Ann Thorac Surg 2005;80:1081-1086
© 2005 The Society of Thoracic Surgeons
New technology
Epicardial Maze Procedure on the Beating Heart With an Infrared Coagulator
Hiroshi Kubota, MD
a
,
*
,
Shinichi Takamoto, MD
b
,
Akira Furuse, MD
c
,
Masaya Sato, MD
a
,
Hidehito Endo, MD
a
,
Tatsuo Fujiki, MD
a
,
Kenichi Sudo, MD
a
a Department of Cardiovascular Surgery, Kyorin University, Tokyo, Japan
b Department of Cardiothoracic Surgery, Tokyo University, Tokyo, Japan
c JR Tokyo General Hospital, Tokyo, Japan
Accepted for publication September 21, 2004.
* Address reprint requests to Dr Kubota, Shinkawa, Mitaka, 181-8611, Tokyo, Japan (Email: kub{at}kyorin-u.ac.jp).
 |
Abstract
|
|---|
PURPOSE: Maze surgery is widely used to treat atrial fibrillation (AF) but requires cardiopulmonary bypass and longer aortic cross-clamping time. Percutaneous transcatheter pulmonary vein (PV) isolation is time consuming and relies on fluoroscopy and contrast media, and PV obstruction and cardiac tamponade are still major problems. To overcome these drawbacks, we developed an epicardial maze procedure with an infrared coagulator on the beating heart, and the aim of this study was to confirm electrophysiologically the efficacy of this method.
DESCRIPTION: Light from a lamp in the infrared coagulator is focused into a quartz rod, and the distal exit-plane of the rod is connected to a sapphire tip that allows 10 mm of linear photocoagulation. In an experiment in 5 dogs with AF, instead of making all of the incisions usually required for maze surgery, the infrared coagulator was applied epicardially to create a continuously overlapping linear lesion that was the same as the incision line in the maze III procedure except for the intraatrial incision. After the procedure, 11 electrodes were attached to both atria, and an electrophysiologic study was performed.
EVALUATION: The electrophysiologic study confirmed electrophysiologic isolation of both atrial appendages and within the PV encircling lesion. Sustained atrial fibrillation could no longer be induced.
CONCLUSIONS: The epicardial maze procedure was successfully performed on a beating heart with the infrared coagulator.
|
Introduction
|
|---|
Percutaneous endocardial pulmonary vein (PV) isolation with radiofrequency was attempted after it had been demonstrated that a rapidly firing focus in the PVs can cause atrial fibrillation (AF), but the technique is time consuming and requires fluoroscopy and contrast media to identify the PVs [1]. Moreover, cardiac tamponade and PV obstruction are major complications [2]. The maze procedure, on the other hand, requires a cardiopulmonary bypass and a longer aortic cross-clamping time [3]. Many ablation devices have been produced to shorten AF treatment, but whether these devices (eg, radiofrequency, cryo, laser) are capable of reliably producing long, linear, continuous, transmural lesions in the atrial free wall remains unclear. We previously demonstrated the efficacy of epicardial infrared coagulation on the beating heart [4], and found that it was capable of producing linear transmural lesions on the atrium and also producing a bidirectional electrical block without cardiopulmonary bypass. To make the treatment of AF less invasive, we applied this device to our original epicardial maze procedure on the beating heart, and in this study we attempted to electrophysiologically and pathologically confirm the efficacy of the method.
|
Material and Methods
|
|---|
The IRK-151 infrared coagulator (Infrarot-Kontaktkoagulator; Messerschmidt-Bolkow-Blohn, Frankfurt, Germany) was originally developed as an alternative to high-frequency electrocoagulation or laser coagulation to ensure hemostasis of bleeding parenchyma. A reflector in the infrared coagulator focuses light from a tungsten-halogen lamp into a light-conducting 10 mm diameter quartz rod, and it emerges as 35 W/cm2 of near-infrared light energy (wavelength, 400 to approximately 1600 nm; peak wavelength, 850 nm). The distal exit-plane of the light-conducting rod is connected to the tip of the coagulator. Because the original IRK-151 contains a 3-second timer and the plastic body of the IRK-151 is not strong enough to tolerate the long coagulation time, we modified the coagulator to make it strong enough for atrial ablation by substituting a 40-second timer and changing the body from plastic to metal. To allow linear atrial myocardial ablation, we produced an original artificial sapphire tip by polishing the surface of a cylindrical sapphire on the bias (Fig 1). The tip has a rectangular (1.5 x 10 mm) edge surface.
View larger version (59K):
[in this window]
[in a new window]
|
Fig 1. (A) Infrared coagulator: the plastic body has been replaced by a metal body to enable it to tolerate the long duration of the coagulation. (B) Sapphire tip: the edge of the tip has a rectangular (1.5 x 10 mm) edge surface.
|
|
Five mongrel dogs weighing 14.5 ± 2.3 kg were anesthesized with ketamine hydrochloride (20 mg/kg, intramuscularly) and sodium pentobarbital (16 mg/kg, intravenously), and were ventilated. All animals received humane care in accordance with the "Guide for the Care and Use of Laboratory Animals" published by the National Institutes of Health (NIH publication 85-23, revised 1985). After median sternotomy, both pleural cavities are openand the vagal nerves are exposed. The pericardium was then opened, and a bipolar electrode was attached to the right atrium. Sustained AF was induced preoperatively by bilateral vagal nerve stimulation (pulse width 0.2 ms, 3 V, 10 Hz) followed by 2 hours of burst stimulation of the atrium. A tape was passed around the superior vena cava (SVC), another around the inferior vena cava (IVC), and a third around the ascending aorta and the main pulmonary artery through the transverse sinus. The tissue behind the SVC and IVC was carefully dissected to expose the left atrium; and after ligating and dividing the azygos vein, the infrared coagulation was performed. Instead of all the incisions of the maze III procedure, except the intraatrial septal incision, the infrared coagulator was applied epicardially to create continuous overlapping linear lesions (Fig 2, A). The duration of application for each ablation was 9 seconds, and a 10-mm lesion was created. After completion of all of the lesions, 11 bipolar electrodes were attached to the wall of each atrium (Fig 2, B). An electrocardiogram (ECG) and atrial potentials were recorded with an HPM 4500 polygraph (Fukuda Denshi, Tokyo, Japan).
View larger version (37K):
[in this window]
[in a new window]
|
Fig 2. (A) Lesion pattern. Coagulation was performed along the incision line of the Maze III procedure, except intraatrial septal incision. (B) Location of the electrodes (1 to 11). After the procedure, 11 bipolar electrodes were placed in the atrial wall, and the potentials were recorded. (IVC = inferior vena cava; LAA = left atrial appendage; MV = mitral valve; RAA = right atrial appendage; SN = sinus node; SVC = superior vena cava; TV = tricuspid valve.)
|
|
The recording conditions were as follows: (1) spontaneous beating; (2) overdrive pacing from the right atrial appendage (RAA); (3) overdrive pacing from the left atrial appendage (LAA); and (4) overdrive pacing from inside the PV encircling lesion.
After recording the atrial potentials, burst stimulation was applied in an attempt to induce AF. If it failed the first time, we tried two more times. After the experiment, the coagulated left atrial wall was excised, fixed, and stained (hematoxylin-eosin, AZAN), and histologic sections were examined microscopically.
|
Results
|
|---|
No potentials were detectable within the RAA, LAA, or PV encircling lesion during spontaneous beating, but other areas of the atrium exhibited sinus rhythm (Fig 3, A). During overdrive pacing from the RAA, the atrial potential subsequent to the pacing was detected only in the RAA. Other areas exhibited sinus rhythm (Fig 3, B). During overdrive pacing from the LAA, only the area within the LAA lesion was activated by the stimulus. Other areas exhibited sinus rhythm (Fig 3, C) During overdrive pacing from inside the PV encircling lesion, only the area within the PV encircling lesion was activated by the stimulus. Other areas exhibited sinus rhythm (Fig 3, D)
View larger version (69K):
[in this window]
[in a new window]
|
Fig 3. (A) Atrial potential during spontaneous beating. No potential was detected within the right atrial appendage ([RAA] electrode no. 3). Other areas of the atrium exhibited sinus rhythm. No potentials were detected with the electrodes within the left atrial appendage (LAA) or pulmonary vein (PV) encircling lesion (electrodes nos. 7, 10, and 11) either. (B) During overdrive pacing from the RAA (electrode no. 3), only the area within the RAA lesion was activated by the stimulus. Other areas exhibited sinus rhythm. (C) During overdrive pacing from the LAA (electrode no. 7), only the area within the LAA lesion was activated by the stimulus. Other areas exhibited sinus rhythm. (D) During overdrive pacing from inside the PV encircling lesion, only the area within the PV encircling lesion (electrode no. 10) was activated by the stimulus. Other areas exhibited sinus rhythm. Electrode no. 11 was used to stimulate the atrium.
|
|
None of the three areas inside the encircling lesion exhibited any potentials during sinus rhythm, and only these lesions were activated by the overdrive stimulus from inside the lesions. Other areas always exhibited sinus rhythm with or without the pacing from inside the encircling lesions. Although we tried to induce AF three times in each dog after completing the ablation, burst stimulation failed to induce AF in any of the dogs. Histologic examination showed preservation of both the endocardium and epicardium of the coagulated lesion. Well-demarcated transmurally degenerated myocardium was demonstrated (Fig 4).
View larger version (63K):
[in this window]
[in a new window]
|
Fig 4. (A) Histologic changes in the left atrium. Well-demarcated transmurally degenerated myocardium was demonstrated. Both the endocardium and the epicardium were intact. (B) Schematic of the left atrium.
|
|
Burst stimulation did not induce AF in any of the dogs. No ST-T changes or arrhythmias occurred during ablation.
|
Comment
|
|---|
Is the warm beating heart more suitable for infrared coagulation than the cardioplegic arrested heart? Ohtake and associates [6] compared the depth, width, and volume of the myocardium coagulated with a Nd-YAG laser in the warm red beating heart and in the cold white nonbeating heart infused with 0°C saline (cardioplegic model) through the coronary artery. The depth, width, and volume of red myocardium coagulated were significantly greater than in the white myocardium, and the volume of white myocardium coagulated was about 60% of the volume of the red myocardium that was coagulated. They concluded that Nd-YAG laser energy was absorbed by the blood (red color indicates hemoglobin) and that a higher temperature was transmitted to the myocardium. Accordingly, because infrared rays are capable of producing photocoagulation that is equivalent to laser coagulation, the beating heart is preferable for obtaining efficient myocardial coagulation with infrared rays.
Several energy sources can be used to achieve epicardial atrial coagulation. Because blood flow within the beating heart weakens the thermal effect on the atrium, it is difficult to produce transmural lesions in the atrial "free" wall with devices that rely on other energy sources, for example, with radiofrequency, microwave, and cryo. In contrast to these energy sourses, the infrared rays easily reach the endocardial side of the myocardium and produce a transmural lesion. That is the unique characteristic of this device. To develop a new ablation device, it is important not only to produce the transmural lesion, but also to preserve the endocardium and epicardium to prevent atrial perforation and thromboembolism. Histologic examination revealed photonecrosis in the ablated myocardium without carbonization or vaporization, and the epicardium and the endocardium were intact. The photoenergy passes through them because both of them are translucent and when the energy reaches the myocardium, a higher temperature is transmitted.
We previously demonstrated the following other unique characteristics of the infrared coagulator [4, 5]. It produces a well-demarcated transmural lesion that is capable of creating a bidirectional electrical block in the beating atrial free wall. It is easy to control the depth of the lesion by varying the duration of application, and its electrophysiologic effect is permanent. Those results encouraged us to try the epicardial maze procedure in the beating heart. Since our previous experiment showed that 9 seconds of coagulation could create a 6.5 mm deep lesion in the beating canine right ventricle [4], and the coagulation time in the present study was set at 9 seconds. Although the myocardium of the atrium and the ventricle are different histologically, the 9 seconds of coagulation was thought to be adequate to create a transmural lesion in the thinner left atrium.
There are three encircling lesions in the maze III procedure, one each in the RAA, LAA, and PV encircling lesion. These encircling lesions are suitable for verifying the efficacy of the ablation, because when continuous transmural coagulation is achieved, the lesions are electrically isolated. If there is locally incomplete ablation, the bidirectional electrical block is not achieved, and the lesion is not isolated. Complicated electrophysiologic mapping is not required. All three lesions in our experiment were confirmed to be isolated electrophysiologically in all dogs, suggesting that the coagulator is capable of being used to make continuous transmural lesions in both atria.
The intraatrial septum was not ablated in our procedure because cardiopulmonary bypass is necessary to expose the intraatrial septum. Although the contribution of the intraatrial incision to the effectiveness of the maze procedure is not well known, omitting the intraatrial ablation in our experiment did not interfere with prevention of AF induction. Vagus nerve and atrial burst stimulation were used to create a model of AF. Since Yamashita and colleagues [7] reported that the earliest mRNA induction that modifies the atrial potassium channel and shortens the atrial refractory period begins only 30 minutes after continuous burst stimulation, we tried creating a model of AF induced by vagus nerve stimulation followed by 2 hours of burst stimulation before ablation. A model of stable sustained AF was achieved in all dogs by this procedure, and it improved the reliability of our experiment in demonstrating the efficacy of the treatment of AF. Future studies are needed in a clinical setting.
The results of many methods of treatment of AF, such as by radiofrequency, microwaves, ultrasound, and cryoablation, have been reported clinically [8–11], and various modifications of the ablation line have also been reported [12–16]. Most clinical reports have focused on the rate of conversion of AF to sinus rhythm as a means of evaluating the efficacy of the procedure. However, before assessing the efficacy of the new procedure it is essential to demonstrate that the device used is capable of producing a continuous transmural lesion in the atrium and of creating an electrophysiologic conduction block. Having demonstrated the effectiveness of the ablation device, we can now proceed to assess modification of the ablation line with the device.
|
Disclosures and Freedom of Investigation
|
|---|
The authors had full control of the design of the study, methods used, outcome measures, and production of the written report.
|
Disclaimer
|
|---|
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.
|
Acknowledgments
|
|---|
This work was supported by Grant-in-Aid for Scientific Research from the Japanese Ministry of Education and Science, 1994, 1995, 2000, 2001 to 2003; Japan Heart Foundation/Pfizer Grant for Cardiovascular Disease Research, 2000; and Fujita Memorial Fund for Medical Research, 2001. We are grateful to Mitsuru Kobayashi and Seiji Sato (Fukuda Denshi, Tokyo, Japan) for their very skillful technical help with the HPM-7100 mapping system.
|
References
|
|---|
- Haissaguerre M, Jais P, Shah DC, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins N Engl J Med 1998;339:659-666.[Abstract/Free Full Text]
- Robbins IM, Colvin EV, Doyle TP, et al. Pulmonary vein stenosis after catheter ablation of atrial fibrillation Circulation 1998;98:1769-1775.[Abstract/Free Full Text]
- Cox JL, Jaquiss RDB, Schuessler RB, Boineau JP. Modification of the MAZE procedure for atrial flutter and atrial fibrillation II. Surgical technique of the MAZE III procedure J Thorac Cardiovasc Surg 1995;110:485-495.[Abstract/Free Full Text]
- Kubota H, Furuse A, Takeshita M, Kotsuka Y, Takamoto S. Atrial ablation with an IRK-151 infrared coagulator Ann Thorac Surg 1998;66:95-100.[Abstract/Free Full Text]
- Kubota H, Takamoto S, Takeshita M, Miyaji K, Kotsuka Y, Furuse A. Atrial ablation using an IRK-151 infrared coagulator in canine model J Cardiovasc Surg 2000;4:835-847.
- Ohtake H, Watanabe G, Mukai K, et al. Basic study of myocardial coagulation by intraoperative laser ablationin the presence and absence of blood. Kyobu Geka 1992;45:870-872.[Medline]
- Yamashita T, Murakawa Y, Hayami N, et al. Short-term effects of rapid pacing on mRNA level of voltage-dependent K(+) channels in rat atriumelectrical remodeling in paroxysmal atrial tachycardia. Circulation 2000;25:2007-2014101.
- Mohr FW, Fabricius AM, Falk V, et al. Curative treatment of atrial fibrillation with intraoperative radiofrequency ablationshort-term and midterm results. J Thorac Cardiovasc Surg 2002;123:919-927.[Abstract/Free Full Text]
- Spitzer SG, Richter P, Knaut M, Schuler S. Treatment of atrial fibrillation in open heart surgery—the potential role of microwave energy Thorac Cardiovasc Surg 1999;47(Suppl 3):374-378.
- Natale A, Pisano E, Shewchik J, et al. First human experience with pulmonary vein isolation using a through-the-balloon circumferential ultrasound ablation system for recurrent atrial fibrillation Circulation 2000;102:1879-1882.[Abstract/Free Full Text]
- Kubota H, Takamoto S, Morota T, et al. Epicardial pulmonary vein isolation by cryoablation as concomitant cardiac surgery to treat non-valvular atrial fibrillation Ann Thorac Surg 2003;75:590-593.[Abstract/Free Full Text]
- Pasic M, Bergs P, Muller P, et al. Intraoperative radiofrequency maze ablation for atrial fibrillationthe Berlin modification. Ann Thorac Surg 2001;72:1484-1490.[Abstract/Free Full Text]
- Deneke T, Khargi K, Grewe PH, et al. Left atrial versus bi-atrial Maze operation using intraoperatively cooled-tip radiofrequency ablation in patients undergoing open-heart surgerysafety and efficacy. J Am Coll Cardiol 2002;39:1644-1650.[Abstract/Free Full Text]
- Khargi K, Deneke T, Haardt H, et al. Saline-irrigated, cooled-tip radiofrequency ablation is an effective technique to perform the maze procedure Ann Thorac Surg 2001;72(Suppl):S1090-S1095.[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 surgery J Am Coll Cardiol 2000;36:159-166.[Abstract/Free Full Text]
- Tanaka H, Narisawa T, Mori T, et al. Pulmonary vein isolation for chronic atrial fibrillation associated with mitral valve diseasethe midterm results. Ann Thorac Cardiovasc Surg 2002;8:88-91.[Medline]
This article has been cited by other articles:
|
|
|
|
 
H. Kubota, K. Sudo, S. Takamoto, K. Tonari, T. Fujiki, H. Endo, H. Tsuchiya, and A. Furuse
Epicardial electrical isolation of the right atrial appendage on the beating heart with an infrared coagulator.
Ann. Thorac. Surg.,
May 1, 2009;
87(5):
1592 - 1595.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Pasic and R. Hetzer
Invited commentary
Ann. Thorac. Surg.,
September 1, 2005;
80(3):
1086 - 1086.
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
