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© 2002 European Association of Cardio-Thoracic Surgery
Biatrial radiofrequency ablation for atrial fibrillation: epicardial and endocardial surgical approachCardiac Surgery Department of the University General Hospital, Valencia, Spain
* Corresponding author. Tel.: +34-96-386-2900 ext. 52396; fax: +34-96-386-2982 Received April 25, 2002; received in revised form August 12, 2002; accepted August 23, 2002
Radiofrequency energy applied by means of surgical probes permits the ablation of atrial fibrillation (AF). This study presents our initial experience on 55 consecutive cardiac patients with permanent AF with radiofrequency ablation through biatrial epicardial and endocardial surgical approach. At discharge, 8.1% of the patients had persistent AF-atrial flutter. Hospital incidence of arrhythmias were, 9% of paroxysmal atrial fibrillation, 10.9% of atrial flutter, and 34.5% of persistent atrial fibrillation. After a mean follow-up of 7 months, 83.6% patients have recovered sinus rhythm, and echocardiographic biatrial contraction was re-established in 73%. Biatrial radiofrequency ablation applied from the endocardium and the epicardium has achieved satisfactory results, without increasing the surgical risk.
Key Words: Atrial fibrillation; Surgery; Radiofrequency
Atrial fibrillation (AF) is the most frequent preoperative cardiac arrhythmia amongst cardiac surgery patients. The ‘cut and sew’ maze surgical procedure is the gold-standard AF treatment, with a sinus rhythm cardioversion superior to 90% [1]. However, due to its technical complexity it has been performed on a limited number of patients. Intraoperative radiofrequency (RF) ablation applied by means of electroprobes has proven able to reproduce the maze surgical atriotomies in a fast, safe and effective way [2–4]. A variety of radiofrequency surgical protocols have been reported in the literature. This study shows our initial experience with RF ablation applied from the endocardium and the epicardium compartmentalizing both atriums in a group of cardiac patients with permanent AF.
From June 2000 and December 2001, we performed biatrial radiofrequency ablation on 55 cardiac patients with permanent AF (>3 months). Table 1, shows the main clinical data and surgical cardiac procedures. The mean time of AF duration was 5.6±4.2 years (range 3 months and 16 years).
Echocardiogram examination (ECO) were performed for sizing atrial dimensions and assessment the atrial contractility. Atrial volumes was calculated using ellipsoid formula. It was considered effective restoration of the atrial transport function when transvalvular A wave was >25 cm/s. The early filling/atrial filling wave (E/A) ratio were also calculated. Results of atrial contraction function were expressed in terms of Santa Cruz Score [5]. The intraoperative RF was applied by means of a surgical malleable probe (ThermaLine®, EP Technologies), with seven 10 mm long coil-type electrodes with 3 mm interelectrode spacing and two indifferent electrodes placed on the patient's back. The ablation settings were 100 W for 120 s, with a maximum set temperature of 85°C. Same protocol was used with the endocardial and epicardial ablations. In the surgical field, in addition to the temperature control during the ablation, the lesion formation was visually evaluated by the surgeon. When the ablation was macroscopically discontinuous at one point, it was repeated until a uniform white coagulation line was achieved. To prevent possible RF complications several measures were taken in the surgical field: the echocardiographic probe was removed from the esophagus during the ablation time; RF was applied before the metallic prosthetic material was implanted; during epicardial ablations we protected the pericardium and nearby structures, such as the phrenic nerve, with surgical gauze; during the endocardial ablation we placed a rubber leaflet on the posterior side of the heart in order to avoid transmural retrocardiac burns; all endocardial lesions with post-ablation charring were cleaned with surgical gauze; continuous cool blood retrograde perfusion in the ablation points near the circumflex artery; and we avoided lesions near (<1 cm) the pulmonary vein ostiums. 2.1. Operative technique We performed a biatrial radiofrequency approach (Fig. 1). Ablations were performed in the right atrium (RA) from the epicardium before starting cardiopulmonary bypass, and in the left atrium (LA) from the endocardium. In cases with tricuspid valve disease the ablation line in the RA was replace by an incision. No cryoablation was performed in the mitral and tricuspid valve annulus, nor did the atrial appendages excised. In all patients, the LA was approached through a standard left atriotomy made just posterior to the interatrial groove, by means of ample dissection up to near the fossa ovalis. Left appendage was internally sutured when thrombus was found.
2.2. Postoperative protocol DDD stimulation was done during the first 48 h. Amiodarone treatment (200 mg/day) was initiated intraoperatively, and stopped on the 3rd month in patients who maintained sinus rhythm. All patients were treated with spirolactone 50–100 mg daily during their hospital stay. The anticoagulation was suspended at the 3rd month in patients without cardiac mechanical prosthesis and with effective echocardiographic atrial contraction. The postoperative follow up controls took place at hospital discharge, at the 3rd, 6th, and 12th month, by means of electrocardiogram and ECO. After discharge, new AF-atrial flutter episodes during the follow up period were treated with external cardioversion. Based in the number recurrences, our protocol considered ineffective the surgical ablation procedure when the patient discharged need more than three cardioversions for recurrences of AF-atrial flutter during the first 3 months after surgery. After this time, new episodes no were cardioverted and AF was considered to be permanent. 2.3. Statistic and data presentation Continuous variables is presented as mean±one standard deviation. Comparisons of patients in AF or sinus rhythm after operation were made using Mann–Whitney test for continuous variables, and discrete variables using the Fisher exact test. Results were considered significant at 95% confidence interval, P value less than 0.05.
The surgical procedures associated to the AF ablation were various as displayed on Table 1. The postoperative complications were: one patient with mitral valve replacement presented a transient ischemic attack 3 days after surgery; two patients presented unusually postoperative fluid retention that need increase the diuretic treatment; three reoperations for bleeding. The mean length of hospitalization was 11.5 days (range 6–65 days). The hospital mortality was one patient (1.8%) with history of chronic renal failure that presented a sudden death 22 days after the surgery. The mean follow up interval was 7 months (range 1–16), and during this time two patients died, the partial atrioventricular canal defect presented a sudden death with unknown causes, and a mitral valve replacement for cerebral haemorrhage probably due to acenocumarol treatment. During epicardial RF applications no atrial perforation was produced, even though in some areas the wall thickness was minimal, under 1 mm. The epicardial fatty areas were visually frequent points of ineffective ablation. The applications evolution was visually controlled and in 16% of the lesions there was a macroscopic healthy tissue gap, that is, a lack of white tissue discoloration typical of the RF ablation (Fig. 2). The RA lesions were performed on all patients without CPB. RF applications in the RA did not compromise in any case the patient's hemodynamic state, nor did they produce any arrhythmic alteration that mandated the abortion of the procedure. No patient recovered the sinus rhythm with just the application in the RA.
After CPB six patients (10.9%) presented intraoperatively AF-atrial flutter recurrence. During the rest of the hospital stay 41 patients (74.5%) presented supraventricular arrhythmias: 17 patients (30.9%) junctional rhythm for over 48 h, 13 patients (23.6%) transient first-degree atrioventricular block, one transient third-degree atrioventricular block (patient with partial atrioventricular canal defect), six patients (10.9%) atrial flutter, five patients (9%) paroxysmal episodes of AF, and 19 patients (34.5%) persistent AF recurrence. At hospital discharge, 44 patients (81.4%) recovered sinus rhythm, one patient maintained an atrial flutter, and nine (16.6%) persistent AF. During the first 3 months, one patient with atrial flutter and three with AF spontaneously recovered sinus rhythm; six patients (13.2%) presented recurrence of AF and one atrial flutter. At late follow up, 46 patients (83.6%) have recovered sinus rhythm, amongst them one with sinus dysfunction without any pacemaker indication on the Holter study; one with chronic atrial flutter, one with episodes of paroxysmal atrial tachycardia; four patients (7.7%) in permanent AF. There were significant correlation between postoperative echocardiographic LA volume and preoperative duration of AF with late AF recurrence (  ; Table 2).
Amongst the 44 patients in sinus rhythm, ECO atrial function checked at hospital discharge confirmed biatrial contraction in 20 patients (45.4%), right uniatrial contraction in seven patients (15.9%), and atonia auricular in 17 patients (38.6%). At the end of the follow up, there was a recovery of the atrial function, with LA contraction in 38 patients (73%), RA contraction in 44 patients (84.6%), and three patients (5.7%) with atonia auricular. In nine patients the left atrial kick was low with small A-wave (<25 cm/s). The E/A ratio was 3.31±1.63 at the end of the follow up. The Santa Cruz Score was: six patients scored 0 (10.9%), three patients scored 1, six patients scored 2, and 38 patients scored 4 (69%).
RF ablation is used to create linear non-conductive barriers to prevent the intra-atrial reentry responsible for AF [2,4,6,7]. One of the major limitations of intraoperative RF ablation for treatment of AF is the heterogeneity and relatively shallow of the lesions. Discontinuous and/or non-transmural lesions are responsible for the origin of new postoperative re-entrant arrhythmias and are probably the most important factor in the result of the RF intraoperative ablation of AF [8]. In our experience, hospitalary prevalence of new paroxysmal or persistent AF-atrial flutter was 54.5%. Macroscopically we observed 16% of lesions with gaps, especially at the points matching the central location of each electrode, atrial regions with difficult approach, such as the ostiums of left pulmonary veins, and epicardial fatty areas and epicardial areas of fibrosis in reoperations. Although a discontinuous line with gaps under 2–3 mm could be effective if it is transmural [9], for our daily practice, we believe that visual inspection of the lesion is necessary in order to guarantee a macroscopic gap-free lesion. In animal studies the lesion is marked by tissue discoloration that corresponds to 60°C isothermal line, and it may be used as histologic marker of good ablation [10]. Probably, in this surgery will be necessary tested intraoperatively the conduction through the lesion and verified the procedure. Various groups have not found differences between maze III and LA side maze when applied to the treatment of AF with mitral valve disease, although the number of recurrences during the follow up was superior in the simple procedure [11,12]. Sie et al., associated RF ablation in 122 patients with AF by means of maze III reestablishing sinus rhythm in 98% at 1 year, and 78.5% at 3 years after surgery [2]. Others groups perform more simple AF procedures for mitral valve disease, such as the selective isolation of pulmonary vein, epicardial and/or endocardial LA RF-maze with results of 50–85% success [4,13]. Kosakai et al. [11] have reported in AF with non-mitral valve disease better results with maze-III procedure than with partial left maze. In our experience we have obtained initial AF treatment effectiveness of 83.6% with biatrial RF. The epicardial ablation has been described in animal models, and later applied to humans by means of pulmonary veins isolation for the treatment of secondary AF to mitral valve disease [3,4]. There is little experience in the right atrium surgical epicardial ablation [7]. In our cases the epicardial ablation was simple, fast and safe (no perforations), even in those cases where it was applied in thin walled atriums, but the fatty areas and epicardial fibrosis in reoperations were difficult points for ablation. Atrial contraction recovery is one of the objectives of AF surgery. The atriotomies cut-and-sew and a linear radiofrequency lesions have a deleterious effect in atrial contraction [14]. Mitchell et al. showed that in a dog model a maze pattern of linear lesions to cure AF may cover 20–22% of the left endocardial surface [15]. In our series we detected an early biatrial contraction recovery in 20 patients (45.4%) followed by an improvement in the 1st months, probably due to an atrial electro-anatomic remodelling process, reaching presence of atrial contractions at 6 months in 73% of sinus rhythm patients. Although the transmitral A-wave can be influenced by a number of factors, in our experience only 53% patients in sinus rhythm presented effective left atrial transport function (A-wave >25 cm/s). Our study has several limitations. The small number of patients in the study, so we can only considered this study as an observational study. We did not perform histological studies to confirm the surgical macroscopic observations during the ablation. The amiodarone treatment for the first 6 months is another limitation of this study, especially for the short follow up time in a type of surgery that requires longer-term results. Our initial experience with RF ablation applied from the endocardium and the epicardium, compartmentalizing both atriums, has achieved satisfactory results by not increasing the surgical risk and obtaining an initial AF treatment effectiveness of 83.6%. Only 53% of patients in sinus rhythm presented normal echocardiographic LA transport function (no small A-wave). The in-hospital prevalence of postoperative arrhythmias was 74.5%, with 10.9% of atrial flutter and 34.5% of AF recurrence. The right atrium epicardial ablation can be performed on all patients without the need for extracorporeal circulation.
ICVTS on-line discussion Author: Stephen Large, Consultant Surgeon, Papworth Hospital, Cardiac Surgery, Papworth Hospital, Papworth Everard, Cambridgeshire CB3 8HX, UK Date: 10-Sep-2002 04:37 Message: This is an interesting piece of work especially through its very laudable attempt to define the population of patients undergoing AF surgery who do badly. Like other radiofrequency techniques it appears that the success rate (despite per-operative amiodorone) is lower than with the cut and sew method. This paper would be the richer for a description of the time taken to construct the maze and in this way show the advantage over the probably more effective cut and sew approach. My final point is in the area of failure to regain sinus rhythm. With incomplete electrical barriers, which is probably the most common cause of failure of radiofrequency approaches, there is a state worse than mere failure to restore sinus rhythm. This is through the creation of intrusive and refractory atrial flutter. I wonder to what extent this group experienced this problem and how they subsequently dealt with it? Response Author: Dr. Fernando Hornero, Consultant Surgeon, Hospital General Universitario, Cardiac Surgery, Av Tres Cruces s/n, Valencia, 46014, Spain Date: 17-Sep-2002 19:00 Message: We would like to thank Dr. Large for his comments and interest shown in our paper. The ablation lines in the right atrium were performed in a mean time of 13+/–5 minutes and in 22+/–7 minutes in the left atrium. This paper didn't compare with the maze procedure, but we believe that radiofrequency is shorter than the cut and sew procedure and it has lower postoperative morbidity. However, carefully controlled studies are lacking. I agree with you, that post-radiofrequency atrial flutter during the postoperative course is a state worse than mere failure to restore sinus rhythm. In our experience, we have 10.9% of atrial flutters. Atrial flutter tends to be stable, not reverting to sinus rhythm or degenerating into atrial fibrillation. During the hospital course the atrial rate during atrial flutter was usually 80 to 120 beats/min with antiarrhythmic drugs. Rapid atrial pacing with the auricular wires was always ineffective and synchronous direct-current cardioversion was commonly the initial treatment of choice for atrial flutter. Based on our short experience, we never discharge patients in atrial flutter (by epicardial record). One patient with mitral valve replacement showed at first postoperative control (1% postoperative month) rapid deterioration of the ejection fraction associated with rapid atrial flutter (110 beats/min). Probably it was a tachy-myocardiopathy, because ventricular function was recuperated after external cardioversion during the follow-up. Although only a few atrial flutters present this complication we believe that it is serious enough to warrant a strict follow-up of these patients by means of electrocardiogram and ECO. However, in our experience the atrial fibrillation can be left untreated with antiarrhythmic drugs and discharge of the patient, depending on the clinical circumstances, and programming external cardioversion in the first postoperative month. Although, at the moment, the incidence of new episodes of atrial flutter during the follow-up is low, one interesting point in this surgery is if the risk of atrial flutter is maintained for a long time. If the answer is affirmative, probably in this surgery it would be necessary to test intraoperatively the conduction through the lesion and verify the procedure. PII: S1569929302000336
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Abstract
1. Introduction
) in a radiofrequency ablation line after time setting; in this atrial point, the ablation was repeated. Inter-cava ablation line, with post-ablation charring points (
).
