Although DE-MRI is an established method for visualising tissue damage in cardiac disease processes, the study assessed its use in a protocol developed to detect fibrosis in atrial fibrillation patients before they underwent radiofrequency ablation. This procedure involves the use of catheters that emit mild, painless radiofrequency energy to destroy carefully selected heart muscle cells to stop them from conducting extra electrical impulses.
In this study, the University of Utah colleagues developed a protocol using DE-CMRI to create 3D images of the left atrium before radiofrequency ablation, which were processed and analysed with custom software tools and computer algorithms to calculate the extent of left atrium wall injury. Patients were then assessed at least six months after the procedure, and the researchers found that only 14% classified as having minimal fibrosis had suffered atrial fibrillation recurrence compared to 75% recurrence for the group that had extensive scar tissue damage.
"Our results indicate that DE-MRI provides a noninvasive means of assessing left atrial myocardial tissue in patients suffering from atrial fibrillation, and that those who do have tissue damage may be at greater risk of suffering AF recurrence after treatment with radiofrequency ablation," said lead author Dr Nassir F Marrouche, University of Utah School of Medicine and director of the 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, three-dimensional 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 in order to visualise the entire volume of left atrium wall injury in 3D.
"Until now, there has not been an accurate, noninvasive way to assess left atrium scar formation, which studies show is linked to AF disease severity," said Marrouche. "If substantiated, our DE-MRI visualisation 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."
Last fall, the University of Utah Atrial Fibrillation program became the first in the world to be able to ablate using a catheter custom-made to be compatible with MRI. Next month, University Health Care will open a new multimillion dollar clinical and research lab, which will be the first in North America to provide real-time DE-MRI for treating patients with AF.