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Medical Devices

Catheter Entrapment with the ev3 Onyx Liquid Embolic System: FDA Safety Communication


  • Health Care Providers: Neuro Interventionalists treating patients with brain arteriovenous malformations (brain AVMs)
  • Patients with brain AVMs

Medical and Surgical Specialties: Neuro Interventionalists

The Onyx Liquid Embolic System (“Onyx”), manufactured by ev3, is a liquid material used to block blood flow in abnormally formed blood vessels in the brain, also know as brain arteriovenous malformations or brain AVMs, before their surgical removal. A catheter is used to deliver the Onyx liquid to the blood vessel(s) in the brain.

Onyx is intended to reduce bleeding and surgical complications when the brain AVM is removed, typically a few days after treatment with Onyx. During the Onyx embolization procedure, the physician uses fluoroscopy to guide the catheter to the site where the Onyx material will be implanted. Onyx material is injected through the catheter into the blood vessels of the brain at the location of the AVM. The Onyx material solidifies when it comes in contact with blood in order to block blood flow to the brain AVM.

The FDA is issuing this communication to inform physicians and patients about the risk of catheter entrapment associated with the use of Onyx. Catheter entrapment happens when the catheter becomes stuck in the implanted Onyx material. The clinical data submitted by the manufacturer prior to marketing included cases where the delivery catheter was difficult to remove, but in all cases the catheter was removed without any adverse patient events. The original product labeling did not reflect the risks related to catheter entrapment but new labeling will include these risks as well as recommendations to help minimize that risk.

Summary of Problem and Scope:
Since Jan. 1, 2005, the FDA has received more than 100 reported cases, including nine patient deaths, of catheter breakage that may be related to catheter entrapment. In some cases the catheter could be removed. In at least 54 of these cases, it was not possible to remove the catheter, so part of the catheter and the implanted Onyx material (Onyx plug) remained implanted in the patient.

Catheter entrapment is unlikely to affect the physician’s ability to surgically remove the patient’s AVM. However, neither Onyx nor the catheter is intended be a long-term implant, and patients may need additional medical interventions to have the catheter removed if it becomes entrapped.

Complications associated with catheter entrapment can be serious. The most serious complications include hemorrhage and death. Other complications include migration of the Onyx plug or catheter fragment to other parts of the body. Patients with catheter entrapment may need to take antithrombotic drugs to prevent blood clots around the catheter, and may need to undergo one or more imaging procedures to locate a piece of the catheter and Onyx plug, increasing their exposure to radiation.

In April 2012, the FDA approved changes to the physician and patient labeling that reflect the risks related to catheter entrapment. The labeling also includes recommendations to help minimize the risk of entrapment. Physicians should expect to see this labeling in new orders of Onyx.


Health Care Providers – Neuro Interventionalists:

  • Select patients carefully, after reviewing the most recent device labeling and instructions. Know that:
    • Onyx is only approved for use in patients who will undergo surgical removal of the treated brain AVM.
    • Onyx has not been tested or approved as a long-term implant.
  • Be prepared to emergently treat serious complications associated with the use of Onyx and ensure that your facility is staffed and equipped to address these complications should they arise.

If the catheter becomes entrapped:

  • Follow the manufacturer’s instructions for removing an entrapped catheter. Aggressive attempts to remove the catheter can result in catheter breakage or brain hemorrhage.
    • Report catheter entrapment, difficulties removing the catheter and other adverse events that occur with Onyx to FDA. For more information, see the section: Reporting Problems to FDA.

Be aware that removing an entrapped catheter may increase the duration of the procedure and increase a patient’s exposure to radiation from additional imaging.


If you have received Onyx treatment:
The potential for catheter entrapment occurs only during implantation. If you were treated with Onyx and did not experience this complication at the time of implantation, you are not at risk.

If your health care provider recommends surgical treatment for a brain AVM, talk to him/her about:

  • Whether you are a good candidate for treatment with Onyx
  • Risks and benefits associated with the use of Onyx
  • Problems that can occur with the use of Onyx, and additional medical procedures that may be needed to treat these problems.
  • The risk of catheter entrapment with Onyx, and the additional risks associated with entrapped-catheter removal.

FDA Activities:

In order to learn more about safety issues with Onyx, the FDA analyzed adverse event reports submitted about Onyx and catheters used to deliver the Onyx material.

The FDA will continue to monitor adverse events associated with the Onyx Liquid Embolic System and delivery catheters, and will make available any new information that might affect their use.

Reporting Problems to the FDA:

Prompt reporting of adverse events can help the FDA identify and better understand the risks associated with medical devices. If you suspect a problem with the Onyx Liquid Embolic System, including a difficult to remove or entrapped (retained) catheter while using Onyx, we encourage you to file a voluntary report through MedWatch, the FDA Safety Information and Adverse Event Reporting program. Health care personnel employed by facilities that are subject to the FDA's user facility reporting requirements should follow the reporting procedures established by their facilities.

Please include the following information in your reports, if available:

  • Adverse event details (date adverse event occurred; complications that occurred, e.g. retained or plugged catheter, migration of Onyx plug, hemorrhage of the brain AVM; and the medical intervention required)
  • Type of Onyx used (e.g. Onyx 18 or Onyx 34)
  • Expiration dates of Onyx, delivery catheter and all accessories used
  • Model and size of catheter used with Onyx
  • Location in the anatomy where Onyx was used
  • Amount (distance) of reflux
  • Whether vessel was in vasospasm
  • Whether surgical resection is planned
  • Location in the pedicle being embolized where the catheter got stuck. For example, proximity to the origin of the pedicle vessel and proximity to the Onyx plug.
  • Whether additional medical therapies (e.g. antithrombotics) were needed

Other Resources:

AVM Patient Information from the National Institutes of Health

Contact Information:

If you have questions about this communication, please contact the Division of Small Manufacturers, International and Consumer Assistance (DSMICA) at DSMICA@FDA.HHS.GOV, 800-638-2041 or 301-796-7100.

Page Last Updated: 01/12/2015
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