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Ann Thorac Surg 2003;76:1711-1715
© 2003 The Society of Thoracic Surgeons
a Department of Cardiac Surgery, Heart Center, University of Leipzig, Leipzig, Germany
Accepted for publication May 1, 2003.
* Address reprint requests to Dr Doll, Heart Center, Clinic for Cardiac Surgery, University of Leipzig, Strümpellstrasse 39, 04289 Leipzig, Germany.
e-mail: dolln{at}medizin.uni-leipzig.de
Abstract
PURPOSE: Recently surgical treatment of atrial fibrillation has gained more popularity and presently is being performed in large numbers of patients. This report describes our early experience in treatment of patients with chronic or paroxysmal atrial fibrillation with a new tool for left atrial cryoablation.
DESCRIPTION: From July 2002 through January 2003, 28 patients underwent left atrial cryoablation with the Surgifrost CryoCath. Patients underwent cryotherapy as an isolated procedure (n = 1), in combination with mitral valve surgery (n = 13), or with other surgical procedures (n = 14). In all patients contiguous lesion lines to the orifices of the pulmonary veins connected to the mitral annulus and the atriotomy were created. Surgery was performed through a conventional sternotomy in 8 patients (29%) and a right lateral minithoracotomy using video-assistance in 20 patients (71%).
EVALUATION: Postoperatively sinus rhythm was restored in 27 patients (96%). At discharge 82% (23/28) of patients were in sinus rhythm and 18% (5/28) were in atrial fibrillation. Four patients (14%) required pacemaker implantation. There was no in-hospital mortality. At 6-months follow-up (19/28 patients) all were alive and 74% were in stable sinus rhythm, New York Heart Association functional class was 1.2 ± 0.4.
CONCLUSIONS: As indicated by our small and early patient cohort left atrial cryoablation with the Surgifrost argon cryocatheter is effective for the treatment of atrial fibrillation. This new device is technically easy to handle, it can be applied through a median sternotomy or lateral minithoracotomy. Long-term follow-up is necessary to evaluate further rhythm outcome.
The most prevalent sustained cardiac arrhythmia is atrial fibrillation (AF) [1]. Although 1% of the individuals in their fifties are affected by AF, on average 10% to 12% of the octogenarians are suffering from this arrhythmia with a total incidence of 2.2 million cases per year in the United States alone [1]. Paroxysmal or chronic AF can significantly affect patient's quality of life, leading to thrombembolic complications, impaired ventricular function, and significant health care costs. Moreover, AF is associated with a 1.5-fold to 1.9-fold increased risk of mortality in both men and women [2].
Over the past several years numerous attempts have been made to treat AF surgically. The most effective has been the Maze procedure, developed in the 1980s and leading to excellent long-term results [3, 4]. Unfortunately, it implies a complex operative procedure and the initial results have not been reproduced at other centers.
Meanwhile it has been demonstrated that the focus for the initiation of AF resides in the pulmonary veins [5]. Therefore, several different techniques of pulmonary vein isolation have been developed to cure AF [6].
It has been demonstrated that AF can be successfully cured by intraoperative radiofrequency ablation, results are comparable to the Maze procedure [7]. This can be achieved using a conventional sternotomy or a lateral minithoracotomy approach [8]. In the search to identify other energy sources to produce better ablation results, intraoperative cryoablation as an isolated or concomitant procedure has been developed. Cryotherapy involves the creation of a specific set of thermally induced transmural lesions to interrupt the circuits required to propagate atrial fibrillation [9]. It can be successfully applied solely to the left atrium because the ectopic electrical foci and reentrant circuits are usually anchored there [7]. Thus far, several investigators have described encouraging results with intraoperative cryoablation of the left atrium [9].
The object of this report is to present our early experience in the treatment of atrial fibrillation using a new flexible cryocatheter, the SurgiFrost CryoCath (Endocare Inc, Irvine, CA).
Material and methods
Cryoablation was performed in 28 patients between July 2002 and March 2003. The ablation was performed as an isolated procedure in 1 patient; in combination with mitral valve surgery in 13 patients; and in combination with other surgical procedures such as aortic valve surgery, aortic and mitral valve surgery, coronary artery bypass grafting, atrial septal defect closure, and aortic valve replacement in combination with replacement of the ascending aorta in 14 patients. A right anterolateral minithoracotomy with femoral access cardiopulmonary bypass was used in 20 patients (71%), whereas median sternotomy was performed in 8 patients (29%).
Demographics are presented in Table 1. Primary indication for rhythm-surgery was chronic atrial fibrillation (82%) or symptomatic paroxysmal atrial fibrillation (18%) refractory to medical treatment. The patients included 19 men and 9 women with a mean age of 60.0 ± 12.5 years with an average duration of AF of 6.8 ± 8.1 years (range 1 to 40 years). Mean left ventricular ejection fraction was 59.0% ± 11.8%, left ventricular end-diastolic diameter was 52.4 ± 9.1 and mean left atrial diameter was 55.9 ± 11.7 mm.
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The ablation procedure was performed as previously described [7, 8]. The right anterolateral minithoracotomy (4 to 6 cm) was performed in the fourth intercostal space and cardiopulmonary bypass was established by femorofemoral cannulation. The CO2 insufflation was used continuously throughout the operation to displace air from the operation field.
The femoral artery was cannulated using a 16Fr to 20Fr arterial cannula (Baxter Healthcare Corporation, Edwards Division, Irvine, CA). Venous drainage was established using a 22Fr cannula (Heartport Inc., Redwood City, CA) inserted into the femoral vein. On occasion an additional 16Fr cannula (Baxter Healthcare Corporation) was inserted into the right internal jugular vein for tricuspid valve repair. Vacuum assistance was used to enhance venous drainage.
The aorta was cross clamped using a direct transthoracic clamp (Chitwood Clamp, Scanlan International, Minnesota, MN) inserted percutaneously through the second intercostal space. Myocardial protection was achieved by using antegrade cold crystalloid cardioplegia or cold blood cardioplegia through a puncture in the ascending aorta.
A small left atriotomy was performed through an incision parallel to the interatrial groove and anterior to the right pulmonary veins. This enabled direct access to the mitral annulus as well as to the orifices of the pulmonary veins. The right atrium was not entered except for patients requiring concomitant tricuspid valve repair. The left atrial appendage was not excised or ligated.
Ablation technique
The cryoablation device (SurgiFrost CryoCath, Irvine, CA) using argon gas as the refrigerant, was used to create the lesions. Ablation is performed by removing heat from the arrhythmogenic target tissue. The hand-held probe (Fig 1) operates on the Joule-Thomson effect providing a 60-mm long malleable freezing segment (Ø = 3.9 mm) attached to a 170-mm malleable shaft. An adjustable isolation sleeve allows the ablation zone to be varied between 10 mm and 60 mm.
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Daily 12-lead electrocardiogram (ECG) was performed during the first 5 postoperative days in all patients. In addition, every patient received 24-hour holter monitoring twice. In case of recurrent AF during the first 10 postoperative days medical therapy using amiodarone or ß-blockers and eventually electrical cardioversion were performed. Patients in stable sinus rhythm (SR) received anticoagulation for 3 months and those patients requiring additional antiarrhythmic drugs received anticoagulation for 6 months. Before hospital discharge, as well as after 6 months, patients received 12-lead ECG and 24-hour holter monitoring.
Results
The intraoperative results of the treated patients are given in Table 2. The mean duration of ablation was 5.2 ± 0.5 minutes. The mean ablation temperature achieved was -143.8 ± 14.4°C (range -90 to -161°C). The average operation time was 167.3 ± 57.3 minutes (range 85 to 310 minutes).
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Comment
Thus far, the Maze procedure [3, 4] demonstrated the best success rate in treating patients with chronic AF.
Comparing our method of intraoperative radiofrequency ablation to the Maze procedure, the morbidity and mortality are very similar and the aortic cross-clamp times and cardiopulmonary bypass times are shorter. Hence, to minimize the complications associated with radiofrequency ablation [10] and to achieve better results, alternative energy sources for ablation need to be studied. Moreover, it has been demonstrated that the endothelial lesions produced by radiofrequency ablation have a higher risk of thrombus formation [9].
In this study we were able to use a new flexible cryocatheter, the Surgifrost CryoCath, to perform cryoablation using a technique previously described. We were able to achieve SR in 82% of the patients at discharge with minimal morbidity and no mortality. The flexibility of the catheter allowed it to be very versatile in performing the procedure through a lateral minithoracotomy.
The average hospital stay of 12.8 days is longer than compared with other cardiac surgical procedures. Our aim was to achieve SR. In 50% of all patients we observed recurrent early postoperative AF. We treated our 43% patients with amiodarone and 61% with ß-blockers. Nine patients (32%) required electrical cardioversion. This might be the explanation for the relatively long hospital stay.
In conclusion, on a rather small series of patients we have found that cryoablation with this new argon cryocatheter is efficient and safe. With this cryocatheter the ablation procedure can be easily performed using a lateral minithoracotomy with excellent results. This could possibly make the surgical treatment of AF become more attractive and promising. However, a larger number of patients need to be evaluated.
Disclosures and freedom of investigation
The cryoconsole and catheters were purchased by the Heartcenter Leipzig, Leipzig, Germany. The authors have performed a free and independent evaluation of this new technology. Doctors Doll, Kiaii, Fabricius, Bucerius, Kornherr, Krakor, Gummert, Walther, and Mohr have no financial relationship with the company Cryocath.
Footnotes
The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.
References
This article has been cited by other articles:
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  J. Seeburger, M. A. Borger, N. Doll, T. Walther, J. Passage, V. Falk, and F. W. Mohr Comparison of outcomes of minimally invasive mitral valve surgery for posterior, anterior and bileaflet prolapse Eur. J. Cardiothorac. Surg., September 1, 2009; 36(3): 532 - 538. [Abstract] [Full Text] [PDF]
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 M. Knaut, S. M. Tugtekin, S. G. Spitzer, F. Jung, and K. Matschke Intraoperative endocardial microwave ablation for treatment of permanent atrial fibrillation during coronary artery bypass surgery: 1-year follow-up. Europace, January 1, 2006; 8(1): 16 - 20. [Abstract] [Full Text] [PDF]
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