Radiologists, cardiologists pair up to treat atrial fibrillation

April 20, 2009

Radiologists and cardiologists may find themselves collaborating more than ever in treating atrial fibrillation. A new study showing the utility of delayed-enhancement MRI may help bridge the gap between the two specialties.

Radiologists and cardiologists may find themselves collaborating more than ever before to treat atrial fibrillation; a new study shows the value of delayed-enhanced MRI to determine whether therapy can be successful, bridging the gap between the two specialties.

Delayed-enhanced MRI (DE-MRI) noninvasively shows damage to left atrial myocardial tissue and also predicts how well patients will respond to radiofrequency ablation, according to a study (Circulation 2009;119:1758-1767).

Atrial fibrillation, which affects approximately 3.5 million people in the United States, is a heart rhythm disorder that scars the left atrium and can lead to stroke. Delayed enhancement on MR can detect areas of no- or low-voltage caused by the scarring, and whether therapy can be successful. Minimal areas of enhancement suggest a good prognosis, but at higher levels the outcomes get progressively worse, the study found.

Dr. Nassir Marrouche, director of cardiac electrophysiology laboratories as well as director of the atrial fibrillation program at the University of Utah Health Sciences Center in Salt Lake City, and colleagues, studied 81 patients with atrial fibrillation. The patients underwent 3D DE-MRI of the left atrium before ablation. As a control, six healthy volunteers were also scanned.

Common practice is to put atrial fibrillation patients on antiarrhythmic drugs if they had atrial fibrillation for a long period of time, or sent home and told to take aspirin if they had symptoms for a few days or less. This paper changes all that.

"We're saying if you have atrial fibrillation get an MRI scan because we show in this paper there is no correlation between the duration and how much structural damage has been caused by this disease," he said.

The researchers assessed patients for atrial fibrillation recurrence at least six months after pulmonary vein antrum isolation with RF ablation. Before the therapy, 43 patients had minimal left atrium wall enhancement, 30 had moderate enhancement and eight had extensive enhancement.

After treatment, 56 remained free of atrial fibrillation recurrence while off antiarrhythmic drugs. Only six patients with minimal enhancement suffered atrial fibrillation recurrence, whereas 13 of the moderate and six of the extensive group suffered recurrence. Thus, the research indicates the higher the area of left atrium enhancement, the higher the atrial fibrillation recurrence after RF ablation.

This paper essentially defines the point of no-return, according to Marrouche.

If a patient has less than 35% scarring they are encouraged to undergo ablation. Anymore than that and it's not worth the trouble, he said.

The implications of this paper are radiologists and cardiologists must start working together more, according to Marrouche.

"If someone sees our collaboration at the University of Utah they say, ‘You are betraying the world of radiology,' and it is the same with cardiologists," he said. Ideally, there should be an atrial fibrillation section.

"You need radiologists to have a successful endeavor like this one. This is only the start. I foresee in the future there will be an MRI machine in every cardiology practice, which is supported by radiology. There's no way around it, especially with the papers coming out showing the usefulness of this," he said.

For more information from the Diagnostic Imaging archives:

DE-MRI predicts postablation scarDelayed-enhanced coronary artery imaging tracks vascular inflammation changesMRI demonstrates heart morphology and function