Zenith abdominal aortic aneurysm (AAA) endovascular grafts and associated H&L-B One-Shot - serious injury or death of the patient during graft deployment

(Cook Medical Incorporated) potential for serious injury or death of the patient due to the difficulty or inability to release the suprarenal stent during graft deployment. (MDA/2009/023).


Zenith® abdominal aortic aneurysm (AAA) endovascular grafts and associated H&L-B One-Shot™ introduction systems. Manufactured by Cook Medical Incorporated.

Zenith® abdominal aortic aneurysm (AAA) endovascular grafts and associated H&L-B One-ShotTM Introduction Systems


Potential for serious injury or death of the patient due to difficulty releasing or inability to release the suprarenal stent during graft deployment.

MHRA has received reports relating to complications experienced during attempts to release the topcap and deploy the suprarenal stent (top-stent) in a number of Cook Zenith AAA endograft procedures. These have involved difficulties releasing or inability to remove the proximal black trigger-wire, delaying or preventing the release of the top-cap and the associated deployment of the enclosed top-stent.

Cook Zenith endovascular grafts have unique proximal and distal trigger-wire release mechanisms. The purpose of the proximal black trigger-wire is to prevent the premature release of the barbed top-stent held within the top-cap of the H&L-B One-Shot Introduction System. The trigger-wire passes through a single hole in the top-cap and through one of the top-stent ‘stent eyelets’ constrained within it. Once deployed, the top-stent is designed to provide physical radial pressure on the aortic wall and stability for the AAA endograft device, minimising the risk of distal migration.

Deployment of this device is a multistage procedure. When the proximal trigger-wire is about to be removed, the endograft is already in a partially deployed condition and it is no longer possible to re-sheath or remove the device from the patient.

Although the worldwide incidence of trigger-wire or top-cap release problems with this introduction system since 2003 remains low (below 0.1%) these have included serious patient complications such as conversion to open surgery, permanent injury or subsequent patient death.

The following factors appear to give rise to difficulty in removing the proximal trigger-wire:

  1. inadvertent upward movement of the top-cap in relation to the top-stent during insertion and manipulation of the introduction system may raise tension on the trigger-wire, thereby temporarily entrapping it and increasing the potential for wire deformation;
  2. the tension between the entrapped trigger-wire and the top-cap may be amplified further if an operator pulls downwards on this trigger-wire in an effort to free it, possibly leading to added deformation of the trigger-wire. Similarly, undue tension will be applied to the entrapped trigger-wire if the top-cap is pushed forward in an attempt to free the top-stent.

Excessive downward force on a deformed, entrapped trigger-wire may also irreversibly alter the shape and position of the proximal end of the inner cannula and dilator tip, causing it to bow. It is important to ensure that the manufacturer’s recommended model and length of stiff guide wire is used and advanced beyond the end of the dilator tip (to the thoracic aorta) to provide maximum support for the inner cannula.

Techniques that may help resolve an entrapped trigger wire are described in the ‘Physicians Reference Manual’ (see Chapter 8, pages 126-127). If these techniques are unsuccessful, an alternative deployment sequence is available to resolve the situation (see trigger wire release instructions).

Well maintained and high resolution fluoroscopy equipment is essential for troubleshooting during implantation of these complex devices. Good fluoroscopy will also assist in accurately confirming the position of the top-cap in relation to the top-stent.


  • review previous guidance on resolving trigger wire release problems in the manufacturer’s ‘Important Patient Safety Information’, (published November 2008) and in the device ‘Physicians Manual’.
  • obtain the manufacturer’s recent guidance (issued February 2009) on a new troubleshooting technique.
  • consider the need for additional training being offered by the manufacturer to ensure proficiency with the new technique.
  • ensure fluoroscopy equipment used during endovascular graft implantation has adequate resolution to aid deployment and, if necessary, troubleshooting.


This MDA has been distributed to:

  • NHS trusts in England (Chief Executives)
  • Care Quality Commission (CQC) (Headquarters)
  • Health Protection Agency (HPA) (Directors)
  • HSC Trusts in Northern Ireland (Chief Executives)
  • NHS Boards in Scotland (Chief Executives)
  • Primary care trusts in England (Chief Executives)
  • Social services in England (Directors)

Onward distribution

Please bring this notice to the attention of all who need to know or be aware of it. This may include distribution by:

Trusts to:
CAS and SABS (NI) liaison officers for onward distribution to all relevant staff including:

  • Cardiothoracic departments
  • Cardiothoracic surgeons
  • Clinical governance leads
  • Interventional radiologist suite managers
  • Medical directors
  • Medical libraries
  • Radiologists
  • Radiology departments
  • Radiology directors
  • Risk managers
  • Theatre managers
  • Theatres
  • Vascular surgeons

Care Quality Commission (CQC) (England only) to:

Headquarters for onward distribution to:

  • Clinics
  • Hospitals in the independent sector
  • Independent treatment centres

Health Protection Agency to:
Directors for onward distribution to:

  • Collaborating centres
  • Divisional directors
  • Heads of department
  • Heads of health, safety and quality
  • Regional directors
  • Risk managers
  • Safety officers

Change of address or removal from address list for Care Quality Commission:

National Contact Centre
Care Quality Commission
St Nicholas Building
St Nicholas Street
Tel: 03000 61 61 61

E-mail: enquiries@cqc.org.uk

Manufacturer contact

Cook Incorporated
750 N Daniels Way
Bloomington, IN 47404
Tel: +1 (812) 339 2235
Fax: +1 (812) 355 6213

European Representative

Mr Arne Mølgaard-Nielsen
William Cook Europe
Sandet 6, DK 4632
Tel: +45 5686 8686

E-mail: a.moelgaard@cook-wce.com


If you are in England, please send enquiries about this notice to the MHRA, quoting reference number MDA/2009/023 or 2008/008/007/061/009.

Technical aspects

Alexander McLaren or Samantha Baxter
Medicines & Healthcare products Regulatory Agency
Market Towers
1 Nine Elms Lane
Tel: 020 7084 3292/3242
Fax: 020 7084 3106


Clinical aspects

Dr Christopher Brittain
Medicines & Healthcare products Regulatory Agency
Market Towers
1 Nine Elms Lane
Tel: 020 7084 3126
Fax: 020 7084 3111

E-mail: christopher.brittain@mhra.gsi.gov.uk

How to report adverse incidents
Please report via our website http://www.mhra.gov.uk
Further information about CAS can be found at https://www.cas.dh.gov.uk/Home.aspx

Northern Ireland

Alerts in Northern Ireland will continue to be distributed via the NI SABS system.

Enquiries and adverse incident reports in Northern Ireland should be addressed to:

Northern Ireland Adverse Incident Centre (NIAIC)
Health Estates
Estate Policy Directorate
Stoney Road
BT16 1US
Tel: 02890 523 704
Fax: 02890 523 900

E-mail: NIAIC@dhsspsni.gov.uk

How to report adverse incidents in Northern Ireland
Please report directly to NIAIC, further information can be found on our website http://www.dhsspsni.gov.uk/niaic
Further information about SABS can be found at https://sabs.dhsspsni.gov.uk


Enquiries and adverse incident reports in Scotland should be addressed to:

Incident Reporting and Investigation Centre
Health Facilities Scotland
NHS National Services Scotland
Gyle Square
1 South Gyle Crescent
EH12 9EB
Tel: 0131 275 7575
Fax: 0131 314 0722

E-mail: iric@shs.csa.scot.nhs.uk


Enquiries in Wales should be addressed to:

National Assembly for Wales
HIMTE 3 Division
NHS Directorate
Cathays Park
CF10 3NQ
Tel: 029 2082 3373
Fax: 029 2082 5479

E-mail: Haz-Aic@wales.gsi.gov.uk

Download documents

Medical Device Alert: Zenith abdominal aortic aneurysm (AAA) endovascular grafts and associated H&L-B One-Shot Introduction Systems (MDA/2009/023) (194Kb)

Published 17 December 2014