Isolating the posterior left atrium by creating a box lesion in a 20-second procedure showed a significantly lower incidence of early atrial tachyarrhythmias and higher freedom from atrial fibrillation (AF) recurrence at one and three months, according to a study published in April issue of the Journal of Thoracic and Cardiovascular Surgery.
The importance of each ablation line in the Cox maze procedure for treatment of AF remains poorly defined, according to the researchers.
Rochus K. Voeller, MD, from the division of cardiothoracic surgery at the Barnes-Jewish Hospital in Saint Louis, and colleagues evaluated differences in surgical outcomes of the procedure performed either with a single connecting lesion between the right and left pulmonary vein isolations versus two connecting lesions (the box lesion), which isolated the entire posterior left atrium.
The researchers collected data prospectively on 137 patients, who underwent the Cox maze procedure from April 2002 through September 2006. Before May 2004, the pulmonary veins were connected with a single bipolar radiofrequency ablation lesion in 56 patients, whereas after that time, a box lesion was routinely performed in 81 patients, the investigators reported. The mean follow-up was 11.8 months.
Voeller and colleagues found that incidence of early atrial tachyarrhythmia was significantly higher in the single connecting lesion group compared with that in the box lesion group (71 vs. 37 percent). The overall freedom from AF recurrence was significantly higher in the box lesion group at one month (87 vs. 69 percent) and three months (96 vs. 85 percent), the authors wrote.
The researchers also found the use of antiarrhythmic drugs was significantly lower in the box lesion group at three months (35 vs. 58 percent) and six months (15 vs. 44 percent).
The findings also showed a lower use of antiarrhythmic drugs at three and six months, according to researchers.
"The box lesion surrounds and electrically isolates the pulmonary veins and the posterior left atrial wall from the rest of the left atrium. Our study shows excellent success when using the box lesion, and we recommend it for any patient with long-standing atrial fibrillation,” said co-author Ralph J. Damiano, Jr., MD, from the Washington University School of Medicine in St. Louis, reported the Washington Post.
Voeller and colleagues concluded that complete box lesion should be included in all patients undergoing the Cox maze procedure.