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266 Saltzberg, Maykel, and Akbari
Fig. 4. Proximal anastomosis of a graft and aortic remnant.
Patients initially selected for the procedure were considered too high risk for the traditional “open” approach. This group included patients of advanced age, low ejection fraction, poor respiratory function, and prior abdominal operations. Because of its initial
success, ndovascular repair has since been expanded to include lower risk patients. The
most important criteria for suitability are anatomic considerations. These criteria include:
suitable proximal neck (>15 mm length, <28 mm diameter) without thrombus or calcification, suitable distal cuff (>10 mm length, <28 mm diameter), suitable iliac vessels, no
evidence of mesenteric occlusive disease, and no evidence of severe tortuosity (4). Technical aspects, complications and other details are described in Chapter 23.
COMPLICATIONS OF AORTIC SURGERY
Improvements in perioperative management and surgical technique have led to a
significant decrease in operative mortality and morbidity for operations performed on
the abdominal aorta. Most large series published within the past decade have reported
perioperative mortality rates of less than 3–5%, as compared to a greater than 20%
operative mortality three decades earlier (1).
Chapter 22 / Surgery of the Abdominal Aorta 267
Fig. 5. Proximal anastomosis of aortic graft, and visualization of the site for distal anastomosis.
Despite this, however, it must be recognized that clamping of the aorta poses a considerable physiologic strain, and in view of the systemic nature of the atherosclerotic
process, the first consideration should be of prevention and management of cardiac
complications. These may include myocardial infarction (MI), congestive heart failure,
and arrhythmias, and indeed in patients with both occlusive and aneurysmal aortic disease, the most common cause of early and late mortality remains these cardiac complications. Intraoperative hypotension, which also compromises coronary flow, may also
occur. This is usually caused by either intraoperative hemorrhage or following release
of the aortic clamp (declamping hypotension) (5).
Pulmonary complications may also arise in these patients, again owing to the high
incidence of cigarette smoking and preexisting pulmonary disease. Not uncommonly,
postoperative atelectasis and airway collapse may also occur, often accentuating the
already compromised pulmonary status. The reasons for this include the presence of a
nasogastric tube (described in more detail below), which impairs the normal clearance
of secretions, and postoperative pain, which prevents the voluntary mechanisms of
cough and deep breathing. In the patient who has sustained prolonged intraoperative
268 Saltzberg, Maykel, and Akbari
Fig. 6. Completed aortic aneurysm graft repair.
hypotension (from either hemorrhage or declamping), and thus, has required significant
transfusions and fluid, both adult respiratory distress syndrome (ARDS) and congestive
failure may occur. Differentiation of these entities is difficult on clinical judgment alone
and usually requires the added information obtained from a pulmonary artery (SwanGanz) catheter (6).
Acute renal failure complicating aortic aneurysm repair is associated with a greater
than 50% mortality. Two principal causes are nephrotoxic agents (such as radiographic
contrast agents or perioperative antibiotics) and ischemic injury. The latter is more
common, and is typically characterized by oliguria, a rapid rise in the creatinine level,
and electrolyte imbalance. Etiologies of ischemic injury include hypovolemia, prolonged renal artery clamp time, and atheroembolization (typically from injudicious use
of the aortic clamp on a diseased aorta, with subsequent “extrusion” of atheromatous
debris into the renal orifices). In rare instances, and particularly in surgery for large iliac
artery aneurysms and “redo” aortic surgery, ureteral injury may occur, because of its
location anterior to the iliac vessels (6).
A variety of gastrointestinal (GI) complications may be seen after aortic surgery. A
prolonged return of GI function may be secondary to a duodenal ileus, as there is significant retraction of the duodenum in order to expose the proximal aorta. As previously
Chapter 22 / Surgery of the Abdominal Aorta 269
noted, the incidence of ileus, and need for prolonged nasogastric suction may be less with
the retroperitoneal approach. Further cephalad dissection of the aorta also exposes the
inferior border of the pancreas, which may be inadvertently injured, leading to a postoperative pancreatitis. With any type of supravisceral aortic surgery and mesenteric
revascularization, either hepatic or small intestinal ischemic injury may occur, with
resultant acidosis, leukocytosis, enzyme elevation, and even death (6).
Colon ischemia is a well-recognized complication of aortic surgery. The classic postoperative presentation is bloody diarrhea, fever, tachycardia, and leukocytosis. It is seen
more commonly following aneurysm repair, and its incidence is highest in patients undergoing repair of a ruptured aneurysm. The pathophysiology is related to the inferior mesenteric artery (IMA) and collaterals (namely the meandering artery, a marginal artery of
Drummond, and hemorrhoidal vessels from the internal iliac artery) which supply the left
colon. In repair of an abdominal aortic aneurysm, the aneurysm always involves the IMA
orifice, which is therefore ligated when the aneurysm sac is opened. The main blood supply
to the left colon then becomes the meandering artery from the superior mesenteric artery
(SMA) and the internal iliac artery. Colonic ischemia may thereby occur if there is a
stenosis or occlusion of the SMA or internal iliac artery. If the colon appears dusky at the
time of surgery, the IMA may be re-implanted into the aortic graft (6).
Aortoenteric fistula is a late complication following aortic graft replacement. The
majority of these occur at the duodenal level, again due to the location of the duodenum
just anterior to the perirenal aortic segment. Infection is usually an antecedent cause,
with erosion of the graft into the fourth portion of the duodenum. A strong suspicion is
essential for the diagnosis, especially in patients who present with unexplained upper
gastrointestinal bleeding following aortic surgery (6).
Technical complications include peri-operative hemorrhage, either from suture lines
or from inadvertent injury to surrounding veins, mesentery, or spleen. Graft thrombosis
may also occur, again usually due to a technical error.
COST
Several recent studies have evaluated the cost associated with open and endovascular
repair techniques. The average cost for an open AAA repair is $12,000, whereas the
average cost for an endovascular repair is $21,000. Although the endovascular approach
decreases those expenses related to ICU admissions and length of hospital stay, the
overall cost is greater because of the price of the endograft itself, approx $10,000. Furthermore, because there is a new complication of endoleak in some cases of endovascular
repair, periodic CT scanning and additional secondary procedures drive up the long-term
care costs (7).
SUMMARY
1. With an increase in the aging population, there is an expected increase in the number of
patients diagnosed with and treated for aortic pathology. Their care is dependent on an
adequate knowledge of the pathophysiology and anatomy of the disease, along with an
awareness of the surgical technique for repair and potential for complications.
2. The diseases of aorta and its branches can be categorized into aneurysmal or occlusive
diseases. Both categories represent a more generalized disorder affecting cardiovascular system.
270 Saltzberg, Maykel, and Akbari
3. Aortic aneurysm and aortoiliac surgery are formidable operations and despite advances
in the peri- and postoperative management, have significant mortality and morbidity.
4. The risk of AAA rupture increases as the size of AAA increase above 5 cm. Surgical
repair is indicated in these patients. Depending upon the anatomy of the AAA,
endovascular repair is an alternative to surgical repair. It has a lower complication rate
but is more expensive than the surgical repair.
REFERENCES
1. Ernst C. Abdominal aortic aneurysms. N Eng J Med 1993;328:1167–1172.
2. Brewster DC. Current controversies in the management of aortoiliac occlusive disease. J Vasc Surg
1997;25:365–379.
3. Hines GL, Chorost M. Supraceliac aortic occlusion: A safe approach to pararenal aortic aneurysms.
Ann Vas Surg 1998;12:335–340.
4. D’Ayala M, Hollier LH, Marin ML. Cardiothoracic and Vascular Surgery: Endovascular grafting for
abdominal aortic aneurysms. Surg Clin North Am 1998;78:845–860.
5. Jean-Claude JM, Reilly LM, Stoney RJ, et al. Pararenal aortic aneurysms: The future of open aortic
repair. J Vasc Surg 1999;29:902–912.
6. Hermreck AS. Prevention and management of surgical complications during repair of abdominal
aortic aneurysms. Surg Clin North Am 1989;69:869–894.
7. Sternbergh WC, Money SR. Hospital cost of endovascular versus open repair of abdominal aortic
aneurysms: a multicenter study. J Vasc Surg 2000;31:237–244.
Chapter 23 / Repair of AAA 271
23
Edovascular Repair
of Abdominal Aortic Aneurysm
Grant J. Price, MD
CONTENTS
INTRODUCTION
INDICATIONS AND ALTERNATIVES
HIGH-RISK PATIENTS
HOSTILE ABDOMEN
FEMALE PATIENTS
INFLAMMATORY ANEURYSMS
YOUNG PATIENTS
GOOD OPERATIVE CANDIDATES
CONTRAINDICATIONS
TECHNIQUE
PREOPERATIVE IMAGING
ANCILLARY INTERVENTIONS
POSTOPERATIVE IMAGING
COMPLICATIONS AND THEIR MANAGEMENT
ALTERNATIVE PROCEDURE
ADVANTAGES
DISADVANTAGES
COST
SUMMARY
REFERENCES
INTRODUCTION
Endovascular repair of abdominal aortic aneurysm (AAA) has exploded onto the
public scene over the past 2 yr. It is important for the general internist to have a balanced
working knowledge of this subject because: 1) AAA is very common; 2) many patients
have heard about endovascular repairs, and will turn to their internists for advice; and 3)
some of the centers offering endovascular grafting promote themselves in the media in
ways that may not be scientifically balanced.
The pathophysiology and surgical repair of AAA is nicely covered in the previous
chapter (see Chapter 22). Whereas most elective cases can be safely done by conven-
From: Clinical Gastroenterology: An Internist's Illustrated Guide to Gastrointestinal Surgery
Edited by: George Y. Wu, Khalid Aziz, and Giles F. Whalen © Humana Press Inc., Totowa, NJ
271
272 Price
tional “open” technique with excellent and durable outcome, it is fair to say that most
of the morbidity and mortality of conventional open surgery relates to the need to open
the abdominal cavity and to cross-clamp the aorta in order to accomplish the repair.
It is important to note that many if not most patients with a surgical-sized AAA have
concomitant vascular disease in coronary, cerebral vascular, renovascular, and/or
peripheral vascular distributions, all of which may increase the risk of general anesthesia and open surgery.
Because of all of the above considerations, there has been a large research and commercial effort to develop techniques to repair AAA from a “less-invasive” endovascular
approach. Essentially, the goal has been to deliver a vascular graft from inside the artery
to cover and exclude the aneurysm, without cross-clamping the aorta or opening the
abdomen, and ideally without general anesthesia. Early attempts at grafting were made
with relatively crude homemade devices constructed from metallic vascular stents sewn
to standard bypass graft material, but progress has been rapid. The earliest successful
endovascular AAA repairs were accomplished around 1990 (1), commercial devices
were widely available in Europe by 1995, and the FDA issued United States approval of
two of the commercial endovascular AAA grafting systems in late 1999. Thus far, all
announced commercial and investigational endovascular systems are constructed from
a mix of metallic vascular stents and biocompatible cloth or polymer materials (PTFE,
Dacron, and so on) The systems currently approved for use in the United States are:
1. The Ancure device, produced by the Guidant company. This is an evolution of the EVT
device, and was the earliest commercial device to start trials. It is a one-piece design
consisting of a conventional cloth Y-shaped bifurcated graft with stented attachments at
each of its ends. The entire assembly is folded into a large-bore introducer, and advanced
and positioned from a bi-femoral approach (2).
2. The AneurRx device produced by Medtronic. This is a modular device, consisting of a
series of variously shaped metallic stents covered with cloth. These are placed sequentially
from a bi-femoral approach in order to build up a Y-shaped graft inside the patient (3).
As of this writing, there are at least a half-dozen other systems in various states of
development, many of them already commercially available outside the United States.
All of the announced investigational devices are of the modular variety.
It should be noted that part of the FDA approval of the devices was a requirement that
the manufacturers provide 2-d “hands-on” training courses to all operating physicians
before selling them the grafts. This requirement set off a scramble among interested
physicians to gain entry into the courses, and initially engendered a de facto segregation
of the procedure to larger, higher volume centers, as the companies initially focused their
attention on those physicians who were likely to purchase the largest number of grafts.
By the time of this writing (2002), many community hospitals have achieved
credentialing, and the number of institutions offering endografting is growing rapidly.
As we shall see in the following sections, endovascular repair of AAA is a promising
technique, but is still early in its evolution, and entails considerable compromises relative to conventional repair. Despite the commercial availability of endograft systems,
tremendous enthusiasm among vascular physicians for the technique, and the real benefit accrued by some high-risk patients, many AAAs cannot yet be repaired by
endovascular techniques, and many others probably should not be. One supporting piece
of evidence for this assertion is the sobering fact that each of these devices has had an
Chapter 23 / Repair of AAA 273
interval of nonavailability owing to regulatory issues arising after FDA approval. The
regulatory climate is changing rapidly, and the reader is directed to the web address listed
in ref. 11 for up-to-the-minute information. If what follows seems more an editorial than
a scientific article, we ask the reader to understand this as an indication of the current
state of the data.
Required Resources for Endovascular Grafting
Little in the way of specialized equipment is needed to place stent grafts. The procedure can be done in any institution with an operating room (OR), a modern c-arm
fluoroscope with a basic angiographic package, and one or more qualified physicians.
Most endovascular grafts are placed in the OR using a portable c-arm for imaging
guidance, although some centers have constructed specialized angiography suites with
OR-standard sterile environments, and a few have installed full-range angiography
equipment in their operating rooms. Much of this is driven by “turf” issues within a
given institution. Operating physicians come from the realms of Vascular Surgery,
Interventional Radiology, and Interventional Cardiology, often working in multispecialty teams. In this author’s opinion, the current ideal is a team consisting of a
vascular surgeon and an interventional radiologist. This is the combination most likely
to have the accumulated skills necessary to successfully address any unanticipated problems that occur during deployment of a graft. Whereas a routine procedure requires lowend surgical skills and medium catheter manipulation skills, the need for high-end
surgical and/or catheter skills can develop very, very quickly during a graft deployment.
INDICATIONS AND ALTERNATIVES
It would be very easy to say that the procedure is indicated for anyone having an AAA
larger than 5 cm who can be fitted for an endograft. However, there is much that is not
known about the long-term durability of the devices, and the endoleak/endotension issue
(see later) is far from settled. It is also important to understand that there has been a rush
to the market with these devices, and the available controlled trials are not up to the task
of defining indications for many patients. It is fair to say that at the current state of the
art, many patients’ suitability for endovascular rather than open repair is as much a
matter of opinion and preference as it is a matter of science.
It is important to understand that the currently available devices simply will not fit a
significant percentage of patients. The reasons for exclusion are numerous and generally
involve an infrarenal neck that is too short or wide, an aneurysm that is too angulated or
iliac arteries that will not permit passage of the introducer. Many investigators claim that
as many as 40–60% of patients are anatomically suitable for endografting with the
commercially available systems. In this author’s experience, that number seems high,
possibly relating to selection bias at the larger referral centers. The real number is
probably closer to 30%.
HIGH-RISK PATIENTS
It is fair to say that endovascular grafting is definitely indicated for patients that have
“surgical” sized AAA can be fitted with a device, and are at high risk for conventional
repair because of concomitant coronary artery disease, COPD, or other co-morbidity.
274 Price
HOSTILE ABDOMEN
Patients with surgically hostile abdomens caused by radiation, inflammatory bowel
disease, adhesions, multiple surgeries, or other conditions that would increase the difficulty of an open repair, are good candidates for endografting.
FEMALE PATIENTS
Females generally are less likely to pass anatomic criteria for endografting, usually
because of smaller iliac arteries. However, women who are successfully grafted probably do about as well as men (4).
INFLAMMATORY ANEURYSMS
These rare, but difficult cases were until recently a terra incognita for endografts.
A recently published series of two patients suggest that endografting might not only
exclude the aneurysm, but stop the inflammatory process (5). Given that the complication rate of conventional repair is considerable in inflammatory aneurysm, it is
reasonable to consign these patients to endografting when anatomically possible.
YOUNG PATIENTS
As of this writing, the oldest implanted Ancure device of current design has been in
place about 6 yr, and the oldest implanted AneuRx device for less than that. In my
opinion, the current endografts should be considered to be of unknown and suspect
durability for patients with long horizons, and those patients should be guided toward
conventional repair.
GOOD OPERATIVE CANDIDATES
These patients constitute by far the largest group of AAA patients. It is currently
difficult to say which of them should be treated by which method; decisions are currently
driven by patient and physician choice.
CONTRAINDICATIONS
Inability to fit the AAA with a graft is by far the most common exclusionary factor
for endografting.
Mycotic AAA
This should be treated with open excision and extraanatomic bypass in most cases
because of the high likelihood of infection of an endograft. There have been a few
reported cases of successful endografting of mycotic aneurysms in the thoracic aorta.
Acutely Ruptured AAA
Although there have been a few reported cases of successful endovascular repair of
acute ruptures, this is not generally indicated. Sizing of grafts without preoperative work
up is problematic, and the leaking aneurysm is not effectively sealed until the procedure
is complete. The possibility also exists of worsening the leak by manipulating the large/
stiff equipment inside of the disrupted AAA. A further practical issue is that many
Chapter 23 / Repair of AAA 275
centers buy these expensive devices per patient, and do not have a depth of inventory to
provide a device in an emergency.
TECHNIQUE
The discussion of technique is complicated by the fact that there are two different
types of grafts (unibody vs modular), and three basic shapes (tube, aortouniiliac, and
bifurcated). Readers are referred to the illustrations for further description.
Tube grafts were the majority of early devices used. They can be used only when
there is a long usable segment of normal aorta distal to the aneurysm in which to secure
the distal end of the graft. This is not a common circumstance, and only a few patients
are candidates for tubes. An important consideration is that the part of the aorta comprising the infrarenal neck is physiologically stronger than the rest of the infrarenal
aorta in that it has more elastin fibers in its wall. The distal landing zone for tube grafts
is physiologically the same as the part of the aorta that became aneurysmal in the first
place, and is, therefore, subject to expansion and weakening over time. There are
reported cases of this leading to delayed leaks. Tube grafts are rapidly falling out of
favor; most centers use them in specialized circumstances or not at all.
Aortouniiliac grafts are one-piece grafts that bridge the infrarenal neck through the
AAA and into one common iliac artery. The opposite common iliac artery must be
occluded (naturally or by intent) in order to cut it off from the AAA, and a femoral to
femoral crossover graft is also required to supply the opposite leg. Aortouniiliac grafts
were initially developed as a compromise solution for high-risk patients who needed
endovascular treatment, and were not anatomically suitable for tube grafts. That application has been supplanted by the development of bifurcated systems. However, the
aortouniiliac systems are still occasionally useful for patients who have only one iliac
artery that would accommodate placement of a graft.
Bifurcated systems currently comprise the vast majority of cases being done. They
bridge from the infrarenal neck into both common iliac arteries (Fig. 1). The following
technical discussion is for a bifurcated system; keep in mind that the following is an
average technical description and that variations on the theme are both legion and beyond
the scope of this volume.
1. Access to both common femoral arteries is obtained via surgical cut-down.
2. Guidewires are manipulated from both sides to a point well above the neck of the AAA.
3. An angiogram is performed. The positions of all key structures (renal arteries, aortic
bifurcation, iliac bifurcation, and so on) are marked.
4. The delivery device containing the graft (one-piece system) or the aortoiliac body of the
graft (modular system) is advanced over one of the guidewires and positioned appropriately. In general, the side with the widest/straightest iliac system is chosen to be the
“ipsilateral” one for this because the systems are big (18–28 fr), very rigid, and must be
advanced with care.
5. Via the contralateral side, a snare catheter is advanced and used to capture the contralateral
limb of the device (one-piece graft), or a catheter is left in place in the iliac system to use
in deploying the contralateral component once the main body is deployed (modular).
6. The introducer sheath is retracted, deploying the aortic and ipsilateral iliac limb (both
types). These are smoothed down and tacked into place using a balloon catheter.
7. If the graft is a unibody system, the contralateral limb is pulled into place, deployed, and
ballooned. At this point, grafting is complete, and the AAA excluded. Proceed to step 9.
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