Atrial Fibrillation Ablation During Mitral Valve Surgery Using the Atricure™DeviceRalph J.Damiano,Jr,MD,and Sydney L.Gaynor,MDT he Maze III procedure wasfirst performed by Dr.James Cox in1988at our institution.This opera-tion is the gold standard for the surgical treatment of atrialfibrillation(AF).On long-term follow-up,over 90%of patients are free of AF.The great majority of these patients also are off antiarrhythmic drugs.1 However,this procedure has not been widely adopted due to its invasiveness,technical difficulty, and complexity.To decrease the morbidity of the cut-and-sew Cox-Maze procedure,our group has evaluated replacing many of the surgical incisions with linear ablation using bipolar radiofrequency(RF)energy.The RF ablation device is manufactured by Atricure,Inc.(Cincinnati, Ohio).Radiofrequency energy is delivered between two closely approximated5-cmϫ1-mm electrodes embed-ded in the jaws of a specially designed clamp.Bipolar RF has several advantages over other energy sources that have been used for surgical AF ablation.By mea-suring the drop in tissue conductance between the two electrodes,the transmurality of the ablation can be measured online and be used to control the time of energy delivery.Extensive experimental evaluation in our laboratory has revealed that using this conduc-tance algorithm,lesions are always transmural.2-4 Moreover,because of the focused delivery of energy between two closely approximated electrodes,the le-sions are discrete and thin,measuring between1and3 mm in width.Thus,this device eliminates the possibil-ity of collateral tissue injury or scar contraction.In our experimental evaluation,there was no evidence of late pulmonary vein stenosis at1month,as evaluated by high resolution magnetic resonance imaging.3Our re-search also demonstrated no evidence of injury to the coronary sinus or to the tricuspid or mitral valve leaf-lets by bipolar RF ablation.Over the last2years,we have performed over50 clinical procedures with this device.In the following paragraphs,we summarize our present surgical tech-nique with this less invasive Cox-Maze procedure.24Operative Techniques in Thoracic and Cardiovascular Surgery,Vol9,No1(Spring),2004:pp24-33SURGICALTECHNIQUE1After induction of anesthesia and median sternotomy,the patient is placed on cardiopulmonary bypass using bicaval cannulation.Initially,the patient is perfused at 36°C to maintain sinus rhythm and allow for accurate determination of pacing thresholds from the pulmonary veins.The left and right pulmonary veins are bluntly dissected and surrounded with umbilical tape.Occasionally,it is necessary to sharply divide the pericardial re flection behind the right and left superior pulmonary veins.On the right side,the space between the right superior pulmonary vein and right pulmonary artery must be carefully developed using blunt dissection.On the left side,it is important to develop a similar space between the left superior pulmonary vein and the left pulmonary artery to avoid injury when placing the bipolar clamp.There often is a fold of tissue (the Ligament of Marshall)that extends from the left pulmonary artery to the left superior pulmonary vein.This is usually divided with Bovie cautery.Following the pulmonary vein dissection,the patient is electrically cardioverted if in AF.Pacing thresholds are then recorded from the superior and inferior pulmonary veins.The bipolar radiofrequency device is then placed around the right pulmonary veins.The device is clamped on the cuff of atrial tissue surrounding the pulmonary veins.RF energy is delivered until the algorithm con firms transmurality.The average RF ablation time has been 9.5Ϯ3.8s in our series.Following the initial ablation,the device is unclamped,moved proximally several millimeters further up on the atrial cuff,and re-clamped for a second ablation.In our experience,this usually ensures electrical isolation.In patients with large pulmonary veins,it may be necessary to clamp the superior and inferior veins separately.Electrical isolation is documented by pacing from both the superior and inferior pulmonary veins at a stimulus strength of 20mA.Further ablations are performed as necessary until there is documented conduction block.ATRIAL FIBRILLATION ABLATION IN MITRAL VALVE SURGERY252Following completion of the right pulmonary vein isolation,the left pulmonary veins are isolated in a similar fashion with the bipolar radio-frequency device.Both right and left pulmonary vein isolations are per-formed with the heart beating at nor-mothermictemperatures.3The right atrial lesions of this modi fied Cox-Maze procedure are then performed with the heart beat-ing.Umbilical tapes are tightened over both caval cannulae.The right atrial appendage is preserved.A small incision is made at the mid-point of the appendage to allow in-sertion of the bipolar RF device.This incision is extended superiorly up to the atrioventricular groove.26DAMIANO ET AL4Through this incision,the bi-polar RF device is placed,and an ablation is performed on the right atrial free wall.A cardiotomy sucker is placed in the right atrium to re-move the blood return from the cor-onarysinus.5A vertical right atriotomy is then performed.Approximately 2cm of space should be left between this incision and the previously per-formed right atrial free wall abla-tion.This incision is extended as shown up to the atrioventricular groove.It is extended inferiorly down toward the intraatrial septum dividing the crista terminalis.ATRIAL FIBRILLATION ABLATION IN MITRAL VALVE SURGERY276Superiorly,the atrioventricular fat pad is re flected off of the underlying right atrial tissue adjacent to the incision which extends from the right atrial appendage.This dissection is performed with the Bovie cautery on a low setting.Care is taken during this dissection to carefully control small venous and arterial branches that arise from the right coronary system.A curved tonsil forceps is then used to develop the plane down to the tricuspid anulus.By looking inside the right atrium,one can visualize the extent of the dissection through the thin-walled atrial tissue.Once the dissection is carried down to the tricuspid anulus,the bipolar clamp is placed such that one arm is inside the atrium,and the other extends outside the atrium but underneath the re flected atrioventricular groove fat ing direct visualization,the clamp should cross the tricuspid anulus and extend slightly onto valvular tissue.If,for some reason,the clamp cannot be placed all the way down to the tricuspid valve anulus,the small gap of remaining tissue can be ablated using a 3-mm cryoprobe.Right atrial cryolesions are performed with a Frigitronics probe (Cooper Medical;Trumbull,Connecticut)for 2minutes at Ϫ60°C.7A similar dissection is per-formed extending from the vertical right atriotomy down to the tricuspid valve anulus on the opposite side.In a likewise fashion,the Bovie cautery at low settings is used to re flect the atrioventricular groove fat pad.A curved tonsil forceps is used to gently spread the fat overlying the atrial tissue down to the tricuspid anulus.The bipolar clamp is then advanced with one arm inside the right atrium and the other outside the atrium but underneath the fat pad down to the tricuspid anulus.An ablation is performed with care be-ing taken to assure that the jaws of the clamp extend onto the tricuspid valve.28DAMIANO ET AL8From the inferior aspect of the vertical right atriotomy,the bipolar clamp is then placed up to the supe-rior vena cava.It is important that the ablation extends onto caval tis-sue.It is often necessary to loosen the umbilicaltape.9The clamp is then rotated 180°and extended in a similar fashion onto the inferior vena cava (IVC).Again,it is usually necessary to loosen the umbilical tape around the IVC cannula.A single ablation is then performed.This completes the right atrial lesions of the modi fied Cox-Maze procedure.At this point,a retrograde cardioplegia catheter is placed under direct vision into the coronary sinus.The heart is ar-rested using a combination of ante-grade and retrograde cold blood car-dioplegia.ATRIAL FIBRILLATION ABLATION IN MITRAL VALVE SURGERY2910A standard left atriotomy isperformed below the interatrial groove and extended inferiorly around the right inferior pulmonary vein.It is critical that this left atri-otomy intersects at some point the encircling right pulmonary vein ab-lation.If the surgical incision does not intersect this ablation,a sepa-rate bipolar ablation line should be placed from the incision down into one of the right pulmonary veins.The transseptal incision of the Cox-Maze III procedure can be replaced with a bipolar RF ablation at this point across the atrial septum onto the fossa ovalis.The atriotomy is ex-tended inferiorly across the poste-rior left atrial free wall in the direc-tion of the mitral valve anulus.The incision is carried down to the atrio-ventricular groove approximately at the junction between the P2and P3scallop of the posterior lea flet of the mitral valve.By biasing the incision toward P3,it is unlikely to find the circum flex coronary artery still in the atrioventricular groove at this point,especially with a right domi-nant coronary system.30DAMIANO ET AL11When the incision reaches the atrioventricular groove,it is continued from the endocardial surface using a 15-bladescalpel.This endocardial incision crosses the coronary sinus,and care should be taken to avoid injury to this structure.The dissection around the coronary sinus should be performed carefully with a nerve hook.In the fat surrounding the coronary sinus,the surgeon should con firm that there is no branch of the circum flex coronary artery.At this point,there are two choices.The bipolar radiofrequency clamp can be placed over the atrioventricular groove and coronary sinus up to the mitral valve anulus,and an ablation can be performed.Following this ablation,a single cryolesion is placed adjacent to the mitral valve anulus using a 3mm cryoprobe.This cryoablation is performed at 3minutes at Ϫ60°C using circulating nitrous oxide.If the surgeon does not wish to use radiofrequency ablation over the coronary sinus,or there is a branch of the circum flex in the fat pad,it is recommended that the coronary sinus be cryoablated separately using a 15-mm cryoprobe.Following this,a bipolar radiofrequency ablation is then performed from the posterior aspect of this incision extending into the left inferior pulmonary vein as shown in the figure.The valve repair is performed at this point.In cases in which a mitral valve replacement is to be performed,the left atrial appendage should be amputated (step 12)prior to seating the prosthesis to avoid excessive retraction.ATRIAL FIBRILLATION ABLATION IN MITRAL VALVE SURGERY31SUMMARYWe have now used bipolar radiofrequency ablation in over 50cases.A total of 43patients have undergone a complete modi fied Cox-Maze procedure as described above;19had a lone Maze procedure,and 24had a Maze procedure plus a concomitant operation.At 1month postoperatively,high resolution MRI scans were performed in the first 8patients to evaluate for pulmo-nary vein stenosis.All patients have been followed monthly since their operation by clinical examination and serial electrocardiograms.In our early experience with this procedure,there have been no operative mortalities.The cross-clamp time required to perform the modi fied bipolar radio-frequency ablation-assisted Maze procedure was 43Ϯ26minutes.This was signi ficantly shorter than our experience with the cut-and-sew lone Cox-Maze proce-dure (93Ϯ34minutes;P Ͻ0.05).Similarly,for con-comitant procedures,our cross-clamp time was re-duced from 122Ϯ37minutes to 92Ϯ37minutes (P Ͻ0.05)when compared with the traditional cut-and-sew Maze procedure.The mean follow-up time in our series has been 7.4Ϯ5.5months.Follow-up MRI showed no evidence of pulmonary vein stenosis,and atrial contractility was preserved in all patients.There were no late strokes.At a 6-months follow-up,91%of patients were in sinus rhythm.At last follow-up,41of 43patients (95%)were free from atrial fibrillation.At a 6-month follow-up,only 10patients were still on antiarrhythmic drugs.Our results show that bipolar radiofrequency abla-tion can replace the majority of incisions of the tradi-tional cut-and-sew Maze procedure.This signi ficantly decreases the amount of time to perform the procedure.The morbidity with this new procedure appears to be low,while still maintaining the ef ficacy of the tradi-tional cut-and-sew Maze procedure.With this simpli-fied operation,the Maze procedure can safely be added to all patients with AF coming to the operating room for correction of their valvular heart disease.ACKNOWLEDGEMENTSThis work supported by National Institutes of Health Grant 2R01HL032257.12Following completion of thevalve repair,a left ventricular vent is placed via the right superior pul-monary vein.The left atriotomy is closed with a running mono filament suture.The heart is retracted,and the left atrial appendage is ampu-tated.The bipolar clamp is placed through the amputated appendage down into the left superior pulmo-nary vein with one jaw inside and the other outside the atrium.This abla-tion should overlap the previously performed encircling ablation of the left pulmonary veins.The left atrial appendage is oversewn in two layers using running mono filament suture.The aorta is unclamped,and the right atrial incision is closed during the rewarming period.Pacing wires are placed on both the right atrium and right ventricle before weaning from cardiopulmonary bypass.32DAMIANO ET ALREFERENCES1.Prasad SM,Maniar HS,Camillo CJ,et al:The Cox Qqhyphenmaze IIIprocedure for atrialfibrillation:Long-term efficacy in patients undergo-ing lone versus concomitant procedure.J Thorac Cardiovasc Surg126: 1822-1828,20032.Prasad SM,Maniar HS,Schuessler RB,et al:Chronic transmural atrialablation by using bipolar radiofrequency energy on the beating heart.J Thorac Cardiovasc Surg124:708-713,20023.Prasad SM,Maniar HS,Moustakidis P,et al:Epicardial ablation on thebeating heart:Progress towards an off-pump Maze procedure.Hear Surg Forum5:100-104,20024.Prasad SM,Maniar HS,Diodato MD,et al:Physiological consequencesof bipolar radiofrequency energy on the atria and pulmonary veins:A chronic animal study.Ann Thorac Surg76:836-842,2003From the Department of Cardiothoracic Surgery,Washington University School of Medicine,St.Louis,MO.Address correspondence to Ralph J.Damiano,Jr,MD,Cardiothoracic Surgery, Washington University School of Medicine,Suite3108,Queeny Tower,Box8234, One Barnes-Jewish Hospital Plaza,St.Louis,MO63110.©2004Elsevier Inc.All rights reserved.1522-2942/04/0901-0004$30.00/0doi:10.1053/j.optechstcvs.2004.01.002ATRIAL FIBRILLATION ABLATION IN MITRAL VALVE SURGERY33。
