Interact CardioVasc Thorac Surg 2007;6:695-698. doi:10.1510/icvts.2006.147942
© 2007 European Association of Cardio-Thoracic Surgery
Work in progress report - Arrhythmia |
Thoracoscopic microwave ablation of atrial fibrillation
Juhani Koistinenb,*,
Mika Valtonenc,
Jukka Savolaa and
Juhani Airaksinenb
a Department of Surgery, Turku University, Finland
b Department of Medicine, Turku University Central Hospital, FIN-20520 Turku, Finland
c Department of Anaesthesiology, Turku University, Finland
Received 28 November 2006;
received in revised form 3 July 2007;
accepted 4 July 2007
*Corresponding author. Tel.: +358-2-313 0000; fax: +358-2-3132061.
E-mail address: juhani.koistinen{at}tyks.fi (J. Koistinen).
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Abstract
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The aim of the study was to assess the safety and efficacy of thoracoscopic microwave ablation in treating atrial fibrillation (AF). AF predisposes to embolic complications and may cause heart failure. The treatment of AF is still challenging in spite of the promising results of endocardial radiofrequency approach. The present study is a follow-up study of 22 patients (mean age 45 years, range 21–59) with disabling paroxysmal (n=10) or persistent (n=12) AF who underwent a thoracoscopic microwave isolation of pulmonary veins. The patients had a lone AF. All the patients had suffered from severely disabling AF for >1 year (range 1–16 years) without any response to antiarrhythmic medication. The patients have been followed-up on an average of 11 months (range 3–22 months). During the follow-up, 13 (60%) patients have become asymptomatic without any documentation of AF since at least two months, six (27%) patients with anti-arrhythmic medication have clinically improved. Because of major intrathoracic bleeding and because of liver damage the thoracoscopy wound had to be expanded to open thoracotomy in two patients. Thoracoscopic AF microwave ablation seems to be a promising alternative to endocardial ablation in the treatment of highly symptomatic paroxysmal and persistent AF.
Key Words: Atrial fibrillation; Microwave ablation; Pulmonary vein isolation
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1. Introduction
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Atrial fibrillation (AF) is the most common arrhythmia leading to hospitalization. It predisposes to embolic complications and may lead to heart failure with poor rate control [1]. Because of the aging in the western societies the prevalence of AF is increasing [2, 3]. The incidence of AF is not only depending on age but also on the function of the left ventricle or on the concomitant structural heart diseases [4, 5]. Several approaches to treat AF have been introduced. Medical therapy in controlling AF has been a disappointment with increased mortality in several patient groups [6–9].
Non-pharmacologic interventions have been promising. The endocardial ablation of AF has emerged as an option for treating AF. The finding of focal AF with the focus in the pulmonary veins, introduced by Haissaguerre et al. [10], led to the procedure of focal ablation in the veins. Because of the risk of pulmonary vein stenosis the isolation of pulmonary veins instead of focal ablation was then introduced. Later, a combination of pulmonary vein isolation and AF substrate modification has yielded promising results [11]. Endocardial radiofrequency ablation is effective in several patients with paroxysmal AF but it needs to be repeated often. Any studies comparing the approaches with the medical ones have not been reported. Possibly, the used radiofrequency energy is not optimal. Microwave energy may have some superior characteristics in comparison to radiofrequency energy. The surgical option has been evolving during the years in spite of the promising outcome of endocardial ablation procedures. The maze [12] procedure is well-known but the problem has been the open-heart surgery leading to expansion of complications. In recent years the thoracoscopic alternative has emerged as a new option of performing the isolation of pulmonary veins accompanied by the substrate modification with epicardial microwave energy. In the present study, we describe our first experience on thoracoscopic microwave isolation of pulmonary veins in a highly symptomatic patient population suffering from paroxysmal AF.
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2. Patients and methdos
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The study population consisted of the 22 patients (mean age 45 years, range 21–59 years, 3 female and 19 male) (Table 1). Thoracoscopic microwave isolation of pulmonary veins was offered as a treatment option for highly symptomatic patients with paroxysmal or persistent AF. The AF was lone AF which was not related to other structural heart diseases. The patients with paroxysmal AF had recurrent episodes of AF with spontaneous cardioversion whereas the patients with persistent AF had undergone cardioversions (medical or electrical). The possible underlying heart disease was excluded by echocardiography. Seventeen patients had enlargement of the left atrium (more than 35 mm) which was interpreted to be caused by recurring AF episodes. Coronary artery disease was excluded by clinical means, but not systematically by a coronary angiogram. All the patients were in sinus rhythm when coming to ablation. All the patients had a failure of at least two different antiarrhythmic drugs, and had suffered from highly symptomatic attacks of AF for more than one year. Two of the patients had undergone dual chamber pacemaker implantation because of sinus node dysfunction and susceptibility to AF. Transvenous catheter ablation was not attempted in any of the patients before the operation. The patients were highly symptomatic and they were offered to undergo the thoracoscopic procedure without any denials in the first 22 patients treated in our hospital. The exclusion criteria were permanent AF, structural heart disease, significant left ventricular dysfunction and thyreotoxicosis. The patients were referred by a cardiologist to the operation.
2.1. Surgical and anaesthesiological techniques
After normal anaesthesia induction by sufentanyl, 50 µg and propofol 2.0–2.5 mg/kg, followed by rocuronium 0.08 mg/kg to facilitate tracheal intubation, one lung ventilation was used in all patients (double lumen tube Mallinckrodt® 35–37 left). During one lung ventilation, 100% oxygen and positive end expiratory pressure (5–8 mbar) were used to ensure oxygenation. Amiodarone (150 mg intravenously) was given after induction if the patient had AF prior to the induction or if the patient had several AF episodes during the operative manipulation. Surgical technique has been described by Saltman et al. [13]. We modified the patient's position laying on his back using a pillow between both scapulas and both arms alongside of the body. Three ports were inserted (4th, 5th, 6th) on the right and left intercostal spaces; the lowest one for the camera (10 mmØ) in the midaxillary line and two more anterior (5 mmØ) for working instruments. After right lung deflation the right pericardium was widely opened from the superior vena cava to the phrenicopericardial pouch. Two small nasogastric tubes were passed through tunnels between the superior vena cava and upper pulmonary as well as lower pulmonary veins and the inferior vena cava to the left pericardial space. Then, a short opening of the left pericardium and picking these two tubes outside of thorax and connected together. With these guiding wires, finally a Flex 10® (Guidant) microwave antenna is positioned by a gentle manner encircling all of the four pulmonary veins and oriented towards the atrial surface (the black line visualized) and behind the left atrial appendix. The Flex 10 antenna was activated in 2 cm in a continuing row at 65 W and 90 s to create an ablation line completely surrounding the pulmonary veins. After visual confirmation the antenna was pulled out. After the ablation, the left atrial appendix was assessed visually by transoesophageal echocardiography (size and flow pattern by pulse wave Doppler). Stapling using endocutter (ETS 45® Ethicon) was performed if the left atrial appendage was visually deemed to be significantly enlarged. The stapling was also performed if the patient had suffered from a thromboembolic event. The thoracoscopic technique of microwave ablation and stapling of the left atrial appendage are shown in Video 1. The still image presents the positioning of microwave antenna encircling pulmonary veins. Right sided ablation lines were not performed in this cohort of the first 22 patients undergoing the pulmonary vein isolation in our hospital. No intraoperative or postoperative electrical stimulation was performed in order to confirm pulmonary vein isolation (Video 1).
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Video 1. Flex 10® (Guidant) microwave antenna is positioned by a gentle manner encircling all of the four pulmonary veins and oriented towards the atrial surface and behind the left atrial appendix. The cannulation of the pericardial space, the positioning of the microwave antennas to encircle the four pulmonary veins, the ablation of the veins and finally the stapling of the left atrial appendage are shown in the enclosed video presentation.
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2.2. Postoperative care and clinical follow-up
Until discharge, patients were monitored by telemetry and standard 12-lead ECG recordings. External cardioversion was encouraged in the early postoperative period. No strict antiarrhythmic regimen was administered postoperatively. The patients were anticoagulated. Amiodarone or flecainide in combination with a betablocking agent was administered to suppress the postoperative AF when needed. The patients were followed-up by clinical means, 12-lead ECG-recordings and Holter recordings. No routine echocardiographic follow-up was performed. The follow-up visits were scheduled for one month, three months, six months and one year postoperatively. Holter recording was performed at the six-month visit. The patients were told to contact the first-aid clinic when having arrhythmia postoperatively. Recurrent AF was cardioverted. The patient records have been checked in all participating patients.
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3. Results
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Pulmonary vein isolation could be performed in every patient with the thoracoscopic approach. The left atrial appendage was removed in six patients. The mean duration of the operation was 186 min (range 85–28 min) and the mean duration of the anaesthesia procedure was 301 min (range 205–435 min). The patients were discharged within one week after the operation. The majority of the patients had episodes of AF during the postoperative hospital stay. The 6-month follow-up period was completed for all patients and no patient was lost during the follow-up period. The mean follow-up period was 11 months with a range of 3–22 months. Adverse events and their relatedness to the procedure were collected and reviewed at the visits. Nineteen patients have clinically improved. Thirteen patients are asymptomatic without any documented AF episodes excluding the first postoperative month. Three out of these 13 patients are still on anti-arrhythmic medication. In these patients Holter recording did not reveal any asymptomatic AF episodes. In these 13 patients their living conditions have radically changed postoperatively. All these patients had preoperatively highly disabling episodes of AF and the symptom correlation with arrhythmic events was documented. These patients were hospitalised preoperatively several times, but not during the late postoperative follow-up. Six patients on antiarrhythmic medication are clinically improved. Four patients developed atrial flutter during the follow-up. Atrial flutter was not typical macro re-entrant flutter with clockwise or counterclockwise features. Three patients have not improved after the ablation. The follow-up data are presented in Table 1.
3.1. Complications
All the patients recovered postoperatively without any life-threatening complications.
No life-threatening complications were found during the postoperative hospital stay or during clinical follow-up to 22 months. The thoracoscopy wound had to be expanded to open thoracotomy in two patients because of major intrathoracic bleeding and because of liver damage. Bleeding was controlled in both cases by suturing the bleeding vessels and the ablation procedure was fulfilled. Two patients had a reversible diaphragmatic relaxation on the right side. No thromboembolic complications were observed during the hospital stay or during follow-up. No late complications ( 30 days after surgical intervention) could be observed in this patient population. Because of sick sinus syndrome dual chamber pacemaker was implanted in one patient with clinical improvement of AF after the thoracoscopic ablation.
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4. Discussion
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The endocardial tranvenous AF ablations have yielded promising results. The problem is that it has to be repeated often, which prolongs the duration of rehabilitation and may disable the patient for several months. The surgical approach has been evolving during the last years. A break-through in the surgical field was the introduction of thoracoscopic technique in performing epicardial ablation lines. The procedure can be performed with beating heart avoiding open-heart surgery and thus reducing significantly the risk of complications. The previous surgical reports on AF treatment have dealt with patients suffering from far-advanced AF and predominantly chronic AF. The rationale of maze procedure differs from the present one. The maze procedure forms corridors for activation to spread and can be speculated to be somehow artificial. The present technique is aimed to focus on triggering of AF and possibly leads to the eradication of the triggering factor. An epicardic substrate modification can be combined to the isolation of the pulmonary veins. In the present study, we demonstrate the results concerning paroxysmal and persistent AF. In these patients the remodeling of the atrial tissue may not be as severe as in the patients suffering from chronic AF. The preliminary results seem to be promising. They also confirm the safety of this technique. The efficacy of an epicardial microwave ablation has been controversial because of uncertainty of transmural lesion. The epicardial approach leads, despite the myocardial lesion, also to modification of cardiac innervation which has been suggested to be beneficial. The present results seem to be comparable with the ones achieved by using the endocardial technique at non-pioneering centres. The obvious cure of the susceptibility to AF is reported to be 55–70% after follow-up of six months in these reports [14].
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Acknowledgements
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The contribution of Dr Timo Savunen, Dr Vesa Vilkki and Dr Kari Kuttila in participation in the present study is acknowledged.
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Abstract
1. Introduction