By Mitchel L. Zoler, Internal Medicine News, June 15, 2006
PHILADELPHIA -- A modified version of the Cox maze procedure has simplified and shortened the surgical treatment of atrial fibrillation.
This new version of the Cox maze treatment substitutes bipolar, radiofrequency ablation for most of the atrial lesions that were previously placed with a cut-and sew technique.
"In our experience, use of radiofrequency-ablation technology significantly simplifies the surgical treatment of atrial fibrillation and broadens the application of this curative procedure," Dr. Shelly C.Lall said at the annual meeting of the American Association for Thoracic Surgery.
She and her associates at Barnes-Jewish Hospital in St. Louis named this modified procedure the "Cox maze IV." Since its introduction about 5 years ago, they have used the new procedure on 88 patients, and now use it exclusively when patients undergo surgical treatment foratrial fibrillation. Until this change, the previous procedure--known as the Cox maze III--was their standard technique for surgically treating atrial fibrillation, said Dr. Lall, a cardiac surgeon at Barnes-Jewish Hospital and at Washington University, St. Louis.
The results "suggest that the new method could supersede the traditional operation as the standard," commented discussant Dr. W. Randolph Chitwood Jr., chairman of the department of surgery at East Carolina University, Greenville, N.C.
The Cox maze IV procedure was developed by a group headed by Dr. Ralph J. Damiano Jr., chief of cardiac surgery at Barnes-Jewish Hospital and the John M. Shoenberg Professor of Surgery at Washington University.
The lesion set used in the Cox maze IV procedure includes all of the lesions of Cox maze III. The only difference is that most--but notall--of the surgical incisions of the Cox maze III procedure are replaced by lesions produced using bipolar, radiofrequency ablation. (See diagram.) The Barnes-Jewish Hospital group has used two different radiofrequency-ablation devices when performing Cox maze IV procedures. Some patients were treated with a device made by AtriCure Inc., and the rest were treated with a device made by Medtronic Inc. Dr. Damiano is a consultant to both companies.
To assess the effect of the Cox maze IV procedure on atrial fibrillation management, Dr. Lall and her associates compared the outcomes of patients who were treated with Cox maze IV with those treated withCox maze III. Since April 1992, 154 patients were treated at Barnes-Jewish Hospital with the Cox maze III procedure.
The researchers used a propensity analysis to identify matched patients from the two treatment series. The analysis identified 58 patients who were treated with Cox maze III and 58 very similar patients who were treated with Cox maze IV. Although seven clinical and demographic variables were used in the matching process, the most important variables for matching were age and New York Heart Association Classification for heart failure before surgery. Late follow-up data were available for 112 of these 116 patients, with an average follow-up of 4.3 years in the Cox maze III group and an average of 1.2 years in the Cox maze IV group.
The two techniques were equally effective. At 1 year following surgery, 96% of patients treated with Cox maze III were free of atrial fibrillation, compared with 93% of patients treated with Cox maze IV, a difference that was not statistically significant.
The Cox maze IV procedure had the advantage of speed, requiring anaverage cross clamp time of 76 minutes, compared with an average cross clamp time of 121 minutes among the patients treated with Cox mazeIII, a statistically significant difference. All other measured aspects of the patients'' surgery and outcome were similar in the two groups, Dr. Lall said. These included ICU and hospital stay, 30-day mortality, permanent pacemaker placement, and early atrial tachyarrhythmias.