P&S Journal: Winter 1996, Vol.16, No.1
Graft for Aortic Aneurysms
By Nicholas P. Christy'51
Abdominal aortic aneurysms are essentially time bombs waiting to go off. For white males over age 55, this hidden affliction ranks among the top 10 causes of death. Currently, the only treatment is surgery, which must sometimes be delayed until the aneurysm grows large enough that its seriousness equals the inherent risks of surgery. Dr. Timothy A.M. Chuter, assistant professor of surgery and assistant attending vascular surgeon, and colleagues have developed a novel, minimally invasive procedure that may allow physicians to treat this condition early and without the risks of surgery.
Dr. Chuter developed an endovascular graft-stent prosthesis that is placed at the site of the aneurysm, taking the place of the enlarged vessel, thus preventing blood flow through the aneurysm, which then clots. Thus, the risk of rupture is avoided (or eliminated). The placement of the prosthesis does not require open abdominal surgery; rather, the prosthesis is delivered via a catheter through the femoral and iliac arteries to the site. An angiogram and CT scan are used to determine the proper length of the graft before the procedure.
Under general or local anesthesia, an incision is made in the groin on both the left and right sides to expose the femoral arteries. A cross-femoral catheter is inserted through the left iliac artery and pulled down the right iliac artery to the right groin. A guidewire is inserted through the right side into the proximal aorta. The graft delivery system is then inserted over this guidewire and positioned above the aneurysm. The stent is expanded, which seats the graft just above the aneurysm, and the graft is pulled down to create an internal bypass of the vessel. Fluoroscopy guides the manipulation of the catheter and wire and positioning of the stents.
Dr. Chuter's device differs from an earlier version developed by Dr. Juan Parodi at Bowman Gray School of Medicine because of the bifurcation component and a smaller delivery system. This graft can be seated down the right and left iliac arteries beyond the distal end of the aorta. "This is advantageous because aneurysms often extend to or beyond the point where the aorta bifurcates," says Dr. Roman Nowygrod, professor of surgery and a colleague of Dr. Chuter's. Thus, the use of the bifurcated graft makes the procedure more suitable than non-bifurcated grafts for a greater number of candidates. The bifurcated graft also makes attachment and anchoring of the graft to the aorta less complicated.
So far, this procedure has proved highly efficacious in both animal studies and preliminary clinical trials. Human trials in the United States have just begun. For now, the procedure is available on a "compassionate need" basis in high-risk patients at CPMC. Worldwide, the procedure has been used in more than 40 cases. Dr. Chuter's team has performed three procedures at CPMC, all of which were successful, although one patient died of unrelated heart disease.
One of the patients who benefited from the procedure suffered severe chronic obstructive pulmonary disease, which required lung reduction surgery (see next Clinical Advance), a surgical procedure that could not be safely performed until a large aortic aneurysm was repaired. The patient was able to have the endovascular procedure followed by lung reduction surgery without the risk of aneurysm rupture.
Dr. Nowygrod believes the procedure will become more widely used in the United States and will be shown to be appropriate for aneurysms of all sizes.
Currently, physicians must weigh the risks involved in surgery against the risk of rupture in deciding when to operate on an aortic aneurysm. For small aortic aneurysms, physicians often recommend watchful waiting, which generally means performing an ultrasound examination every six months. No medication has been proved to reduce the growth rate of aortic aneurysms.
Because the new procedure is minimally invasive and requires only a short hospital stay, Dr. Nowygrod predicts it will be used for repairing aneurysms at an earlier stage. The procedure requires a hospital stay of two to three days, as opposed to an average of 10 to 14 days with surgery. Prolonged disability is virtually eliminated.
About 4 percent of men over age 65 are diagnosed with aortic aneurysms annually, and better imaging techniques will result in increased diagnoses. Early diagnosis and treatment is particularly appealing considering that a ruptured abdominal aortic aneurysm causes shock and death in most cases and that the best predictor of risk for rupture is the size of the aneurysm.
Dr. Chuter's stent-graft prosthesis appears to have the potential to be a powerful tool for defusing aortic aneurysms.