SAN FRANCISCO – Considerable variation by institution suggests that additional training is needed to standardize radiofrequency ablation of persistent atrial fibrillation in patients undergoing concomitant cardiac surgery, according to a prospective, multicenter study.
"As surgeons we need to take the ‘a fib’ part of the procedure more seriously. There can be a high cure rate," Dr. Ralph J. Damiano Jr. said at the annual meeting of the American Association for Thoracic Surgery.
Ralph J. Damiano Jr.
He and his associates studied 150 consecutive patients with persistent or permanent atrial fibrillation (AF) undergoing irrigated unipolar or bipolar radiofrequency treatment at 15 centers between May 2007 and July 2011. The study protocol included use of the Cox Maze IV lesion set.
Freedom from AF at 6-9 months’ follow-up was a primary efficacy end point of the CURE AF (Concomitant Utilization of Radiofrequency Energy for Atrial Fibrillation) trial; this outcome was achieved by 66% of patients. Just more than half of patients, 53%, were not taking antiarrhythmia medications at this follow-up time, another measure of efficacy.
"The Cox Maze IV procedure performed with irrigated radiofrequency ablation in patients with persistent atrial fibrillation restored the majority of patients to sinus rhythm with a low complication rate," Dr. Damiano said.
There was no statistical difference in efficacy outcomes by AF type. Most of the participants, 75%, had long-standing persistent atrial fibrillation, 22% had persistent AF, and 3% had paroxysmal AF.
The mean patient age was 71 years, 56% were men, and the majority had New York Heart Association (NYHA) class II or III heart failure. The mean duration of AF was 64 months.
The primary safety measure in the study was the major cardiac composite adverse event rate within 30 days. A total 6.6% of participants experienced such an event, although none were device related, Dr. Damiano said. There were no cases of pulmonary vein stenosis, he added. Operative mortality was 4%.
Significant predictors of success, defined as freedom from AF, included shorter duration of the persistent or permanent atrial fibrillation, smaller left atrial diameter, and fewer concomitant cardiac procedures, said Dr. Damiano, a cardiothoracic surgeon at Barnes Jewish Hospital in St. Louis.
As an example, the success rate was 50% when total radiofrequency ablation time was less than 6 minutes. By comparison, success grew to 80% with ablation times of 12 minutes or longer.
Left atrial diameter was the only significant predictor of success that remained on a multivariate analysis. Dr. Damiano and his colleagues found that 69% of patients with a left atrial diameter of 3.0-4.5 cm were free from AF, compared with 36% who had a diameter larger than 6 cm. The overall mean left atrial diameter was 5.2 cm.
There were significant differences in achievement of success among different study centers, including a 33% success rate at one site versus 100% at three other sites, Dr. Damiano said.
"The variability between centers is probably one of the most important findings in this study," study discussant Dr. Niv Add said. He asked: "How would you see moving forward with training and credentialing of surgeons?" Dr. Add is chief of cardiac surgery at Inova Fairfax Hospital, Falls Church, Va.
"We were supposed to perform the exact same procedure in the same way," Dr. Damiano replied. "The surgeons all agreed on the lesion set [but] it’s hard to quantify experience. You can see a huge variation in ablation time, so clearly we were not all performing the same procedure. This variability suggests a need for more effective procedural and device training."
A total 80% of patients had concomitant mitral disease; 58% had heart failure; and 52% had tricuspid disease.
The most common surgical procedure was single valve with or without coronary artery bypass grafting (CABG) in 53%. Double-valve surgery with or without CABG was performed in 30% of patients; CABG in 15%; triple-valve with or without CABG in 1%; and other surgery in 1%.
Intraoperative pulmonary vein isolation was measured using exit block and was achieved for 81% of patients. Radiofrequency ablation was performed using Medtronic’s Cardioblate unipolar or bipolar device. As the device is not yet cleared by the Food and Drug Administration for this indication, such use is considered off label.
Dr. Damiano is a consultant for Medtronic. Medtronic sponsored the trial.