Aortoiliac Occlusive Disease Treatment & Management

The 2 goals for the clinician treating aortoiliac occlusive disease (AIOD) are (1) improving symptoms and (2) reducing the associated risk of myocardial infarction, stroke, and vascular death. Three fundamental principles are involved in the treatment of symptomatic peripheral arterial disease (PAD) due to aortoiliac occlusive disease (AIOD).

First, the risk factors must be identified and aggressively treated. The 2 most important risk factors for peripheral arterial disease (PAD) are cigarette smoking and diabetes. Complete cessation of smoking is mandatory. Carefully regulate serum glucose. The goal for adequate glucose control is an Hgb A1c level lower than 7%. The goal of hypertension control should be blood pressures lower than 140/90 mm Hg. Finally, the LDL cholesterol level should be reduced to less than 100 mg%. This usually can be accomplished with the use of hepatic 3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (statins). In addition to modification of risk factors, patients with aortoiliac occlusive disease (AIOD) should receive lifelong antiplatelet therapy to reduce the risk of myocardial infarction, stroke, and vascular death.

Secondly, initiate a walking exercise program. No fewer than 28 prospective randomized clinical trials attest to the efficacy of walking exercise to treat claudication.^{[7, 8]} Every trial has demonstrated improvements in walking distance from 180-340%. Supervised walking programs usually produce better results than unsupervised exercise. Walking exercise even has been compared to angioplasty and found to produce superior results. Walking exercise improves symptoms of claudication because the muscle enzymes involved in oxygen extraction and utilization become more efficient over time.

Finally, 2 Food and Drug Administration (FDA)–approved pharmacologic agents may improve the symptoms of claudication caused by lower extremity arterial occlusive disease. Pentoxifylline is a methyl xanthine derivative that acts as a hemorheologic agent, lowering blood viscosity. Unfortunately, pentoxifylline only is effective in 30-40% of patients and must be taken 3 times daily. If it is effective, walking distances only improve modestly. Cilostazol, on the other hand, is a newer agent that belongs to the class of phosphodiesterase III inhibitors and has been shown to be more effective statistically than either pentoxifylline or placebo. The mechanism of action is not well understood. Adverse effects may include headache and loose stools, but the medication generally is well tolerated. It should not be used in patients with significant congestive heart failure.

Direct arterial reconstruction on the diseased aortoiliac arterial segment is well established. Aortoiliac endarterectomy (TEA) and aortobifemoral bypass (AFB) are the 2 traditional means of surgically treating aortoiliac occlusive disease (AIOD). Both procedures have similar risk and results, and the outcomes have stood the test of time. In 1966, Blaisdell introduced axillofemoral bypass as an extra-anatomic technique for improving inflow to the lower extremities without the need for an abdominal procedure.^[9] More recently, with the advent of arterial stents, endovascular repair of aortoiliac lesions has become a reasonable alternative to consider if the pathologic anatomy is suitable.

TEA of the aorta and iliac arteries was the first reconstructive procedure performed for aortoiliac occlusive disease (AIOD). The concept is simple. A dissection plane exists between the arterial media and the obstructing plaque. When the appropriate plane is entered, the arterial intima, plaque, and internal elastic lamina of the media are removed as a single specimen. Early in the experience, surgeons were concerned that the remaining portion of arterial wall was not sturdy enough to hold blood under arterial pressure.

However, with more experience, it became clear that the remaining portion of the vessel (external elastic lamina of the media and adventitia) following TEA provided a secure and durable conduit with excellent long-term patency. When aortoiliac TEA is used to treat patients with type I atherosclerotic occlusive disease, the patency rates are excellent. However, the results are not as good when TEA is applied to patients with more extensive distal occlusive lesions in the external iliac and femoral arteries.

Today, aortoiliac TEA is not used as commonly as AFB, primarily because the procedure is best suited for patients with type I atherosclerosis, occlusive disease limited to the infrarenal aorta and common iliac arteries, as depicted in the image below. Patients with type 1 atherosclerosis comprise the minority of patients with PAD. Furthermore, younger surgeons may not have had proper exposure to the technique of aortoiliac TEA during their training and therefore do not have appropriate experience using the procedure to treat aortoiliac occlusive disease (AIOD).

Aortoiliac TEA has significant advantages over conventional AFB for the treatment of aortoiliac occlusive disease (AIOD). First and most obvious is that prosthetic material is not needed to perform the arterial reconstruction. Even for the most experienced surgeons, aortic prosthetic graft infections occur in 0.5-3% of patients following AFB. The mortality rate associated with the treatment of aortic graft infection ranges from 11-27%. In addition, a similar rate is observed for early amputation following aortic graft infection.

Many patients undergo aortoiliac TEA not for the indication of removing the plaques that obstruct blood flow, but rather to remove the source of atheroembolism causing blue toe syndrome. Aortoiliac TEA is ideally suited for this indication because the offending degenerated atheroma is removed, leaving a clean, glistening surface that soon is covered by new functional endothelium.

The only significant disadvantage of TEA compared with AFB is that a larger, more meticulous dissection is required to expose and control the branches of the infrarenal aorta. For this reason, some surgeons may opt for AFB even if the occlusive process is limited to the infrarenal aorta and common iliac arteries.

Finally, aortoiliac TEA should not be performed if occlusive plaques involve the more distal external iliac and femoral arteries. The "tail" of the atheroma in the common iliac artery may extend into the orifice of the external iliac artery, and this tongue usually is removed easily during the course of the procedure. However, if diffuse disease exists in the more distal external iliac and femoral arteries, AFB is a more suitable alternative.

AFB is the most common open surgical alternative used to treat aortoiliac occlusive disease (AIOD). In the early experience of aortic surgery, unilateral AFB or even aortoiliac bypass (AIB) often was performed to limit the extent of the procedure. However, as more experience was gained with these operations, using the common femoral arteries as the outflow target clearly produced better long-term patency results. Unilateral AFB is performed infrequently today because the extremity that was neglected initially seldom truly is healthy and invariably demonstrates symptoms from progressive atherosclerosis. Therefore, performing AFB bilaterally to avoid the need for subsequent inflow operative procedures on the limb that demonstrates less extensive occlusive disease is appropriate.

The original approach to AFB was transabdominal. As an alternative approach, retroperitoneal exposure of the aorta can be used to avoid entering the peritoneum. Some authors have advocated this approach based upon a theoretical advantage of fewer pulmonary problems, more rapid resolution of postoperative ileus, and fewer days in the hospital. Other studies have not supported this proposed benefit.

In some circumstances, a bypass serving both legs can be constructed using a single common iliac artery as the donor site. This procedure can be performed through either a transperitoneal or retroperitoneal approach.

For higher-risk patients who are less likely to tolerate an abdominal operation, extra-anatomic bypass was developed in the mid 1960s. Axillobifemoral bypass provided an extracavitary means of improving blood flow to the lower extremities. This procedure proved especially useful in the treatment of aortic graft infections. However, the long-term patency of extra-anatomic bypass is distinctly inferior to conventional aortobifemoral bypass.

With the advent of percutaneous transluminal angioplasty (PTA) and stents, excellent minimally invasive alternatives to conventional open reconstructive surgery now are available. If applied to the appropriate anatomical problem, the results of iliac angioplasty/stent placement rival open surgical results. For isolated segmental common iliac artery stenoses, angioplasty/stenting rivals open surgical results. However, for occlusive disease that diffusely involves the aortoiliac segment, direct open surgical repair still offers the best long-term outcome. However, through catheter-based treatments (angioplasty/stenting), patients with significant operative risk due to comorbid diseases can be offered therapy.

Because most patients with aortoiliac occlusive disease (AIOD) are older than 50 years, finding associated ischemic heart disease is not uncommon, even if classic anginal symptoms are not present. Hertzer and colleagues found that most patients undergoing aortic operations for arterial occlusive disease had diseased coronary arteries when coronary arteriography was performed. Moreover, Porter and associates found a significant incidence of occlusive plaques in the carotid arteries in a similar group of patients. Clearly, aortoiliac occlusive disease (AIOD) does not exist in a vacuum. However, despite the association of coronary and extracranial arterial occlusive disease with peripheral arterial disease (PAD), every patient clearly does not need an extensive preoperative evaluation prior to undergoing aortic surgery.

Preoperative cardiac evaluations are reserved for patients with either an abnormal finding on ECG and/or a history of new-onset or unstable angina or with symptoms of ventricular dysfunction (orthopnea, dyspnea on exertion). Patients who have had coronary angioplasty or bypass or who have a history of stable angina on appropriate medication probably do not need a preoperative cardiac evaluation, unless a change has occurred in either exercise tolerance or anginal pattern.

Immediately before the induction of anesthesia, the anesthesiologist places an epidural catheter. Although the catheter is not used during the procedure, the analgesic relief provided by instillation of narcotic and local anesthetic agents in the postoperative period is invaluable.

In addition, a systemic dose of perioperative cephalosporin antibiotic is administered intravenously before the skin incision is made. The antibiotic is continued postoperatively for 24-28 hours to lower the risk of graft infection.

Both of the conventional surgical procedures used to treat aortoiliac occlusive disease (AIOD), TEA and AFB, are performed through either a longitudinal midline or transverse intra-abdominal incision and even may be performed via a retroperitoneal exposure to the aorta. More dissection is needed with TEA. Total circumferential mobilization of the infrarenal aorta and common iliac arteries is required in order to perform aortoiliac TEA. The proximal extent of the dissection is the level of the renal arteries as long as the occlusive plaques do not extend proximally and impinge on the orifices of these vessels. If occlusive disease extends cephalad to the renal arteries, the dissection must be carried proximally to the origin of the superior mesenteric artery (SMA) to allow placement of the aortic occluding clamp at the base of this vessel.

An alternative approach for suprarenal control of the aorta is placement of the aortic cross clamp above the level of the celiac axis, a maneuver that is not difficult and is quite familiar to vascular surgeons. The lumbar, middle sacral, and inferior mesenteric (IMA) arteries must be managed using vessel loops to control back bleeding when the aorta is opened. Take care to identify and preserve any accessory renal arterial branches that may be present in as many as 20% of patients. In addition, the proximal portion of the external iliac and hypogastric arteries should be dissected adequately to allow placement of occluding clamps on these vessels distal enough from the origin to view the proximal portion of the external iliac artery

The difficult portion of the dissection occurs around the distal aorta and proximal common iliac arteries. The inferior vena cava and common iliac veins may be quite adherent to the arteries at this point, and care must be taken to avoid injury to these veins. After the dissection is completed, 5000 units of intravenous heparin are administered prior to arterial occlusion.

The distal clamps are placed first to reduce the incidence of atheroembolism that may occur following application of the aortic clamp. The aorta is incised longitudinally extending from 2 cm distal to the aortic occluding clamp proximally to 2 cm proximal to the aortic bifurcation distally. Place the line of incision on the right side of the anterior surface of the aorta to avoid the origin of the IMA. The endarterectomy plane easily is established where the atheromatous disease is most severe. Grasp the plaque and gently push away the remaining arterial wall. The dissection is continued distally until the bifurcation is reached, and the appropriate plane is continued into the orifice of each common iliac artery.

The iliac artery may be incised longitudinally (if the length of the common iliac is long), or even transversely, directly over the common iliac bifurcation. The author prefers a longitudinal incision extending from the proximal common iliac artery 2 cm from the origin to the iliac bifurcation because it affords the surgeon a better view of the endarterectomized surface and the endarterectomy endpoint. A bridge of arterial wall is preserved between the abdominal aortic incision and the common iliac incisions.

Once the entire plaque is mobilized in the common iliac, the entire specimen may be pulled in a cephalad direction and removed entirely as a single specimen resembling a pair of pants. Take care to examine the distal endpoint in the iliac artery. A tongue of atheroma may continue into the origin of the external iliac and hypogastric arteries. This tail of atheroma must be excised in a more superficial plane to avoid extending the endarterectomy into the deeper plane used to perform TEA. The plane of the atheroma actually is easy to discern because the atheroma usually is a darker yellow color and has a different consistency than the more normal adherent intima.

After any remaining plaque and/or strands of media are removed, the arteriotomies are closed with continuous polypropylene sutures. If the aorta is small (< 2 cm), a prosthetic, zero-porosity Dacron patch is used to avoid narrowing that may occur during primary closure of a longitudinal arteriotomy. Once blood flow has been restored, femoral pulses should be palpated to confirm the presence of adequate inflow.

A similar aortic exposure is used to perform AFB. In addition, the common femoral, proximal superficial femoral, and proximal profunda femoris arteries are mobilized through longitudinal groin incisions that are made just lateral to the femoral pulse. If the pulse is not present, the proper line of incision is found by measuring 3-4 finger breadths lateral to the pubic tubercle.

Cover the skin in a povidone-iodine–impregnated plastic drape to help avoid skin contact with the prosthetic graft. The infrarenal aorta immediately adjacent to the renal arteries is mobilized. Circumferential mobilization of the aorta is not necessary. The common femoral artery and its branches are mobilized from the inguinal ligament to the bifurcation, exposing enough superficial femoral and profunda femoris arteries to allow placement of an arterial occluding clamp.

The aortic anastomosis may be performed in either an end-to-end or an end-to-side configuration using continuous polypropylene suture. Although partial occluding aortic clamps have been used when performing end-to-side anastomoses, a better view of the aortic lumen is obtained with the use of proximal and distal clamps that totally occlude the aorta.

If the aorta is filled with atherosclerotic debris that appears loose and may embolize when flow is restored, perform an end-to-end aortic anastomosis and oversew the distal aorta. The configuration of the proximal anastomosis is not as important as its location. The anastomosis to the aorta must be placed near the renal arteries to help avoid recurrent atheromatous and/or aneurysmal disease that may involve infrarenal aorta that remains proximal to the aortic anastomosis.

Once the proximal anastomosis is completed and no bleeding is present, the limbs of the prosthetic graft are passed carefully through retroperitoneal tunnels that were made before the patient received intravenous heparin. The tunnels are made directly anterior to the iliac arteries and posterior to the ureters. The circumflex iliac veins must be avoided during creation of the tunnel and passage of the graft limbs. Partial incision of the inguinal ligament may aid in constructing the tunnel and identifying these large troublesome veins.

The common femoral artery is incised longitudinally, and a conventional end-to-side femoral anastomosis is performed using continuous polypropylene suture. Take care to examine the origins of the 2 outflow branches (SFA and profunda) of the common femoral artery. Not uncommonly, the SFA has significant occlusive disease. If the SFA is occluded, any stenosis in the proximal portion of the profunda must be repaired to insure adequate long-term patency of the aortic graft limb. If the common femoral artery is severely diseased, limited local TEA may need to be performed to facilitate an adequate femoral anastomosis.

In the past, all patients were monitored in an intensive care environment for the first 24-48 hours following an aortic operation. In the last decade, it has become increasingly common for patients undergoing operations for occlusive disease to avoid the ICU and have their postoperative care on a regular surgical floor.

For patients with hemodynamic concerns, systemic arterial as well as pulmonary capillary wedge (PCWP) pressures help to plan intravenous fluid requirements. In addition, hourly urinary output through a bladder catheter is recorded. Although significant blood loss is not common, the hematocrit is monitored every 6-12 hours during the first 24 hours.

If the operation has proceeded smoothly, perform extubation at the end of the procedure. Preoperative pulmonary function tests help to predict which patients are likely to develop postoperative respiratory problems. When the forced expiratory volume in 1 second (FEV₁) is less than 1000 cc, one can anticipate difficult respiratory problems associated with conventional aortic surgical approaches through midline incisions. For such cases, a transverse intra-abdominal or retroperitoneal incision may help to reduce postoperative respiratory complications.

Most large fluid shifts occur following aortic surgery and are related to the size of the dissection and the length of the operation as well as the amount of intraoperative blood loss. Patients tend to gain significant "wet weight" during the first 48 hours postoperatively. By the beginning of the third postoperative day, mobilization of the excess water back into the intravascular compartment begins to occur. Urine output increases, PCWP rises, and hematocrit may drift downward.

Also monitor the perfusion to the lower extremities carefully. If pedal pulses cannot be palpated due to SFA occlusive disease, monitor Doppler flow as well as ABI. After successful revascularization, ABI should increase by at least 15%.

In general, results of the treatment for aortoiliac occlusive disease (AIOD) are excellent, but patients still need follow-up care at regular intervals. See patients every 3-6 months for the first year and every 6-12 months thereafter. If a prosthetic graft has been implanted, a lifelong risk of graft infection exists that the patient must recognize. Moreover, oral antibiotic prophylaxis is appropriate before dental procedures, urologic instrumentation, sigmoidoscopy, or other gastrointestinal surgical procedures.

Several complications are related both to aortoiliac TEA and AFB, and others are associated only with one or the other. Perioperative thrombosis may be a complication of either procedure and generally is related to technical problems. For example, a plaque that dissects, causing restriction in blood flow and subsequent thrombosis, may occur as a complication of either procedure. Visualization of endarterectomy endpoints and suturing of plaques that may elevate when blood flow is restored may help to reduce the risk of dissection and subsequent thrombosis.

Intraoperative atheroembolism is another complication that may occur during surgical dissection and mobilization of the vessels or following release of the occluding clamps during reperfusion. Meticulous dissection during mobilization of the arteries is imperative. Furthermore, placement of the distal occluding clamps before application of the proximal clamps may help to reduce the risk of atheroembolism that is inherent during any aortic operation.

Injury to adjacent structures (ie, duodenum, inferior vena cava, iliac veins, ureters) usually is easy to avoid with careful technique. However, care must be used with mechanical retractors to avoid inadvertent injury to adjacent structures. Care is necessary both in the retroperitoneum and in the groin to avoid injury to nerves adjacent to major vessels.

Careful closure of groin wounds is necessary in order to avoid a lymphocele, which can lead to graft infection.

A specific complication related to the use of prosthetic material for AFB is development of aortic graft infection, which occurs in 0.5-3% of cases. Usually, presentation of the infection follows the aortic procedure by a significant length of time (20-24 mo). Most commonly, a complication of healing in the groin wound is the first sign that a serious, life-threatening and limb-threatening problem must be dealt with.

Graft infections can be classified into 2 groups, depending on the etiologic microbial involved. The more virulent organisms (ie, Staphylococcus aureus, gram-negative bacilli) usually are responsible for causing a more severe type of clinical infection. When systemic signs of sepsis occur with graft infection, a virulent organism is present.

On the other hand, a significant number of graft infections are caused by Staphylococcus epidermidis. These infections are much more indolent, and the extent of graft involvement may be harder to determine. Even with the most skilled physician, the mortality rate following treatment of aortic graft infection is 11-27%. Moreover, the risk of amputation following graft infection is almost as high.

Major complications rates associated with catheter-based treatments (percutaneous transluminal angioplasty/stents) for aortoiliac occlusive disease range from 2.3-17%. The problem can occur in the target vessel, the access site, or even other arteries that are far removed anatomically (ie, atheroembolism). These complications include dissection, acute thrombosis, atheroembolism, and even arterial perforation. Complications related to the contrast agent (ie, anaphylaxis [rarely] or contrast-induced renal dysfunction) are uncommon.

Outcomes following aortic operations for aortoiliac occlusive disease (AIOD) are measured in terms of operative mortality rates and patency of the arterial reconstruction over time. These outcomes are similar for both aortoiliac TEA or AFB. The operative mortality rate (30-d) is 2-3%. Long-term patency is excellent too. The patency rate at 5 years following AFB or TEA is 85-90%. If patients continue to smoke, however, these excellent patency rates are reduced by half.

Outcomes for extra-anatomic (axillofemoral/femoral-femoral) bypasses are clearly not as good as either AFB or aortoiliac TEA. Operative mortality rates for extra-anatomic bypass might be expected to be better than AFB due to the extracavitary nature of these procedures and the fact that aortic occlusion is not required during the course of the operation. However, an operative mortality rate of 0-4% for femorofemoral bypass and 2-11% for axillobifemoral bypass is a reflection of the selected patients in whom these procedures are performed. Five-year primary patency of extra-anatomic bypasses performed for AIOD ranges from 19-50% for axillobifemoral bypass and 44-85% for femoral-femoral bypass.

Endovascular techniques (ie, percutaneous transluminal angioplasty, stent placement) offer alternatives to conventional surgical repair.^[10] Therefore, understanding the outcomes offered with such interventions is important. Although isolated stenosis of the infrarenal aorta or common iliac artery is uncommon, this lesion is suited ideally to percutaneous transluminal angioplasty (PTA) and/or stent placement. With localized, segmental occlusive disease in the aorta, initial technical success can be achieved in 95% of cases, with 5-year patency rates of 80-87% using PTA. Initial success rates using PTA for iliac lesions are 93-97%, with 5-year patency rates of 54-85%. These results seem to be improved when arterial stents are used either primarily or as an adjunct to PTA for the treatment of iliac artery stenosis.

One study investigating the effects of heavy calcification in stent-implanted iliac arteries showed that iliac stents in heavily calcified lesions presented significant residual stenosis; however, even in cases with incomplete expansion of the stent, further blockage was not found and all stents remained anatomically patent.^[11]

No controversy exists regarding the appropriate surgical procedure to treat aortoiliac occlusive disease (AIOD). Use TEA only in cases of type I atherosclerosis. TEA also is an excellent option for those patients with blue toe syndrome from severe ulcerogenic aortoiliac atherosclerosis that involves only the infrarenal aorta and common iliac arteries.

Some authors have advocated performing the aortic procedure through a retroperitoneal rather than an intra-abdominal approach. Unfortunately, despite some excellent work in this area, outcomes are similar whether the procedure is performed in a retroperitoneal or transabdominal fashion.

A more controversial area is whether proximal occlusive disease should be treated nonoperatively, using angioplasty and stent placement rather than the more invasive aortic operation. It seems clear that angioplasty and/or stent placement is a suitable alternative for patients with very focal occlusive disease in the common iliac artery but offers a poor alternative for more diffuse disease that involves the external iliac artery. Furthermore, the patency results for patients who have had total occlusions in the iliac arteries treated by endovascular therapy are definitely inferior to conventional surgical results.

The current controversy involves the appropriate place for minimally invasive treatment of aortoiliac occlusive disease (AIOD). Laparoscopically assisted AFBs have been performed both in animals and humans with satisfactory results. However, a significant learning curve seems to be involved, and no long-term follow-up data are available for review.