In the March 2 issue of the New England Journal of Medicine, researchers from the University of Michigan Cardiovascular Center and the San Raffaele Hospital in Milan, Italy report the results of a rigorous study of radiofrequency catheter ablation for the chronic form of the most common heart-rhythm disorder: atrial fibrillation.
Although the treatment has shown promise for several years in studies by U-M researchers and others, the new paper gives conclusive evidence of catheter ablation's positive effects on heart rhythm, symptoms, quality of life and heart function -- even in the most difficult-to-treat chronic atrial fibrillation patients.
In all, 74 percent of study participants who had the procedure were free of their irregular heartbeat a year afterward, and did not need rhythm-regulating drugs. They reported a steep drop in the severity of symptoms, and their hearts' left upper chambers returned to normal size. No side effects were reported, though some of the patients needed a second procedure to fully treat their heart rhythm disturbance.
"We have shown objectively, and with rigorous follow-up, that this procedure is a very good option for patients with symptomatic, chronic atrial fibrillation who otherwise may have to live with atrial fibrillation for the rest of their lives," says lead author Hakan Oral, M.D., an associate professor of medicine at the U-M Medical School and member of a U-M Cardiovascular Center team that has treated more than 2,000 atrial fibrillation patients using catheter ablation.
The study was a randomized, controlled trial, and used long-term automatic daily monitoring of heart rhythm, to assess the efficacy of ablation. It involved 146 patients, 77 of whom were randomized to receive a left atrial catheter ablation procedure known as circumferential pulmonary-vein ablation. The remaining 69 patients were randomized to a control group.
The study was supported by U-M's Ellen and Robert Thompson Atrial Fibrillation Research Fund, founded in 2001 by a Detroit philanthropist who has the condition.
More than 2.3 million Americans live with atrial fibrillation, which is caused by electrical "misfires" in the heart muscle that make the upper chambers of the heart quiver and pump erratically. This causes weakness and other debilitating symptoms, and encourages the formation of clots, putting patients at much higher risk of stroke.
Some patients have rhythm problems only occasionally, but most, like those in the study, have them all the time. Usual treatments for atrial fibrillation include electric-shock procedures called transthoracic cardioversions, which requires sedation, and drugs to regulate rhythm and thin the blood, which can cause side effects and often lose effectiveness. Moreover, these measures often are only temporarily effective, and the majority of the patients develop recurrences of atrial fibrillation sooner or later.
Catheter ablation aims to counteract the irregular electrical impulses in the heart muscle by delivering tiny bursts of intense radiofrequency waves to areas of disorganized and rapid electrical activity, thereby short-circuiting the aberrant electrical impulses. The catheters that record electrical signals in the tissue and deliver the radiofrequency energy are inserted through the groin of a sedated patient, and snaked through the major blood vessels into the heart. Then, the catheter head pokes through the septum that divides the heart vertically, and enters the left atrium, where ablation takes place. The radio wave heats the targeted areas of tissue, a process called ablation, but spares nearby tissue.
The new study was the first ever designed specifically to separate the ablation procedure's effects from those of medications and cardioversion, which are often used temporarily after ablation.
All study participants took amiodarone, a rhythm-regulating medicine, for six weeks before and three months after they were randomized to either the ablation group or the control group. Ablation patients were allowed to have a cardioversion during their ablation procedure and as needed in the first three months after the procedure, and they were allowed to take amiodarone for up to three months. Control-group patients had a cardioversion after being randomized, and were allowed to have a second one anytime in the next the three months. During those three months, they took amiodarone daily, then stopped. If their atrial fibrillation came back, control patients were allowed to resume amiodarone or have an ablation procedure. Fifty-three control patients opted for ablation.
For a year, all patients used a portable monitor to record their heart rhythm several times a day and any time their heartbeat became irregular. Those recordings were transmitted by phone to a central location and the rhythm patterns were analyzed by cardiologists who did not know which patients had had ablation. The patients also had several clinic visits, and electrocardiogram and echocardiogram heart tests, during the year, at which they completed questionnaires about the severity of their symptoms.
Although the study was not designed to compare the efficacy of catheter ablation with long-term use of rhythm-regulating medications, only 4 percent of the patients who didn't have the ablation procedure and stopped their medication after three months were still free of their atrial fibrillation after one year.
Senior author Fred Morady, M.D., a professor of cardiovascular medicine who directs the U-M CVC's Clinical Electrophysiology Laboratory, notes that after one year, ablation patients in the study experienced a decrease in the size of their left atrium, which is often enlarged in AF patients, and an improvement in the ejection fraction, or pumping ability, of their left ventricle. The patients who received ablation reported significant reductions in the severity of their symptoms, compared with those who did not receive ablation.
In the ablation group, 20 patients needed one more ablation procedure to address remaining atrial fibrillation, and four had a second ablation after developing a less-serious rapid-heartbeat condition called atrial flutter. There were no complications related to the ablation procedure.
Morady, Oral and their Italian colleagues Carlo Pappone, M.D., and Vincenzo Santinelli, M.D., led the study. U-M co-authors are cardiologists Aman Chugh, M.D., Eric Good, D.O., Frank Bogun, M.D., Frank Pelosi, M.D., Eric Bates, M.D., and Michael Lehmann, M.D. Oral, Morady, and Chugh have consulting agreements or have received grant support from manufacturers of equipment used in ablation, and Oral and Morady have founded a company related to catheter ablation but unrelated to the current study. There was no grant or other support from industry or manufacturers in this study.
Reference: New England Journal of Medicine, Vol 354, No. 9, pp. 36-43.
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