Aorta and Peripheral Vascular Disease 20

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20

Aorta and Peripheral Vascular Disease

Max P. Rosen

I. Aorta: what are the appropriate imaging studies for suspected acute aortic dissection or traumatic rupture?

II. Aorta: what is the impact and cost-effectiveness of screening for abdominal aortic aneurysms on mortality from abdominal aortic aneurysms rupture?

III. Aorta: endovascular vs. surgical treatment of abdominal aortic aneurysms: which is the best choice?

IV. Peripheral vascular disease: what are the appropriate noninvasive imaging studies for patients with suspected peripheral vascular disease?

A. Magnetic resonance angiography B. Computed tomography angiography

V. Special case: evaluation of abdominal aortic aneurysms graft endoleak

VI. Special case: evaluation of the renal donor VII. Special case: evaluation of renal artery stenosis

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䊏 Due to the need for rapid diagnosis of patients with suspected acute aortic rupture or dissection, computed tomographic angiography (CTA) is preferable to magnetic resonance angiography (MRA) (limited evidence).

䊏 Screening with ultrasound for abdominal aortic aneurysm (AAA) among men between the ages of 60 and 74 has been shown to be cost- effective with a mean cost-effectiveness ratio of £28,400 per life year gained (strong evidence).

䊏 Endovascular repair of AAA has been shown to signiﬁcantly reduce 30-day mortality from repair of AAA rupture. However, the proce- dural cost of endovascular repair is greater than that for open surgical repair (strong evidence).

䊏 Computed tomographic angiography is preferred to catheter angiography for detection of aortic stent-graft endoleak (moderate evidence).

Issues

Key Points

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Deﬁnition, Pathophysiology, and Epidemiology

Imaging of the aorta and peripheral vascular disease poses a unique set of challenges and benefits in medical imaging. For almost all clinical settings, the gold standard is catheter-based angiography. While advances in catheter design and imaging equipment over the past decade have greatly enhanced the field of diagnostic angiography, the basic tenets of the field have changed little in the past 20 years. Thus, there is an extensive body of literature based on catheter-based imaging. With the advent of multidetector CT scans and concurrent advances in MRA, CTA and MRA have become viable alternatives to catheter-based diagnostic angiography.

However, unlike any other diagnostic modality, a catheter-based diagnostic study may rapidly be converted to an interventional procedure. Thus, any new modality for imaging the aorta or peripheral vascular disease must be compared to the gold standard of angiography, both for its diagnostic accuracy and for its cost-effectiveness in the context of immediately converting a catheter-based diagnostic study to a therapeutic intervention.

Aortic rupture is usually cased by blunt or penetrating trauma. Aortic dissection can be precipitated by traumatic or nontraumatic causes such as hypertension and aortitis; the latter may be infectious or inﬂammatory in nature. Aortic aneurysms are caused by a weakening in the aortic wall resulting in either saccular or fusiform dilatation.

While most AAAs are the result of atherosclerosis, they may also have traumatic, infectious, and inﬂammatory etiologies. In men over the age of 65, ruptured AAAs are responsible for 2.1% of all deaths in England and Wales (1). Approximately 50% of these deaths occur before the patient reaches the hospital. Operative mortality for the 50% of patients with ruptured AAAs who reach the hospital alive is between 30% and 70%.

Peripheral vascular disease is most often caused by hypertension, dia- betes, hypercholesterolemia, or cigarette smoking and can be classiﬁed as either acute or chronic. Acute limb ischemia (ALI) is deﬁned as a sudden decrease in limb perfusion that may result in threatened viability of the extremity. Chronic manifestations of peripheral arterial disease (PAD) are divided clinically into (1) intermittent claudication and (2) chronic critical limb ischemia.

Overall Cost to Society

Data on the societal cost of imaging for these indications is not available, except for the cost-effectiveness of screening for AAA with ultrasound among men 65 to 74 years of age (see I, below).

䊏 Computed tomographic angiography is comparable to MRA for evaluation of peripheral vascular disease and for the preoperative evaluation of renal artery stenosis (moderate evidence).

䊏 The most cost-effective imaging strategy for the evaluation of the living renal donor varies and is dependent on the perspective of the analysis (renal donor or recipient), as well as the speciﬁcity of digital subtraction angiography (DSA) (moderate evidence).

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Goals

The goals and method of imaging of the aorta and peripheral vascular branches depend on the clinical setting. In the case of suspected traumatic injury or aortic dissection, the goal of imaging is twofold. The most immediate goal is to identify as quickly as possible the patients in need of immediate surgical repair. The secondary goal in this acute setting is to help the surgeon identify the extent of vascular injury and plan the appropriate repair.

The goal of screening asymptomatic patients for AAA is to identify patients with AAA and provide immediate intervention if the size of the AAA at the time of screening warrants repair. For those patients with AAA, the size of which does not warrant immediate repair, the goal of screening is to identify any change in the size of the AAA over time, and to initiate therapy when the rate of expansion of the AAA reaches a threshold that justiﬁes repair.

When vascular insufﬁciency or ischemia is suspected, the goal of imaging is to identify the level and extent of the stenosis or occlusion. The optimal imaging strategy is somewhat dependent on the most likely method for intervention. If a catheter-based intervention is likely, then a catheter-based imaging study is often warranted as the initial imaging study. On the other hand, if a surgical intervention is likely, then a less invasive initial imaging study such as CTA or MRA may be optimal.

Methodology

PubMed searches for the following index terms were performed from January 2000 to August 2004: computed tomography (CT) angiography, mag- netic resonance (MR), vascular studies, arteries, stenosis or occlusion, angiogra- phy, comparative studies, aneurysms, aortic, cost-effectiveness, and abdominal aortic aneurysms. Relevant articles in English were obtained and read for appropriateness. The search was limited to articles published in January 2000 or later to ensure that only studies employing current noninvasive technologies would be included. Selected articles published before 2000 and after August 2004 (2) were also included at the time of manuscript review by the book’s editors.

I. Aorta: What Are the Appropriate Imaging Studies for Suspected Acute Aortic Dissection or Traumatic Rupture?

Summary of Evidence: Due to the need for rapid diagnosis of patients with suspected acute aortic rupture or dissection (Fig. 20.1), CTA is preferable to MRA. Most modern emergency departments are equipped with helical CT scanners, and unlike MRA, CTA of the entire aorta can be performed in a less than 60 seconds.

Supporting Evidence: Yoshida et al. (3) assessed the sensitivity, speciﬁcity, and accuracy of CTA among 57 patients with surgically proven type A dissection who underwent helical CT, and reported 100% sensitivity of helical

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CT to detect aortic dissection in the thoracic aorta. Sensitivity for detection of arch branch vessel involvement was 95% and 83% for detection of pericardial effusion. (The authors explain that the lower sensitivity for detection of pericardial effusion may be due to the delay between CTA and surgery, with the pericardial effusion developing during the delay.) Due to the lack of reported follow-up of the 64 patients in whom the CTA did not show dissection, this study represents limited (level III) evidence. Several other studies support the use of CTA to exclude aortic injury (4,5) but are based on older single detector technology. Although not commonly available in emergency situations, Pereles et al. (6) reported excellent 100% sensitivity for diagnosis of thoracic aortic dissection using true fast imaging with steady-state precision (FISP).

Cost-Effectiveness Analysis: An older paper by Hunink and Bos (7) pub- lished in 1995 evaluated the cost-effectiveness of CT compared with plain ﬁlm chest radiography and immediate angiography in deciding when angiography should be performed in hemodynamically stable patients with suspected aortic injury after blunt chest trauma. This study was performed before the widespread use of multidetector CT, and investigated the use of CT as a triage tool rather than as a deﬁnitive diagnostic study.

The authors conclude that selecting patients for triage to angiography based on the CT ﬁndings yielded higher effectiveness at a lower cost- effectiveness ratio than doing so based on chest radiographs, and that the incremental cost-effectiveness ratio was $242,000 per life saved for the strategy of CT followed by angiography for positive cases.

Figure 20.1. Coronal (A) and sagittal (B) computed tomographic angiography (CTA) demonstrating type B aortic dissection. Both renal arteries are supplied from the true lumen (arrows).

A B

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II. Aorta: What Is the Impact and Cost-Effectiveness of Screening for Abdominal Aortic Aneurysms on Mortality from Abdominal Aortic Aneurysms Rupture?

Summary of Evidence: The Multicenter Aneurysm Screening Study (MASS) (1) investigated the impact of ultrasound screening for AAA in a popula- tion of 67,800 men between the ages of 65 and 74 years. The study was a randomized controlled study conducted at four centers in the United Kingdom and provides strong evidence that screening for AAA with ultrasound signiﬁcantly reduced AAA related deaths.

Supporting Evidence: The MASS group (1) investigated the effect of AAA screening on mortality in men using a randomized controlled trial design of 67,800 men aged 65 to 74 years. Men in whom AAA (>3cm in diameter) were detected were followed with repeat ultrasound for a mean of 4.1 years. Surgery was considered if the diameter of the AAA was >5.5cm or if the AAA expanded >1cm per year, or if symptoms related to the AAA developed. Health-related quality of life was measured using the stan- dardized medical Outcomes Study short-form 36-item survey (SF-36) (8) and the EuroQol EQ-5D (9). The primary outcome measure was mortality related to AAA.

There were 65 (0.19%) AAA-related deaths in the screened group, and 113 (0.33%) in the control group (p= .0002) with a 53% risk reduction [(95%

conﬁdence interval (CI) 30–64%] among those who underwent screening.

Thirty-day mortality following elective surgery was 6% vs. 37% following emergency surgery.

Cost-Effectiveness Analysis: Data from the MASS study (1) were used to esti- mate the cost-effectiveness of AAA screening using ultrasound over a 4- year period and they provide strong evidence. Costs included in the analysis were costs associated with the initial screening program: clinic staff and study administration, ofﬁce space, equipment, and costs associated with any follow-up scans. Costs associated with surgery were calculated from the actual costs incurred by the cohort of patients who underwent surgery and any hospital admission during the 12 months after surgery. No costs related to patient death from aneurysm rupture were included if the patient had not been admitted to the hospital for attempted emergency surgery. Cost-effectiveness was measured as survival free from mortality related to AAA for each patient for up to 4 years and was expressed as incremental cost per additional life year gained.

Over 4 years, the mean estimated cost-effectiveness ratio for screening was $51,000 per life year gained, equivalent to $64,600 per quality-adjusted life year (QALY) gained.

III. Aorta: Endovascular vs. Surgical Treatment of

Abdominal Aortic Aneurysms: Which Is the Best Choice?

Summary of Evidence: Endovascular treatment of AAA is associated with a signiﬁcant reduction in 30-day mortality and hospital length of stay, compared to surgical repair. However, the cost of endovascular repair is greater than that of surgical repair, due to the cost of the endograft (strong evidence).

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Supporting Evidence: Several recent papers have addressed the clinical effectiveness of endovascular aneurysm repair (EVAR) (10) and calculated the cost-effectiveness of EVAR compared to standard therapy. The short- term (30-day) outcome of patients treated with EVAR has been reported from a prospective registry in which 611 patients were enrolled at 31 centers in the UK (10a). The aneurysm was successfully excluded in 465/611 (76%) of patients. Additional endovascular procedures were required in 71/611 (12%) and additional surgical procedures were required in 30/611 (5%). An additional 32/611 (5%) patients required conversion to open repair. Thirty-day complication rates were as follows: technical, 6%;

wound complications, 8%; renal failure, 4%; and other medical complications, 13%. Thirty-day mortality for all patients was 6.6%. For patients considered ﬁt, 30-day mortality was 4% but increased to 18% for unﬁt patients.

Complications of persistent endoleaks and 30-day mortality were signiﬁ- cantly greater for AAAs > 6cm than for AAAs ⭐ 6cm.

Zeebregts et al. (11) compared the outcome of AAA repair with EVAR (n = 93) vs. open surgical repair (n = 195) in a nonrandomized prospec- tive trial. All consecutive patients undergoing AAA repair at one institution during a 10-year period were included in the study. Detailed patient characteristics of the two groups were not provided, but the authors state,

“The study conﬁrmed that patients were mainly selected on anatomic grounds to undergo either open repair or EVAR.” Compared to open sur- gical repair, patients undergoing EVAR had signiﬁcantly (p< .05) shorter stays in the intensive care unit (ICU); shorter hospital stays; fewer bleed- ing complications, pulmonary complications, and episodes of multiple organ failure; and lesser 30-day morality.

A randomized controlled trial (EVAR 1 trial) (12), comparing EVAR with open repair, has recently been reported in which 1082 elective patients (age

>60 with AAA diameter >5.5cm) were randomized to receive either EVAR (n= 543) or open repair (n = 39) at 41 British hospitals. Thirty-day mortality by intention to treat was the outcome reported and was signiﬁcantly less in the EVAR group, 1.7% (9/531), compared to 4.7% (24/516) in the open group (odds ratio 0.35; 95% CI 0.16–0.77; p= .009).

A second, multicenter trial, the Dutch Randomized Endovascular Aneurysm Management (DREAM) trial (13) is also being conducted with 345 patients enrolled. Initial results from 153 patients at 1 year demonstrated cumulative survival of 95% in the EVAR group compared to 89%

in the operative group, p= .21). The cumulative event-free survival at 12 months was 76% in the EVAR group and 72% in the operative group. Data from all 345 patients analyzed from the point of view of 30-day mortality found that endovascular repair was associated with a lower 30-day mortality, 1.2% (95% CI, 0.1–4.2%), compared to 4.6% (95% CI 2.0–8.9%) for open repair, resulting in a risk ratio of 3.9 (95% CI, 0.9–32.9] (14). The DREAM trial has also reported quality of life (QoL) using the SF-36 and EuroQoL(-)5D questionnaires at regular intervals during the ﬁrst year (15).

From 6 months onward the operative group reported a signiﬁcantly higher score on the EuroQol EQ-5D than the EVAR group (p= .045).

The cost of EVAR has been compared to open repair using data from a retrospective analysis of 131 patients undergoing AAA repair and 49 patients undergoing open repair as part of a U.S. Food and Drug Admin- istration phase II prospective multicenter study (16). Total inpatient hos-

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pital costs of EVAR were signiﬁcantly higher than that of open repair ($19,985± $7396 vs. $12,546 ± $5944, p = .0001). The cost of the Endograft ($10,400) accounted for 52% of the total cost of EVAR.

Cost-Effectiveness Analysis: While the expected robust cost-effectiveness data from the EVAR 1 and EVAR 2 trials has not yet been published, moderate data calculating the cost per hospital day saved of EVAR vs. open repair from a single institution in which seven patients underwent EVAR and 31 patients underwent open repair have been reported (17). The mean total cost for EVAR ($14,967) was signiﬁcantly greater than that for open repair ($4823) (p= .004), even though the mean length of stay for the EVAR group (2.09 days) was signiﬁcantly less than the mean length of stay for the open repair group (4.45 days) (p = .009). The cost of the Endograft accounted for 57% of the total cost of EVAR. The cost of reducing the hospital stay by 1 day by performing EVAR was $1,604.

IV. Peripheral Vascular Disease: What Are the

Appropriate Noninvasive Imaging Studies for Patients with Suspected Peripheral Vascular Disease?

Magnetic resonance angiography and CT angiography are the most commonly used noninvasive imaging studies in peripheral vascular disease.

A. Magnetic Resonance Angiography

Summary of Evidence: Numerous studies compare various MRA techni- ques with catheter angiography for evaluation of patients with suspected peripheral vascular disease (PVD). However, almost all of these studies provide only limited evidence in support of MRA. Many studies are retrospective and suffer from selection bias. Further complicating the analysis is a lack of standardization in the reporting of arterial segments.

Supporting Evidence: Several studies compare the sensitivity and speciﬁcity of MRA with digital subtraction angiography (DSA). However, synthe- sizing these studies into a comprehensive summary is difﬁcult, due to heterogeneous patient populations, disparate reporting methods, and variations in MRA technique. For example, among patients with known or suspected PVD, Loewe et al. (18) reported positive and negative predictive values for overall stenosis detection of 91.2% and 97.3%, respectively.

However, when nondiagnostic segments were included, the positive and negative predictive values decreased to 89.9% and 95.9%, respectively.

Binkert et al. (19) compared the diagnostic accuracy of dedicated calf MRA vs. standard bolus-chase MRA with catheter angiography and found that dedicated calf studies were superior to standard bolus-chase MRA, 81.5%

vs. 67.8% (reader 1) and 79.1% vs. 63.4% (reader 2). Among patients with symptoms and signs of aortoiliac occlusion, MRA has been shown to yield sensitivity of 87.5% and speciﬁcity of 100% for diagnosing aortic occlusion, compared to catheter angiography (20). In a retrospective study of 45 patients with lower-limb ischemia at high risk for catheter angiography, none of 28 who subsequently underwent above-knee surgical reconstruc-

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tion required complementary catheter angiography. However, in seven of 10 patients who underwent below-knee surgical reconstruction, pre- or intraoperative catheter angiography was required (21). Khilnani et al. (22) retrospectively compared the concordance of three readers’ selection of inﬂow and outﬂow segments for preoperative treatment planning with MRA and catheter angiography and found that the mean percentage of agreement between MRA and catheter angiography ranged from 91% to 97%.

B. Computed Tomography Angiography

Summary of Evidence: There is limited evidence supporting the diagnostic accuracy of CTA for the evaluation of patients with suspected PVD. Com- pared to MRA, there is less variability in CTA protocols and techniques, which reduces some of the variability in study design. The current literature reports diagnostic performance of four-row multidetector CT (MDCT), which is currently being replaced by up to 32- to 64-row MDCT.

Supporting Evidence: An initial study of the technical feasibility of MDCT for the evaluation of lower extremity arterial inﬂow and runoff was published in 2001 (23). The study evaluated patients with symptomatic lower extremity arterial occlusive (n= 19) or aneurysmal disease (n = 5). Indica- tions for CTA among the 19 patients with suspected occlusive disease included calf or thigh claudication, nonhealing foot ulcers, or gangrene.

Eighteen of the 24 patients underwent conventional angiography within 3 months of the CTA. The authors reported the degree of arterial enhance- ment and the number of arterial segments analyzable with CTA. As the scope of this study was limited to technical issues, sensitivity and speci- ﬁcity were not reported.

A more clinically relevant paper was published in 2004 by Romano et al.

(24) in which they compared the diagnostic accuracy of four-row multidetector CTA (MDCTA) with DSA in patients with peripheral occlusive disease. Forty-two patients underwent MDCTA and DSA within 5 days.

Images were blindly interpreted by two radiologists. The overall sensitivity and speciﬁcity of MDCTA, compared to DSA, was 93% and 95%, respectively. Positive and negative predictive values were 90% and 97%, respectively. The accuracy of MDCT for each anatomic segment is provided in Table 20.1.

Normal arterial segments and 100% occluded segments were correctly identiﬁed in all cases by MDCT. Almost all cases in which the degree of arterial segment stenosis was misinterpreted were in the calf; 58% of mis-

Table 20.1. Accuracy of multidetector computed tomography (MDCT), compared to digital subtraction angiography (DSA), according to anatomic segment (24)

Diagnostic Sensitivity Speciﬁcity PPV NPV accuracy

Aortoiliac 95 99 99 97 98

Femoropopliteal 94 97 96 97 97

Infrapopliteal 85 92 74 96 89

PPV, positive predictive value; NPV, negative predictive value.

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interpreted stenotic segments were false positives and 42% were false negative. Interobserver agreement (k) for DSA and MDCT were 0.817 and 0.802, respectively, and for MDCT vs. DSA were 0.835 and 0.857 for reader 1 and reader 2, respectively.

Cost-Effectiveness Analysis: None available.

V. Special Case: Evaluation of Abdominal Aortic Aneurysms Graft Endoleak

Summary of Evidence: Immediate complications of endoluminal stent-graft placement for treatment of AAA include perigraft leaks (Fig. 20.2), occlusion of aortic branches, stent-graft collapse, incomplete stent-graft deploy- ment, and graft thrombosis. Of these complications, perigraft leak is the most common. Endoleaks are classified according to their origin: type I, incomplete attachment; type II, retrograde filling; type III, device degen- eration or junctional dehiscence; type IV, transient graft porosity; and type V, continued expansion of the aneurysm without detectable endoleak (endotension) (25). Type I, II, and III endoleaks are often amenable to treatment with a secondary endovascular procedure, whereas type V endoleaks must be corrected with surgical repair. Compared with catheter angiography, CTA has much greater sensitivity and specificity in detecting endoleaks and is the preferred method for imaging a patient with suspected endoleak. However, if an endoleak is detected during CTA, and the etiology of the endoleak is not demonstrated, in a 2004 case report of two patients (14), MR angiography identified the cause of an endoleak that was

Figure 20.2. Axial CT scan cephalad to the aortic bifurcation. High density within the posterior aspect of the aorta represents an endoleak (arrow).

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not detectable by CTA (limited evidence). The data provided from this single study provides moderate evidence in support of CTA as the modality of choice for evaluating patients with suspected endograft leak.

Supporting Evidence: Amerding et al. (26) conducted a retrospective, blinded study comparing the sensitivity and speciﬁcity of CTA and catheter angiography in detecting immediate complications of endoluminal stent-graft placement for treatment of AAA. The most common complication, perigraft leak, was observed in 20/46 (43%) of patients. All patients underwent both CTA and conventional angiography and each modality was reviewed by three independent reviewers. The reference standard interpretation was developed by consensus of a CT radiologist and the primary angiographer. Mean sensitivity and speciﬁcity for detecting perigraft leaks were 63% (range, 60–70%) and 77% (range, 58–100%) for catheter angiography and 92% (range, 80–100%) and 90% (range, 85–92%) for CTA. The mean k value for interpretation of catheter angiography was 0.41 (range, 0.27–0.63) and 0.81 (range, 0.73–0.91) for CTA.

Wicky et al. (25) reported two cases in which the cause of an endoleak was not detected on CTA, but was detected on MRA.

Cost-Effectiveness Analysis: Not available.

VI. Special Case: Evaluation of the Renal Donor

Summary of Evidence: Several studies reported the sensitivity and speci- ﬁcity of CTA and MRA in identifying anatomic variations and arterial stenosis or occlusion, which are needed prior to selecting a donor kidney from a living donor. However, these studies only provide limited evidence, as most studies lack a gold standard (i.e., surgical conﬁrmation of the anatomy of the kidney that was not chosen as the donor). The majority of these studies simply report the interobserver agreement between two preoperative imaging modalities. However, using existing data from the literature, Liem et al. (27) evaluated the cost-effectiveness of several imaging strategies for the preoperative evaluation of living renal donors.

Supporting Evidence: Halpern et al. (28) compared CTA and MRA in the preoperative evaluation of living renal donors in which 35 donors underwent preoperative assessment with both CTA and gadolinium-enhanced MRA. Both CTA and MRA studies were evaluated by two independent reviewers and the following data were recorded: number and size of renal arteries found on each side, presence of arterial stenosis or a proximal arterial branch, and the anatomy of renal veins and ureters. Forty-one patients initially enrolled in the study, but only six underwent CTA. Sur- gical correlation with the transplanted kidney was available for 18 kidneys.

Thek value for interobserver agreement for MRA was 0.74 and for CTA was 0.73, and for agreement between MRA and CTA was 0.74. Among the 18 kidneys for which surgical correlation was available, one proximal arterial branch to a left kidney was missed at both CTA and MRA, and two very small (<1mm) accessory arteries suggested at CTA were not found at nephrectomy.

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Rankin et al. (29) reported the correlation between CTA or gadolinium- enhanced MRA with findings at nephrectomy for living related kidney donors. Unlike the study of Halpern et al. (28), patients underwent either CTA or MRA. Both CTA and MRA were 100% sensitive in identifying the main renal arteries and renal veins; CTA visualized 37/40 arteries identified at surgery for a detection rate of 93%, and MRA visualized 18/20 arteries identified at surgery, for a detection rate of 90%.

Cost-Effectiveness Analysis: Liem et al. (27) reported a decision- and cost- effectiveness for the evaluation of living renal donors. Their conclusion depends on the perspective (donor vs. recipient) and on the speciﬁcity of DSA. For the donor, MRA dominated all other strategies (DSA, CTA, DSA with MRA, MRA with CTA, no testing and transplantation always performed, and no testing and no transplantation performed). For the recipient, DSA and DSA with MRA performed the same day both dominated all other strategies. For both donor and recipient (combined results) DSA dominated all other strategies. If the speciﬁcity of DSA was less than 99%

for detection of renal disease, MRA with CTA performed the same day was superior. The authors point out the limitations of their study, which include that their model was based on multiple data sources, some of which may be subject to publication bias. Imaging protocols for each of the techniques varied among transplant centers. In addition, all cost data utilized in the analysis was obtained from their own center.

VII. Special Case: Evaluation of Renal Artery Stenosis

Summary of Evidence: There is no statistical difference between three- dimensional (3D) MRA and multidetector row CTA in the detection of hemodynamically signiﬁcant renal artery stenosis identiﬁed in the current literature.

Supporting Evidence: Willmann et al. (30) reported the diagnostic perfor- mance of MRA compared with DSA in the detection of hemodynamically renal artery stenosis in 46 patients. Two independent readers participated in the study. The sensitivity for readers one and two were 86% (95% CI, 64–100%) and 100% (95% CI, 99–100%), respectively, and the speciﬁcity was 100% (95% CI, 99–100%) and 100% (95% CI, 95–100%), respectively.

Stueckle et al. (31) reported the performance of CTA compared to DSA for identiﬁcation of renal artery aneurysms, low- and high-grade renal artery stenosis, and renal artery occlusion. Data were reported for axial, 3D volume reconstruction (VR) and multiplanar imaging (MPI) CTA techniques. Compared to DSA, MPI achieved the greatest sensitivity (100%) and speciﬁcity (100%) for detection of low- and high-grade renal artery stenosis, as well as arterial occlusion.

Cost-Effectiveness Analysis: None available.

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Take-Home Table

Table 20.2. Take-home table: questions and answers

Question Answer Level of evidence

What is the appropriate CT angiography Limited

imaging study for suspected aortic injury?

Is screening for AAA with The MASS (1) study has shown a signiﬁcant Strong ultrasound cost-effective? reduction in mortality from AAA among

patents who underwent ultrasound screening.

The mean cost-effectiveness ratio for screening was £28,400 per life-year gained.

Endovascular vs. surgical Endovascular repair of AAA has been shown to Strong repair of AAA—what is be associated with a signiﬁcant reduction in

the best choice? mortality when compared with open surgical repair. However, the cost of endovascular repair is greater than that of open repair, mainly due to the cost of the stent-graft.

What is the appropriate Studies of CTA and MRA for PVD are limited to Limited noninvasive imaging study reporting the sensitivity and speciﬁcity of CTA

for suspected peripheral and MRA compared to catheter angiography.

vascular disease (PVD)?

What is the best way to CTA is preferred to catheter angiography, with Moderate evaluate the patient with MRA reserved for cases in which the cause of

suspected AAA endograft leak? the endoleak is not evident on CTA.

What is the best The most cost-effective imaging strategy varies Moderate noninvasive imaging study and is dependent on the perspective of the

for evaluation of the renal analysis (renal donor or recipient), as well as the donor? speciﬁcity of digital subtraction angiography

(DSA).

What is best noninvasive CTA and MRA are comparable. Moderate imaging study for MRA is preferred for the patients with impaired

evaluation of renal artery renal function.

stenosis?

Future Research

The following studies are needed to further deﬁne the cost-effectiveness of imaging of the aorta and peripheral vascular disease:

• Impact of CTA and MRA on treatment planning for patients with suspected peripheral vascular disease.

• Impact of CTA and MRA on outcome for patients evaluated for suspected renal artery stenosis.

• Standardization of CTA and MRA techniques to allow for more direct comparison of studies performed at different institutions.

Acknowledgment: Dr. Bertrand Janne contributed to the deﬁnition and pathophysiology of peripheral vascular disease.

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