The Incredible Disappearing Pacemaker

Medtronic has developed a unique approach to working with electronics that enabled it to make a pacemaker one tenth the size of its predecessor.

About nine years ago, Medtronic started a program called deep miniaturization, which ultimately led to the development of the tiny Micra pacemaker, which recently won CE Mark approval.

When the company's engineering team was first given the charge to develop an ultrasmall pacemaker, it quickly realized that its old product development approach was obsolete. “When we first started out, the leadership said: ‘We need our pacemaker to be one-tenth the size of the prior product,’” recounts Mark Phelps, senior program director, diagnostics and monitoring at Medtronic (Dublin, Ireland). Such a small device could be inserted directly into the heart with a catheter. “When they first heard about it, the engineering team said, 'Well, that is impossible.”

The team soldiered on anyway and came up with a more systems-oriented approach to product development. In the past, the engineering group was organized around device components. For instance, one group had focused on integrated circuit design, another on packaging of the electronics, another on the battery technology, another on the pacemaker’s leads, and so forth.

“In order for us to make a major breakthrough though, we decided that we can no longer afford to treat everything as a component and wire it together at the end,” Phelps says.

The team ended up rethinking the pacemaker from the ground up. “I think the breakthrough from a technological standpoint was building it as an entire system. Every component had to change and be fitted to optimize the overall space,” Phelps explains. “When you start over from scratch and don’t reuse any components, it ripples through every function. In terms of manufacturing, verification, and validation...all of the steps had to change.”

For instance, modelling for the device required blurring the lines between electrical and mechanical engineering. And then the company had to enlist new component suppliers because all of the device’s components were custom.

Ultralow Power Efficiency

The key thing enabling the device’s small size is its ability to function on ultralow power levels. “Our device when turned on, burns less power than many consumer devices turned off,” Phelps says.

When the team created the Micra and a related product, the Reveal LINQ insertable cardiac monitor, the engineers had to become comfortable working with levels of electric current in the nanoamp range.

The Micra had to work eight to 10 years on a single battery; the LINQ for three years. “If you think about it, both products are a computer that lasts from three to 10 years inside the body. We couldn’t afford to throw any power away,” Phelps says. “What people considered leakage currents in their integrated circuit designs we actually used.”

To create the integrated circuits to support such low levels of power, Medtronic had to partner with its integrated circuit manufacturers to redesign some of their processes to make the electronics as power efficient as possible. “We had to have a deep understanding of how our integrated circuit manufacturers’ processes worked. We had really good models to be able to design the integrated circuits.”

Phelps says the company's feedback it gave its electronics suppliers ultimately made those companies more effective. “We can see variation or any problems before anyone else does. We have become sort of a canary in the coal mine in spotting variation that no one else is looking at. That has enabled us to bring our contract manufacturers specific knowledge that helps them as well related to fairly low-volume to high-volume integrated circuit manufacturing,” he says.

Creating custom electronics for medical device applications can be an expensive proposition, requiring the development of components that are markedly different from those used in the consumer electronics field. “Most consumer electronics are trying to operate as fast as possible. But the human body is fairly slow in terms of the signal processing you need to do,” Phelps says. “We are sort of a different design space; we don’t need the speed to get to the very low power.”

Density

Creating a tiny pacemaker also requires devising highly dense electronics packaging. “All of our integrated circuits are all very thin and are stacked on top of each other and are packaged on a very dense module,” Phelps says. “It has wireless functionality, so we had to redesign or create our own wireless antenna, and that had to go inside the device but in a way where it is integrated.”

This density required by the device required remapping the geography of the device and making its components multifunctional. For instance, one end of the pacemaker’s wireless antenna serves as an electrode. The header with an antenna on it also has an electrode for the ECG signal. And the titanium can of the device includes a battery. On the other side of the battery is another electrode. “In terms of design, our battery and electrode are essentially built into the same can. We had to integrate not only the electronics but the rest of the mechanical and electrical components and couldn’t afford to have separate components; we had to combine them in the system,” Phelps explains.

This unique configuration enables the pacemaker to pack the same functionality and battery life as the prior product in a much smaller package.

As for the Reveal LINQ, it does everything its predecessor, the Reveal XT, did, but the LINQ adds wireless functionality. “They didn’t defeature the device to get to the size, which you might think you would have to do: What are you going to give up to get down to the size?” Phelps says.

The LINQ works with a bedside MyCareLink patient monitor. “Essentially, every night, the transmission goes through that bedside monitor up to our CareLink data management system. If it triggers an alert, it sends a report to the clinician so they can act on it. Without any interaction from the patient, the device can capture an event, send...the clinic those data. This allows for much quicker communication of any adverse events,” Phelps comments.

Reflecting on a New Approach

The protocol used to create the Micra and the LINQ is unique for a big medical device company. “From a big company standpoint, it is highly unusual. Most products are incremental from one product to the next. But for both Micra and LINQ, everything was created from scratch,” Phelps remarks. They essentially had zero reuse from prior products.”

Phelps believes that such new protocols are needed to help make the most of quickly evolving technologies. “We have to adopt these new techniques and capabilities to not only make the devices small but to simplify the procedures and make them less invasive,” he says.

“As we take on more of a global strategy and focus on economic value for our customers and patients, we have to leverage these new technologies. We have to think differently and continue to innovate to provide more of a systems solution for a broader less-specialized group of physicians.”

Regulatory strategy is also important. “I think the key is that regulatory groups are small compared to how many people are innovating in technologies,” Phelps says. “I actually think the companies that are leading have the responsibility ... to provide the right information that is effective to make good decisions. As you adopt the new technologies, you need to present the data and information in a way that can be effectively reviewed.”