Covered verses uncovered stents for malignant common bile duct obstruction, which lasts longer?

The often taught convention that covered biliary stents stay open longer than their bare relatives may not be true. Researchers from Seoul, South Korea are challenging this, finding that uncovered stents had significantly longer patency in their subjects. Although limited by a small sample size of 20 patients in each arm, this prospective randomized study found that the uncovered stents had a mean patency of 413 days, double that of the covered ones at 208 days.

Covered stents were always thought to have better patency because of their ability to avoid tumor ingrowth, a theory that was previously supported by several randomized studies. After finding the opposite, the authors of this study theorize that pores on the surface of the covered stent act to promote bacterial colonization and biofilm development, in turn leading to slower bile flow. Nevertheless, the authors found no survival benefit for either stent.


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Kaplan-Meier graph showing cumulative stent patency. Cumulative stent patency was significantly higher in the uncovered metallic stent versus the covered metallic stent group (P = .041, log-rank test).




Stent occlusion by sludge. (a) Percutaneous cholangiography performed after 10 mm × 80 mm Niti-S covered stent placement. The stent is not yet fully dilated. (b) Cholangiography performed 2 months after stent placement showed multiple filling defects (arrows), suggesting debris. Debris and food material were confirmed by saline irrigation.


Citation: Lee, S. J. et al. Comparison of the Efficacy of Covered versus Uncovered Metallic Stents in Treating Inoperable Malignant Common Bile Duct Obstruction: A Randomized Trial. Journal of Vascular and Interventional Radiology (2014). doi:doi: 10.1016/j.jvir.2014.05.021


Post author: Amish Patel, MD

Robot-assisted fibroid embolization

Researchers from London, UK have recently published their early experience with the Magellan robotic catheter for use during uterine artery embolization. The 9-French outer diameter system has a multidirectional bending 6-F leading catheter that is used to catheterize vessels while the operator is seated in the control room, away from ionizing radiation. Where I trained we had something like this, but we were called “fellows” and not “robots.”

The system was used in 5 women with heavy bleeding during menstruation, four of which had fibroids and one that had adenomyosis. All procedures were technically successful and without major or access site complications. Median procedure time in this study was no different than previously published times, but median fluoroscopy time compared favorably to that in the literature for the conventional technique. Based on this early experience, the authors conclude that the use of the Magellan system in uterine artery embolization is feasible and safe.

However, don’t rush to throw your apron into the trash. Although the system can accept a microcatheter in place of a 0.035” wire, the wire manipulator is not currently compatible with microcatheters. So, if you get this system in your angiosuite sometime soon, you’ll still have get up and steer the microcatheter the old-fashioned way . . . or get your fellow to do it.


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The Magellan workstation




(a, b) The SmartMask function was employed to facilitate cannulation of the right internal iliac artery. Fine movements of the leader tip were then used to direct the microcatheter into the uterine artery.

Citation: Rolls, A. E. et al. Robot-Assisted Uterine Artery Embolization: A First-in-Woman Safety Evaluation of the Magellan System. Journal of Vascular and Interventional Radiology (2014). doi:doi: 10.1016/j.jvir.2014.05.022


Post author: Amish Patel, MD

Meta-Analysis of Infrapopliteal Atherosclerotic Disease Treatment Shows Added Benefit with Drug-Eluting Stent Placement

There have been many advances in the treatment of critical limb ischemia, however, optimal management and factors affecting short and long-term procedural success have not been clearly elucidated. The authors performed a meta-analysis of 42 studies representing 3,660 unique patients. While the analysis focused primarily on short-term outcomes with a very heterogenous set of procedural and research methodologies, the manuscript found significant, device-dependent, differences. Technical success rates were higher with bare metal stents and drug-eluting stents than with atherectomy or percutaneous transluminal angioplasty. Further, DES use had higher primary patency rates than atherectomy, BMS, and PTA. In addition, the 30-day rate of TLR was significantly higher with PTA (8.1%) than with BMSs (2.2%; P < .05) and DESs (1.1%; P < .05).

Comments: 

While this study is limited due to a variety of factors, the analysis was surprising in the significant, device-dependent, differences that could be identified. While further research is necessary, the results support the use of DES in the setting of infrapopliteal disease to improve technical success, primary patency, and TLR rates.


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Artist rendition of a drug-eluting stent, reproduced via Vankatesh et al: http://www.slideshare.net/quizzito/bioabsorbable-drugeluting-cardiac-stent-analysis


Citation: Razavi MK, Mustapha JA, Miller LE. Contemporary Systematic Review and Meta-Analysis of Early Outcomes with Percutaneous Treatment for Infrapopliteal Atherosclerotic Disease. J Vasc Interv Radiol, 25 (2014) 1489-96.


Post author: Luke Wilkins, MD

New Study Examines the Effectiveness of Collateral Vein Embolization for Non-Maturing Fistulas

Failure of a new arteriovenous fistula (AVF) may be defined as an unsuitable access site 3 months after creation. While most commonly this may be treated by balloon angioplasty, collateral vein embolization (CVE) is touted to promote maturation of a non-maturing AVF. Researchers from the University of Chicago evaluated 56 embolizations in 42 patients. The majority of patients treated by collateral vein embolization (76%) progressed to fistula maturity. In 79% of patients, this was done without angioplasty, contradicting the argument that collateral veins reflect venous outflow obstruction and do not, by themselves, indicate a true 'accessory' venous pathway. In addition, the study showed a trend toward higher rates of fistula failure in patients treated with radiocephalic fistulas undergoing CVE and PTA; however, the results were not statistically significant. Of note, fistula age, vessel, size, and number of collaterals did not correlate with the rate of fistula failure or success.

Comments: 

While this study is limited by lack of objective criteria for CVE and patient sample size, the results are compelling. Unlike prior studies investigating CVE, the number of CVE procedures performed in the absence of PTA in the present study makes for a strong argument that collateral veins may represent true accessory drainage pathways that return blood to the right atrium and prevent arterialization of the target outflow vein. While more research is warranted, one may consider incorporating more aggressive treatment strategies in the setting of a non-maturing fistula.


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(a) Digital subtraction angiogram in a 67-year-old man with new brachiocephalic fistula referred for fistula immaturity. Angiogram of the fistula demonstrates a large collateral vein arising from the primary venous outflow (arrow) without other diagnostic abnormality. This vessel was subsequently selected, and embolization was performed with four 0.035-inch, 8-mm pushable coils. (b) Postembolization image after CVE no longer demonstrates opacification of the collateral vessel.


Citation: Ahmed O, Patel M, Ginsburg M, Jilani D, Funaki B. Effectiveness of Collateral Vein Embolization for Salvage of Immature Native Arteriovenous Fistulas. J Vasc Interv Radiol 2014.


Post author: Luke Wilkins, MD