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Maze Procedure for Atrial Fibrillation

SPECIALISTS WHO TREAT AND COMMONLY ASKED QUESTIONS ABOUT THE MAZE PROCEDURE

The Maze procedure, developed at Washington University School of Medicine, is a surgical intervention that cures atrial fibrillation (AF) by interrupting the circular electrical patterns or wavelets that are responsible for this arrhythmia. Just like its name, the cardiothoracic surgeon creates barriers and blind alleys within the heart so the electrical impulse has only one route to travel. This causes the malfunctioning electrical system of the heart to move in the correct sequence in a normal top-to-bottom direction.

The surgical procedure is done by making strategic incisions in the heart, and the resulting little scars create the permanent barriers to form the maze. The Maze corrects the three problems associated with atrial fibrillation - permanently erases the arrhythmia, restores proper rhythm between the atrium and the ventricles and preserves a correct and organized contraction of the atria.

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What is atrial fibrillation ?

Atrial fibrillation is an abnormality of the electrical system of the heart. Normally, the heartbeat is triggered by an electrical impulse which starts in the sinoatrial (SA ) node. The SA node is in the upper right chamber, or the right atrium, and is the normal " pacemaker " of the heart. The electrical signal that triggers the heart's contraction starts in the SA node and normally moves evenly across the atrium enabling the heart to contract all at once. The impulse then travels through the atrioventricular ( AV ) node and triggers the ventricles ( the main pumping chambers of the heart ) to contract. This entire process is called sinus rhythm.

Atrial fibrillation occurs when the electrical impulse no longer travels from the SA node to the AV node in the normal manner. Instead of the impulse traveling evenly across the atrium straight from the SA node to the AV node, the impulse is "side-tracked." This means that the atrium is no longer triggered in an even and synchronized fashion, but is triggered one small region at a time. As a result of this malfunction, the atrium can no longer contract in a coordinated manner, but instead it fibrillates irregularly and leads to an irregular heartbeat.

Figures A and B show atrial flutter and atrial fibrillation. Rather than traveling in a straight line, the impulse is "side-tracked" such that it travels in large or small circles triggering the atrium irregularly to contract.

What causes atrial fibrillation?

A variety of conditions can lead to atrial fibrillation. The most common cause of atrial fibrillation is simply aging. The risk of atrial fibrillation increases as we grow older and areas of scarring or fibrosis develop in our atrial tissue as a result of simple "wear and tear." Abnormalities of the valves in the heart, most often the mitral valve, can also cause "wear and tear" and lead to atrial fibrillation. Some specific conditions that can lead to atrial fibrillation, such as thyroid disease, may be treatable with medications alone. Other conditions may be treatable by our colleagues the cardiologists in the cardiac catheterization laboratory. In a small number of cases, atrial fibrillation appears to be inherited - which is to say that it runs in some families - while in many cases its cause is unknown.

Why is atrial fibrillation a problem ?

Atrial fibrillation results in: 1) an irregular heartbeat that may be too slow at times, and racing at others, 2) loss of the atrial contraction that normally contributes to filling of the ventricle ( the main pumping chamber of the heart ) and improves pump performance --in some ways analogous to a automobile engine supercharger, 3) an abnormal flow of blood through the atrium with areas of stagnation ( eddies ) which increase the risk of stroke.

How does the Maze procedure correct atrial fibrillation ?

The surgical procedure is complex. In principle it consists of creating a number of incisions in the atrium that disrupt all of the potential re-entrant circuits. An electrical impulse cannot cross the scar that is left behind after an incision has been made.

The incisions are organized in a specific pattern such that there is only one pathway from the SA node to the AV node.

Once the incisions are made they are sewn together again so that the atrium is once again "water-tight" and can hold blood on its way to the ventricle. The atrial muscle is also normal, so it can still contract to push the blood into the ventricle. The result is what looks like a children's maze , hence the name. The atrium can no longer fibrillate and sinus rhythm (the normal rhythm of the heart) is restored.

What is the Washington University advantage?

First, the procedure was developed here at Washington University in 1987; consequently, we have the longest history of performing the operation. Because of its complexity, the experience and skill of the surgeon is paramount. Second, we provide a true multidisciplinary approach to treatment, employing the skills of our cardiology/electrophysiologists, recognized as the top scientists in their field. The strength of our program is that all the team members are in one place, so patients benefit from their collective experience and availability.

Who is a candidate for the Maze ?

The Maze procedure is not necessary in most patients with atrial fibrillation. Most patients are not bothered by the rhythm or the medications required for its control. In some patients, our cardiology electrophysiologists are able to disrupt the circuits that cause atrial fibrillation with catheters using radio frequency. Other patients, however, are so troubled by the way they feel when they are in atrial fibrillation or by the medications they must take, that a surgical option is appropriate. The Maze procedure may also be indicated for individuals in atrial fibrillation who have experienced a stroke because they are at significant risk for another stroke.

Is it an open heart procedure ?

Yes, the Maze is an open-heart procedure. The surgeon makes an incision about 10-12 inches in length and divides the sternum (breastbone) to access the heart. The patient is transferred to a heart-lung machine during the procedure. After surgery, the sternum is wired together and the skin sutured. If other procedures such as valve replacement or coronary bypass are to be performed concurrently with the Maze procedure, then the standard open chest approach is likely to be used.

What are the risks associated with the Maze ?

Because the Maze procedure is usually open-heart, there is operative risk. Although the risk is low in general terms, it is affected by the individual's specific health conditions (heart function, lung function, kidney function, etc.). Like any open heart procedure, there is also a risk of stroke, kidney failure, other organ failure, and death.

Although the procedure is directed toward curing abnormal heart rhythm, there is some risk that the procedure may fail and that atrial fibrillation will persist. In the early postoperative period, up to one-third of patients may have temporary atrial fibrillation. It is easily controlled with medicines, however, and it resolves within 6 to 12 weeks. In addition, some patients may require a permanent pacemaker postoperatively. This is probably because many patients with atrial fibrillation also have underlying disease of the SA node.

What is the success rate for the Maze?

The Maze procedure is highly effective in restoring sinus rhythm. Success rates vary by center, but are generally reported in the range of 80-100%. The majority (about 90%) of patients will be restored to sinus rhythm without the need for any medications. The majority of the remaining patients will have control of their rhythm with a single medication, even if that medication did not control their rhythm preoperatively.

What can I expect after surgery?

Most patients are hospitalized an average of 10-12 days. Much of that time is spent waiting for the atrial tissue swelling to decrease and the sinus node function to return. Patients are usually in the intensive care unit for two days and the remainder of the time is spent on the step down unit. Typically, at this point, patients can walk around a bit, wearing a portable telemetry monitor while they wait for the heart's rhythm to stabilize.

In general, the recovery is complete about 6-8 weeks after surgery. Depending on the type of work that a patient performs and the surgical approach that was used (minimally invasive versus open chest), the decision to return to a full schedule is somewhat individualized. For those patients with physically demanding work, the recovery may be extended to three months for open chest procedures.

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Copyright 2014 Washington University School of Medicine
Copyright 2014 Washington University School of Medicine