External pacemakers - sudden increase in pacing rate and change of mode

(APC Medical Ltd) the pacing rate for models E4162, E4164, E4165 and E4166 may increase by 20 pulses per minute and change in pacing mode in some cases. (MDA/2003/008)


Issued: 27 March 2003


External Pacemakers: Models - E4162, E4164, E4165 and E4166 (manufactured by APC Medical Ltd)


The APC Medical E4162, E4164, E4165 and E4166 external pacemaker models incorporate a design feature whereby the pacing rate will increase by approximately 20ppm, when either the battery voltage becomes low, or when electromagnetic interference is sensed. In both instances the mode of pacing changes from demand to asynchronous pacing. The original intention of this design feature was to avoid competitive pacing and pacing on the T-wave (initiating VT/VF), by increasing the set paced rate by approximately 20ppm.

Some patients however may not tolerate such a sudden increase in pacing rate, which may be detrimental to their condition (eg open-heart surgery, valve replacement, congestive heart failure, myocardial infarction, arrhythmia etc). MDA became aware of an incident involving one of the above devices, where the design feature initiated an unexpected change in pacing therapy, which could be inappropriate for certain patients. In the device concerned, failure analysis determined an internal component failure in the battery monitoring circuit. This resulted in inaccurate detection of the battery voltage, which was incorrectly sensed as low. This initiated asynchronous pacing and an increase in pacing rate by an additional 20ppm. The clinician concerned was unaware of the device feature.

The APC Medical E4162, E4164, E4165 and E416 pacemakers were designed and manufactured over 20 years ago and therefore clinicians may not be familiar with all the instructions for use, which may not be readily accessible. The design feature common to the above models is not widely used in modern external pacemakers, which incorporate different warning systems to alert users to low battery voltage or the presence of electromagnetic interference.

MDA has previously advised that some external pacemakers (including APC model E4162) are susceptible to interference from mobile communications systems 1,2,3 and care should be taken to ensure that patients supported via external pacemakers are not exposed to electromagnetic fields from mobile phones, walkie-talkies etc. MDA has also previously advised that older external pacemaker models should be withdrawn and replaced. 4,5 APC Medical advises that E4162, E4164, E4165 and E416 models have a 15-year service life expectancy and recommends their replacement at the end of that period.

Consideration should therefore be given to replacing the above models as soon as practicable. Risk managers are reminded of the Controls Assurance Standard - Medical Devices Management (Criterion 18)6, which addresses the replacement of medical devices in detail, extract as follows:

For both hospital and community devices, a stage is reached at which replacement must be considered. If any of the following seven criteria apply, the device is no longer serviceable:

  • Worn out beyond economic repair
  • Damages beyond economic repair
  • Unreliable (check service history)
  • Clinically or technically obsolete
  • Spare parts no longer available
  • More cost-effective or clinically effective devices have become available
  • Unable to be cleaned effectively prior to disinfection and/or sterilisation”


  1. DB 9702 Electromagnetic compatibility of medical devices with mobile communications.
  2. DB 1999(02) Emergency service radios and mobile data terminals: compatibility problems with medical devices.
  3. SN 2001(06) Update on electromagnetic compatibility of medical devices with mobile communications: TETRA (terrestrial trunked radio system) and outside media broadcasts from hospital premises.
  4. SN 9716 Model EV4542 and EV4543 external pacemakers.
  5. SN 2002(15) External pacemakers “ temporary cardiac pacing leads with shrouded connector pins: connection problems.
  6. Controls Assurance Standard - Medical Devices Management.


  • All clinicians who perform external pacing.
  • Supplies and risk managers.


  • Be aware that the above external pacemakers will revert to asynchronous mode pacing at a rate of approximately 20 ppm above the pre-set pacing rate, when either the battery voltage is low or electromagnetic interference is sensed.
  • Ensure that the above devices are not used for patients where a sudden increase in paced rate of 20 ppm, or a change from demand to asynchronous mode pacing, could compromise patient health.
  • Consider replacing the above pacemaker models (which were designed and manufactured over 20 years ago) as soon as practicable.
  • When the above external pacemakers are used, ensure also that mobile communication devices are not used in the vicinity, especially during patient transfer.


  • NHS Trusts (England) - Chief Executives
  • National Care Standards Commission - 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)
  • Directors of Anaesthetics
  • Supplies Managers
  • Medical Directors
  • Nursing Executive Directors
  • Accident & Emergency Departments
  • Risk Managers
  • Cardiac/Coronary Care Units
  • Cardiologists
  • Cardiac Surgeons
  • Adult & Paediatric Intensive Care Units
  • All Wards where external pacemakers are used
  • Catheter Laboratory Managers
  • Biomedical Engineering
  • Clinical Governance Leads


  • Headquarters (for onward distribution)
  • Hospitals in the Independent Sector


Details of supplier contacts, MDA contacts for technical and clinical aspects.Change of address or removal from address list for services registered under the Care Standards Act 2000.

Enquiries to the manufacturer should be addressed to:

Mr Gerry Burne
General Manager
APC Medical
68 Tewin Road
Haslemere Industrial Estate
Welwyn Garden City
Hertfordshire AL7 1BD

Tel: 01707 327 641
Fax: 01707 333 117

Enquiries to the MDA should quote reference number DEF/28/07/20021220.999-117 and be addressed to:

Technical aspects:

Dr Crina Cacou or Mr Peter M Solesbury
Medical Devices Agency
Hannibal House
Elephant and Castle
London SE1 6TQ

Tel: 020 7972 8338 / 8215
Fax: 020 7972 8106

E-mail:Crina.Cacou@doh.gsi.gov.uk Peter.Solesbury@doh.gsi.gov.uk

Clinical aspects:

Dr Jon Hopper
Medical Devices Agency
Hannibal House
Elephant and Castle
London SE1 6TQ

Tel: 020 7972 8126Fax: 020 7972 8111

E-mail: Jon.Hopper@doh.gsi.gov.uk

Change of address or removal from list for services registered under the Care Standards Act 2000.


NCSC Customer Service Unit
St Nicholas Building
St Nicholas Street

Tel: 0191 233 3556

Email: enquiries@ncsc.gsi.gov.uk


None required.

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