February 11, 2005 - Medtronic, Inc., today said it is voluntarily advising physicians about a potential battery shorting mechanism that may occur in a subset of implantable cardioverter-defibrillator (ICD) and cardiac resynchronization therapy defibrillator (CRT-D) models. In a letter to physicians, Medtronic reported that nine batteries (0.01 percent, or approximately 1 in 10,000) have experienced rapid battery depletion due to this shorting action. If shorting occurs, battery depletion can take place within a few hours to a few days, after which there is loss of device function. There are no reported patient injuries or deaths.
Devices with batteries manufactured between April 2001 and December 2003 may exhibit this shorting action. Potentially affected models are the Marquis VR/DR and Maximo VR/DR ICDs and the InSync I/II/III Marquis and InSync III Protect CRT-D devices. Approximately 75 percent of these devices were implanted in the United States. Patients with other models of Medtronic devices or these device models with batteries manufactured after December 2003 are not affected.
As part of the company's program to analyze products returned from physicians, Medtronic identified nine of 87,000 implanted devices (0.01 percent) with a battery design that exhibited this shorting mechanism. Based on highly accelerated company testing, Medtronic estimates that this rate may increase to between 0.2 percent and 1.5 percent over the second half of device life.
ICDs shock or pace the heart into normal rhythm after patients suffer rapid, life-threatening heart rhythm disturbances originating in the lower chambers of the heart that can lead to sudden cardiac arrest (SCA). CRT-Ds can also provide electrical pulses to the heart's two lower chambers to improve heart failure symptoms. An ICD or CRT-D device is surgically implanted in the chest in a procedure typically lasting one to two hours.
"We were able to identify this possible risk through our stringent product testing," said Steve Mahle, president of Medtronic Cardiac Rhythm Management. "Even though the potential for rapid battery depletion is extremely low, we see it as our obligation to alert all implanting physicians to the potential issue and provide ways to help them and their affected patients successfully manage the situation."
Medtronic began notifying physicians about the situation on Feb. 10, providing them with a list of potentially affected patients and recommending that physicians communicate with those patients and follow them closely. Medtronic is communicating this information so that physicians are aware of the potential issue and can manage it as they feel is appropriate with their individual patients.