In several presentations at the American Heart Association's Scientific Sessions 2003, and in a new paper in the Nov. 12 issue of the AHA journal Circulation, heart rhythm specialists from the University of Michigan Cardiovascular Center report their dramatic success in treating atrial fibrillation patients using a technique called radiofrequency catheter ablation.
The reports show that more than 85 percent of patients with intermittent AF were cured after a single session of catheter ablation, and no longer required medications to stabilize their heartbeat and cut their risk of clotting and strokes. Complication rates were extremely low.
"In all, we have treated more than 500 patients in the last three years and have achieved very favorable results in these patients," says cardiologist Hakan Oral, M.D., lead author of the Circulation paper and the U-M presentations at AHA. "It's still a technically challenging procedure, but we hope to continue to simplify and improve it, and train others to perform it."
Catheter ablation aims to counteract irregular electrical impulses in heart muscle by delivering tiny bursts of intense radiofrequency waves to the areas of disorganized electrical activity. The radio wave "zap" heats the target areas of tissue, a process called ablation, but spares nearby tissue.
The catheters that record electrical signals in the tissue and deliver the radiofrequency energy are carefully inserted through the groin of a sedated patient, and wind through the major blood vessels and into the heart. Then, the catheter head pokes through the septum that divides the heart vertically, and enters the left atrium.
Depending on which areas will be targeted for ablation, doctors guide the tiny devices into position and deliver the radiofrequency pulses with painstaking precision in patterns that resemble dotted lines and circles. Then, they remove the catheter from the body, and monitor the patient overnight.
Recently, Oral says, the technique has been greatly enhanced by the development of new ablation strategies, and the ability to make three-dimensional digital maps of the heart and its electrical signals.
Of the few centers in the world performing catheter ablation, the U-M may be one of the most experienced and the most successful. But Oral hopes the technique can spread to other centers to help as many patients as possible. Oral will conduct a "how-to" session for other heart rhythm specialists at the AHA meeting, and the U-M team has welcomed many doctors to watch them performing the technique in Michigan.
Oral and Fred Morady, M.D., the U-M cardiologist who is senior author on the paper, hope the new results their team is publishing and presenting will help convince others in their field of the technique's worth in tackling an otherwise difficult-to-treat condition. They especially point to the increased success they've had by ablating areas of the left atrium wall, rather than just the juncture between the pulmonary veins and the left atrium.
More than 2.2 million Americans have AF, and 160,000 more are diagnosed each year. In addition to causing heart palpitations, fatigue and pain that can be debilitating, the condition can quintuple a person's risk of stroke, because of blood clots that form in the irregularly beating chambers of the heart. AF can also cause heart enlargement.
The Circulation paper is a prospective randomized trial involving 80 patients with the paroxysmal, or intermittent, form of AF, all of whom had experienced symptoms for years.
Ever since Michel Hassaguerre, M.D. and his colleagues in Bordeaux, France, first described how AF is initiated by electrical impulses that originate in the pulmonary veins, ablation attempts have primarily focused on electrical disconnection of the pulmonary veins from the left atrium. However, another approach proposed by Carlo Pappone, M.D., in Milan, Italy, suggested that higher efficacy might be possible via ablation within the left atrium, to encircle the pulmonary veins.
It was not clear which approach would be best. So, Oral and his colleagues randomized patients to undergo ablation in one of two ways. Some had it at the junction (ostia) between the pulmonary veins and the left atrium (a procedure called segmental ostial ablation or SOA). Others had a left atrial ablation procedure that was modified by Oral and his colleagues to include lines of ablation in the left atrium in addition to encircling the ostia (a procedure called left atrial catheter ablation or LACA).
Six months after treatment, 67 percent of the SOA patients were symptom-free without medication, compared with 88 percent of the LACA patients. Only one patient had a complication.
The results will help settle the controversy over which form of the technique is more reliable, Oral says, because it's the first time SOA and LACA have been compared directly.
Catheter ablation for AF has been done for several years at a handful of centers. In addition to treating patients with paroxysmal AF, the U-M team treats patients with the much more debilitating and harder-to-treat form of the disorder called persistent AF.
At AHA, the U-M team will report the results of their efforts based on data gathered from more than 100 persistent AF patients. They treated 24 with the SOA technique, and the remaining patients underwent different forms of left atrial ablation. After six months, 25 percent of the SOA group, and more than 75 percent of the left atrial ablation group, were symptom-free without medication.
Also at AHA, the U-M team will report the results of their efforts to determine which patients undergoing catheter ablation for AF are more likely to develop atrial flutter, a related but different arrhythmia. They found that patients who had a history of atrial flutter, or who had inducible atrial flutter during the ablation procedure, were at risk of developing atrial flutter later on. Therefore, the authors suggest that in these patients, ablation with a certain region of the right atrium should be performed at the same time as the AF ablation, to minimize the risk of atrial flutter recurrence.
In all, Oral believes the new paper and presentations will help spread the word about the procedure. "I hope that patients and their treating physicians will become aware of the promise that catheter ablation holds, and that more centers will adopt the techniques," he says. "The more patients we can help, the better."
The U-M team's research is funded by the Ellen and Robert Thompson Atrial Fibrillation Research Fund. Oral and Morady have served as consultants and speakers for Biosense-Webster, the company that makes the catheter that detects the electrical impulses in heart and vein tissue.
The other authors on the Circulation paper and AHA presentations are Christoph Scharf, M.D.; Aman Chugh, M.D., Burr Hall, M.D., Peter Cheung, M.D., Eric Good, D.O., Mehmet Ozaydin, M.D., Srikar Veerareddy, M.D., and Frank Pelosi, Jr., M.D.
References:
"Catheter Ablation for Paroxysmal Atrial Fibrillation: Segmental Pulmonary Vein Ostial Ablation Versus Left Atrial Ablation", Circulation, Vol. 108, Nov. 11, 2003, (published online in October)
Contact:
Kara Gavin
At AHA meeting: cell 734-358-4910, or
Sally Pobojewski, pobo@umich.edu
At U-M: 734-764-2220