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Ann Thorac Surg 2005;80:210-216
© 2005 The Society of Thoracic Surgeons
Joseph B. Whitehead Department of Surgery, Division of Cardiothoracic Surgery, Emory University and Emory Crawford Long Hospitals and the Emory Clinic, Emory University School of Medicine, Atlanta, Georgia
Accepted for publication January 17, 2005.
* Address reprint requests to Dr Craver, The Emory Clinic, Division of Cardiothoracic Surgery, 1365 Clifton Rd, Atlanta, GA30322 (Email: joseph_craver{at}emoryhealthcare.org).
Presented at the Fifty-first Annual Meeting of the Southern Thoracic Surgical Association, Cancun, Mexico, Nov 2–4, 2004.
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Abstract |
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METHODS: A retrospective review was performed on 54 patients undergoing radiofrequency ablation with concomitant cardiac operations from March 2002 through July 2003. Forty-two patients (77.8%) received left atrial ablation, and 12 (22.2%) received biatrial ablation.
RESULTS: Mean duration of preoperative AF was 46.3 ± 44 months; 23 (42.6%) had AF 5 years or more, 32 (59.3%) had continuous AF, and 12 (22.6%) had a preoperative left atrial diameter of 6.0 cm or greater. At discharge, 33 patients (70.2%) were free from AF, 30 (62.5%) were in normal sinus rhythm, and 6 (12.7%) required a new pacemaker. Mid-term follow-up was available in 44 (93.6%) patients, with a median follow-up of 8.7 months (range, 3 to 22 months). At follow-up, 34 (77.3%) patients were free from AF. There were no significant differences in freedom from AF in patients with continuous versus intermittent AF or duration of 5 or greater years versus less than 5 years. In patients with isolated mitral valve surgery and radiofrequency ablation, 22 (88.0%) were free from AF compared with 12 (63.2%) with other operations (p = 0.074). In patients with left atrial diameter less than 6.0 cm, 30 (88.2%) were free from AF compared with 4 (40%) with left atrial diameter of 6.0 cm or greater (p = 0.006).
CONCLUSIONS: Radiofrequency ablation is an effective surgical option for the treatment of continuous or intermittent AF. The elimination of AF using radiofrequency ablation is most successful in patients undergoing isolated mitral valve surgery with preoperative left atrial diameter less than 6.0 cm.
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Introduction |
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| Drs Craver, Puskas, and Guyton disclose that they have a financial relationship with Medtronic Corp.
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The Cox-maze procedure and its subsequent modifications have produced durable long-term outcomes for the surgical treatment of atrial fibrillation (AF) [1, 2]. Although the original procedure was described in patients with lone AF, its use has expanded to patients with organic heart disease in addition to AF. However, the perceived technical complexity and longer procedure times inherent to the Cox-maze procedure have prevented its widespread adoption into clinical practice. Intraoperative ablation using radiofrequency energy has been developed to simplify the surgical treatment of AF [3–7]. Similarly, modifications such as the Cox-maze III and mini-maze have been applied to reduce the number of lesion sets required [2, 8]; other modifications limit lesions to only the left atrium [9].
The aim of this study was to determine the efficacy of intraoperative radiofrequency ablation (RFA) performed during concomitant cardiac surgery and to identify variables that may be associated with favorable mid-term success rates.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionAcknowledgmentsReferences |
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Surgical Procedure
A median sternotomy was performed in all patients. All procedures were performed under cardiopulmonary bypass with standard aortic and either bicaval or right atrial cannulation. Cardiac arrest was achieved with antegrade cold blood cardioplegia and moderate hypothermia (28° to 32°C). In those cases not requiring surgery by means of the right atrium, the left atrium was entered directly after dissection of Waterston’s groove. Left atrial ablation lesions were placed before mitral valve repair or replacement as follows (Fig 1): (1) after withdrawing the transesophageal echocardiography probe, individual circumferential ablation lesions were placed around the left and right pulmonary veins, with an interconnecting lesion between both sets of pulmonary veins; (2) a linear ablation lesion was placed from the left pulmonary vein lesion to the left atrial appendage, with a circumferential ablation lesion placed around the orifice of the left atrial appendage; and (3) the final ablation lesion was placed from the left inferior pulmonary vein across the isthmus to the posterior mitral valve annulus. In all cases, anatomic exclusion of the left atrial appendage was performed by either oversewing the orifice of the appendage from within the atrium or by amputating the appendage externally. Subsequently, the mitral valve procedure was performed. Right atrial ablation was performed only when tricuspid annuloplasty or replacement or other procedures requiring right atrial access (atrial septal defect repair) were indicated. Otherwise, RFA was limited to the left atrium. In patients who underwent biatrial ablation, right atrial lesions were placed from the tricuspid annulus to the inferior vena cava and from the tricuspid annulus, across the interatrial septum, and extending to the coronary sinus.
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Follow-Up
The primary end point of this study was freedom from AF at follow-up. The median follow-up time was 8.7 months (range, 3 to 22 months). Follow-up was less than 6 months in 8 of the patients who survived to discharge. Secondary end points included restoration of sinus rhythm, occurrence of adverse events, need for permanent pacemaker, need for anticoagulation and antiarrhythmic medications, and survival. Clinical history was obtained by telephone interview and by contacting referring cardiologists for patient history and electrocardiograms. Sinus rhythm was defined as a supraventricular rhythm with P waves on a 12-lead electrocardiogram. Follow-up was obtained from telephone interviews and from referring cardiologists in all discharged patients (n = 47). Information about rhythm status and medications was obtained in all patients who were alive at latest follow-up (n = 42) and in 2 patients who had expired at latest follow-up. Electrocardiograms were available for 42 of 47 (89.4%) patients. Subgroup analyses were performed to evaluate the effect of variables including duration and type (continuous or intermittent) of AF, type of concomitant procedure, and preoperative left atrial diameter on freedom from AF.
Statistical Analysis
Statistical comparisons between groups were made using either the 
2 or Fisher’s exact test for the categorical items (intermittent versus continuous, isolated mitral valve procedures versus other procedures, and so forth) and the two-sample Student’s t test for quantitative measurements (left atrial size). A p value less than 0.05 was considered statistically significant. Data are expressed as mean ± standard deviation.
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Results |
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Operative and Perioperative Data
Mean cardiopulmonary bypass and aortic cross-clamp times were 159.0 ± 58 minutes (median, 158.5 minutes; range, 84 to 418 minutes) and 104.7 ± 35 minutes (median, 96.5 minutes; range, 51 to 206 minutes), respectively. Mean intensive care unit stay was 103 ± 270 hours (median, 48 hours; range, 19 to 1,720 hours), and mean length of hospital stay was 12 ± 12 days (median, 7 days; range, 4 to 36 days).
Morbidity and Mortality
Six patients required a postoperative pacemaker for sinus or AV node dysfunction before discharge. Two of these patients underwent biatrial ablation procedures whereas 4 underwent left-sided ablation only. There were two (3.7%) postoperative strokes, but there were no instances of postoperative myocardial infarction or esophageal perforation. Five patients (9.3%) required reexploration for bleeding, but none were related to the RFA ablation lines. In-hospital mortality was 12.9% (7 patients), including 2 isolated MVR patients, 1 myomectomy/patent foramen ovale closure/MVR, 1 redo MVR, 1 MVR/aortic valve replacement/tricuspid valve replacement, 1 MVR/coronary artery bypass grafting, and 1 MVR/tricuspid valve replacement.
Follow-Up
At discharge, 33 of 47 (70.2%) patients were free from AF and 30 of 47 (62.5%) patients were in normal sinus rhythm. Three patients who were free from AF at discharge required a pacemaker for sinus bradycardia. Thirty-five patients (74.5%) were discharged on warfarin. Ten patients (21.3%) were discharged on amiodarone and 10 (21.3%) on sotalol according to the protocol previously defined.
At latest follow-up, 34 of 44 (77.3%) patients were free from AF. Of these patients, 29 of 42 (69.0%) were in normal sinus rhythm on electrocardiogram. An additional 3 patients had an underlying sinus rhythm but were paced for sinus bradycardia. Seven patients were discharged in AF but were free from AF at latest follow-up. On the contrary, 6 patients were free from AF at discharge but had recurrent AF at latest follow-up. Three patients required readmission for recurrent AF but were successfully cardioverted. In addition, 23 of 44 (52.3%) and 10 of 44 (22.7%) patients remained on warfarin and antiarrhythmia medication, respectively. Of the five late deaths, only one was directly attributable to a cardiovascular cause, presumably from a fatal arrhythmia. There were no late strokes.
Subgroup Analysis
At late follow-up, patients with preoperative continuous AF had similar rates of freedom from AF compared with those with preoperative intermittent AF (21 of 28, 75.0% versus 13 of 16, 81.3%, respectively; p = 0.72). Moreover, the duration of preoperative AF did not have an impact on outcome with 13 of 18 (72.2%) patients with duration of 5 years or greater free from AF at follow-up compared with 21 of 26 (80.8%) with a duration of less than 5 years (p = 0.72). However, patients with a preoperative left atrial diameter of 6.0 cm or greater had a significantly worse freedom from AF rate compared with those with diameter of less than 6.0 cm (Fig 2).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionAcknowledgmentsReferences |
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Several reports have documented success using radiofrequency energy as the ablative source. Sie and colleagues [4] reported a 79% freedom from AF rate in 200 patients treated with RFA during concomitant cardiac operations with a mean follow-up of 40 months. Other investigators have had success rates of 70% to 90% when using radiofrequency energy to perform atrial ablation with concomitant heart surgery [6, 7, 12]. Overall, 77.3% of our patients who survived to discharge were free from AF, and 69% were in normal sinus rhythm with a median follow-up of 8.7 months. During this period there was a 30% reduction in the use of warfarin and a 47% reduction in the use of antiarrhythmia medication. When patients with mechanical prosthetic valves were excluded, only 31% of patients remained on oral anticoagulation at the discretion of the referring physicians.
With chronic mitral regurgitation, volume conditions on the left atrium are associated with gradual enlargement of the left atrium. These physiologic changes in loading conditions may be responsible for the occurrence of AF in this population. In patients with mitral valve disease and AF, Kargi and associates [5] reported a freedom from AF rate of only 20% in patients with MVR alone compared with 80% in patients with MVR and concomitant RFA. Others have confirmed the low conversion rate (<10%) to an atrial rhythm for patients undergoing mitral valve surgery alone with a history of AF [13, 14].
In this study, patients undergoing isolated mitral valve surgery with RFA had freedom from AF rates of 88%. Others have had similar results when performing Cox-maze III incisions or RFA in combination with mitral valve surgery [2, 4, 5, 13, 15]. Patients who underwent RFA with concomitant procedures other than or in addition to mitral valve surgery had a much lower freedom from AF rate. This may be related to the complexity of additional procedures or the associated pathophysiologic variables (ischemia versus mitral regurgitation) that provide the substrate for AF. Haissaguerre and coworkers [16] identified pulmonary vein foci as the initiating triggers for the majority of AF and concluded that elimination of these triggers with RFA could cure AF. Our results with left atrial RFA combined with isolated mitral valve surgery suggest that comparable rates of freedom from AF can be achieved with left atrial ablation only in patients undergoing mitral valve surgery.
Several reports have documented a higher recurrence rate of AF with increasing left atrial size [12, 17]. In this study, increasing left atrial size (6.0 cm or greater) was associated with significantly higher failure rates compared with those with atrial diameters less than 6.0 cm, regardless of concomitant procedure. Even patients who underwent isolated mitral valve operations failed ablation therapy in 2 of 3 cases when the left atrial diameter was 6.0 cm or greater. Overall, patients with left atrial diameters less than 6 cm had freedom from AF rates of 88.2%. These results suggest that patients with an atrial diameter of 6.0 cm or greater are less likely to benefit from RFA.
In our series, we only performed right atrial ablation procedures if a right atriotomy was indicated for surgery of the tricuspid valve or to repair septal defects. Our primary reason for limiting lesions to the left atrium was to avoid the risk associated with prolongation of ischemia and bypass time and an additional atrial incision. Several investigators have reported excellent results when limiting incisions or ablation lines to the left atrium [12, 17, 18]. Although the risk of atrial flutter, which originates predominantly in the right atrium, is theoretically higher in patients who do not undergo right atrial ablation [8], we did not observe this complication in any of our patients during the postoperative period.
In addition to performing ablation lesions with radiofrequency energy, the left atrial appendage was excluded in all cases, the majority of which were oversewn from within the left atrium. Some authors have advocated preserving the left atrial appendage to simplify the procedure and preserve atrial transport function [17, 19]. Others argue that excluding the atrial appendage is important in preventing thrombus embolization [6]. In our series, there were no late strokes at follow-up, and none of the late deaths occurred as a result of complications of stroke.
The limitations of the present study include the inherent confines of retrospective, nonrandomized data collection. Furthermore, follow-up data were dependent on patient history and cardiology (electrocardiogram) evaluation, which may allow variability secondary to nonuniform assessment. We may have underestimated the recurrence of AF, especially in patients with intermittent AF. In this preliminary study, we did not have further definitive measures of intermittent atrial arrhythmias, such as 24-hour or weekly Holter monitoring. Finally, we did not assess atrial transport function postoperatively, which would be necessary to document whether there is associated atrial contractility with restoration of sinus rhythm.
In conclusion, this observational, retrospective series documents the efficacy of RFA for the treatment of AF during concomitant cardiac surgery. As surgery for AF evolves to include patients with organic heart disease undergoing concomitant procedures, patient selection as well as the risk-benefit of this additional procedure must be considered. We agree with the conclusion of Prasad and colleagues [2] that the Cox-maze operation is the standard against which alternative procedures for AF must be compared. In our experience, left atrial ablation using radiofrequency energy is an effective treatment for patients with mitral valve disease undergoing concomitant repair or replacement. In patients with left atrial diameters less than 6.0 cm, cure rates approaching 90% can be expected with only small increases in procedure and ischemia times. For patients undergoing coronary revascularization or other valvular procedures, the risk of complications must be weighed against the potential benefits and success rates of atrial rhythm restoration. Future studies documenting the success rates of RFA or alternative energy forms for AF therapy will be needed before widespread application of this modality can be applied to more complex cardiac surgical patients.
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Discussion |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionAcknowledgmentsReferences |
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First regarding the large left atrium. Have you had any experience with left atrial reduction and can you speculate on the role that has, especially in this large left atrium population?
The second question is related to Coumadin and medical therapy. Do you oversew the left atrial appendage and how are you dealing with your cardiologists in stopping Coumadin? Do you have any kind of markers of left atrial contractility in follow-up, such as echo, et cetera? Finally, can you just describe your current level of follow-up and how long you keep patients on amiodarone?
DR HALKOS: All very good questions. Let me answer the first one on atrial contractility. Obviously, one of the limitations of the study was that we did not measure postoperative contractile function in these patients to determine whether or not the procedure actually improved atrial transport function.
With regard to left atrial reduction, that was not performed by any of our surgeons. The main reason for this was the reservation about reducing left atrial size and the impact this would have on atrial contraction.
With regard to coumadin, we work very closely with our cardiologists, and they believe that almost all of these patients should be treated with postoperative anticoagulation for some period of time. In addition, some believe that they should be treated with lifelong anticoagulation due to the risk of asymptomatic intermittent atrial fibrillation and its thromboembolic sequelae. We currently believe that most of these patients should be discharged on anticoagulation for at least three months. If sinus rhythm can be documented after this time with serial electrocardiograms or Holter monitoring, then anticoagulation can be discontinued. The fact that we oversew the appendage at least reduces the risk of embolic stroke from this area even without anticoagulation.
DR JOHN H. CALHOON (San Antonio, TX): It was a nicely presented paper. In the people with a large left atrium, that greater than 6 cm, you had a higher recurrence of atrial fibrillation, and yet your paper said that 78% of your patients only had a left-sided ablation procedure. Do you think from your experience that you might extend that to a bilateral maze in those people with a large atrium? Thank you again.
DR HALKOS: Thank you for your question. Our surgeons are comfortable performing a left atrial procedure, ablating the right atrium only if right atrial access is indicated to correct right atrial or septal pathology. We work very closely with our electrophysiologists who are comfortable performing a right atrial ablation via a percutaneous approach if we have problems with atrial flutter or other arrhythmias.
DR CLIFFORD H. VAN METER (New Orleans, LA): I wanted to echo that question, and I have a second question. The first, again, is what were your criteria for selecting patients who needed a right-sided procedure? Did you do preoperative Holters or anything to look for episodes of flutter mixed in with the fibrillation?
And then secondly, I was surprised to see that your success rate was lower in the patients with intermittent atrial fibrillation, because many who have proposed pulmonary vein isolation only protocols to ablate intermittent atrial fibrillation have hypothesized a success rate in excess of 95%. So that would imply that that is either an unwise hypothesis or that perhaps bipolar rather than unipolar therapy would be the way to go in that study.
Could you comment on those, please?
DR HALKOS: With regard to your last question, this study may be underpowered to detect statistically significant differences in some variables. I cannot speculate on whether a bipolar device would be more effective than the unipolar device, but the conclusion from our data was that there was no significant difference in outcome with regard to the preoperative type of atrial fibrillation (continuous versus intermittent). In response to your first question, a right atriotomy was performed only in those patients who required right atrial access to address tricuspid or septal pathology. None of our patients had preoperative documentation suggesting atrial flutter.
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