Ann Thorac Surg 2007;84:1408-1411
© 2007 The Society of Thoracic Surgeons
How To Do It
Intraoperative Cryoablation of Atrial Fibrillation With the Old-Fashioned Cryode Tips: A Simple, Effective, and Inexpensive Method
Fernando Hornero, MD, PhD*,
Ignacio Rodríguez, MD,
Vanesa Estevez, MD,
Alejandro Vázquez, MD,
Oscar Gil, MD,
Sergio Canovas, MD,
Rafael García Fuster, MD, PhD,
Juan Martínez-León, MD, PhD
Department of Cardiac Surgery, Consorcio Hospital General Universitario de Valencia, Universidad de Valencia, Valencia, Spain
Accepted for publication February 12, 2007.
* Address correspondence to Dr Hornero, Servicio de Cirugía Cardiaca, Consorcio Hospital General, Universitario de Valencia, Av Tres Cruces s/n, Valencia, 46014, Spain (Email: hornero_fer{at}gva.es).
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Abstract
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Nowadays atrial fibrillation is usually treated simultaneously with cardiac procedures, and new cryo-systems have been developed for performing easier and faster intraoperative ablation. However, the old cryode designs can still be useful in surgical practice and represent a more cost-effective method. In this article we present a technique using old-fashioned cryodes for intraoperative treatment of atrial fibrillation and comment on its advantages and limitations.
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Introduction
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Operative treatment of atrial fibrillation (AF) has now earned a permanent place in the surgical arena. Surgeons are familiar with the different interventional techniques, and the indications have been progressively broadened. Modern intraoperative ablation devices allow us to reproduce patterns of atrial lesions and can be safely used with simultaneous cardiac procedures. These promising new surgical tools have increased intraoperative treatment of AF, but their financial costs are high and the physician must consider the short-term and long-term cost effectiveness. The AF recurrence rate is probably the most frequent problem associated with the ablation procedure. A recent meta-analysis, based on 69 surgical ablation studies, reports rates of freedom from late AF between 92% and 73.4% [1]. Khargi and colleagues [2] reviewed 48 clinical studies with long-term follow-up results and reported that postoperative sinus rhythm recovery rate was 78.3% (21.7% recurrence) with different ablation energies. The substantial number of patients with a possibly unsuccessful ablation process and facing financial difficulties has prompted a review of traditional cryo-systems to take the fullest advantage of their potential. In this setting, we used the classical cryosurgical console using diverse old-fashioned tips that had been rescued from the armamentarium of other surgical units, adapted to the morphologic conditions required for each lesion.
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Technique
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The left atrium (LA) was approached through the interatrial groove used with a wide dissection of the interatrial groove until reaching the fossa ovalis. All the ablation lines of the LA were endocardics during cross-clamp time, and in the right atrium epicardially off pump with the same freezing protocol in both chambers. Cryoablation was performed using conventional refrigerant fluid (NO2) under pressure into the inner lumen. The cryode was connected to a console (Erbocryo CA, Erbe Electromedicin GmbH, Tübinger [Germany]) that delivered the refrigerant fluid. The minimum freezing temperature of approximately –80°C was reached in 5 seconds. Cryo-lesions were formed by 2 minutes of ice-ball at –70°C. The same cryoprobe allowed us to use diverse tip shapes, which were changed depending on the area for freezing.
Four types of tips of different design were used according to the area of the atrium to be frozen, (Fig 1). With conical tips the whole antrum of pulmonary veins (PVs) can usually be ablated with a single freezing cycle, especially the left pulmonary veins, with minimum risk of a gap, because the lesion is not a lineal periostium, but consists of the entire PV antrum endocardial surface area (Figs 2, 3a–b).
The flat-circle tip used in the left isthmus is similar to that used in the coronary sinus of the classical maze (Figs 3c–d). The posterior LA is performed with the linear tip in one or two applications (Fig 3f). The cavo-tricuspid isthmus can be carried out with a single application of the conical or cylindrical linear tip (Fig 3e). The right atrium pattern of lesions can be reproduced using the cylindrical linear tip. The LA maze is normally carried out with 7 to 10 applications, and the right atrium with 5 to 7.
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Fig 1. Tips for the cryoprobe (dermatologic and gynecologic models Erbocryo CA, Erbe Electromedicin GmbH, Tübinger [Germany]). (a) Conical tip of 25 mm in diameter x 21 mm in height used for the application of the pulmonary vein antrum. (b) Flat-circle tip 19 mm in diameter. (c) A cylindrical tip of 29 mm in height x 9 mm in diameter for linear lesions. (d) Conical tip of 21 mm in diameter x 21 mm in height used for the application of the pulmonary vein antrum.
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Fig 2. Scheme of pulmonary vein antrum cryoablation. The conical cryode can freeze and adhere to the adjacent tissue and complete ablation of the myocardium tissue of the pulmonary veins antrum is performed. As the heat source of the remaining pulmonary venous flow is occluded by the cryode, ice-ball within the thick atrium adjacent to the veins is achieved. (LA = left atrium; PVs = pulmonary veins.)
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Fig 3. Intraoperative images of the cryoablation. (a) Left pulmonary vein ice-ball with the conic tip that freezes the left antrum. (b) Antrum freeze with the shape of the conic-tip immediately after the cryoablation. (c) Left isthmus ice-ball with the conic tip. (d) Left isthmus freeze with the shape of the conic-tip. (e) Epicardial freeze of the right isthmus between the inferior vena cava and the right coronary artery. (f) Shows posterior line of the left atrium with the long cylindrical tip. (IVC = inferior vena cava; LPVS = left pulmonary veins; MV = mitral valve; RPVS = right pulmonary veins.)
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From June 2000 to June 2006, this technique was used on 56 patients in permanent AF (>3 months) who underwent cardiac surgery including intraoperative cryoablation of the arrhythmia. All patients had concomitant organic heart disease, 56 patients (100%) were affected by mitral valve disease, 8 (14%) had tricuspid valve disease, 16 (28%) had aortic valve disease, 11 (20%) had coronary artery disease, 1 (1.7%) had atrial septal defect type fossa ovalis, and one (1.7%) had a resection of ascending aorta aneurysm. Mean LA size was 51 ± 9 mm, longstanding of the AF was 6.5 ± 6.0 years. Pattern of LA lesions with the right isthmus (mini maze) in 49 patients and bi-atrial in only 7 patients was performed according to the surgeon’s criteria (Fig 4). Left appendage was not excised, although it was closed with an internal suture in two cases in which an intraoperative thrombus was found. All operative data and surgical procedures are listed in Table 1. No complications were observed during the procedure. Amiodarone was initiated in the immediate postoperative period (1,200 mg endovenous/day during the first 48 hours) and continued for at least 3 months by oral administration (200 mg/day). Sotalol was administered in cases of contraindication (80–160 mg/day). During intrahospital time, postoperative AF recurrence was not electrically cardioverted, except in cases that presented hemodynamic intolerance of the arrhythmia. Programmed electrical cardioversion was performed between postoperative months 1 and 3. During the late follow-up, new persistent, permanent AF or flutter episodes were always treated with electrical cardioversion, with a maximum of two new attempts in which the surgical ablation process was then considered as ineffective and the AF again as permanent. Postoperative controls during the follow-up were carried out on the day of discharge, after 3 and 6 months, and annually, with an electrocardiogram and echocardiography. After a mean follow-up of 296 days (526 patients/mo), 80% of patients achieved sinus rhythm. One patient needed a DDD pacemaker implantation. Freedom in the use of antiarrhythmic medication occurred in 43% of patients, anticoagulation in 39%, and complete freedom of both types of medication in 21%. Two patients had late left atrial tachycardia; one with a re-entry around the patch area of fibrosis in the posterior LA wall treated with a percutaneous ablation procedure. In the echocardiography controls during the follow-up, no patients had PV stenosis develop.
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Fig 4. Pattern of cryoablation lesions. Black area and lines represent the cryothermal lesions. Left atrium (LA) with cryoablation of the antrums of the pulmonary veins (a), with the posterior wall (pw) and mitral isthmus (mi) lines. Right atrium (RA) with lines on the right isthmus (ti), crista terminalis (ct), right atrial appendage (rap), and fossa ovalis (fo). (lap = left atrial appendage.)
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Comment
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Cryoablation was the first method of treating intraoperative arrhythmias, and is probably one of the safest energies. The properties of cryothermal lesions are advantageous when ablation is required within venous structures, such as PVs, coronary sinus, and superior venous cava, or at LA sites close to adjacent structures, such as the phrenic nerve, esophagus, and coronary artery. New cryo-systems specially designed for treatment of AF minimizing the maze atrial pattern are fast and have a greater capacity for freezing tissue. However this new technology means a more expensive surgical procedure. In this setting we have successfully used various conventional consoles with old-fashioned cryode tips that were rescued from the armamentarium of other surgical units. Experiences with old cryo-systems in AF treatment have been reported previously, and were usually used with a 15-mm flat circle cryode [3, 4] or 4-cm linear probe [5]. In our experience, old cryodes have both advantages and limitations; they provide a safe and effective ablation system and the procedure is less costly because all the accessories are re-sterilizable. In difficult situations, when the LA is small or left PVs are difficult to see, old cryodes offer precise manipulation and stabilization. Use of the rigid cryoprobe with a conical tip allows easier, faster, and less traumatic placement of the cryoprobes, especially in the antrum of the left PVs. They are easy to use with stable adhesion of the tip to the endocardium during freezing, and they do not preclude or complicate continuing with the primary cardiac procedure at the same time. The contact surface of the conical tip creates a bigger ablation area of the PV ostiums and antrum, probably avoiding possible gaps in the PVs, although it remains unclear whether it can improve the efficacy of cryoablation. However it has the limitations and disadvantages of the old cryo-systems. The main limitation is that it has a slower and lower freezing capacity, with a mean time for the complete ablation procedure of approximately 25 to 30 minutes, and the endocardial freezing process needs a bloodless field. We also have reservations about its capacity for achieving transmurality freezing epicardially off pump, although we performed right atrium lesions with apparently satisfactory results.
We concluded that the classic cryo-console is old technology with certain limitations, but that it provides a safe, effective, and cost-saving technique. It is also probable that further important clinical applications can still be obtained from it.
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References
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- Barnett SD, Ad N. Surgical ablation as treatment for the elimination of atrial fibrillation: a meta-analysis J Thorac Cardiovasc Surg 2006;131:1029-1035.[Abstract/Free Full Text]
- Khargi K, Hutten B, Lemke B, Deneke T. Surgical treatment of atrial fibrillation: a systematic review Eur J Cardiothorac Surg 2005;27:258-265.[Abstract/Free Full Text]
- Chen MC, Guo GB, Chang JP, Yeh KH, Fu M. Radiofrequency and cryoablation of atrial fibrillation in patients undergoing valvular operations Ann Thorac Surg 1998;65:1666-1672.[Abstract/Free Full Text]
- Gaita F, Gallotti R, Calo L, et al. Limited posterior left atrial cryoablation in patients with chronic atrial fibrillation undergoing valvular heart disease J AM Coll Cardiol 2000;36:159-166.[Abstract/Free Full Text]
- Nakajima H, Kobayashi J, Bando K, et al. The effect of cryo-maze procedure on early and intermediate term outcome in mitral valve disease: case matched study Circulation 2002;106(Suppl I):I46-I50.[Medline]
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Abstract
Introduction
