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Ann Thorac Surg 2003;75:590-593
© 2003 The Society of Thoracic Surgeons
a Department of Cardiovascular Surgery, University of Kyorin, Tokyo, Japan
b Department of Cardiothoracic Surgery, University of Tokyo, Tokyo, Japan
Accepted for publication August 8, 2002.
* Address reprint requests to Dr Kubota, 6-20-2, Shinkawa, Mitaka-shi, Tokyo 181-8611, Japan
e-mail: kub{at}kuorin-u.ac.jp
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Introduction |
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On March 29, 2001, an 82-year-old woman was transferred to our hospital with a diagnosis of acute aortic dissection, DeBakey II, Stanford A. Preoperative echocardiography revealed normal cardiac function, and aortic regurgitation was trivial.
The diameter of the left ventricle was 35 mm in diastole, and 19 mm in systole. There was no mitral regurgitation and no enlargement of the left atrium. A preoperative electrocardiogram showed AF, and the amplitude of the f-wave in V1 was 0.1 mV. The patient’s AF had initially been diagnosed about 3 years previously. An operation was performed on the day after admission.
The pericardium was opened through a median sternotomy. A mild bloody pericardial effusion was aspirated, and tapes were passed around the superior vena cava (SVC) and the inferior vena cava (IVC). A cardiopulmonary bypass was established by cannulations through the left femoral artery and both vena cavae, and the left ventricle was vented through the right superior pulmonary vein. During cooling, the tissue behind the SVC and IVC was carefully dissected to expose the left atrium. When the tympanic temperature reached 20°C, both vena cavae were snared, and epicardial cryoablation was started with N2O at -60 °C (Cardiac Cryosurgical System CCS-200; Cooper Surgical, Shelton, CT). A pencil-type probe (20 mm x 9 mm) and a T-shaped probe (20 mm x 5 mm) were used.
The right side of the left atrium was cryoablated first. The roof of the left atrium behind the SVC was then ablated by pulling the snared tape anteriorly, and the left atrium behind the IVC was ablated pulling the snared tape anteriorly (Fig 1A).
At a tympanic temperature of 18°C, the ascending aorta was incised under circulatory arrest and retrograde cerebral perfusion. Antegrade blood cardioplegia was infused. After folding in the aortic adventitia to reinforce the aorta at the intended site of anastomosis, a 26-mm woven Dacron graft (Hemashield®, Boston Scientific Medi–Tech, Wayne, NJ) was anastomosed to it. The graft was clamped, and the antegrade perfusion was started through a side branch of the graft. The retro-aortic portion of the left atrial roof was easily cryoablated because the proximal ascending aorta was left transected. Reinforcement of the proximal aorta and an anastomosis were carried out. The cryoablation of the remaining part of the left atrium was continued while warming. A tape was passed around the pulmonary artery, and as the tape was pulled anteriorly, the cryoprobe was passed into the transverse sinus, thereby enabling ablation of the left side of the roof of the left atrium. Great care was taken not to ablate the left coronary artery system to prevent reactive hypertrophy of the intima, which might cause serious ischemia of the myocardium. The ablation was extended to the left side of the left atrium, the inferior wall of the left atrium parallel to the coronary sinus, and was finally connected to the retro-IVC lesion that had been made before circulatory arrest (Fig 1B, C). The left atrial appendage was ligated, and the orifices of the left superior and inferior pulmonary vein were cryoablated (Fig 1D). All applications of the probe were epicardial, and the cryolesions were always created so that they overlapped by 2
3 mm to produce a continuous lesion. The duration of each application was 1.5 minutes.
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The patient was extubated the next day and returned to a general ward on postoperative day 2.
The postoperative electrophysiological examination revealed that overdrive pacing inside of the encircling lesion with a bipolar pacing wire left behind the left atrium did not affect the cardiac rhythm, even when the output was set at maximum (Fig 2). The atrial electrical potential within the encircling lesion was recorded with the same pacing wire, and no atrial potential was found within the encircling lesion. A Holter electrocardiogram recorded 4 months after the operation showed a regular sinus rhythm without any supraventricular tachycardia. An electrocardiogram 16 months after the operation showed that the regular sinus rhythm had been maintained without drugs. Postoperative echocardiography confirmed left atrial contraction, but showed a markedly increased ratio between early and late (E/A) transmitral flow velocity peaks (E: early peak velocity, 0.55 meter/second, A: late peak velocity, 0.18 meter/second).
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It has recently been shown that a rapidly firing focus in or close to the pulmonary veins could be the cause of AF, and node-like cells have been demonstrated in the myocardium that encircle the pulmonary veins of the rat [3]. Blom and colleagues [4] used Human Natural Killer and killer cell (HNK–1) immunohistochemistry to trace the development of the cardiac conduction system in the human embryo and discovered HNK-1 antigen is transiently expressed in the myocardium around the pulmonary vein. These findings led to the use of radiofrequency catheter ablation of such foci as a means of treating AF [5]. However, it is a time consuming procedure with possible complications, such as thromboembolism, pulmonary vein stenosis, cardiac tamponade, and it requires fluoroscopy and contrast medium. To overcome these problems, we developed the technique previously described and called it the "LAVIE" (left atrium and vein isolation: epicardial) procedure. In the previously presented case we were unable to find any cardiac disease except the ascending aortic dissection. Although a preoperative electrophysiological study was not performed, in view of the patient’s advanced age and echocardiographic findings her AF was thought to be lone AF, very probably of the pulmonary vein origin. The postoperative electrophysiological study showed that the encircling pulmonary vein lesion had produced a bi-directional block. The posterior wall of the left atrium, including the pulmonary veins, had been electrically isolated. Because the report of Haïssaguerre and colleagues [1] stated that the ectopic foci are most frequently identified in the left superior pulmonary vein, we added the cryoablation of the orifice of the left pulmonary veins to isolate the ectopic focus with greater certainty. In this case, the left atrial roof was cryoablated easily because the proximal ascending aorta was left transected. In nonopen cardiac operation, such as coronary bypass procedures, the entire length of the left atrial roof can also be ablated by pulling up a tape passed around the ascending aorta and the pulmonary trunk through the transverse sinus.
The postoperative echocardiogram revealed a markedly increased E/A ratio as a result of decreased transmitral A flow velocity, a phenomenon suggesting that the isolated left atrium does not participate in the atrial contraction.
The left atrium and vein isolation technique does not require atriotomy and does not prolong the aortic cross-clamp time. Since two cryoprobes can be used simultaneously, total ablation time can be shortened. Both vena cavae were snared to reduce blood flow in the left atrium. Reducing the blood flow, which weakens the cryo effect, is quite important to producing transmural cryolesions. The left ventricular venting is also effective to reduce the blood in the left atrium. The deep hypothermia in our patient was also thought to have contributed greatly to augmentation of the effect of the cryoablation. As the temperature decreases, the efficacy of the cryoablation increases. In another series of experiments in normothermic beating canine hearts, we found that cryoablation did not produce atrial transmural lesions [6]. Our technique should be applied only during cardiac operations performed under hypothermic conditions with total cardiopulmonary bypass. Although the most suitable temperature for creating transmural lesions is unknown, this concomitant procedure enables the treatment of nonvalvular AF without prolonging aortic cross-clamp time.
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