ATRIAL FIBRILLATION FROM A SURGICAL PERSPECTIVE

ATRIAL FIBRILLATION FROM A SURGICAL PERSPECTIVE

Cooper, George N Jr

For over 20 years I have witnessed the ravages of atrial fibrillation (AF) as a frequent, sometimes lethal, postoperative complication. Warfarin is one of the mainstays of AF treatment and reduces the incidence of AF-related strokes.1,2 Until recent, AF has been an irrevocable life sentence.

Major hemorrhages with Warfarin have occurred at an annual rate of 10% in a subgroup over age 75.3 In a large series in Wales,4 patients treated with Warfarin were outside the INR target range 32% to 71% of the time. Time spent outside the target range decreased from 52% initially to 30% after two years. This still leaves many patients at risk for embolism or hemorrhage.

AF is the most common of all sustained cardiac arrhythmias: the prevalence increases with age up to 5% in persons older than 65;and it is a major cause of stroke.5 Other literature shows AF in 8%-17% of the population over age 60.6

AF affects 2.5 million patients in the United States, with 300,000 new cases diagnosed every year. The risk of stroke in patients with AF is estimated at four times greater than in patients without AF. AF is second to heart failure in terms of cardiac-related hospitalizations.

The prevalence of thromboembolism associated with AF is roughly 33% (825,000 United States citizens).7 Approximately 75% of all thromboembolic episodes associated with AF involve the brain (608,000 U.S. citizens). In one series, 60% of cerebroembolic events resulted in death or permanent, severe neurologic deficit (364,950 U.S. citizens).7

In the late 1980s, Dr. James Cox and colleagues in St. Louis identified the electrical characteristics and sites of AF in animals and patients.6 This made possible the development of surgical treatments to prevent the abnormal atrial conduction pathways, which cause this arrhythmia. Dr. Cox developed an operation by which multiple, full thickness incisions were made in both atria to interrupt the abnormal macro-circuits. The left atrial appendage was excised as well, thereby removing the major source of cerebral and peripheral emboli. All of these incisions were then closed by suturing. The result was the Cox “Maze III” operation for AF. If done correctly, the mortality rate was and is low and success in curing AF is still over 93% with no recurrences over 14 years in the original St. Louis series of patients.8 Other series had similar results.9,10

In spite of the success of this concept, the “Maze” was not appealing to heart surgeons because it was a very difficult art form with every suture line a possible bleeding complication. Maze operations needed significant heartlung machine time and had a steep learning curve. Some centers persisted nevertheless and noted a marked reduction in postoperative stroke rate and increased freedom from AF.11,12

Since the late 1990s there has been a resurgence of interest in surgery for AF. Technological advances have made it possible to apply all of the Cox described ablative lesions in a matter of minutes with radiofrequency, cryotherapy or microwave energy with the same effect as the “cut and sew” method, thus avoiding the necessity of multiple atrial incisions and resuturing which commonly took about one to one and a half hours.13

In the recent three to four years, based on laboratory and clinical series,14,15 it has been demonstrated that it is not necessary to perform all of the Cox described atrial ablative lesions to cure atrial fibrillation and that only a basic set of left sided ablations could still accomplish over 90% success and be easily applied even without the help of the heart-lung machine. If necessary, additional right-sided lesions could easily be performed in the electrophysiology laboratory.16,17

Haissaguerre in 1998,1 working in Bordeaux, studied 45 patients, mapping the spontaneous initiation of atrial fibrillation. 69 foci were identified and 65 (94%) were found originating in the pulmonary veins. The pulmonary veins have been targeted, therefore, by electrophysiologists and surgeons working on this problem. Surgeons in many centers, including our own, have been ablating the left atrium adjacent to the entrance of the pulmonary veins and removing the left atrial appendage in each instance. These ablations are usually done with a bipolar radiofrequency device in conjunction with valve or coronary bypass operations. The results are very promising. Over 157 Maze operations have been done in Rhode Island since 2000 by seven heart surgeons. All of these have been carried out in conjunction with operations for other cardiac pathology, including mitral and/or aortic operations, with or without coronary bypass. Initially most of our Maze attempts sought to include all or most of the Cox described ablative lesions on left and right atria. Many times, however, based on various series in the literature,14,15 only left-sided lesions were done, especially if the patient was having an off pump operation; e.g., off pump coronary bypass. There are very few patients in the Rhode Island series who have had Maze procedures who are not free from atrial fibrillation. The exact numbers will be the subject of a follow-up article in this journal.

Recent technological development has included minimally invasive surgical approaches to pulmonary vein-left atrial ablation. These involve bipolar radiofrequency, laser 18 and microwave technologies.19,20 The bipolar radiofrequency device has been easy to use and yields full thickness atrial wall ablation, which completely blocks the pulmonary vein foci from causing AF. Also included in this concept is the denervation, or obliteration, of multiple ganglionic plexi which are numerous and located on and around the pulmonary veins. The importance of this is alluded to by Schuessler, Boineau and Cox who, in 1991,21 discussed atrial fibrillation occurring after bradycardia induced by acetylcholine infusion or vagal stimulation. Also, Coumel22 showed that patients with high vagal tone have spontaneous atrial fibrillation associated with increased vagal activity. Scherlag in Oklahoma 23 reported in 2005 that stimulating the autonomie ganglia at the right superior pulmonary vein in dogs provided a substrate for conversion into atrial fibrillation. Thus, in addition to atrial ablation at the entrance of pulmonary veins, it becomes important to ablate also the ganglionic plexi. This denervation concept is emphasized by Dr. Randall Wolf at the University of Cincinnati. Dr. Wolf’s minimally invasive approach consists of bilateral two and a half inch transverse incisions in the anterior axillary line, entering the chest through the third or fourth intercostal space with no rib spreading, thus no or very little discomfort. A double lumen endotracheal tube is used, allowing selective deflation of the lung on the operative side. First the right side is done, then the patient is turned and positioned with the left side up so that the left sided portion of the procedure can be completed. This concept provides good visualization of pulmonary veins and vena cavae on the right and pulmonary veins and left atrial appendage on the left. Visualization and illumination are aided by a camera port lower down on the chest and one additional port for the radiofrequency device. Most of the work is done through the two and a half inch incisions. After the ablations are completed and the pulmonary veins are electrically isolated, the left atrial appendage is removed or stapled out with the endo-GIA automatic stapling device. Pain has been minimal and hospital stay has been two to three days in Dr. Wolf’s series. Fig 1 shows the extent of the left chest incision after completion of bilateral ablation. In the past 20 months Dr. Wolf has performed the “mini-Maze” in nearly 100 patients.24 All of the patients who presented with paroxysmal atrial fibrillation are in sinus rhythm postoperatively. The patients with permanent atrial fibrillation have taken a bit longer to convert, but they seem to eventually achieve normal rhythm.25 In the beginning of the Cincinnati experience, the intention was to do a mini-Maze only on patients with paroxysmal atrial fibrillation, but patients with permanent atrial fibrillation were referred in significant numbers, so these were added to the mix. In the September, 2005 issue of The Journal of Thoracic and Cardiovascular Surgery,26 Dr. Wolf et al reported on 27 patients (22 male patients) with atrial fibrillation (18 paroxysmal, 4 persistent and 5 permanent; over age 57 years). All underwent the above described bilateral video-assisted thorascopic off-pump epicardial radio frequency pulmonary vein isolation and stapler exclusion of the left atrial appendage. The operation was performed successfully in all patients. There were no conversions to sternotomy or thoracotomy. All patients were extubated in the operating room. The average postoperative followup was 6 months (173.6 days). 23 patients were followed for more than 3 months, and 21 of these were free of atrial fibrillation (91.3%). Magnetic resonance angiography showed no pulmonary vein stenosis in 12 of 12 patients evaluated by this technique 3-6 months postoperatively. The general observation has been that if the left atrium is normal in size or only slightly enlarged, the chances of success with the mini-Maze in permanent atrial fibrillation are good, although it may take three or four months for conversion to sinus rhythm to occur. If the atrium is 6 cm or larger, the patient may be better served with a formal open heart Maze operation with reduction of left atrial size by resecting a strip of left atrial wall in the posterior aspect, which if needed, is very easily accomplished. The long-term results of the miniMaze in permanent atrial fibrillation remain to be delineated, but the initial observations are causing some optimism.

We have begun the minimally invasive AF surgery program at Miriam Hospital. Two patients have successfully completed the operation. One spontaneously converted to sinus rhythm 3 weeks postoperatively and the second is in sinus rhythm after cardioversion 6 weeks post-operatively. Many of the patients will take 4-8 weeks to regain sinus rhythm. Dr. Wolf cautions chat a 3-month wait may be necessary before normal sinus rhythm is achieved. The Wolf mini-Maze concept has significant promise and is associated with a hospital stay of only two to three days as compared to five to seven days with the conventional Maze operation. We are very excited to offer this technology to AF patients in Rhode Island whose lives have been seriously altered by this arrhythmia.

Indeed, as the evolution continues, AF may cease to be a life sentence. The Maze operation and possibly the minimally invasive Maze offer great hope of restoring life without AF or Warfarin, with virtually no surgical mortality and minimal morbidity.

SUMMARY

Before 1985, there was no surgical solution for AF. Any therapy contained uncertainties and Warfarin was still needed in the treatment regimen. The Maze operation as described by Dr. Cox cures AF. Recent modifications in technique and technology have allowed us to apply Dr. Cox’s concepts in ways that are easy to apply surgically with excellent results and virtually no mortality and minimal morbidity. In most cases Warfarin will become unnecessary, the number of strokes will be markedly reduced and normal lifestyle can be restored. The minimally invasive Maze procedure is very appealing. It is an atrial ablation as well as cardiac denervation. It is user-friendly, so far effective and associated with minimal discomfort and short hospitalizadon.

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GEORGE N. COOPER, JR, MD

George N. Cooper, Jr, MD, is Clinical Associate Professor of Surgery, Brown Medical School, and Cardiothoracic Surgeon, Department of Surgery, Rhode Island Hospital.

CORRESPONDENCE:

George N.Cooper, Jr, MD

840 Greenwich Avenue

Warwick, RI 02886

phone: (401)739-0011

e-mail: gncjr@ gncjr.necoxmail.com

Copyright Rhode Island Medical Society Jan 2006

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