Advisories
Sigma Implantable Pulse Generators
Original Date of Advisory: November 2005
Potential Separation of Interconnect Wires
Product
A specific subset of Sigma series pacemakers may fail due to separation of interconnect wires from the hybrid circuit. Specific model and serial numbers of affected devices are available online at http://SigmaSNList.medtronic.com.
Advisory
This subset of Sigma series pacemakers that may fail due to separation of interconnect wires from the hybrid circuit may present clinically as loss of rate response, premature battery depletion, intermittent or total loss of telemetry, or no output.
Separation of redundant interconnect wires has been observed on hybrid terminal blocks. Device failure occurs only where both interconnect wires separate from a hybrid terminal block. In October 2005, testing and analysis identified the root cause of these failures and the affected population. Hybrid circuits used in this subset of devices were cleaned during manufacturing with a particular cleaning solvent that could potentially reduce the strength of the interconnect wire bond over time.
Our modeling predicts a failure rate from 0.17% to 0.30% over the remaining lifetime of these pacemakers. No provocative testing can predict which devices may fail.
Patient Management Recommendations
To assist physicians in their patient care and after discussion with physician consultants, Medtronic offers the following recommendations:
- Medtronic does not recommend replacement of these devices prior to normal elective replacement (ERI), based on the low probability of occurrence of a serious event in this population
- Continue routine follow-up in accordance with standard practice
- Advise patients to seek attention immediately if they experience return of symptoms (e.g., syncope or light-headedness)
- Determine whether device replacement is warranted on a case-by-case basis based upon consultation with patients, review of the individual patient’s medical history, and consideration of the relative risks of an invasive procedure
Status Update
The Sigma Family device performance related to the interconnect wires separation mechanism continues to be within Medtronic’s engineering projections. As of January 31, 2009, 213 devices out of approximately 40,000 devices worldwide have been confirmed as having experienced interconnect wire separation. Fifty-three (53) of these devices were returned from the United States.
One hundred fifty-eight (158) of the 213 devices (0.40%) were returned with information indicating a problem with the patient’s pacing system prior to explant. The remaining 55 devices (0.14%) were returned with no information indicating a potential malfunction while implanted or with insufficient information to determine the state of the device at explant. Lacking definite information indicating proper operation until explant, these devices are conservatively categorized as having experienced interconnect wire separation while implanted.
Implant duration for the 213 devices confirmed as having experienced interconnect wire separation has ranged between 17 and 83 months, with an average of 61.3 months.
Out of the initial advisory population of 40,000 worldwide, approximately 16,200 remain implanted. Approximately 3,900 of these are in the United States.
The Patient Management Recommendations set forth in the advisory remain unchanged.