FIRM Ablation Improves Treatment for Atrial Fibrillation
Sanjiv Narayan, MD, PhD, director of the Atrial Fibrillation program at Stanford, developed a new type of targeted ablative therapy that greatly improves treatment results with often less ablation.
February 2015
In the US alone, there are five million people with atrial fibrillation (AF), a number that's expected to double in the next 20 years. When left untreated, this very complex heart rhythm disorder, also known as arrhythmia, can cause heart failure and stroke.
Treatment often starts with lifestyle changes and medication, but many patients can't tolerate the medication or continue to experience breakthrough arrhythmia. For this group, physicians have relied on surgical ablation of the areas in the heart causing the unsteady rhythm. Knowing which areas to ablate, however, hasn't been an exact science.
As a physician and software engineer, Sanjiv Narayan, MD, PhD, professor of cardiovascular medicine and director of the Atrial Fibrillation program at Stanford, was curious about one question — Is atrial fibrillation chaos or a complex, but understandable pattern? Narayan and his team began studying these rhythms and found that by using engineering and software modeling, together with a computational approach, they could map atrial fibrillation. Rather than chaos, they discovered that atrial fibrillation is a complex but deterministic pattern, pinpointed with small, localized areas driving the electrical activity. These areas look like the eye of a storm or a spinning top, says Narayan, sending off disorganized activity like the corona emanating from the sun.
"We developed physiological models and software that allowed us to identify ‘sources' for AF, and then target them for ablation," he adds. "If you eliminate the sources for atrial fibrillation, your patient returns to normal rhythm."
This new form of ablation, called Focal Impulse and Rotor Modulation or FIRM, is based on understanding the rhythm better, says Narayan. "In the CONFIRM trial and multicenter registry studies, we went from about a 50 percent success rate with conventional ablation as shown in recent randomized trials to about an 80 percent success rate by adding FIRM-based ablation," he says. "It's changed the way we think about atrial fibrillation."
In the past, physicians empirically ablated various sections of the heart to hit areas causing the arrhythmia, without actually knowing if they were important to atrial fibrillation in any one individual. But many patients had breakthrough arrhythmia despite the treatment, and would undergo second, third or more ablative treatments. FIRM can lead to significantly improved results, often with less ablation since it is a more targeted approach, says Paul J. Wang, MD, professor of cardiovascular medicine and bioengineering.
"FIRM ablation provides a truly unique method to identifying areas that may be critical to sustaining atrial fibrillation," says Wang. "It has brought us from a purely anatomic ablation strategy to one that can identify target areas in the specific individual."
When testing this new technique on the first patient, Narayan used FIRM ablation on a 47-year-old man who had undergone three previous ablations, but continued to experience severe breakthrough fibrillation. Narayan identified that this patient's arrhythmia was emanating from the right atrium. Standard ablative treatments almost always begin in the left atrium near the pulmonary vein, he says. By starting ablation in the right atrium, Narayan was able to stop the patient's arrhythmia "after just minutes of ablation." A second patient had a similar result. In presenting their findings in 2011, Narayan and his team showed greatly improved success rates in treating atrial fibrillation using FIRM — all while destroying less tissue.
"My goal is to get the best result with the minimum amount of ablation," says Narayan, who joined Stanford last September, bringing ten years of experience developing and using FIRM in patients with atrial fibrillation. "We're also working to improve on it further by engaging the scientists and the bioengineers at Stanford to bring it to the next stage."
The majority of patients treated with FIRM ablation have atrial fibrillation that is symptomatic despite having been on medications, or have failed a previous ablation.