Originally Published MPMN July/August 2007

SPECIAL FEATURE: IMPLANTABLES

The Great Battery Debate: To Recharge or Not to Recharge?

Batteries may seem trivial, but their use in implantable devices has some people in the industry all charged up.

Shana Leonard

When designing devices, OEMs often overlook the battery or treat it as an afterthought. But batteries are the components that will ultimately determine the size of an implantable device, as well as whether it will jump-start a patient’s heart for several months or several years. In addition to factoring in cost and real estate in the clamshell, manufacturers should consider what type of battery is best suited for an implantable application. This particular choice is not an easy one; major industry players are even at odds as to whether rechargeable lithium-ion batteries are preferable to finite primary batteries in electronic implantable devices.

Evaluation of energy density, cycle life, self-discharge, and calendar fade is essential when selecting a battery. Demonstrating favorable characteristics in these various categories, lithium-ion batteries are gaining momentum in the implantable device marketplace. Having developed a lithium-ion battery that it claims virtually eliminates calendar fade and self-discharge, Quallion LLC (Sylmar, CA; www.quallion.com)—manufacturer of the first FDA-approved lithium-ion battery ever implanted—is dedicated to persuading OEMs to employ lithium-ion rechargeable batteries in implants. Rechargeable lithium-ion batteries are increasingly replacing primary batteries in neurotransmitters and other energy-consuming implants.

But while enjoying success in the neurological implant market, lithium-ion batteries have yet to infiltrate the cardiac implant industry. Paul Beach, vice president of business development for Quallion, opines that “the big three” cardiac implant OEMs (Medtronic, St. Jude, and Guidant) opt to power their devices with primary batteries rather than lithium ion, which he says is done at the expense of patient comfort and reliability. The OEMs do, however, employ lithium-ion batteries for some of their neurological devices and medium-draw applications, which do not require the high rate of current in a short time period as demanded by cardiac implants.

Beach speculates that cardiac implant OEMs have not adopted the use of rechargeable batteries due to the crippling effect that it would have on revenue. ICDs and pacemakers typically have a life span ranging from 5 to 10 years, with an average of about 5 years. When the battery life has been significantly depleted, patients must undergo a surgical procedure to have the device replaced.

Devices powered by Quallion’s lithium-ion batteries have been approved in Europe for 25-year life. Beach argues that in his research, patients are much more keen on the concept of having one surgery every 25 years and recharging the device every 6 months or so than on having a device explanted and replaced every 5 to 10 years.

Opting for primary batteries over lithium-ion for cardiac implants is not a decision based on fear of lost revenue; rather, it stems from a concern for safety, according to St. Jude Medical (St. Paul, MN; www.sjm.com). The company ardently refutes Beach’s statements, emphasizing that patient safety is the company’s top priority when selecting components such as batteries for its devices.

“Patients with cardiac devices rely on those devices for lifesaving therapy, and any lapse in the battery’s viability puts patients at mortal risk,” says Kathleen Janasz, senior director of public relations and communications for the company. “Therefore, using a secondary-anode lithium rechargeable battery is unacceptable because its viability depends on patients intervening to recharge the battery. Should patients unexpectedly find themselves with an uncharged battery—their flight was delayed, the charger was lost, they got caught in traffic, they forgot to recharge it, etc.—they would be at risk.”

Medtronic (Minneapolis; www.medtronic.com) also staunchly defends its use of primary batteries and stresses its dedication to patient safety, first and foremost. “Medtronic’s proprietary, high-reliability lithium-ion technology is regularly explored for use in appropriate implantable applications,” the company says. “Further, an implanted device system is a complex electromechanical system that has mechanisms other than the battery that must remain functional throughout the device’s life span. It is critical to understand the reliability of the entire system beyond a typical 8- to 10-year implant life provided by the battery.”

But reliability is not guaranteed by using a primary battery, either, according to Beach. “The energy in a primary battery depletes just as that in a rechargeable,” he notes. “The question becomes: which chemistry is more amenable to indicating the remaining battery capacity at a given point in time? And in my opinion, the rechargeable chemistry can provide a much more reliable indication of remaining capacity than that of a primary chemistry.”

Extrapolating, Beach says that though a primary battery may have a predicted life of 10 years, the device may be explanted with half of the energy remaining in the battery as a precaution since there are no hard data to determine the remaining capacity and longevity is calculated through algorithms. In comparison, lithium-ion batteries have a predictable voltage curve, so capacity is easier to determine, he says.

This is not the case, according to Medtronic. Battery life is predictable to a point and is not just a guessing game. “The batteries used in both ICDs and pacemakers are specially designed to provide an appropriate time to allow for replacement without compromising patient safety,” the company avers. “This is called a battery depletion model, which supports a 3-month time from the point at which a battery starts to near the end of its useful charge to the need for replacement.”

Multiple replacement surgeries are not only a bane to patients, they’re also detrimental to the government, Beach claims. Factoring in the average number of cardiac devices implanted in patients each year, along with the average costs of ICDs and pacemakers, as well as the typical replacement cost for hospitals—part of which is picked up by the government since so many of these patients are on Medicare—Beach has calculated that multiple replacements caused by primary battery use are a major burden on the government. Using these figures, Beach found that if patients used 25-year-approved lithium-ion batteries instead of shorter-life primary batteries in these devices, by year 10, the U.S. government would save $250 billion a year.

“These are real numbers,” he says. “They put rechargeable pacemakers in people 30 years ago; this is not new technology. [Lithium-ion batteries] are implanted every day [in noncardiac applications]; they are FDA approved.”

“The big three” may not be sold on current lithium-ion battery technology for use in cardiac implants; however, they do acknowledge possibilities for the future. “St. Jude Medical’s research and development teams are continuing to improve battery technology,” Janasz says. “It is likely that, in the future, rechargeable batteries will be appropriate for implantable cardiac devices. At this time, rechargeable batteries are available in our neurostimulators to help patients manage chronic, intractable pain.”

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