MRI may change heart care
U. expert says the tool can be used for rhythm disorder
A heart expert at the University of Utah predicts that a well-known tool commonly used in other areas of medicine magnetic resonance imaging is poised to change how a heart rhythm disorder is treated.
Atrial fibrillation is a common heart malfunction, affecting more than 3.5 million Americans. The unbridled and chaotic contractions of the heart's upper chambers result in more hospitalizations than any other rhythm disorder.
And because blood can pool and create clots, Afib, as it's called, is a leading cause of strokes and heart deterioration. It's most often treated with medications, which may become less effective over time, and/or a process of short-circuiting errant electrical signals around the pulmonary veins, where Afib originates, called radiofrequency (RF) ablation.
Dr. Nassir Marrouche, assistant professor at the U. School of Medicine and director of the U.'s Atrial Fibrillation Program, last week shared with the American College of Cardiology in Chicago the results of studies on MRI's value in locating precisely the tissue where errant signals originate and in assessing how much damage the heart has sustained.
But MRI also has value as a real-time imaging tool during RF ablation, he said. And it's invaluable in tracking the heart's recovery afterwards.
The U. is the first in the country to refine the imaging-based heart ablation procedure to use MRI, he told the Deseret Morning News. And that directly impacts the two historic challenges of ablation: safety and outcome.
Complications of ablation can include narrowing veins, or perforation of the atrial wall and the esophagus, which can be deadly. One approach has been to use lower RF energy to ablate the tissue. But Marrouche said that better imaging is a key to successful treatment.
He came to the U. 17 months ago from the Cleveland Clinic primarily because of the reputation of the Utah Center for Advanced Imaging and the Scientific Computing and Imaging Institute as leaders in use of interventional MRI and advanced imaging.
The technology has opened a whole new world, he said. "For the first time ever, we can see regions in left atrial muscle, which is a tiny chamber that was impossible to see." Before a procedure, MRI can show the details and extent of damage caused by arrhythmia. Through an unknown process, heart tissue subjected to the wild bounce of Afib can become fibrotic and die. Knowing the extent of that not only points out areas for treatment but also indicates whether a patient is a candidate for ablation, since cure rates are low when more than half the tissue is scarred. After the ablation, tissue changes can be tracked.
He's done more than 1,000 ablations and said about 90 percent of his patients are arrhythmia-free and off heart medications within three months. The major complication rate is less than .5 percent. A worldwide survey in 2005 found an ablation success rate that ranged from 14.5 percent to 76.5 percent depending on the center (52 percent average), with another 23.9 percent arrythmia-free when medication was also used. About 6 percent of those ablation patients had a major complication.
But the most exciting thing, he said, is the ability to do an ablation while a patient is actually in the MRI, watching the lesions as the RF burns them. "You can see to stop when the lesion is deep enough," he said of the process, which is still experimental but very promising.
Last Oct. 16, the U. "became the first in the world to be able to ablate using a catheter custom-made to be compatible with MRI. You can burn within the heart without interfering with MRI and watch the extent of lesions," he said.The procedure uses a closed-magnet MRI that Siemens designed for the project, featuring a shorter magnet. And 28 people from various departments of the U. are putting all their effort into redefining ablation and making it more successful, he said.
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