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Ann Thorac Surg 2005;79:480-484
© 2005 The Society of Thoracic Surgeons

Original article: Cardiovascular

Combining Robotic Mitral Valve Repair and Microwave Atrial Fibrillation Ablation: Techniques and Initial Results

Clifton C. Reade, MD, James O. Johnson, MD, Gil Bolotin, MD, William L. Freund, Jr, MD, Nelson L. Jenkins, MD, Curtis E. Bower, MD, Saqib Masroor, MD, Alan P. Kypson, MD, L. Wiley Nifong, MD, W. Randolph Chitwood, Jr, MD, FACS*

Division of Cardiothoracic and Vascular Surgery, The Brody School of Medicine at East Carolina University, Greenville, North Carolina

Accepted for publication July 29, 2004.

* Address reprint requests to Dr Chitwood, Department of Surgery, The Brody School of Medicine at East Carolina University, 600 Moye Blvd, Greenville, NC 27858 (E-mail: chitwoodw{at}mail.ecu.edu).

Presented at the Video Session of the Fiftieth Annual Meeting of the Southern Thoracic Surgical Association, Bonita Springs, FL, Nov 13–15, 2003.


   Abstract
Top
 Abstract
Introduction
 Material and Methods
 Results
 Comment
 References
 
BACKGROUND: Left atrial microwave ablation for atrial fibrillation has become popular for isolating autonomous atrial foci. Previously, mitral valve repairs (MVP) with atrial fibrillation ablation have been performed through sternotomy. We present a technique that combines robotic MVP with left atrial fibrillation ablation.

METHODS: Through a 4-cm right minithoracotomy and using cardiopulmonary bypass, the transverse and oblique sinuses are accessed. A Flex-10 microwave catheter is passed around the pulmonary veins, and after weaning from cardiopulmonary bypass, peripulmonary vein microwave ablations are performed. After cardioplegic arrest, the da Vinci system is used to manipulate the catheter to create endocardial lesions around the left atrial appendage. Another endocardial lesion is made connecting the pulmonary venous line with the mitral annulus near P3. The left atrial appendage is closed, and the MVP performed robotically. Data are expressed as mean ± standard deviation.

RESULTS: Sixteen patients underwent this combined procedure, with 80% returning to a normal sinus rhythm at 6 weeks and 73% remaining in normal sinus rhythm at 6 months. Only 1 patient was in atrial fibrillation at 6 months. The ablation procedure added 42 ± 16.1 minutes to a robotic MVP. The average length of hospital stay was 6.3 ± 2.2 days, 1.3 days longer than the mean of the prior 50 consecutive robotic MVP patients without a concomitant ablation.

CONCLUSIONS: Robotic microwave ablation during robotic MVP is a safe, effective way to resolve atrial fibrillation. These methods offer a promising prelude to the combined totally endoscopic treatment of atrial arrhythmias and mitral insufficiency.


   Introduction
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 Abstract
 Introduction
Material and Methods
 Results
 Comment
 References
 
Atrial fibrillation (AF) is a debilitating problem that affects 5% of the population older than 65 years and is a major cause of stroke [1]. Medical therapy is the first choice of care for these patients, but a significant proportion are refractory to both pharmacologic and cardioversion therapy, with less than 30% free from AF at 4 years [2]. In addition, patients who remain in AF after mitral valve surgery have nearly a 20% higher mortality at 5 years than patients in normal sinus rhythm [3]. Searching for permanent treatment options, Cox and associates [4, 5] in the late 1980s defined pathways associated with automatic atrial foci, and developed the initial Maze procedure to contain AF by means of surgical incisions. Even though the Maze operation provides excellent results (up to 99% success with the Maze-III) [6], the procedure has not been accepted widely because of complexity and bleeding risks.

In 1998 Haissaguerre and colleagues [7] determined that 94% of patients in refractory AF had automatic foci originating in pulmonary vein orifices. As a result of this work, researchers investigated radiofrequency and cryoablative lesions to encircle areas containing automatic foci and prevent propagation throughout the atrium [8, 9].

With the advent of flexible microwave energy devices, a new energy source with a more direct method of lesion placement became available [10]. These catheters allow surgeons to create epicardial lesions, both on and off cardiopulmonary bypass (CPB), as well as intracardiac endocardial ones. Thus far, studies using microwave catheters by means of median sternotomy during concomitant procedures have no long-term results [11, 12].

Fifty percent of patients requiring mitral valve surgery also have AF [13], and surgeons now are offering combined procedures to treat both pathologic processes. An ablative procedure combined with mitral valve surgery and minimal arrested heart time is ideal. Robotically directed ablations could increase lesion set placement precision because of enhanced visualization and advanced telemanipulation [14, 15].


   Material and Methods
Top
 Abstract
 Introduction
 Material and Methods
Results
 Comment
 References
 
Patients referred for mitral valve insufficiency with AF and no coronary disease were considered for the procedure. All patients were given full details of the operation as well as alternatives by hospital informed consent standards, and all patients consented to treatment. Preoperative echocardiography was reviewed, and the length of time in AF was documented. Our robotic operative setup, patient positioning, exposure, cannulation, and perfusion have been described previously [15].

After cannulation, CPB was initiated at normothermia to empty the heart, allowing easier dissection of the interatrial groove, transverse sinus, and oblique sinus. A 5-mm endoscope inserted through the minithoracotomy assisted with the epicardial dissection. Pericardial reflections behind the superior vena cava were dissected free to expose the transverse sinus followed by inferior vena caval dissection to expose the oblique sinus. Finally, the overlying fat pad along the interatrial groove was dissected with electrocautery. The Flex-10 (AFX Inc, Fremont, CA) catheter was passed through the transverse sinus, around the left pulmonary veins, and then retrieved through the oblique sinus (Fig 1). The catheter was then looped again under the superior vena cava to create a snare for tight catheter approximation against all four epicardial pulmonary veins. The endoscope was used to confirm that the catheter passed above the left atrial appendage and away from the circumflex coronary artery. Patients were weaned from CPB, and 90-second epicardial lesions were created on the beating heart at 65 W. After completion of this initial lesion set, CPB was reinstituted, and the heart was arrested using antegrade cold blood cardioplegia and a transthoracic clamp (Scanlan, Minneapolis, MN). The mitral valve was exposed through a small left atriotomy using a transthoracic retractor (Cardiovations, Somerville, NJ). The robotic arms were placed in the third and fifth intercostal spaces, and the da Vinci instrument cart (Intuitive Surgical, Sunnyvale, CA) was moved into the tableside position.



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  		Fig 1. Lesion placement set. From left to right: catheter placement, lesion created, intraoperative view. (A) Epicardial encircling pulmonary vein box performed off bypass. (B) Endocardial left atrial appendage encircling lesion performed robotically. (C) Endocardial connection lesion between the pulmonary vein box lesion and the mitral valve annulus performed robotically.

 
All endocardial lesions were performed using robotic telemanipulation. The first lesion encircled the left atrial appendage (LAA), and was followed by LAA closure using a 3-0 Prolene (Ethicon, Somerville, NJ) pursestring suture. Next, endocardial connecting lesions were created (1) between the LAA lesion and the endocardial surface of the epicardial encircling pulmonary vein lesion and (2) from the epicardial lesion region, on the endocardium near the right inferior pulmonary vein, to the mitral annulus near P3 (Fig 1). Early in the series, the endocardial lesions were created with the Flex-4 (AFX Inc) device (n = 3); however, by the fourth patient we were using the Flex-10 (AFX Inc) device because of easier manipulation and a longer catheter. The assistant surgeon passed the Flex-10 catheter through the minithoracotomy, and the console surgeon conformed the catheter robotically to create the desired lesion sets. Endocardial lesions were performed at 65 W for 45 seconds.

After completion of endocardial lesions, a robotic mitral valve repair (MVP) was performed as reported previously [15]. With completion of the repair, the atrium was closed, and the patient was weaned from CPB. Transesophageal echocardiography was performed to evaluate valve function and regional ventricular wall motion. Amiodarone (150 mg bolus followed by 1 mg/min continuous infusion) was initiated postoperatively and converted to oral administration when tolerated. Patients were anticoagulated before discharge and maintained on both warfarin sodium (Coumadin) and amiodarone for 2 months. Follow-up was complete and was conducted by means of telephone interviews with patients and physicians.


   Results
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 Abstract
 Introduction
 Material and Methods
 Results
Comment
 References
 
Between January 2003 and September 2003, 16 patients underwent a combined robotic MVP and AF ablation procedure. Demographic data are presented in Table 1.


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  		Table 1. Preoperative Data
 
Intraoperative data (Table 2) reflect mean cross-clamp and total CPB times as 133 ± 30.0 minutes and 174 ± 40.8 minutes, respectively. Combined times required to perform both the epicardial dissection and catheter placement averaged 13.2 ± 9.4 minutes, whereas epicardial lesion placement times averaged 18.9 ± 5.5 minutes. Intracardiac (endocardial) ablation times averaged 12.3 ± 5.3 minutes, and time to close the LAA averaged 7.1 ± 2.7 minutes. Mitral valve repair (including valve resection, repair, and annuloplasty) required 61.4 ± 24.5 minutes, with a total operating time of 5.4 ± 1.4 hours.


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  		Table 2. Intraoperative and Postoperative Data
 
Postoperatively, patients remained intubated for 9.1 ± 3.2 hours and in the intensive care unit for 1.2 ± 0.4 days (Table 2). Average chest tube drainage was 628 ± 439 mL. Patients received an average of 1.6 ± 4.2 of packed red blood cells and 0.7 ± 1.6 U of either fresh-frozen plasma or platelets. Eleven patients (69%) received no blood products, and hospital length of stay for the series was 6.3 ± 2.2 days.

Only one ablation-related complication developed. After arrival in the intensive care unit a patient experienced ventricular arrhythmias and ST depression. Coronary angiography showed partial left circumflex artery occlusion with thrombus in the atrioventricular groove and just below the LAA. Immediate stenting corrected this thermally related complication. One patient died on postoperative day 43, after a prolonged hospitalization, as a result of respiratory distress and a bowel infarction. As this patient was more than four standard deviations from the mean for ventilation time, intensive care unit stay, and length of stay, these data were not included in the mean calculations. However, the patient was in sinus rhythm postoperatively.

Immediately after surgery, 7 patients (47%) were in normal sinus rhythm, 6 patients (40%) were either paced or in a junctional rhythm, and 2 patients (7.1%) remained in AF (Fig 2). On postoperative day 2 the incidence of AF peaked in 4 patients (29%) but by day 3, 2 patients (14%) had reverted to normal sinus rhythm. After postoperative day 3, patients maintained the same rhythm with 10 (67%) in normal sinus rhythm, 3 (20%) in either a junctional or paced rhythm, and 2 (14%) remaining in AF at discharge.



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  		Fig 2. Postoperative rhythm. Y axis = percentage of patients; blue = sinus rhythm; burgundy = paced/junctional; cream = atrial fibrillation. (hosp d/c = hospital discharge; POD = postoperative day; Post-Op OR = postoperative operating room.)

 
Six weeks postoperatively no patients were in AF, 12 (80%) patients were in a normal sinus rhythm, and 3 (20%) were being paced. At this follow-up period, cardiologists still maintained 8 (53%) of these patients on amiodarone and 10 (67%) remained on warfarin. At both 3 and 6 months, 11 (73%) of all patients were in sinus rhythm, 3 (20%) were still being paced, and 1 (7%) was in AF. All but 1 of these patients was no longer in AF 6 months after surgery.


   Comment
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
References
 
Our goal has been to combine robotic MVP with a simple, efficient, and safe AF ablative procedure. We believe that dissection and epicardial placement of the Flex-10 catheter around the base of the pulmonary veins is a safe and easily learned technique. Also, our data show that after 4 patients the dissection and epicardial and endocardial ablation times drop precipitously. However, circumflex artery injury remains a potential complication.

The use of a 5-mm endoscopic handheld camera assists with epicardial dissection and accurate catheter placement. This added visualization also helps the entire surgical team to understand the procedure. Some surgeons advocate additional access through the left thorax using thoracoscopy to ensure proper catheter placement above the LAA and away from the circumflex coronary artery [16]. With our single-incision approach the LAA can be visualized endoscopically through the transverse sinus. After weaning from CPB, the ablation is performed on the beating heart, not only saving CPB time but also assuring better contact with the left atrial wall. Overall, this strategy adds 13 minutes of CPB time for the dissection and catheter placement. The off-pump epicardial ablation adds 19 minutes on average of operating time.

The greatest advantage of this method relates to the ability to perform the endocardial part of a left-sided Maze operation with facility during the MVP. Endocardial lesions were created around the LAA to further isolate automatic foci, and the appendage was excluded to eliminate a potential embolic source. The mitral isthmus lesion from the pulmonary veins to the valve annulus is of particular importance to a complete left-sided ablation. This has been omitted from the off-pump epicardial approach. Initially the Flex-4 device was used, with the bedside surgeon introducing the probe transthoracically and the console surgeon directing the tip using robotic instruments. Because of the stiffness of the probe, the device needed to be preshaped before placement. This meant the console surgeon did not have complete control of lesion placement. However, the Flex-10 is more malleable, and the console surgeon has total control over lesion placement. Robotic stereoscopic vision, high magnification, and tremor filtration enabled the operating surgeon not only to place lesions precisely but also to confirm endocardial carbonization. Moreover, transmural lesions emanating from the epicardial surface can be seen more easily with three-dimensional assisted vision of the robot. If carbonization produces mobile char, robotic instrumentation and irrigation enables evacuation of these potential emboli. Robotic guidance also allows efficient closure of the LAA. Endocardial lesion placement and appendage closure added only 19 minutes of arrested heart time.

Interestingly, our data suggest that return to AF peaks at postoperative day 2, which coincides with the nadir of sinus rhythm. However, by postoperative day 3, the chances of being in normal sinus rhythm have doubled. This may be in part either related to decreasing cardiac edema or from lesion cellular degradation. By postoperative day 3, patients generally retain their rhythm until discharge. Gains in sinus rhythm are then made progressively during the follow-up period largely as a result of continued lesion maturation and progression to scarification. At 6-month telephone follow-up, 73% had returned to a normal sinus rhythm and 93% were free of AF. Although there has been no previously published midterm follow-up data for microwave ablation, our data compare well with other energy sources in which success has been measured at between 70% and 80% of patients in sinus rhythm at 6 months [9, 17].

Potential improvements exist to speed lesion placement and reduce morbidity and mortality. Although the epicardial lesion is placed easily and efficiently with the Flex-10, the catheter is long and cumbersome for use in creating the endocardial lesions. We are currently seeking catheter refinements and method improvements for endocardial lesion placement. Tailoring the connecting lesion from the pulmonary vein to the mitral valve annulus on the basis of individual patient coronary anatomy may improve the recovery rate to normal sinus rhythm and may help to avoid circumflex coronary artery injury [18]. Combined robotic MVP and AF ablation is effective at treating valve disease concomitantly with AF. The procedure is longer; however, patients have a favorable risk-benefit ratio. As learning curves decrease and innovative technology improvements are developed, these combined procedures will be further enabled. Also, as more patients reach long-term follow-up, statistical analysis will help to prove ablative effectiveness. As instrumentation advances, the procedure may progress to a totally endoscopic approach.


   References
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 References
 

  1. Kopecky SL, Gersh BJ, McGoon MD, et al. The natural history of lone atrial fibrillation: a population-based study over three decades N Engl J Med 1987;317:669-674.[Abstract]
  2. Van Gelder IC, Crijns HJ, Tieleman RG, et al. Chronic atrial fibrillationSuccess of serial cardioversion therapy and safety of oral anticoagulation. Arch Intern Med 1996;156:2585-2592.[Abstract/Free Full Text]
  3. Obadia JF, el Farra M, Bastien OH, Lievra M, Martelloni Y, Chassignolle JF. Outcome of atrial fibrillation after mitral valve repair J Thorac Cardiovasc Surg 1998;114:179-185.
  4. Cox JL, Canavan TE, Schuessler RB, et al. The surgical treatment of atrial fibrillation: IIIntraoperative electrophysiologic mapping and description of the electrophysiologic basis of atrial flutter and atrial fibrillation. J Thorac Cardiovasc Surg 1991;101:406-426.[Abstract]
  5. Cox JL, Schuessler RB, D'Augostino Jr HJ, et al. The surgical treatment of atrial fibrillation: IIIDevelopment of a definitive surgical procedure. J Thorac Cardiovasc Surg 1991;101:569-583.[Abstract]
  6. Cox JL, Ad N, Palazzo T, et al. Current status of the Maze procedure for the treatment of atrial fibrillation Semin Thorac Cardiovasc Surg 2000;12:15-19.[Medline]
  7. Haissaguerre M, Jais P, Shah DC, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins N Engl J Med 1998;339:659-666.[Abstract/Free Full Text]
  8. Sueda T, Imai K, Ishii O, et al. Efficacy of pulmonary vein isolation for the elimination of chronic atrial fibrillation in cardiac valvular surgery Ann Thorac Surg 2001;71:1189-1193.[Abstract/Free Full Text]
  9. Williams MR, Stewart JR, Bolling SF, et al. Surgical treatment of atrial fibrillation using radiofrequency energy Ann Thorac Surg 2001;71:1939-1944.[Abstract/Free Full Text]
  10. Williams MR, Knaut M, Bérubé D, Oz MC. Application of microwave energy in cardiac tissue ablation: from in vitro analyses to clinical use Ann Thorac Surg 2002;74:1500-1505.[Abstract/Free Full Text]
  11. Gillinov AM, Smedira NG, Cosgrove DM. Microwave ablation of atrial fibrillation during mitral valve operations Ann Thorac Surg 2002;74:1259-1261.[Abstract/Free Full Text]
  12. 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(Suppl):S1307-11.[Abstract/Free Full Text]
  13. Ad N, Cox JL. The significance of atrial fibrillation ablation in patients undergoing mitral valve surgery Semin Thorac Cardiovasc Surg 2002;14:193-197.[Medline]
  14. Felger JE, Chitwood Jr WR, Nifong LW, Holbert D. Evolution of mitral valve surgery: toward a totally endoscopic approach Ann Thorac Surg 2001;72:1203-1209.[Abstract/Free Full Text]
  15. Nifong LW, Chu VF, Bailey BM, et al. Robotic mitral valve repair: experience with the da Vinci system Ann Thorac Surg 2003;75:438-443.[Abstract/Free Full Text]
  16. 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]
  17. Sie HT, Beukema WP, Misier AR, et al. Radiofrequency modified maze in patients with atrial fibrillation undergoing concomitant cardiac surgery J Thorac Cardiovasc Surg 2001;122:249-256.[Abstract/Free Full Text]
  18. Benussi S, Nascimbene S, Calvi S, Alfieri O. A tailored anatomical approach to prevent complications during left atrial ablation Ann Thorac Surg 2003;75:1979-1981.[Abstract/Free Full Text]



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