Mid-Term Results of Intraoperative Radiofrequency Ablation

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1 Kitakanto Med J ; 53 : 37 `41 Mid-Term Results of Intraoperative Radiofrequency Ablation A new approach to atrial fibrillation Susumu Ishikawa,1 Jai S. Raman,1 Brian F. Buxton1 and Yasuo Morishita 2 Purpose : Mid-term results of intraoperative radiofrequency ablation (RFA) procedure for the treatment of atrial fibrillation (AF) were evaluated. Methods : A total of 87 patients were followed up for longer than three months after RFA. The mean age of them was 67 } 11 years old, including 61 males and 26 females. Preoperatively 64 patients were in persistent AF, 21 had paroxysmal AF and two had atrial flutter. Fifty-eight patients underwent mitral valve repair/replacement concomitantly, including combined CABG or aortic valve replacement (AVR). CABG, AVR and CABG + AVR procedures were performed in 13, five and three patients, respectively. The left atrial RFA lesions were created endocardially in patients with mitral procedures, while epicardially created in patients with AVR/CABG. The right atrial epicardial lesions were common to both groups of patients. The mean follow-up period was 6.3 months ranging from three to 24. Results : No heart muscle or esophageal perforation occurred after RFA. The recovery rate to regular sinus rhythm at the time of three, six and 12 months after surgery was 83%, 88% and 93%, respectively. Conclusions : Mid-term results of RFA suggest that it is safe and effective in the treatment of AF, especially in patients without mitral valve disease. (Kitakanto Med J 2003 ; 53 : 37 `41) Key Words : atrial fibrillation, radiofrequency ablation, cardiac surgery Introduction Intraoperative radiofrequency ablation (RFA) treatments were commenced in late 1990s and majority of these techniques have been adopted in conjunction with mitral valve procedures and modified maze procedures.1,2 These procedures were mainly aimed to reduce the prolonged operative time and increased morbidity in maze procedures. RFA treatment has been already used in the field of catheter treatment, and selective ablation of ectopic electrical foci has been effective in the treatment of focal AF3 and other supraventricular tachycardias.4 Intraoperative RFA treatment for AF was started as a multicentre study in Australia and New Zealand in March We have used combined endocardial and epicardial RFA of both atria in patients both with and without mitral valve disease. We have already mentioned the details of our procedures and favorable initial results.5 In this report, the mid-term results were evaluated and the possible developments of this procedure in the future were discussed. Patients and methods A total of 139 patients underwent the intraoperative RFA procedure for the treatment of AF between March 2000 and March 2002 at 20 hospitals across Australia and New Zealand. Mid-term results, longer than three months, were studied in 87 patients of 15 hospitals. The mean age of these patients at the time of operation was 67 } 11 years old ranging from 35 to 81. They included 61 males and 26 females. Sixtyfour (74%) patients were in persistent AF, 21 (24%) had paroxysmal AF and two (2 %) had atrial flutter at the time of operation. The mean duration of preoperative rhythm disturbance was 36 months ranging from 1 to 120. As primary surgical procedures, 46 patients underwent solitary mitral valve repair/replacement, six underwent a combination of mitral valve procedure and aortic valve replacement (AVR), and six underwent mitral valve procedure plus coronary artery bypass grafting (CABG). Thirteen patients underwent 1 Department of Cardiac Surgery, Austin & Repatriation Medical Centre, University of Melbourne, MelbourneAustralia 2 Second Department of Surgery, Gunma University Faculty of Medicine, Maebashi, Japan Received : November 8, 2002 Address : SUSUMU ISHIKAWA Second Department of Surgery, Gunma University Faculty of Medicine, Showa-machi, Maebashi, Gunma , Japan

2 38 Radiofrequency Ablation for Atrial Fibrillation Fig 1 Lesion set on the left atruim Lesions was decided according to modified radial & bilateral isolation of pulmonary veins.6'7 Table 1 Patient Demographics CABG, five underwent AVR, three underwent CABG AVR, and residual eight underwent other combined procedures (Table 1). Patients were followed up after surgery with a clinical examination, echocardiogram, and a Holier monitor. The mean follow-up period after surgery was 6.3±4.5 months ranging from three to 24. Fifty patients have been followed up for longer than 6 months after RFA and 15 have undergone a 12 months' follow-up study. As an anti-arrhythmic medication, low-dose amiodarone (200 mg/day) was recommended up to 6 months after surgery. RFA was used on both endocardial and epicardial lesions by a malleable RFA catheter with seven electrodes (Cobra Boston Scientific, San Jose, CA) according to the modified radial and bilateral isolation of pulmonary veins.6,7 The surgical technique of RFA varied depending on whether the left atrium was opened (Figure 1). In patients with mitral procedures, left-sided lesions were approached via left atrial opening and RFA burn was created on the endocardial lesion of an arrested heart under cardiopulmonary bypass (CPB). While, in patients with aortic valve procedures or CABG, the approach of RFA catheter was predominantly epicardial. The left atrial appendage was opened and evacuated. The appendage was ligated at its base. In total, 66 patients of this followup study underwent endocardial ablation and another 21 underwent epicardial procedure. The right atrial lesions were common to both groups of patients, and usually created epicardially on the surface of the right atrium with the heart beating and ejecting on CPB (Figure 2). All lesions were created using radiofrequency energy delivered by a handheld versatile Cobra probe at a minimum temperature of 80 C to 85 C for the period of 2 minutes. The aortic cross-clamp

3 39 Mitral, Aortic Valves, CABG 1) Between SVC and IVC (along crista terminalis) 2) Connecting lesion up to AV groove affecting cawtricuspid junction Fig 2 Lesion set on the right atrium Lesion was common to all patients and ablation was performed with the heart beating Table 2 Follow-up results period prolonged by RFA was about 15 to 25 minutes. Values are expressed as the mean }standard deviation. The x2-test and Students' T-test were used for a statistical analysis with Stat-View R (SAS Institute Inc.). A p value of less than 0.05 was considered to be significant. Results All 87 patients were weaned from CPB in a regular paced rhythm or sinus rhythm. No heart muscle perforation and esophageal perforation occurred after RFA. Ten patients required defibrillation within three months postoperatively, and nine of ten patients have still remained in sinus rhythm. Permanent pacemaker (PPM) implantation was required in five patients of endocardial RFA with mitral valve disease. Four of them received PPM implantation during the early phase of surgery due to sinus or junctional bradycardia, and another one underwent PPM implantation seven months after atrio-ventricular node catheter ablation due to sustained supraventricular tachycardia. Atrial flutter occurred in two patients. The recovery rate to regular sinus rhythm in total patients at three, six and 12 months after surgery was 83%, 88% and 93%, respectively (Figure 3). These results were compared between 66 patients who had undergone endocardial RFA and 21 patients of the epicardial RFA procedure (Table 2). Three months after surgery, 82% of patients with endocardioal RFA and 86% of patients with epicardial RFA

4 40 Radiofrequency Ablation for Atrial Fibrillation Fig 3 Postoperative Rhythm Sinus recovery rate was 83%, 88%, 93% at the time of three, six and 12 months after surgery. pacemaker was implanted stayed in regular sinus rhythm. Six months after surgery, 87% of patients with endocardioal RFA remained in regular sinus rhythm and 91% of patients with epicardial RFA stayed in regular sinus rhythm. The preoperative left atrial diameter was significantly (p ƒ0.05) larger in patients with endocardial RFA than those with epiacrdial RFA, however, there was no significant difference after surgery. There were no significant correlation between the preoperative left atrial diameter and the postoperative sinus recovery rate. Postoperative echocardiography showed reasonable atrial contraction in both groups of patients in sinus rhythm. The transmitral peak early filling velocity was high in the endocardial ablation group probably due to the effect of artificial valves. Discussion in five patients. The permanent Favorable results after maze procedure and its modifications have been reported8 and are also important in the follow-up study when we evaluate results after surgical procedures. Considering that rhythm changes are frequent during the early phase after surgery, results should be evaluated at six months or over than one year after surgery. Sinus recovery rates after the maze procedure and its modifications were favorable, reported to be 92-99%940 at the time of six months and 80-92% at one year.9,11,12 Intraoperative radiofrequency treatments were commenced in late 1990s and the majority of these techniques have been used as a part of modified maze procedures. A sinus recovery rate of these procedures was 89-92% six months after surgery.1,2 The solitary intraoperative radiofrequency treatments for AF were recently started and the procedures have not been established. In this study the recovery rate to regular sinus rhythm at three, six and 12 months after surgery was 83%, 88% and 93%, respectively. Our results are acceptable because a sinus recovery rate after solitary radiofrequency treatments was reported to be 81% to 91% six to 13 months after surgery.13,14 Surgical treatments for AF patients without mitral valve disease have not been established. We adopted the epicardial RFA procedure on the left atrium in patients with aortic valve disease and ischemic heart diseases, and a sinus recovery rate was 91% six months after surgery. Benussi and colleagues15 recently showed that similar results could be achieved by creating epicardial lesions around the pulmonary veins in patients with mitral valve diseases. Melo and associates16 also showed epicardial lesions in "off-pump" procedures to be reasonably effective. Favorable results of the maze procedure and its modifications for loan AF have been recently reported.12 However, it is still controversial whether these procedures are suitable for patients without mitral valve disease because of an attendant increase of operative time and morbidity. In our study, we used the RFA procedure in conjunction with the treatment of underlining cardiac diseases. Radiofrequency energy is relatively quick to perform and creates lesions in the myocardium without disadvantage of making multiple incisions, thus, further extension of this procedure to the treatment of loan AF should be required. Despite the favorable sinus recovery rate after the maze and RFA procedures, postoperative recovery of atrial transportation function is still controvertial. Echocardiography is usually used for the evaluation of atrial function nevertheless to quantitate atrial function is sometimes difficult because diastolic function of the ventricle is influenced patients' age, underlining heart disease' and operative procedure. After maze III procedure for patients with paroxysmal atrial fibrillation, there was a progressive increase in the transmitral early filling/atrial filling wave ratio after surgery, consistent with a gradual decrease in left atrial transport function.18 However, improvements of atrial transport function have been reported in the so-called mini-maze procedure.9 Isobe and colleagues" reported the bilateral appendage-preserving procedure improved atrial transport and atrial natriuretic peptide secretion without decreasing its effectiveness against atrial fibrillation. Lee and colleagues" also reported the efficacy of a modification of the maze procedure using linear cryoablation. In an animal study, Thomas and colleagues20 mention that multiple linear radiofrequency lesions in the atria might impair atrial contractility. In our study, a postoperative echocardiogram showed reasonable peak atrial velocity. therefore, we believe the advantages of recovery to sinus rhythm after RFA treatment are enough to

5 41 overcome this problem. In conclusion, mid-term results of RFA suggest that it is safe and effective in the treatment of AF, especially in patients without mitral valve disease. References 1. Sic HT, Beukema WP, Misier ARA, et al. The radiofrequency modified maze procedure. A less invasive surgical approach to atrial fibrillation during open-heart surgery. Eur J Cardiothorac Surg 2001 ; 19 : Pasic M, Bergs P, Muller P, et al. Intraoperative radiofrequency maze ablation for atrial fibrillation : The Berlin modification. Ann Thorac Surg 2001 ; 72 : Haissaguerre M, Jais P, Shah DC, et al. Right and left atrial radiofrequency catheter therapy of paroxysmal atrial fibrillation. J Cardiovasc Electrophysiol 1996 ; 7: Jackman WM, Beckman KJ, McClelland JH, et al. Treatment of supraventricular tachycardia due to atrioventricular nodal reentry, by radiofrequency catheter ablation of slow-pathway conduction. N Engl J Med 1992 ; 327 : Raman JS, Seevanayagam S, Storer M, et al. Combined endocardial and epicardial radiofrequency ablation of right and left atria in treatment of atrial fibrillation. Ann Thorac Surg 2001 ; 72 : S Nitta T, Lee R, Schuessler RB, et al. Radial approach : a new concept in surgical treatment for atrial fibrillation. I. Concept, anatomic and physiologic bases and development of a procedure. Ann Thorac Surg 1999 ; 67 : Melo JQ, Adragao P, Neves J, et al. Surgery for atrial fibrillation using radiofrequency catheter ablation : Assessment of results at one year. Eur J Cardiothorac Suig 1999 ; 15 : Cox JL, Schuessler RB, Lappas DG, et al. An 8 clinical experience with surgery for atrial fibrillation. Ann Surg 1996 ; 224 : Bauer EP, Szalay ZA, Brandt RR, et al. Predictors for atrial transport function after mini-maze operation. Ann Thorac Surg 2001 ; 72 : Lee JW, Choo SJ, Kim KI, et al. Atrial fibrillation surgery simplified with cryoablation to improve left atrial function. Ann Thorac Surg 2001 ; 72 : Sueda T, Nagata H, Shikata H, et al. Simple left atrial procedure for chronic atrial fibrillation associated with mitral valve disease. Ann Thorac Surg 1996 ; 62 : Jessurun ER, Hemel NM, Defauw JAMT, et al. Results of maze surgery for lone paroxysmal atrial fibrillation. Circulation 2000 ; 101 : Williams MR, Stewart JR, Bolling SF, et al. Surgical treatment of atrial fibrillation using radiofrequency energy. Ann Thorac Surg 2001 ; Alfieri O, Benussi S. Mitral valve surgery with concomitant treatment of atrial fibrillation. Cardiol Rev 2000 ; 8 : Benussi S, Pappone C, Nascimbene S, et al. A simple way to treat chronic atrial fibrillation during mitral valve surgery : The epicardial radiofrequency approach. Eur J Cardiothorac Surg 2000 ; 17 : Melo JQ, Adragao P, Neves J, et al. Endocardial and epicardial radiofrequency in the treatment of atrial fibrillation with a new intraoperative device. Eur J Cardiothorac Surg 2000 ; 18 : Otto CM. Echographic evaluation of ventricular diastolic filling and function. In Textbook of Clinical Echocardiolography. 2nd ed. Philadelphia, WB Saunders, 2000 : Lonnerholm S, Blomstrom P, Nilsson L, et al. Atrial size and transport function after the maze III procedure for paroxysmal atrial fibrillation. Ann Thorac Surg 2002 ; 73 : Isobe F, Kumano H, Ishikawa T, et al. A new procedure for chronic atrial fibrillation : Bilateral appendage-preserving maze procedure. Ann Thorac Surg 2001 ; 72 : Thomas SP, Nicholson IA, Nunn GR, et al. Effect of atrial radiofrequency ablation designed to cure atrial fibrillation on atrial mechanical function. J Cardiovasc Electrophysiol 2000 ; 11 :