The Cox-Maze & Mini-Maze Surgeries and the Hybrid Surgery/Ablation

 Cox-Maze Surgeries

Developed by Dr. James Cox in 1987, the Cox Maze operation was the first treatment that made patients A-Fib free. In the Cox-Maze open heart “cut and sew” operation, the surgeon made numerous incisions in your atria. This “maze” of incisions divided your atria into electrically isolated segments, thereby blocking the electrical impulses that cause A-Fib from spreading throughout the heart. The atria continued to be activated by a regular signal from the sinus node.

The left atrial appendage is usually removed during this operation.

Dr. Cox developed a successor to the Cox Maze III called a “Radial Maze.” (also see 2006 BAFS: Dr. David Kess “Advances in Surgical Therapy for A-Fib.”)

In a later version of the operation, the Cox Maze IV, most of the “cut and sew” incisions are replaced with linear ablation lesions created either with radiofrequency energy or cryothermy (freezing).^1,2Access to the heart on pulmonary bypass can be through the sternum (breast bone) or through incisions in the chest. If access is through the chest, Dr. Damiano, Jr. calls it a Minimally Invasive Cox-Maze IV.

The Cox Maze IV operation does work and has a high success rate (“approximately 75% at two years”) but it hasn’t been used often because of the risks of open heart surgery, the danger of bleeding from the incisions, the pain, discomfort and prolonged convalescence from the operation, and the resulting reduced atrial function due to the incisions/lesions. (Voltage mapping of post-Maze patients may show that their left atrium has reduced or is entirely devoid of electrical activity because of the extensive scarring.)

According to Surgeon A. Mark Gillinov of the Cleveland Clinic, having the Maze surgery alone generally should be done only after other therapies have been tried.³

However, if you have to undergo open heart surgery for another heart problem, you may want to go to a heart center that can perform the Cox Maze operation at the same time.

Note: If you have a left atrium larger than 6.0 cm or if you’ve been in A-Fib for over five years, the long term success of the “Cut and Sew” Maze operation is lower, under 80%.⁴

For more about the Cox Maze and Mini-Maze surgeries, you may want to read Boston AFib 2006/Advances in Surgical Therapy for A-Fib by Dr. David C. Kress.

 Mini-Maze Operations

In newer maze operations surgeons do not crack open the breastbone and stop the heart while putting the patient on a heart-lung machine as in the Cox Maze operation.

Instead the surgeons cut keyhole-sized incisions on the sides of the chest or go through the diaphragm to gain access to the heart. Using a tiny video camera the surgeons loop a bipolar clamp catheter around the outside of the heart. Each lung is temporarily deflated in turn to allow the bipolar clamp to be threaded around the pulmonary veins. The bipolar clamp creates lesions around the atrium cuff of the pulmonary veins that scar and block the electrical impulses causing the irregular heartbeat.⁵

Though not open heart surgery like the Cox Maze III (Radial Maze), the Mini-Maze operations are nevertheless very traumatic for the body and require general anesthesia.

To be effective the ablations (lesions, burns) have to be transmural; i.e., they have to penetrate all the way from the outside of the heart to the inside. But the inside of the heart varies in thickness, has ridges, etc. And epicardial (outside the heart) fat can also prevent transmurality. Even bipolar RF burns cannot guarantee transmural lesions.⁶ “Transmurality of a lesion set cannot be guaranteed with current ablation catheters on the beating heart.”⁷ Also, proving or confirming bidirectional block from outside the heart can be challenging.⁸

If you have a simple case of recent onset A-Fib that requires only the isolation of the Pulmonary Vein openings, the Mini-Maze operation may work for you.

The biggest drawback to Mini-Maze operations is that they can’t currently reach or isolate all areas of the heart where A-Fib signals may originate. If you have a simple case of recent onset A-Fib that requires only the isolation of the Pulmonary Vein openings, the Mini-Maze operation may work for you. But anything more complicated is questionable. Currently surgeons don’t have the ability to map inside the heart to identify sites where A-Fib originates. For example, patients with long-standing persistent (complicated) A-Fib tend to have relatively poor results. One study cites a 46.2% success rate after three months.⁹(In contrast, Dr. John Sirak, inventor of the Five Box Totally Thorascopic Maze surgery, reports a 91% success rate.)¹⁰

One considered advantage of the Mini-Maze operations is that the Left Atrial Appendage is cut out, stapled shut or closed off. Most A-Fib blood clots which cause stroke come from the Left Atrial Appendage (more on this topic further down the page). See https://a-fib.com/left-atrial-appendage-role-and-removal-issues/ 

VIDEO 1: Inside the O.R. for a Mini-Maze Surgery. Dr William Harris, cardiovascular surgeon, describes what he refers to as a mini-maze procedure, the minimally invasive Lone Atrial Fibrillation Ablation. Posted by Baptist Medical Center in Jackson, Miss. (4:49 min.)

Is Mini-Maze Overkill For Paroxysmal A-Fib?

Patients may ask if a Mini-Maze surgery is overkill for simple cases of Paroxysmal (occasional) A-Fib. Some surgeons would agree.

Surgeon Andy C. Kiser says about his practice, “when a patient has paroxysmal A-Fib and the left atrium is under 4.5-5.0 cm, we recommend percutaneous (through the skin) catheter ablation. In this population, simple pulmonary vein isolation may be effective in over 80% of patients.“^11,12

Surgeon James Edgerton does not normally perform surgery on Paroxysmal (Occasional) A-Fib patients. “I think they are very well treated with catheter ablation.” (See surgeon James Edgerton’s presentation Boston AF 2011/Hybrid Ablation.)

Maze Surgery is Recommended in Some Cases

In general, Maze surgical treatments for A-Fib are not recommended as a first choice or option by current guidelines. They are generally more invasive, traumatic and risky than catheter ablation.

Surgery, however, is recommended if one can’t tolerate blood thinners or if one is “morbidly obese.” With current imaging systems, it’s more difficult to see a clear image of the heart during a catheter ablation if someone is significantly overweight. Also, a Mini-Maze might be a better option is you’ve already had a stroke and are more in danger of having a stroke during a catheter ablation. And if you have to have a heart operation to, for example, fix a heart valve, the surgeon can often do a Maze operation at the same time.

Mini-Maze Risks

Mini-Maze surgeries “usually have significant risks compared with catheter-based electrophysiology procedures such as catheter ablation.”¹³ A study comparing catheter versus surgical ablation found that Mini-Maze surgeries had about a one in four chance of a major adverse event.¹⁴

Since 2008, there have been at least five U.S. patient deaths reported to an FDA database in A-Fib surgeries using AtriCure devices and one involving a Medtronic device. (That database doesn’t prove that the devices caused the deaths.) According to Thomas M. Burton of the Wall Street Journal, currently (2010) “there are no large studies comparing the safety of surgical ablation to that of other ways to treat A-Fib.”¹⁵ 

Mini-Maze-type surgeries can also be very painful, including ongoing numbness and phantom pain at chest access sites.

In addition, deflating and re-inflating the lungs can be very difficult particularly for older people whose lungs are no longer very elastic. Possible complications include but are not limited to pericardial effusion, pleural effusion, pneumothorax (collapsed lung), herniated lung, heavy coughing, bronchitis, and pneumonia.

And approximately 6% of patients may require a pacemaker.”¹⁶

In a very unscientific survey at one center, when patients were asked whether or not they would undergo a Mini-Maze surgery again, 50% said no way, 30% said it was a lot harder than they thought it would be, but 1 out of 5 said it was worth it.

When patients were asked whether or not they would undergo a Mini-Maze surgery again, 50% said no way, 30% said it was a lot harder than they thought it would be, but 1 out of 5 said it was worth it.

Extent of Scarring of the Left Atrium

Scarring in the heart permanently damages heart tissue and is usually avoided unless absolutely necessary. Circulation, nerve signal pathways, heart muscle fibers, transport function, the ability of the left atrium to contract, etc. may be affected. This is irreversible heart damage. Non-contracting scar tissue replaces normal heart muscle. This may weaken the heart and may later contribute to heart problems like congestive heart failure. Millions of patients today suffer from weak hearts due to heart muscle damage.

These ablation burns are normally not a problem in the Pulmonary Vein areas which function as pipes into the left atrium, but may be a problem in areas of the left atrium more involved in heart function and contraction.

Newer Mini-Maze surgeries, such as the Wolf Mini-Maze, Totally Thoracoscopic (TT) Maze, the Five-Box Thorascopic Maze Surgery, the Dallas Lesion Set, and the Biatrial Maze are one-size-fits-all surgeries which create a specific pattern of ablation lines/burns on the left atrium. But we don’t know if this scarring is necessary or appropriate for all cases of A-Fib. (The Wolf Mini-Maze name suggests it is related to the Maze operation. But it has nothing to do with the concept of using a maze pattern of lesions to treat A-Fib. It only isolates the PVs and removes the Left Atrial Appendage.)

Questions for your surgeon: Patients should ask their surgeons if this scarring of the left atrium is necessary to fix their type of A-Fib. And ask, Would a Pulmonary Vein Ablation procedure, for example, fix their A-Fib without the added risks of heart surgery and permanent heart damage?

For more about the Cox Maze and Mini-Maze surgeries, you may want to read Boston AFib 2006/Advances in Surgical Therapy for A-Fib by Dr. David C. Kress.

To help you select a cardiologist, electrophysiologist or surgeon:
• see Questions for Doctors (and What the Answers Mean)
• download our free ‘Questions for Doctors Worksheet’ (in PDF format).
• see our ‘Questions for Surgeons’ in our book, Beat Your A-Fib: The Essential Guide to Finding Your Cure by Steve S. Ryan, PhD.

 The Hybrid Surgery/Ablation

Relatively new is the Hybrid Surgery/Ablation in which a surgeon and a cardiac electrophysiologist (EP) team up to work together on the same patient.¹⁷ The genius of the Hybrid approach seems to be its complementary nature: the surgeon works on the outside the heart and the EP on the inside of the heart. (Similar multidisciplinary ablation techniques are called ‘hybrid ablation technique’, ‘convergence process’, ‘Convergent Maze Procedure’ and ‘Convergent Ablation”’.)

The surgeon working on the outside of the heart can produce visible linear lesions much easier on the smooth outside surface of the heart than the EP working on the inside of the heart with point-by-point catheter ablations. The EP working inside the heart, on the other hand, is better equipped to tell if a surgical lesion is effective or not. They can then detect any gaps and correct them with catheter ablation. For example, if the surgeon’s “entrance and exit block lesions” were incomplete, the EP can identify the conduction gaps and ablate them.

To eliminate all A-Fib signals, “the goal is to treat the full thickness of the tissue,” says Dr. Paul Wang of Stanford Hospital & Clinics.¹⁸ According to Dr. Laurent Pison of The Netherlands, “in almost a quarter of patients, catheter ablation [is] needed to finish incomplete epicardial [outside the heart] surgical lesions by endocardial [inside the heart] touch-up.”¹⁹ Endocardial catheter touch-up is often necessary to achieve bidirectional block of the pulmonary veins (in about a third of patients), but even more so in the box (roof and floor) surgical lesions (about two-thirds of patients).²⁰

Also, the EP can ablate in areas surgeons currently can’t reach such as making a Caviotricuspid Isthmus line in the right atrium to stop Atrial Flutter. In addition, the EP utilizes diagnostic mapping techniques to confirm that all abnormal electrical signals have been interrupted. EPs have years of experience and training in mapping, tracking down and ablating A-Fib signals found in areas other than the pulmonary veins, while this is difficult for surgeons working from outside the heart.

VIDEO 2: Introduction to the Hybrid Surgery/Ablation Procedure. Dr. Robert Joy gives an overview of the hybrid procedure in which a cardiothoracic surgeon and an electrophysiologist work together in a single procedure; How it opens up a new opportunity for A-Fib patients who are not good candidates for catheter-based procedures alone. Posted on the Ellis Medicine website (includes a brief promotion of their services.) (1:46) 

Access Techniques

Most often surgeons access the heart using the same method as the Mini-Maze surgery. Three or more small incisions are made between the ribs for insertion of their scope and instruments. While the EP usually accesses the heart by inserting a catheter through the femoral vein in the groin and threads the catheter up and into the heart.

Another minimally invasive surgical approach is to access the heart through the soft tissues of the abdomen and with a small hole made in the diaphragm. This “convergent” approach is intended to result in less discomfort and a more rapid recovery for the patient.

Three Variations of the “Hybrid” Approach

In this article we are describing a “sequential” Hybrid approach. First, the surgeon works on the patient, then the EP steps in and takes over to detect and correct any gaps, and ablates additional locations of A-Fib signals.

A second Hybrid variation is a “simultaneous” approach with both the surgeon and the EP working on the patient at the same time. As the surgeon makes a lesion on the outside of the heart, the EP monitors the inside of the heart. The EP can tell the surgeon immediately if a particular lesion is effective (complete) or not. The surgeon can adjust the lesion or the EP can ablate the area. According to Dr. Wilber Su of the Cavanaugh Heart Center at Good Samaritan Medical Center, “the simultaneous hybrid maze procedure combines the best of what surgeons have to offer…with the knowledge, testing and confirmation of ablation by the electrophysiologist.”

A third Hybrid variation is “non-synchronous” or two-staged; the surgeon and the EP work on the same patient but they do so at different times (and sometimes even different locations).

(For more, see 2011 Boston AF: Hybrid Ablation for Persistent A-Fib.)

Results of Hybrid Surgery

In a small study of 27 patients most of whom had long-standing persistent A-Fib (the most likely candidates for a Hybrid Surgery/Ablation), at six months 72.2% of patients were in sinus rhythm, and 66.5% were off of antiarrhythmic drugs. (Four patients were still in A-Fib and one developed right atrial flutter.) These results are comparable to the success rates of catheter ablation procedures.²¹

Risks of Hybrid Surgery

Patients should keep in mind that Hybrid surgery, though called “minimally invasive,” is still major heart surgery. It is invasive, traumatic, complicated, requires considerable surgical skills and experience, and is potentially risky. And added to this are the low but real risks of a catheter ablation. Combining these two levels of risk is probably more dangerous than the sum of the parts. Also, patients have to be on anticoagulants for at least 90 days after the surgery/ablation.

Who Should Consider Hybrid Surgery?

The Hybrid Surgery/Ablation can be an effective option for highly symptomatic patients with persistent atrial fibrillation and longstanding persistent atrial fibrillation who have failed one or two catheter ablations, for someone with a significantly enlarged left atrium, or for someone who is morbidly obese (making it difficult to create imaging maps necessary for catheter ablations). (For more, see 2011 Boston AF: Hybrid Ablation for Persistent A-Fib”.)

Final Thoughts about the “Hybrid”

Is the “Hybrid” Surgery/Ablation better and more effective than current advanced catheter ablation strategies?²²Or the Mini-Maze?

Only time will tell. This is a relatively new operation with little long-term research or history of patient tracking.²³  Dr. Hugh Calkins of Johns Hopkins Hospital writes, “It is clear that more research is needed…a much larger, multicenter trial of “hybrid AF ablation” that targets a population of patients with long-standing persistent AF… .”²⁴Dr. Pison and colleagues note that the longer-term impact of this Hybrid Surgery/ablation strategy on atrial systolic function remains unknown.

Dr. Calkins also points out a logistical problem. It’s extremely rare to have tremendous expertise with catheter ablation and surgical A-Fib ablation at the same institution. Most centers are expert at one or the other. This will limit the number of facilities offering the Hybrid Surgery/Ablation approach, making it harder for patients to access this treatment choice. (See Steve’s Lists: Centers Performing the Hybrid Surgery/Ablation procedure.)

And finally, from a risk/reward perspective, if the Hybrid approach and advanced catheter ablation strategies have similar success rates, the advanced catheter ablation strategies might be preferable to Hybrid Surgery/Ablation.

A last thought, a prediction really, from Dr. M. Clive Robinson, a cardiothoracic surgeon with Bridgeport Hospital. Dr. Robinson, who performs the “hybrid”, has said “it is likely that the new hybrid ablation procedure will make Mini-Maze [surgery] obsolete,”²⁵

 Steve’s Lists

 Doctors by Specialty

I’ve compiled several specialty lists from the A-Fib.com Directory of Doctors & Facilities called ‘Steve’s Lists‘.

For surgeons performing Maze/Mini-Maze operations, see Doctors & Facilities/Steve’s Lists Doctors by Specialties and more specifically, US Surgeons performing Maze and Mini-Maze operations.

For centers performing the Hybrid Surgery/Ablation, see Steve’s Lists: Centers Performing the Hybrid Surgery/Ablation procedure.

 Additional Readings

• Advantages of the Convergent Procedure by Dr. James Edgerton
• FAST Trial: Surgical Versus Catheter Ablation―Flawed Study, But Important Results for Patients
• Advances in Surgical Therapy for A-Fib by Dr. David Kess
• Role of the LAA & Removal Issues

 Beware of Profit Incentives

 Mini-Maze Marketing

Be advised that some hospitals, medical services, web sites, etc. may promote the Mini-Maze over catheter ablation, because current reimbursement rates are higher for surgery (currently around $15,000 in the US) than for catheter ablation. Mini-Maze-type surgeries represent a huge and growing market and an important income source for hospitals, surgeons, medical device companies, web sites, etc.

Some hospitals, medical services, web sites, etc. may promote the Mini-Maze over catheter ablation, because current reimbursement rates are higher for surgery (currently around $15,000 in the US) than for catheter ablation.

Some 25,000 patients underwent Mini-Maze-type surgeries in 2009. Surgical devices to treat A-Fib have sales of about $100 million a year.²⁶

Profits may influence doctors to use medical devices for “off-label” treatments. (Companies are only allowed to market them for the uses for which they have been FDA-approved. The idea behind this restriction is to limit the number of U.S. patients exposed to experimental, relatively untested treatments.)

For example, AtriCure, of West Chester, Ohio, in 2010 agreed to pay $3.8 million to resolve allegations it marketed its surgical ablation devices for the unapproved purpose of treating irregular heartbeats (A-Fib). According to an article in Mass Device.

“The [U.S. Dept. of Justice, DOJ] lawsuit accused AtriCure of offering kickbacks to induce surgeons and hospitals to use its inpatient cardiac ablation procedure rather than less expensive, outpatient alternatives (such as catheter ablation). The company was accused of promoting the spread between Medicare reimbursement rates for its procedure and the cost to hospitals, and doling out kickbacks including free equipment, discounts, free advertising, marketing, and referral services and training for surgeons on its procedure.”²⁷

According to Jacqueline Bell of Law360.com:

“The DOJ also alleged that AtriCure pushed heart surgery using the company’s medical devices when less-invasive alternatives were appropriate, and suggested to hospitals how to pump up Medicare reimbursement claims for surgical procedures using the company’s devices.”²⁸

From Thomas S Burton, The Wall Street Journal:

AtriCure did not admit wrongdoing.²⁹

And in another settlement:

Estech (Endoscopic Technologies), of San Ramon, California, agreed to pay $1.5 million to settle similar charges with the Justice Department, also without admitting wrongdoing³⁰

Last updated: Saturday, January 8, 2022

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