Asian Cardiovasc Thorac Ann 2006;14:e24-e26
© 2006 Asia Publishing EXchange Ltd
Epicardial Pulmonary Vein Isolation Concomitant with Aortic Valve Replacement
Hidehito Endo, MD,
Hiroshi Kubota, MD,
Yutaka Hosoi, MD,
Masaya Sato, MD,
Shigeyuki Ishii, MD,
Kenichi Sudo, MD
Department of Cardiovascular Surgery, University of Kyorin, Tokyo, Japan
For reprint information contact: Hidehito Endo, MD Tel: 81 4 2247 5511 Fax: 81 4 2242 7587 Email: ehidehito{at}hotmail.com, 6-20-2, Sinkawa, Mitaka-shi, Tokyo, 181-8611, Japan.
Based on a report that paroxysmal atrial fibrillation (AF) can be triggered by ectopic beats in or close to the pulmonary vein (PV), pulmonary vein isolation has been used as a treatment for AF. We describe a technique of cryoablation for isolation of the left atrial posterior wall and the PV in a patient with AF undergoing concomitant aortic valve replacement. The patient remained in sinus rhythm at the follow-up point of 25 months.
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INTRODUCTION
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Atrial fibrillation (AF) is the most common type of sustained cardiac arrhythmia, being present in approximately 2% of the general population and in 5–9% of those aged 60 years or greater. The arrhythmia is an independent risk factor for stroke and contributes to significant patient morbidity and mortality.1 Since 1991, the Cox-Maze procedure has been used for the surgical ablation of abnormal foci that may otherwise trigger or perpetuate AF.2 This procedure is typically performed during correction of a co-existing valvular abnormality. In 1998, Haïssaguerre reported that paroxysmal AF can be triggered by an ectopic beat in or close to the pulmonary veins.3 Although pulmonary vein (PV) isolation has been used for successful ablation of areas responsible for perpetuating atrial fibrillation, the technique has some specific disadvantages that make its use problematic. The present report describes a novel approach, called ‘left atrium and pulmonary vein isolation; epicardially’ (LAVIE),4 for the rapid and safe isolation of the PV in a patient with chronic AF undergoing aortic valve replacement.
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CASE REPORT
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A 68-year-old man was diagnosed with severe aortic valve stenosis and AF of unknown duration. On admission, physical examination revealed a systemic blood pressure of 90/50 mm Hg and a heart rate of 64 beats·min–1. On auscultation, a grade III/VI systolic ejection murmur was evident at the upper left sternal border. Echocardiography revealed concentric left ventricular hypertrophy and a severely calcified bicuspid aortic valve with a peak transvalvular pressure gradient of 173 mm Hg. Left atrial diameter was 58 mm, and there was no mitral regurgitation. Electrocardiography demonstrated AF and left ventricular hypertrophy. The amplitude of the f-wave in lead V1 was 0.2 mV.
After median sternotomy, cardiopulmonary bypass was established by cannulation of the ascending aorta and both vena cavae, and the left ventricle was vented through the right superior pulmonary vein. Surgical tape was placed around the superior vena cava (SVC), the inferior vena cava (IVC) and the ascending aorta. The ascending aorta was crossclamped after the tympanic temperature reached 28°C, and myocardial protection was achieved with repetitive doses of cold blood cardioplegia in an antegrade and retrograde fashion. The severely calcified aortic leaflets were excised via aortotomy, and a 23 mm SJM prosthesis (St. Jude Medical, Inc., St. Paul, MN, USA) was implanted. Warming was discontinued when the tympanic temperature reached 31°C, and the aorta was de-clamped.
Epicardial cryoablation was subsequently initiated with N2O at -60°C (Cardiac Cryosurgical System CCS-200, Cooper Surgical, Shelton, CT, USA). When the liquid nitrogen was delivered to the cryoprobe, the temperature reached -60°C within a few seconds. Pencil- (20 x 9 mm) and T-shaped (20 x 5 mm) probes were used. The right side of the left atrium (LA) was ablated by sequential exposure and localized ablation of specific areas. These included the left atrial roof (exposed by anterior traction of the tape surrounding the SVC), the LA behind the IVC (exposed by anterior traction of the tape surrounding the IVC), and the retro-aortic portion of the left atrial roof (Figure 1-I
). Next, the left side of the left atrial roof was exposed by anterior traction of the tape surrounding the pulmonary artery, followed by passage of the cryoprobe into the transverse sinus for ablation (Figure 1-II). Finally, the inferior left atrium parallel to the retro-IVC lesion (Figure 1-III) and the left superior and inferior PV orifices were cryoablated without ligation of the left atrial appendage. Re-warming was then started.
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Figure 1. Epicardial encircling cryoablation of the left atrial posterior wall including the four pulmonary veins.
I. Cryoablation was sequentially performed after the isolation of various areas including the right side of the left atrium.
II. The retro-aortic portion of the left atrium was ablated (with ablation extending to the left side of the left atrium), and the left superior and inferior pulmonary vein orifices.
III. The inferior wall of the left atrium parallel to the coronary sinus was ablated. Ao = aorta, LA = left atrium, RA = right atrium, SVC = superior vena cava, IVC = inferior vena cava, RSPV = right superior pulmonary vein, RIPV = right inferior pulmonary vein, LSPV = left superior pulmonary vein, LIPV = left inferior pulmonary vein.
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With regards to operative and cryoablative techniques, all applications of the probe were performed epicardially with a duration of 1.5 minutes, and a continuous cryolesion was achieved by overlapping the individual ablative lesions by 2–3 mm. Aortic crossclamp time was 107 minutes, total cardiopulmonary bypass time was 197 minutes and operative time was 373 minutes. Atriotomy was not required.
The patient’s recovery was uneventful, with restoration of sinus rhythm occurring immediately after the procedure (Figure 2) without the administration of antiarrhythmic agents. Serum potassium concentration adjusted range was 4.0–4.5 mEq·liter–1. Postoperative echocardiography confirmed left atrial contraction, but showed a markedly increased ratio between early and late transmitral flow velocity peaks (1.51 meter·sec–1). On postoperative day 10, the rhythm converted to AF, which persisted despite administration of several antiarrhythmic agents. As anticoagulation therapy, 5mg of warfarin was administered from 3POD to 6POD. The dose of warfarin was controlled using international normalized ratio (INR). INR monitoring was performed daily until therapeutic range (2.0–2.5) has been achieved, thus the maintenance dose for this patient was meticulously determined. Direct current shock was not employed, and, on postoperative day 30, the patient’s rhythm spontaneously converted back to sinus rhythm. Electrocardiography at 25 months after the operation revealed normal sinus rhythm, and the patient did not require ongoing use of antiarrhythmic agents.
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Figure 2. Postoperative electrophysiological study. The patient experienced immediate postoperative restoration of sinus rhythm but experienced onset of AF on postoperative day 10. Direct current shock was not employed, and, on postoperative day 30, the patient’s rhythm spontaneously converted back to sinus rhythm. POD = postoperative day
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DISCUSSION
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Treatment of AF with the Cox-Maze procedure is dependent on the ablation of areas that transduce multiple re-entrant wavelets. While the success rate of this procedure ranges from 64–90%, postoperative complications may include attenuation of atrial natriuretic peptide secretion, decreased left atrial contraction, and inability to generate an appropriate sinus tachycardia in response to maximal exercise. Moreover, complications associated with aortic crossclamping may occur because the procedure is primarily performed in the context of concomitant valvular repair or replacement.
Recent studies suggest that AF can result from an ectopic beat with a single focal discharge or with a short burst of repetitive discharges in or close to the PV. Although endocardial radiofrequency has been used for successful isolation of the PV in the past, the success rate is modest because of incomplete ablation or concealed ectopic foci, and the technique may occasionally cause PV obstruction and cardiac tamponade. This technique also has the disadvantages of long operative time and the requirement for fluoroscopy and contrast media, which may be relatively contraindicated in patients with renal dysfunction.
The goal of the present study was to develop an ablative strategy (i.e., the LAVIE procedure) that did not possess the disadvantages of the technique described above. This procedure was based on the hypothesis that non-mitral AF originates from the PV and consists of encircling cryoablation after exposure and isolation of different components of the left atrial posterior wall and four PVs. Since Haïssaguerre stated that an ectopic beat that initiated AF is most frequently identified in the left superior pulmonary vein, cryoablation of the orifice of the pulmonary veins was also performed to isolate the ectopic focus with greater certainty.
Like any procedure, the LAVIE technique has specific advantages and disadvantages. The operative strategy is technically simple, minimizes the aortic crossclamp time, and does not require atriotomy. While it is difficult to evaluate the depth of the lesion during the procedure in the present patient, experiments in normothermic beating canine hearts demonstrated that cryoablation did not produce transmural atrial lesions. The presence of normothermic blood inside the LA may interfere with the establishment of an endocardial cryolesion. To minimize this effect, mild hypothermia was used, and the left ventricle was vented to reduce left atrial blood flow under total cardiopulmonary bypass.
The patient experienced AF from postoperative day 10 to postoperative day 30. Khargi and colleagues reported that a shortened postoperative atrial refractory time may occur because of surgical trauma and secondary edema, inflammation and elevations in circulating catecholamines.5 Daniel and colleagues reported that establishment of a stable cryolesion occurs over a period of 2–4 weeks.6 Thus, we deferred on performing electrical cardioversion until the cryolesion maturation period was complete, and we advocate a period of postoperative observation to determine whether any persistent AF will spontaneously revert to normal sinus rhythm. We conclude that the LAVIE procedure may be effective as a less invasive method of treating non-shunt and non-mitral AF. Further clinical study will be required to confirm the efficacy of this surgical procedure.
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REFERENCES
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- Romano MA, Bach DS, Pagani FD, Prager RL, Deeb GM, Bolling SF. Atrial reduction plasty Cox maze procedure: extended indications for atrial fibrillation surgery. Ann Thorac Surg 2004;77:1282–7.[Abstract/Free Full Text]
- Cox JL, Schuessler RB, D’Agostino HJ Jr, Stone CM, Chang BC, Cain ME, et al. The surgical treatment of atrial fibrillation. III. Development of a definitive surgical procedure. J Thorac Cardiovasc Surg 1991;101:569–83.[Abstract]
- Haissaguerre M, Jais P, Shah DC, Takahashi A, Hocini M, Quiniou G, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. New Engl J Med 1998;339:659–66.[Abstract/Free Full Text]
- Kubota H, Takamoto S, Morota T, Ohtsuka T, Motomura N, Kotsuka Y, et al. Epicardial pulmonary vein isolation by cryoablation as concomitant cardiac operation to treat nonvalvular atrial fibrillation. Ann Thorac Surg 2003;75:590–3.[Abstract/Free Full Text]
- Khargi K, Deneke T, Haardt H, Lemke B, Grewe P, Müller KM, et al. Saline-irrigated, cooled-tip radiofrequency ablation is an effective technique to perform the maze procedure. Ann Thorac Surg 2001; 72:S1090–5.[Abstract/Free Full Text]
- Lustgarten DL, Keane D, Ruskin J. Cryothermal ablation: mechanism of tissue injury and current experience in the treatment of tachyarrhythmias. Prog Cardiovasc Dis 1999;41:481–498.[Medline]
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INTRODUCTION
CASE REPORT
