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Ann Thorac Surg 2005;79:1505-1511
© 2005 The Society of Thoracic Surgeons
a Service de Chirurgie Cardiovasculaire, Hôpital Cardiologique, CHRU de Lille, Lille, France
b Service d'Explorations Fonctionnelles Cardiovasculaires, Hôpital Cardiologique, CHRU de Lille, Lille, France
Accepted for publication November 17, 2004.
* Address reprint requests to Dr Fayad, Hôpital Cardiologique, CHRU, Boulevard du Pr. J. Leclercq, 59037 Lille Cedex, France (E-mail: g-fayad{at}chru-lille.fr).
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Abstract |
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METHODS: In a prospective study, 70 patients (64 ± 10 years) with mitral valve disease and atrial fibrillation underwent mitral surgery and left atrial endocardial radiofrequency ablation. Evaluation was achieved before surgery, at 7 days, 5 months, and 22 months after surgery. Maximal right and left atrial areas, left atrial diameter, and volume were measured. Atrial filling fraction (ventricular filling related to atrial contraction to total ventricular filling ratio) was used as an index of atrial contraction.
RESULTS: At the end of follow-up (22 ± 10 months) most patients (91%) were in sinus rhythm. Actuarial freedom from atrial fibrillation recurrence was 62.5% after 2 years. Atrial size decreased, with a significant improvement in right (36 ± 15 vs 10 ± 20% preoperatively, p < 0.0001) and left (25 ± 12 vs 7 ± 14%, p < 0.0001) atrial filling fraction. Despite similar preoperative atrial size, at the end of follow-up atrial fibrillation recurrence was associated with a higher left atrial volume than in patients free of recurrence (41 ± 14 vs 32 ± 9 mL/m2, p = 0.004). Independent predictors of atrial fibrillation recurrence were previous mitral procedure (p = 0.029), left ventricular ejection fraction (p = 0.033), and mitral rheumatic lesion (p = 0.034).
CONCLUSIONS: Left atrial radiofrequency ablation for atrial fibrillation during mitral surgery is an effective procedure restoring sinus rhythm. Right and left atrial size was significantly reduced, with a recovery in atrial contraction.
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Introduction |
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Patients and Methods |
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Patients evaluation included questioning, clinical examination, electrocardiogram recording, and complete Doppler-echocardiographic examination. It was performed before surgery, 7 days, 3 to 6 months, and 12 to 36 months after surgery.
Surgery
Operations were performed by two experienced surgeons. Cardiopulmonary bypass was conducted through median sternotomy, using moderate hypothermia and repeated antegrade cold blood cardioplegia. Surgery consisted of MV replacement or repair associated with endocardial RFA in the LA. Endocardial RFA was achieved in the LA before valve surgery using a seven tip radiofrequency catheter (Thermaline, EP Technologies, Boston Scientific Corp, San Jose, CA); electrodes were close enough to each other to provide continuous linear lesions. The technique consisted of 120 seconds application time, 75°C target temperature, and 150 W output. Isolation of pulmonary veins was obtained with two circular ablation lines and a connecting line between both islands of pulmonary veins. An ablation line was then performed from the left pulmonary veins to the posterior mitral annulus as previously described [19]. In our study, left atrium appendage was not excluded.
Cardiac Rhythm Assessment
Patients were monitored by telemetry until the fourth postoperative day. A daily electrocardiogram was recorded during the following in-hospital stay. Later on, the cardiac rhythm was assessed during each evaluation; a 24-hour electrocardiogram recording was achieved after 6 months and repeated at least once during the follow-up in patients without previous AF recurrence. Any atrial arrhythmia occurring after the third postoperative month was considered as a recurrence, including short runs of atrial arrhythmia on 24-hour electrocardiogram recording [11]. Early postoperative atrial arrhythmias were treated with sotalol or amiodarone and cardioversion when necessary. In this last case, patients were discharged under antiarrhythmic drugs for at least three months to allow reverse electrical remodeling. All patients were discharged under effective oral anticoagulation. Referring cardiologists were allowed to stop antiarrhythmic drugs after the third month in patients with stable SR and effective atrial contraction. They were advised not to discontinue anticoagulation until they got cardiac rhythm under control.
Doppler and Echocardiography
Echocardiography was performed by two experienced investigators using a commercially available device (Sonos 5500, Philips, Andover, MA; or HDI-5000, ATL, Philips, Bothell, WA). All values were obtained from the mean of 3 to 5 beats with a particular care for patients in AF. Left atrial diameter was measured in the parasternal long-axis view using M-mode echocardiography [20]. Left atrial volume (LAV) was calculated as an ellipse using the formula: LAV = 
/6 (LAD1. LAD2. LAD3), where LAD1 is LAD in M-mode, LAD2 and LAD3 are, respectively, the short-axis and long-axis LAD measurements in the apical four-chamber view at ventricular end-systole [21, 22]. Left atrial volume was indexed to body surface area. Left atrial area (LAA), right atrial area, LV volumes, and EF were measured from the apical chamber views. The mitral and tricuspid flow profiles were recorded in the apical view; time-velocity integrals, E-waves, and A-waves measurements were performed. Atrial contribution to ventricular filling was assessed by measuring atrial filling fraction (AFF) as the ratio of the tricuspid or mitral flow time-velocity integral of the A wave to total ventricular filling [16].
Follow-Up
Data were collected prospectively during the in-hospital stay and during the evaluation sessions. Follow-up was achieved by phone contacts with patients, family physicians, and cardiologists. Mean follow-up time was 22 ± 10 months in both groups; no patient was lost in follow-up.
Statistical Analysis
Results are expressed as mean ± standard deviation. Comparisons between groups were performed with 
2 tests or with paired or unpaired Student t tests. A repeated-measures analysis of variance was used to evaluate changes in echocardiographic variables, with a two-way analysis for comparison between groups. The interaction between time and groups was tested. Event-free actuarial survival rates were calculated by the actuarial method. The log-rank test was used to compare actuarial events. A multivariate Cox model analysis was performed to determine independent predictive factors for AF recurrence. A p value less than or equal to 0.05 was considered statistically significant.
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Results |
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Cardiac Rhythm
In most patients, an early recurrence was recorded during the in-hospital stay; however, 46 patients (68%) were in SR at discharge. The percentage of patients in SR on the day of examination at each follow-up time point is depicted in Figure 1. Twenty-four patients (35%) experienced at least one late atrial arrhythmia recurrence, 15 patients (22%) had several recurrences, including 6 patients (9%) in permanent AF at the end of follow-up. Patients with permanent AF were in the preoperative permanent group. Atrial flutter, treated with percutaneous RFA, occurred in 2 patients; both presented subsequent AF recurrence. Freedom from AF recurrence, including short runs of atrial arrhythmias, was 70.4% at 12 months and 62.5% at 24 months after surgery (Fig 2). Univariate analysis shows that rheumatic valvular lesion, previous MV procedure, LVEF, and associated procedures were predictive factors for AF recurrence. In multivariate analysis, previous MV procedure (p = 0.029), LVEF (p = 0.033), and MV rheumatic lesion (p = 0.034) were independent predictive factors for AF recurrence. On the contrary, left atrial size and type of surgery were not predictive factors for AF recurrence.
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Doppler and Two-Dimensional Echocardiography
Echocardiography was performed in all but one patient during follow-up. Compared with the preoperative values, there was a significant decrease in LAD, LAA, LAV, and RAA (Table 3). Changes were similar in both preoperative groups (Fig 3). Effective atrial contraction was demonstrated in all patients in SR during follow-up. Right and left AFF increased significantly during follow-up. Right AFF was higher at each time point. (Table 3, Fig 4).
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Using a two-way repeated-measures analysis of variance, an interaction between time and AF recurrence on LAD (p = 0.006) or LAA (p = 0.03) was found. At the end of follow-up and only at this time, there was a significant difference between the stable SR group and the AF recurrence group (LAD: 43 ± 6 vs 46 ± 7 mm, p = 0.02; LAA: 24 ± 5 vs 27 ± 6 mm, p = 0.03). There were no differences in LAV indexed to body surface area (LVA/BSA), between patients with stable SR and those with AF recurrence, before surgery (61 ± 21 vs 60 ± 19 mL/m2, p = 0.87), or 7 days and 5 months after surgery. However, stable SR was associated with a significantly lower LAV/BSA at the end of follow-up (32 ± 9 vs 41 ± 14 mL/m2, p = 0.004).
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Comment |
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Cardiac Rhythm
Due to the loss of atrial contraction, AF decreases ventricular filling and cardiac output and may worsen heart failure, particularly in patients with cardiomyopathy or valve disease. Atrial fibrillation is thus often badly tolerated and is also an important risk factor for thromboembolism. In patients with MV disease, AF incidence is high [1, 2] and is associated with an impaired survival under medical treatment or after surgery [2, 3]. The atrial fibrillation follow-up investigation of rhythm management (AFFIRM) and the rate control versus electrical cardioversion for persistent atrial fibrillation (RACE) medical studies have recently demonstrated that medical rhythm control offers no survival advantages over rate control, leading to the idea that rhythm control might be abandoned if not fully effective [23, 24]. Because the use of antiarrhythmic drugs is not quite satisfying, nonpharmacologic approaches to control rhythm have been developed. Surgical treatment of AF appears to be an interesting option in patients requiring MV surgery with direct access to the LA. Although the Cox-maze procedure is effective for curing AF [4, 6], the procedure duration and the increased morbidity rate have prevented widespread acceptance of this technique. Moreover, even when SR is restored after the Cox-maze procedure, recovery of atrial function remains low, below 80% [4, 6, 16]. Simplified techniques replacing surgical incisions with left atrial cryoablation or radiofrequency ablation in combination with MV surgery have been successfully developed, but little is known about the effect of SR restoration on atrial size and function in this setting.
Atrial fibrillation recurrence is frequent in the early postoperative period, due to the decrease in the refractory period related to catecholamines discharge; this hyperadrenergic state usually resolves within three months after surgery [25]. Consequently, AF recurrences were considered for analysis after the third postoperative month [11]. However, most patients were in SR at discharge in our study. At the end of follow-up (22 ± 9 months), the percentage of patients in SR on the day of examination was about 90% (62 from 68 survivors) confirming favorable results of the surgical technique we used [5, 8, 11]. Moreover, a significant decrease in medical treatment was possible. Freedom from any atrial arrhythmia recurrence, including short runs recorded on 24-hour electrocardiogram (ECG), was 70.4% after 12 months and 62.5% after 24 months, which is similar to previously reported results [11].
Atrial Size and Function
Our results showed a progressive and sustained decrease in atrial size after surgery (Table 3, Fig 3). Although the main driver of early postoperative decrease in atrial size can be a conjunction of direct surgical effect and decrease in atrial pressure, subsequent atrial size improvement is probably related, at least in part, to SR restoration. Indeed, recent studies using intraoperative RFA have also demonstrated a decrease in LA size after SR restoration [17, 26]. Moreover, as in our study, LA size was significantly lower at the end of follow-up in the stable SR group compared to the AF recurrence group in a previous study [17]. In our study, the RFA procedure was limited to the LA posterior wall leading to the recovery of atrial contraction in 100% of patients in SR. This result compares favorably with previous studies reporting an atrial contraction in 90% to 100% of patients in SR [8, 12, 17], which appears higher than after the maze procedure [4, 6, 16]. Moreover, after exclusion of patients with permanent AF, there was only a nonsignificant trend toward a decrease in the left AFF in patients with paroxysmal AF recurrence. Thus, RFA did not appear to have a deleterious effect on atrial function in our experience and allowed an early and sustained restoration of the right as well as the left atrial contraction (right AFF: 36 ± 15%, and left AFF: 25 ± 12%). Comparison of left and right ventricular filling patterns demonstrated that right AFF was higher at each time point compared with the left AFF. This difference was probably related to MV repair or replacement leading to a high level of transmitral driving pressure at MV opening and to an increase in early LV filling. Left radiofrequency ablation might also participate, at least in part, to the relative low level of left AFF.
The strengths of our study include a prospective design with sequential echocardiographic assessment of atrial size and function before and after surgery. In addition, any atrial arrhythmia, even one short run recorded on 24-hour ECG, was considered as a recurrence. Since we are convinced that there is no perfect mean to detect atrial arrhythmia recurrence, one cannot exclude that some patients classified in the postoperative SR group experienced asymptomatic recurrence. Due to this inherent limitation, our results have to be considered with caution, as in any study concerning AF. The lack of a comparative group and of randomization is the main limitation of this study. The decision regarding the use of the RFA procedure was made by the cardiovascular surgeon on the basis of the preoperative data. Since it has been demonstrated that the RFA procedure is effective and safe to treat AF during MV surgery, a randomized control trial to assess the beneficial effect of this technique on atrial size and function would be difficult to develop.
In conclusion, the LA endocardial RFA procedure is safe and effective in MV surgery, leading to a permanent and stable SR in most patients (62.5%) after 2 years, independently of preoperative AF duration or LA size. Previous MV procedure, LVEF, and rheumatic MV lesions are predictive factors of AF recurrence. This procedure allowed an early recovery of left and right atrial mechanical function with a progressive decrease of both atrial sizes.
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
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= before; 
= 7 days; 
= 5 months; 
= 22 months.
= persistent AF. Data are depicted as mean ± standard error. There was a significant decrease in RAA (p = 0.014), LAD, LAA, and LAV (all p < 0.0001) in both preoperative groups. There were significant differences in atrial sizes between preoperative permanent and persistent groups (RAA, p = 0.035; LAD, p = 0.006; LAA, p = 0.029; LAV, p = 0.048) but changes in atrial sizes were similar in both groups (p not significant for interaction between time and groups). (LAA = left atrial area [top right]; LAD = left atrial diameter [bottom left]; LAV/BSA = left atrial volume indexed to body surface area [bottom right]; RAA = right atrial area [top left].)