MINNEAPOLIS _ St. Jude Medical Inc. said Tuesday that nearly 350,000 of its defibrillators implanted in patients may short-circuit and stop, a malfunction that may have killed two people.
Ten people have fainted and 37 more have reported dizziness after their defibrillators failed to keep their hearts beating in proper rhythm, the company said. At least one of the deaths was in the U.S., it said.
The defect was detected in devices made before May 2015.
The news sent St. Jude Medical stock down 3.5 percent in trading Tuesday, to a close of $78.41. A spokeswoman for the company, headquartered in suburban Minneapolis, said it takes the issue "very seriously" but did not expect a material financial effect.
An implantable defibrillator shocks the heart back into rhythm if it stops beating normally. It needs a powerful battery. St. Jude defibrillators use lithium batteries.
"We have identified a very small risk of premature battery depletion in a very small percentage" of implantable defibrillators, Mark Carlson, the company's chief medical officer, said via email. "While the risk that this will occur in an individual patient is very small, we are informing physicians about this issue so they can make the best clinical decisions for their patients."
Shares in Medtronic PLC, another major medical device-maker rooted in Minnesota, also fell, and some investment sites speculated that its heart products may be vulnerable to the same battery problem.
Medtronic declined to comment on its stock movement. A company spokeswoman said Tuesday that all lithium medical device batteries have the potential to fail in the way that St. Jude disclosed, but Medtronic was still evaluating St. Jude's findings.
"All high-power (defibrillator) devices from all manufacturers use lithium batteries; however we use a different battery" than St. Jude, Medtronic spokeswoman Kathleen Janasz said via email. She said the company routinely monitors the performance of its defibrillators.
St. Jude made the announcement in the hours before the Food and Drug Administration published an alert on the St. Jude device failures. It said the potential for premature battery depletion existed in a wide swath of implantable cardioverter defibrillators, or ICDs, and cardiac resynchronization therapy defibrillators, or CRT-Ds.
St. Jude's at-risk defibrillator models include various versions of its Fortify, Fortify Assura, Quadra Assura, Quadra Assura MP, Unify, Unify Assura, and Unify Quadra devices.
St. Jude set up a web link where patients can go to see if their devices are affected: https://www.sjm.com/en/patients/arrhythmias/resources-support/battery-advisory.
Some defibrillators can also serve as pacemakers, and that function is impacted by the issue. But the battery-failure issue does not affect St. Jude's stand-alone pacemakers, which are smaller devices that use lower-voltage batteries than defibrillators.
During charging, the lithium material in the defibrillator battery can form "clusters" inside the device that may cause a short circuit and lead to battery depletion, depending on the location of the lithium 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 called 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.
"We recommend that patients and their doctors work together leveraging available resources that include a built-in vibratory notification to the patient, remote monitoring, and in-office visits to ensure they understand the health of their battery. For many health care providers, these are already considered best practice in managing patients with implantable devices," Carlson said.
St. Jude, which has a market capitalization of about $22 billion, is in the process of being acquired by Abbott Laboratories in suburban Chicago.
An Abbott spokesman said St. Jude recently told Abbott that it was going to send out the battery alert. Abbott still expects to close its $25 billion acquisition of St. Jude by the end of the year. Abbott stock closed down more than 5 percent Tuesday.
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 and device-hacking group MedSec 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 rebutted the allegation and has since filed a defamation lawsuit. The FDA has not recommended doctors take any action with regard to the cybersecurity allegations.
On Monday night, Muddy Waters sent out a tweet saying an anonymous source had informed it that St. Jude would soon disclose that premature battery depletion had led to two deaths.
In its alert on the battery issue, the FDA also said it would monitor St. Jude devices "for any adverse events related to premature battery depletion or cybersecurity vulnerabilities."
St. Jude's Carlson also said the defibrillator battery issue was "completely unrelated to the false allegations made by Muddy Waters and MedSec, who are interested only in influencing the price of our stock for their own financial gain."
