- Email: [email protected]
The Surgical Treatment of Atrial Fibrillation Via Median Sternotomy
Accepted Manuscript
The Surgical Treatment of Atrial Fibrillation via Median Sternotomy Robert M. MacGregor MD , Ali J. Khiabani MD , Ralph J. Damiano Jr. MD PII: DOI: Reference:
S1522-2942(19)30007-8 https://doi.org/10.1053/j.optechstcvs.2019.07.001 YOTCT 471
To appear in: Atlas
Operative Techniques in Thoracic and Cardiovascular Surgery: A Comparative
Please cite this article as: Robert M. MacGregor MD , Ali J. Khiabani MD , Ralph J. Damiano Jr. MD , The Surgical Treatment of Atrial Fibrillation via Median Sternotomy, Operative Techniques in Thoracic and Cardiovascular Surgery: A Comparative Atlas (2019), doi: https://doi.org/10.1053/j.optechstcvs.2019.07.001
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
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Operative Techniques in Thoracic and Cardiovascular Surgery: A Comparative Atlas
The Surgical Treatment of Atrial Fibrillation via Median Sternotomy
Robert M. MacGregor, MD, Ali J. Khiabani, MD, Ralph J. Damiano, Jr., MD*
Department of Surgery, Division of Cardiothoracic Surgery, Washington University School of Medicine, Barnes-Jewish Hospital, St. Louis, Missouri
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*Corresponding Author: Ralph J. Damiano, Jr., MD, Washington University School of Medicine, Barnes-Jewish Hospital, Division of Cardiothoracic Surgery, Campus Box 8234, 660 S. Euclid Ave., St. Louis, MO 63110, Phone: 314-362-7327, Fax: 314-361-8706, Email: [email protected]
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Conflict of Interest Disclosure: R.J.D. – Atricure, Inc: Speaker and receives research funding; LivaNova, Inc.: Speaker. Medtronic: Consultant; Edwards Lifesciences: Speaker. Other authors have nothing to disclose.
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Abstract Atrial fibrillation (AF) is the most common cardiac arrhythmia in the United States and remains a major cause of significant morbidity and mortality. Current treatment options include medical
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management, catheter ablation, and surgical techniques, which have been improved over the past decades through surgical innovation and advancement in instrumentation. The gold-standard of surgical treatment for AF is the Cox-Maze procedure (CMP). First introduced clinically in 1987, the procedure used multiple incisions in the left and right atria to eliminate AF. This cut-and-sew
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technique was subsequently replaced by the CMP-IV with the advent of bipolar radiofrequency (RF) and cryoablation technology. The modern ablation devices have made the CMP technically faster and more amenable to minimally invasive approaches. This manuscript reviews the
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surgical technique of the Cox-Maze IV procedure through a median sternotomy approach.
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Keywords: atrial fibrillation, surgical ablation
Short Introductory Section
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The Cox-Maze procedure (CMP) was first described by James Cox and colleagues in 1987, which employed a myriad of biatrial incisions to develop geometrically organized scar in an
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attempt to electrically isolate the pulmonary veins and the posterior left atrium.1 The first
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iteration of the CMP resulted in a high incidence of pacemaker placement due to a lack of sinus node response to stress and exercise.2 The CMP-II was too technically difficult, and was replaced by the third iteration of the CMP, which became the gold standard for surgical treatment of AF. The incisions performed in the operation allowed all of the atrial myocardium to be activated while directing the electrical impulses from the sinoatrial (SA) to the atrioventricular (AV) node.3
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The Cox-Maze III procedure achieved excellent results in a long-term study, as 97% of the patients at late follow-up were free from symptomatic AF.4 Despite this success, there was never a widespread use of this operation, due to its inherent technical complexity. Over the past two
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decades, the intricate incisions of the cut-and-sew technique have been replaced by the use of surgical energy sources capable of performing tissue ablations. The energy devices, employing radiofrequency and cryoablation technology, have been shown to reliably create transmural lesions.5 Furthermore, the devices are able to replicate the incisions of the CMP-III in a
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technically simpler, faster, and less-invasive manner. The use of surgical ablation technology prompted the development of the Cox-Maze IV procedure, which is currently the procedure of
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choice for the surgical treatment of AF.
Indications for Surgical Treatment of Atrial Fibrillation
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The indications for surgical ablation for atrial fibrillation have been defined in recent guidelines and consensus statements and include6,7,8:
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1. All symptomatic patients with documented AF undergoing cardiac surgery
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2. Selected asymptomatic patients with AF undergoing cardiac surgery in which the ablation can be performed with minimal risk in experienced centers
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3. Stand-alone surgery should be considered for symptomatic patients with AF refractory or intolerant to at least one Class I or III antiarrhythmic drug, and/or have failed one or more attempts at catheter-based ablation, or are not candidates for catheter-based ablation.
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At our institution, additional relative indications for surgical ablation of atrial fibrillation are9: 1. Patients with AF who have developed a contraindication to long-term anticoagulation and have a high risk of stroke (CHADS score ≥ 2). The CMP not only can eliminate AF in most of these patients, but also excludes the left atrial appendage, which is the most
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common source of atrial thrombus.
2. Patients with longstanding AF who have suffered a cerebrovascular accident despite adequate anticoagulation, and are at high risk for repeat neurological events.
3. Symptomatic AF patients with clot in the left atrial appendage who are not candidates for
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catheter ablation and should be considered for surgical ablation.
Main Section (10-15 drawings)
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Figure 1. Median Sternotomy and Bicaval Cannulation The patient is brought to the operating room, placed supine on the operating table, and
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anesthetized. A transesophageal echocardiogram is performed to evaluate cardiac pathology and to rule out presence of clot in the left atrial (LA) appendage or a patent foramen ovale (PFO). If
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an atrial thrombus is identified, the heart should not be manipulated or cardioverted prior to cross-clamping. A median sternotomy is performed. Ascending aortic and bicaval cannulation is
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performed and normothermic cardiopulmonary bypass is initiated. Umbilical tapes are placed
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around the superior and inferior vena cava.
Figure 2. Right Pulmonary Vein Isolation
The left and right pulmonary veins are bluntly dissected and surrounded with umbilical tape after cardiopulmonary bypass is initiated. The oblique and transverse sinuses are mobilized. The
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intraatrial septum needs to be dissected and developed for two important reasons. First, it allows for the isolation of a generous cuff of atrial tissue around the right pulmonary veins. Second, the removal of as much fat as possible from surrounding the right pulmonary veins is critical to allow for effective ablation. Fat is an excellent insulator and can prevent transmural lesion
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formation if not removed. Blunt dissection is used to develop the space between the right
superior pulmonary vein and right pulmonary artery. On the left side, the space between the left superior pulmonary vein and left pulmonary artery should be developed, and the Ligament of Marshall is usually divided with Bovie cautery. Following pulmonary vein dissection, if the
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patient is in atrial fibrillation, attempts should be made to restore sinus rhythm. An IV bolus of amiodarone (150 mg) is given and cardioversion is performed. Pacing thresholds for each pulmonary vein are obtained prior to ablation. The bipolar radiofrequency device is clamped
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around as large a cuff of atrial tissue surrounding the right pulmonary veins as possible. Radiofrequency energy is delivered until the algorithm confirms transmurality. An additional
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ablation is performed prior to unclamping the device. Following the initial two ablations, the device is unclamped and moved a few millimeters proximally or distally and reclamped to
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perform a second set of ablations. Three sets of ablations are performed on the pulmonary veins,
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and for all other lesions of the CMP-IV. Pacing is then performed from the pulmonary veins at
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20 mA to confirm exit block.
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Figure 3. Left Pulmonary Vein Isolation After completion of the right pulmonary vein isolation, the left pulmonary veins are isolated in a similar fashion with the bipolar radiofrequency device. The right and left pulmonary vein
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isolations are performed with the heart beating at normothermic temperatures. In patients with large pulmonary veins it may be necessary to clamp the superior and inferior veins separately. Electrical isolation is confirmed by documenting exit block from both the superior and inferior
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pulmonary veins. Further ablations may be necessary until there is documented conduction block.
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Figure 4. Right Atrial Lesion Set: Right Atrial Appendage Following pulmonary vein isolation, the right atrial lesion set is performed on the beating heart.
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The patient is cooled to 34ºC. A small purse-string suture is placed at the base of the right atrial appendage. The purse-string should be sutured wide enough to accommodate the lower jaw of
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the bipolar RF clamp. The clamp is positioned through the purse-string and directed down the
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aortic side of the right atrial appendage to perform the right atrial free wall ablation.
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Figure 5. Right Atrial Lesion Set: Vertical Atriotomy and Intercaval Ablation A vertical right atriotomy is performed extending from just above the interatrial septum midway between the superior and inferior vena cava up toward the acute margin of the heart near the
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atrioventricular groove. From the inferior aspect of the atriotomy, the RF clamp is used to create ablation lines up to the superior vena cava and down to the inferior vena cava.
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Figure 6. Right Atrial Lesion Set: Tricuspid Annulus Ablation From the superior aspect of the atriotomy, a linear cryoprobe is used to perform an endocardial ablation extending down towards the tricuspid annulus at the 2 o’clock position. A second endocardial ablation is performed through the purse-string at the base of the right atrial appendage, extending down to the tricuspid annulus at the 10 o’clock position. The endocardial
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cryoablations are performed for 3 minutes at a temperature of -60ºC. A retrograde cardioplegia
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cannula is positioned in the coronary sinus under direct vision and secured with a purse-string
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suture. The right atrium is closed with a running 4-0 Prolene suture.
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Figure 7. Left Atrial Lesion Set: Left Atrial Appendage On completion of the right atrial lesion set, the heart is arrested using cold-blood cardioplegia
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and the aorta is cross-clamped. The heart is retracted to expose the left atrial appendage. The left atrial appendage is amputated, leaving a 1-2 cm cuff of atrial tissue at the base. A connecting lesion is created with the RF clamp that extends through the amputated appendage into the left superior or inferior pulmonary vein, crossing the previous ablation line. The left atrial appendage is subsequently oversewn with 4-0 Prolene suture in 2 layers. The coronary sinus is marked with
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methylene blue between the terminal branches of the circumflex and the posterior descending coronary arteries.
Figure 8. Left Atrial Lesion Set: Atriotomy and Box Pulmonary Vein Isolation A standard left atriotomy is performed below the interatrial groove and extended inferiorly
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around and behind the right inferior pulmonary vein. The bipolar RF clamp is positioned at the inferior aspect of the left atriotomy and an ablation line is created across the floor of the left atrium into the left inferior pulmonary vein. From the superior aspect of the left atriotomy, the RF clamp is used to create an additional ablation line across the roof of the left atrium into the
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left superior pulmonary vein. The “box lesion” completely isolates the entire posterior left atrium and all four pulmonary veins.
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Figure 9. Left Atrial Lesion Set: Mitral Valve Annulus The bipolar RF clamp is used to create an ablation line from the inferior aspect of the atriotomy
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and directed across the floor of the left atrium towards the mitral valve annulus. This ablation line crosses the coronary sinus, which was previously marked with methylene blue. A 15 mm
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bell-shaped cryoprobe is used to create an endocardial ablation to connect this lesion to the
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mitral valve annulus.
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Figure 10. Left Atrial Lesion Set: Left Atrial Isthmus The left atrial lesion set is completed by performing epicardial cryoablation over the coronary sinus. A linear cryoprobe is placed along the epicardial surface and in line with the previously performed endocardial ablation. A left ventricular (LV) vent is placed through the right superior pulmonary vein. The left atriotomy is closed with a running 4-0 Prolene suture. The patient is weaned from cardiopulmonary bypass and the sternotomy is closed in a standard fashion.
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Short Closing Section Post-Operative Care The successful completion of the CMP-IV requires effective post-operative care, most importantly the monitoring of post-operative arrhythmias. The epicardial pacing wires that are
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sewn to the right atria and ventricle prior to closure of the chest are used to pace the atria at a rate of 80 to 100 beats per minute if needed. Frequent interrogation of the underlying electrical
activity is performed. Junctional rhythms are most commonly seen post-operatively after CMPIV. In the event heart block develops, the pacer can be changed to AV sequential pacing [dual-
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chamber (DDD) mode] to optimize cardiac function. Patients are started on antiarrhythmic
medications once they return to normal sinus rhythm. Patients with persistent bradycardia due to a junctional rhythm are followed for 5-7 days to allow for sinus node recovery. It is important to avoid antiarrhythmic drugs and beta-blockers in these patients. If they remain in a symptomatic
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bradycardia after this time, a dual chamber pacemaker is inserted. In patients with complete heart
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block, pacemaker insertion is usually performed after a waiting period of 5 days. Unfortunately, 5% of patients require permanent pacemaker placement due to persistent heart block or sinus
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node dysfunction after a lone CMP-IV, which increases in the elderly population.10 Atrial tachyarrhythmias (ATAs) may occur post-operatively, but usually resolve within the first month
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after the operation. Patients with persistent ATAs receive pharmacologic treatment with class 1
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or 3 antiarrhythmic drugs (AAD), as well as cardioversion if necessary. The final post-operative consideration is starting anticoagulation therapy. All patients receiving CMP-IV and without contraindications are started on Warfarin or a novel anticoagulant agent post-operatively and continued for 3-6 months. Anticoagulation can be discontinued when the patient is demonstrated to have not experienced ATAs off antiarrhythmic medications as seen on prolonged monitoring
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(24-hour or greater Holter monitor recording), and showed no atrial stasis or thrombus on echocardiography.
Surgical Results The CMP remains the most successful method of terminating ATAs and is the gold standard in
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the surgical treatment of AF. Outcomes of the CMP-IV have shown 91% of patients were free from ATAs at six months in a single-center study, while a more recent prospective cohort study of 100 patients undergoing stand-alone CMP-IV showed freedom from AF of 93%, 90%, and 90% at 6, 12, and 24 months, respectively.11,12 At long term follow-up, Ad et al. reported
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freedom from ATAs of 88% and 85% at 2 and 5 years, respectively.13 These results were similar to the experience at our institution that reviewed 576 consecutive patients undergoing CMP-IV between January 2002 and September 2014. In that study, twelve month freedom from ATAs
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was 93%, with 85% of patients free from antiarrhythmic drugs. At five years the freedom from ATAs was 78%, with 66% of patients free from AAD. The study showed no difference in
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freedom from ATAs off AAD at any time point between patients with paroxysmal or persistent
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AF.14
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Minimally invasive techniques remain the future of cardiac surgery, and have been shown to lower complication rates and overall hospital costs without compromising results.15 Though
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median sternotomy for CMP-IV remains highly effective, advancements in surgical ablation technology have allowed for a less invasive approach. A minimally invasive operation through right mini-thoracotomy (RMT) for CMP-IV reduces overall morbidity and operative risk, as well as cardiopulmonary bypass and aortic cross clamp time compared to median sternotomy.16 The RMT approach has showed similar success in the treatment of AF, and is our approach of choice
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for a stand-alone procedure. A retrospective review conducted of 365 patients at our institution undergoing CMP-IV found 79% freedom from ATAs and AADs at two years follow-up through sternotomy approach, compared to 74% for RMT. The RMT group had significantly less major complications compared to sternotomy group (6% vs 13%, P=0.04).16 Further work must be
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done to increase the number of patients undergoing surgical treatment of AF, especially in the setting of concomitant procedures. In conjunction with the improvement of surgical ablation technology, a greater understanding of the mechanisms underlying the development of atrial
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fibrillation would allow for more tailored lesions sets to more efficiently treat patients with AF.
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References 1. Cox JL, The surgical treatment of atrial fibrillation. IV. Surgical technique. J Thorac Cardiovasc Surg 1991;101:584-92. 2. Cox JL, Boineau JP, Schuessler RB, et al. Successful Surgical Treatment of Atrial Fibrillation: Review and Clinical Update. JAMA. 1991;266(14):1976–80. 3. Cox JL, Schuessler RB, D’Agostino HJ Jr, et al. The surgical treatment of atrial fibrillation, III: development of a definitive surgical procedure. J Thorac Cardiovasc Surg. 1991;101:569-83. 4. Cox JL, Ad N, Palazzo T, Fitzpatrick S, Suyderhoud JP, DeGroot KW et al. Current status of the Maze procedure for the treatment of atrial fibrillation. Semin Thorac Cardiovasc Surg 2000;12:15–9. 5. Melby SJ, Schuessler RB, Damiano RJ. Ablation technology for the surgical treatment of atrial fibrillation. ASAIO J. 2013;59(5):461-8. 6. Badhwar V, Rankin JS, Damiano Jr RJ, Gillinov AM, Bakaeen FG, Edgerton JR, et al. The Society of Thoracic Surgeons 2017 Clinical Practice Guidelines for the Surgical Treatment of Atrial Fibrillation. Ann Thorac Surg 2017;103:329–41. 7. Calkins H, Hindricks G, Cappato R, et al. 2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation. Europace. 2017;20(1):e1-e160. 8. Ad N, Damiano RJ Jr, Badhwar V, Calkins II, La Meir M, Nitta T, et al. Expert consensus guidelines: examining surgical ablation for atrial fibrillation. J Thorac Cardiovasc Surg. 2017;153:1330-35.e1. 9. Ruaengsri C, Schill MR, Khiabani AJ, Schuessler RB, Melby SJ, Damiano RJ, Jr. The Cox-maze IV procedure in its second decade: still the gold standard? European Journal of Cardiothoracic Surgery. 2018;53(suppl_1):i19-i25. 10. Robertson JO, Cuculich PS, Saint LL, et al. Predictors and risk of pacemaker implantation after the Cox-Maze IV procedure. Ann Thorac Surg 2013;95:2015-20. 11. Gaynor SL, Diodato MD, Prasad SM, Ishii Y, Schuessler RB, Bailey MS et al. A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation. J Thorac Cardiovasc Surg 2004;128:535–42. 12. Weimar T, Bailey MS, Watanabe Y, Marin D, Maniar HS, Schuessler RB et al. The Coxmaze IV procedure for lone atrial fibrillation: a single center experience in 100 consecutive patients. J Interv Card Electrophysiol 2011;31:47–54. 13. Ad N, Holmes SD, Stone LE, Pritchard G, Henry L. Rhythm course over 5 years following surgical ablation for atrial fibrillation. Eur J Cardiothorac Surg 2015;47:52–8. 14. Henn MC, Lancaster TS, Miller JR, Sinn LA, Schuessler RB, Moon MR et al. Late outcomes after the Cox maze IV procedure for atrial fibrillation. J Thorac Cardiovasc Surg 2015;150:1168–76, 1178.e1–2. 15. Schmitto JD, Mokashi SA, Cohn LH. Past, present, and future of minimally invasive mitral valve surgery. J Heart Valve Dis 2011;20(5):493-8. 16. Lawrance CP, Henn MC, Miller JR, Sinn LA, Schuessler RB, Maniar HS et al. A minimally invasive Cox maze IV procedure is as effective as sternotomy while decreasing major morbidity and hospital stay. J Thorac Cardiovasc Surg 2014;148:955– 61; discussion 62–2.
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The Surgical Treatment of Atrial Fibrillation via Median Sternotomy Robert M. MacGregor MD , Ali J. Khiabani MD , Ralph J. Damiano Jr. MD PII: DOI: Reference:
S1522-2942(19)30007-8 https://doi.org/10.1053/j.optechstcvs.2019.07.001 YOTCT 471
To appear in: Atlas
Operative Techniques in Thoracic and Cardiovascular Surgery: A Comparative
Please cite this article as: Robert M. MacGregor MD , Ali J. Khiabani MD , Ralph J. Damiano Jr. MD , The Surgical Treatment of Atrial Fibrillation via Median Sternotomy, Operative Techniques in Thoracic and Cardiovascular Surgery: A Comparative Atlas (2019), doi: https://doi.org/10.1053/j.optechstcvs.2019.07.001
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
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Operative Techniques in Thoracic and Cardiovascular Surgery: A Comparative Atlas
The Surgical Treatment of Atrial Fibrillation via Median Sternotomy
Robert M. MacGregor, MD, Ali J. Khiabani, MD, Ralph J. Damiano, Jr., MD*
Department of Surgery, Division of Cardiothoracic Surgery, Washington University School of Medicine, Barnes-Jewish Hospital, St. Louis, Missouri
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*Corresponding Author: Ralph J. Damiano, Jr., MD, Washington University School of Medicine, Barnes-Jewish Hospital, Division of Cardiothoracic Surgery, Campus Box 8234, 660 S. Euclid Ave., St. Louis, MO 63110, Phone: 314-362-7327, Fax: 314-361-8706, Email: [email protected]
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Conflict of Interest Disclosure: R.J.D. – Atricure, Inc: Speaker and receives research funding; LivaNova, Inc.: Speaker. Medtronic: Consultant; Edwards Lifesciences: Speaker. Other authors have nothing to disclose.
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Abstract Atrial fibrillation (AF) is the most common cardiac arrhythmia in the United States and remains a major cause of significant morbidity and mortality. Current treatment options include medical
CR IP T
management, catheter ablation, and surgical techniques, which have been improved over the past decades through surgical innovation and advancement in instrumentation. The gold-standard of surgical treatment for AF is the Cox-Maze procedure (CMP). First introduced clinically in 1987, the procedure used multiple incisions in the left and right atria to eliminate AF. This cut-and-sew
AN US
technique was subsequently replaced by the CMP-IV with the advent of bipolar radiofrequency (RF) and cryoablation technology. The modern ablation devices have made the CMP technically faster and more amenable to minimally invasive approaches. This manuscript reviews the
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surgical technique of the Cox-Maze IV procedure through a median sternotomy approach.
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Keywords: atrial fibrillation, surgical ablation
Short Introductory Section
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The Cox-Maze procedure (CMP) was first described by James Cox and colleagues in 1987, which employed a myriad of biatrial incisions to develop geometrically organized scar in an
CE
attempt to electrically isolate the pulmonary veins and the posterior left atrium.1 The first
AC
iteration of the CMP resulted in a high incidence of pacemaker placement due to a lack of sinus node response to stress and exercise.2 The CMP-II was too technically difficult, and was replaced by the third iteration of the CMP, which became the gold standard for surgical treatment of AF. The incisions performed in the operation allowed all of the atrial myocardium to be activated while directing the electrical impulses from the sinoatrial (SA) to the atrioventricular (AV) node.3
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The Cox-Maze III procedure achieved excellent results in a long-term study, as 97% of the patients at late follow-up were free from symptomatic AF.4 Despite this success, there was never a widespread use of this operation, due to its inherent technical complexity. Over the past two
CR IP T
decades, the intricate incisions of the cut-and-sew technique have been replaced by the use of surgical energy sources capable of performing tissue ablations. The energy devices, employing radiofrequency and cryoablation technology, have been shown to reliably create transmural lesions.5 Furthermore, the devices are able to replicate the incisions of the CMP-III in a
AN US
technically simpler, faster, and less-invasive manner. The use of surgical ablation technology prompted the development of the Cox-Maze IV procedure, which is currently the procedure of
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choice for the surgical treatment of AF.
Indications for Surgical Treatment of Atrial Fibrillation
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The indications for surgical ablation for atrial fibrillation have been defined in recent guidelines and consensus statements and include6,7,8:
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1. All symptomatic patients with documented AF undergoing cardiac surgery
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2. Selected asymptomatic patients with AF undergoing cardiac surgery in which the ablation can be performed with minimal risk in experienced centers
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3. Stand-alone surgery should be considered for symptomatic patients with AF refractory or intolerant to at least one Class I or III antiarrhythmic drug, and/or have failed one or more attempts at catheter-based ablation, or are not candidates for catheter-based ablation.
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At our institution, additional relative indications for surgical ablation of atrial fibrillation are9: 1. Patients with AF who have developed a contraindication to long-term anticoagulation and have a high risk of stroke (CHADS score ≥ 2). The CMP not only can eliminate AF in most of these patients, but also excludes the left atrial appendage, which is the most
CR IP T
common source of atrial thrombus.
2. Patients with longstanding AF who have suffered a cerebrovascular accident despite adequate anticoagulation, and are at high risk for repeat neurological events.
3. Symptomatic AF patients with clot in the left atrial appendage who are not candidates for
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catheter ablation and should be considered for surgical ablation.
Main Section (10-15 drawings)
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Figure 1. Median Sternotomy and Bicaval Cannulation The patient is brought to the operating room, placed supine on the operating table, and
ED
anesthetized. A transesophageal echocardiogram is performed to evaluate cardiac pathology and to rule out presence of clot in the left atrial (LA) appendage or a patent foramen ovale (PFO). If
PT
an atrial thrombus is identified, the heart should not be manipulated or cardioverted prior to cross-clamping. A median sternotomy is performed. Ascending aortic and bicaval cannulation is
CE
performed and normothermic cardiopulmonary bypass is initiated. Umbilical tapes are placed
AC
around the superior and inferior vena cava.
Figure 2. Right Pulmonary Vein Isolation
The left and right pulmonary veins are bluntly dissected and surrounded with umbilical tape after cardiopulmonary bypass is initiated. The oblique and transverse sinuses are mobilized. The
ACCEPTED MANUSCRIPT
intraatrial septum needs to be dissected and developed for two important reasons. First, it allows for the isolation of a generous cuff of atrial tissue around the right pulmonary veins. Second, the removal of as much fat as possible from surrounding the right pulmonary veins is critical to allow for effective ablation. Fat is an excellent insulator and can prevent transmural lesion
CR IP T
formation if not removed. Blunt dissection is used to develop the space between the right
superior pulmonary vein and right pulmonary artery. On the left side, the space between the left superior pulmonary vein and left pulmonary artery should be developed, and the Ligament of Marshall is usually divided with Bovie cautery. Following pulmonary vein dissection, if the
AN US
patient is in atrial fibrillation, attempts should be made to restore sinus rhythm. An IV bolus of amiodarone (150 mg) is given and cardioversion is performed. Pacing thresholds for each pulmonary vein are obtained prior to ablation. The bipolar radiofrequency device is clamped
M
around as large a cuff of atrial tissue surrounding the right pulmonary veins as possible. Radiofrequency energy is delivered until the algorithm confirms transmurality. An additional
ED
ablation is performed prior to unclamping the device. Following the initial two ablations, the device is unclamped and moved a few millimeters proximally or distally and reclamped to
PT
perform a second set of ablations. Three sets of ablations are performed on the pulmonary veins,
CE
and for all other lesions of the CMP-IV. Pacing is then performed from the pulmonary veins at
AC
20 mA to confirm exit block.
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Figure 3. Left Pulmonary Vein Isolation After completion of the right pulmonary vein isolation, the left pulmonary veins are isolated in a similar fashion with the bipolar radiofrequency device. The right and left pulmonary vein
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isolations are performed with the heart beating at normothermic temperatures. In patients with large pulmonary veins it may be necessary to clamp the superior and inferior veins separately. Electrical isolation is confirmed by documenting exit block from both the superior and inferior
AN US
pulmonary veins. Further ablations may be necessary until there is documented conduction block.
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Figure 4. Right Atrial Lesion Set: Right Atrial Appendage Following pulmonary vein isolation, the right atrial lesion set is performed on the beating heart.
ED
The patient is cooled to 34ºC. A small purse-string suture is placed at the base of the right atrial appendage. The purse-string should be sutured wide enough to accommodate the lower jaw of
PT
the bipolar RF clamp. The clamp is positioned through the purse-string and directed down the
AC
CE
aortic side of the right atrial appendage to perform the right atrial free wall ablation.
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Figure 5. Right Atrial Lesion Set: Vertical Atriotomy and Intercaval Ablation A vertical right atriotomy is performed extending from just above the interatrial septum midway between the superior and inferior vena cava up toward the acute margin of the heart near the
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atrioventricular groove. From the inferior aspect of the atriotomy, the RF clamp is used to create ablation lines up to the superior vena cava and down to the inferior vena cava.
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Figure 6. Right Atrial Lesion Set: Tricuspid Annulus Ablation From the superior aspect of the atriotomy, a linear cryoprobe is used to perform an endocardial ablation extending down towards the tricuspid annulus at the 2 o’clock position. A second endocardial ablation is performed through the purse-string at the base of the right atrial appendage, extending down to the tricuspid annulus at the 10 o’clock position. The endocardial
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cryoablations are performed for 3 minutes at a temperature of -60ºC. A retrograde cardioplegia
ED
cannula is positioned in the coronary sinus under direct vision and secured with a purse-string
PT
suture. The right atrium is closed with a running 4-0 Prolene suture.
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Figure 7. Left Atrial Lesion Set: Left Atrial Appendage On completion of the right atrial lesion set, the heart is arrested using cold-blood cardioplegia
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and the aorta is cross-clamped. The heart is retracted to expose the left atrial appendage. The left atrial appendage is amputated, leaving a 1-2 cm cuff of atrial tissue at the base. A connecting lesion is created with the RF clamp that extends through the amputated appendage into the left superior or inferior pulmonary vein, crossing the previous ablation line. The left atrial appendage is subsequently oversewn with 4-0 Prolene suture in 2 layers. The coronary sinus is marked with
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methylene blue between the terminal branches of the circumflex and the posterior descending coronary arteries.
Figure 8. Left Atrial Lesion Set: Atriotomy and Box Pulmonary Vein Isolation A standard left atriotomy is performed below the interatrial groove and extended inferiorly
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around and behind the right inferior pulmonary vein. The bipolar RF clamp is positioned at the inferior aspect of the left atriotomy and an ablation line is created across the floor of the left atrium into the left inferior pulmonary vein. From the superior aspect of the left atriotomy, the RF clamp is used to create an additional ablation line across the roof of the left atrium into the
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left superior pulmonary vein. The “box lesion” completely isolates the entire posterior left atrium and all four pulmonary veins.
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Figure 9. Left Atrial Lesion Set: Mitral Valve Annulus The bipolar RF clamp is used to create an ablation line from the inferior aspect of the atriotomy
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and directed across the floor of the left atrium towards the mitral valve annulus. This ablation line crosses the coronary sinus, which was previously marked with methylene blue. A 15 mm
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bell-shaped cryoprobe is used to create an endocardial ablation to connect this lesion to the
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mitral valve annulus.
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Figure 10. Left Atrial Lesion Set: Left Atrial Isthmus The left atrial lesion set is completed by performing epicardial cryoablation over the coronary sinus. A linear cryoprobe is placed along the epicardial surface and in line with the previously performed endocardial ablation. A left ventricular (LV) vent is placed through the right superior pulmonary vein. The left atriotomy is closed with a running 4-0 Prolene suture. The patient is weaned from cardiopulmonary bypass and the sternotomy is closed in a standard fashion.
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Short Closing Section Post-Operative Care The successful completion of the CMP-IV requires effective post-operative care, most importantly the monitoring of post-operative arrhythmias. The epicardial pacing wires that are
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sewn to the right atria and ventricle prior to closure of the chest are used to pace the atria at a rate of 80 to 100 beats per minute if needed. Frequent interrogation of the underlying electrical
activity is performed. Junctional rhythms are most commonly seen post-operatively after CMPIV. In the event heart block develops, the pacer can be changed to AV sequential pacing [dual-
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chamber (DDD) mode] to optimize cardiac function. Patients are started on antiarrhythmic
medications once they return to normal sinus rhythm. Patients with persistent bradycardia due to a junctional rhythm are followed for 5-7 days to allow for sinus node recovery. It is important to avoid antiarrhythmic drugs and beta-blockers in these patients. If they remain in a symptomatic
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bradycardia after this time, a dual chamber pacemaker is inserted. In patients with complete heart
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block, pacemaker insertion is usually performed after a waiting period of 5 days. Unfortunately, 5% of patients require permanent pacemaker placement due to persistent heart block or sinus
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node dysfunction after a lone CMP-IV, which increases in the elderly population.10 Atrial tachyarrhythmias (ATAs) may occur post-operatively, but usually resolve within the first month
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after the operation. Patients with persistent ATAs receive pharmacologic treatment with class 1
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or 3 antiarrhythmic drugs (AAD), as well as cardioversion if necessary. The final post-operative consideration is starting anticoagulation therapy. All patients receiving CMP-IV and without contraindications are started on Warfarin or a novel anticoagulant agent post-operatively and continued for 3-6 months. Anticoagulation can be discontinued when the patient is demonstrated to have not experienced ATAs off antiarrhythmic medications as seen on prolonged monitoring
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(24-hour or greater Holter monitor recording), and showed no atrial stasis or thrombus on echocardiography.
Surgical Results The CMP remains the most successful method of terminating ATAs and is the gold standard in
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the surgical treatment of AF. Outcomes of the CMP-IV have shown 91% of patients were free from ATAs at six months in a single-center study, while a more recent prospective cohort study of 100 patients undergoing stand-alone CMP-IV showed freedom from AF of 93%, 90%, and 90% at 6, 12, and 24 months, respectively.11,12 At long term follow-up, Ad et al. reported
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freedom from ATAs of 88% and 85% at 2 and 5 years, respectively.13 These results were similar to the experience at our institution that reviewed 576 consecutive patients undergoing CMP-IV between January 2002 and September 2014. In that study, twelve month freedom from ATAs
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was 93%, with 85% of patients free from antiarrhythmic drugs. At five years the freedom from ATAs was 78%, with 66% of patients free from AAD. The study showed no difference in
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freedom from ATAs off AAD at any time point between patients with paroxysmal or persistent
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AF.14
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Minimally invasive techniques remain the future of cardiac surgery, and have been shown to lower complication rates and overall hospital costs without compromising results.15 Though
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median sternotomy for CMP-IV remains highly effective, advancements in surgical ablation technology have allowed for a less invasive approach. A minimally invasive operation through right mini-thoracotomy (RMT) for CMP-IV reduces overall morbidity and operative risk, as well as cardiopulmonary bypass and aortic cross clamp time compared to median sternotomy.16 The RMT approach has showed similar success in the treatment of AF, and is our approach of choice
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for a stand-alone procedure. A retrospective review conducted of 365 patients at our institution undergoing CMP-IV found 79% freedom from ATAs and AADs at two years follow-up through sternotomy approach, compared to 74% for RMT. The RMT group had significantly less major complications compared to sternotomy group (6% vs 13%, P=0.04).16 Further work must be
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done to increase the number of patients undergoing surgical treatment of AF, especially in the setting of concomitant procedures. In conjunction with the improvement of surgical ablation technology, a greater understanding of the mechanisms underlying the development of atrial
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fibrillation would allow for more tailored lesions sets to more efficiently treat patients with AF.
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References 1. Cox JL, The surgical treatment of atrial fibrillation. IV. Surgical technique. J Thorac Cardiovasc Surg 1991;101:584-92. 2. Cox JL, Boineau JP, Schuessler RB, et al. Successful Surgical Treatment of Atrial Fibrillation: Review and Clinical Update. JAMA. 1991;266(14):1976–80. 3. Cox JL, Schuessler RB, D’Agostino HJ Jr, et al. The surgical treatment of atrial fibrillation, III: development of a definitive surgical procedure. J Thorac Cardiovasc Surg. 1991;101:569-83. 4. Cox JL, Ad N, Palazzo T, Fitzpatrick S, Suyderhoud JP, DeGroot KW et al. Current status of the Maze procedure for the treatment of atrial fibrillation. Semin Thorac Cardiovasc Surg 2000;12:15–9. 5. Melby SJ, Schuessler RB, Damiano RJ. Ablation technology for the surgical treatment of atrial fibrillation. ASAIO J. 2013;59(5):461-8. 6. Badhwar V, Rankin JS, Damiano Jr RJ, Gillinov AM, Bakaeen FG, Edgerton JR, et al. The Society of Thoracic Surgeons 2017 Clinical Practice Guidelines for the Surgical Treatment of Atrial Fibrillation. Ann Thorac Surg 2017;103:329–41. 7. Calkins H, Hindricks G, Cappato R, et al. 2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation. Europace. 2017;20(1):e1-e160. 8. Ad N, Damiano RJ Jr, Badhwar V, Calkins II, La Meir M, Nitta T, et al. Expert consensus guidelines: examining surgical ablation for atrial fibrillation. J Thorac Cardiovasc Surg. 2017;153:1330-35.e1. 9. Ruaengsri C, Schill MR, Khiabani AJ, Schuessler RB, Melby SJ, Damiano RJ, Jr. The Cox-maze IV procedure in its second decade: still the gold standard? European Journal of Cardiothoracic Surgery. 2018;53(suppl_1):i19-i25. 10. Robertson JO, Cuculich PS, Saint LL, et al. Predictors and risk of pacemaker implantation after the Cox-Maze IV procedure. Ann Thorac Surg 2013;95:2015-20. 11. Gaynor SL, Diodato MD, Prasad SM, Ishii Y, Schuessler RB, Bailey MS et al. A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation. J Thorac Cardiovasc Surg 2004;128:535–42. 12. Weimar T, Bailey MS, Watanabe Y, Marin D, Maniar HS, Schuessler RB et al. The Coxmaze IV procedure for lone atrial fibrillation: a single center experience in 100 consecutive patients. J Interv Card Electrophysiol 2011;31:47–54. 13. Ad N, Holmes SD, Stone LE, Pritchard G, Henry L. Rhythm course over 5 years following surgical ablation for atrial fibrillation. Eur J Cardiothorac Surg 2015;47:52–8. 14. Henn MC, Lancaster TS, Miller JR, Sinn LA, Schuessler RB, Moon MR et al. Late outcomes after the Cox maze IV procedure for atrial fibrillation. J Thorac Cardiovasc Surg 2015;150:1168–76, 1178.e1–2. 15. Schmitto JD, Mokashi SA, Cohn LH. Past, present, and future of minimally invasive mitral valve surgery. J Heart Valve Dis 2011;20(5):493-8. 16. Lawrance CP, Henn MC, Miller JR, Sinn LA, Schuessler RB, Maniar HS et al. A minimally invasive Cox maze IV procedure is as effective as sternotomy while decreasing major morbidity and hospital stay. J Thorac Cardiovasc Surg 2014;148:955– 61; discussion 62–2.
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