Sigma® implantable pacemakers - advise patients to contact their follow-up clinic immediately if they experience a return of symptoms

(Medtronic) failure of interconnecting wires may cause loss of pacing output from atrial and or ventricular ports, premature depletion of battery, intermittent or total loss of telemetry, undersensing, high lead impedance values, loss of rate response, device reset to manufacturer's default settings. (MDA/2005/072)

Deadline (Action underway): 23 January 2006 Action plan to be agreed and actions started.

Deadline (Action complete): 24 April 2006 All actions to be completed.


Medtronic Sigma® implantable pacemakers

Model Numbers

SD203 SDR203 SS203 SSR203
SD303 SDR303 SS303 SSR303
SS103 SS106 SDR306 SVDD303

Affected serial numbers:

MDA/2005/072 - Serial numbers


Failure of interconnecting wires within the pacemaker may cause:

  • loss of pacing output from atrial and/or ventricular ports
  • premature battery depletion
  • intermittent or total loss of telemetry
  • undersensing
  • high lead impedance values
  • loss of rate response
  • device reset to manufacturer’s default settings

Medtronic has advised MHRA that some Sigma® pacemakers from the above model ranges may be subject to failures which could result in any of the behaviours listed on page 1. Medtronic issued letters to clinicians about this issue in November 2005 (See Appendices 1 and 2).

Medtronic’s analyses of 19 returned Sigma® pacemakers has identified a failure mode where separation of interconnecting wires between certain electronic components, can seriously affect the performance of the device.

Analysis has identified that the wire separation is associated with the use of an incorrect cleaning solvent during circuit board manufacturing that contained an antioxidant. The solvent, which was only used for a limited manufacturing period, resulted in surface contamination of electrical connection areas prior to wire bond connection. Extensive testing and analysis by Medtronic has now confirmed that use of this cleaning solvent can lead to a reduction in strength of the wire bond connections and these connections may separate over time. No mean time to failure has been established for this failure mode however there have been no failures less than 17 months post implant.

There is no provocative testing that can be performed to identify when any of the affected devices may fail.

Failure rates are currently low at approximately 0.05%. To date 19 Sigma® failures have been confirmed where wire bond connections have separated. Medtronic estimate that approximately 28,000 devices remain implanted worldwide. In the UK 1 failure by this mode has been confirmed to date out of an estimated 1700 devices that remain implanted. The UK failure occurred at implant duration of 36 months with the patient presenting with shortness of breath. Subsequent clinical checking confirmed no pacing output or telemetry.

Medtronic have received no reports of serious injuries or deaths due to this problem.

Affected Sigma® pacemakers may be identified through accessing the Medtronic website


  • Identify and return to Medtronic all un-implanted devices that are potentially affected (under ‘Download Documents’ below)
  • Identify all patients that have affected pacemakers and where last follow-up was longer than six months, arrange for pacemaker follow-up as soon as possible, giving priority to pacemaker dependant patients.
  • At follow-up confirm that the device is performing as expected. Abnormal device behaviours may include:
    • intermittent or total loss of pacing output in either or both of the atrial/ventricular ports
  • intermittent or total loss of telemetry
  • unanticipated premature battery depletion
  • unexplained increases in lead impedance(s) in unipolar or bipolar mode
  • undersensing
  • loss of rate response function (where applicable and programmed on)
  • power on reset - return to manufacturer’s default settings
  • Advise patients to contact their follow-up clinic immediately if they experience return of symptoms (e.g. syncope / light-headedness or shortness of breath).
  • Consider elective device replacement if any of the above device behaviours are detected, especially for pacemaker dependant patients giving consideration to each patient’s medical history, degree of pacemaker dependency and the relative risks of an invasive procedure.
  • Consider scheduling subsequent pacemaker follow-up at intervals no longer than six months, for all potentially affected pacemakers, to monitor for signs of device degradation.
  • Report all incidents of device failure to the MHRA and Medtronic.
  • Report explants to the National Pacing and ICD Database (see Contacts).

Action by

All cardiologists and cardiac physiologists who manage patients implanted or to be implanted with any of these devices.


  • NHS Trusts (England) - Chief Executives
  • Healthcare Commission (CHAI) - Headquarters

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


  • Liaison officers (for onward distribution)
  • Accident & emergency departments
  • Cardiac pacemaker/ICD physiologists
  • Cardiologists with pacemaker/ICD responsibilities
  • Cardiothoracic surgeons
  • Clinical governance leads
  • Medical directors
  • Nursing executive directors
  • Risk managers


  • Headquarters (for onward distribution)
  • Hospitals in the independent sector


Details of manufacturer/National Pacing & ICD Database, MHRA contacts for technical and clinical aspects.Change of address or removal from address list for Healthcare Commission.


Enquiries to the manufacturer or the National Pacing and ICD Database should be addressed to:

David G Dunham BSc PhD Regulatory Affairs Manager - UK & Ireland, Medtronic Ltd, Suite One, Sherbourne House, Croxley Business Centre, Watford WD18 8WW

Tel: 01923 212 213


National Pacing and ICD Database, PO Box 9205, Bridge of Weir, Strathclyde, PA11 3DZ

Tel: 01505 612 829 Fax: 01505 612 829



Enquiries to the MHRA should quote reference 2005/011/023/061/006 and be addressed to:

Technical aspects:

Miss Anna Richter or Mr Peter Solesbury, Medicines & Healthcare products Regulatory Agency, Market Towers, 1 Nine Elms Lane, London SW8 5NQ

Tel: 020 7084 3223/3215 Fax: 020 7084 3106

Clinical aspects

Dr Susanne Ludgate, Medicines & Healthcare products Regulatory Agency, Market Towers, 1 Nine Elms Lane, London SW8 5NQ

Tel: 020 7084 3123 Fax: 020 7084 3111

Change of address or removal from address list for Healthcare Commission

Healthcare Commission, Finsbury Tower, 103-105 Bunhill Row, London EC1Y 8TG

Tel: 020 7448 0842



Please see the PDF version for all appendices:

Full Device Alert

Published 17 December 2014