While MTS and its sequelae were historically treated with open surgical bypass procedures (albeit rarely), the current treatment choice is minimally invasive, venography- and IVUS-guided, endovascular stenting. Beginning with the development of lytic techniques in the early 1990s, the use of catheter-directed thrombolysis and venography for the treatment of iliofemoral DVT frequently identified compression of the left CIV and simultaneously offered the ability to treat the underlying conditions with iliocaval stenting. With the widespread adoption of advanced endovascular techniques, iliac vein stenting for symptomatic MTS leading to acute iliofemoral deep venous thrombosis, as well as a host of other chronic venous occlusive lesions , has now become standard practice in most centers.

Any treatment should be preceded by thorough history and physical exam that subsequently guides appropriate diagnostic imaging. Hypercoagulable workup should be done when any underlying coagulopathy may be suspected, as genetic thrombophilias can dictate anticoagulation management in some patients undergoing stenting for MTS.

For those patients with non-thrombotic MTS presenting with symptoms of mild unilateral left leg swelling, a trial period of daily compression stocking use, exercise program, weight loss, and other conservative measures is appropriate and should be considered first-line therapy after initial evaluation with duplex ultrasonography. Daily use of stockings can control many of the symptoms and may eliminate the need for stent implantation in compliant patients. Patients with severe or debilitating symptoms, or those that have failed a trial of compression therapy, should undergo venography and IVUS assessment of the iliac venous system, often with the intention of stenting at the same setting if appropriate.

Venography and IVUS can be performed under local anesthesia in an outpatient setting, although conscious sedation can be helpful if stenting is planned due to the associated back pain that often accompanies stent placement . Access for therapeutic interventions is guided by duplex ultrasound, which is used to identify a non-diseased segment of femoral or common femoral vein. For non-thrombotic MTS with unilateral leg swelling, antegrade duplex-guided access is generally performed at the common femoral vein, although patients with previously unrecognized deep venous thrombosis may have common femoral vein or femoral vein scarring that necessitates puncture of the femoral vein at the mid-thigh level or popliteal level. In anticipation of stent implantation, the puncture should be done below all diseased segments to allow for stenting of all diseased segments of vein, including across the inguinal ligament if necessary.

Initial venograms are obtained after venous access is achieved, observing for the venogram findings described above, including iliac vein contrast stagnation, extensive collateralization, and contralateral cross-filling to the right iliac circulation. Our practice includes selective catheterization of the contralateral right iliofemoral venous system via left femoral access, followed by simultaneous contrast injection within the diagnostic catheter in the right iliac circulation and the left femoral sheath to compare flow patterns bilaterally (Fig. 35.3). Next, wire access is established across the left common iliac vein into the inferior vena cava, and IVUS is used to assess cross-sectional area of the left iliac system and to identify the point of maximal compression of the left common iliac vein. If proceeding with stent implantation, the sheath is upsized to an appropriately large sheath for stent delivery (generally 10Fr for braided stainless steel stents), and the patient is anticoagulated with 100 units/kg of intravenous heparin.

Choosing the proper stent size is based upon IVUS diameter measurements of the compressed vein and also the proximal vein segment, which is an important anchor point for the stent. Oversizing 10–20% is appropriate, and undersizing should be avoided as it may lead to stent migration or embolization. In patients with isolated compression of the distal left CIV and no evidence of postthrombotic scarring, stents are placed from the normal-appearing proximal segment of the left common iliac vein to the caval confluence. It is critical to extend the stent at least 1–2 cm beyond the point of maximal compression, as determined by IVUS. This generally includes extension of the stent into the inferior vena cava by at least 1 cm, which is rarely of any consequence to the flow through the right iliac system. Our group exclusively uses braided stainless steel stents, typically in diameters of 16–20 mm, for iliac vein stenting. These stents perform well in this location but have reduced radial force at the ends, thus the requirement to extend the stent into the vena cava (Fig. 35.4). While there are self-expanding nitinol stents specifically designed for venous stenting under investigation in the USA, these are not yet commercially available. In patients found to have postthrombotic scarring of portions of the iliac or common femoral veins, it is generally recommended that all diseased areas be stented to avoid stent thrombosis due to poor venous blood flow. Following stent implantation, balloon angioplasty is used to help stent expansion and achieve adequate wall apposition (Fig. 35.5). Completion venography and IVUS imaging should be performed subsequently to evaluate luminal gain and stent apposition to the vein wall (Fig. 35.6).

In thrombotic May-Thurner patients presenting with acute iliofemoral DVT, lysis or pharmacomechanical thrombectomy is required prior to treatment of the underlying venous compression pathology. Venous access in these cases is typically via the popliteal vein with the patient in the prone position to access the venous system below the lower extent of the thrombus burden. For patients with acute deep venous thrombosis and symptoms of less than 1-week duration, an attempt of a single-session clearance of the thrombus with pharmacomechanical thrombectomy is reasonable, generally utilizing the AngioJet system (Boston Scientific, Minneapolis, MN) in the “power pulse” mode in which the thrombus is laced with 10 mg of tissue plasminogen activator, followed by aspiration of the lysed thrombus after a 10–20-min dwell time. For patients with a longer interval between initial symptom onset and treatment, we have noted less success with single-session thrombus clearance attempts and therefore recommend overnight catheter-directed thrombolysis , typically at tissue plasminogen activator drip rates of 0.5–1.0 mg/h. Following clearance of thrombus, venographic and IVUS evaluation for May-Thurner compression of the left common iliac vein is nearly identical to that discussed for non-thrombotic May-Thurner patients , with the caveat that these patients are more likely to have additional postthrombotic occlusive lesions, and these lesions from the common femoral vein (even below the inguinal ligament) up to the caval confluence should be stented if they are flow limiting (Figs. 35.7 and 35.8).

Anticoagulation with heparin is performed intra-procedurally, with activated clotting times (ACT) of 250–300 desired prior to stent implantation. Postoperatively, aspirin 81 mg daily and clopidogrel 75 mg daily are prescribed to all stented patients for a period of 3 months, at which point we favor single antiplatelet therapy with aspirin alone. In patients with a history of hypercoagulable state or those treated with lysis for acute DVT before correction of the MTS lesions, appropriate systemic anticoagulation is continued according to national guidelines. Oral opioid analgesics and muscle relaxants are prescribed perioperatively for pain control, as oftentimes patients complain of lower back pain within the first 1–2 weeks after stent implantation.

Perioperative complications are infrequent , with the most common being back pain that can be managed with oral analgesics and muscle relaxants as noted above. Access site complications, including puncture site hematomas, may occur in the setting of full anticoagulation and antiplatelet therapy, although these are uncommon complications that require no treatment in most cases. The rate of complications has been reported to be as low as 0.3% in large series of iliac vein stenting [12].

Post-intervention, patients are imaged with duplex US to confirm patency of the iliac venous system within 2 weeks, as our experience suggests that patients that lose patency tend to do so in the early postoperative period due to technical factors, and if these are identified early, the patient can undergo lysis and correction of the inciting issue. Thereafter, patients are followed at 6 months and then yearly with duplex ultrasonography and assessment of residual symptoms. Patients generally experience significant improvement shortly after stenting, but ongoing clinical improvement can continue to be seen for up to 1 year.

The paradigm shift toward endovascular treatment of May-Turner patients is now a decade and a half old, with a growing library of evidence to support not only acute endovascular thrombus clearance strategies in thrombotic May-Thurner syndrome but also the effectiveness of stenting as a definitive treatment of iliofemoral compression.

Raju and Neglen have published widely on iliofemoral stenting for a broad range of obstructive venous lesions, beginning with a publication on their early experience in 2000, establishing the technique’s safety and good short-term outcomes. The study of 77 patients showed a technical success rate of 97% and primary and secondary patency rates of 82% and 92%, respectively, at 1 year [13]. Followed further to an average of 30 months by the same group, a cohort of 610 limbs stented for nonmalignant obstructive lesions of the iliofemoral and caval venous system had an overall primary patency rate of 67%, assisted primary patency rate of 89%, and secondary cumulative primary patency rate of 93% at 6 years [12].