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Angioplasty.org Discusses Boston Scientific's Voluntary Recall of the Taxus and Express2 Stent Systems
(updated August 9, 2004)

In an effort to inform patients and healthcare professionals about the issues associated with this latest development in the world of drug-eluting stents, Angioplasty.org offers the following report on the recent recall of the TAXUS™ Express2™ Paclitaxel-Eluting Coronary Stent System and the Express2 Coronary Stent System. Patients may also be interested in our article, "What's a Patient To Do?".

Summary
  • If you currently have a Taxus or Express2 stent implanted, you are not at risk and this recall does not affect you
  • 1.1 million of these stents (combined) have been placed worldwide; there have been 95 confirmed reports of non-deflation problems, including 3 deaths and 43 serious injuries
  • The non-deflation problem is a mechanical difficulty with the delivery system, not with the drug-eluting stent itself
  • The company has implemented an FDA-approved modification to the manufacturing process to rectify this problem
  • The FDA recently finished their inspection of both of Boston Scientific's manufacturing plants (in Minnesota and Ireland) and found no problems

The Recall
On July 2, 2004, acting on reports of problems with balloon deflation in the TAXUS™ Express2™ Paclitaxel-Eluting Coronary Stent System (the company noted 30 complaints worldwide) Boston Scientific identified a potential problem in two manufacturing lots and recalled 200 of the stents. On futher investigation and analysis, Boston Scientific identified potential problems in additional lots of not only the Taxus Express2 Coronary Stent System but also the "bare metal" non-drug-coated Express2 Coronary Stent System (the two systems share the same delivery catheter). On July 16, the company voluntarily recalled approximately 85,000 TAXUS stent systems and approximately 11,000 Express2 stent systems, stating in its press release: "While the number of customer reports of balloon deflation difficulty is extremely small, patient safety is the Company's paramount concern, and therefore it has chosen to initiate this broader recall." On August 5, the company recalled an additional 3,000 Taxus stents, explaining that these particular stents were manufactured over a two-and-a-half-day period in late April at its plant in Ireland, before any of the recalls occurred. The company has stated that these batches should have been part of the previous recall, but were not, due to a "an inspection problem" in its Galway plant -- an optical component of the new visual inspection system (supplied by an outside vendor) was calibrated three thousandths of an inch off specification. While no problems had surfaced from that batch, the company decided to recall all catheters made on those days. Boston Scientific has held meetings with the FDA, and the FDA completed inspection of the company's manufacturing facilities in Maple Grove, Minnesota and Galway, Ireland on September 8 -- no observations of problems were issued.

The combined total for both stent systems of confirmed "no deflation" complaints (failure of the delivery catheter balloon to deflate within one minute after deployment of the stent) was small -- 95 out of approximately 1.1 million implants worldwide. However, as Boston Scientific noted, "impeded balloon deflation can result in significant patient complications, including coronary artery bypass graft surgery and death". The company received reports of one death and 18 serious injuries associated with balloon deflation for the TAXUS stent system, and two deaths and 25 serious injuries associated with balloon deflation in the Express2 (bare metal) stent system.

Background
The TAXUS™ Express2™ Paclitaxel-Eluting Coronary Stent System was approved by the FDA on March 4, 2004, making it the second drug-eluting stent available in the U.S. (the first was the CYPHER, manufactured by Johnson & Johnson / Cordis). Like all such devices, the TAXUS stent had gone through a series of clinical trials to demonstrate its safety and effectiveness in preventing restenosis (reclosing of the artery). Within a very short time, cardiologists had adopted the new device and the TAXUS stent soon claimed almost 70% of the U.S market. Some doctors felt it was easier to use than the CYPHER when trying to get into certain coronary arteries; it was also more readily available in a wider range of sizes.

"No Deflation" Problem Isolated
Boston Scientific reports that the cause of the "no deflation" condition has been isolated to the balloon catheter shaft and does not affect any other component (the stent, drug or polymer -- the coating that holds the drug on the stent). To understand the technical issues involved, it is necessary to examine how stents are deployed.

 

Stent-on-a-Balloon
Stents are placed in a process similar to angioplasty. The standard angioplasty catheter is a double-lumen structure (a concentric tube-within-a-larger-tube) consisting of a balloon that is laser-welded to a hollow shaft.

The hollow shaft lumen allows the catheter to be passed over a guide wire, while the outer lumen allows the balloon to be inflated and deflated. Stents are manufactured and delivered to the hospital already mounted on the balloon.


In the cath lab, the balloon/stent system is advanced by the interventional cardiologist along a thin guide wire to the diseased area in the coronary artery. When the balloon is inflated, the stent expands. The balloon is then deflated and withdrawn, and the stent remains in place, serving as a permanent scaffolding for the newly widened artery. Within a few weeks, the natural lining of the artery, called the endothelium, grows over the metallic surface of the stent. This procedure is the same whether the stent is the older "bare metal" type or the newer drug-eluting type.

  Animation of Stent Implantation

 

In the cases where the Taxus stent balloon would not deflate, and could not be withdrawn, Boston Scientific has reported that the condition was caused by a narrowing, or "focal neckdown", of the outer inflation/deflation lumen which restricts the flow of contrast media out of the balloon. This seemed to center around the proximal balloon weld, one of the two places where the balloon is laser-welded to the catheter shaft. When the shaft has a sufficient positive pulling force exerted on it, as would occur when withdrawing the catheter, while the area towards the tip of the balloon is constrained, a weakened area may collapse, thereby preventing the balloon deflation.

The Solution
Boston Scientific states that it has already implemented an FDA-approved modification of the laser welding process to make the proximal weld more robust, as well as an "enhanced inspection method" by quantitatively and visually inspecting every catheter to verify the minimum outer diameter of the proximal balloon weld . In addition, its plant in Maple Grove, Minnesota was "piloting a software program to monitor the parameters of the laser bonding process", a program whose data allowed the company to identify production lots with the appropriate laser bonds. The company states that to date, noproblems have been reported with any of the stents manufactured after these changes were put into place.

What Does This Mean for Patients and Physicians?
As stated above, any patient who has already had a successful implant does not need to be concerned -- the problem was with deployment, not with the stent itself (for more patient information on the recall, read Boston Scientific's Q&A's for patients -- in PDF format). On July 20, Boston Scientific announced that it had completed its recall and, according to Paul LaViolette, head of the company's cardiovascular unit, it planned to ship 30,000 of the Taxus heart devices to its clients in the United States immediately and that all inventory in the United States should be replaced by early August. He also stated that none of the recalled stent systems will be redistributed anywhere in the world. The most recent August 5 voluntary recall was an expansion of the July 16 action. The company believes it has isolated the problem and put into place new procedures that have eliminated it.

Complications with new products are not infrequent. Issues sometimes surface when a new device goes into widespread use. For example, not long after the Johnson & Johnson / Cordis CYPHER stent was approved last year by the FDA, some issues regarding sub-acute thrombosis with the CYPHER were raised (read our editorial on the CYPHER). Out of 450,000 CYPHER stents implanted, 60 cases of sub-acute thrombosis resulting in patient deaths had occurred (while the number was well within the complication rate for bare metal stents, it still was considered cause for concern -- subsequent investigation found no problem with the device itself).

As for Boston Scientific, the impact will be be financial, certainly in the short-term. When a product is introduced so successfuly, and then hits a snag, it's a difficult situation. And while the number of actual reported problems was relatively small, the recall ultimately had to be relatively large. As Jim Tobin, CEO of Boston Scientific, commented to theHeart.org, "If you can't find a needle in a haystack, you have to recall the whole haystack." Whether the cardiology community, which had enthusiastically embraced the Taxus stent for the past four months, will continue to utilize this new device as much as it has...well, in the words of Adam Feuerstein of TheStreet.com, "Boston Scientific Needs to Win Doctors' Hearts". This may be happening. One month after the final recall, the company reports that usage of the Taxus stent is almost at pre-recall levels. As for patient perceptions and concerns about the stent, read our feature topic, "What's a Patient To Do?".

For the latest news about developments in the field, go to our Drug-Eluting Stent NewsCenter. We welcome your comments on this article.

Source: Angioplasty.org, July 20, 2004, updated August 9, 2004

CONTACT: Burt Cohen, Producer of Angioplasty.org


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