Circ: Consider replacing Fidelis leads during generator replacement
David H. Birnie, MD, of the University of Ottawa Heart Institute in Ontario, and colleagues in the Canadian Heart Rhythm Society Device Committee estimated that 268,000 Fidelis leads have been implanted in patients globally. In Canada, the Sprint Fidelis lead (Medtronic) was approved in 2004, but Medtronic suspended distribution in Oct. 15, 2007, after reports of early lead failure rates. Single center studies have shown an increase in failure rates, but findings have been variable.
Birnie and colleagues determined that a large, multicenter study of lead failure data was warranted to help physicians and patients make decisions about lead replacement. They noted that all 23 centers that perform implantable cardioverter-defibrillator (ICD) procedures in Canada participate in the Canadian Heart Rhythm Society Device Committee, providing a rich dataset for analyses.
For this study, the researchers stratified centers into high and low failure rate centers and selected the median and randomly five from each strata for a follow-up of half of the Fidelis leads implanted in Canada. Only Fidelis leads implanted in the 11 selected centers were included in the analyses. They abstracted clinical and device interrogation data from the ICD databases as well as patient data from other clinical records.
Within the 11 centers, they identified 3,169 Fidelis leads implanted between Dec. 16, 2003, and Nov. 9, 2007, with a total of 251 failures. Of the 3,169 Fidelis leads, 81.6 percent were model 6949, dual coil active fixation leads. Model 6931, single coil active fixation leads, accounted for 12.3 percent of the total, and model 6948, dual coil passive fixation leads, another 5.9 percent. Model 6930, dual coil passive fixation leads, captured only 0.2 percent of the total.
Overall, the one-, two-, three-, four- and five-year lead failure rates were 0.2 percent, 2.1 percent, 5.3 percent, 10.6 percent and 16.8 percent, respectively. In model 6949, for those five years, the failure rates were 0.2 percent, 1.8 percent, 4.7 percent, 9.9 percent and 16.6 percent, respectively.
“The failure rate in this study and other reports is higher than Medtronic has reported from their own data,” the authors noted. “This is possibly explained, at least in part, by variable center failure rates and perhaps bias toward reporting data from centers with higher rates. In the current study we controlled for this by selecting centers from high and low strata of failure rate.”
They added that Medtronic’s largest post-market studies are from the U.S., and patient differences between the two countries could also be a factor.
Birnie and colleagues found four independent predictors of failure. Female patients were at higher risk, as were patients who underwent axillary and subclavian access. Additionally, previous lead failure also was a predictor of subsequent Fidelis failure.
“Lead access via the subclavian vein (compared to cephalic access) was one of two independent predictors of lead failure with an odds ratio of 3.47,” the authors wrote. “[D]ata from our study suggest that the debate about the relative value of cephalic versus non-cephalic access should be revisited.”
Of the total cohort studied, the Fidelis lead was not implanted as the first device surgery in 406 patients, they found. That subgroup accounted for 38 of the subsequent Fidelis failures, and 44.7 percent of those 38 patients had had a previous lead failure.
“These data support the widespread anecdote that there are a group of patients, whom for unknown reasons, have recurrent ICD lead failures,” the researchers observed. “The explanation is unclear but needs further investigation; however, it should be noted that in this high-risk subgroup, cephalic vein access still significantly reduced the hazard of recurrent failure. This suggests that after an initial non-cephalic lead failure, replacement leads ideally should be inserted via the cephalic vein if possible.”
Birnie and colleagues suggested that their findings can be used to project the risk of Fidelis lead failure. At five years, the generator may have reached its replacement time, they wrote. They calculated that if the rate of failure plateaus at five years at 6.2 percent, then the risk of failure would be 23.7 percent. They pointed out that if the failure rate continues to increase, then the risk of failure will be higher than 23.7 percent.
“Our data suggest that Fidelis replacement should be strongly considered in most patients at the time of generator replacement,” they concluded.