Stretchable electronics to map the inside of the heart? It’s not from a movie

What if you could design a small piece of electronics that is both flexible and stretchable, is able to take high-resolution images of the electrical signals inside the heart, and cure a cardiac condition that impacts more than 35 million people worldwide? It may sound futuristic, but that’s exactly what NHLBI-funded researchers from Cornell are working on.

The heart is controlled by electrical signals that coordinate the contractions of its four chambers. When things go haywire, irregular heartbeats known as cardiac arrythmias, can occur. Atrial fibrillation, or AFib, is one type of arrythmia that makes the upper chambers of the heart contract much faster than normal. If left untreated, AFib can lead to serious, even life-threatening complications, like stroke or heart failure.

“With some cardiac arrythmias, a cardiologist will evaluate you and decide they can keep you on a medication to manage the condition, such as blood thinners or anti-arrhythmic drugs,” said Simon Dunham, Ph.D. assistant professor of electrical engineering in radiology at Weill Cornell Medicine and NHLBI-funded researcher. “But once they get to a place where they realize that it presents a significant enough risk, they need to treat the underlying arrythmia.” About 20,000 people in the U.S. fall into this category each year, he noted.

The limits of current treatments

The current standard of care to treat AFib is cardiac mapping and ablation. In this procedure, the first step is to insert a diagnostic catheter up through the groin, weave it through the blood vessels, and up into the heart. It sounds intense, but Dunham said it’s minimally invasive. “The prior version of cardiac mapping and ablation procedures used to require open heart surgery, so the current standard of care is already a massive improvement over the way we used to do it,” Dunham noted.

Once the catheter reaches the heart, the real work begins. Sensors on the catheter that contain electrodes collect electrical measurements from the tissues in the heart’s interior surface. As the catheter is moved around the heart’s chamber, it creates a detailed map of the electrical activity. With this map in hand, the cardiologist identifies the abnormal electrical activity and uses a second catheter to deliver a specific type of electrical energy to eliminate – or ablate – the heart cells that are misfiring, restoring a normal cardiac rhythm.

While this sounds promising, cardiac mapping has had a pretty meager success rate, with up to 60% of arrythmias reoccurring within a year of having the procedure. This is due to a simple fact: the electrical patterns in AFib are complex – so complex that researchers have been in constant search of technology that maps them most accurately.

With earlier technology, doctors could only collect the electrical signals one at a time as the sensor was moved around to map each section of the heart’s chamber. It was much like taking serial snapshots. What they needed was a panoramic photo to capture the full image – a simultaneous recording of all the electrical signals from each contraction.

Getting better, but not quite there

Enter basket catheters. With this next-phase technology, the electrode-containing sensors were embedded within a spherical cage of stiff metallic filaments at the end of the catheter. Though the basket catheter was able to fill the entire heart to simultaneously map the arrythmia, these devices had their own problems. The heart’s interior surface is complex, with pockets and crevices throughout. When the devices were inserted into the heart chamber, some sensors bunched in the crevices, generating too much data from one area and leaving large areas of the cardiac anatomy unmapped.

“It was like taking a coat hanger and trying to bend it and push it against something to conform to that shape,” Dunham explained. The devices were too rigid.

Hitting the sweet spot

One of the critical hurdles to overcome now is improving the detection of arrythmias in more complex atrial anatomies, explained Rahul Thakar, Ph.D., a program officer in the Advanced Technologies and Surgeries branch in NHLBI’s Division of Cardiovascular Sciences.

In 2021, capitalizing on NHLBI’s Catalyze program, Dunham and team used an NHLBI grant to develop what Thakar called “a novel solution.” The new technology builds on the basket catheter, but instead of being rigid, the cage is made with soft, medical-grade plastic that, after insertion, inflates like a balloon when filled with saline. The new design can stretch and flex to adapt to each patient’s unique anatomy.

Dunham explained that the device’s ability to inflate, even while holding its cage-like shape, allows blood flow throughout the procedure. “The mapping procedure is done in a very natural way where the patient is under anesthesia, but normal cardiac function happens throughout the mapping,” he said.

In the future, the researchers hope that this technology can be applied to other uses. For example, because the catheters can easily conform to different shapes and flex with each heartbeat, technology like this might have applications for a more complex arrythmia known as ventricular tachycardia, which occurs in the lower chambers of the heart. In mapping these arrythmias, cardiologists must consider how to avoid disrupting the mitral valve that connects the upper and lower chambers. Because the new catheters are so flexible, this may be the solution.

Dunham’s team also hopes to move more towards robotics, making it so the catheters can detect their own size and shape as they inflate, giving real-time information that could be used for clinical applications. These might include, for example, breathing tubes for intubation that can gently guide themselves down a patients’ airway.

Dunham and his team have been so successful in the development and testing phase, that they have just been awarded a Small Business Innovation Research (SBIR) grant from NHLBI. They can now move towards commercializing the new catheters to treat the more complex ventricular tachycardias.

“Our small business researchers have the potential to affect true change,” said Thakar. “The SBIR program is the actual embodiment of the money we spent on basic research. We can now take all of the knowledge that the testing and design phase has generated to move the research to the clinic and improve patient outcomes.”