About 15 percent of the 600,000 new and recurrent strokes diagnosed in the U.S. each year occur in people who have atrial fibrillation. Previous studies indicate that more than 90 percent of nonrheumatic fibrillation-related strokes result from a thrombus that formed in the left atrial appendage and subsequently embolized into the systemic circulation.

In a multicenter trial, German researchers successfully sealed off the left atrial appendage of 15 patients with chronic atrial fibrillation with a novel procedure called percutaneous left atrial appendage transcatheter occlusion. In the procedure, the clinician uses a catheter to place a blocking device at the mouth of the appendage.

"The left atrial appendage has no purpose; no one needs it," says lead study author Horst Sievert, M.D. "Its only function is to form clots. It can be blocked with no disadvantage to the patient."

The blocking device is a self-expanding metal cage made of nitinol that pops open as the metal warms up inside the body. The cage is covered with a membrane, which both blocks the atrial appendage and allows normal tissue to grow into the device.

"This study was to show [that the procedure, termed PLAATO] was technically feasible," says Sievert,. "Not only was it possible, but after six months we have had no strokes and no late complications."

Warfarin can prevent strokes in patients with atrial fibrillation. However, "this drug's disadvantages are that it can cause bleeding, it is difficult to control, and many patients cannot take it, which puts them at high risk of stroke." Sievert says.

The researchers selected 15 patients whose dysrhythmnia was not caused by rheumatic fever. All of the patients were at high risk for stroke because they could not take warfarin for long periods. Participants ranged in age from 59 to 78 years.

The research team used transesophageal echocardiography to guide placement of the device at the entrance of the atrial appendage. If the initial placement was not adequate, the researchers collapsed the device and repositioned it. Once inserted properly into the mouth of the atrial appendage, the cage expanded to its proper shape. Tiny spikes attached to the nitinol-alloy cage that protrude through its covering anchored the device in place.

The left atrial appendage was successfully blocked in all 15 patients, Sievert says.
Each patient received a device that was 20 percent to 40 percent larger than the opening of his or her left atrial appendage. During the procedure, 4 patients had the device removed and replaced with one of a different size with complication. Of the 15 patients, 1 person had a complication during the procedure, so four weeks later the procedure was repeated, this time successfully.

The patients' implants, when fixed in place, ranged in diameter from 18 to 32 millimeters. The average time for the procedure was 92.7 minutes.

As promising as the new findings appear, Sievert emphasizes that additional studies are needed to confirm the successful implantation of the device and to show that the therapy will prevent strokes. "This initial study supports the concept that implanting a mechanical device to block the left atrial appendage can be done safely and with relative ease," Sievert says. "It may become a valuable alternative for patients with chronic, non-rheumatic atrial fibrillation in whom standard anticoagulation therapy is contraindicated or poorly tolerated."