Atrial fibrillation (AF) occurs when the top two chambers of the heart, the atria, beat more rapidly and irregularly than normal and are not synchronized with the bottom two chambers, the ventricles. Because of this irregular heart rate and rhythm, the ventricles do not fill up completely before squeezing, which reduces the pumping capacity and efficiency of the heart by 20 to 30 percent. Blood pools and swirls in the left atrium during AF, which encourages clots to form. If these clots leave the atrium and are pumped to the body by the left ventricle, they can block a small blood vessel. One quarter of all strokes are caused by clots formed during AF.

The first line of treatments for AF is blood-thinning medication, medication to regularize heart rate (anti-arrhythmics), and cardioversion. However, the side effects of anti-arrhythmic drugs are significant, and studies show that only a third of patients on AF medication therapy take their pills as directed. Even among those who take their medication correctly, half will revert to AF despite the drugs. Cardioversion often restores a normal rate and rhythm in the short term, but in the long term a significant proportion of patients revert back to AF. Patients with chronic atrial fibrillation have dimished life spans, and 15 to 30 percent will suffer a major complication, such as stroke, within five years of diagnosis.

AF ablation, a catheter-based therapy, is a minimally invasive treatment that successfully restores a normal heart rate and rhythm for many patients. However, catheter-based AF ablation does not reduce the risk of stroke. This is because AF-related blood clots continue to form near an appendage in the heart’s left atrium. During AF, this appendage stops contracting regularly with the rest of the heart muscle, causing blood to stagnate. Even when medication, cardioversion, or ablation restore normal rate and rhythm, the appendage continues to lie dormant and blood continues to stagnate. Only surgical removal or isolation of the clot-forming appendage will eliminate the risk of stroke.

The surgical treatment for AF is called maze, after the maze-like pattern of lesions created in the heart muscle during the procedure. These lesions, which block conduction of the errant electrical signals that cause AF, are similar in pattern to those created by catheter-based technologies during AF ablation, but there are important differences. Because the surgeon has full access to the heart during maze surgery, he is able to use a wider variety of energy sources and can direct that energy at both sides of the heart muscle. During catheter ablation, by contrast, the physician can access only the inside of the heart muscle. Thus, maze surgery leads to lesions that are more precise and that penetrate farther across the heart muscle than those created during catheter-based AF ablation. The original form of this surgery, pioneered in the 1980s, created a maze-like pattern of scars by cutting the heart muscle and then sewing it back together. Modern forms of surgical maze replace cutting with radiofrequency, ultrasound, or freezing energies in order to create a similar scar pattern.

Because surgical maze requires an incision in the breastbone, it is not typically the first line of therapy for patients with AF. However, patients who have not been helped by, or are not suitable for, catheter-based AF ablation, or patients who have other structural heart disease—such as coronary-artery blockages or heart valve dysfunction—may be candidates for surgical maze. Also, patients who have had a stroke or who need open-chest surgery for another condition should consider maze. Because it presents no additional risk and adds only 20 minutes to an operation, the maze procedure is now a standard add-on to all open-chest heart surgeries performed on patients with AF at UW Medicine Regional Heart Center.

Surgical maze is an open-chest procedure performed under general anesthesia. When performed by itself, it takes about two hours and requires a hospital stay of three to seven days. The chest incision takes approximately four weeks to fully heal. Because the heart lesions take three to six months to completely scar over, restoration of normal heart rhythm and rate, as well as recovery of the patient’s energy level, may also take several months.

Patients are given blood thinners, such as Coumadin, and anti-arrhythmic drugs for several months following the surgery, until the heart lesions scar over and normal heart rhythm is restored.

Patients with AF should consider surgical maze if: 1) catheter-based AF ablation has failed to restore heart rhythm and rate, 2) they are at risk of a stroke, or 3) they already need open-chest surgery for another heart condition. Sometimes patients with AF have another heart condition that, by itself, falls just short of needing surgery. In these patients, surgery may be warranted if both heart conditions can be fixed simultaneously.

Surgical maze has an 80 to 90 percent rate of success at restoring normal heart rate and rhythm and reducing the risk of stroke. Earlier intervention is associated with a higher success rate. Patients with years of chronic AF, enlarged heart chambers (a secondary effect of chronic AF), or decreased heart function have a lower chance of success.

There is no added risk when the maze procedure is performed with other open-chest cardiac surgery. All heart surgeries carry some risks, such as infection, stroke, and damage to heart function. There is also the small but finite risk of general-anesthesia complications.

Patients who do not treat their AF will continue to experience symptoms, have a shortened life expectancy, and be at risk of stroke. Even those who can control AF with anti-arrhythmic drugs must take those drugs and endure their significant (and often cumulative) side effects indefinitely, unless they undergo further intervention.

Surgical maze is an elective procedure that can be scheduled at the patient’s convenience, after consultation with his or her referring physician.