ABT Abbott Laboratories

By Joseph Walker and Austen Hufford 

St. Jude Medical Inc. warned Tuesday that a battery malfunction could cause hundreds of thousands of its implanted heart defibrillators to quickly lose power and stop functioning.

Two patients died after batteries in their St. Jude-made defibrillators failed prematurely and prevented the devices from providing needed shock therapy, the Food and Drug Administration said in a separate safety advisory on Tuesday.

St. Jude, based in St. Paul, Minn., is in the process of being acquired by Abbott Laboratories in a cash-and-stock deal initially valued at $25 billion. The company does "not expect the medical advisory to have a material financial impact" on its financial results, a St. Jude spokeswoman said in a statement.

St. Jude shares were down 3.5% to $78.43 at 4 p.m., as Abbott shares fell 5.4% to $41.16.

"We continue to expect the transaction to close by the end of the year," Abbott spokesman Scott Stoffel said in an email.

St. Jude said the battery problem is a "rare occurrence" and that it is "working with regulators and physicians to communicate about this advisory and the resources we are providing to assist with patient management."

The potential for premature battery depletion affects nearly 350,000 patients globally who have implanted cardioverter defibrillators or cardiac resynchronization therapy defibrillators manufactured by St. Jude before May 2015, the FDA said.

The devices alert patients that batteries are running low by vibrating. When the devices are functioning normally, patients have three months to replace them after receiving the alert, the agency said. But the devices involved in the recall could stop working within 24 hours to a few weeks of patients receiving the alert.

"If the battery runs out, the [devices] will be unable to deliver lifesaving pacing or shocks, which could lead to patient death," the FDA said in its safety communication. "The patients most at risk are those with a high likelihood of requiring lifesaving shocks and those who are pacemaker dependent."

However, the frequency of device failure is low and most patients won't need to have their devices replaced early unless they receive an alert, the agency said.

Patients with the devices are being told to monitor them closely for battery failure and to contact their doctors if the device notifies them of a battery problem.

The implanted devices provide pacing for slow heart rhythms and electrical shock or pacing to stop dangerously fast heart rhythms.

The malfunction occurs when deposits of lithium form within the devices' batteries and create abnormal electrical connections, leading to battery failure. The problem was identified by medical researchers as far back as 2014, said Raj Denhoy, a Jefferies & Co. analyst. St. Jude resolved the problem with a new battery design in 2015, Mr. Denhoy said.

In addition to the two deaths, 10 patients have reported fainting from devices that didn't provide pacing because of battery depletion, and 37 patients have reported dizziness, the FDA said. So far, 841 devices have been returned to St. Jude for analysis due to premature battery depletion.

In recent months, St. Jude has been fending off allegations that its devices are vulnerable to hacking and other cybersecurity threats. St. Jude has denied the allegations and sued the short seller who released the report accusing its devices of having security holes.

Write to Joseph Walker at joseph.walker@wsj.com and Austen Hufford at austen.hufford@wsj.com

(END) Dow Jones Newswires

October 11, 2016 16:32 ET (20:32 GMT)

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