INNOVATION

This Wearable ‘Heart Sock’ May Someday Save Lives

Inventors say a new device can detect irregularities and even intervene before heart attacks turn deadly

March 10, 2014

Heart Sock — This "heart sock" is dotted with sensors that can detect the intricate inner workings of the heart. Credit University of Illinois and Washington University

There's a lot of buzz around wearable electronics these days—Google, for instance, is expanding into the eyewear business, while other companies are scrambling for their share of the market with high-tech clips and watches that track what you eat and how you move.

But none of them are remotely like what John Rogers, the 2013 Smithsonian American Ingenuity award winner in physical sciences, is developing. His device, you see, is engineered not only to fit like a glove, but also perhaps someday save the wearer's life.

The materials scientist, along with his team of students at the University of Illinois at Urbana-Champaign, have successfully tested what's best described as a sock for the heart. The device, fitted over the entire surface area of the heart, is comprised of a series of sensors to monitor, with uncanny precision, the inner workings of this most vital organ. If it detects a troubling abnormality, it can relay data to medical professionals; in an emergency, such as during a heart attack, it could even intervene by administering an electrode-induced pulse.

Normally, the heart pumps in a manner that's so efficient we hardly notice it working. But for those with heart rhythm conditions, out-of-sync heart contractions can be debilitating—causing lightheadedness, weakness, vomiting and chest pain, for those with arrhythmia—or, in some cases, deadly. Over time, rhythmic irregularities can cause blood clots (which sometimes lead to strokes) and, in extreme cases, cardiac arrest.

Doctors can usually prescribe medication to correct these sorts of issues. But in some instances, patients must turn to surgical interventions such as pacemakers or defibrillator implants. And while those devices work sufficiently enough, the mechanism they use to regulate a person's heartbeat is actually quite crude. With defibrillator implants, a pair of electrodes is positioned inside the heart chamber. Whenever a life-threatening arrhythmia is detected, the defibrillator sends an electric shock that stuns the heart back into a normal rhythm. The problem with that approach, Rogers says, is that activity from another region of the heart can, by mistake, trigger a painful jolt when there isn't really a need for it.

Rogers' device encloses the heart in a much more sophisticated sensory system that can pinpoint exactly where a rhythmic irregularity occurs. In a sense, it functions like the nerve endings on a secondary skin.

“What we wanted was to harness the full power of circuit technology," Rogers says of the device, which is two and a half years in the making. "With a lot of electrodes, the device can pace and stimulate in a more targeted fashion. Delivering heat or pulses to specific locations, and doing it in measurable doses that are just sufficient enough, is important because applying more than necessary is not only painful but can damage the heart."

creation of heart sock — This step-by-step diagram illustrates how the heart device was created. University of Illinois and Washington University

Besides its potential as an emergency cardiac implant, the heart sock's elasticity allows for an array of other electronic and non-electronic sensors that can monitor calcium, potassium and sodium levels—considered key indicators of heart health. The membrane can also be programmed to track changes in mechanical pressure, temperature and pH levels (acidity), all of which could help signal an impending heart attack.

To fabricate the prototype sheath, the researchers first scanned and 3D printed a plastic model of a rabbit's heart. They then arranged a web of 68 tiny electronic sensors over the mold, coating it with a layer of FDA-approved silicone rubber material. After the rubber set, Rogers' lab assistants peeled off the custom-prepared polymer.

To test the membrane, researchers wrapped it around a real rabbit heart, hooked up to a mechanical pump. The team engineered the device to be a tad bit smaller than the actual organ to give it a gentle, glove-like fit.

"The tricky thing here," Rogers says, "is that the membrane needs to be sized in a way that it can create just enough pressure to keep the electrodes in sufficient contact with the surface. Pressing too hard will cause the heart to respond in a negative way."

"It needs to fit just right," he adds.

As Michael McAlpine, a mechanical engineer at Princeton University who was not involved in the research, told The Scientist: "What’s new and impressive here is that they’ve integrated a number of different functionalities into a membrane that covers the entire surface of the heart. That spread of sensors provides a high level of spatial resolution for cardiac monitoring and offers more control when it comes to stimulation."

So what will it take for this breakthrough to go from lab to patient? Rogers estimates at least another decade of development before something could be ready for the medical market. In the meantime, he plans to continue collaborating with Washington University biomedical engineer Igor Efimov to refine the proof-of-concept into a practical, safe and reliable technology.

One major obstacle is figuring out how to power the membrane without conventional batteries. Currently, Rogers and his team are exploring a few alternatives, such as ultrasound charging, a method in which power is transmitted wirelessly through skin, as well as using piezoelectric materials that capture energy from the surrounding environment. For the latter, there's some precedent for success. Two years ago, engineers at the University of Michigan harnessed such materials to develop a pacemaker powered solely by its user's heartbeat.

"Since we're trying to incorporate a lot more sensors, as well as deliver electrical impulses and heat, it's going to take more energy than the amount generated for conventional pacemakers," Rogers says. "In the future, we're hoping we can improve the efficiency."

Another crucial element is homing in on a way to send data to an external gadget so patients and specialists can access it. Right now, the sensors record things like changes in temperature and PH, among other patterns, but scientists have yet to figure out a way to deliver that data wirelessly.

"Bluetooth communication is low-powered, so we're looking at that," Efimov says. “Basically, the device will require more components and we'll need experts in other fields like electronics, telemetry and software. So ultimately, we're going to have to raise venture capital and start a company."

Right now, the focus is making the sleeve work as a practical device; there's no telling how much it will cost to produce, or, how much it will cost consumers when it comes to market.

The big question, though, is ultimately whether the heart sock will function safely and effectively in vivo, or in actual living test subjects. Pacemakers can typically last 10 years. So, to be practical, Rogers' invention would also have to demonstrate it can stay operational for at least that long. The team is preparing to take that next step with a pilot that will test the membrane inside a living rabbit, a test they hope to complete with funding from the National Institutes of Health, along with other grants they're working to secure. If everything goes well, the next test of whether the gadget is up to snuff will be on humans.