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© 2003 European Association of Cardio-Thoracic Surgery
Surgical treatment of permanent atrial fibrillation during heart valve surgery
a Department of Cardiac Surgery, AK St.Georg, Lohmühlenstraße 5, 20099 Hamburg, Germany
* Corresponding author. Tel.: +49-40-2890-4150; fax: +49-2890-4184 Received August 28, 2002; received in revised form January 6, 2003; accepted January 10, 2003
A simple strategy to abolish permanent atrial fibrillation (AF) in patients undergoing heart valve surgery is described. The concept includes: (1) endocardial radiofrequency (RF) ablation creating two encircling isolation lesions around the left and the right pulmonary veins (LPV, RPV) and a connection line between both; (2) antiarrhythmic protection with amiodarone for 3 months. Between 02/01 and 02/02 29 patients underwent surgical AF ablation procedures associated with primary valve operations (mitral,  ; aortic,  ; aortic+mitral,  ). Six months after surgery 87.5% (14 of 16) were in sinus rhythm (SR), particularly all patients with an LA diameter of <56mm had SR.
Key Words: Atrial fibrillation; Atrial fibrillation surgery; Radiofrequency ablation; Arrhythmia surgery; Heart valve surgery; Maze surgery
Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia treated in clinical practice. In cardiac surgery, permanent AF is exceptionally important because of two reasons: it is (1) found in patients who need open heart surgery for other reasons [1]; and (2) associated with significant morbidity and related to poorer survival rates compared to patients with SR [2]. Since Cox has demonstrated that AF can be definitely eradicated [3], efforts were made to achieve less invasive and time consuming methods. Intraoperative surgical catheter ablation became a challenge for the treatment of AF in combination with open heart surgery. Considering the broad spectrum of modified intraoperative ablation techniques which have been presented recently, particularly the pattern of ablation lines and the type of energy are matter of concern [4–8].
The relative frequency of permanent AF (following the classification of the ACC/AHA/ESC Practice Guidelines [9]) which had been documented to persist for a period of at least 6 months among all patients undergoing open heart surgery in our department between 02/01 and 02/02 was evaluated. Particularly in patients with heart valve disease, the presence of permanent AF was analysed. Etiology of heart valve disease was assessed by clinical history, intraoperative valve examination and histologic analysis. Patients hospitalised for heart valve surgery with permanent AF underwent combined intraoperative AF treatment with RF ablation. Patients with any other form of AF (paroxysmal or permanent lasting less than 6 months), emergency operation, acute bacterial endocarditis, cachexia (body mass index (BMI)  24), severe intracavitary thrombosis or extreme left atrial size were excluded (LA diameters of  72mm were assessed to be our limit for the procedure). 2.1. Surgical procedure To create endocardial RF ablation lesions either the Thermaline® device or (since 01/02) the Cobra® device (both Boston Scientific Corporation, San Jose, USA) were used. Both almost identical systems consist of a flexible electrosurgical probe with seven electrode terminals for separate or combined use, a generator of RF energy, an ablation controller and connecting cables including two indifferent patch electrodes. Ablation was performed using 100W RF power for 120s, energy was delivered in a monopolar fashion. The local temperature (measured by integrated thermocouples) was set at 70°C. The first lesion line completed the isolation of the RPVs from the inferior to the superior RPV using the left atriotomy. Isolation of the LPVs was performed with a semicircular ablation line close to the inferior, and another one around the superior LPV. These were connected by a transverse lesion across the posterior wall of the LA (Figs. 1 and 2).
Precautions were taken to avoid thermic esophageal injury as follows: (1) cachectic patients were excluded; (2) a dry compress was passed behind the LA before delivery of RF energy; (3) the transesophageal echocardiogram (TEE) probe was removed during the ablation procedure; (4) a flexible ablation probe was used and adapted to the tissue without pressure; (5) local temperature was set at only 70°C; and (6) RF ablation was performed precisely under direct view during conventional open heart valve surgery only. 2.2. Perioperative management, follow-up and statistical analysis Standard 12-lead electrocardiogram (ECG) and transthoracic echocardiogram (TTE) were routinely performed on admission and before discharge. Preoperative LA diameter was evaluated by TTE. Administration of amiodarone was started with an intravenous bolus of 300mg before end of cardiopulmonary bypass followed by an infusion of 900mg/day for 3 days. The oral administration of 5x200mg/day up to 7–10g dependent of body weight was begun, 1x200mg/day followed for 3 months. Patients with postoperative bradycardia were externally paced and antiarrhythmic drug administration continued. Persisting bradycardia for more than 10 days lead to a termination of amiodarone. An indication for permanent pacemaker implantation was persisting bradycardia for 2 weeks. Early recurrence of AF was DC cardioverted after saturation with amiodarone. Heparin was administered after resolution of postoperative bleeding. Patients with mitral valve (MV) repair or bioprosthetic valves got cumarine for 3 months, patients with mechanical valves lifelong anticoagulation.All patients were restudied 6 weeks, 3, 6, 9 and 12 months after surgery by standard 12-lead ECG and clinical examination. Quantitative preoperative and operative data were normally distributed and described by arithmetic mean±standard deviation; qualitative distributed data were presented as absolute frequencies. For permanent AF the relative frequency among all patients and some subgroups and the directional measure lambda to indicate the reduction in the prediction error were calculated. Qualitative characteristics were compared using the exact Fisher chi-square test. All P-values were two-tailed and interpreted nominal, that is not adjusted for multiple comparisons. P-values <0.05 were considered to be statistically significant. Analysis was performed with SPSS for Windows 9.0.1.
3.1. Relative frequency of permanent AF The incidence of permanent AF among all patients undergoing open heart surgery was 3.6% (Table 1). In the group of heart valve operations permanent AF was prevalent in 10.1% compared with 0.98% in the group of non heart valve operations  . The relative frequency in patients with MV disease was 33.7%, followed by combined MV and aortic valve (AV) disease (23.1%) and AV disease (2.2%). In the MV group 17 of 34 patients with rheumatic valve disease had permanent AF and 12 of 52 with non-rheumatic valve disease. There was a statistically significant association between type of MV disease and permanent AF  but no reliability in predicting the type of MV disease by the knowledge of permanent AF  .
3.2. Clinical results The relevant preoperative data and details of surgery are given in Table 2. Twenty-nine patients underwent surgical AF ablation procedures (Thermaline® device:  , Cobra® device:  ) associated with primary valve operations (MV, ; AV, ; AV+MV, ), nine were excluded. The main group suffered from rheumatic heart valve disease (18/29). Mean LA diameter was 55.9±7.3mm, 18 patients had a small (<56mm) and 11 patients a large LA (56mm). There were no severe early postoperative complications, no pacemaker-implantation had to be performed. There were no cases of hospital mortality. Mean follow-up time up to 02/02 was 6.7±4.2 months. Six weeks after surgery every third patient was in AF, but at 3 months 18 of 21 patients had SR (6 months, 14 of 16; 87.5%). After 9 months 12 of 13 (92.3%) were in SR (12 months, 5/5). Early postoperative return of AF (18/29) occurred mainly during the first 3 months (17/18) and was DC cardioverted in 11 of 18 cases; four turned to SR spontaneously later. Preoperative duration of AF was not predictive for long-term results. Particularly all patients with small preoperative LA had SR after 6 months. Six months after surgery 11 of 13 patients which had an implantation of a bioprosthesis or valve repair needed no anticoagulation, nine of 16 patients took no antiarrhythmics.
4.1. Rationale of surgical practices to treat permanent AF The goal in patients with AF is restoration and maintenance of SR. Particularly permanent AF has multiple clinical consequences: (1) a loss of atrial contraction and rapid ventricular rate without adequate ‘AV-synchronisation’ results in reduced cardiac output and potential heart failure [10]; (2) it is associated with a five times higher risk of stroke and a two times higher rate of death in all patients [2]; and (3) the risk of thrombembolic complications by bloodpooling in the atria forces systemic anticoagulation with the risk of bleeding. Already in 1962 Moe presented a remarkable concept to explain the pathophysiology of AF [11]. His most widely accepted ‘multiple wavelet hypothesis’ still represents the basis for almost all efforts to cure AF. He proposed that AF is a consequence of multiple independent reentrant wavelets which spread through the atrium. Allessie indicated that only six wavelets are necessary to sustain AF [12]. The Cox-maze procedure and many of its modifications were based on Moe's concept and demonstrated efficiency to abolish AF [3]. The principles are: (1) PV isolation, (2) reduction of atrial size and (3) block of reentrant wavelets by complex incisions. But even if success rates of almost 90% have been described, the method is avoided by most surgeons because of its complexity. In the early 1990s, it was confirmed that RF energy could be used for a less complex surgical ablation procedure to create transmural atrial lesions. Preliminary clinical experiences were reported in the late 1990s [4] and in 1999 microwave energy was recommended alternatively [6]. However, the early results were far away from the success rates of the Cox-maze procedure. In 1998 Haissaguerre described the demonstration of an important pathophysiologic finding that the initiation of AF originates from rapidly firing foci predominantly located inside the PVs [13]. According to that the concept was developed that isolation of the PVs creating transmural encircling RF ablation lesions around the LPVs and the RPVs should be a sufficient basis for surgical RF ablation procedures. To save LA function and to bar potential generation of foci the maze pattern of multiple incisions was reduced to a short connection line between both. Radiofrequency ablation was performed from the endocardial side with a direct view on the atrial tissue to guaranty continuity of the lesions. Amiodarone was given to reduce postoperative recurrence of AF [14]. 4.2. Evaluation of the results Compared with the literature the described data confirm the relative frequency of permanent AF. While the rate was low in cases without severe heart valve disease, a significantly higher presence of permanent AF in patients scheduled for heart valve surgery was observed. The occurrence was particularly high in patients with rheumatic MV disease. This potential relationship of permanent AF and etiology could be interpreted by the long-standing processes underlying rheumatic MV disease. Pathologic structural changes over decades may cause permanent AF, whereas non-rheumatic diseases commonly do not. MV disease in general, particularly with major regurgitation, is associated with LA enlargement by dilatation and hypertrophy, which is a risk factor for AF.Even if our patients were approximately a decade older compared to patients of others [7,8], surgery was tolerated well. Particularly no case of esophageal injury, which was described as a rare but fatal complication because of too deep RF ablation lesions [15], was observed. In congruity with others the proportion of SR increased during the following months after surgery [7,8]. It can be suggested that 3 months administration of amiodarone is appropriate but should be handled flexible. According to the data of Melo [8], which termed LA size to be a prognostic factor for long-term results after RF ablation, patients with small LA diameter were in SR in the late follow-up. We interprete the results particularly on the basis researches of Cox [3], Moe [10], and Haissaguerre [13]: AF wavelets sustained by foci located inside the PVs were blocked by the created lesions, the described antiarrhythmic protection supported SR during the unstable initial stage, which was approximately 3 months. We recommend a DC cardioversion in the case of AF return, however, the influence on the long-term results should be clarified soon. As for MV surgery the LA has to be opened anyhow we strongly recommend an endocardial ablation technique for these patients. Further investigations have to show, if epicardial approaches are more recommendable in the AV cases. However, so far we have used the method only in a small number of patients. Whereas continuity of the created lesions was controlled by direct view, transmurality is presumptive but not guaranteed, follow-up time was short. For rhythm evaluation only 12-lead ECG was used. We consider to complete the follow-up data by performing a 24-h-ECG registry to assess the possibility of paroxysmal AF. The data were not evaluated under randomised conditions. We suggest that the described concept provides a successful treatment of permanent AF in patients undergoing heart valve surgery. It fulfills all demands of an effective and easy to handle method, simplifies the treatment of permanent AF and can be recommended in patients undergoing heart valve surgery. The advantages compared to other techniques are: (1) no additional incisions are required apart from the left atriotomy; (2) the procedure is easy to practice; and (3) atrial tissue trauma is extremely slight.
ICVTS on-line discussion Author: Mr. Joel Dunning, RCS Research Fellow, Cardiothoracic Surgery, Manchester Royal Infirmary, Oxford Road, Manchester M13 3BW, UK Date: 19-Mar-2003 00:01 Message: The authors are to be congratulated on their excellent results, with a restoration of Sinus Rhythmn of 87%. The authors refer to the original concepts of the Cox-Maze procedure, which includes the principal that reduction of left atrial size is ofbenefit in patients with chronic AF. There have been some concerns in the literature that radiofrequency ablation may impair contractility of the left atrium despite restoration of sinus rhythm and RF ablation certainly does not address the problem of the reduced contractility of the enlarged or giant left atrium. Jansz et al [1] in Australia have recently described a novel left atrial reduction technique whereby the left atriotomy is extended circumferentially, and after the mitral valve procedure an equatorial rim of left atrium is excised, including the left atrial appendage. Closure of the atriotomy reduces LA size and also isolates the pulmonary vein orifices. They report that 57 of 62 (92%) patients with chronic AF and enlarged LA are restored to sinus rhythm and they are in the process of quantitively measuring the improved contractility that is observed by echocardiography. They also report that the additional cross-clamp time spent performing this procedure is compensated for by the time saved due to the excellent exposure gained to the mitral valve. Thus, perhaps for a clinician searching for a less invasive way to treat patients in AF undergoing Mitral valve surgery, Geidel et al present the optimal method for patients without gross LA enlargement and Jansz et al provide us with a simple surgical option in those with larger left atria. 1. Jansz P, Bennetts J, Wilson M, Spratt P, Farnsworth A. Restoration of Sinus Rhythmn Following Mitral Valve Surgery with Left Atrial Reduction In Patients with Chronic Atrial Fibrillation. Abstract 38, Annual Scientific Meeting of the Society of Cardiothoracic Surgeons of Great Britain and Ireland, 2003. Response Author: Dr. Stephan Geidel, Cardiac Surgeon, AK St.Georg, Dept. of Cardiac Surgery, Lohmühlenstraße 5, Hamburg 20099, Germany Date: 26-Mar-2003 05:15 Message: The supposed influence of the LA size on the success rates after RF ablation surgery for permanent AF finally raises the question, whether the LA size itself is the critical issue. We think that progressive enlargement and hypertrophy of the atria is normally connected with cellular and structural morphologic changes and in parallel with electrophysiologic changes in the atrial tissues as well. This electrical and anatomic "atrial remodeling" may lead to what has been described as "AF begats AF". We are planning to focus our interest on those structural and electrophysiologic changes which occur with progressive LA enlargement. Author: Dr. Fernando Hornero, Cardiac Surgeon, Hospital General Universitario de Valencia, Cardiac Surgery, Av. Tres Cruces s/n, Valencia 46014, Spain Date: 31-Mar-2003 06:03 Message: The last modifications in atrial fibrillation (AF) surgery and the new intraoperative ablation methods allow for a more frequent AF treatment combination among cardiac surgery patients. Different studies have been reported in the literature with the use of intraoperative radiofrequency (RF) ablation. These studies considered a heterogeneous population and used different ablation techniques that consisted of multiple RF lesions in the left and / or right atria. Probably heterogeneous cardiac population is different among countries. In our experience, the preoperative incidence of permanent AF in an adult Cardiac Surgery Unit in Spain is 13.6%, analysed retrospectively 3550 patients operated on in the past 8 years. The permanent AF incidence varied depending on the pathology: 2.2% in CAD patients; 38.5% in heart valve disease patients (12.4% aortic, 63.9% mitral, 57.1% mitral-aortic, 91.6% mitral-tricuspid, 78.5% mitral-aortic, and 66.6% tricuspid); 19.8% in CAD and heart valve mixed pathology, 11.5% in adult congenital heart disease, and 20% in pericardial disease. In our experience, 20% of permanent preoperative AF patients present non-mitral cardiac pathologies. > Potentially diverse electrophysiological mechanisms and substrates exist in different patient populations. Valvular heart disease, particularly mitral valve disease, results in increased atrial chamber pressures, atrial stretch, increased atrial size, atrial muscle disruption, and fibrosis. These patients have sufficient electrophysiological substrate to initiate and maintain AF, even in the absence of pulmonary vein ectopics. It is likely that rapid atrial arrhythmias anchoring around anatomical orifices degenerate into AF in this patient population. A variety of RF surgical protocols have been reported in the literature. Your experience, with surgical protocol based in bilateral pulmonary veins isolation by intraoperative radiofrequency ablation, suggests that although the atria as a whole participate in the process of AF, not all the parts of the atria contribute equally to the perpetuation of the fibrillatory process. There are several interesting questions in this paper, which remain unanswered. Which types of recurrences of the arrhythmias after the surgery did you detect? Also, could you comment on what was the reason for not doing the lesion between pulmonary veins and the mitral annulus? In which type of cardiac pathology was the selective procedure of the pulmonary veins unsuccessful? Overall the paper confirms the current opinion that cardiac patients with permanent AF should be considered for intraoperative surgical ablation, and, one has to congratulate the authors for their data, which may also serve as a valuable basis for a further evaluation of surgical concepts in this important and steady patient group. Response Author: Dr. Stephan Geidel, Cardiac Surgeon, AK St. Georg, Department of Cardiac Surgery, Lohmühlenstraße 5, 20099 Hamburg, Germany Date: 05-Apr-2003 01:41 Message: We thank Dr. Hornero for his interest in our data and his precise comment. 1. We agree with the statement that the incidence of permanent AF is in all probability very different among countries. It is interesting for us to learn that a really high incidence of permanent AF is observed in Spain in adult patients scheduled for cardiac surgery, particularly among multiple-valve cases with severe mitral valve (MV) disease. The difference to our data can possibly be explained by a different mixture of pathologies of the heart valve cases. Another hypothesis might be that these patients normally come for surgery at different stages of valve disease. In MV surgery particularly in the literature of MV repair AF has been described as a relevant prognostic factor for post-operative outcome, which has lead to the idea that patients with MV insufficiency should be operated generally earlier, that means before progressive decrease of LV function and NYHA class III/IV symptoms and before AF occurs. The described differences therefore might be an expression of variant proceedings and infrastructures of our countries, possibly patients are scheduled for heart valve surgery earlier here. In 2000 Spain had 628 open heart procedures on 1 Mio inhabitants, Germany 1.239, which supports this hypothesis; particularly in Hamburg it was 2.045 procedures on 1 Mio inhabitants in 2001. However, the whole subject remains speculative, a precise analysis of the data would be necessary to come to real conclusions. 2. One more comment to our lesion pattern: when we started with RF ablation in February 2001 there was already an international discussion about the subject how complete (compared to the Maze procedure) an ablation pattern has to be. Our primary intention was to offer a proceeding with a minimal time consumption and risk in a group of old patients with a lot of additional diseases. That is why we omitted lesions other groups estimated to be of importance. We were not convinced that a lesion between the PVs and the MV annulus would be absolutely necessary for a successful ablation procedure in most cases. We believe now, that in patients with small LA diameters the success rates of the described procedure are good enough to omit any further lesion; in patients with large LA and severe diseased atrial myocardium any additional lesions should be calculated on the basis of electrophysiological and morphological findings. For us and our further proceeding the described pattern has one more advantage: it can be performed easily with a bipolar RF energy device we started to use for treatment of permanent AF concomitant to CABG surgery since March 2003. 3. The types of arrhythmias we saw after surgery were recurrences of continuous atrial fibrillation, no single case of intermittent AF but 2 cases of atrial flutter finally culminating in continous AF. Early recurrence of AF after ablation surgery may be due to the fact that the refractory period of the atrium is significantly shortened. However, we continued to perform early DC cardioversion in these cases to generate sinus rhythm as early as possible knowing that other groups began to wait for spontaneous conversion during the first 3-6 months after surgery. 4. Therapy refractory recurrences of permanent AF were unfortunately seen without significant relation to specific cardiac pathologies. However, as mentioned before, in patients with large LA the lowest success rates were observed. doi:10.1016/S1569-9293(03)00009-4
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Abstract
1. Introduction
