Wireless Implant Monitors Aneurysms

By M.L. Baker  |  Posted 12-12-2005
Wireless pressure sensors are being used to warn doctors that a blood vessel is liable to burst.

On Monday, the Michael E. DeBakey VA Medical Center announced that it had implanted the Endosure sensor in patients who were receiving stents to protect against aortic aneurysms.

The sensor, approved by the FDA last month, promises a more effective, cheaper and safer way to make sure the stents are working.

Aneurysms occur when a weakened area of an artery gives way, creating a bulge. This is most likely to happen in the abdominal aorta, just under the kidneys.

Abdominal aortic aneurysms are the third leading cause of sudden death in elderly U.S. men and the 13th leading cause of death in the United States.

The device, made by CardioMEMS Inc., is implanted in the aneurysm sac.

When activated by an external device, it transmits information about pressure inside the aneurysm.

According to Division of Vascular Surgery and Endovascular Therapy of Emory University, which tested the sensor, aneurysms are typically repaired by inserting a stent into the affected blood vessel. This takes the pressure off the aneurysm by creating a new route for blood to flow.

But since the stents can leak and cause the aneurysm to rupture, they require regular check-ups. The sensor, which is implanted into the aneurysm sac, provides a new way to monitor the pressure.

Instead of expensive CT (computed tomography) scans every six or 12 months, physicians can place an antennas over a patients' abdomen to make sure that the stent is still holding up; sensor information is converted to a pressure wave form and displayed on a screen.

Besides the expense, CT scans are also problematic because they can fail to detect small leaks and require contrast dye and radiation that might harm patients, said Ruth Bush, MEDVAMC vascular surgeon.

"Because this cutting-edge device is inside the aneurysm, it can give us information we never had before. We are now able to monitor pressure changes and receive important feedback regarding the stent graft's ability to appropriately seal off the aneurysm from systemic circulation. This system provides an opportunity for us to know whether the aneurysm is truly protected against rupture after endovascular repair," said Wei Zhou, M.D., MEDVAMC vascular surgeon.

According to its producer, CardioMEMS Inc., the device is the first wireless, permanently implantable pressure sensor to become commercially available in the United States.

It received FDA approval after testing in 100 patients in Brazil, Argentina and Canada and at nine hospitals in the United States.