- Medicines and Healthcare products Regulatory Agency
- 15 March 2007
- Alert type:
- Medical device alert
- Medical specialty:
- Cardiology, Critical care, and Vascular and cardiac surgery
(Boston Scientific Ltd.) patients may experience extended charge times in the middle-of-life phase of the device, which could lead to a delay in shock delivery; also replacement and end of life indicators may display earlier than expected. (MDA/2007/023)
15 March 2007 at 11:45
Action deadlines for the Safety Alert Broadcast System (SABS)
Deadline (action underway): 16 April 2007, Deadline (action complete): 18 June 2007
Boston Scientific Ltd:
Vitality and Assure implantable cardioverter defibrillator (ICD) families and Contak Renewal cardiac resynchronisation therapy defibrillator (CRT-D) families (see Appendix 2 for full details of models affected)
- Delay in delivery of therapy during device middle-of-life phase due to temporarily extended charge time limits.
- Transition to device end of life (EOL) without prior observation of elective replacement indication (ERI) even though battery capacity remains available.
The MHRA has received 31 reports of early explants from four of the above device models (1870, 1871, 1872, A135) during the middle-of-life (MOL) phase. Replacement has been due to observation of premature elective replacement / end of life indicators (ERI/EOL), caused by long capacitor charge times. The MHRA has also become aware of confusion about ERI/EOL indicators throughout implant duration.
Incident reports have included devices displaying:
- extended charge times where no replacement / end of life indicators have been observed
- ERI where charge times have extended beyond 26 seconds giving rise to potentially inappropriate therapy delay for some patients
- EOL indicators with charge times in excess of 30 seconds without ERI being observed in the first instance.
Boston Scientific ICDs / CRTDs are designed to regularly monitor both battery voltage and capacitor charge time, and flag ERI when specified limits are exceeded. Charge time ERI is flagged whenever two charges (capacitor reform or therapeutic shock) occur within a 24hr period in which both exceed the specified limit.
Increase in charge time (due to a rise in battery impedance) is an expected behaviour of ICDs that have lithium-silver-vanadium-oxide batteries. However, early batteries used in some of the above models have a tendency to exhibit a more exaggerated increase in battery impedance during the MOL phase, due to a battery manufacturing anomaly.
Boston Scientific has confirmed that the above models have been programmed with temporarily extended ERI charge time limits during the MOL phase (compared to unaffected models). This is to prevent premature tripping of ERI due to the battery impedance characteristic.
In January 2007, Boston Scientific issued a product update about this issue via their website. The company issued a more detailed and informative product update about this problem in March 2007.
The MHRA is issuing this Medical Device Alert to ensure that all UK clinicians who implant these devices, or manage patients already implanted with these devices, are aware of Boston Scientific’s communication and can therefore consider the clinical implications of long charge times that may be inappropriate for some patients.
Identify patients implanted with these devices, asses clinical risks associated with the above device problems, and follow the actions on page 2.
- Be aware of:
- extended capacitor charge times during device MOL phase, as documented in the most recent Boston Scientific product update (see the MHRA’s website for March 2007 issue)
- the higher prevalence of long charge times in earlier manufactured devices (see Appendix 2 below)
- the potential for earlier manufactured devices to pass from ERI to EOL in less than three months.
- At the next scheduled follow-up, review capacitor charge time history and evaluate the appropriateness of charge time according to patient condition and device dependency, giving priority to those who have not been followed up within the last three months (see Appendix 1 below).
- Consider the risks (infection etc) and benefits of elective device replacement where capacitor charge time is judged to be inappropriate for an individual patient.
- Consider scheduling future patient follow-ups at three monthly intervals – where the device is around MOL, to increase the likelihood of detecting longer charge times, early ERI and/or EOL as appropriate.
- Consider programming the ‘Beep When ERI is Reached’ feature to ‘ON’ (default) for all affected patients.
- Remind patients to contact their follow-up centre immediately if they hear beeping from their device and/or experience arrhythmias/resumption of symptoms that remain uncorrected by the device.
- Consult the Boston Scientific website for future related product updates.
- Report all instances of device failure to the MHRA and Boston Scientific.
- Report explants to the National Pacing and ICD Database (see contacts on page 3).
All cardiologists, cardiothoracic surgeons and cardiac physiologists who implant any of these devices or manage patients implanted with them.
Please bring this notice to the attention of all who need to know or be aware of it. This may include distribution by:
SABS liaison officers for onward distribution to all relevant staff including:
- A&E departments
- Cardiac physiologists
- Cardiology departments
- Cardiology nurses
- Cardiothoracic departments
- Cardiothoracic surgeons
- Cardiothoracic surgery directors
- Clinical directors of cardiology
- Clinical governance leads
- Coronary care units
- Directors of nursing
- Medical directors
- Risk managers
Healthcare Commission (CHAI) to:Headquarters for onward distribution to:
- Hospitals in the independent sector
Enquiries to the manufacturer and the National Pacing and ICD Database respectively should be addressed to:
Ms Jayne Puckeridge, Regulatory Affairs Manager
Boston Scientific Ltd
Hampshire International Business Park
Crockford Lane, Chineham
Hampshire RG24 8WH
Tel: 01256 374 010
Fax: 01256 374 014
National Pacing and ICD Database
PO Box 9205
Bridge of Weir
Tel: 01505 612 829
Fax: 01505 612 829
Enquiries to the MHRA should quote reference number 2006/008/002/291/009 and be addressed to:
Mr Peter M Solesbury or Ms Hazel Randall
Medicines & Healthcare products Regulatory Agency
1 Nine Elms Lane
London SW8 5NQ
Tel: 020 7084 3215 / 3287
Fax: 020 7084 3106
Medicines & Healthcare products Regulatory Agency
1 Nine Elms Lane
London SW8 5NQ
Tel: 020 7084 3126
Fax: 020 7084 3111
Change of address or removal from address list for Healthcare Commission:
103-105 Bunhill Row
Tel: 020 7448 0842
How to report adverse incidents
Incidents relating to medical devices must be reported to the Medicines and Healthcare products Regulatory Agency (MHRA) as soon as possible.
Further information about reporting incidents; online incident reporting facilities; and downloadable report forms are available from MHRA’s website (http://www.mhra.gov.uk).
Alternatively, further information and printed incident report forms are available from:
MHRA Adverse Incident Centre
Medicines and Healthcare products Regulatory Agency
Market Towers, 1 Nine Elms Lane
London SW8 5NQ
Telephone 020 7084 3080 or Fax 020 7084 3109 or e-mail: firstname.lastname@example.org(An answerphone service operates outside normal officer hours)
Medical Device Alerts are available in full text on the MHRA website:http://www.mhra.gov.uk
Further information about SABS can be found at www.info.doh.gov.uk/sar2/cmopatie.nsf
Appendix 1 to MDA/2007/023
Aspects of device behaviour to be considered during patient follow-up, when assessing the appropriateness of patient exposure to extended capacitor charge times:
- ERI capacitor charge times differ at beginning of device life and during/after MOL.
- Extended capacitor charge times can occur during MOL without programmer ERI indication.
- ERI will not ‘flag’ until two consecutive charge times in excess of the extended charge time limit occur within a 24 hour period (or when battery voltage falls to the battery ERI value).
- EOL will not ‘flag’ until a single charge time greater than 30 seconds occurs.
- Transition to EOL may in some instances appear rapid and may occur without display of programmer ERI indication.
- Device MOL occurs:
- when battery voltage is between approximately 2.52V and 3.00V
- typically between 24-38 months however, occurrence is dependent on device usage.
- Devices that trigger charge time-based ERI/EOL have several months (and in most cases more than one year) of remaining battery capacity. During this time ERI/EOL therapies are available (as per device manuals/labeling) as well as maximum energy shocks, bradycardia pacing and left ventricular pacing (according to device type).
- Extended ERI charge time design specifications and expected charge time performance are not documented in the current instructions for use.
- Where ‘Beep When ERI is Reached’ is programmed ON – 16 R-wave sync tones will be emitted from the device every 6 hours when ERI is reached. Other warning tones will require investigation of other related warning conditions.
Notes: (1) See also ACTION on page 2. (2) Refer to the MHRA’s website (http://www.mhra.gov.uk) to access the Boston Scientific March 2007 product update. (3) Refer to the ‘Product Updates’ area of the Boston Scientific website (http://www.guidant.com) for future revised model listings and ERI extended charge time limits.
Appendix 2 to MDA/2007/023:
See attachment for table of affected models and projected rate of display of replacement indicators during the MOL phase
Issued: 15 March 2007
Alert type: Medical device alert