The Therapeutic Approach of the May-Thurner Syndrome without Deep Venous Thrombosis : a Systematic Review

May-Thurner Syndrome is a clinical condition which causes a variety of vascular symptoms, resulting from pelvic and lower extremity venous flow obstruction caused by the compression of the iliac vein by overlying iliac artery. Treatment paradigms have changed as experience with endovascular modalities has evolved, making traditional surgical treatment strategies essentially obsolete and a endovascular treatment with angioplasty and stenting along selective thrombolysis has become the standard for symptomatic the syndrome. The objective of this present study is to show the therapeutic approach in treatment when there’s no presence of Deep Venous Thrombosis (DVT) symptoms. To accomplish this purpose, a systematic review of articles about May-Thurner Syndrome and its management therapies, published from January 1, 2005 to September 20, 2015, on PubMED and SCOPUS databases, was carried out. Search terms were “maythurner syndrome” (medical subject headings [MeSH term]), “iliocaval compression syndrome” (MeSH), “cockett syndrome” (MeSH), “peripheral vascular diseases” (MeSH), and “treatment” (keyword). Of the 89 retrieved studies, 14 met the elegibility criteria. Retrieved studies covered that without correction of this syndrome, patients are at continued risk for recurrent deep vein thrombosis and postthrombotic syndrome. Considering the therapy, systemic anticoagulation is the first component, and endovascular treatment appears to be superior to conventional surgical treatment. It should be the first line of therapy. Furthermore, there has been multiple advences in the recent years for chronic arterial occlusions using techniques such as blunt micro dissection, radiofrequency energy and laser. In the absence of deep venous trombosis, conservative treatments are The Therapeutic Approach of the May-Thurner Syndrome without Deep Venous Thrombosis: a Systematic Review REVIEW Thaís Abreu Luedy1, Isadora Rodrigues da Costa2, João Vitor Pimentel1, Francisco Henrique Peixoto da Silva1


Introduction
Iliac vein compression syndrome (IVCS), also known as May-Thurner or Cockett syndrome, is a clinical condition which causes lower extremity swelling, pain, varicosities and other symptoms, resulting from pelvic and lower extremity venous flow obstruction caused by the compression of the iliac vein by overlying iliac artery.[1] This compression may present symptomatically or be an incidental finding.[2] The incidence of IVCS is extremely difficult to accurately estimate due to the high percentage of patients who are asymptomatic, and thus the denominator is unknown.[3] While the estimated incidence of this underlying anatomic variant is approximately 22-24%, the actual risk of progression to thrombosis is believed to be influenced by other factors affecting a patient's coagulation profile.[4] In the past, open vascular surgery was necessary and included vein-patch angioplasty with excision of intraluminal bands, division of the right common iliac artery and relocation behind the left common iliac vein or inferior vena cava, and contralateral saphenous vein graft bypass to the ipsilateral common femoral vein with creation of a temporary arteriovenous fistula (Palma crossover).[5] Treatment paradigms have changed as experience with endovascular modalities has evolved, making traditional surgical treatment strategies for IVCS essentially obsolete.Meanwhile, endovascular treatment with angioplasty and stenting along selective thrombolysis has become the standard for symptomatic IVCS.[3] Therefore, this review intends to analyze the approach of the current literature about the therapeutic management of IVCS treatments when there's no presence of Deep Venous Thrombosis (DVT) symptoms.

Methods
It was performed a qualitative review of the articles about May-Thurner Syndrome and its management therapies, especially those focusing this syndrome without Deep Venous Thrombosis (DVT), published in electronic databases previously selected.We have also included the articles that aimed to discuss the syndrome after DVT due to the little quantity of available articles in the databases.
It was conducted a search in the literature through the online electronic PubMED and Scopus databases, limiting it to published articles from January 1 of 2005 to September 20 of 2015.The reason to delimitate this research time is that there is little approach in literature about this theme, which means it is important to demonstrate that the current literature has few productions about patients with May-Thurner Syndrome that did not presented Deep Venous Thrombosis (DVT), and how they were managed to achieve a great therapy.Thus, it was aimed to perform a brief but sufficient analysis of the articles published.
Initially, the following descriptors were used: The research was performed using all these descriptors together, following the order: 1 AND 2 AND 3 AND 4 AND 5.The keyword "Treatment" was used focusing the gathering of the maximum number of publications related to the therapeutic management of the patients with this syndrome.All articles wrote in English were collected.
The results analysis was followed by the application of the inclusion criteria, which were: • articles that had in title or in abstract at least one combination of the descripted terms in the search strategy; • publications wrote in English language; • studies that discussed the focus theme; • observational prospective and retrospective studies (analytical or descriptive), clinic essay and case reports.
The exclusion criteria were: • other study designs, such as reviews and book chapters; • non-original studies including editorials, preface, brief communication and letter to editor; • studies that did not focus the May-Thurner Syndrome and its treatment; • unavailable study abstract or full text.Each article of the sample was read, filtered and, accordingly, included in this review's sample.

Results
The implementation of the previously described search strategy resulted in 89 articles, from which 53 were from PubMED and 36 were from Scopus.9 of these studies were presented in both Scopus and PubMED databases, so these duplicated ones were excluded.After an insightful analysis of the found studies, 66 were excluded because they matched one of the previous cited exclusion criteria.14 were included in the final sample.A better summary of the found articles is shown in Figure 1.In addi-

Discussion
IVCS is an independent etiologic factor affecting the pathogenesis of iliac venous outflow obstruction and appears to play an important role in the clinical expression of chronic venous insufficiency, particu-larly by producing pain.[6] Symptomatic IVCS occurs predominantly in young to middle-aged women (20-40 years).Patients present with either sudden onset of symptoms or with a long-standing history of venous congestion with or without deep venous thrombosis (DVT).[7] Therapy for May-Thurner syndrome has evolved over the years.Conservative therapy with compressive stockings has been largely unsuccessful, likely due to the proximal mechanical nature of the obstruction.Many surgical procedures for the relief of obstruction have been described.[8] Recent imaging data indicate that compression of the LCIV (Left Commom Iliac Vein) at the arterial crossover point may be present in 66% of the general population without any venous symptoms [9] and without correction of this compression, patients are at high risk to develop a recurrent deep vein thrombosis and post-thrombotic syndrome.
The goal of treating May-Thurner in the setting of iliofemoral DVT is to prevent or attenuate symptoms of post-thrombotic syndrome, including chronic leg swelling, venous claudication, stasis dermatitis, and ulcers, as well as varicosities associated with valve damage and iliac venous outflow obstruction.Considering the therapy, systemic anticoagulation is the first component.However, that alone is not adequate for the treatment of DVT with May-Thurner, as it fails to address any of the long-term sequelae in this group of pacients.[10] May-Thurner syndrome, in which the overriding right iliac artery compresses the left iliac vein, will rarely respond to conservative treatments, [11] including anticoagulation and fibrinolysis [12], given the physical etiology of the disease.[11] Pacients with iliofemoral thrombosis and May-Thurner should be treated aggressively with catheter directed thrombolysis, percutaneous mechanical trombectomy and angioplasty and stent placement across the common iliac stenosis.It should be stressed that stent placement is an essential component to therapy as May-Thurner is an acquired disorder from mechanical obstruction.[10] The treatment of May-Thurner syndrome has also leaned toward endovascular therapy involving thrombolysis followed by balloon angioplasty and stenting.[11] Authors of other studies have reported successful endovascular treatment of common iliac vein compression by stent placement.[7] This type of therapy is a minimally invasive approach to treating venous lesions and is feasible and effective for treating left-sided IVCS with a high technical success rate and an acceptable complication pro-file.Therefore, endovascular treatment appears to be superior to conventional surgical treatment and should be the first line of therapy for many patients suffering from IVCS.[8] An endovascular mechanical thrombectomy, combined with guiding catheter suction, can substitute most of the surgical embolectomy.[1] In addition, it appears that balloon venoplasty and stenting of the iliac vein in chronically obstructed limbs is a safe, minimally invasive method with a minimal complication rate, no mortality, and an acceptable 1-year patency rate.[8] Overall, balloon angioplasty and stenting is safe and effective, and the complication rate is likely to decrease as technology evolves and experience increases.[8] Multiple advanced endovascular have been developed in recent years for chronic arterial occlusions using techniques such as blunt micro dissection, radiofrequency energy and laser.[11] In this context, is important to mention that there are only few absolute contraindications for iliocaval stenting including uncorrectable coagulopathy and local or systemic infection.[13] Operative intervention for May-Thurner with acute thrombosis includes thrombectomy with adjunctive arteriouvenous fistula and relief of the distal iliac obstructionn via dissection of the right common iliac artery off the left common iliac vein.[10] Therefore, early recognition and endovascular treatment of iliac vein compression could prevent a DVT and an improvement in the symptoms.[1] The treatment, however, depends on the presence of DVT.It is difficult to find isolated iliac vein compression without thrombosis in a clinical setting, but it does not indicate the low incidence of iliac vein compression.[1] In the absence of DVT, conservative treatments are preferred.Compression stockings alone may be effective.However, this review showed that the literature about May-Thurner Syndrome without DVT does not mention the specific treatment used in the conservative therapy.

Conclusion
The data obtained from the evaluated patients suggest that those ones who have the May-Thurner syndrome are more likely to present thrombosis.
Treatment involves both open surgical and endovascular interventions.Open procedures include venous patch angioplasty, division and reallocation of the right common iliac artery, and placement of a silicon elastic bridge over the iliac vein.[14] The data also suggests that endovascular treatment for IVCS, with or without DVT, is safe and effective, although it is still not certain what the best treatment is.[1] Further clinical trials are required to define the optimal treatment strategy [8], especially in the May-Thurner Syndrome cases in the absence of DVT.
Finally, based on the review of the literature, a combination of conservative and endovascular therapy usually provides the best treatment in most cases.

Figure 1 : 14 )
Figure 1: PRISMA Flow diagram summarizing the selection process of studies for review.

Table 1 .
Overview of selected articles.