People implanted with St. Jude’s now-recalled Riata defibrillator lead wires face risks from electrical shorts caused by a number of problems with the wires, according to a new study. The study, which was presented Monday at the American College of Cardiology meeting in Chicago and published online in the journal Heart Rhythm, also found that electrical malfunctions of the defective St. Jude Riata leads may have been responsible for as many as 22 additional deaths.
A defibrillator lead is a thin wire attached to the heart wall that delivers an electrical impulse via an implantable defibrillator. St. Jude recalled the Riata and Riata ST defibrillator leads last December, after it was discovered that the wires could potentially penetrate their insulation, compromising the device’s integrity. This could cause the defibrillators to inappropriately shock some patients, and at other times fail to deliver life-saving therapy when needed, St. Jude said.
At the time of the St. Jude Riata lead recall, two deaths and one serious injury had been linked to the faulty wires. In addition, one patient death and one serious injury in patients with protruding wires were reported, but St. Jude said that it was determined that those cases were not caused by the externalized conductors.
Now it appears that the problems with the Riata leads may go far beyond defective insulation. According to the Pioneer Press, the study presented Monday analyzed 105 reports on failed Riata wires and found that two-thirds had multiple defects, often up and down their length. According to lead researcher Robert Hauser of the Minneapolis Heart Institute, the analysis of data from the U.S. Food & Drug Administration’s (FDA) MAUDE database also found 22 deaths caused by Riata or Riata ST lead failure. However, Hauser said the “failures that have resulted in death…appeared to be caused” by short-circuiting unrelated to wires poking through their insulation.
According to a report in The New York Times, Hauser said he found that the silicone insulation on the Riata cables was breaking down and resulting in the electrical shorts. These electrical shorts were more serious than the wires protruding through their insulation, he said.
“When I went in, I thought I would find more deaths related to externalized cables,” he told the Times. “But as it turned out, the externalized cables really didn’t factor in.”
Hauser told The Wall Street Journal that the deaths alleged from Riata malfunctions were about nine times greater than a competing lead called the Quattro Secure made by Medtronic Inc.
According to the Pioneer Press, Hauser said one of the major problems with the Riata lead defects is that they are difficult to detect until a defibrillator patient experiences a serious event. That’s particularly concerning because the FDA has warned that surgery to remove the Riata leads may present higher risks than keeping them in. Hauser’s study found that eight patients had died during procedures to extract Riata lead wires.
“It’s an all-or-nothing situation. We are trying to figure out how to manage these patients, or a way to monitor them safely and effectively,” he said.
According to The New York Times, it is estimated that 79,000 patients in the United States and about 49,000 patients elsewhere have had either the Riata or Riata ST lead wires implanted.