Asian Cardiovasc Thorac Ann 2004;12:272-277
© 2004 Asia Publishing EXchange Ltd
Radiofrequency Ablation for Atrial Fibrillation: Different Approaches
Bruno Chiappini, MD,
Roberto Di Bartolomeo, MD,
Giuseppe Marinelli, MD
Department of Cardiovascular Surgery, Policlinico S. Orsola-Malpighi, University of Bologna, Bologna, Italy
For reprint information contact: Bruno Chiappini, MD Tel: 39 347 514 7032 Fax: 39 051 345 990 Email: bruno_chiappini{at}hotmail.com Department of Cardiovascular Surgery, Policlinico S. Orsola-Malpighi, Via Massarenti 9 – 40138, Bologna, Italy.
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ABSTRACT
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The existing literature regarding radiofrequency ablation for the surgical treatment of atrial fibrillation was reviewed, analyzing the early and late results. A MEDLINE search supplemented with a manual bibliographic review was performed for all peer-reviewed English language articles regarding the use of radiofrequency ablation for the treatment of atrial fibrillation. Six studies were identified, with a total of 451 patients. None of the studies was completely randomized. All patients underwent radiofrequency ablation as an adjunct to a variety of cardiac surgical procedures. The hospital mortality rate was 2.7%. The overall survival rate was 97.1%, and freedom from atrial fibrillation was 76.3% ± 5.1% after a mean follow-up period of 13.8 ± 1.9 months. It was concluded that radiofrequency ablation should be considered a safe and effective means to cure atrial fibrillation in patients undergoing open heart surgery.
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INTRODUCTION
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Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice. It affects nearly 1% of the general population, with a striking increase in incidence in patients older than 60 years. The most widely accepted surgical treatment for AF is the maze procedure, developed by James Cox in the mid 1980s.1 The operation is performed with multiple full-thickness cuts and sutures within the atrial walls, disrupting the abnormal reentry pathways.2 Although the maze III procedure is recognized as an effective treatment for AF, it is lengthy and technically demanding.3,4 Therefore, efforts are being made to find alternative means of creating full-thickness continuous linear incisions that preclude the ability of the atria to fibrillate. The following literature review includes an analysis of the current clinical application of radiofrequency (RF) for the surgical treatment of AF.
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TIME-RELATED MECHANISM OF RF
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Radiofrequency catheter ablation is a technique whereby high-frequency alternating electrical current with frequencies of 350 kHz to 1 MHz is delivered through electrode catheters to myocardial tissue, creating a thermal lesion. The mechanism by which RF power heats the tissue is resistive heating of a narrow rim of tissue in direct contact with the electrode. Deeper tissue planes are then heated by conduction from the small region of volume heating. Heat is dissipated from the region by conduction into normothermic tissue and by convection via the circulating blood pool and larger coronary vessels. The lesion size is proportional to the temperature at the electrode-tissue interface and to the size of the electrode. At temperatures above 100°C, boiling occurs at the electrode-tissue contact point, resulting in a rapid rise in electrical impedance.5 Heat propagation is based on resistive and passive mechanisms. In the immediate proximity of the probe, tissue is heated to 50°C–60°C with consequent coagulation and irreversible destruction of cells and collagen structures. Further away from the probe, the resistance offered by tissue decreases exponentially and the heat rapidly decreases. Thus, ablation of the peripheral portion of the lesion results from passive heating, with irreversible damage being achieved over a longer period of time. A few weeks after RF application, the formation of scar is noted with a similar width and depth up to 8–10 mm, and with blunt edges.6 Once transmural ablation is achieved, the effects of the RF lesions are the same as those of other major techniques, with effective ablation of atrial muscle, an antiarrhythmic effect, and no significant pro-arrhythmic activity from the scar tissue.
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LITERATURE REVIEW
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A comprehensive literature review was undertaken using a MEDLINE search of "radiofrequency ablation" and "atrial fibrillation" from 1997 to July 2003, supplemented with manual bibliography reviews. All peer-reviewed studies, published in the English language, regarding the surgical treatment of AF by RF ablation were identified and reviewed. Studies containing data that was duplicated in latter publications from the same institution were excluded. Six publications were identified, which reported results from patients suffering from AF and an organic heart disease requiring surgery (Table 1
). All data were extracted from the studies and entered into a computer file. It should be stressed that none of the studies were randomized clinical trials; they were all retrospective observational studies of cohorts of consecutive patients with concomitant RF ablation and open heart surgery. The 6 studies included 451 patients who had an indication for cardiac surgery irrespective of AF. The preoperative characteristics of the patients are shown in Table 1. All atrial incisions currently used in the Cox maze procedure were replaced by linear ablation lines with the use of different devices, except for the incisions to enter the left and right atrial cavity.
In the studies by the groups of Patwardhan,7 Sie,9 and Guang,11 the RF probe was applied on the endocardium of the left and right atria. After both caval cannulas were snared, the right atrium was opened through a posterior longitudinal incision starting caudally of the superior vena caval cannulation site at the dorsolateral aspect of the right atrium. This incision was extended along the border of the interatrial septum, slightly curved, and finally ended at the atrioventricular groove opposite the inferior vena caval cannulation site. The right atrial appendage was excised, and an anterior incision was made from the middle of the anterolateral aspect of the base of the amputated auricle toward the inferior vena caval orifice. Radiofrequency energy was then used to extend the electrical block caused by the first surgical incision cranially as far as possible toward the superior vena caval cannulation site and caudally toward the inferior vena caval cannulation site. Additional RF ablation lines were drawn from the medial aspect of the base of the excised right atrial appendage into the annulus of the tricuspid valve, and from the caudal end of the first surgical incision at the atrioventricular groove to the posterior part of the annulus of the tricuspid valve. This part of the procedure was performed on a beating heart without crossclamping. Access to the inside of the left atrium was gained via a standard atriotomy in the interatrial groove. After excision of the left atrial appendage and suturing of the amputation site, the left-sided maze procedure was performed with linear ablation lines around the ostia of the pulmonary veins. Ablation lines were also extended from the ablation line isolating the left pulmonary vein to the base of the left atrial appendage amputation site and to the posterior mitral valve annulus. According to the technique of Melo and colleagues,8 the RF probe was applied only in the left atrium to perform endocardial bilateral isolation of the pulmonary veins, and after RF ablation was completed, the left atrial appendage was surgically excluded, tying it from the outside. Benussi and colleagues10 also performed RF ablation on the left side only, but by an epicardial approach: a posterior semicircular ablation around the orifices of the right pulmonary veins was performed epicardially off-pump.After institution of cardiopulmonary bypass, the operating table was tilted 15 degrees to the right, and the heart was gently lifted toward the surgeon to expose the left pulmonary veins. The Marshall fold was divided with diathermy, and an encircling lesion was produced around the orifices of the left pulmonary veins. The left encircling line was then connected with the base of the left appendage through another epicardialablation. After aortic crossclamping, the heart was arrested and isolation of the right pulmonary veins was completed by a standard left atriotomy. Two linear ablations were performed endocardially. The first connected the two encircling ablations on the posterosuperior atrial wall. This lesion was kept cranial, opposite the transverse sinus, to prevent any possible damage to the esophagus. The last ablation connected the left appendage to the posterior aspect of the mitral annulus. The auricle was then excluded with a double-layer running 4/0 polypropylene suture (Figure 1A).
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Figure 1. (A) The left atrial procedure showing encircling of the pulmonary veins and the cutting and sewing of the left atrial appendage. (B) The right atrial procedure showing isolation of the isthmus of the inferior vena cava.
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Raman and colleagues12 recently described the usefulness of right-sided ablation in addition to lesions on the left atrium. They created right-sided lesions epicardially on the surface of the right atrium with the heart beating and ejecting on cardiopulmonary bypass. A single lesion was created roughly along the crista terminalis, from the superior vena cava to the inferior vena cava. A connecting lesion was then created from the lower end of this lesion to the atrioventricular groove, low down opposite the orifice of the coronary sinus, to create a block in the cavotricuspid isthmus area (Figure 1B
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Three hundred and twenty-five (72%) patients underwent mitral valve surgery, of whom 152 (47%) had mitral valve repair and 173 (53%) had mitral valve replacement. Associated procedures are shown in Table 2. One hundred twenty-six (28%) patients underwent other cardiac surgical procedures not involving the mitral valve (Table 2). The additional ischemic time needed to perform RF ablation was 11.8 ± 3.6 min. There were 12 (2.7%) hospital deaths (Table 3). The nonfatal hospital complications were repeat thoracotomy (19), low cardiac output requiring an intraaortic balloon pump (7), sternal wound infection (2), pneumothorax (2), endocarditis (1), stroke (1), and gastrointestinal bleeding (1). No severe arrhythmias were observed postoperatively, and 4 (0.8%) patients required implantation of a dual-chamber pacemaker. All surviving patients were monitored for at least 3 months and up to 65 months after surgery. The mean follow-up period was 13.8 ± 1.9 months. The overall survival rate was 97.1%. There were 13 (2.9%) late deaths including 7 cardiac, 1 unspecified, and 5 non-cardiac-related deaths. Because of early recurrences of AF, all authors chose to analyze the incidence of AF after the first 3 postoperative months. Among 426 survivors, 325 (76%) were in sinus rhythm, 17 (4%) had atrial rhythm, 7 (1.6%) received an atrioventricular sequential pacemaker, and 67 (16%) remained in AF. The overall freedom from atrial fibrillation was 76.3% ± 5.1%. Benussi and colleagues10 reported 10 patients who experienced typical counterclockwise atrial flutter at 9 ± 6.3 months after surgery. No preoperative factor, including the presence of tricuspid disease, was significantly related to postoperative flutter. All patients with fl utter underwent an electrophysiologic study and were successfully cured by RF ablation of the cavotricuspid isthmus.
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DISCUSSION
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Patients with mitral valve disease often suffer from AF which impairs cardiac performance and predisposes them to systemic embolism. Many factors such as a long history of AF, increased atrial size, and advanced age tend to result in persistent AF even after a successful mitral valve operation and electrical cardioversion.13–16 When AF is not treated during surgery, the rate of spontaneous recovery of sinus rhythm is in the range of 15% to 20%.17,18 Even with extensive use of antiarrhythmic drugs and electrical cardioversion, the reported rates of late sinus rhythm maintenance remain below 25%.19,20 Therefore, restoration of normal sinus rhythm is highly desirable for patients in AF. Cox maze procedure is successful in converting the majority of patients with AF to normal sinus rhythm; however, the procedure is time-consuming. Cox and colleagues21,22 reported that in 59 patients undergoing the maze procedure alone without additional valve surgery, the cardioplegic arrest time averaged 68 min (range, 50–102 min) and the cardiopulmonary bypass time averaged 182 min (range, 130–256 min). It should be noted that the additional ischemic time needed to perform RF ablation was 11.8 ± 3.6 min in the 6 studies analyzed. Postoperative bleeding is a complication related to the Cox procedure because of the extensive incisions, with a reported incidence of reoperation of 7%–8%.22–25 In our review, a repeat thoracotomy was performed in 19 (4%) patients because of postoperative bleeding, suggesting that RF ablation may decrease the possibility of bleeding from the heart. Approximately 20% of patients needed permanent pacemaker implantation after the Cox maze procedure.21 We found that 7 (1.6%) patients in the 6 studies received a permanent pacemaker. Possible reasons include the fact that in the maze III procedure, the left atrial dome incision is moved more posteriorly. This causes the atrial septotomy to be moved more posteriorly also, addressing the chronotropic incompetence of the sinus node; in the maze operation, left atrial incisions are performed, so the possibility of injury to the sinus blood supply from the left coronary artery is high and sinus node function can be compromised.
In the study by Patwardhan and colleagues,7 15 survivors in the coagulation maze group were followed-up from 43 to 224 days and 12 (80%) of them converted to normal sinus rhythm; atrial transport function studies with pulsed-wave Doppler showed the presence of a wave in tricuspid valve flow in all 12 (100%) patients, and in mitral valve flow in 9 (75%) patients. The procedure took 11.62 ± 3.86 min of elective cardioplegic arrest for the left atrial portion, and 18.71 ± 4.25 min on cardiopulmonary bypass during reperfusion for the right atrial portion; thus, the time taken for creating lesions was considerably shortened with good results. Melo and colleagues8 described the results of AF surgery using the Santa Cruz scores. Briefly, score 0 is defined as persistence of AF (failure); score 4 is attributed when normal sinus rhythm with bilateral atrial contraction is achieved (success). Scores 1, 2, and 3 include intermediate, less successful grades, where AF is absent but normal sinus rhythm is not attained. In score 1, the atria do not contract and are hemodynamically silent. In score 2, only the right atrium is beating, and in score 3, both atria contract but without sustained sinus rhythm. According to this system, 36% of patients remained in AF (Santa Cruz score 0), 30% had score 4, 18% had score 3, 6% had score 2, and 9% had score 1. In the study of Benussi and colleagues,10 the mean cardiac arrest time for open heart ablation was significantly shorter (5.2 ± 0.9 min) when the epicardial approach was used (107 of 132 patients, 81%). Hospital mortality was 0.8% and sinus rhythm was restored in 77% of patients. Overall 3-year survival was 94%. The 3-year actuarial freedom from stroke was 98%. No patient required implantation of a permanent pacemaker. Atrial contraction recovered in all patients with stable sinus rhythm. In the report of Raman and colleagues,12 3 patients required defibrillation within the first 3 months postoperatively and have since stayed in sinus rhythm; one patient had late atrial flutter that was cardioverted to sinus rhythm. The sinus recovery rate was 93.7% (15 of 16 patients) at 6 months, and 100% in 8 patients reviewed at 12 months. To the best of our knowledge, this is the first detailed analysis of the use of RF ablation for the treatment of AF. The results of the 6 most important studies published on this topic suggest that the use of RF ablation intraoperatively is an effective method for the treatment of AF, with substantial benefits from restored atrial rhythm.
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REFERENCES
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- Cox JL, Schuessler RB, D’Agostino HJ Jr, Stone CM, Chang BC, Cain ME, et al. The surgical treatment of atrial fibrillation. III. Development of a definitive surgical procedure. J Thorac Cardiovasc Surg
1991;101:569–83.[Abstract]
- Cox JL, Jaquiss RDB, Schuessler RB, Boineau JP. Modification of the maze procedure for atrial flutter and atrial fibrillation. II. Surgical technique of the maze III procedure. J Thorac Cardiovasc Surg
1995;110:485–95.[Abstract/Free Full Text]
- Cox JL, Sundt TM 3rd. The surgical management of atrial fibrillation. Annu Rev Med
1997;48:511–23.[Medline]
- Cox JL, Ad N, Palazzo T, Fitzpatrick S, Suyderhoud JP, DeGroot KW, et al. Current status of the maze procedure for the treatment of atrial fibrillation. Semin Thorac Cardiovasc Surg
2000;12:15–9.[Medline]
- Haines DE. The biophysics of radiofrequency catheter ablation in the heart: the importance of temperature monitoring. Pacing Clin Electrophysiol
1993;16:586–91.[Medline]
- Viola N, Williams MR, Oz MC, Ad N. The technology in use for the surgical ablation of atrial fibrillation. Semin Thorac Cardiovasc Surg
2002;14:198–205.[Medline]
- Patwardhan AM, Dave HH, Tamhane AA, Pandit SP, Dalvi BV, Golam K, et al. Intraoperative radiofrequency microbipolar coagulation to replace incisions of maze III procedure for correcting atrial fibrillation in patients with rheumatic valvular disease. Eur J Cardio-thorac Surg
1997;12:627–33.[Abstract]
- Melo J, Adragao P, Neves J, Ferreira MM, Pinto MM, Rebocho MJ, et al. Surgery for atrial fibrillation using radiofrequency catheter ablation: assessment of results at one year. Eur J Cardio-thorac Surg
1999;15:851–5.
- Sie HT, Beukema WP, Misier AR, Elvan A, Ennema JJ, Haalebos MM, et al. Radiofrequency modified maze in patients with atrial fibrillation undergoing concomitant cardiac surgery. J Thorac Cardiovasc Surg
2001;122:249–56.[Abstract/Free Full Text]
- Benussi S, Nascimbene S, Agricola E, Calori G, Calvi S, Caldarola A, et al. Surgical ablation of atrial fibrillation using the epicardial radiofrequency approach: mid-term results and risk analysis. Ann Thorac Surg
2002;74:1050–7.[Abstract/Free Full Text]
- Guang Y, Zhen-jie C, Yong LW, Tong L, Ying L. Evaluation of clinical treatment of atrial fibrillation associated with rheumatic mitral valve disease by radiofrequency ablation. Eur J Cardio-thorac Surg
2002;21:249–54.[Abstract/Free Full Text]
- Raman JS, Ishikawa S, Power JM. Epicardial radiofrequency ablation of both atria in the treatment of atrial fibrillation: experience in patients. Ann Thorac Surg
2002;74:1506–9.[Abstract/Free Full Text]
- Waris E, Kreus KE, Salokannel J. Factors influencing persistence of sinus rhythm after DC shock treatment of atrial fibrillation. Acta Med Scand
1971;189:161–6.[Medline]
- Henry WL, Morganroth J, Pearlman AS, Clark CE, Redwood DR, Itscoitz SB, et al. Relation between echocardiographically determined left atrial size and atrial fibrillation. Circulation
1976;53:273–9.[Abstract/Free Full Text]
- Sato S, Kawashima Y, Hirose H, Nakano S, Matsuda H, Shirakura R. Long-term results of direct-current cardioversion after open commissurotomy for mitral stenosis. Am J Cardiol
1986;57:629–33.[Medline]
- Hansen JF, Andersen ED, Olesen KH, Steiness E, Lyngborg K, Andersen JD. DC-conversion of atrial fibrillation after mitral operation: an analysis of the long-term results. Scand J Thorac Cardiovasc Surg
1979;13:267–70.[Medline]
- Chua YL, Schaff HV, Orszulak TA, Morris JJ. Outcome of mitral valve repair in patients with preoperative atrial fibrillation. Should the maze procedure be combined with mitral valvuloplasty? J Thorac Cardiovasc Surg
1994;107:408–15.[Abstract/Free Full Text]
- Jessurun ER, van Hemel NM, Kelder JC, Elbers S, de la Rivière AB, Defauw JJ, et al. Mitral valve surgery and atrial fibrillation: is atrial fibrillation surgery also needed? Eur J Cardio-thorac Surg
2000;17:530–7.[Abstract/Free Full Text]
- Crijns HJ, Van Gelder IC, Van der Woude HJ, Grandjean JG, Tieleman RG. Efficacy of serial electrical cardioversion therapy in patients with chronic atrial fibrillation after valve replacement and implications for surgery to cure atrial fibrillation. Am J Cardiol
1996;78:1140–4.[Medline]
- Kalil RAK, Maratia CB, D’Avila A, Ludwig FB. Predictive factors for persistence of atrial fibrillation after mitral valve operation. Ann Thorac Surg
1999;67:614–7.[Abstract/Free Full Text]
- Cox JL, Boineau JP, Schuessler RB, Kater KM, Ferguson TB Jr, Cain ME, et al. The electrophysiologic basis, surgical development and clinical results of the maze procedure for atrial fl utter and atrial fibrillation. Indian J Thorac Cardiovasc Surg
1994;10:9–38.
- Cox JL, Boineau JP, Schuessler RB, Kater KM, Lappas DG. Five-year experience with the maze procedure for atrial fibrillation. Ann Thorac Surg
1993;56:814–24.[Abstract]
- Cox JL, Boineau JP, Schuessler RB, Jaquiss RD, Lappas DG. Modification of the maze procedure for atrial flutter and atrial fibrillation. I. Rationale and surgical results. J Thorac Cardiovasc Surg
1995;110:473–84.[Abstract/Free Full Text]
- Kosakai Y, Kawaguchi AT, Isobe F, Sasako Y, Nakano K, Eishi K, et al. Cox maze procedure for chronic atrial fibrillation associated with mitral valve disease. J Thorac Cardiovasc Surg
1994;108:1049–55.[Abstract/Free Full Text]
- Kosakai Y, Kawaguchi AT, Isobe F, Sasako Y, Nakano K, Eishi K, et al. Modified maze procedure for patients with atrial fibrillation undergoing simultaneous open heart surgery. Circulation
1995;92(Suppl II):359–64.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
