May Thurner Syndrome: Diagnostic and Therapeutic Outcomes in an Institutional Setting

Introduction: May-Thurner syndrome (MTS), a chronic compression of left common iliac vein (CIV) against the lumbar vertebrae by overlying common iliac artery is an underappreciated contributor to left leg deep venous thrombosis. Even though the estimated prevalence of MTS is high in left-leg deep vein thrombosis (DVT) cases per autopsy studies, the clinical association remains low. Since the screening for MTS in patients with recurrent left-leg DVTs is not a common practice, diagnosis can either be incidental or a combination of clinical presentation and objective testing. Diagnosis is challenging via ultrasound (US) due to the deep anatomical location of iliac veins; therefore, invasive imaging including Contrast venography (CTV) is needed for confirmation. The management of MTS has been reformed over the years with the advances in minimally invasive therapeutic tools. We sought to review the management and outcomes of the MTS adult population by conducting a retrospective review to identify all adult cases of MTS at our academic safety net hospital between 2010 and 2022.

Methods: Data was extracted and analyzed for baseline parameters including age, gender, ethnicity, and body mass index (BMI). Presenting symptoms, imaging used for MTS diagnosis (including US Doppler, magnetic resonance venography or CTV), and interventional approaches (catheter or systemic thrombolysis, thrombectomy, balloon angioplasty and/or stent placement) were additionally documented. SAS v9.4 (Cary, NC) was used for statistical analysis.

Results: A total of 19 cases, predominantly females 68% (13/19), with a median age of 48 years and a mean BMI of 28.84 kg/m ² diagnosed with MTS were identified. The predominant initial presentation was left lower extremity edema and pain 36% (7/19) later found to have a DVT, followed by non-healing venous ulcer 15% (3/19) and pelvic congestion syndrome 0.05 % (1/19). Whereas 42% (8/19) of the patients were diagnosed with MTS while undergoing evaluation for chronic and recurrent DVTs. All patients were diagnosed following CTV using transvenous pressures with the formation of collateral veins and a pressure gradient of more than 2 mm Hg across iliofemoral stenosis at rest. Sixteen patients (84%) underwent endovascular stent placement, while one patient underwent Balloon Angioplasty only. One patient refused any intervention for MTS however underwent great saphenous vein ablation for chronic venous wounds. In view of anticoagulation therapy, the initial choice in the most cases was low molecular weight heparin (LMWH), which was later transitioned to other choices, 81 % (10/16) were switched to direct oral anticoagulants, (apixaban= 10, rivaroxaban=3) due to ease of administration and compliance, while 19 % (3/16) were continued on LMWH for patient preference and pregnancy. Post-intervention complications consisted of stent failure in 25% (4/16) patients; related to stent thrombosis and Post-thrombotic Syndrome (PTS) in 12.5 % (2/16) patients. No bleeding complications were seen post any case of endovascular stent placement.

Conclusion: This review was a highly educational experience giving us insight into this unacknowledged syndrome. Multiple factors could be contributing to this underdiagnosis, including invasive gold standard imaging for MTS, more easily recognizable risk factors for DVTs that can overshadow MTS, and a smaller number of data and studies. Some authorities have advocated a need to rule out MTS in young women with acute left lower extremity DVT, a clear female predominance was also noted (68%) in our analysis. Post-stent placement, systemic anticoagulation for 3-6 months is recommended, in our review, all patients (100%) who underwent stent placement were started on anticoagulation for at least 3 months. A small sample size, patients lost to follow-up (poor outcomes and complications could have been missed) and a single institutional review were some limitations of our study, however with a rare disease such as MTS with 2-3% prevalence it is difficult to conduct a large size, multi- institutional analysis. This study contributes to the limited literature available on MTS.