Aneurysm - Aortic
Description of Clinical Program
Research Sponsor: Guidant/Endovascular Technologies
The first attempted clinical implant of the Guidant/EVT device worldwide took place at UCLA Medical Center on February 10, 1993. The implant was successful, and since then UCLA has maintained the lead, with the largest single institutional experience using this new, less invasive technique.
The objective of repair of abdominal aortic aneurysm is to prevent fatal rupture while, at the same time, minimizing morbidity and mortality from the operation.
There are approximately 40,000 patients undergoing elective repair of abdominal aortic aneurysm in the United States each year. In spite of that, approximately 15,000 patients die from ruptured aneurysm, making aneurysm rupture the 13th leading cause of death in the United States each year. This cause of premature death is entirely preventable providing that patients with abdominal aortic aneurysm can be diagnosed prior to rupture and undergo safe elective repair of the abdominal aortic aneurysm. The diagnosis of abdominal aortic aneurysm can be made quickly, painlessly, and inexpensively, using the technique of abdominal ultrasound examination. Unfortunately, the majority of patients that we see have had their diagnosis of abdominal aortic aneurysm made almost accidentally. Usually an imaging study of the abdomen, done for some other reason, uncovers the presence of abdominal aortic aneurysm. Until we can establish a program of effective ultrasound screening, it is unlikely that death from aneurysm rupture will be significantly reduced.
Elective repair of abdominal aortic aneurysm has matured over the 45-year interval since the first direct surgical repair of abdominal aortic aneurysm was performed. While centers of excellence, such as UCLA, consistently report mortality rates of less than 3.0% for aneurysm repair, multi-institutional community-based studies suggest that the mortality rate for elective aneurysm repair ranges from 6.0% to 10.0% each year. In addition, conventional surgical repair of abdominal aortic aneurysm represents a very major operation through a large abdominal incision, which requires at least a week in the hospital and perhaps one to two months before the patient is fully recovered and returns to the preoperative state of well being.
Endovascular repair of abdominal aortic aneurysm offers the advantage of a minimally invasive technique, a hospital stay of one to two days, a rapid return to normal physical activity, and a reduction in the mortality and complication rate when compared with the conventional surgical procedure.
Endovascular repair of abdominal aortic aneurysm utilizes access to the vascular system, through the femoral artery, to place a graft of appropriate design in the abdominal aorta in order to remove the aneurysm from the pathway of bloodflow and thus eliminate the risk of rupture. This technique uses the same graft material, woven polyester, as that used for conventional aneurysm repair. A self-expanding stent with hooks that engage the wall of the aorta and iliac arteries become a substitute for suture material. When the operation is completed, there is essentially the same reconstruction as would have been achieved with conventional open repair with the exception of the fact that a major abdominal incision is avoided with the substitution of one or two small incisions over each femoral artery in the groin.
At the present time, the Guidant/Endovascular Technologies device offers three different graft configurations, depending upon the anatomic problem with which we are presented. For patients with an abdominal aortic aneurysm that is limited to the aorta, and in whom there is both a neck between the renal arteries and the aneurysm as well as a neck between the lower portion of the aneurysm and the iliac bifurcation, a graft of tubular configuration is available. For those patients in whom the abdominal aneurysm extends to the iliac bifurcation, a bifurcated or Y-shaped graft is available. For those patients who have both an abdominal aortic aneurysm as well as an aneurysm of one or both iliac arteries, the third option is a tapered tube graft that excludes both the aortic aneurysm and one iliac aneurysm. The contralateral iliac artery aneurysm is secondarily excluded, and bloodflow to the contralateral leg and pelvic circulation is accomplished with the placement of a subcutaneous crossover graft between the two femoral arteries.
The patient comes to the hospital on the morning of operation and is taken to the operating room. Using either general anesthesia or regional anesthesia, one or both femoral arteries are exposed depending upon the type of reconstruction that is required. A needle followed by a guidewire is then placed in the femoral artery, and the guidewire is extended up the aorta. An angiogram is obtained in order to provide a roadmap image for placement of the device. The patient is then anticoagulated with Heparin and the femoral artery is clamped. A small transverse opening is then made in the femoral artery through which a working sheath is inserted. The sheath then provides a blood-type roadway for placement of the graft/catheter delivery system. If a bifurcated graft is required or an aortoiliac with femoral-femoral crossover, the contralateral femoral artery is also exposed. In the case of the bifurcated graft, the contralateral femoral artery is accessed with a needle puncture followed by the placement of a sheath with a catheter that has a snare system.
In the case of a tube graft, the graft catheter delivery system is passed up through the sheath, over the guidewire, and positioned across the aneurysm. Using remote release levers, the graft is deployed with the upper attachment system immediately below the renal arteries. A balloon within the catheter delivery system is then positioned across the attachment site and expanded in order to seat the hooks into the wall of the aorta. The lower attachment system is then deployed immediately proximal to the bifurcation of the iliac arteries. The balloon is positioned across that attachment site, and the hooks are seated at that point. A completion angiogram is then obtained to make certain that the graft is properly seated and there is no evidence of flow between the graft and the aneurysm, so-called perigraft leak.
In the case of the bifurcated graft, initially a wire that is connected to the contralateral limb of the graft is passed up the ipsilateral side, captured with a snare, and drawn into the contralateral side. The graft/catheter delivery system is then advanced over a guidewire, and a jacket that covers the graft is retracted, thus allowing the two limbs of the graft to separate. The graft is then brought down and appropriately positioned with the proximal attachment system immediately below the renal arteries and each iliac graft limb in their appropriate ipsilateral and contralateral iliac arteries. The attachment systems are then sequentially deployed, and each attachment system is seated with inflation of a balloon catheter. Once completed, the opening of the femoral artery(s) is repaired. The femoral incision sites are closed, and the patient is returned to the recovery room for initial observation. Following that, the patient is sent to a regular hospital bed for an overnight stay. If the patient is feeling hungry that evening and has had no untoward effects from anesthesia, a light meal is served. The following morning the patient is discharged from the hospital. A return visit is accomplished within the first seek, at which time a repeat CT scan and plane abdominal films are obtained in order to make certain that the graft is functioning properly. The femoral incisions are usually well healed within one to two weeks, and the patient returns to normal physical activity.
Results of the UCLA Trial
The UCLA Medical Center is now one of 22 medical centers, nation wide, that have participated in an FDA-monitored investigation of this technique. Between February 1993 and June 1999, 128 patients have been treated with endovascular repair. The implant was successful in 92% of the patients attempted, with 8.0% being converted to a standard open repair. There has been no surgical mortality (30-day) in patients undergoing successful endovascular repair. A recent study, carried out at our institution, compared the first 100 patients undergoing endovascular repair with 100 patients undergoing conventional repair during the same time interval. endovascular repair was associated with a reduced morbidity, shorter hospital stay, and a quicker return to the patient’s preoperative status. There have been no ruptured of abdominal aortic aneurysm that occurred during the follow-up interval. Long-term survival of the two groups are equal and are equivalent to an age-adjusted population without aneurysm disease. Thus, once the aneurysm is treated, the patients return to their usual life expectancy.
The investigational phase of this device has now been completed. The national results, including the UCLA series, have been presented to the FDA panel in June, and received the panel’s recommendation to the FDA for conditional approval. The FDA is currently reviewing the data, including the panel’s recommendation.
During the past six years, it has become apparent that endovascular repair of abdominal aortic aneurysm, in properly selected patients, is safe, efficacious, and durable. The challenge for the future will be to downsize and simplify the devices that are available. In addition, device modification should enable a larger percentage of patients with abdominal aortic aneurysm to be treated by an endovascular approach. We are currently working with new and improved devices that are designed to meet those objectives.
For More Information Concerning Participation: Contact the Gonda Vascular Center at UCLA Clinical Studies Office (310) 206-1115.
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