Circulation: MRI method could predict outcomes in a-fib patients
Researchers have found that advanced visualization with delayed-enhancement MRI (DE-MRI) holds promise for predicting treatment outcomes and measuring disease progression for patients with atrial fibrillation (AF), according to study appearing in the April 7 issue of Circulation. For this study, the University of Utah colleagues developed a protocol using DE-CMRI to create 3D images of the left atrium before RF ablation, which were processed and analyzed with custom software tools and computer algorithms to calculate the extent of left atrium wall injury.

According to the researchers, 81 patients presenting for pulmonary vein antrum isolation for treatment of AF underwent 3D DE-MRI of the left atrium before the ablation; and six healthy volunteers also were scanned.

Investigators assessed the patients at least six months after the procedure, and the found that only 14 percent classified as having minimal fibrosis had suffered AF recurrence compared to 75 percent recurrence for the group that had extensive scar tissue damage.

The authors wrote that on the basis of the extent of preablation enhancement, 43 patients were classified as having minimal enhancement, 30 as having moderate enhancement and eight as having extensive enhancement.

"Our results indicate that DE-MRI provides a noninvasive means of assessing left atrial myocardial tissue in patients suffering from AF, and that those who do have tissue damage may be at greater risk of suffering AF recurrence after treatment with RF ablation," said lead author Nassir F. Marrouche, MD, assistant professor of internal medicine in the University of Utah School of Medicine in Salt Lake City, and director of its atrial fibrillation program. "Our findings also present a disease progression model that supports the importance of early intervention."

In addition to its noninvasive nature, DE-MRI offers other advantages over commonly used invasive electroanatomic mapping studies to assess tissue health. For example, while other such diagnostic mapping studies have been associated with a high degree of spatial error, 3D DE-MRI provides information on both the anatomy and the location of pathology without spatial distortion. Marrouche and his colleagues also have developed methods of processing the MRI images to visualize the entire volume of left atrium wall injury in 3D.

"Until now, there has not been an accurate, non-invasive way to assess left atrium scar formation, which studies show is linked to AF disease severity," said Marrouche. "If substantiated, our DE-MRI visualization technique and analysis would provide guidance in determining appropriate candidates for AF catheter ablation as well as in identifying the heart muscle cells that need to be destroyed."

Atrial fibrillation affects more than 3.5 million Americans and causes more than 66,000 deaths a year.