Some 2 million Americans suffer from atrial fibrillation, in which the electrical signals that control the synchronized contraction of the heart's two upper chambers go awry. Instead of following the normal pathways, those electrical signals spread out irregularly, so that the chambers quiver uselessly. The resulting problems include a high risk of blood clots, which can cause strokes by blocking brain arteries. An estimated 15 percent of all strokes are attributed to atrial fibrillation.
In most patients, drugs such as digoxin or beta blockers can control the condition. But for severe cases, the only alternative until now has been surgery called the Maze procedure, in which tissue that transmits the abnormal signals is destroyed with great precision, leaving a pathway that guides the signals to their correct destination.Maze surgery is technically difficult and so is not widely available. But a group led by Dr. Ralph J. Damiano Jr., professor of surgery and chief of cardiac surgery at Washington University, will perform the procedure using a precision radio-frequency device.
That device will use carefully controlled impulses sent through two electrodes to destroy the abnormal tissue, with minimum damage to surrounding normal tissue, the Washington University team told the annual clinical congress of the American College of Surgeons in New Orleans today.
"We can route the electrical impulses where we want them to go, not where they want to go," Damiano says.
A potential major advantage of the radio-frequency technique is that it could be done without stopping the heart, Damiano says. A patient must be put on a heart-lung machine for the Maze procedure, which means a prolonged hospital stay.
"The current stay is about seven days," Damiano says. "We figure that if we do it without using the heart-lung machine, it could be one or two days. Certainly our current work suggests that this procedure can be done on a beating heart."
The device to be used at Washington University was developed by Atricure, Inc., of Cincinnati. It is a more advanced form of the bipolar radio-frequency devices now available at major medical centers, says Douglas Ladd, a company spokesman. Those devices are used in procedures where minimum blood loss is desired; for example, to harvest blood vessels for bypass surgery.
"What is unique about our device is that it uses a very low level of power compared to other radio-frequency devices, and, as a result, we are able to ablate [kill] tissue in a way that creates no spread," Ladd says. "The other thing that is unique is that we are able to monitor the ability of tissue to conduct electrical signals as it is ablated. What you want to do is to make lines in very specific spots and make sure you do not allow electrical signals to pass though them."
Instant feedback from the electrodes of the device will be available to the surgeon in two ways, Ladd says. It will be displayed on a video screen and will also generate a tone whose sound will change as tissue is destroyed.
"We can know in a split second when the tissue is not able to conduct electrical energy," Ladd says.
The technique has been tested on sheep, Damiano says. The destruction of a section of abnormal tissue that takes five to 10 minutes with conventional surgery can be done in less than 10 seconds with radio frequency, he says.
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"The first human cases probably will be done in November," Damiano says. If the procedure is successful, he says, "It shouldn't take long for it to be widely available."