Clauden Louis, MD, Daniel Ryan Ziazadeh, MD, Peter Knight, MD
Concept
- Subtypes
- Paroxysmal Atrial Fibrillation (PAF)
- AF intermittently with each episode less than 1 week
- Non-Paroxysmal Atrial Fibrillation (NPAF)
- Persistent AF – lasting longer than 1 week
- Longstanding Persistent AF – continuous AF of greater than 1 year
- Permanent AF – AF that cannot be electrically cardioverted
- Surgical pitfalls and indications for ablation
Key terms: Non-Paroxysmal Atrial Fibrillation (NPAF), Paroxysmal Atrial Fibrillation (PAF), MAZE, Cryoablation, Radiofrequency Ablation
Chief complaint
A 61-year-old female with long-standing atrial fibrillation following failed EP ablations presents for further evaluation and consultation regarding definitive management of her arrhythmia.
Differential
Non-Paroxysmal Atrial Fibrillation (NPAF), Paroxysmal Atrial Fibrillation (PAF), Premature atrial contractions, Premature ventricular contractions, Atrial Flutter
History and physical
Any patient being considered for arrhythmia surgery needs to have a comprehensive system-based history and physical to identify history of stroke, renal disease, coronary lesions, respiratory problems, bleeding disorders, or peripheral vascular disease. This can usually be performed prior to intervention as arrhythmia surgery is typically an elective procedure. Concomitant cardiac comorbidities must be ruled out.
Tests
- Biochemical Profile (CMP, LFTs)
- CBC
- Cardiac Enzymes (Troponin, CK, LDH)
- BNP
- EKG
- ECHO (TTE +/- TEE)
- Cardiac catheterization
Index scenario (additional information)
Upon further evaluation of her transthoracic echocardiography, imaging reveals that in addition to long-standing atrial fibrillation she also has severe mitral regurgitation. What is the definitive management available for this patient?
Treatment/Management
- The objective of intervention for AF, either stand-alone or concomitant, depends on whether the patient has PAF or Non-PAF.
- Paroxysmal AF – “Isolate the Triggers.”
- N-PAF – “Interrupt the Drivers.”
- In the treatment of this lesion a Bi-Atrial Maze with LAA ligation should be considered. Bi-atrial MAZE surgical procedures are more effective than left-sided procedures in eliminating AF as the addition of right atrial lesions increase likelihood of normal sinus rhythm. (Barrett et al)., Sole Left-Sided Maze Procedure are incomplete as RA drivers are not intervened upon. Additionally, right-sided ablations are important for the prevention of atrial flutter.
Indications
- Atrial fibrillation resistant to drug Tx
- Intolerance to drug Tx
- Six months of atrial fibrillation w/ enlarged atrium
- High risk for thromboembolism (eg hypercoagulable state)
- Contraindication to anticoagulation
- Patients who have suffered a stroke on Coumadin
Key maneuver is pulmonary vein isolation (majority of atrial fibrillation foci located in pulmonary veins) MAZE can be done off cardiopulmonary bypass (cryolesions, RF ablation)
Success rate – 70%
Contraindications
Relative
- None
Operative steps – Cox Maze IV
**Conduct of operation varies significantly depending on what else needs to be done**
- Aortobicaval cannulation
- Pulmonary Vein Isolation and Ablation (can be done outside the heart using Atricure RF device or inside the heart using cryo).
- Ablation of the right pulmonary veins (RPVs)
- Ablation of the left pulmonary veins (LPVs).
- Must obliterate Ligament of Marshall
- Fetal left SVC that stretches across the base of the LA appendage near the LSPV
- Snare SVC/IVC
- Arrest heart (not mandatory)
- Open left atrial appendage (LAA)
- LAA to left superior vein lesion
- Exclude LAA: clip or surgical ligation
- Left atriotomy
- Construction of the floor lesion of the box
- Construction of the roof lesion of the box
- Coronary sinus lesion
- Mitral valve lesion
- Vertical right atriotomy
- Tricuspid valve lesion
- Superior vena cava lesion
- Inferior vena cave lesion
What is the cryoablation energy source?
- Nitrous Oxide – Atricure (CryoICE)
- Reaches probe temperatures of –600C
- Argon Gas – Medtronic (CryoFlex 10S)
- Reaches probe temperatures of –1500C
- Both devices feature a 10 cm malleable probe with insulation sleeve
What is the purpose of the box lesion?
- Adding the roof and floor lines to create a Box Lesion does two things.
- It isolates 80% of the triggers that induce PAF
- It interrupts at least some of the macro-reentrant circuits that sustain N-PAF
- If a given patient has N-PAF that happens to be sustained by some of the reentrant circuits that are interrupted by the Box Lesion, this alone might cure that patient’s N-PAF.
- This occurs infrequently but may account for the reported 20-45% 5-year success rate of catheter ablation for N-PAF.
Potential Questions / Alternative Scenario
While dissecting the transverse sinus, you inadvertently see a dark collection of blood begin to pool. What have you likely injured?
There is a concern for injury of the right pulmonary artery (RPA).
Potential questions/alternative scenarios
A 61-year-old female with a 7-year history of mitral regurgitation and long-standing atrial fibrillation underwent a concomitant mitral valve repair with ring annuloplasty and a Cox Maze IV procedure with left atrial appendage ligation. She returns 2 weeks later to the clinic with symptoms of palpitation and found to be in atrial flutter with a heart rate of 160 beats/min. What is the likely cause of her symptoms?
“Peri-Mitral Flutter”
Failure to interrupt conduction across the Left Atrial Isthmus allows the development of so-called “Peri-Mitral Flutter”, the most common mode of failure of surgery for AF. This is due to an incomplete lesion line involving the mitral valve annulus. A catheter-based intervention by EP colleagues may assist in completing this ablation line.
- Lesions sets not connected such as transmural ablation of the epicardium and endocardium of the coronary sinus to the level of the mitral annulus can lead to flutter
- A large macro-reentrant circuit develops just above the mitral valve annulus thus it’s important to perform both the mitral line to prevent conduction across the atrial myocardium and the coronary sinus lesion to prevent conduction across the coronary sinus.
- Coronary sinus conduction occurs in a small subsegment of patients. Thus, all patients undergoing arrythmia surgery require ablation to both the mitral isthmus and the coronary sinus lesion. One must collapse the CS during cryoablation, a circumferential lesion can be assured.
- As the CS is collapse an “iceball” is created by the cryoprobe on the epicardium that can also be seen as an “iceball” on the endocardium of the left atrium, as the LA is opened. Preventing postoperative Peri-Mitral flutter is done by placing both the mitral line and the CS lesions in the same plane.
Potential Complications / Alternative Scenarios
While preforming the Cox Maze IV with cryoablation, you notice a cryolesion across the pericardial surface of the right atrium of the heart. What complication can you expect post operatively and how can this mistake be avoided in the future?
- It is wise to protect the right phrenic nerve while performing cryosurgery in either the right or left atrium. The handle of the cryoprobe can sometimes be inadvertently resting on the right phrenic nerve and cause temporary right hemidiaphragm paralysis. Special care should be taken at all times of the procedure to avoid this complication.
Potential Questions / Alternative Scenarios
After completing the Cox-Maze IV, you notice that there is a discontinuous lesion due to a fold in tissue. The cryoprobe is no longer sterile. You determine that the line appears good enough. After rewarming, you notice that the patient is still in A-Fib. Why did the procedure fail?
- The Maze is unforgiving, with even a minor slip in technique. Even a single break in the line can preserve a macro reentry circuit and the entire procedure will fail.
- Incoming waves of atrial activation will find even the slightest break in the line. The lesions must be uniformly transmural (full thickness), and contiguous. Unfortunately, even cryoablation and bipolar RF clamps are not full proof. Gaps in the ablation line create islands of scar that can result in iatrogenic flutter.
- Tissue folding is a sign of poor technique and will always create a line with multiple breaks. The clamp will only ablate through the folded section, creating an air tissue interface in the unfolded sections with no contact or ablation.
Potential questions/alternative scenarios
Instead of using the cryoprobe for pulmonary vein isolation in a patient with PAF, you have selected the Atricure Synergy Bipolar RF clamp. You believe that you have effectively created contiguous, transmural lines of ablation. However, after rewarming, you again notice the patient is in A-Fib. Your scrub tech notices some char on the clamp but does not mention it to you. Why did the procedure fail?
- Effective operation of the RF clamp depends on perfect contact between the tissue and the electrodes. Char is an isolator that disrupts this contact and prevents the underlying tissue from appropriately heating. A break in the line, will render the procedure ineffective.
- Surgeons may sometimes confuse char as a sign of high heat reaching the tissue surface, but this is incorrect. The surgeon and scrub tech must be vigilant in removing char from the clamp. It is recommended to clean the clamp after every three ablations. Repeated ablation over an area of char will just produce more char.
Potential questions/alternative scenarios
After cannulation, normothermic cardiopulmonary bypass is instituted prior to left pulmonary vein isolation. The heart is retracted to the patient’s right to expose the left atrial appendage and left pulmonary veins. When this retraction is performed, the Ligament of Marshall is stretched taught and is easily identified near the left superior pulmonary vein. The ligament is divided with a cautery. Immediately afterwards, a device is seen protruding through the left atrial appendage.
- Although very rare, the exposure required for Ligament of Marshall may compromise the position of the LV Vent. It is necessary to expose and divide the Ligament of Marshall to obtain passage behind the left pulmonary antrum for left sided pulmonary vein isolation.
Potential questions/alternative scenarios
After completing the Cox Maze IV with placement of the AtriClip, you come off cardiopulmonary bypass. The anesthesiologist notices a small pouch with clot in the appendage. What is the likely cause of this problem?
- The Atriclip was likley not placed at the base of the appendage. The Atricure AtriClip is a left atrial appendage exclusion system that is indicated for occluding the left atrial appendage and creating a left atrial appendage line that circles around the conical structure of the base of the appendage. It should be placed under direct visualization and in conjunction with other cardiac surgical procedures. Direct visualization requires the surgeon to be able to see the heart directly with or without camera assistance.
- Improper placement will leave behind a small pouch that is often a source of thrombus. Alternative techniques include left atrial appendage amputation that was traditionally one of the remaining cut and sew lesions in the Cox Maze IV. In rare circumstances, amputation can lead to bleeding through the suture line or from tributaries at the AV grove near the coronary sinus from improper dissection.
- Amputation will remove many of the potential macro reentry circuits but not the ones at the base. If amputation is preferred, the base needs to be anchored to the left pulmonary vein isolation.
- One advantage of placing the clip on the LAA at this juncture is that you can visualize your isolation from the inside of the left atrium during concomitant mitral valve surgery.
Potential Questions / Alternative Scenarios
In the above scenario, following securing of the AtriClip or amputation of the LAA, the patient is noted to have EKG changes with T-wave inversions in the lateral leads. What are your concerns?
- There is likely inadvertent injury to the left circumflex coronary artery causing myocardial infarction at the time of LAA isolation.
- Normally, the LAA orifice is at the level of the frenulum between the left pulmonary vein orifices and it is located several centimeters from the mitral valve annulus. In addition, the circumflex coronary artery is normally located far away from the LAA orifice in the AV groove near and slightly below the coronary sinus.
- In some patients, the LAA orifice is located nearer the MV annulus and is in the plane of the LIPV orifice. In addition, the proximal circumflex coronary artery, or just one segment of it, can lie unusually close to the base of the LAA.
- For the high lying LCX, this close juxtaposition of the proximal LCX with the LAA can pose a danger when closing the LAA from the endocardium. The position of the circumflex cannot be seen from the endocardial view. In the situation described here, it is likely that the LAA orifice is unusually low and the circumflex is unusually high, setting up a potential for injury.
Potential questions/alternative scenarios
After completion of the classic right atrial appendage line, you come off cardiopulmonary bypass and notice that the patient is in complete heart block. What caused this?
- The only remaining place in the right atrium where a macro-reentrant circuit can form is around the base of the RA appendage.
- While damage to the AV node during the Maze procedure is nearly impossible, this is the one line in which it can occur. If the cryoprobe is positioned too posteriorly, it can inadvertently damage the pacemaker complex and result in permanent pacemaker dependency.
- The SA node can also be injured. To prevent this from occurring, the final RA lesion is placed from the distal end of the vertical atriotomy to the tip of the RA appendage. It is extremely important to place this lesion as far anteriorly as possible to avoid injury of the pacemaker complex.
- The modified RAA line has been advocated as a simpler, safer, and faster approach to accomplish the same results. It consists of the vertical atriotomy and IVC line segment and anchor to form a line from the IVC to the tip of the RAA.
Potential questions/alternative scenarios
“A 57-year-old woman with a history of obesity and atrial fibrillation (AF) was treated initially with antiarrhythmic medications and was not compliant due to the side effects. She underwent 2 catheter ablations for persistent afib with a short period of relief but now returns with recurrent palpitations, generalized weakness and dizziness for more than a week. It has been 4 months after catheter ablation and the cardiology refers her to you for a surgical alternative?”
Differential
The diagnosis was established initially by the cardiologist. Recognizing other associated diseases will be important for planning surgical interventions. Also, review the EKG carefully to ensure that the rhythm is labelled correctly.
History and physical Attempt to determine the pattern of afib (paroxysmal – spontaneous conversion, recurrent – requires ECV/antiarrhythmics or persistent), medications (anticoagulation, antiarrhythmics), and complications of afib (stroke, peripheral emboli). Identify signs and symptoms of diseases that predispose to a high recurrence rate after catheter ablation: hypertension, hypercholesterolemia, persistent AF, or obstructive sleep apnea. Predisposing factors include age, male sex (because of the tall stature), hypertension, hyperthyroidism, chronic kidney disease, alcohol, PE, obesity (BMI > 30 kg/m2) and family history. Ask about any known ischemic or valvular issues.
Tests
- Labs: CBC, BMP, Coags.
- 12 lead EKG to establish the rate and rhythm.
- 24 Holter monitoring especially if the patient is currently in sinus rhythm.
CT scan or MRI: pulmonary vein protocol in patients with a failed catheter ablation (to rule out pulmonary stenosis).
Echo: complete valvular assessment, septal anatomy, right and left function, and left atrial size. Severely dilated left atrium decreases the likelihood of achieving sustained sinus rhythm.
Left heart catheterization: for IHD and for establishing coronary anatomy (left dominant patients are at slightly increased risk of injury to their coronary arteries while ablating close to the coronary sinus).
Electrophysiological mapping: which utilizes the combination of pace/anatomic/activation mapping to identify potential sites for ablation.
Index Scenario (additional information)
“The patient has normal electrolytes, no valve abnormalities and evidence of persistent afib on 24-hour holter monitoring with a rate between 70 and 90. Her cardiac catheterization is normal.”
Index scenario (additional information) “The patient has normal electrolytes, no valve abnormalities and evidence of persistent afib on 24-hour holter monitoring with a rate between 70 and 90. Her cardiac catheterization is normal. “Treatment/management Indications for catheter or surgical ablation include paroxysmal (PAF), persistent or recurrent AF in patients who do not tolerate or have failed antiarrhythmics. Catheter ablation is usually attempted first once or even twice prior to referral for surgery unless the patient is undergoing surgery for a concomitant lesion. This patient has failed medical and catheter-based interventions and is thus a candidate for standalone surgical ablation. Options include pulmonary vein isolation (works well for PAF), or Cox MAZE IV (cut and sew or the modified ablation protocol). For this patient Cox MAZE IV will give her the greatest chance of sinus rhythm control.
Potential questions/alternative scenarios
“A 65 year-old female with a history of PAF is undergoing an AVR and is noted to have PAF.”
This is an excellent indication for pulmonary vein isolation (PVI). PVI can be used as a standalone procedure for PAF especially in patients with comorbidities who need a limited operation. However, it is not as complete as the Cox Maze IV and is not as successful for persistent or recurrent AF. PVI is very often used for PAF in patients undergoing valve surgery with good results.
Pulmonary venous isolation (PVI)Median sternotomy, aortic and single stage venous cannulation. Initiate CPB and perform the right sided lesions first. Right sided lesions: carefully get around the right superior pulmonary vein (RSPV) and right inferior pulmonary vein (RIPV) with blunt and sharp dissection. Stay away from the phrenic nerve. The bipolar RF jaws are inserted around the right sided pulmonary veins and then clamped on the atrial tissue to avoid pulmonary vein stenosis.
Left sided lesions: now arrest the heart and get around the left sided pulmonary veins in a similar fashion. Identify and divide the ligament of Marshall. Here you must make sure that you are away from the circumflex artery on the AV groove when clamping on the left atrial tissue. Excise/ligate LAA: excise and suture or occlude the LAAL with a variety of commercially available devices. Perform the AVR. “A 58-year-old male is undergoing a mitral valve repair and has a history of PAF.” For this patient the PVI is best performed when the left atrium is opened with a single cryoablation catheter. Bipolar devices can be used for the inferior and superior connecting lesions to prevent injury to the esophagus. But remember to excise or exclude the LAA prior to repairing or replacing the mitral valve. You do not want to lift on the heart after the mitral is completed due to the potential for AV groove disruption. “The same patient has a history of persistent afib.” There are a few different ways to do this. It is reasonable to plan for left and right sided lesions (Cox Maze IV) as well as LAAL as described above. Make the left atriotomy through Sondergaard’s groove, address the left sided lesions, LAAL, repair/replace the valve and make a separate right atriotomy for the right sided lesions. Alternatively, perform the mitral through a transseptal incision. The one risk with the transseptal is that if the mitral exposure is not great and you need an extended transseptal then you risk injury to the artery supplying the SA node.
Potential questions/alternative scenarios
“A 59-year-old diabetic, hypertensive male patient with chronic kidney disease is suffering from persistent atrial fibrillation. She had an intracranial bleed while on warfarin and other class 1 and 3 anti arrhythmics. How would you proceed?”
This patient is at increased risk of intracranial hemorrhage with CPB. Thus, catheter ablation with best medical management may be her best option. “On electrophysiologic mapping a patient is a suitable candidate for minimally invasive PVI, but a thrombus is discovered intraoperatively on
TEE, how will you proceed?”
The minimally invasive PVI will be converted to an open procedure.
Potential questions/alternative scenarios
“A 57-year-old obese, female who is a known case of atrial fibrillation (AF) was treated initially with antiarrhythmic drugs and she was non-compliant due to the side effects, this was followed by a catheter ablation procedure but she is still having occasional palpitations 2 months after catheter ablation?”
If she is highly symptomatic and antiarrhythmics are not effective or tolerated a second attempt at catheter ablation after careful electrophysiologic mapping can be attempted. If this fails wait for 3 months and proceed with surgical management.
Pearls/pitfalls
- Dissecting transverse sinus RPA
- Lesions sets not connected (CS epi and endo) to mitral annulus can lead to flutter
- Phrenic nerve to cryoablation
- Discontinuous lesions due to fold in tissue
- Discontinuous lesion due to char on bipolar clamp (measuring tissue impedance and there is no conduction)
- LV vent prior to LPV isolation
- LAA not on base
- Oversew LAA hitting or injuring circumflex
- Pacemaker complex right atrial appendage
Critical Errors
- Avoid placing an ablation line through the Sinus Tachycardia site at the right atrium. This can lead to an inability to generate an appropriate sinus tachycardia response to normal exercise. This was a common complication of Maze-I procedure with 30% of patients unable to generate a heart rate above 100-110.
- Avoid transection of Bachmann’s Bundle, both medial and superior to the roof lesion as this will delay the arrival of a sinus impulse from the RA to the LA.
- Avoid “Flutter Line” or “Isthmus Lesion” across the cavo-tricuspid isthmus (CTI) as this will result in the inability to develop an appropriate bradycardia when one is asleep.
Guidelines
2017 STS Guidelines on Surgery for Atrial Fibrillation
Adding AF surgery does not affect operative morbidity
- Class Ia, Level B
Adding AF surgery does not affect operative mortality
- Class I, Level A
2017 AATS Guidelines on Surgery for Atrial Fibrillation
Adding AF surgery does not affect operative morbidity
- Class IIa, Levels A, B-R, B-NR
Adding AF surgery improves operative mortality
- Class I, Level A
Suggested readings
- Philpott JM., et al. Surgical Treatment of Atrial Fibrillation: A Comprehensive Guide to Performing the Cox Maze IV Procedure. Academic Press, 2017.
- Badhwar V, Rankin JS, Ad N, Grau-Sepulveda M, Damiano RJ, Gillinov AM, McCarthy PM, Thourani VH, Suri RM, Jacobs JP, Cox, JL Surgical ablation of atrial fibrillation in the United States: Trends and Propensity Matched Outcomes. Ann Thor Surg, (August) 2017;104:493-500
- Barnett SD, Ad N. Surgical ablation as treatment for the elimination of atrial fibrillation: a meta-analysis. Journal of Thoracic and Cardiovascular Surgery, 2006 May;131(5):1029-35.
- Cullen MW, Stulak JM, Powell BD, White RD, Ammash NM, Nkomo VT. Left Atrial Appendage Patency at Cardioversion After Surgical Left Atrial Appendage Intervention. Ann Thor Surg, 2016;101(2):675-681.
- Forlani S, De Paulis R, Guerrieri WL, Greco R, Polisca P, Moscarelli M, Chiariello L.Conversion to sinus rhythm by ablation improves quality of life in patients submitted to mitral valve surgery. Ann Thor Surg, 2006;81(3):863-867
- Melo J, Santiago T, Aguiar C, Berglin E, Knaut M, Alfieri O, Benussi S, Sie H, Williams M, Hornero F, Marinelli G, Ridley P, Fulquet-Carreras E, Ferreira A. Surgery for atrial fibrillation in patients with mitral valve disease: Results at five years from the International Registry of Atrial Fibrillation Surgery. J Thor Cardiovasc Surg, 2008;135(4):863-869
