J Thorac Cardiovasc Surg 2007;133:395-396
© 2007 The American Association for Thoracic Surgery
Surgery for Acquired Cardiovascular Disease
Clearly, Dr Jim Cox established the gold standard for a procedure to relieve patients of AF, both intermittent and continuous AF. The seminal investigative and clinical work of Dr Cox and Dr Bonieau at Washington University eventuated in the CM III procedure, which was described first in the Journal of Cardiothoracic and Vascular Surgery in 1995, also bears mention. Through detailed intraoperative mapping, he finally settled on an effective right and left atrial incision set that relieved more than 95% of patients from AF. New lesion sets in the CM III procedure at that time improved both right and left atrial transport and decreased the need for pacemakers. Despite these impressive results, the complexity of creating surgical lesions and the morbidity, especially in inexperienced hands, precluded the widespread adoption of the CM III procedure, despite these obvious advantages that Dr Lall has shown us. This is especially true when combined with mitral valve surgery and mitral valve repair.
Dr Damianos work has continued in this illustrious shadow, with attempts to determine an effective operative method that most surgeons can perform in a reasonable time with minimal complications. The procedure described in this presentation used bipolar RF ablation, with most lesions approximating those of the CM III procedure. However, there were differences in the lesion sets.
The authors have compared 154 patients undergoing traditional cut-and-sew operations with 88 patients undergoing the new operation, which has been dubbed here as the CM IV procedure. Because a serial patient series was reviewed retrospectively, the authors used a propensity score analysis to select matched cohorts for comparison. This method yielded 58 patients in the cut-and-sew group and 58 patients in the bipolar RF or CM IV group. Patients had either lone AF, or it was combined with valvular or coronary disease, and therefore they really were not all the same. They determined that more than 90% in both groups were relieved of AF, suggesting that this new method could supersede the traditional operation as a standard. There was no statistical difference between the groups as far as relief from AF. In the CM IV group 12% more patients continue to receive antiarrhythmics, but follow-up was 4 years less than in the CM III group.
A weakness of this study, of course, is the retrospective review, which we are all forced to do, and the small number of patients in each final comparative cohort. However, these seem inescapable considering the evolutionary nature of these methods.
Our results confirm the data presented. In an attempt to render an effective, minimally invasive, small-incision AF operation, we developed an endoscopic method using cryoablative lesions at 150°C. In 161 patients either with lone AF or combined with mitral valve disease, we approximated the lesion set described by Dr Lall. Of the 41 patients with lone AF, either intermittent or continuous, 92% were AF free 3 months without drugs and 2 continued to receive antiarrhythmics, suggesting that a full lesion set, as you suggested, is optimal and that these operations are safe and efficient. We had no mortality in the lone AF group, and 13% required pacemakers, as you have shown here. I have several questions for you.
This commentator applauds you for confirming electrical isolation of pulmonary veins by pacing and mapping for exit block. I think this is important. Would it have been possible to determine isolation of the right side and other parts of the right atrium? Does it matter if we isolate the right atrium? Why do the right side at all if there is no AF?
Would you like me to go ahead and ask all my questions, or let her answer them one at a time?
Dr Mitchell. Lets go one at a time.
Dr Lall. Thank you, Dr Chitwood, for your kind comments and questions. It is an honor to have you discuss our article, and we recognize the many achievements of your group in pioneering minimally invasive AF surgery.
To address your first question on confirmation of conduction block, we can use computerized mapping techniques and multiple electrodes to confirm conduction block, but this is difficult to do in the operative setting; it is very time consuming and not practical. The other way to confirm isolation is with pacing or recording of individual electrocardiograms. This would require a portion of the atrium to be completely electrically isolated from the remainder of the atrium, and in the CM lesion sets, this only occurs around the pulmonary veins.
In terms of the right atrial lesions, we do believe that it is important to perform a biatrial lesion set because mapping studies have shown that between 10% and 30% of patients with AF have a right atrial focus.
Dr Khargi, in the Journal of European Cardiothoracic Surgery in 2005, showed in a univariate analysis that sinus rhythm conversion rates were higher in the biatrial lesion set group, and also Dr Niv Ad has shown this in a meta-analysis. Finally, without any right atrial lesions, there will be an incidence of late atrial flutter of about 10% to 20% in most series.
Dr Chitwood. Therefore you are suggesting we always do the right side.
What is the rationale for isolating the pulmonary veins in 2 islands rather than as 1 continual island?
Dr Lall. The bipolar clamp device that we use makes it impossible to encircle all 4 pulmonary veins at once. Therefore we isolate the right and left pulmonary veins separately, and then a lesion across the inferior posterior left atrium is completed. In patients with an atrium larger than 5 cm, we would place a second lesion that would connect with the superior aspect of the pulmonary vein lesions.
Dr Chitwood. Therefore it is mainly related to the device, is that correct?
Dr Lall. Yes.
Dr Chitwood. And I think I will yield my last 2 questions. My last question will be this: What percentage of your patients required a second electrophysiologic study for flutter? Did you have much flutter develop after these procedures?
Dr Lall. We did not have any reoperations for atrial flutter.
Dr Chitwood. Even in the catheterization laboratory?
Dr Lall. Correct.
Dr Chitwood. I thank the Association for the opportunity to discuss this fine article.
Dr John Stulak (Rochester, Minn). What was your method of rhythm assessment for these patients during their clinical follow-up? Was it telephone interview, electrocardiogram, Holter monitor, etc?
Dr Lall. In the CM III group we did a retrospective follow-up through a mailed questionnaire or telephone interview, as well as having contact with either their cardiologist or primary care physician regarding recurrence of AF. In patients who complained of arrhythmia recurrence, copies of an electrocardiogram and Holter monitoring were obtained. In the CM IV group an electrocardiogram was obtained at scheduled 1-, 3-, 6-, and 12-month follow-up appointments. Our study had 100% follow-up in this group. Patients unable to return to our clinic were contacted by telephone, and electrocardiograms from their referring physicians were obtained. A 24-hour Holter monitor or event recorder was obtained on each patient with any symptoms or palpitations.
Dr Syed Tasnim Raza (Parkersburg, WV). Dr Lall, I wanted to congratulate you on a very fine presentation. When Dr Cox moved from St Louis to Washington, he changed from doing all cut-and-sew maze procedures to cryoablation, using a long cryoablation probe, the procedure he called cryo-maze, and I wanted to ask, how does your CM IV procedure differ from the cryo-maze procedure? My second question is this: you used 2 separate bipolar RF technologies, the Medtronic and the Atricure. Was there any difference between the results in those 2, and have you compared them?
Thank you very much.
Dr Lall. I am unsure of how the cryo-maze procedure compares with our CM IV procedure.
For your second question, the Atricure device was used for 57 of the 58 patients, and the Medtronic device was used for only 2 patient. We did not look for any difference between the 2 devices.
Dr Craig R. Smith (New York, NY). I am curious how much overlap there was during the period of the study between the 2 procedures. You would think that a procedure with such a dramatically reduced crossclamp time would quickly replace its predecessor if it seemed even close to equivalent. If there was little overlap, I would not think you would need to do a propensity analysis.
Dr Lall. We no longer do the CM III procedure at Barnes-Jewish. There was no overlap between the 2 procedures. Thus to compare these 2 nonrandomized groups, a propensity analysis was done.
Dr Smith. I understand. I just could not see as much of a rationale for it if they were really just one procedure following the other. Point made.
J. Thorac. Cardiovasc. Surg. 2007 133: 389-396.
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