Factors associated with outcome after interventional treatment of symptomatic iliac vein compression syndrome

Article Outline

• Abstract
• Methods
  • Data source
  • Demographic and clinical information
  • Hypercoagulable disorders
  • Procedural data
  • Outcome variables
  • Statistical analysis
• Results
  • Demographic information
  • Clinical presentation and follow-up
  • Diagnostic testing
  • Treatment and results
  • Complications
  • Patency and follow-up
  • Univariate analysis
  • Multivariate analysis
• Discussion
• Author contributions
• Acknowledgment
• Appendix
• References
• Copyright

Background

Iliac vein compression syndrome (IVCS) results from compression of the left iliac vein by the overlying right iliac artery against the pelvic brim. In many cases, patients are symptomatic. In symptomatic cases, management consists of angioplasty and stenting. Although therapy is often initially successful, factors associated with long-term outcome have been poorly defined. The purpose of this study was to identify factors associated with stent patency.

Methods

The medical records of all patients who underwent iliac vein percutaneous transluminal angioplasty and stenting from January 1996 to December 2006 for symptomatic IVCS were reviewed retrospectively. There were 50 women and 8 men, with a mean age of 42 years (median, 39 years; range, 17-71 years). Primary, assisted primary, and secondary patency rates were determined. Patient characteristics and clinical variables were evaluated by univariate and multivariate analysis to determine association with vein patency.

Results

Symptoms consisted of lower extremity swelling (81%) and lower extremity pain (67%). Iliac vein obstruction was treated with pharmacologic thrombolysis (31% of patients) and mechanical thrombus fragmentation (17% of patients). The primary, assisted primary, and secondary patency rates of angioplasty/stenting were 74.1%, 79.7%, and 85.8% at 1 year and 38.1%, 62.8%, and 73.8% at 5 years, respectively. Using a Cox proportional risk model, male sex (hazard ratio, 6.5; P = .001), recent trauma (hazard ratio, 5.3; P = .001), and age younger than 40 years (hazard ratio, 3.8; P = .015) were associated with decreased primary patency. In the absence of any risk factors, primary patency was 94.4% at 1 year and 63.0% at 5 years, decreasing to 28.6% and 0% for two or more risk factors.

Conclusions

Patency rates for iliac vein percutaneous transluminal angioplasty and stenting in patients with IVCS can potentially be predicted on the basis of a multivariate model. Assessing risk factors allows for patient stratification and appropriate clinical decision making. Prospective validation of these variables is necessary.

Symptomatic iliac vein compression syndrome (IVCS), known also as May-Thurner syndrome, is uncommon. Although the prevalence of this anatomic abnormality in the population has been documented as 22% to 33% in autopsy series,¹, ², ³ it is often asymptomatic and can therefore be easily overlooked in the workup of acute iliofemoral deep venous thrombosis, especially in patients who do not fit the classic picture. IVCS is a condition of venous compression by the overlying iliac artery, usually the left common iliac vein by the right iliac artery. Strictures in the common iliac vein were first described by McMurrich² in 1908. However, it was not until 1957 that May and Thurner³ proposed that the pulsatile right iliac artery may be the cause of chronic left iliac vein changes. The clinical features of this syndrome were described by Cockett and Thomas⁴ in 1965. Patients often present with left leg swelling and pain secondary to acute thrombosis, generally involving the entire leg (including the thigh). The syndrome is particularly evident in young to middle-aged women, especially after multiple pregnancies. Alternatively, patients may present chronically with symptoms of venous insufficiency inadequately treated by compression stockings, intermittent leg elevation, and good exercise for the calf muscle pump. If symptoms do not respond to such a program or actually worsen with this program, this syndrome must be suspected, especially if it involves the left leg. Men also can present with this syndrome, and although leg swelling is most common in men, an ipsilateral varicocele has been reported in a male patient with iliac vein compression.⁵

In a previous report from our institution, we described our experience with and approach to the management of IVCS.⁶ Over the past decade, we have noted that stent patency rates are variable. We therefore sought to identify factors that influenced patency rates, to adapt treatment approaches appropriately. This study presents a retrospective review of our 10-year experience with endovascular treatment of IVCS, specifically addressing risk factors for decreased stent patency.

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Methods 

Data source 

The medical records of 145 patients who underwent venous interventions from January 1996 to December 2006 were reviewed. These patients are part of a clinical practice in which patients are followed up closely with duplex imaging after their interventions; flow is assessed at regular intervals. Patients with IVCS diagnosed by magnetic resonance venography, contrast phlebography, or intravascular ultrasonography (IVUS) and who underwent iliac vein angioplasty with stenting were then identified for retrospective analysis. The IVUS criterion for IVCS is an absence of a visible venous lumen surrounding the IVUS catheter, generally at the level of the right common iliac artery. Exclusion criteria included an index procedure performed at an outside hospital, angioplasty without stent placement, and no intervention.

Demographic and clinical information 

Each chart was reviewed for sex, age at the onset of symptoms, severity of the symptoms, a family history of hypercoagulable disorders, recent airline travel or other causes of immobility, recent trauma, recent surgical procedure, recent pregnancy, a history of malignancy, medications (including hormonal contraception or hormone-replacement therapy), obesity (defined as BMI >30.0 kg/m² or documentation of a diagnosis of obesity), and medical conditions including lower extremity deep venous thrombosis, pulmonary embolism, or hypercoagulable disorder. Basic CEAP scores were determined from clinical notes and from documented reflux studies before stenting, when available.⁷

Hypercoagulable disorders 

Patients were classified as having a hypercoagulable disorder if they had one of the following: factor V Leiden mutation heterozygosity or homozygosity, protein C or S deficiency, antithrombin deficiency, increased factor VIII level, prothrombin 20210A mutation, or methyltetrahydrofolate reductase mutation heterozygosity or homozygosity with concomitant hyperhomocysteinemia. In cases in which the hypercoagulable workup was either incomplete or missing, a clinical assessment was made. Evidence of hypercoagulable disorder—such as a personal or family history of recurrent deep venous thrombosis or pulmonary embolism, especially in the absence of explanatory factors, or multiple miscarriages—led to a presumptive diagnosis of hypercoagulability.

Procedural data 

Each case was reviewed for the imaging modalities used (duplex ultrasonography, computed tomography, magnetic resonance venography, contrast phlebography, or IVUS), location of the thrombus (iliocaval, iliac, iliofemoropopliteal, and so on), interventions used (chemical thrombolysis, mechanical thrombus fragmentation, venoplasty, stent placement, arteriovenous fistula creation, or inferior vena cava filter placement), the lytic agent used (if any), duration of thrombolysis, vessels lysed, vessels stented, number and size of stents, and total stent length.

Outcome variables 

The primary outcome variable was primary stent patency. Additional outcome variables were assisted primary patency, secondary stent patency, and subjective symptom improvement. Assisted primary patency was defined as uninterrupted stent patency after any additional rescue procedure (eg, venoplasty of in-stent restenosis). Secondary patency was defined as restoration of patency after a procedure (eg, lysis of an occluded stent with restoration of patency). Duration of follow-up was defined as the time from the initial intervention until the most recent clinical encounter. An event was defined as a loss of primary patency (eg, an assist procedure was required), loss of assisted primary patency (eg, a lysis procedure was required), or loss of secondary patency (eg, the stent became permanently occluded or an alternate bypass procedure was performed).⁸ If no event occurred, the duration was censored for statistical purposes at the most recent objective duplex ultrasound scan or phlebogram demonstrating stent patency.

Statistical analysis 

Patient characteristics and clinical variables were evaluated to determine association with stent patency. Univariate analysis of patient characteristics or technical variables was performed via Kaplan-Meier analysis with log-rank comparison. Any variables found to be significant in univariate analysis with P ≤ .10 were entered into a Cox proportional hazards model. P ≤ .05 was considered significant in the final analysis. Variables are presented as mean ± SD or SE as noted. All statistical calculations were performed with the SPSS software package, version 11.0.1 (SPSS Software Inc, Chicago, Ill).

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Results 

Demographic information 

From a 10-year period (1996-2006) of our venous reconstruction database, patients treated with endovascular therapy for IVCS were identified. Fifty-eight patients were treated, which included 50 women and 8 men. The mean age at presentation was 41.6 ± 13.2 years (median, 39 years; range, 17-71 years; Table I).

Table I. Patient demographics

Variable	Data
Total No. patients	58
Female	50(86%)
Age (y)	41.6±13.2
Average follow-up (mo)	29.7±30.3
Unilateral symptoms	51(88%)
Lower extremity swelling	47(81%)
Venous claudication or groin pain	39(67%)
Phlebitis	6(10%)
Phlegmasia alba dolens	2(3%)
Phlegmasia cerulean dolens	9(16%)
Hypercoagulable disorder	19(33%)
Obesity	21(36%)
Family history of clotting disorders	14(24%)
Lower extremity deep venous thrombosis	52(90%)
Pulmonary embolism	11(19%)
Postsurgical	11(19%)
Estrogen-based contraception	15(26%)
Hormone-replacement therapy	7(12%)
Recent trauma	8(14%)

Clinical presentation and follow-up 

All patients presented with left-sided symptoms; in 7 patients, the symptoms were bilateral. The time between the initial onset of symptoms and presentation ranged from less than 1 day to 31 years. The median time was 7 months. In the subset of patients with thrombotic disease, the time from the onset of clinical symptoms to initial intervention was 59 months (SE, 15 months; range, 0-376 months). This time represented the interval between presentation to a physician and the time until referral to our institution. Clinical presentations included lower extremity swelling (n = 47), lower extremity pain (n = 39), phlebitis (n = 6), phlegmasia alba dolens (n = 2), and phlegmasia cerulea dolens (n = 9). By CEAP classification, 47 (81%) were class C3 (edema), 12 (21%) were class C4a or C4b (skin changes including pigmentation, lipodermatosclerosis, or atrophie blanche), and 4 (7%) were classes C5 or C6 (healed or active ulcers). Eighteen patients (31%) underwent reflux studies: photoplethysmography, air plethysmography, or venous ultrasonography. Symptoms were from a postthrombotic etiology in 52 patients (90%) and from a primary obstructive etiology in 6 patients (10%). Venous reflux was noted in 12 (21%) patients: in 9 patients, reflux was limited to the deep system only, and in 3 patients there was reflux in the deep and superficial systems. Reflux was documented in the great saphenous vein in two patients, the external iliac vein in two patients, the common femoral vein in four patients, and the popliteal vein in three patients. CEAP scores are tabulated in Appendix I (online only). The average follow-up was 29.7 ± 30.3 months (median, 20 months; range, 0-124 months). Of the entire treated group (n = 58), 35 patients (60%) underwent formal hypercoagulability testing, of which 16 tests results were positive; the remaining 23 patients (40%) were assessed by subjective analysis, and 3 were classified as positive (Table II). A total of 52 patients (90%) had a current or prior deep venous thrombosis. A total of 21 patients (36%) were obese, 15 patients (26%) were taking oral contraceptive pills, 14 patients (24%) had a family history of clotting disorders, 11 patients (19%) had a history of pulmonary embolism, 11 patients (19%) had undergone recent surgery, 8 patients (14%) were victims of recent generalized blunt trauma, 7 patients (12%) were taking hormonal replacement medications, and 7 patients (12%) had been recently pregnant.

Table II. Hypercoagulable disorders

Diagnostic testing 

Evaluation in all patients consisted of a complete history and physical examination. Documentation of iliac vein compression by radiographic evidence was present in all cases. Subsequent evaluation included phlebography in all patients. The diagnosis was made by IVUS in 36 (62.1%) cases, by magnetic resonance venography in 9 (15.5%) cases, and by phlebography only in the remaining 13 (22.4%) cases. Duplex ultrasound imaging was performed in 57 (98.1%) cases. In 52 (90%) patients, deep venous thrombosis (current or by history) was present; in 2 cases, the thrombus was bilateral, but in both cases the contralateral thrombus was not in the iliac vein.

Treatment and results 

All treated patients underwent successful recanalization. Subjectively, of the 56 patients with follow-up data available, improvement was noted in 45 (80%), and no change was noted in 19 (20%); no patient described worsening of symptoms. Adjunctive treatments included pharmacologic thrombolysis, with a mean duration of 2.2 ± 1.2 days (n = 18), and mechanical thrombus fragmentation (n = 10). All patients were treated with angioplasty and stents. The mean number of stents was 2.7 ± 1.4 (median, 3; range, 1-7). The mean stent length was 137 ± 73 mm. Stents used in the study are listed in Appendix II (online only) and ranged in diameter from 8 to 16 mm, with 41% being 16 mm. This is consistent with our earlier practice.⁶ All stents were placed in the left iliac vein and extended into the inferior vena cava. One patient had stents placed concomitantly in the right iliac vein and the brachiocephalic vein. Inferior vena caval filters were placed in 18 patients. Six patients underwent subsequent formation of an arteriovenous fistula, typically consisting of an anastomosis between a branch of the great saphenous vein and the superficial femoral artery. Arteriovenous fistulas were constructed because of concern of poor inflow into the stented area. Of the six patients who had arteriovenous fistulas, no fistula currently remains patent. Four were taken down by angioembolization, and two spontaneously closed. Of the patients who underwent arteriovenous fistula creation, one has an open stent without further interventions, one has an open stent with a rescue procedure for stenosis, two have open stents after lytic therapy, and two have occluded stents. Additional operations were performed in six patients near the time of the initial stent placement, exclusive of cutdowns for percutaneous vascular access. In one patient, a left saphenopopliteal vein anastomosis and bypass was performed along with a left axillary vein transplantation to the left saphenous vein and a left saphenous external valvuloplasty. A second patient underwent cutdown for venous thrombectomy of the femoral vein. A third patient underwent creation of an arteriovenous fistula, common femoral vein venoplasty for web removal, and patch venoplasty, and a fourth patient underwent creation of an arteriovenous fistula only. Two additional patients underwent venoplasty for web removal only.

Complications 

In one case the most caudal Wallstent (Schneider, Minneapolis, Minn) in the left femoral vein was removed as a result of thrombosis, and in a second case a groin cutdown was performed for a retained balloon. In one patient, a 4-cm Wallstent placed in the left common iliac vein migrated into the inferior vena cava despite placement at the crossing of the right common iliac artery and had to be removed percutaneously. After this, a minimum of 6-cm-long Wallstents were used to ensure docking of the stent in the distal postthrombotic intima. Two patients had groin hematomas, one of which was associated with a retroperitoneal hematoma.

Patency and follow-up 

Duplex ultrasonography, phlebography, or both were performed in 54 patients (93.1%) after their initial stent procedure. One patient was lost to follow-up after discharge from the hospital. Life-table analysis of primary, primary assisted, and secondary stent patency is shown in Fig 1. Primary patency was 74.1% at 12 months (SE, 6.3%; n = 29) and 38.1% at 60 months (SE, 12.4%; n = 4). Assisted primary patency was 79.7% at 12 months (SE, 5.8%; n = 31) and 62.8% at 60 months (SE, 10.5%; n = 7). Secondary patency was 85.8% at 12 months (SE, 5.0%; n = 35) and 73.8% at 60 months (SE, 9.7%; n = 7). One death unrelated to treatment occurred 3.5 years after successful intervention.

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• Fig 1. 

  Life-table analysis of primary, primary assisted, and secondary patency.

After stent placement, 42 patients (72%) received warfarin for a variable length of time based on their underlying thrombotic risk potential. An additional 11 patients (19%) received antiplatelet therapy with clopidogrel, aspirin, or both for a minimum of 6 weeks. For five patients, data were not available regarding anticoagulation.

Univariate analysis 

We sought to determine whether stent patency was affected by patient or thrombus characteristics or treatment variables. Kaplan-Meier univariate analysis was performed for each variable vs primary patency. Log-rank comparisons were performed. Variables with P ≤ .1 were entered into a Cox proportional hazards model for multivariate analysis. Variables found significant in univariate analysis at P ≤ .10 were trauma, male sex, placement of an inferior vena cava filter, mechanical thrombus fragmentation, creation of an arteriovenous fistula (as part of the index procedure), obesity, stent longer than 180 mm, hypercoagulable state, age younger than 40 years, and more than three stents (Table III).

Table III. Univariate analysis for primary patency

IVC, Inferior vena cava.

Multivariate analysis 

Factors associated with decreased primary patency were male sex (hazard ratio, 6.5; P = .001), recent trauma (hazard ratio, 5.3; P = .001), and age younger than 40 years (hazard ratio, 3.8; P = .015; Table IV). Fig 2, Fig 3, Fig 4 demonstrate the variation in primary, assisted primary, and secondary patency relative to the number of risk factors identified by multivariate analysis. In patients with no risk factors, primary patency rates were 94.4% at 1 year and 63.0% at 5 years. These rates decreased to 74.6% at 1 year and 37.3% at 5 years for one risk factor and 28.6% at 1 year and 14.3% at 2 years for two risk factors. Similarly, assisted primary patency rates for patients with no risk factors were 94.4% at 1 and 5 years, decreasing to 86.3% at 1 year and 61.3% at 5 years for patients with one risk factor and 28.6% at 1 year and 14.3% at 2 years for two risk factors. Secondary patency rates were 94.4% at 1 and 5 years for no risk factors, 92.2% at 1 year and 73.7% at 5 years for one risk factor, and 42.9% at 1 year and 28.6% at 4 years for patients with two risk factors.

Table IV. Multivariate model of primary patency

CI, Confidence interval.

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• Fig 2. 

  Kaplan-Meier analysis of primary stent patency by number of risk factors. In the one case of a patient with all three risk factors, the stents occluded within 24 hours and required immediate reintervention; secondary patency remained durable beyond 2 years. Comparisons were made by using the log-rank statistic.

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• Fig 3. 

  Kaplan-Meier analysis of primary assisted stent patency by number of risk factors. Comparisons were made by using the log-rank statistic.

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• Fig 4. 

  Kaplan-Meier analysis of secondary stent patency by number of risk factors. Comparisons were made by using the log-rank statistic.

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Discussion 

Factors associated with decreased primary patency were male sex, recent trauma, and age younger than 40 years. It is important to note that with none of these three factors present, the primary patency at 1 year in our study was 94.4% and at 5 years was 63%. However, with two or more factors, patency decreased to 28.6% and 14.3% at 1 and 2 years, respectively.

The right iliac artery most commonly crosses the left common iliac vein just distal to the iliac bifurcation, as was the case for all patients in this study, although variations of this anatomy have been described.⁹ Compression of the vein by the overlying artery is quite common and generally painless. In one study of 50 consecutive asymptomatic patients, 24% demonstrated more than 50% compression and 66% showed more than 25% compression by using computed tomography with intravenous contrast and axial images with 2- to 5-mm slice width.¹⁰ However, in some patients this compression leads to significant symptoms, such as pain and swelling of the entire leg, deep venous thrombosis, or phlegmasia cerulea dolens, necessitating intervention. It is currently unclear why some patients progress to symptomatic obstruction whereas others have no sequelae in this apparently common anatomic scenario. Raju and Neglen⁹ proposed that iliac vein compression serves as a permissive lesion, similar to esophageal reflux in the etiology of esophageal cancer, and that patients with asymptomatic lesions should be educated and followed up closely for the early identification of acute occlusion.

Several methods are available to help to make this diagnosis, including air plethysmography, venous duplex ultrasound imaging, magnetic resonance imaging (magnetic resonance imaging/magnetic resonance venography), phlebography, computed tomographic imaging, and IVUS.⁶, ⁹, ¹¹, ¹², ¹³, ¹⁴ IVUS led to diagnosis in many of the patients in this study, followed by magnetic resonance imaging/magnetic resonance venography and phlebography.

Treatment involves both open surgical and endovascular interventions. Open procedures include venous patch angioplasty, division and relocation of the right common iliac artery, and placement of a silicon elastic bridge over the iliac vein.¹ A venous bypass (the Palma procedure) is also possible if the iliac vein is too severely damaged to be repaired. Endovenous techniques have the obvious advantage of not necessitating a major abdominal dissection. In a large group of 447 limbs with chronic nonmalignant obstruction with greater than 50% stenosis, after venoplasty and stenting, approximately 50% of patients were completely relieved of pain, and approximately one third were relieved of swelling.¹⁵ Additionally, more than half of open ulcers healed, even though associated reflux was not corrected in this study.

Although technical success for endovenous angioplasty and stenting has generally exceeded 87% to 95% and primary patency has ranged from 79% to 95% (1 year) to 73% (3 years),¹⁶, ¹⁷, ¹⁸, ¹⁹, ²⁰, ²¹, ²², ²³ very few data exist on factors that relate to long-term success. The most information to date comes from Neglen and Raju.²⁴ Over a 42-month follow-up, only 23% of patients showed no in-stent restenosis, 61% of patients had greater than 20% in-stent restenosis, and 15% of patients demonstrated greater than 50% in-stent restenosis. More limbs with thrombotic disease vs nonthrombotic disease showed in-stent restenosis: 20% narrowing was documented in 63% vs 41%, and 50% narrowing was documented in 23% vs 4%, respectively. Factors associated with in-stent restenosis were thrombotic disease, thrombophilia, and stenting below the inguinal ligament. In this study, long stent length was significant in univariate analysis, as was thrombophilia (P ≤ .10); in multivariate analysis, however, neither was independently associated with stent patency. It is possible that our study was underpowered to detect thrombotic disease as a risk factor, because only 6 of 58 patients presented without current or past thrombosis.

In the current study, we found recent trauma (mostly general blunt trauma, not isolated trauma to the iliac vein) to be associated with decreased stent patency, although recent surgery was not associated with worse outcomes. This may be because many of the surgical patients underwent orthopedic procedures and appropriate prophylaxis was used, whereas in cases of blunt trauma, no prophylaxis is available and is often contraindicated in the immediate posttrauma setting. Therefore, if patients have a predisposing lesion, this may result in an acute thrombotic occlusion.

Limitations of this study involve its retrospective nature, the limited number of patients evaluated, and the fact that not all patients evaluated underwent a full hypercoagulability workup. In addition, no quality-of-life assessment was made after intervention. Advantages include the facts that all patients were managed by the same team, the patients underwent close follow-up, and only symptomatic patients with objectively diagnosed iliac vein compression were treated.

In conclusion, in our experience, male sex, trauma, and young age were associated with decreased stent patency. These factors should be considered carefully when venous angioplasty and stenting are planned for left iliofemoral venous compression. We plan to evaluate this predictive model in a future prospective clinical trial.

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Author contributions 

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We gratefully acknowledge the assistance of the Michigan Surgical Collaborative for Outcomes Research and Evaluation (M-SCORE), including Dr Nancy Birkmeyer, Dr Onur Baser, and Zhaohui Fan, in the critical evaluation of the statistical analysis in this study.

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Appendix 

Additional material for this article may be found online at www.jvascsurg.org.

Appendix I (online only). Basic CEAP scores

Where an x is indicated, there were insufficient data to provide an assessment.

Appendix II (online only). List of stents used in endovascular treatment

The numbers for each stent represent the size of the stent in millimeters (diameter × length).

Wallstent (Schneider, Minneapolis, Minn) Palmaz 308 (Johnson & Johnson, Warren, NJ), Cordis SMART stent (Johnson & Johnson, Warren, NJ), Vivant Z stent (PFM AG, Cologne, Germany).

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