Medical Device Daily Contributing Writer
An Internet audience was treated to a recent live webcast of a minimally invasive surgical (MIS) repair of an endovascular abdominal aortic aneurysm (AAA) using a new stent graft repair system.
Surgeons from Surgical Care Associates (Louisville, Kentucky) performed the procedure at Baptist Hospital East (also Louisville) last month using the Gore Excluder bifurcated endoprosthesis from W. L. Gore & Associates (Flagstaff, Arizona).
More than 15,000 people die in the U.S. every year when their aneurysms rupture, making this disease the 13th leading cause of death in this country.
Traditional surgical treatment of an AAA involves a large midline incision to place a synthetic graft to repair the diseased artery. This traditional method results in long hospital stays of four to five days and painful recoveries, often from six to eight weeks.
In contrast, the new MIS endovascular stent graft repair generally requires only a one- to two-day hospital stay and a recovery of two to three weeks, and it also may be applied to elderly and high-risk patients, a subset that surgeons had been hesitant to treat with the traditional surgical approach.
The endovascular AAA repair was done in the hospital's dedicated endovascular/radiology suite. A specialized postoperative nursing care unit has also been designed for patients undergoing endovascular AAA repair.
Elizabeth Rachel, MD, was the primary surgeon, and Matthew Jung, MD, served as moderator for the webcast. Jung described the steps in the procedure and fielded live questions from viewers over the Internet.
The Excluder bifurcated endoprosthesis is constructed of a durable expanded polytetrafluoroethylene (ePTFE) bifurcated graft with an outer self-expanding nitinol support structure to combine both device flexibility and material durability. The function of the endoprosthesis is to internally reline the abdominal aorta, including the bifurcation. This isolates the aneurysm from the flow of blood and thus blocks its growth in size. Its small outer diameter makes the device very useful for female patients whose arteries are normally smaller than those of males.
The device was approved by the FDA in November 2002 (Medical Device Daily, Nov. 8, 2002), and the company has added several extensions to the Excluder line since then.
The patient was a 78-year-old woman with a family history of vascular disease. Her aneurysm was discovered about three years ago. Since that time the aneurysm had grown to measure 5 cm in diameter.
Experts believe that once an aneurysm reaches 5 cm, the risk of rupture exceeds the risk of surgery. The patient received general anesthesia and was prepped and draped in the traditional manner.
To initiate the implant, two oblique incisions were made – one in each of the patient's groins. The common femoral artery was isolated on each side and an 8 Fr introduction sheath was placed in the left common femoral while a 6 Fr sheath went into the right common femoral.
Next, the 18 Fr Gore Excluder delivery sheath was introduced into the left artery over a stiff wire. Fluoroscopy was used to monitor each step in this procedure. A radiopaque indicator at the tip of the deployment sheath provided location verification.
Jung answered a question from a viewer. "What percentage of people with AAAs of 6 cm die?"
Jung replied, "The mortality rate is directly related to the size of the AAA. At 6 cm about 8% of those people die from rupture. At 7.5 cm the risk goes to 15% to 20%."
The Gore Excluder bifurcated graft is shaped like an upside-down "Y." It comes in two parts: the upper portion of the Y and the left limb form the main part of the graft. The right limb is the second part. They are deployed separately, largest section first. The main body of the graft will lie inside the AAA and the left limb of the graft will be placed in the left femoral artery. Then, coming from the right common femoral the contralateral (right) limb of the graft will be introduced.
First, the implant is prepared on a second back table using a double-glove technique to reduce any possibility of contamination. A metal mandril is removed from the graft, and the graft is then irrigated with saline just prior to introduction.
The graft was placed inside the deployment sheath and moved up to the proximal neck of the AAA, just below the renal arteries. At this point the anesthesiologist held the patient's respirations while Rachel deployed the stent graft by removing a retaining screw and pulling back on the deployment sheath. This motion allowed the stent to expand.
Correct positioning was determined by fluoroscopy, and the stent's proximal anchors were set by inflating elastomeric balloons from inside the graft. The anchors provide positive fixation into the wall of the abdominal aorta so the graft will not migrate out of place.
Another viewer asked, "Are AAAs inherited, and what can I do to prevent having one?"
Jung answered that AAAs are inherited, adding: "There is a 10% to 20% increase in risk if a close relative has had an AAA. Unfortunately there is nothing you can do to stop them, [and that] smoking and atherosclerosis are additional risk factors."
In the OR, Rachel secured the main body and the ipsolateral (left) limb of the graft. Then, the surgeons moved to the patient's right side and prepared to deploy the contralateral limb of the graft. Several sizes are available for this right limb of the graft. Rachel used intravascular ultrasound (IVUS) to measure the necessary length and diameter. A gold ring marks the gate or opening of the main graft for entrance of the contralateral limb.
An 18 Fr diameter, 9.5 mm length graft was prepared using double gloves and saline irrigation. The graft was then placed over a wire and deployed so that it was inside the major body of the graft with a 3 cm overlap into the gate.
From the audience: "Can all patients with AAAs be treated in this endovascular manner?" And, "How can I be checked for an AAA?"
Jung answered: "No. The shape and position of the AAA determine eligibility. We need a certain amount of good aorta below the renal arteries to be sure we can anchor successfully."
As to detection of AAA, he said, "There are no signs or symptoms of the AAA until it reaches a pretty good size. We recommend a screening exam if you are over 60 or if you have family history an exam at 50 years. These [AAAs] grow slowly, about 0.5 cm per year."
Back at the OR table, Rachel moved to secure the graft by ballooning or "ironing out" the graft from top to bottom including both limbs. Arteriograms and IVUS again were used to double check graft placement and preservation of other arteries. All wires and sheaths were removed and the surgical wounds were closed. No anticoagulants were used during the procedure.
The patient was released from the hospital the next day.