Asian Cardiovasc Thorac Ann 2005;13:247-250
© 2005 Asia Publishing EXchange Ltd
Ablation of Atrial Fibrillation Using Microwave Energy - Early Experience
Sami S Kabbani, MD,
Ghassan Murad, MD,
Hisham Jamil, MD,
Ammar Sabbagh, MD,
Khaled Hamzeh, MD
Damascus University Cardiovascular Surgical Center, Damascus, Syria
For reprint information contact: Sami Kabbani, MD Tel: 963 11 373 8902 Fax: 963 11 373 8901 Email: dam-uncv{at}net.sy, P.O. Box: 2837, Damascus, Syria.
 |
ABSTRACT
|
|---|
Between Dec 12, 2002 and Aug 22, 2004, 84 operative patients with chronic atrial fibrillation (AF) were subjected to AF ablation with microwave energy. Of these, 49 patients were female; their ages ranged between 20 and 72 years (mean, 43.1 years). Most patients suffered from mitral disease, accompanied in over one third of cases with tricuspid insufficiency. Thirteen patients had aortic valve disease, mostly with mitral involvement. Three patients had coronary artery disease, three had atrial septal defect and one had a left atrial (LA) myxoma. Seventy-two patients underwent endocardial ablation and 12 patients underwent epicardial ablation. Operative mortality was 4 (4.8%), and there were no major untoward postoperative events. Fifty seven patients (71.3%) had their AF converted to sinus rhythm immediately after surgery. Amiodarone or sotalol was used in all postoperative patients for 6 months, except in 8 who had bradycardia. Electrical defibrillation was utilized in cases of atrial flutter or persistent AF. Seventy patients were followed for at least 6 months. In total, 52 of them (74.3%) are still in sinus rhythm. We believe microwave ablation is a satisfactory and safe method of AF ablation, and because it is brief, it can be added to surgical procedures without undue risk to the patient.
|
INTRODUCTION
|
|---|
Surgical ablation of atrial fibrillation (AF) has been gaining ground as the preferred method of treatment for this potentially lethal arrhythmia. Atrial fibrillation affects close to 1% of the general population,1 about 5% of cardiac patients over 60 years of age,2 and 1/3 to 1/2 of patients with mitral valve disease. Surgical ablation is especially suited for patients already undergoing an operative procedure (usually a mitral or coronary bypass operation).
Recent advances in understanding the mechanism of AF include the discovery that the initiation site in most AF patients is located in the pulmonary veins.3 As a result, it has been possible to reduce the classic Cox-Maze surgical incisions to simplified lesion line sets, created by one of a number of methods, including cryoablation, radiofrequency and microwave energy utilization.
In this paper we present our early experience with the use of a microwave ablation device to treat chronic atrial fibrillation, associated mainly with rheumatic mitral valve disease, still common in our part of the world.4
|
PATIENTS AND METHODS
|
|---|
Every operative patient with chronic AF (duration > 6 months), regardless of age, associated pathology or duration of AF, was subjected to microwave ablation at our center between Dec 12, 2002 and Aug 22, 2004. There were 84 patients in all, 49 of whom were female, ages ranging between 20 and 72 years (mean, 43.1 years). No patient had intermittent or paroxysmal AF. In total, 79 patients suffered from mitral valve disease, 38 with concomitant tricuspid regurgitation, 11 with concomitant aortic disease, and three with concomitant coronary artery disease. Two patients had pure aortic valve disease, 3 had atrial septal defect and one had a LA myxoma as the primary cardiac lesion. Eleven patients were in functional NYHA Class I, 34 patients in Class II, 33 patients in Class III and 6 patients in Class IV.
All patients underwent preoperative transthoracic or transesophageal echocardiography. LA size ranged between 3.4 and 17 cm (mean, 6.2 cm). Pulmonary artery pressure was estimated between 28 and 117 mm Hg (mean, 51.7 mm Hg), and left ventricular ejection fraction (LVEF) ranged between 20% and 73% (mean, 54.0%).
There was no contraindication to AF ablation related to pathology or duration of AF. Seventy-two patients underwent endocardial ablation and 12 patients underwent epicardial ablation. Ablation was performed using a microwave ablation system (AFx, Inc., Fremont, CA, USA) with a rigid antenna (Flex 2) for endocardial ablation, and a flexible antenna (Flex 4) for epicardial ablation.
All patients were operated on under cardiopulmonary bypass. Table 1
lists the operations performed. The lesion line set used for endocardial ablation encircled the pulmonary vein orifices and connected the circle to the posterior mitral annulus, as well as to the neck of the LA appendage (Figure 1). The lesion line set used for epicardial ablation followed the Maastricht outline (Figure 2).13 All patients had their LA appendage excluded or amputated as part of the operative procedure. Temporary pacemaker wires were placed in all patients prior to chest closure, and used in the intensive care unit for pacing if necessary.
The patients received amiodarone or sotalol postoperatively for 6 months. Eight patients were excluded because of bradycardia. Oral anticoagulation was prescribed for a period of 3 months after the operation, which was extended indefinitely in cases of mitral replacement with mechanical prostheses. Recurrence of AF, or the appearance of atrial flutter were treated with a combination of drug therapy and electrical cardioversion.
|
RESULTS
|
|---|
There were 4 operative fatalities in the series (for an operative mortality of 4.8%), and no major surgical complications. Five patients developed atrial flutter during the year under investigation. Two reverted on amiodarone alone and 3 required electrical cardioversion. There were two patients with temporary (first postoperative day) complete atrio-ventricular dissociation. None of the patients required pacemaker implantation. Postoperative ablation success (conversion to sinus rhythm) was established in the intensive care unit in 57 out of 80 surviving patients (71.3%). At 6 months postoperatively there were 70 patients available for study. (The rest of the patients (10) were lost to follow-up because of change of address, eight of whom had reverted to sinus rhythm immediately postoperatively). Of the 70 patients available for study at the end of 6 months 52 (74.3%) were in sinus rhythm. Atrial contraction could be confirmed echographically in 45 of these (86.8%).
The lack of success in close to 25% of patients can be attributed to extreme chronicity of AF, to a large LA, or to less-than-ideal application of the microwave probe. LA size seemed to be a factor in the failure of patients to respond to ablation, since the preoperative mean LA diameter in the 18 non-responding patients was 7.0 cm, as compared to 5.7 cm in the responding group ( p < 0.001).
|
DISCUSSION
|
|---|
The untoward effects of chronic AF are now well recognized. These include the discomfort of palpitation and congestive failure due to loss of regular rhythm and atrial transport, and most importantly, the constant threat of thromboembolism, which makes AF a potentially incapacitating and lethal condition.5 Admittedly, results from the Atrial Fibrillation Follow-up Investigation of Rhythm Management [AFFIRM] Study did not show a significant relationship between rate control combined with anticoagulation and improved functional status of patients with AF.6 However the study was only conducted for a limited duration, and does not take into account the difficulty in attaining proper anticoagulation in most countries of the world.
There are presently 3 modes of treatment for chronic AF. Medical treatment is by far the least efficacious and harbors significant morbidity. AF treatment by interventional electrophysiologic ablation has a low efficacy, is time-consuming and is accompanied by a number of potential hazards, most notorious of which is pulmonary vein stenosis.7 Surgical ablation seems at present to be the most successful and permanent mode of treatment.
While the Cox-Maze III operation is still considered the "gold standard" to which other types of surgical ablation are compared, it is a prolonged operation and not without risks.8–9 It is particularly inconvenient when added to another surgical procedure, such as mitral valve replacement. Surgical ablation has been proven to be a good alternative.10 Cryoablation, or the use of radiofrequency, microwave or ultrasound energy may not obtain the > 90% success rate reported with the surgical Maze, but results are not too far off that figure, and these techniques have the added advantages of brevity and convenience. Microwave and radiofrequency ablation have been shown to yield similar success rates,11 and at least in one study,12 radiofrequency ablation offered equivalent outcomes as the Cox-Maze III operation. Whatever the method used, surgical ablation is required to be transmural, with continuous linear lesions, and should result in no collateral extracardiac damage and preferably no charring or coagulation.
We chose microwave energy because it is safe and simple, does not result in tissue adhesion or charring, and, most importantly, has had no record of adverse effects such as esophageal perforation or coronary thrombosis. The latter complication can completely be avoided by administering cold cardioplegia during creation of lesions adjacent to the circumflex artery. Microwave energy is transmitted by the antenna into the tissues, where water molecules absorb the energy, increasing kinetic energy and elevating the tissue temperature above 50°C. Permanent, linear and transmural lesions can thus be created. The lesion size is controlled by setting power and ablation time, and both have to be increased when creating epicardial (as compared to endocardial) lesions.
Since it has been shown that AF is triggered from the pulmonary veins and posterior left atrium in over 90% of cases, for our lesion set we have chosen a simplified "box-type" lesion around the pulmonary veins, connected to the posterior mitral annulus and atrial appendage (Figure 1
). The atrial appendage, of course, has to be excluded or amputated in all cases. With epicardial lesion sets we have followed the ‘butterfly’ pattern recommended by the University of Maastricht (Figure 2).13
Our results have been satisfactory and compare favorably with those of other investigators.13,14 Further follow-up is needed to establish the ideal lesion sets for every category of AF patients. Further work is also needed to assess the benefits of epicardial, as compared to endocardial ablation,13 and the role of endoscopic approaches to microwave ablation of AF.15
|
REFERENCES
|
|---|
- Kannel WB, Abbott RD, Savage DD, McNamara PM. Epidemiologic features of chronic atrial fibrillation: the Framingham study. N Engl J Med 1982;306:1018–22.[Abstract]
- Kannel WB, Abbott RD, Savage DD, McNamara PM. Coronary heart disease and atrial fibrillation: the Framingham study. Am Heart J 1983;106:389–96.[Medline]
- Haissaguerre M, Shoda M, Jais P, Nogami A, Shah DC, Kautzner J, et al. Mapping and ablation of idiopathic ventricular fibrillation. Circulation 2002;106:962–7.[Abstract/Free Full Text]
- Steer AC, Carapetis JR, Nolan TM, Shann F. Systematic review of rheumatic heart disease prevalence in children in developing countries: the role of environmental factors. J Paediatr Child Health 2002;38:229–234.[Medline]
- Wolf PA, Abbott RD, Kannel WB. Atrial fibrillation: a major contributor to stroke in the elderly. The Framingham Study. Arch Intern Med 1987;147:1561–4.[Abstract/Free Full Text]
- Cooper HA, Bloomfield DA, Bush DE, Katcher MS, Rawlins M, Sacco JD, et al; AFFIRM Investigators. Relation between achieved heart rate and outcomes in patients with atrial fibrillation (from the Atrial Fibrillation Follow-up Investigation of Rhythm Management [AFFIRM] Study). Am J Cardiol 2004;93:1247–53.[Medline]
- Purerfellner H, Aichinger J, Martinek M, Nesser HJ, Cihal R, Gschwendtner M, et al. Incidence, management, and outcome in significant pulmonary vein stenosis complicating ablation for atrial fibrillation. Am J Cardiol 2004;93:1428–31.[Medline]
- 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;110:485–95.[Abstract/Free Full Text]
- Bando K, Kobayashi J, Kosakai Y, Hirata M, Sasako Y, Nakatani S, et al. Impact of Cox maze procedure on outcome in patients with atrial fibrillation and mitral valve disease. J Thorac Cardiovasc Surg 2002;124:575–83.[Abstract/Free Full Text]
- Sie HT, Buekema WP, Ramdat Misier AR, Elvan A, Ennema JJ, Wellens HJ. The radiofrequency modified maze procedure. A less invasive surgical approach to atrial fibrillation during open-heart surgery. Eur J Cardiothorac Surg 2001;19:443–7.[Abstract/Free Full Text]
- Wisser W, Khazen C, Deviatko E, Stix G, Binder T, Seitelberger R, et al. Microwave and radiofrequency ablation yield similar success rates for treatment of chronic atrial fibrillation. Eur J Cardiothorac Surg 2004;25:1011–7.[Abstract/Free Full Text]
- Chiappini B, Martin-Suarez S, LoForte A, Arpesella G, Di Bartolomeo R, Marinelli G. Cox/Maze III operation versus radiofrequency ablation for the surgical treatment of atrial fibrillation: a comparative study. Ann Thorac Surg 2004;77:87–92.[Abstract/Free Full Text]
- Maessen JG, Nijs JF, Smeets JL, Vainer J, Mochtar B. Beating-heart surgical treatment of atrial fibrillation with microwave ablation. Ann Thorac Surg 2002;74:S1307–11.[Abstract/Free Full Text]
- Schuetz A, Schulze CJ, Sarvanakis KK, Mair H, Plazer H, Kilger E, et al. Surgical treatment of permanent atrial fibrillation using microwave energy ablation: a prospective randomized clinical trial. Eur J Cardiothorac Surg 2003;24:475–80.[Abstract/Free Full Text]
- Saltman AE, Rosenthal LS, Francalancia NA, Lahey SJ. A completely endoscopic approach to microwave ablation for atrial fibrillation. Heart Surg Forum 2003;6:E38–41.[Medline]
This article has been cited by other articles:
|
|
|
|
 
S. Kabbani, H. Jamil, F. Nabhani, A. Hamoud, K. Katan, N. Sabbagh, A. Koudsi, L. Kabbani, and G. Hamed
Analysis of 92 mitral pulmonary autograft replacement (Ross II) operations.
J. Thorac. Cardiovasc. Surg.,
October 1, 2007;
134(4):
902 - 908.e7.
[Abstract]
[Full Text]
[PDF]
|
|
|
TOP
ABSTRACT
INTRODUCTION
