| Arterial aneurysms have been recognized from antiquity with abdominal aortic aneurysms first described by Vesalius in the 16 th century. An arterial aneurysm is currently defined as a focal enlargement 50% greater than the adjacent normal sized artery. There are many etiologies of arterial aneurysms including infection, trauma, congenital aneurysms, vasculitis, and disorders of collagen. The most common type of aneurysm is the nonspecific degenerative aneurysm previously referred to as atherosclerotic aneurysm. Abdominal aortic aneurysms account for the majority of arterial aneurysms with thoracic aortic aneurysms next most common. |  |
| Abdominal aortic aneurysms are a significant health
problem effecting 3-4% of adults over the age of 65. They are five times
more common in men than women. The incidence of aortic aneurysms is
increasing because of increased detection with CT, MR and ultrasound
which frequently demonstrate aortic aneurysms in asymptomatic patients
undergoing imaging for unrelated reasons. Fortunately most of these
aneurysms are small and do not represent an immediate risk to the
patient. Abdominal aortic aneurysms have been observed to increase in diameter at a rate of 10% or 0.25 to 0.3 cm per year. The most common complication of abdominal aortic aneurysm is rupture and this risk is clearly related to aneurysm size. The risk of rupture of an aneurysm less than 5 cm in diameter is less than 1% per year . This risk increases to 11% per year for aneurysms from 5 to 6 cm in diameter and 25% per year for aneurysms greater than 6cm in diameter. |
| Rupture of an abdominal aortic aneurysm is a catastrophic event. It is estimated that 50% of patients with ruptured abdominal aortic aneurysms die before reaching the hospital, and of the patients presenting to the hospital another 40% die before surgery. Fifty per cent of patients undergoing surgical repair die. There has been little change in this mortality over the last 25 years in spite of advances in surgical care. These depressing figures underline the importance of the diagnosis of and elective repair of abdominal aortic aneurysms 5 cm or greater in diameter. |  |
| There have been many approaches to abdominal aortic aneurysm repair. Historically these include aortic ligation above and below the aneurysm, packing the aneurysm with wire to induce thrombosis, and even introduction of electric current to thrombose the aneurysm. Surgeons have wrapped aortic aneurysms with cellophane to reinforce their walls and prevent rupture. This procedure was performed on Albert Einstein who unfortunately succumbed to aneurysm rupture six years later. |
| The modern treatment of abdominal aortic aneurysms, pioneered by DeBakey, consists of incision of the aneurysm sac, ligation of aortic branches originating from within the aneurysm and placement of an interposition graft within the aneurysm sac. In contrast to emergency repair, the mortality of elective repair of abdominal aortic aneurysms is 3-5% when performed by experienced surgeons at centers performing adequate numbers of aneurysm repairs. Unfortunately many patients with abdominal aortic aneurysms are elderly and have comorbid conditions which contribute to the morbidity and mortality of aortic aneurysm repair. |  |
| The goal for minimally invasive treatment of vascular disease, pioneered by the work of Charles Dotter in the1960’s, has led to the development of endovascular therapy. With this, there has been an evolution in the technology of angioplasty and endovascular stents. The concept of treating aortic aneurysms with endovascular techniques became a reality with the development of the current generation of self- expanding and balloon expandable endovascular stents. Following peripheral access from the femoral or iliac artery, graft material is delivered from within the arterial system across the aneurysm and secured in place with endovascular stents which replace the surgical suture line. The technique has evolved from the work of Parodi who sutured a Palmaz balloon expandable stent to the proximal portion of a Dacron graft. The stent and graft were mounted co-axially on an angioplasty balloon and advanced so that the proximal portion of the graft and stent were positioned just below the renal arteries. As the delivery sheath was retracted the balloon was inflated, expanding the stent and opposing the graft to the aortic wall. With continued retraction of the sheath, the remainder of the graft was deployed and the distal portion of the graft was opposed aortic wall with a balloon expandable Palmaz stent. This design was limited to tube grafts and suitable for aneurysms that ended above the aortic bifurcation. |
 
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| Current stent graft design includes both tube grafts and bifurcated grafts. Grafts which are supported throughout with stents are referred to as covered stents. Grafts with stents at only the proximal and distal attachment sites are called stented grafts. There are advantages and disadvantages to each of these stent graft designs. Covered stents are less likely to kink or obstruct at bends or sites of narrowing in the arterial system. Stented grafts offer a greater capacity to yield to conformational changes in the aortic aneurysm following exclusion from the circulation with subsequent aneurysm shrinkage. Stent grafts are designed as modular grafts in which the body of the graft and one limb are deployed as a single component. The second limb of the graft is docked in the graft body from the contralateral side. A uni-body or one piece grafts consists of an aortic and both iliac limbs which are introduced from one side. After introduction , the contralateral iliac limb of the graft is pulled across the aorta to the contralateral iliac artery. The disadvantage of modular systems is the potential for graft components to separate and allow arterial flow to return to the aneurysm. |  Animation of
bifurcated modular stent graft |
| Anatomic considerations are important in patient selection for stent graft placement. Currently patients must have a 1.5 to 2 cm neck of normal aorta below the renal arteries and above the aneurysm to provide a site for stable fixation of the graft to the arterial wall. In addition the aortic neck must be 26 mm or less in diameter and be free of circumferential thrombus. The angle that the aneurysm and aortic neck makes with normal aorta must be less than 60 degrees. The access arteries that is the external iliac and common iliac arteries must be large enough to accept the devices and therefore exceed 7 mm in diameter. If the external iliac arteries are less than 7 mm in diameter cutdown on the common iliac artery can be performed for carrier placement. The common iliac arteries, the landing zone for the graft limbs, should be 13 mm or less in diameter. Angulation of the common iliac arteries if excessive present an impediment to advancement of the stent graft carrier. Extensive calcification of the aortic neck or the iliac arteries may inhibit introduction and deployment of the stent graft. |  |
| There are currently two FDA approved stent grafts. The AneuRx stent graft is a modular covered stent . It consists of a tube with a long and short limb and a separate contralateral limb. The tube with ipsilateral long and contralateral short limb is deployed in the abdominal aorta with the long limb extending into the ipsilateral common iliac artery. A sheath is introduced from the contralateral femoral artery for deployment of the contralateral limb. A guidewire is directed into the short limb and over this wire the contralateral limb is introduced and docked in the short limb of the graft. This contralateral limb extends from the body of the graft to the contralateral iliac artery. |  |
| The Ancure stent graft is a uni-body bifurcated stented graft. A guidewire which is attached to the contralateral limb of the graft is first introduced into the abdominal aorta and captured with a snare introduced from the contralateral side. This wire is pulled outside the patient through a sheath in the contralateral femoral artery. The graft with both iliac legs is the introduced through a sheath from the ipsilateral femoral artery to abdominal aorta above the aortic bifurcation. The stent graft is unsheathed and the contralateral limb of the graft pulled toward the contralateral iliac artery. The stent graft is slowly pulled down so the proximal end of the stent graft is positioned just below the renal arteries and the ipsilateral and contralateral limbs positioned in their respective common iliac arteries. The stents securing the aortic component of the graft and the iliac limbs of the graft are self expanding stents with hooks which are embedded in the arterial wall using an angioplasty balloon. |  
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Animation uni-body bifurcated stent graft placement |
| As experience with endovascular treatment of abdominal aortic aneurysms increases, it appears that about 30 – 60% of patients with abdominal aortic aneurysms are candidates for stent graft repair. Endografts are successfully deployed in 80 to over 90% of patients. While complications are reported in 25 to 60% of patients undergoing endovascular repair, they adversely effect the in the minority of patients. |  Real Video |
| Shared disadvantages of the currently available stent grafts are the requirement for large diameter sheaths for introduction of the stent graft. This can cause injury to the access artery, one of the most common complications of stent graft placement. Embolization of thrombus from the aortic aneurysm or iliac arteries is another complication contributed to by the large diameter of the delivery system. Stent grafts may be deployed at the incorrect level or migrate into the aneurysm during deployment . Contrast related renal insufficiency from peri-procedural arteriography has been reported in patients with impaired renal function. Excessive blood loss during stent graft deployment, a major complication of early devices, is less common with current delivery systems. |
| Endoleak is a common complication observed in up to 45% of patients undergoing stent graft repair of abdominal aortic aneurysms. An endoleak is caused by incomplete exclusion of the aortic aneurysm from the arterial circulation by the stent graft. This may occur because of continued arterial flow into the aneurysm sac around the proximal or distal ends of the stent graft. This is called a type 1 endoleak and is the type of leak most often associated with delayed aneurysm rupture following stent graft repair. The aneurysm sac may also continue to fill because of retrograde flow into the aneurysm from the lumbar arteries , the inferior mesenteric or the internal iliac arteries. These are called type 2 endoleaks. Type 3 endoleaks occur from separation of the components of modular grafts or tears in the graft fabric itself. Type 4 endoleaks are ooze of blood through the graft material. This resolves spontaneously. Type 1 endoleaks must be repaired at the time of diagnosis either by further approximation of the stent graft to the arterial wall with an angioplasty balloon or additional stent placement. Introduction of extender stent grafts may be required to treat the leak. If these maneuvers are unsuccessful surgical repair of the aneurysm becomes necessary. Surgical repair or the introduction of a st ent graft within the stent graft is required for type 3 endoleaks. Type 2 endoleaks may resolve spontaneously in up to 50% of patients. If the leak does not resolve it may be treated by embolization of the collateral vessels filling the aneurysm sac or by placement of metal coils in the aneurysm sac. The most feared complication of endovascular repair of abdominal aortic aneurysms is delayed rupture of the aneurysm. This is a very unusual complication, however the follow up of patients undergoing endovascular aneurysm repair is still short. |
Real Video
| The procedure related mortality of aortic stent graft
placement, in the most recent reports in the literature, is 0 – 3% and
not dissimilar to that following elective surgical repair of abdominal
aortic aneurysms. The major advantage of endovascular repair of aortic
aneurysms is that it is a less invasive procedure, imparts less stress
on the patient and therefore requires a shorter recovery period.
Transfusion requirements and length of stay in the intensive care unit
are significantly reduced in patients undergoing endovascular repair.
Decreased recovery time permits many patients to be discharged from the
hospital within one or two days of the procedure, with return to normal
activity in one to two weeks. It comes as no surprise that the results
of endovascular stent grafting are dependent on the overall experience
of the center performing the procedure and the procedure volumes of the
operators, reflecting a relatively steep learning curve for the
procedure. While long term follow up of patients undergoing stent graft repair of abdominal aortic aneurysms is necessary before accurate comparison with open surgical repair can be made, the early results are promising. Our experience includes the use of both custom stent grafts and the FDA approved devices. This experience has been gained both in the laboratory and in clinical placement of stent grafts starting five years ago with the treatment of thoracic aortic aneurysms with a custom designed stent graft. Taking advantage of the resources of the Vascular Center of New Jersey, through the collaboration of experienced Vascular Interventional Radiologists and Vascular Surgeons, we have had success with treatment of both routine and complex aortic and iliac artery aneurysms. Currently we treat the majority of abdominal aortic aneurysms with the bifurcated one piece Ancure device. We have successfully deployed grafts in over 90% of the patient in whom the procedure was attempted. Only one patient required conversion to an open procedure. Endoleaks have been observed in less than 20% of patients. We too are optimistic that endovascular stent graft repair of aortic aneurysms will become an invaluable asset in the minimally invasive treatment of vascular disease. |