Improving the Odds for Patients with Atrial Fibrillation

Atrial fibrillation, or AF, is the unpredictable musician throwing the symphony of the heart out of whack, causing the upper chambers to beat haphazardly, out of sync with the steady rhythm of the lower chambers. 

And unfortunately, AF is all too common, affecting one in 100 people. It can be brief or persistent. It can wear you out, leaving you dizzy and out of breath, causing chest pains and palpitations. By itself, AF usually isn’t life-threatening, but it reduces the heart’s efficiency and can lead to blood clots and strokes — which definitely are life threatening. 

“There are some helpful treatments for AF, but they are suboptimal,” said Yue Chen, assistant professor of biomedical engineering in the Coulter Department, where he runs the Biomedical Mechatronics Lab. “For too many patients, the treatment is incomplete.”

Treatments like radiofrequency ablation (RFA), for example, have proven effective.  A catheter delivers radiofrequency energy to create scar tissue inside the heart. Scar tissue can’t conduct electricity, so it blocks AF’s abnormal signals, restoring normal rhythm to the heart. But 30-50% of patients have a recurrence of symptoms.

It’s partly because controlling the surgical tools inside the heart’s complex environment isn’t easy. The idea is to create a continuous line of lesions without any gaps, to completely block the faulty electric signals. 

“Sometimes, there are gaps,” said Chen, who aims to close them, and he’s using a National Science Foundation CAREER Award to find a solution. Chen and his collaborators are developing a continuum robotic system that can efficiently perform procedures like RFA while the patient is inside a magnetic resonance imaging (MRI) scanner. 

“This CAREER Award means a lot to me and my lab,” said Chen, one of three Coulter BME faculty members, with Ming-fai Fong and Ahmet Coskun, to win the honor this year. 

“I’m honored that my past work as well as my future research visions are being recognized,” he added. “This is a great opportunity for us to explore some new directions — MRI-safe continuum robots. Our goal is to develop robot-based medical interventions for improved treatment outcomes.”

Smart Snake

Continuum robots are long and slender and made of flexible materials that allow them to bend and twist and move with a great deal of dexterity, like a snake. 

“It makes them perfect for minimally invasive surgeries, such as cardiac ablation, intracerebral hemorrhage removal, drug delivery, and many other procedures,” Chen said.

But that’s not what makes the Chen team’s system unique. Unlike traditional robotic systems, this one is designed to work inside an MRI machine, offering doctors more precision than ever. 

MRI provides high-resolution tissue imaging and real-time tracking, making it superior to other types of imaging. In addition to its diagnostic power, MRI is being used increasingly as part of clinical procedures. 

But most robotic surgical systems haven’t been compatible with MRI, said Chen, “mainly due to the strong magnetic field generated by the MRI scanner, which precludes the use of ferromagnetic materials.”

To overcome this problem, Chen’s team created a new type of flexible robot made from polymers, including a plastic, 3D-printed transmission mechanism. The motors that give the robot mobility are made of 3D-printed resin and are powered by pressurized air. Since no electricity is used, there is no interference with the MRI’s magnetic fields.

“We’ve also devised a controller that ensures the motors will move accurately and designed them in a way that allows easy customization with just a few key settings,” Chen said.

Controlling the Outcome

A key challenge in RFA is manipulating the catheter in the heart, which is not unlike driving a car through a twisting, unfamiliar road. Chen’s robotic system is basically a smart GPS that ensures the car stays on the right path at the right speed.

“Our system will use MR imaging and catheter tracking to provide real-time feedback to the physician, which will help them guide the catheter more accurately,” Chen said. 

Additionally, the research team has developed sensors that will monitor the contact force between the catheter and the heart tissue — the right amount of pressure is crucial for delivering heat energy, creating effective and continuous lesions, and reducing the chances of AF recurrence.

“The project has multiple phases,” Chen said. “First, we’ll develop the navigation software to merge MR imaging, catheter tracking, and contact force estimation into a single interface. This will provide physicians with comprehensive feedback during the procedure.”

The team will enhance the robotic system to control both the catheter, developing algorithms to ensure precise placement inside the patient. Then they’ll test the system on a heart model in an MRI scanner before testing it on animal models.

This is a multi-institutional effort. In addition to Chen’s students — Yifan Wang, Anthony L. Gunderman, and Milad Azizkhani — his collaborators include Ehud Schmidt and Aravindan Kolandaivelu from Johns Hopkins University, and Junichi Tokuda from Harvard University. 

“We believe this platform will significantly improve the outcomes of AF treatments by providing physicians with better tools to perform precise, effective ablations,” said Chen. “This technology could improve the quality of life for many patients.”