In this retrospective study of 39 patients with iliofemoral post-thrombotic obstruction with infrainguinal involvement, endovenous infrainguinal stent placement was successful in all patients. The majority of patients reported clinical improvement and had patent stents at final follow-up. None of the patients with occluded stents reported clinical deterioration. Patients classified as having “good” inflow had better patency compared to those with “fair/poor”, and inflow seemed to be a more important predictor of patency than localization of lower stent border.
The two-year cumulative primary patency in our study was 78%. This is in line with the results reported by Neglen et al. on 53 patients with stents extending into the common femoral vein (Neglen et al., 2008). Van Vuuren et al. recently reported on patency and clinical outcome in 369 patients who received percutaneous stent placement or a hybrid procedure (combining stenting with open surgical disobliteration and arteriovenous fistula) depending on the extent of the infrainguinal post-thrombotic obstruction with regard to the sapheno-femoral junction (van Vuuren et al., 2017a, b, c). In this material the 60 months primary, primary assisted, and secondary patency in the stent group were 64%, 81% and 89%, respectively. However, 29% received re-intervention(s), which is higher than in our study. The corresponding patency rates in the hybrid group after 36 months follow-up were 37%, 62% and 72%, the complication rate was high with 89%, and 59% received various re-interventions (van Vuuren et al., 2017a, b, c). Poor results for the hybrid approach has also been reported in a small study by Garg et al. with a 24 months cumulative secondary patency of 30% (Garg et al., 2011).
Another recent report by the same Dutch group included 24 patients undergoing a scheduled procedure for closure of arteriovenous fistula following a hybrid procedure with stenting below the sapheno-femoral junction (van Vuuren et al., 2017a, b, c). The lower stent border was placed into the vessel with highest quality and flow as assessed on ascending venography. The primary, primary assisted, and secondary patency were 60%, 70% and 70%, respectively. In line with the findings in our study, the authors indicate that in patients with infrainguinal obstruction and sufficient inflow on imaging, primary stenting may be a favorable alternative to the hybrid approach.
Although the evidence of infrainguinal stent placement into the common femoral vein is growing, the experience with stent placement into the deep femoral and femoral vein is scarce (Wittens et al., 2015; Rosales et al., 2010; van Vuuren et al., 2017a, b, c). Moreover, given the low primary patency rate and high rates of re-intervention and complications following hybrid procedures, further research and development should aim at optimizing the solely percutaneous stenting technique. This also includes studying the efficacy of the new generation dedicated venous stents in infrainguinal venous obstructions. These nitinol stents have the advantage of easier deployment and various combinations of flexibility and radial force, with the potential of better performance compared to braided stainless steel stents.
The overall favorable outcomes following recanalization and infrainguinal stenting, and the few other treatment options available, justify a minimally invasive approach in these patients (Wittens et al., 2015). Moreover, the endovascular approach is safe and even with failed stent patency no clinical deterioration was reported in our study.
In spite of the dedicated follow-up and explicit patient information about the importance of immediate contact in the case of symptom recurrence, the majority of stent occlusions were detected at a planned follow-up visit. This may have contributed to the low number of re-interventions in this study. Accordingly, the quality of the patient information may be improved, however the delay in diagnostics may also be explained by insidious development of in-stent restenosis with little symptoms, or a limited immediate access to health care.
In our study the stented segments in the two patients who were classified as having “poor” inflow occluded after 8 months. Hence, endovenous stent placement may not be justified for small caliber inflow vessels with post-thrombotic changes, and a hybrid approach can be an alternative treatment approach in these patients (van Vuuren et al., 2017a, b, c).
Two of the 24 patients classified as having “good” inflow experienced stent occlusion. One occluded following cessation of anticoagulation. The other patient experienced early stent occlusion with concurrent contralateral iliofemoral occlusion; a rare, but previously reported complication for stent protrusion into the inferior vena cava (Neglen et al.,2007). The etiology of the bilateral occlusion in this patient with no known thrombophilia was not identified, and other factors than inflow may have contributed to the stent occlusion.
Limitations to this study include its retrospective design, the low number of patients and no control group. Although IVUS is becoming an established image modality for venous assessment, IVUS was not used in our study. However, it has been reported that IVUS has higher sensitivity for the detection of venous stenosis compared to CV (Neglen and Raju, 2002; Gagne et al., 2017). Post-thrombotic changes detected on IVUS and not on CV, may improve the assessment of stent landing zone (Neglen and Raju, 2002). The Villalta scale has been recommended for the diagnosis and assessment of post-thrombotic syndrome (PTS) in clinical trials (Kahn et al., 2009). With our retrospective study design it was not possible to provide Villalta scores. However, good correlation between Villalta scale and VCSS has been shown, and VCSS may be more sensitive in severe PTS (Jayaraj and Meissner, 2014).
Our findings confirm the importance of adequate venous inflow, and indicate that the suggested inflow classification may be valuable in guiding the decision on where to place the lower stent border, and possibly which patients may not be suitable for endovascular treatment. However, the validity and reliability of such a classification needs to be applied and assessed in a larger patient cohort. Nevertheless, we think that in addition to MRV patients with post-thrombotic obstruction in the femoral confluence, should be examined with a CV with contrast injection from the dorsum of the foot, or from the popliteal vein, to evaluate axial transformation and inflow to improve the decision on optimal stent landing zone.
Although there are reports on the benefit of endovenous stenting, controlled trials have been lacking. A randomised study comparing venous stenting with conservative treatment is ongoing and its research protocol has been published (van Vuuren et al., 2017a, b, c).