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Michael E. DeBakey VA Medical Center - Houston, Texas

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Houston VA Vascular Surgeons Implant Wireless Pressure Sensor to Monitor Abdominal Aortic Aneurysms in Endovascular Repair

December 12, 2005

HOUSTON - The Michael E. DeBakey VA Medical Center (MEDVAMC) is the first VA hospital to implant a cutting-edge, FDA-approved wireless pressure sensor to monitor aortic aneurysm pressure in patients undergoing endovascular aortic aneurysm repair.

Each year, approximately 15,000 people die from Abdominal Aortic Aneurysms (AAA), making this disease the 13th leading cause of death in the U.S. AAA is the third leading cause of sudden death among men over the age of 60 and affects 1.5 million people in the U.S., with approximately 200,000 new cases diagnosed each year.

An aneurysm is a ballooning of an artery resulting from a weakening or stretching of the arterial wall. Aneurysms may occur in any blood vessel, but the most common place is in the abdominal aorta just below the kidney arteries. The aorta is the large arterial trunk that carries blood from the heart to be distributed by branch arteries through the body.

If an abdominal aortic aneurysm is left untreated, it can rupture leading to catastrophic consequences. However, aneurysms can be successfully treated with stent grafts which are made of flexible fabric and metal tubes inserted via small incisions near the patient's groin and placed snugly inside an aneurysm to prevent aneurysm enlargement.

"Endovascular aneurysm repair is a less invasive and less painful treatment in patients with abdominal aortic aneurysm compared to the traditional open abdominal operation. The Achilles heel of endovascular repair, however, relates to a small incidence of endoleaks. That is, continued filling and pressurization of the aneurysm sac even after endovascular repair. Such pressurized sacs may remain at risk for rupture and, unfortunately, standard imaging methods such as angiography or CT scanning do not always show the leak," said Peter Lin, M.D., chief of Vascular Surgery at the Michael E. DeBakey VA Medical Center.

"Because of this risk, patients must have their stent grafts checked at least once a year by their health care provider. Besides being expensive, the CT scans used to monitor the stents sometimes fail to detect small leak within the aortic aneurysm. These leaks can lead to a gradual enlargement of the aortic aneurysm which may result in rupture. Furthermore, CT scans are associated with certain risks including contrast dye which can be harmful to the kidney as well as radiation exposure." said Ruth Bush, M.D., MEDVAMC vascular surgeon.

The FDA recently approved a wireless implantable pressure sensor, which is implanted by physicians during the endovascular aortic aneurysm repair. This thin oval-shaped wireless sensor, about the size of a quarter, contains microchips that sense changes in pressure and a coil that works like a tiny radio antenna.

When health care providers want to gather pressure information from the sensor during follow-up appointments, they use an electric wand that transmits a signal to the sensor. When the sensor bounces the signal back, the wand uses changes in the electrical signals to determine how much pressure the sensor is experiencing. The sensor can detect very subtle changes, equivalent to a one millimeter shift of the mercury in blood pressure readings, and if the pressure reading climbs, physicians know something is wrong.

"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 and it represents a great step forward in medical device technology," said Wei Zhou, M.D., MEDVAMC vascular surgeon.

MEDVAMC vascular surgeons have extensive experience in using endovascular stent graft devices to treat patients with aortic aneurysms. Since 1998, they have collectively performed more than 1,500 endovascular procedures in the treatment of aortic aneurysms, including the thoracic and abdominal aorta. This represents the largest experience in the VA health care system. Veterans may contact the MEDVAMC Vascular Surgery Service at (713) 794-7892 for more information about endovascular aneurysms and cutting-edge treatment options.

"The Michael E. DeBakey VA Medical Center is the first VA hospital in the country to implant this wireless pressure sensor in patients undergoing endovascular aneurysm repair. This is extremely exciting because of the long tradition of excellent care our medical center provides to veterans with cardiothoracic and vascular diseases," said Alan Lumsden, M.D., MEDVAMC vascular surgeon.

The Michael E. DeBakey VA Medical Center (MEDVAMC) is the first VA hospital to implant a cutting-edge, FDA-approved wireless pressure sensor to monitor aortic aneurysm pressure in patients undergoing endovascular aortic aneurysm repair. Above, Peter Lin, M.D., chief of MEDVAMC Vascular Surgery examines veteran Wendell Sowel whose aneurysm was successfully treated with stent graft.

PHOTO BY: Sally McCoy, RN, Nurse Practitioner, Operative Care Line