Clot Plug Passes First Test
Prevents risky blood from collecting in leftover heart pouch
MONDAY, April 8, 2002 (HealthDayNews) -- Your heart has a useless appendix and, just like the vestigial organ in your gut, it can be the source of deadly trouble.
Known as the left atrial appendage, it's a fleshy pouch hanging off the primer to the heart's main pumping chamber. Doctors believe it only serves as an occasional reservoir for dangerous blood clots in people with faulty heartbeats.
However, a new device that prevents the pouch from collecting blood may neutralize its effect in the people most prone to the blockages, a new study has found.
So far, it's not clear if the experimental technology works as advertised. Yet, the latest research shows the plugs can be safely implanted in humans. A report on the surgeries appears in tomorrow's issue of Circulation.
Remnants of fetal heart development, the pouches pose no threat to people with healthy pumps. The blood that wells up gets pushed out with beating. However, for those with atrial fibrillation, a common heart rhythm anomaly, the pouch can't be cleared efficiently. Blood stagnates, gels and eventually forms clots that can drift off and make their way to the brain, where they can do deadly damage.
Atrial fibrillation affects an estimated 2 million Americans. Left untreated, it can lead to life-threatening clots -- most of which originate in the pouch -- in between 5 percent and 15 percent of patients. The current standard of care for the condition is the blood thinner warfarin.
In theory, the new device, called PLAATO -- for percutaneous left atrial appendage transcatheter occlusion -- could be even more effective. An expandable metal cage covered by a polymer membrane, it resembles two circus big tops joined at the base. Once deployed via catheter, the apparatus seals off the pouch and prevents it from filling with blood. Appriva Medical of Sunnyvale, Calif., developed the device.
In the new study, German and American heart surgeons report PLAATO can be safely implanted in people, although the trial was not designed to detect any drop in clot risk.
A team led by Dr. Horst Sievert of the Cardiovascular Center Bethanien in Frankfurt implanted the devices in 15 men and women, aged 59 to 78, with atrial fibrillation. None of the patients had heart valve problems.
The 90-minute operation went smoothly in 14 patients and, after an initial complication, was repeated successfully in the 15th. The cages were 18 millimeters to 32 millimeters in diameter, or between 20 percent and 40 percent bigger than the patients' pouches.
A month later, chest X-rays showed the implants holding steadily in place, and none of the patients had evidence of clotting in the immediate area.
Sievert says his group has since performed the procedure in two more patients, and the original 15 have reached the six-month mark with no problems. Still, he says, it's far too soon to say if the devices prevent blockages.
"We need longer follow-up and more patients," Sievert says. A trial with 300 to 400 patients is being planned for late this year or early next year.
Dr. Paul Kramer, a cardiologist who implanted PLAATOs in three patients as part of a study in the United States, says heart specialists have high expectations for the technology.
"All of this is intuitive. We all anticipate that this will translate into a clinical benefit for patients, but we haven't shown that yet," he says.
Most patients with atrial fibrillation are prescribed warfarin. However, this drug is notorious for causing bleeding problems in some people. Moreover, it doesn't eliminate the risk of clots.
"The risk will be further reduced if this little side chamber of the heart is blocked, and maybe this will actually be better than [warfarin]," says Kramer, who has no financial ties to Appriva.