Researchers in the University of Utah College of Engineering are working with cardiologists and radiologists to transform the treatment of heart rhythm disorders, which abnormally affect the electrical activity of muscles in the heart.

The most common arrhythmia is atrial fibrillation, which affects at least 2.5 million Americans and leads to more than 66,000 deaths a year in the U.S. By 2050, the incidence of atrial fibrillation is expected to double to 5 million Americans. 

In atrial fibrillation, the right and left atria of the heart lose their synchronization and beat erratically and inefficiently. While usually not life-threatening in its initial stages, the condition reduces the pumping capacity of the heart and elevates heart rate. Over time the condition can lead to a stroke—15 percent of all strokes are caused by atrial fibrillation.

Although there are medications to treat atrial fibrillation, over time these drugs often become less effective at controlling stray electrical impulses and are also poorly tolerated by many patients. One intervention that can permanently suppress atrial fibrillation without the use of supplemental drugs is a procedure called radiofrequency catheter ablation—where a catheter with an energy-emitting probe is inserted into a vein and threaded into the heart to direct radiofrequency energy directly to trouble spots. The heat from the probe creates scar tissue in the heart, which eliminates erratic electrical signals.

However, the treatment is not always successful. Pre-existing fibrosis in the left atrium can hinder the ability to effectively burn away electrically defective tissue. In addition, doctors historically have had no way to tell the severity of the disease or pinpoint the exact locations of the troubled tissue, making it challenging to determine whether all of the problem spots have been treated.

Using MRI for Atrial Ablation

University of Utah researchers are seeking to improve the success and safety of atrial ablation through advances in medical imaging, specifically through the use of magnetic resonance imaging (MRI). Imaging specialists at the U have developed new ways of using MRI to visualize the walls of the atria, a task previously considered almost impossible in a beating heart.

“MRI has the potential to reveal important data about the condition of heart tissue before and after an ablation,” says Rob MacLeod, associate professor of bioengineering and a faculty member of the Scientific Computing and Imaging Institute (SCI) and the Cardiovascular Research and Training Institute (CVRTI). MacLeod is on the image analysis and processing team at SCI developing the software technology that allows doctors to get the most accurate information from MRIs. 

“The U is at the forefront of developing better imaging techniques and analysis in conjunction with MRI,” he says. “This can show the physicians whether a patient has too much atrial fibrosis to be a good candidate for ablation. MRI also helps after an ablation to show where scar tissue is forming. This information is critical for properly planning and guiding ablation therapy.”

The U’s research team was formed after cardiologist Nassir Marrouche came to the University of Utah and learned of the advancements SCI and the Utah Center for Advanced Imaging Research (UCAIR) were making in computing, imaging and visualization. Recognizing the possibilities MRI could offer for ablation therapy, Marrouche founded the U’s Comprehensive Arrhythmia Research & Management Center (CARMA) in 2009, leading a team of researchers who are conducting the world’s most innovative research on the use of MRI to treat atrial fibrillation.

The executive committee leadership of CARMA includes Marrouche, MacLeod, radiologist Dennis Parker (director of UCAIR), cardiologist Chris McGann, and hospital administrator Jeremy Fotheringham. Other members of the interdisciplinary research team include bioengineer Edward Hsu and radiology researchers Dennis Parker, Edward DiBella, Eugene Kholmovski and Rock Hadley. Ross Whitaker, another member of SCI and professor in the School of Computing, helped develop the image processing software that is essential for the project. 

Personalizing Treatment for Each Patient

Marrouche performs pre-ablation MRIs in his patients to obtain 3-D images of the heart that help him map the location and extent of diseased tissue. The cardiology team quickly recognized that atrial walls in one patient look different from another. Software developed by MacLeod, Whitaker and their group at SCI allowed the team to visualize and quantify these differences—including atrial wall thickness, structure, shape and composition—in each individual patient.

“The results were striking and allowed us to create a method to identify and measure regions of the heart most altered by atrial fibrillation,” says MacLeod. “The notion of personalized medicine is very important because there is no ‘one size fits all’ when it comes to treatment.”

The software created by MacLeod and his group allowed doctors to design a classification system to help guide personalized treatment for each patient. Patients with high scores in the “Utah Classification Scheme” make poor candidates for ablation since their disease has progressed too far for current ablation techniques. The focus then turns to managing the disease with medication. Patients with low Utah scores have a higher likelihood of success and are treated more aggressively with ablation. 

“When we first started this project, it would take 10 hours to image, map and analyze a patient’s heart,” says MacLeod. “Today, it can be done in 20 minutes. That’s the difference computing and software can make.”

Once an ablation is performed, the patient is immediately taken back into the MRI scanner to see whether all of the problem spots were treated. The success rate is currently in the range of only 60 to 80 percent. “We can take an MRI of a patient after an ablation and can be fairly confident we got it all,” he says. “Ablation causes the tissue to blister, so it is difficult to see exactly what’s happened until the heart heals. We have to wait for about three months and another MRI to see whether any spots were missed.”

To solve this problem, the CARMA team is conducting pioneering research into the integration of real-time MRI with ablation therapy. Last year, the research team opened the first integrated electrophysiology MRI laboratory in North America with a high-tech scanner from Siemens that provides high-resolution images of the heart. The lab also includes fluoroscopy, computed tomography and intracardiac echo. Patients move along a track in the floor between fluoroscopy and MRI areas (the two technologies cannot yet exist in the same scanner), and images from both systems will be immediately fused and updated in real-time as the patient undergoes ablation.

As part of his research into the electrophysiology of the heart, MacLeod and his group are seeking to develop quantification software that shows whether the research can be applied universally. “We are working nationally with 12 centers that send us their images so we can see whether our algorithms work on a broad variety of images, not just our patients,” MacLeod says. 

CARMA is also developing software that will link patient records with images, so that patients have access to their images in the doctor’s office. Further, CARMA researchers are working with Chuck Grissom in the chemistry department at the U to develop better biomarkers for atrial fibrillation. 

MacLeod also points out his role as an educator. “Being part of a research university, we have a great opportunity to impact educational experiences for students,” he says. “Students get to be involved in cutting-edge research, where they learn how to do image analysis or they get involved in the patient care. It’s a great thing to offer those who are interested in engineering and medicine.”