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Minimally invasive surgery for heart rhythm abnormality proven effective

19.10.2004


A minimally invasive approach to curing the most common heart rhythm abnormality, atrial fibrillation, takes half the time of the traditional surgical procedure but is equally effective, according to research at Washington University School of Medicine in St. Louis.



Results from the first reported clinical trial testing the procedure appear in the October issue of The Journal of Thoracic and Cardiovascular Surgery. "Our findings show that this technique is much easier to perform but works just as well as the more invasive approach," says principal investigator Ralph J. Damiano, M.D., the John Shoenberg Professor of Surgery and chief of cardiac surgery at the School of Medicine, and a cardiac surgeon at Barnes-Jewish Hospital. "This is very good news because it means more surgeons can perform the procedure and it will be applicable to virtually all patients with this irregular rhythm."

Atrial fibrillation affects more than two million Americans. Normally, electric signals trigger the synchronized contraction of muscles in the heart’s two upper chambers, the atria. During atrial fibrillation, a chaotic web of electric impulses spreads throughout the atria, causing the chambers to quiver rather than contract in unison. The result is a host of painful symptoms and significantly increased risk of heart attack or stroke. In fact, atrial fibrillation accounts for about 15 percent of all strokes in the United States.


Medications can alleviate symptoms in some patients, but they cannot cure the problem. In 1987, researchers at the School of Medicine led by James Cox, M.D., developed a surgical cure called the Cox maze procedure to control these erratic impulses. In this procedure, surgeons make small, strategically placed incisions in the atria. The slits generate scar tissues that serve as barriers, trapping abnormal electric signals in a "maze" of barricades. Only one path remains intact, guiding impulses to their correct destination.

With a success rate of more than 90 percent, the Cox maze procedure revolutionized the treatment of atrial fibrillation. However, it is technically difficult and therefore is not performed frequently. Surgeons also must temporarily stop the heart and use a heart-lung machine to take over the heart’s role of circulating blood in order to make the incisions. Not all patients, therefore, are healthy enough to endure the operation.

Damiano and his colleagues developed an alternative using two electrodes that pass a current through a section of heart tissue, heating and killing a thin band of tissue. This bipolar radiofrequency variation of the Cox maze procedure creates scar tissues that similarly block abnormal impulses responsible for atrial fibrillation.

Damiano’s team replaced most of the Cox maze incisions with lesions created using the new, less invasive approach in 40 consecutive patients treated for atrial fibrillation at Barnes-Jewish Hospital from January 2002 to October 2003.

Overall, the success of the procedure was equivalent to the team’s success using the traditional Cox maze approach between January 1988 and January 2002. All patients survived the operation, and about 15 percent needed a pacemaker after surgery to help maintain a normal heart rhythm. A little over 90 percent of patients followed for six months still had healthy heart rhythms.

The only notable difference between the patients in this study and their predecessors who had undergone the traditional surgery was the length of the operation. Traditional Cox maze procedures took, on average, 93 minutes to perform, while procedures that incorporated the new approach took only 54 minutes. "Shorter operative times are important for patient safety and outcome," says Damiano. "If we shorten the procedure, it decreases the time we need to keep patients on the heart-lung machine. We are working in the laboratory on an approach that someday will allow us to perform atrial fibrillation surgery on the beating heart."

Gila Z. Reckess | EurekAlert!
Further information:
http://www.wustl.edu

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