Tiny Device Blocks "Useless" Part Of Heart, Prevents Blood Clots

About 2 million Americans have been diagnosed with atrial fibrillation, a type of irregular heartbeat. About 15 percent of strokes occur in people with atrial fibrillation. Each year, about 600,000 Americans suffer a new or recurrent stroke.

Previous studies indicate that more than 90 percent of nonrheumatic AF-related strokes result from a blood clot that forms in the left atrial appendage, a small, thumb-shaped pouch in the heart’s left upper chamber. Such clots can block a blood vessel leading to the brain, causing a stroke.

In a multicenter trial, German researchers successfully sealed off the left atrial appendage of 15 chronic AF patients with a novel procedure called PLAATO.

PLAATO, which stands for percutaneous left atrial appendage transcatheter occlusion, 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 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 PLAATO was technically feasible,” says Sievert, a senior consultant at the Cardiovascular Center of Bethanien Hospital in Frankfurt, Germany. “Not only was it possible, but after six months we have had no strokes and no late complications.”

Stroke is the most serious consequence of AF.

The anti-clotting drug warfarin can prevent strokes in AF patients. 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.

Therefore, another treatment is needed to prevent strokes in people with AF.

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

Using an ultrasound technique called transesophageal echocardiography to guide them, the researchers threaded a catheter containing the PLAATO device to 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 nitinol cage expanded to its proper shape.

Tiny spikes attached to the 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, four patients had the device removed and replaced with one of a different size with no problems. One patient 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 PLAATO 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 became a valuable alternative for patients with chronic, non-rheumatic AF in whom standard anticoagulation therapy is contraindicated or poorly tolerated.”

Co-authors are Michael D. Lesh, M.D.; Thomas Trepels; Heyder Omran, M.D.; Antonio Bartorelli, M.D.; Paola Della Bella, M.D.; Toshiko Nakai, M.D.; Mark Reisman, M.D.; Dirk Fleschenberg; Ulrike Krumsdorf; and Detlef Scherer, M.D.