CardioNerds co-founder Dr. Dan Ambinder joins Dr. Abdelrhman Abumoawad, Dr. Leili Behrooz from the Boston University Vascular Medicine over hot chocolate in Boston. They discuss two interesting cases of lower extremity edema caused by May-Thurner syndrome. Dr. Naomi Hamburg (Professor of Vascular Medicine and Cards at BU/BMC) provides the ECPR for this episode. Audio editing by CardioNerds Academy Intern, Dr. Akiva Rosenzveig.

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Case 1: A 34-year-old woman with HIV on HAART presenting with left leg swelling and non-healing new foot ulcer for 3 months. She works as a cashier. On exam, her BMI is 35 kg/m² and there are intact pulses bilaterally. Her left leg has varicose veins in the territory of the great saphenous vein, hyperpigmentation, edema, and a foot ulcer. Her right leg appears normal. Venous Duplex ultrasonography showed chronic partially occlusive thrombus in the left common femoral and profunda femoral veins and decreased doppler respiratory variation on the left side. She was treated with debridement and compression therapy for ulcer healing. She was referred to vascular surgery and underwent contrast venography that demonstrated collateral circulation from the left lower extremity (LE) to the right lower extremity, and stenotic lesion at the left common iliac vein (LCIV). She was diagnosed with May-Thurner syndrome, and a venous stent was placed, and the patient was started on aspirin 81 mg daily for 6 months.

Case 2: A 71-year-old man presented with left lower extremity pain and edema. He underwent a left lower extremity venous Duplex ultrasound that showed chronic thrombus in the left proximal to distal femoral vein and acute thrombus in the left popliteal vein and was started on anticoagulation (AC). The patient was also having palpitations and was found to have paroxysmal atrial fibrillation. He underwent pulmonary vein isolation during which it was noted that his LCIV was subtotally occluded. He underwent CT venogram which showed lumbosacral osteophytic compression of the LCIV known as bony May-Thurner syndrome. Given minimal symptoms, the decision was made not to pursue interventional options and to manage conservatively with AC which the patient needs regardless.

1. An often under-recognized, but treatable cause of DVT is left common iliac vein compression known as May-Thurner syndrome.
   
2. Most patients who have May-Thurner anatomy are asymptomatic. Only a minority of patients with the May-Thurner anatomy present with symptoms such as left leg edema/pain and DVT.
   
3. Young women are at a higher risk of developing May-Thurner syndrome compared to men. 
   
4. A high degree of suspicion is needed to investigate patients with unilateral left-sided leg symptoms and venous duplex features of May-Thurner syndrome.
   
5. The diagnosis is made with non-invasive imaging including venous duplex, CT/MR venography, intravascular Ultrasound (IVUS), and catheter-based venography.
   
6. Although IVUS is the gold standard for diagnosis, due to its invasive nature, it has been replaced by CT/MR imaging.
   
7. Treatment includes anticoagulation if a thrombus is present. Most patients receive venous stenting at the obstructed site to prevent compression of the left common iliac vein. Some patients need catheter-directed thrombolysis prior to stent placement.
   

1. What is May-Thurner syndrome?
   

Classic May-Thurner syndrome is venous outflow obstruction due to external compression of the left common iliac vein by the right common iliac artery causing venous stasis which can lead to DVT. It is more common in women of reproductive age. Osteophytic/bony variant of May-Thurner Syndrome is when a prominent vertebral osteophyte compresses the iliac vein which is more common in older patients.

For another fascinating case of May-Thurner Syndrome, presenting with CTEPH, enjoy CardioNerds episode 53. Case Report: CTEPH & May Thurner Syndrome – Temple University.

• What is the presentation of May-Thurner Syndrome and what are the risk factors?
  

May-Thurner syndrome is often asymptomatic but may present with pain and swelling of the left leg with or without the presence of DVT. Some patients will develop signs of venous insufficiency such as varicose veins, pigmentations, and venous ulcers. Risk factors include scoliosis, female sex, use of oral contraceptives, and pregnancy. As demonstrated in CardioNerds episode #53, chronic thrombo-embolic pulmonary hypertension may be a long-term sequela.

• How do we diagnose May-Thurner Syndrome?
  

Features suggestive of proximal obstruction in the venous Duplex for the initial assessment of DVT or venous insufficiency raise suspicion for May-Thurner syndrome. These features include loss of respiratory variation of the venous blood flow. IVUS is the gold standard to diagnose May-Thurner Syndrome and can also provide information regarding the chronicity of the thrombus, which could help decide management (for example, whether to perform thrombolysis of acute clot burden). CT/MR venography may have high sensitivity and specificity to detect iliac vein compression nearing 95%. It is also useful in ruling out other causes of iliac vein compression such as osteophyte compression of the iliac vein.

• How do you treat May-Thurner Syndrome?
  

Management mainly focuses on addressing the patient’s symptoms. For patients with moderate to severe symptoms and significant venous stenosis, endovenous stenting is used rather than conservative management.

There are a paucity of data to clarify the optimal antithrombotic regimen following venous stent placement. Practrice patterns varry significantly in terms of antiplatelet/anticoagulant choice and the duration of treatment.

The presenct of complications such as DVT, venous stasis ulcer, etc should be managed as usual.

1. Mangla A, Hamad H. May-Thurner Syndrome. In: StatPearls. Treasure Island (FL): StatPearls Publishing; November 30, 2022. https://www.ncbi.nlm.nih.gov/books/NBK554377/
   
2. Kaltenmeier CT, Erben Y, Indes J, et al. Systematic review of May-Thurner syndrome with emphasis on gender differences. J Vasc Surg Venous Lymphat Disord. 2018;6(3):399-407.e4. doi:10.1016/j.jvsv.2017.11.006    https://pubmed.ncbi.nlm.nih.gov/29290600/
   
3. Poyyamoli S, Mehta P, Cherian M, et al. May-Thurner syndrome. Cardiovasc Diagn Ther. 2021;11(5):1104-1111. doi:10.21037/cdt.2020.03.07 https://pubmed.ncbi.nlm.nih.gov/34815961/
   
4. Knuttinen MG, Naidu S, Oklu R, et al. May-Thurner: diagnosis and endovascular management. Cardiovasc Diagn Ther. 2017;7(Suppl 3):S159-S164. doi:10.21037/CDT.2017.10.14 https://cdt.amegroups.com/article/view/17529/18075