The Sticky Story of Stuck Stents

We now know what was long suspected. In fact, interventionists suspected it for years, dating back to 2004 when the Food and Drug Administration first investigated Boston Scientific’s TAXUS drug eluting stent for “stickiness of the balloon during withdrawal.”1,2 But nothing was ever proven. Until now. In this issue of the Journal, Turk et al report their tests on several stent/balloon delivery systems to determine whether the TAXUS stent delivery balloon is more difficult to withdraw after stent deployment than other stent balloons.3 Their ex vivo setup included silastic tubes in a heated bath, fitted into forms with 0, 20, and 40 degree bends. They deployed TAXUS and CYPHER drug eluting stents, and their bare metal versions, the Liberté and the BX Velocity. The authors report that Taxus stents were more difficult to withdraw, particularly on a bend, with an up to 10-fold increase in withdrawal force required for TAXUS compared to CYPHER or bare metal Liberté stent delivery balloons. Is this clinically important? The authors think so. They correctly note that incidents have been reported of “sticky” balloons leading to coronary dissections and even emergency bypass surgery. This information comes from the Manufacturer and User Facility Device Experience (MAUDE) Database (https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfMAUDE/search.CFM). MAUDE is worth a 5-minute visit. It is an easily searchable, public access database consisting of voluntary user-reported vignettes describing difficulties attributed to devices. Reading the cases involving coronary stenting is like reading a collection of horror stories. If patients found it, our cath labs might be empty. The MAUDE website introduction clearly states it is “not intended to be used either to evaluate rates of adverse events or to compare adverse event occurrence rates across devices.” Despite this warning, the authors searched MAUDE from 2004 to mid 2006 and found 390 reports of “sticking” or “difficult to remove” problems attributed to the TAXUS compared to “virtually no similar complications” from the CYPHER or bare metal Express or Liberté stents. We checked MAUDE reports from 2004 through 2008 for “sticking” or “difficult to remove” problems and found 201 reports related to TAXUS and 145 related to CYPHER, less one-sided than reported by the authors. TAXUS fans might take comfort in the finding that there were 159 balloon burst-related incidents with CYPHER versus only 6 with TAXUS over the same period. Overall, for 2005–2008 (the period during which both TAXUS and CYPHER were approved and widely used), there were 9587 TAXUS-related and 8440 CYPHER-related incidents reported to MAUDE. Hardly evidence to justify abandoning the TAXUS. Does the TAXUS balloon “stickiness” reported by the authors translate into adverse patient outcomes? Large randomized trials and registries reporting procedural outcomes4–7 and early clinical complications4,8–11 do not show any statistically significant differences, or even trends, of increased procedural complications with TAXUS stents compared to CYPHER or bare metal stents. Nor could we find any case reports of problems withdrawing the TAXUS stent deployment system. In fact, we found only two references to this phenomenon in the stenting literature.1,2 Even if TAXUS “stickiness” does not produce a visible signal in large studies, do the MAUDE reports implicate the TAXUS in “sticky” complications? Not clearly. MAUDE documents “difficulty in removing” stent delivery balloons with both CYPHER and TAXUS. Further, as the authors acknowledge, interventionists are skilled at working their way out of sticky situations. A review of incidents related to “difficult to remove” TAXUS or CYPHER stent delivery balloons, randomly selected from the MAUDE database, finds that the vast majority (e.g., 95%) result in no injury to the patient. Tricks used by operators include repeated inflation/deflations, inflation of a second “buddy” balloon in the stent to loosen the stuck stent delivery balloon, sidebranch balloons to provide counter-traction, and buddy wires to straighten stents on a bend. They are usually successful. Even when deep-seated guides cause catheter tip dissection, additional stents usually save the day. A quick review of the MAUDE database incidents, representing what may be a random sample of procedural difficulties, shows that difficult withdrawal is only one of many device-related procedural difficulties. Others, familiar to all interventionists, include balloon rupture, stent loss off the catheter, wire fracture, and even stent fracture. Compared to these, difficult withdrawal may be one of the easier problems to solve. Do interventionists, knowing that the TAXUS stent delivery balloon is more difficult to withdraw compared to other brands, have an ethical obligation to avoid the TAXUS, at least in tortuous calcified lesions where it is most likely to cause problems? Is even one complication due to a “sticky” stent too many? The authors’ data shows that TAXUS balloon delivery withdrawal force is minimal in straight segments, so interventionists can stick with TAXUS for straight arteries. But withdrawal forces increase dramatically with increasing bend severity, and most MAUDE reports of difficult balloon withdrawal were in tortuous, heavily calcified arteries. So, for lesions such as these, operators might wisely select a different drug-eluting stent. A stuck stent deployed in a severe bend resulting in a serious complication might leave the operator open to criticism and a malpractice suit.12 What are the implications from the device-safety point of view? A more obvious problem with TAXUS stents occurred in 2004, when failure of stent delivery balloons to deflate in 40 patients led to 18 serious injuries and 1 death. This forced the recall of 88,000 TAXUS stents and a modification of the balloon manufacturing process.1 Apparently device surveillance methods in place at that time never detected enough problems related to “stickiness” to prompt the FDA to take action on this issue.2 Improved device surveillance systems were mandated by Congress in 2007 which, when fully implemented in 2012, may more easily distinguish devices that are dangerous.13 In the final analysis, Turk et al are to be congratulated for studying a phenomenon which has been suspected by interventional operators since the introduction of TAXUS 6 years ago. In a field where manufacturers make myriad claims but peer-reviewed objective data are scarce, we now know that TAXUS can stick. It is true that stent “stickiness” is only one of many factors that interventionists should consider as they pick their stents. But it is a fact that we are stuck with.

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From the Department of Cardiology, Geisinger Medical Center, Danville, Pennsylvania and *The Faculty of Medicine, University of Glasgow, Glasgow, United Kingdom. The authors report no financial relationships or conflicts of interest regarding the content herein. Address for correspondence: Jim Blankenship, MD, Department of Cardiology 21-60, Geisinger Medical Center, 100 North Academy Drive, Danville PA 17822. Email: Jblankenship@geisinger.edu

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References

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