Monday, April 30, 2007

Defibrillator Lead Report Misleads

It didn't take long for the media to chew up this week's report on the high failure rate of old defibrillator leads published in Circulation from a single center registry from Germany today. What's better than to scare the heck out of patients? I mean, fear sells, doesn't it?

For those of you who haven't seen it yet, doctors from Germany decided to look back at their last 990 consecutive defibrillator lead implants between 1992 and 2005. They found 148 (15%) of defibrillator leads failed during follow-up and required replacement. They found that annual failure rates increased over time, peaking at 20% in 10-year-old leads.

But before you go out an insist that your defibrillator be removed, let's look at a few facts from the very same article:

  • 15% of the leads had problems, 85% of them did just fine.

  • No patent died as a result of ICD lead failure

  • Older lead materials that have since been show to have high failure rates are no longer used, but included in this report

  • The authors performed 95% of their implants using a subclavian approach, an approach they freely admit is prone to an unusually high level of lead "crush" as the lead passes between the first rib and clavicle. Like a coat-hanger repetitively bent, leads implanted by this approach are subject to a higher failure rate.
But the authors do make several valuable points: (1) defibrillators and their leads need constant monitoring, even after they are implanted and (2) in patients implanted for "primary prevention" of a cardiac arrhythmia (that is, they've never had an arrhythmia before the device is implanted), consideration of device failure over the lifetime of the patient should be considered when recommending a device for implantation.

It is important to note that the Heart Rhythm Society has been aware that these devices can be subject to malfunction on occasion. As such they have recommended that implantable cardiac defibrillators (ICDs) be evaluated every three months by a qualified physician. Further, most of the ICD manufacturers are developing wireless telemetry systems that can check these devices even as often as daily to assure their reliability. Furthermore, companies have migrated away from the form of polyurethane that can degrade when exposed to metal oxides (as occurred in leads manufactured before 1997). The fact that these older leads were included in the analysis serves to make the data more sensational and press-ready.

I would suggest that people evaluate the performance data maintained by each of the companies and published on-line. Boston Scientific's (formerly Guidant) performance data on their devices can be found here, Medtronic's here, St. Jude's here and Biotronik's can be found here. These data suggest current failure rates for most ICD's is approximately 10% after 10 years, fully one-half of that described by the authors in the above article. Certainly, this number is not perfect, but helps keep a reasonable perspective on defibrillator lead reliability, and reflects the world-wide experience of patient's with a particular lead or device system, and may be a more accurate reflection of lead trends across multiple centers and operators.


1 comment:

Anonymous said...

What's the alterative to subclavian placement?