Danger of Medtronic's Sprint Fidelis ICD lead is increasing, scientists warn
This article was originally published in Clinica
The Sprint Fidelis heart lead, which was withdrawn from the market by its manufacturer, Medtronic, in October 2007, may be even more dangerous than previously thought.
A study published online in Heart Rhythm on February 23 suggests that the lead may be failing in patients at a rate significantly higher than previously known.
Robert Hauser and David Hayes of the Minneapolis Heart Institute and the Mayo Clinic in Rochester, both in Minnesota, assessed the health of all patients implanted with all types of transvenous implantable cardioverter-defibrillator (ICD) leads at the two hospitals between January 2004 and December 2008. In total, 3,037 ICD leads were implanted, 848 of which were Sprint Fidelis leads.
The researchers found that 94 defibrillator leads failed in total, and 72 of these were Sprint Fidelis leads. The Sprint Fidelis failure rate was significantly higher, at 3.75% per year, than the 0.58% per year seen with the other leads in the study. The three-year estimated survival rate was also significantly lower with Sprint Fidelis, at 87.9%, compared with the 98.5% rate of the other leads.
Drs Hauser and Hayes wrote: "The cumulative hazard of Sprint Fidelis failure was significantly greater compared with the 2,189 other defibrillator leads, and the hazard of Sprint Fidelis failure accelerated after the first year and continued to increase during the study."
Furthermore, the chance that a Sprint Fidelis lead would last another year intact decreased progressively during the study. 63 Sprint Fidelis failures (87.5%) were caused by pace-sense conductor fracture, causing inappropriate shocks in 36 of the 72 patients whose Sprint Fidelis leads failed.
Around 268,000 patients had been implanted with the lead before it was recalled by Medtronic. Many of these patients still have their leads in place, because of the risks attendant on the prophylactic surgical removal of the devices. Despite these risks, physicians will now have to seriously consider replacing the Sprint Fidelis leads in patients who still have them, as this study shows the increased danger of the devices.
Drs Hauser and Hayes concluded: "The hazard of Sprint Fidelis lead failure is increasing, while the failure rates of other defibrillator leads are low and stable. Physicians should consider these data when managing patients who have Sprint Fidelis leads."
88% or 96%?
Intriguingly, Medtronic has alternative statistics. On February 2, the firm posted data on its website claiming that the lead's three-year survival rate averaged 96.2%, rather than the 87.9% found by Drs Hauser and Hayes.
Medtronic has two sources for its data: its System Longevity Study (SLS), and CareLink, a patient monitoring system. The CareLink and SLS data show three-year survival rates of 97.0% and 95.4%, respectively, giving an average of 96.2%.
In January, all the lawsuits filed by patients who were fitted with Sprint Fidelis leads were dismissed by Judge Richard Kyle, who ruled that devices which were already FDA-approved were exempt from litigation. However, this ruling is controversial as it was subsequently revealed that the judge's son, also called Richard Kyle, works for a legal company that has Medtronic as a client.