Most surprisingly, the deaths were caused by electrical malfunction at high voltages — and not because of lead wires coming out of their insulation. The so-called externalized conductors were the main reason that the U.S. Food and Drug Administration slapped St. Jude (NYSE: STJ) with a Class I recall in December.
The findings of the study, whose manuscript was accepted for publication in the Heart Rhythmjournal, are bound to create a vexing issue for St. Jude, which has attempted to deflect the fear that externalized conductors might be a problem for its newer Durata family of leads. Specifically, the company’s CEO Daniel Starks has argued that Durata leads have a coatingthat is much more resistant to insulation abrasion. Others have argued that aside from the coating, the Durata is similar in design to the older generation of leads.
The study “Deaths Caused By the Failure of Riata and Riata ST Implantable Cardioverter Defibrillator, found that out of a total of 133 deaths reported in an FDA database, 71 involved Riata and Riata ST leads, with 22 of them caused by lead failure.
That’s 31 percent lead failure rate leading to death, compared with 8 percent (5 of 62 deaths) caused by Medtronic’s Sprint Quattro Secure leads. The fatalities involving Riata and Riata ST lead failure were caused most commonly by short circuits between high voltage components. When that kind of electrical malfunction occurred, the ICD failed to defibrillate.
None of the deaths was due to externalized conductors, one outcome of lead abrasion, although some of the Riata family of leads showed this problem.
Of the 141,000 Riata and Riata U.S. implants, approximately,79,000 remain active, the study noted. St. Jude voluntarily pulled the devices from the market in December 2010.
“Doctors need to place these patients on very close monitoring,” said Robert Hauser, one of the authors of the study and a senior consulting cardiologist at the Minneapolis Heart Institute. “We need to figure out what the predictors of the failure is.”
He noted that the short-circuit issue is still relatively rare, but added that compared to another high-profile lead recall involving Medtronic’s Sprint Fidelis family of leads, the Riata lead failure is more troubling.
“Sprint Fidelis was rarely associated with death; it was a low voltage issue,” Hauser noted. “This is a high voltage problem, which is more serious.”
In fact, the study is urging St. Jude to “conduct studies focused on the behavior of measurable electrical parameters prior to lead failure. Algorithms are needed that can detect electrical abnormalities before short-circuits occur.”
A St. Jude Medical spokeswoman said that “abrasion of silicone leads is acknowledged within the clinical community as a well-known clinical risk” and that led the company to develop the Optim technology which insulates leads making them several times more resistant to insulation abrasion than older, silicone-only defibrillation leads.
“We have three large ongoing prospective registries monitoring the performance of our Durata leads, which continue to demonstrate an abrasion free rate of 99.9%,” said Amy Jo Meyer, the spokeswoman in an e-mail. “The data from those studies is also being validated by PHRI, an independent research institute.”