduces the chances of the vein getting blocked again.
For those with a long-term blockage in their veins (chronic PTO), the shape and condition of the blocked vessel and the patient’s symptoms are important to consider. These symptoms may include pain, swelling (edema), and leg ulcers that haven’t healed despite treatment, including interventions in the lower leg. Ulcers are areas of skin that have broken down and revealed the flesh underneath.
In patients with NIVL (condition causing pain, swelling and ulcers in the legs because of vein problem), symptoms can differ from person to person. Some people experience chronic pelvic pain, exertion-induced leg pain (venous claudication), and swelling. But, sometimes, the degree of symptoms does not match the extent of vein compression discovered through imaging. Some patients with this compression have no symptoms at all. However, it’s not recommended to place a stent in such patients who show evidence of compression but have no symptoms.
While swelling of the legs can be a symptom, there are many causes other than vein problems. It’s important to investigate the primary reason causing the swelling to ensure that placing a stent is truly beneficial for the patient.
When a Person Should Avoid Venous Stenting
There are certain situations or conditions where inserting a stent into the vein that carries blood from the lower part of the body to the heart, also known as iliocaval stenting, might not be advisable. Some were worried about the safety of this procedure for women in the age range where they can bear children. However, recent studies have confirmed that stent insertion can be performed safely in these women. It’s important that after the stent is inserted, these women have regular check-ups with their doctors to ensure everything remains okay.
Preparing for Venous Stenting
When diagnosing vein-related health issues, doctors often use various imaging methods. These might include CT venography, intravascular ultrasound (IVUS), MRI venography, and multiplanar venography – all of them serve to confirm the diagnosis and to check for any possible external blockage. Other procedures like duplex ultrasonography and plethysmography can provide further insight into conditions like DVT (a blood clot in a deep vein) and blocked veins. However, these are usually more effective when used in combination with other imaging methods.
In more detail, with duplex ultrasound, a significant narrowing (more than a 50% reduction in vein diameter) at the point where the vein is being compressed, as well as an increased flow speed (more than 2.5 times the normal speed) in the compressed part of the internal iliac vein (a major vein in the pelvic area), are indications of problematic narrowing in the veins.
Mostly, a combination of multiplanar venography and IVUS is used when a stent (a tube inserted in the vein to keep it open) needs to be placed with precision. The exact area and length of the narrowed vein can thus be identified properly. In cases of PTO (a disorder characterized by blood clot formations), venography is helpful for showing unusual blood flow patterns, while for patients with symptomatic NIVL (narrowing of the veins), it shows the compressed vein area and the accumulative effect of the contrast agent (a substance used to make the vascular system visible during imaging).
To confirm the area’s narrowing and the extend of this constriction, IVUS is used to visualise the cross-sectional reduction in the area. Comparisons are then made to a normal segment of the same vein. Research trials have shown that compared to multi planar venography, IVUS is more accurate at identifying significant narrowing areas (more than 50% of the cross-sectional area) that could benefit from a medical intervention.
The selection of the correct treatment based on these finding is important as it significantly impacts patients’ lives since the stents placed in the veins are permanent. A vein’s diameter can change based on the patient’s position, hydration levels, and breathing. Thus, IVUS is often used alongside providing intravenous fluids and instructing the patient to perform a Valsalva maneuver (forceful exhalation against a closed airway) to get accurate measurements of the vein’s size.
It has been shown that IVUS is more sensitive for assessing treatable narrowing of the main vein in the leg than standard imaging processes. It also often leads to revised treatment plans and potentially better health outcomes. For people with NIVL, using IVUS to identify a reduction in diameter of more than 61% can better predict who will see clinical improvement from the procedure.
How is Venous Stenting performed
The method a doctor chooses to insert a stent (a small tube used to keep your blood vessels open) in your veins will vary depending on: where the problem is, what caused it, and how severe it is. In patients undergoing treatment for a sudden Deep Vein Thrombosis (DVT), a medical condition where blood clots form in the deeper veins of your body, the stent is often put in alongside other treatments like breaking up the clots by using drugs (thrombolysis) or physical means (mechanical thrombectomy). The veins usually accessed for these urgent interventions are the popliteal vein (behind your knee) and posterior tibial vein (in your leg).
For patients with a chronic (long-term) DVT, doctors’ decision on where to place the stent will be guided by the extent of the disease. Doctors might access the saphenous vein in your leg to clear a blockage in the lower extremity via a procedure known as Internal Jugular Vein (IJV) access. They then can reroute the IJV into the vein in your upper thigh (femoral vein) or deep thigh vein (profunda femoris vein). By using vein imaging (venography), they place the stent at the ideal location because of its positioning at the union of two important veins in your thigh.
Once the stent has been placed, doctors will undergo imaging verification and ensure your blood remains thin and does not clot. In case of a sudden DVT, doctors will break down the clot with drugs and imaging will be used to confirm the clot has dissolved and stent has been placed correctly. They will then calculate the severity of any remaining blockage in the vein by comparing the blocked segment with a healthy vein.
Doctors will accurately determine the size of the stent required using an IVUS catheter, a device with a small camera on the end. Once implanted, the stent will gradually widen the vein. This is done by initially using a balloon under high pressure, which upon partial inflation, an X-ray is done. If normal shapes and flow are not seen with the balloon in place, this suggests the stent needs to be inflated further. Once the stent is in place, second balloon inflation is performed.
The stents will be slightly bigger than the calculated measurements from the real-time IVUS imagery. If more than one stent needs to be inserted, they will overlap by at least 2 inches to ensure effective coverage of the blocked area. After the procedure, doctors will perform more scans to ensure the stent is supplying proper blood flow and placed snugly against the vein wall.
There isn’t much scientific literature on how doctors should do follow-up scans to check if the stent is still open (stent patency) or how long you should be on blood thinners (anticoagulation). After the operation, you will be encouraged to move around and your doctor will provide you with anticoagulant and antiplatelet therapy as they see fit. If you have had a DVT, either chronic or acute, you will be transitioned to blood thinning medications for a period. Patients with a condition that makes their blood clot more easily than normal (hypercoagulable state), are typically given blood thinners for an indefinite period. There is no guideline yet on how long patients should be kept on blood thinners.
After the procedure, you will have an imaging scan within a few weeks to check for any disturbances in the stent’s blood flow or the presence of any clot attached to the stent’s wall. Further, your stent patency will be assessed using ultrasound scans at 3 months, 6 months, and then yearly. This is to evaluate your primary veins in your body.
When chronic and post-clot blockages in the femoral (leg) vein and ICVO are associated with disability, bypass interventions are commonly unsuccessful. In patients with a diseased or blocked femoral vein, doctors often choose an operative procedure that combines an opening in the blocked area in the vein (endovenectomy) with the placement of a stent or a bypass procedure. Procedures that combine stent placement and open surgical intervention may be necessary.
Possible Complications of Venous Stenting
Getting the right size for a stent (a tiny tube inserted into a blocked blood vessel to keep it open) is crucial to avoid problems like the stent moving from its original position. This has caused certain kinds of stents to be taken off the market. If a vein is incorrectly measured and a too small stent is used, it could move to other parts of the body, such as the right atrium (one of the four chambers of the heart) or the intraspinal canal (a canal in the spine). However, if a stent is too big, it can lead to back pain after the procedure. In rare cases, severe ongoing pain might require the stent to be removed.
Stents are generally placed in parts of a blood vessel that aren’t affected by the disease. If the main vein entering the stent is seriously affected by the disease, it could cause the stent to fail. So, it’s really important to make sure there’s good blood flow into the stent. It’s also essential to avoid placing stents in areas that bend a lot, like the pelvic curvature or the inguinal ligament (a ligament in the lower part of the abdomen) because this could cause kinking (a sharp bend or twist) in the vein, which could cause a blood clot in the stent. Another point to note is that if a large scar extends from a vein in the leg or the common femoral vein (the vein that carries blood from the leg back to the heart) to the inferior vena cava (the largest vein in the body), it might require multiple stents, which could indicate an early failure of the stent graft. Additionally, blocking the opposite large vein could lead to another blood clot and persistent ulcers (open sores).
What Else Should I Know About Venous Stenting?
The VIRTUS trial, a research study conducted at multiple centers, showed that a special type of stent (a small, flexible tube that holds open a blood vessel) used to treat ICVO (or blockages in the veins) was effective and safe to use for up to a year. The trial found that patients’ symptoms improved and they felt better overall as measured by a tool called the Venous Clinical Severity Score (VCSS).
A separate study showed that patients who received iliac vein stenting (a procedure where a stent is used to open a blocked vein in the hip area) had less pain and better well being, as measured by the VCSS and the SF-36, two medical scoring systems that measure health-related quality of life, when compared to patients who only received standard medical treatment. The research also suggested that stenting might help heal venous leg ulcers (wounds on the leg resulting from poor blood flow), but the results were not definitive.
Interestingly, even in patients with vein closures successful through endovenous thermal ablation (a medical procedure that uses heat to seal off faulty veins), nearly 21% of them had symptoms return within five years. This recurrence could be due to existing blockages. A study that looked back at patients’ records found that symptoms persisted on average for four months after endovenous thermal ablation. Adding a stent in the vein offered further symptom relief for about one-third of patients who had this procedure.
