Fig. 3.5  Intra-operative completion angiogram showing a type II endoleak (arrow)

CTA at 3 years showed regression of aneurysm size, despite the presence of a small type II endoleak. No migration or device-related complications were documented. At the appointment, the patient’s blood tests revealed deteriorating renal function (Fig. 3.7).

Question 13

Regarding prolonged follow-up in patients with renal insufficiency

A.  Non-contrasted CT scans may provide enough information as long as aneurysm size is not increasing

B.  Gadolinium-enhanced magnetic resonance angiography (MRA) is the best alternative to CTA and is safe in patients with renal insufficiency

C.  DUS is a good alternative for surveillance in expert hands

D.  Pain abdominal radiograms provide no additional information when associated with other surveillance methods and should be avoided

Question 14

According to available data, what is the estimated probability of annual secondary intervention for this patient?

A.  <1%

B.  2–4%

C.  5–10%

D.  10–20%

E.  >20%

3.1  Commentary

AAAs are typically a disease of elderly white males. In men, occurrence starts in the fifth decade of life, reaching a peak incidence of about 350/100,000 person-years by the age of 80. The prevalence of AAAs measuring at least 3 cm in diameter in men over 65 years old is 7.6%. In women, AAAs tend to occur a few years later in life. The age-adjusted incidence is four to six times greater in men than in women. The risk factors with the largest impact on AAA prevalence are smoking (fivefold), male gender (5.6-fold) and age (1.7- fold each 7 years).1–3 The course of the disease is usually silent until rupture occurs. This major complication is associated with an overall mortality over 80% and ranks as the 15th cause of death in the United States of America. The aim of elective treatment is essentially to prevent death from rupture.

Although ultrasonography is the method of choice for population screening or followup measurements in patients with known aneurysms, ultrasound imaging alone gives insufficient information for preoperative assessment. For open repair, most surgeons recommend preoperative imaging with CTA, which provides accurate information regarding aneurysm size, morphology and relationship with branch vessels, as well as any anatomical variations. Detailed imaging is particularly important when an endovascular treatment is considered. 64-detector (or higher) technology offers great special resolution and submilimetric slices and allows for quick and accurate post-processing.4,5 Visualization of the entire iliac and common femoral arteries is useful for access planning anticipating difficulties related to stenosis, calcification or tortuosity. Furthermore, optimal projection angles of the C-arm maybe obtained using virtual angiography,thus improvingdeployment accuracy, reducing operative time and minimizing radiation exposure and contrast administration. CTA and post-processing with dedicated software have made conventional calibrated angiography measurements redundant in nearly all cases. [Q1: B]

Deciding whether and how to treat a AAA remains a difficult process in which the following variables play a role: risk of rupture, operative risk, anatomical suitability, patient fitness,lifeexpectancyandpatientpreference(informedconsent).Ruptureriskwillalways be an estimate, because of significant interpersonal variability and because no large

numbers of patients were ever followed-up without intervention. Using available data from the UK Small Aneurysm Trial and the Veterans Administration Aneurysm Detection and Management (ADAM) Trial, the annual risk of rupture is less than 1% when the maximum diameter is 40–55 mm, although this estimation may be tampered by the fact that many patients received surgery before they reached 55 mm for reasons other than rupture.6,7 With increasing diameters, the annual rupture rates have been estimated to be the as follows: 50–60 mm, 5–10%; 60–70 mm, 10–20%; 70–80 mm, 20–40%; greater than 80 mm, around 50%.8 [Q2: C]

The 30-day operative mortality in these two trials ranged from 2.7% to 5.8%, leading to the current concept that aneurysms can be safely observed until they reach 55 mm in diameter. The generally lower operative mortality for EVAR has challenged this view, and two trials are currently under way to compare EVAR and surveillance for small aneurysms. Women have been found to have a higher probability of rupture at any given diameter, and a lower threshold of 45 mm for surgery in this group has been proposed.11 This may be offset partially by the fact that women also have a 1.5-fold higher mortality and mobility both for open repair and for EVAR. Faster growth rate has also been associated with a higher likelihood of rupture. Most authors defend treatment of rapidly expanding AAAs (over 5 mm in 6 months or 7 mm in a year) regardless of maximum diameter. [Q3: A, B, D]

The benefit gained from EVAR is believed to be greater for higher-risk patients, but those with low-risk should not be denied an endovascular repair. Importantly, patient preference should weigh considerably in candidates for both options, as current evidence demonstrates non-superiority of one over the other. EVAR has demonstrated to result in an important threefold reduction in 30-day mortality, compared to open repair, in patients fit for both procedures. Hospital stays were shorter, recovery was easier and postoperative quality of life was better. At 4 years, though, the early survival advantage of the EVAR groups was lost, mainly due to a higher rate of coronary events. EVAR also required more re-interventions, closer follow-up involving nephrotoxic contrast and radiation exposure and was more expensive.14,15 However, recent years have witnessed a steady increase in early and late success rates, with decreasing rates of re-interventions, device-related complications and late rupture, for which technological advances and accumulated knowledge are probably responsible.16,17 While important in demonstrating the efficacy and safety of endovascular repair, the first randomized trials comparing EVAR to open repair are probably already outdated. The presence of renal failure is not an absolute contra-indication for EVAR, as various measures may be used to protect the kidneys and minimize damage, such as intravenous hydration, antioxidant medications or temporary dialysis. The contrast use in straightforward EVAR procedures is 40–100 mL, which is less than the quantity used in most CTA protocols. [Q4: D, E]

Not all aneurysms are suitable for EVAR due to anatomical restrains. Generally, endografts require areas of reasonably healthy vessel wall proximally and distally to be able to seal off blood flow. The most important feature for suitability is the size and morphology of the proximal neck (area between the lowermost renal artery and the beginning of the aneurysm). It should consist of relatively normal aorta over a minimum length of 10 mm, and the diameter should not exceed 32 mm. Neck angulation is another important limitation – infra-renal angulation over 60°–75° or iliac angulation over 90° may result in

treatment failure or late complications. Efforts have been undertaken to overcome short or unfavorable sealing zones. Recent devices, more flexible and compliant, have shown to be efficient in aneurysms with severe angulation, though mid and long-term results are still unavailable. Most modern devices offer introducer diameters of 18–22F (main body) and 12–16F(contra-laterallimbandextensions),correspondingroughlyto7and5mm,respec- tively. Hydrophilic coating of sheaths further improves “pushability” and minimizes injury to access vessels. [Q5: B, C, D]

Graft selection should be individualized, as different brand devices show specific advantages over others. Proximal fixation is achieved through radial force, in addition to hooks barbs or anchors in most available devices. An open supra-renal stent with hooks seems to be associated with less downward migration and is advantageous in more complex neck morphology. To date, supra-renal fixation has not been related to embolic or thrombotic complications of the renal arteries. A potential disadvantage supra-renal stents is the added complexity in the unlikely need of a conversion to open repair. Distal fixation usually relies solely on radial force. Bifurcated grafts are preferred, but aorto-uni-iliac (AUI) devices may be used when one of the iliac axis is compromised or the aortic lumen isverynarrow.Somepreferthesedevicesforrupturecases.Thereasonsforthisarealleged reduced time until aneurysm exclusion and the need for a smaller off-the-shelf stock. The major disadvantage of AUI devices is the necessary addition of a femoro-femoral crossover, with concerns over patency, altered hemodynamics and graft infection. [Q6: C, D]

Proximal and distal stent-graft diameters should be oversized in 15–20% of the original vessel diameter. Failure to do so will most likely result in failure to achieve adequate proximal or distal seal, thus allowing for continued pressurization of the aneurysm sac (Type I endoleak). Morethan 20% oversizing may,in turn, causeinfolding of thegraft fabric,prone to failure in achieving seal. Oversizing has been blamed for continued aortic neck enlargement, which in turn may lead to late treatment failure. While stent radial force at the aneurysm neck seems implicated in neck enlargement, this happens predominantly during the first 6 months and does not usually exceed the diameter of the prothesis.18,19 [Q7: C]

Injuxta-renalorsupra-renalaneurysmsthreeendovascularoptionsremain.Debranching provides extra-anatomical retrograde revascularization of visceral vessels (with inflow from either the infra-renal aorta or more commonly the iliac arteries) and subsequent coverage of the visceral segment (a so called hybrid procedure). It’s a valid alternative with satisfactory mid-term results, but the procedure itself is complex and not without significant operative risk.20,21 The other two options are fenestrated and branched grafts, offering an all-endovascular solution. Fenestrated grafts have “holes” for the visceral ostia, while branched grafts include ramifications that are intra-operatively extended into visceral branches with covered stents. These grafts are custom-made to match the anatomy of the patient. Time required for manufacturing (around 3 months), high cost and complexity of the procedure have tampered its widespread use, which is limited today to high-risk patients with challenging anatomies. In particular, renal complications seem to be more frequent than observed in the standard devices. In contrast, type I and III endoleak occurrence and aneurysm-related mortality show no significant difference. Despite concerns over the long-term durability of the branch revascularizations, promising short and midterm results and on-going efforts to reduce cost and availability will likely broaden the use of these devices in the future.22,23 [Q8: B] [Q9: C, D]

Iliac aneurismal involvement is a frequent finding in the diagnostic workup of AAA. Absence of a distal landing zone in the common iliac artery may be overcome by overstentingtheinternaliliacartery(occludingit)orbymeansofabifurcatediliacbranch,with vessel preservation. The first option often requires occlusion of the internal iliac artery by means of coil embolization or using an endovascular plug. This may be avoided if the internal iliac artery is already occluded, stenosed or small and the landing zone in the external iliac artery is long. Internal iliac aneurysms are best treated distal occlusion with coils and overstenting. Infrequently, unilateral occlusion of the internal iliac artery may result in buttock claudication and/or sexual dysfunction, especially if the contra-lateral vessel is occluded and pelvic collateralization is poor. Branched iliac grafts may be used in these selected cases, although they are costly, technically demanding and increase contrast load and radiation exposure. The presence of concomitant iliac aneurysms has been related with a higher risk of distal type I endoleaks.24 [Q10: B, C]

Endoleaks represent the presence of blood flow outside the endograft but within the aneurysm sac after endovascular treatment. They are classified according to their origin (Table3.1).Aboutonethirdofpatientswillpresentwithanendoleakduringfollow-up,but itssignificanceisrelatedtotypeandtochangesinaneurysmmorphology.TypeIendoleaks are rare and should be repaired in most instances, as they indicate on-going risk of rupture. This may be achieved by further balloon expansion, placement of a proximal or distal extension or ultimately by conversion. Type II endoleaks are very frequent and their documentation is increasing as image methods become more accurate. Early type II endoleaks tend to disappear spontaneously and additional measures need not be applied when they are present intra-operatively. The true significance of persistent type II endoleaks is still a matter of debate. The pressure transmitted to the aneurysm sac is known to be low and reported ruptures related to these are extremely rare. Unless significant aneurysm growth occurs, most authors defend a conservative approach and closer surveillance. Type III endoleaks are rare and require treatment for the same reason as Type I, usually with additional stent-grafts. Type IV endoleaks were frequent with early devices, but have nearly disappeared with newer generation systems. Endotension may represent undetected endoleaks or fluid accumulation. Although treatment is seldom required, expansion of the

Table 3.1  Endoleak classification

sac may warrant intervention. Anecdotal reports of percutaneous or laparoscopic aneurysm fenestration have been successful. [Q11: A] [Q12: A]

EVAR follow-up remains essential for evaluation of long-term aneurysm exclusion and timely detection of complications (Table 3.2). General recommendations include a physical examination and CTA scan within 1 month, then 12 months after operation, and then annually. Gadolinium-enhanced MRA is not an alternative in patients with renal insufficiency, as it may provoke nephrogenic systemic fibrosis, a highly incapacitating and potentially deadly complication. Moreover, prosthetic materials create significant artifacts, especially in endografts using stainless steel stents. Advances in MRA protocols may partially overcome the need for contrast enhancement and diminish artifacts. With strict protocols, CT without contrast may prove to be a valuable alternative for CTA when renal insufficiency is present. Color-flow DUS is emerging as an alternative to CTA for follow-up. Recent evidence shows that it may be comparable to CTA for detection of endoleaks.25–27 Addition of a four-plane abdominal radiogram to surveillance protocols will allow detection of stent-related complications that would otherwise be missed with DUS. [Q13: A, C]

The prognosis of patients with AAA is highly related to the underlying atherosclerotic disease. Cardiovascular complications are responsible for more than two thirds of late deaths after AAA repair. The annual aneurysm rupture risk after EVAR was around 1% with earlier devices, but this figure is estimated to be much lower today and will likely continue to decrease as newer generation grafts become predominant. Also decreasing is the rate of secondary intervention, shown to be around 20% at 4-years in earlier trials.14–17 Trial and registry data suggests that annual secondary intervention rate today is around 3%.28,29 Secondary intervention for aneurysm-related complications after open repair was

Table 3.2  EVAR follow-up imaging options