Sometime next week, we should be receiving software, called the "Lead Integrity Alert" that can be uploaded into existing Medtronic implantable cardiac defibrillators (ICDs) to help detect lead fractures from the recalled Sprint Fidelis (Model 6949) defibrillator leads. This software was approved by the FDA today and can be uploaded into the Medtronic's Marquis, Maximo, Virtuoso and Concerto ICD models non-invasively during a routine office visit. It is thought that such programming changes can reduce the number of patients who receive an inappropriate shock from a lead fracture before it is explanted by 38 to 40%. While not perfect, it might alert both the patient and physician earlier to a avoid unnecessary shocks should a lead fracture.
How the Software Works
There is a so-called Sensing Integrity Counter that usually trips an alert if there are greater than 300 counts of non-physiologic sensed intervals by the device. This software will lower this number to 30 or more to trigger an alert. Further, if there are an excessive number of very short "non-sustained ventricular tachycardia" sensed intervals, this also could trigger an alert. The software also allows an automatic adjustment of the "number of intervals to detect" to be automatically incremented to the next-higher detection ratio in hopes of averting a shock, while beeping six times a day (rather than once) to improve the chances a patient will notice the new alert state if tripped.
What to Do
Patients with the advisory leads will have the software automatically installed during their next routine office device check, but those who want it installed earlier should contact their doctor and inquire if the software could be installed earlier.
Realize this software only affects Medtronic ICDs. St. Jude and Boston Scientific devices are NOT affected.
11 Sep 2008 Update: Medtronic's Info on the Lead Integrity Alert.