April 21 (HealthDay News) -- Adding one step and no more than 20 seconds to heart surgery can greatly improve the results of an operation to treat the common irregular heartbeat called atrial fibrillation, according to a new report.

In the April issue of the Journal of Thoracic and Cardiovascular Surgery, heart surgeons at Washington University School of Medicine in St. Louis reported that one extra ablation -- a precise scar that destroys the heart muscle tissue housing the short circuit responsible for the irregular heartbeat -- to a series of such scars already being made during the surgery makes a significant difference.

"The single additional ablation creates what we call a box lesion," Dr. Ralph J. Damiano Jr., the John Shoenberg Professor of Surgery at the Washington University School of Medicine, said in a prepared statement. "The box lesion surrounds and electrically isolates the pulmonary veins and the posterior left atrial wall from the rest of the left atrium. Our study shows excellent success when using the box lesion, and we recommend it for any patient with long-standing atrial fibrillation."

During atrial fibrillation, the upper chambers (atria) of the heart beat rapidly and quiver instead of contracting, drastically reducing the amount of blood they pump. Without the box lesion, this area could still conduct electrical signals that disrupt the regular contractions of the heart's upper chambers.

The extra ablation improves upon the Cox-Maze procedure, a surgical procedure that redirects wayward electrical impulses causing irregular heartbeat. The procedure, which creates a series of ablations in the heart muscle, is highly effective at curing atrial fibrillation, the Washington University scientists said.

The study involved two groups of patients undergoing surgery to correct atrial fibrillation -- one receiving Cox-Maze procedures with a box lesion and one without it. The box lesion group had a 48 percent lower occurrence of atrial flutter and fibrillation in the first weeks following surgery. These patients also had shorter hospital stays -- nine days on average versus 11 days.

Three months after surgery, only 5 percent of patients with the box lesion showed signs of atrial fibrillation, compared with 15 percent of the patients receiving the standard procedure. All patients in the box lesion group were free from atrial fibrillation after six months, compared with 90 percent of the other group, the researchers said.

More than 2 million people in the United States have atrial fibrillation, which can cause fatigue, shortness of breath, heart palpitations and stroke. Medications can control the abnormal heart rhythms in some patients, as well as the risk of clotting, but only surgery can cure the disorder.

SOURCE: Washington University in St. Louis, news release, April 7, 2008