Atrial fibrillation (AF) is an abnormal heart rhythm. One effective method of treating AF is radiofrequency (RF) ablation. In RF ablation, mild, painless radiofrequency energy is used to destroy carefully selected heart muscle cells to stop them from conducting extra electrical impulses. Previous research suggested scar formation within the left atrium (LA) after RF ablation helps to predict the success of the procedure in preventing the recurrence of atrial fibrillation.
“Until now, there has not been an accurate, non-invasive way to assess LA scar formation,” said lead author Nassir F. Marrouche. “We have developed a novel MRI-based method to detect and measure the extent of LA wall scarring and, potentially, predict the success of RF ablation.”
The scientists developed a technique for using a non-invasive method called delayed-enhancement cardiovascular MRI (DE-CMRI) to create 3-D images of the left atrium both before and after RF ablation in patients with atrial fibrillation. They processed and analysed these images using custom software tools and then used computer algorithms to calculate the extent of LA wall injury.
The team found that all patients who underwent RF ablation showed evidence of left atrium wall injury on MRI three months after the procedure. The pattern of tissue injury correlated with the areas where the radiofrequency energy was applied during RF ablation, and thus, was presumed to reflect tissue scarring. The scientists also found patients with a higher percentage of LA wall injury were more likely to be free of arrhythmia than patients with lower percentages, suggesting the degree of scarring is linked to the likelihood of success in the RF ablation procedure.
The novel visualisation technique and analysis potentially could help doctors improve planning for RF ablation procedures by making it easier to identify the heart muscle cells that need to be destroyed. Improved localisation and isolation of these heart muscle cells would likely lead to a reduction in the recurrence rate of AF.
“The benefit of 3-D MRI is that it visualises the entire LA wall,” said Marrouche. “And, it is safe and non-invasive, so it can be repeated without significant risk to the patient.”