A heart procedure may be an effective alternative for treating the leading cause of strokes in the U.S., an abnormal heart rhythm called atrial fibrillation, suggests a large new study.
In a group of nearly 38,000 people, researchers compared individuals with similar stroke risk profiles to one another, and found that those with atrial fibrillation who underwent the catheter ablation procedure fared better than those on medications alone over three years.
During that time, ablation patients had about as many strokes as the general population without atrial fibrillation, while people on just medication had about twice as many.
“The risk going in doesn’t seem to matter on the outcome,” said Dr. Douglas Packer at the Mayo Clinic in Rochester, Minnesota. “Those at the highest risk (of stroke) still appear to have received substantial benefit from the ablation.”
The study is “a very important piece of work and has all kinds of implications for patients with (atrial fibrillation),” said Packer, who studies the causes of atrial fibrillation but was not involved in the new research.
According to American Heart Association figures, as many as five million Americans experience the chaotic heart-muscle contractions of atrial fibrillation, a condition that becomes more common with age, and also with other diseases, including diabetes and high blood pressure.
The disordered beating can cause blood clots to form inside the heart chambers, and those clots may escape and travel to the brain. Atrial fibrillation is thought to cause about 15 percent of all strokes in the U.S., according to the National Stroke Association.
Drugs to restore normal heart rhythms work poorly and come with unpleasant side effects, so blood-thinning medications to reduce stroke risk are the mainstay of treatment for atrial fibrillation, though they do not treat the fibrillation itself.
Catheter ablation involves threading a thin tool through blood vessels to the interior of the heart, where it applies electrical current to burn tissue that generates the abnormal rhythms.
To see how well ablation reduces stroke risk in atrial fibrillation patients and how it compares to standard care, Dr. Thomas Bunch, a heart rhythm specialist at Intermountain Medical Center in Murray, Utah, and his colleagues looked at data on 37,908 participants in a large healthcare network. They ranged in age from 60 through the late 80s.
The group included 4,200 people with atrial fibrillation who underwent ablation, 17,000 with atrial fibrillation who did not have the procedure and another 17,000 people matched with the first two groups for age and gender who did not have atrial fibrillation or ablation.
The researchers also matched people in the three groups based on their risk profiles for stroke because of previous strokes, high blood pressure, diabetes and congestive heart failure.
After one year, about 900 people had strokes. Among those with atrial fibrillation who did not have ablation, 3.5 percent had a stroke while 1.4 percent of those who did have ablation had strokes. The stroke rate in the comparison group without atrial fibrillation was also 1.4 percent.
After three years, the results were similar and held across all risk-profile categories, Bunch and his colleagues report in the journal Heart Rhythm.
The study cannot prove that the ablation procedure reduced stroke risk. It remains unclear, for instance, whether ablation patients had more follow-up care that could also have helped reduce their stroke risk, notes Dr. Yasuo Okumura at the Nihon University School of Medicine in Tokyo, Japan, in an accompanying editorial.
The researchers also did not have information on what drug treatments atrial fibrillation patients were taking, so they could not compare the procedure to specific medications or ablation with or without additional medication.
But as the largest study to date of stroke risk following ablation for atrial fibrillation, Bunch considers the results encouraging.
“It was really gratifying when we saw a reduction in stroke risks that were across the (risk) profiles,” said Bunch. “This means we have the opportunity to improve the long-term quality of life in many or our patients, despite the presence or absence of other diseases they may have in addition to atrial fibrillation.”
The procedure isn’t a new treatment, he said, but it is usually considered secondary to medication and is not offered at all hospitals.
“Atrial fibrillation ablation is typically offered in facilities that have a high level of expertise in caring for many cardiac conditions,” Bunch said. “Since not all facilities offer (the procedure), there is an access issue… when you consider the extent of the disease in our communities.”
The procedure can cost upwards of $80,000, but in Bunch’s study, patients were covered either privately or by Medicare insurance.
A clinical trial underway will include 22,000 patients worldwide and follow them for five years from their first atrial fibrillation diagnosis. Known as the Catheter Ablation versus Antiarrhythmic Drug Therapy for Atrial Fibrillation Trial (CABANA), it will also examine the costs and benefits of ablation versus drug therapy.
Previous research by Bunch that found lower death rates among atrial fibrillation patients who underwent ablation was an impetus for the CABANA trial, according to Packer, who is leading the international study.
“He provided rationale for our hypothesis, which is that ablation will be better than drug therapy, and you need to do the CABANA trial to confirm this study,” Packer said.
With population aging and increases in related diseases like diabetes, the Centers for Disease Control and Prevention predicts that as many as 12 million Americans will have atrial fibrillation by the year 2050.
“This is a condition that is increasing rapidly by reasons beyond old age,” Bunch said. “One in eight of us will develop AF, if we live long enough.”
Current guidelines place atrial fibrillation patients on anti-arrhythmic medications or blood thinners first to reduce the risk of stroke. But Bunch said that his results suggest patients might benefit from ablation if their medications are not effective.
SOURCE: Heart Rhythm, online July 22, 2013.