MINNEAPOLIS _ Following deaths and injuries worldwide, Minnesota-based heart device-maker St. Jude Medical announced Tuesday that nearly 350,000 of its defibrillators implanted in patients may be prone to short-circuiting in a way that causes the device to fail unexpectedly.
Two deaths have been associated with situations where the devices failed to send lifesaving shocks to the heart, including one death in the U.S. In addition, 10 people have fainted and 37 more have reported dizziness after their defibrillators failed to keep their hearts beating in proper rhythm.
"While it is a rare occurrence (0.21 percent), we want to ensure we are providing the information physicians need to best care for their patients," a St. Jude spokeswoman said in an email regarding the rate of device failures. "We have asked physicians to contact their patients with information about this advisory. Device replacement is not recommended unless the physician determines otherwise."
Just hours before a Food and Drug Administration alert on the failures was published Tuesday morning, St. Jude announced that it had detected the potential for premature battery depletion in a wide swath of its implantable cardioverter defibrillators, or ICDs, and cardiac resynchronization therapy defibrillators, or CRT-Ds.
The at-risk models include various models of: Fortify, Fortify Assura, Quadra Assura, Quadra Assura MP, Unify, Unify Assura, and Unify Quadra devices. The defect has only been detected in devices made before May 2015.
Some defibrillators can also serve as pacemakers, and that function is disrupted by a battery failure as well. But the battery-failure issue does not affect St. Jude's stand-alone pacemakers, which are smaller devices that use lower-voltage batteries than the defibrillators.
An implantable defibrillator is a device capable of shocking the heart back into rhythm if its stops beating normally, but the therapy needs a powerful battery to work as intended. St. Jude defibrillators use lithium batteries, which is where the problem is.
During charging, the lithium material can form "clusters" inside the device that may cause a short circuit and lead to battery depletion, depending on the location of the cluster deposit. Battery depletion can happen in as little as one day after a low-battery alert, if a short circuit occurs.
"The patients most at risk are those with a high likelihood of requiring lifesaving shocks, and those who are pacemaker dependent," the FDA said in a safety communication Tuesday.
So far, 841 of the 398,740 devices sold worldwide have been confirmed to have premature battery depletion "in association with" lithium cluster formation, including 549 in the U.S. Forty-six of the devices had visible electrical shorting from the clusters.
Roughly 349,850 of the devices remain implanted in patients worldwide today and are at risk.
At this point, "prophylactic" replacements are not being recommended, as the risks of complications from replacement surgery are thought to be greater than the risk of premature battery failure. The FDA said most patients will not require a prophylactic replacement.
But devices should be checked and replaced immediately if a battery warning is detected. Such warnings are supposed to trigger a vibratory alert in the device that the patient can feel. Based on the circumstances, St. Jude may cover the cost of a replacement device, if one is needed, the St. Jude alert says.
The FDA and St. Jude recommended patients enroll in a service it calls Merlin@home, which can remotely monitor a device battery and send alerts if a problem is detected.
The FDA also said patients with St. Jude defibrillators should seek immediate medical attention if they feel lightheaded or dizzy, or if they lose consciousness, have chest pain or feel severe shortness of breath, all of which may be signs of a depleted battery.
St Jude stock dropped more than 3 percent in morning trading, to $78.57. The $22.4 billion medical device company, based in suburban Minneapolis, is in the process of being acquired by Abbott Laboratories in suburban Chicago.
An Abbott spokesman declined to say when Abbott became aware of the widespread battery issues, but it still expects to close its $25 billion acquisition of St. Jude by the end of the year.
The defibrillator battery warning is the second major hit to St. Jude devices in just over a month.
In late August, short-selling firm Muddy Waters Capital announced what it said were major cyber-vulnerabilities in St. Jude pacemakers and other implanted devices, based on vulnerabilities in wireless communication systems, including Merlin@home. St. Jude has since filed a defamation lawsuit and said the allegations are false.
Despite an initial dip in St. Jude's stock price, market analysts and independent cybersecurity researchers have said Muddy Waters' fears about cybersecurity may be overblown. The FDA has not recommended taking any action with regard to the cybersecurity allegations.
"The FDA will continue to monitor affected St. Jude Medical ICD and CRT-D devices for any adverse events related to premature battery depletion or cybersecurity vulnerabilities, and the agency will keep the public informed as new information becomes available," the FDA alert Tuesday said.
