Catheter ablation, a common cardiovascular procedure, appears no more effective than drug therapies in preventing strokes, deaths, and other complications in patients with atrial fibrillation. However, patients who get the procedure experience much greater symptom relief and long-term improvements in the quality of life, including fewer recurrences of the condition and fewer hospitalizations, than those who get only drugs. The findings are from two new studies published in the issue of the Journal of the American Medical Association.
The papers report the outcomes of the Catheter Ablation versus Antiarrhythmic Drug Therapy for Atrial Fibrillation (CABANA) trial, funded in part by the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health. It was a randomized trial that compared state-of-the-art drug therapies for atrial fibrillation — an irregular heartbeat — to ablation, a procedure in which a doctor inserts a catheter through a patient’s blood vessels to scar or destroy heart tissue causing the irregularities.
“Since current drug therapies often have limited effectiveness in controlling atrial fibrillation, it is very important to understand whether ablation, an invasive procedure, yields better outcomes,” said David Goff, M.D., Ph.D., director of the Division of Cardiovascular Sciences at NHLBI. “As these two papers show, CABANA provided a wealth of information that doctors can use to manage patients better and improve their quality of life.”
Atrial fibrillation, the most common cardiac arrhythmia, affects at least 2.7 million Americans, and is a major contributor to stroke, congestive heart failure, and even late cognitive impairment. Symptoms include rapid palpitations, in which the heart flip-flops or skips; fatigue; shortness of breath; and difficulty with physical exertion. While some patients have no symptoms, others suffer a severely-diminished quality of life. Some become extremely distressed and even disabled by both the actual symptoms and the unpredictability of them.
Researchers with the CABANA trial wanted to know what course of action—ablation or drug therapy—would be better at reducing these patients’ rates of death, disabling strokes, serious bleeding or cardiac arrest.
From November 2009 when it was launched to April 2016, CABANA enrolled more than 2,200 patients at 126 sites in the United States, Canada, Europe, and Asia.
About half the patients were randomly assigned to the ablation procedure. The other half was assigned to drug therapy; but they could choose to undergo ablation if their symptoms could not be controlled. Approximately 27 percent of patients in the drug therapy arm ended up also receiving ablation. The median follow-up period for the trial was 48.5 months.
“While data from the trial did not show that ablation was superior to drug therapy in reducing rates of deaths and strokes, it showed reduced recurrence of atrial fibrillation, as well as reductions in hospitalizations,” said Yves Rosenberg, M.D., the program officer for the study, and chief of the NHLBI’s Atherothrombosis and Coronary Artery Disease Branch.
The overall rate of deaths and strokes was lower than expected; and about 9 percent of those assigned to ablation were not able to undergo the procedure. This could have affected the study’s results, according to Douglas L. Packer, M.D., a cardiologist and professor of medicine at Mayo Clinic, in Rochester, Minn. and the study’s principal investigator.
“Most commonly, we look at clinical trial data by comparing the results according to which group a patient is randomly assigned, but patients and physicians do not always follow the assigned treatment. When we examined the data according to the treatment actually received, the ablation group had significantly lower rates of death as well as the combination of death, disabling stroke, serious bleeding, or cardiac arrest compared with patients who only received drug therapy,” said Packer.
The data also showed a significant long-term improvement in quality of life, as well as a reduction of the symptoms of atrial fibrillation, among the patients in the catheter ablation treatment group. This was a key secondary objective of the CABANA research program. Ablation for atrial fibrillation had previously been shown to improve quality of life over drug therapy, but those early studies had limited sample sizes and short follow-ups of one year or less.
“CABANA, because of its size and duration, provides extraordinary new data regarding the patient’s perspective,” said Rosenberg.
Just 12 months after the start of treatment, the quality of life of patients in both groups improved substantially. However, those treated with ablation saw greater decrease in symptoms of atrial fibrillation, such as fatigue and shortness of breath, and these quality of life improvements were sustained over the five-years of follow-up.
At baseline, 86 percent of patients in the ablation group and 84 percent on drug therapy reported atrial fibrillation symptoms during the previous month. By the end of the study, however, there had been a significant decrease in symptoms – with only 25 percent of patients in the ablation arm reporting symptoms compared to 35 percent in patients treated with drug therapy alone.
The researchers also noted that patients with the most severe quality of life impairments at the time of enrollment in the study showed significantly greater improvement after catheter ablation than patients with initially mild symptoms.