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Innovations: Technology & Techniques in Cardiothoracic & Vascular Surgery:
Review Articles: Original Articles

Cardioscopic Trans-septal Cryoablation of Left Atrium in Nonmitral Cases

Ohtsuka, Toshiya MD; Ninomiya, Mikio MD; Maemura, Taisei MD

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From the Department of Cardiovascular Surgery, Tokyo Metropolitan Fuchu General Hospital, Tokyo, Japan.

Address correspondence and reprint requests to Dr. Ohtsuka, 2-9-2 Musashidai, Fuchu-shi, Tokyo 183-0042 Japan; e-mail: ootsuka-cvs@fuchu-hp.fuchu.tokyo.jp.

This study was presented in part at the 8th ISMICS Scientific Meeting, New York, NY.

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Abstract

Background: A modified maze procedure in which trans-septal cardioscopy was used for cryoablation in the left atrium is described.

Methods: The technique was used in 11 consecutive patients (9 men and 2 women, 56.5 ± 19.8 years) with permanent atrial fibrillation (Af) and concomitant nonmitral cardiac or aortic disease: aortic valvular disease in 4 patients, atrial septal defect (ASD) in 2 patients, tricuspid regurgitation in 2 patients, acute aortic dissection in 1 patient, arch aneurysm in 1 patient, and coronary artery disease in 1 patient. The mean Af duration detected in 7 cases was 18.5 ± 10.1 months. Partial sternotomy was used in aortic valve replacement, ASD closure, and tricuspid valve plasty, and fullsternotomy was used in aortic graft replacement and coronary artery bypass. Cardiopulmonary bypass was established, aortic cross-clamp was performed, a right atriotomy was created, a cryoablation probe and cardioscope (3 mm) were introduced into the left atrium through a 1-cm cut at the fossa ovalis or ASD, and cardioscopic left-atrial endocardial cryoablation was performed. The right-side maze procedure was conducted directly. The atrial appendages were excised in each case.

Results: Left-atrial cardioscopic cryoablation required 25.0 ± 5.5 minutes, and no deaths or procedure-related morbidities occurred. The mean follow-up period was 12 ± 8.5 months. One patient with tricuspid regurgitation died of liver failure. With the exception of coronary and acute dissection cases, all patients have maintained a sinus rhythm.

Conclusion: Although experience is limited, videocardioscopic trans-septal left-atrial cryoablation is a viable method for nonmitral Af cases, and the partial sternotomy approach can be performed.

Surgical treatment of atrial fibrillation (Af) is often performed in patients undergoing cardiopulmonary bypass–assisted surgery for concomitant cardioaortic disease. The maze procedure, originated by Cox et al., has become the standard procedure used for the surgical treatment of permanent or intermittent atrial fibrillation.1,2 In this procedure, both atria are electrically separated into small compartments by atriotomy and cryoablation to prevent electrical macroentry at each compartment, and conduction from the sinus node to the atrioventricular node is preserved.

In the usual left-atrial maze procedure, endocardial cryoablation is performed directly through a right-sided left atriotomy, which is created anterior to the pulmonary veins (PVs). Instead of the direct left atriotomy approach, we applied a new technique, the video-assisted minicardioscopy approach through a small cut in the fossa ovalis or a congenital atrial septal defect (ASD), for patients in whom the mitral valve remained uninvolved. This article describes the method and clinical outcomes of this technique.

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METHODS

Since April 2002, the present technique has been applied in 11 consecutive patients (9 men and 2 women, 56.5 ± 19.8 years) with permanent Af and concomitant nonmitral cardioaortic disease: aortic valvular disease in 4 patients, ASD (secundum type) in 2 patients, severe tricuspid regurgitation (TR) in 2 patients, coronary artery disease (CAD) in 1 patient, acute aortic dissection in 1 patient and aortic arch aneurysm in 1 patient. The duration of arrhythmia was often unknown, probably longer than 3 years in 4 cases. In 7 patients with a known period of arrhythmia, the mean was 18.5 ± 10.1 months. The mean size of the left atrium (LA) on a longitudinal echocardiography view was 54.4 ± 6.1 mm. The fibrillation waves were over 1 mV in the V1 electrocardiography lead in each case. Preoperative electrophysiologic tests were not available for any of the patients.

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Instrumentation and Surgery

A 3-mm-diameter, 30-degree rigid endoscope (Karl Storz, Tuttlingen, Germany) was used for cardioscopy, and T-shaped and straight cryoablation probes (Cooper Surgical, Inc., Trumbull, CT) were used for the maze procedure.

A partial sternotomy approach was used in cases of aortic valvular disease, ASD, and TR, and a full-length sternotomy was made in patients with aortic and coronary artery disease. Total cardiopulmonary bypass was established using bicaval drainage and occlusion, and left atrial venting via the right superior PV was conducted. The patients were cooled down to 28°C and an aortic cross-clamp and cardiac arrest were performed. Thereafter, the right atriotomy was performed, and the T-shaped cryoablation probe and cardioscope were introduced into the LA through a 1-cm cut at the fossa ovalis or ASD. The anatomy of the LA, including the ostia of each PV and the left atrial appendage (LAA), was precisely identified videoscopically, and videocardioscopic endocardial cryoablation was performed (Figs. 1 and 2). Cryolesions were created around the four PVs, between the PV-encircling cryolesion and the middle of the posterior mitral valvular annulus, and between the PV-encircling lesion and the base of the LAA. Finally, the cryolesion between the PV-encircling lesion and the septotomy or ASD was created using the straight cryoprobe. Each cryoablation was 2 minutes, and the temperature was –75°C. Thereafter, the septotomy or ASD was closed, and the concomitant cardiac or aortic procedure was performed; aortic valvular replacement with bioprosthetic valve in 4 patients, tricuspid valvular plasty in 2 patients, coronary artery bypass in 1 patient, graft replacement of the dissected ascending aorta in 1 patient, and arch replacement in 1 patient. In the TR and CAD cases, valvular and coronary artery operations were performed on the beating heart after the aortic clamp was released. After declamping, cryoablation for the right atrium was performed directly and the right atriotomy was closed. Both atrial appendages were excised in all cases.

Figure 1
Figure 1
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Figure 2
Figure 2
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RESULTS

In each patient, the present videocardioscopic left-atrioendocardial cryoablation required 25.0 ± 5.5 minutes of aortic cross-clamping. There was no conversion to the direct left atriotomy approach. The partial sternotomy, a T-shaped one for TR and ASD cases and a reverse T-shaped one for aortic valvular disease cases, was not converted to full-sternotomy approach in any patients. No deaths or procedure-related morbidities occurred. At the time of discharge, sinus rhythm was maintained via electrocardiography in all patients, except in the case of acute aortic dissection.

Each patient was followed up with electrocardiography and an interview at the outpatient clinic 1, 3, and 6 months and 1, 2, and 3 years after discharge. The mean follow-up period was 12 ± 8.5 months, and ranged from 2 months to 3 years. All patients received oral anticoagulant therapy, including warfarin for at least 6 months after surgery, digoxin, and/or disopyramide. The patient on coronary artery bypass was converted back to Af 1 month after discharge. Although sinus rhythm had been maintained, 1 patient with TR died of liver failure 3 months after surgery. As of August 2005, sinus rhythm has been maintained in 10 patients (80% of the live cases).

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CONCLUSION

Cox et al. introduced their original maze procedure in 1991 and developed the Cox-maze III technique with excellent clinical outcomes1,2 Bando et al.3 demonstrated the clinical results of maze operation in mitral plasty cases and documented that the patient group treated with mitral valve plus Af surgery had a better prognosis than the group treated with only the valvular operation. Although further investigation is necessary, Af surgery is also likely to improve the prognosis of nonmitral cases, eliminating the potential risk of atrial thrombus–related stroke and other arrhythmia-associated complications.

Today, although different energy sources (laser, microwave, and radiofrequency) have been applied endocardially or epicardially,4,5 endocardial cryoablation is the safest and most reliable method with acceptable transmurality and durability. Kosakai et al.6 developed a modified method in which cardiotomies were reduced and cryoablation was used more extensively to minimize hemorrhage from atriotomies and preserve the sinus node artery. Their clinical results, including sinus rhythm recovery, were as good as the outcomes of the Cox method. Although limited to nonmitral cases, our cardioscopic technique is actually a modified Kosakai’s technique in which the left atriotomy, with the exception of the LAA division, has been eliminated. The 3-mm cardioscope is the most important tool in the present technique. This miniscope was only recently developed and enables excellent intra-atrial visualization via a small septal entry.

In the present patient series, we experienced 1 CAD case. Recently, off-pump coronary artery bypass has been developed and conducted in an increasing number of patients, and new technology enables epicardial ablation for PV electrical isolation, which is achievable without cardiopulmonary bypass.7,8 Thus, although the clinical outcome should be examined carefully, combination of off-pump coronary artery bypass and Af surgery with the new technology might become a less invasive optional treatment for CAD cases with Af.

Many surgeons have been using a partial sternotomy for aortic valvular replacement and the right heart surgery, such as operations for TR and ASD.9 Although this approach is less invasive and cosmetically favorable, the standard left-atrial maze procedure, which is performed directly via the right-sided left atriotomy, is challenging through the limited wound. In 8 cases in the present series, although the limited sternotomy was chosen, cryoablation of the LA was enabled by approaching the LA from the anterior side, which is the atrial septum, and by using cardioscopy.

In conclusion, although our experience is limited, videocardioscopic endocardial left-atrial cryoablation via a small septotomy or ASD is a feasible procedure with acceptable results. This technique can be applied to nonmitral cases with Af, and the limited sternotomy approach can be used.

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REFERENCES

1. Cox JL. The surgical treatment of atrial fibrillation. IV. Surgical technique. J Thorac Cardiovasc Surg. 1991;101:584–592.

2. Cox JL, Jaquiss RD, 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.

3. Bando K, Kasegawa H, Okada Y, et al. Impact of preoperative and postoperative atrial fibrillation on outcome after mitral valvuloplasty for nonischemic mitral regurgitation. J Thorac Cardiovasc Surg. 2005;129:1032–1040.

4. Mohr FW, Fabricius AM, Falk V, et al. Curative treatment of atrial fibrillation with intraoperative radiofrequency ablation: short-term and midterm results. J Thorac Cardiovasc Surg. 2002;123:919–927.

5. Kress DC, Tector AJ, Schmahl TM, et al. Off-pump epicardial ablation for atrial fibrillation: Comparison of microwave and radiofrequency techniques. Abstract presented at the 5th Annual Meeting of the International Society for Minimally Invasive Cardiac Surgery, New York, NY, June 20–23, 2002. Heart Surg Forum. 2002;4:S191.

6. Kosakai Y, Kawaguchi AT, Isobe F, et al. Modified maze procedure for patients with atrial fibrillation undergoing simultaneous open heart surgery. Circulation. 1995;92(Suppl):II359-364.

7. Murphy GJ, Ascione R, Angelini GD. Coronary artery bypass grafting on the beating heart: surgical revascularization for the next decade? Eur Heart J. 2004;25:2077–2085.

8. Gillinov AM, McCarthy PM. Atricure bipolar radiofrequency clamp for intraoperative ablation of atrial fibrillation. Ann Thorac Surg. 2002;74:2165–2168.

9. Gundry SR, Shattuck OH, Razzouk AJ, et al. Facile minimally invasive cardiac surgery via ministernotomy. Ann Thorac Surg. 1998;65:1100–1104.

Keywords:

Maze; Cardioscopy; Trans-septal approach; Atrial fibrillation

© 2005 Lippincott Williams & Wilkins, Inc.

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