Lead integrity alert algorithm linked with decrease in inappropriate shocks from ICD leads

Kallinen L. Heart Rhythm. 2010;7:1048-1055.

The use of lead integrity monitoring software was associated with an improvement in the number of inappropriate shocks delivered to patients implanted with Medtronic’s Sprint Fidelis implantable cardioverter defibrillator leads, results from a study suggested.

The Sprint Fidelis leads were formally recalled by the manufacturer in October 2007 after reports of lead failures. The manufacturer sent safety advisories to more than 250,000 patients and their physicians regarding the recall and continued impedance monitoring of patients who had received the leads. Although researchers had studied the use of audible alerts intended to identify impending lead fractures, the results of their studies suggested that the alerts did not reliably forewarn patients of impending fracture, nor substantially reduce inappropriate shocks to the patients. After the release of lead integrity alert software by the manufacturer in August 2008, researchers for the current study sought to evaluate an algorithm-based alert system.

Researchers for the single-center study included patients who had received Sprint Fidelis high-voltage ICD leads, which are prone to fracture, at the Minneapolis Heart Institute. Two models of the leads (6949 and 6931) were included for analysis.

Fifty-two (11.3%) of 461 leads failed in the study population between October 2004 and January 2010, with an annual failure rate of 3.6%. Fracture of the pace-sense conductor occurred in 49 of the 52 lead failures (94.2%); the remaining three device failures affected high-voltage conductors. The average time to lead failure was 34.2 ± 12 months.

Inappropriate shocks, according to the researchers, were the first indication of lead failure in more patients without the lead integrity alert software (n=18, 69%) vs. those with the lead integrity alert software (n=4, 17%; P=.0004). The patients who received inappropriate shocks and who did not have the lead integrity alert software had an average of 13.2 ± 13.6 shocks vs. those with the lead integrity alert software (3 ± 2 shocks, P=.017 for comparison). In addition, the audible alert was effective in 70% of patients with the software and 36% of those without the software and whose audible alerts were programmed ON (P=.053).

“The audible alert is problematic for some patients, and manufacturers should improve the ability of ICDs to automatically recognize device problems and to notify caregivers without delay,” the researchers wrote. “Patients who have Sprint Fidelis leads should have lead integrity alert monitoring.”

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