MRI-Based Marker Predicts Arrhythmia Recurrence
Index could be used to identify best candidates for catheter ablation to treat atrial fibrillation.
To treat arrhythmias, doctors often create precise scars on heart tissue using a procedure called catheter ablation. But this procedure doesn't always work. A study published Jan. 12 in JACC Cardiovascular Imaging reveals an MRI-based marker that predicts recurrence of atrial fibrillation -- the most common type of arrhythmia -- after catheter ablation. This marker, called intra-atrial dyssynchrony, could be used to identify patients who are most likely to benefit from catheter ablation, saving less suitable candidates from a potentially futile procedure and complications.
Atrial fibrillation increases the risk of stroke and can also cause heart attack or heart failure. Rapid, disorganized electrical signals cause the heart's two upper chambers -- called the atria -- to contract rapidly and irregularly. Patients who don’t respond to drugs often undergo catheter ablation, which uses energy to make small scars in heart tissue to prevent abnormal electrical signals from moving through the heart.
But the rate of recurrence after the procedure is relatively high, in part due to poor patient selection before the intervention. Although catheter ablation is superior to anti-arrhythmic drugs, recurrence rates can be as high as 40 percent.
“Identifying tools that assist the physician in the selection of adequate candidates is imperative,” said first author Luisa Ciuffo, a postdoctoral fellow at the Johns Hopkins University School of Medicine in Baltimore, Maryland. “The main motivation for this study was to identify a new MRI-based index, which could help the physician in the decision-making process.”
The study participants were 208 patients with a history of atrial fibrillation who were referred for catheter ablation at the Johns Hopkins Hospital. One hundred and one of these patients experienced recurrence of their atrial fibrillation after undergoing ablation.
When the researchers examined MRI images taken before the procedure, they saw that patients with recurrence tended to have greater intra-atrial dyssynchrony -- atrial movements that were more out of sync, with different parts of the atrium relaxing and contracting at different times. The average intra-atrial dyssynchrony was 3.9 percent for patients with recurrence, significantly higher than the 2.2 percent for patients whose atrial fibrillation was successfully treated.
Intra-atrial dyssynchrony has previously been assessed with echocardiography, but the authors point out that this is the first study to demonstrate intra-atrial dyssynchrony using cardiac magnetic resonance.
“In our study, we found that the best indicator of success is how in sync the left atrium chamber of the heart is when it relaxes,” Ciuffo explained. “Diseased, damaged hearts with a lot of scar tissue don’t contract and relax at the same time throughout the atrium because it is more difficult to rhythmically contract the thicker, tougher damaged tissue.”
According to Ciuffo, intra-atrial dyssynchrony is a simple index to quantify. “The average time of measurement was only nine minutes,” she said. “In addition, it is based on MRI, which is routinely required to assess heart anatomy and guide the procedure. Therefore, our index would not increase the expense of catheter ablation because it relies on the MRI that is nowadays the standard of care.”
However, one study limitation was that the analysis was based on a retrospective database of individuals who underwent a catheter ablation. Ciuffo and her colleagues plan to evaluate the validity of the MRI-based index for predicting ablation outcomes in the context of a prospective randomized trial.
If successful, the clinical implications could be significant. “It is imperative to find out who are the patients who will benefit from this therapy to use the right treatment for the right person. This study may provide us better criteria for patient selection,” said Reza Nezafat, an associate professor of medicine at Harvard Medical School in Boston, Massachussetts, who was not involved in the research. But moving forward, it will be important to standardize the measurement and assess its reproducibility and accuracy, he added.