This is the current release of the guideline.

This guideline updates a previous version: Casciani T, Bettmann MA, Gomes AS, Grollman JH, Holtzman SR, Polak JF, Sacks D, Schoepf J, Stanford W, Jaff M, Moneta GL, Expert Panel on Cardiovascular Imaging. Follow-up of lower extremity arterial bypass surgery. [online publication]. Reston (VA): American College of Radiology (ACR); 2005. 6 p. [30 references]

The appropriateness criteria are reviewed biennially and updated by the panels as needed, depending on introduction of new and highly significant scientific evidence.

Recurrent symptomatic or asymptomatic stenosis following lower extremity arterial bypass surgery

To evaluate the appropriateness of initial radiologic examinations for recurrent symptomatic and asymptomatic stenosis following lower-extremity arterial bypass surgery

Patients with recurrent symptomatic and asymptomatic stenosis following lower-extremity arterial bypass surgery

Utility of radiologic examinations in differential diagnosis

Literature Search Procedure

The Medline literature search is based on keywords provided by the topic author. The two general classes of keywords are those related to the condition (e.g., ankle pain, fever) and those that describe the diagnostic or therapeutic intervention of interest (e.g., mammography, MRI).

The search terms and parameters are manipulated to produce the most relevant, current evidence to address the American College of Radiology Appropriateness Criteria (ACR AC) topic being reviewed or developed. Combining the clinical conditions and diagnostic modalities or therapeutic procedures narrows the search to be relevant to the topic. Exploding the term "diagnostic imaging" captures relevant results for diagnostic topics.

The following criteria/limits are used in the searches.

1. Articles that have abstracts available and are concerned with humans.
2. Restrict the search to the year prior to the last topic update or in some cases the author of the topic may specify which year range to use in the search. For new topics, the year range is restricted to the last 5 years unless the topic author provides other instructions.
3. May restrict the search to Adults only or Pediatrics only.
4. Articles consisting of only summaries or case reports are often excluded from final results.

The search strategy may be revised to improve the output as needed.

The total number of source documents identified as the result of the literature search is not known.

Strength of Evidence Key

Category 1 - The conclusions of the study are valid and strongly supported by study design, analysis, and results.

Category 2 - The conclusions of the study are likely valid, but study design does not permit certainty.

Category 3 - The conclusions of the study may be valid, but the evidence supporting the conclusions is inconclusive or equivocal.

Category 4 - The conclusions of the study may not be valid because the evidence may not be reliable given the study design or analysis.

The topic author drafts or revises the narrative text summarizing the evidence found in the literature. American College of Radiology (ACR) staff draft an evidence table based on the analysis of the selected literature. These tables rate the strength of the evidence for all articles included in the narrative text.

The expert panel reviews the narrative text, evidence table, and the supporting literature for each of the topic-variant combinations and assigns an appropriateness rating for each procedure listed in the table. Each individual panel member forms his/her own opinion based on his/her interpretation of the available evidence.

More information about the evidence table development process can be found in the ACR Appropriateness Criteria® Evidence Table Development document (see the "Availability of Companion Documents" field).

Modified Delphi Technique

When the data available from existing scientific studies are insufficient, the American College of Radiology Appropriateness Criteria (ACR AC) employs systematic consensus techniques to determine appropriateness. The ACR AC panels use a modified Delphi technique to determine the rating for a specific procedure. A series of surveys are conducted to elicit each individual panelist's expert opinion of the appropriateness of an imaging or therapeutic procedure for a specific clinical scenario based on the available data. ACR staff distributes surveys to the panelists along with the evidence table and narrative. Each panelist interprets the available evidence and rates each procedure. Voting surveys are completed by panelists without consulting other panelists. The ratings are integers on a scale between 1 and 9, where 1 means the panel member feels the procedure is "least appropriate" and 9 means the panel member feels the procedure is "most appropriate." Each panel member has one vote per round to assign a rating. The surveys are collected and de-identified and the results are tabulated and redistributed after each round. A maximum of three rounds are conducted. The modified Delphi technique enables each panelist to express individual interpretations of the evidence and his or her expert opinion without excessive bias from fellow panelists in a simple, standardized, and economical process.

Consensus among the panel members must be achieved to determine the final rating for each procedure. If eighty percent (80%) of the panel members agree on a single rating or one of two consecutive ratings, the final rating is determined by the rating that is closest to the median of all the ratings. Up to three voting rounds are conducted to achieve consensus.

If consensus is not reached through the modified Delphi technique, the panel is convened by conference call. The strengths and weaknesses of each imaging examination or procedure are discussed and a final rating is proposed. If the panelists on the call agree, the rating is accepted as the panel's consensus. The document is circulated to all the panelists to make the final determination. If consensus cannot be reached, "No consensus" appears in the rating column and the reasons for this decision are added to the comment sections.

Not applicable

The guideline developers reviewed a published cost analysis.

Criteria developed by the Expert Panels are reviewed by the American College of Radiology (ACR) Committee on Appropriateness Criteria.

Note from the American College of Radiology (ACR) and the National Guideline Clearinghouse (NGC): ACR has updated its Relative Radiation Level categories and Rating Scale. The Rating Scale now includes categories (1,2,3 = Usually not appropriate; 4,5,6 = May be appropriate; 7,8,9 = Usually appropriate). See the original guideline document for details.

ACR Appropriateness Criteria®

Clinical Condition: Follow-up of Lower-Extremity Arterial Bypass Surgery

Variant 1: Infrainguinal vein graft, asymptomatic. Screening.

Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.

Variant 2: Infrainguinal graft, symptoms of ischemia and/or abnormal ABI.

Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.

Summary of Literature Review

Lower-extremity arterial bypass surgery can be broadly categorized as suprainguinal or infrainguinal and, when infrainguinal, as autologous vein or artificial graft. Postsurgical surveillance previously was limited to clinical observation of recurring symptoms, measurement of ankle-brachial indices (ABI), and segmental volume recordings. Over the past two decades, routine duplex ultrasound (US) for asymptomatic patients following infrainguinal bypass has gained acceptance. Further imaging may be warranted for anatomic mapping prior to open surgical or endovascular intervention for dysfunctional grafts identified by clinical symptoms or duplex US.

Digital subtraction angiography (DSA) remains the gold standard imaging tool for precise evaluation of the severity, location, and character of graft stenoses, as well as the quality of the native vessels proximal and distal to the graft prior to reintervention. More recently, magnetic resonance angiography (MRA) and computed tomography angiography (CTA) have become more accepted as noninvasive imaging substitutes for DSA. Even in the setting of an acutely threatened limb after bypass graft failure, these studies may be warranted prior to urgent intervention.

The natural history of lower-extremity bypass graft failure is the development of stenoses within or adjacent to the graft and ultimately thrombosis, if left uncorrected. Early failures are usually secondary to technical errors such as a retained valve or a kink in the conduit during tunneling. There is strong evidence that using intraoperative, duplex US during the creation of the graft reduces early graft failures. In fact, the most sensitive predictor of subsequent graft stenosis formation is an abnormal duplex US during initial surgery. Late failures are usually due to intimal hyperplasia within the graft or at either anastomosis, or progression of atherosclerosis in the inflow or outflow arteries. During the first postoperative year, up to 30% of venous grafts develop stenoses. There is evidence suggesting that repair of these stenoses, by either surgical or endovascular means, extends the patency of venous bypass grafts. In addition, patency following revision of a thrombosed vein graft is inferior to patency following revision of a stenotic graft prior to thrombosis.

Ultrasound

Duplex US has been used as a method of vein graft surveillance for more than 20 years. The technique involves the sequential study of a graft from the proximal to distal anastomosis, with measurement of peak systolic flow velocity (PSFV) and peak systolic flow velocity ratio (PSFVR), the ratio of PSV to the systolic velocity in the adjacent normal segment. There is evidence to suggest that PSFVR is the most sensitive indicator of a graft stenosis. A PSFVR of >2.0 to 2.5 is often considered representative of a significant stenosis, although there are reports suggesting a higher value of 3.0 to 3.5 as a more appropriate threshold for intervention. Other values that may signify a graft stenosis are a PSFV >200 cm/sec at any point in the graft or a midgraft PSFV <45 cm/sec, which may indicate high outflow resistance (suggesting progressive atherosclerosis in the runoff vessels). However, low PSFV can also be seen in normal large-caliber vein grafts.

Despite the long-term use of duplex US for routine surveillance of lower-extremity bypass grafts, there are no large, randomized controlled trials available supporting US surveillance. Trials comparing duplex US surveillance versus clinical follow-up of lower-extremity bypass grafts have come to different conclusions. One study showed no difference in assisted primary or secondary patency for 185 vein grafts at 1 year. A study of 165 grafts did show a significant benefit in assisted primary and secondary patency for vein grafts at 3 years, but no benefit in patency for the surveillance of polytetrafluoroethylene (PTFE) grafts. A large, nonrandomized study of 615 bypasses found significant improvement in secondary patency and limb salvage for grafts followed by duplex US and ABI compared to clinical surveillance alone.

A recent multicenter prospective randomized control trial of 594 patients offered strong evidence to the contrary. This study randomized patients into a clinical or duplex US follow-up group for 18 months. The primary, primary assisted, and secondary patency rates were nearly identical for both groups (69%, 76%, 80% versus 67%, 76%, 79%), but the diagnostic costs were significantly higher in the US group. The investigators concluded that routine lower-extremity bypass graft surveillance with US showed no additional health benefit but incurred greater cost.

Digital Subtracted Angiography

Prior to reintervention in a bypass graft, interventionalists and surgeons need accurate anatomic mapping of not only the graft but also the native inflow and outflow arteries. Selective DSA has remained the gold standard for this purpose, but it carries inherent risks due to the invasive nature of the procedure.

Magnetic Resonance Angiography

In recent years, MRA, specifically three-dimensional (3D) contrast-enhanced MRA, has shown increasing ability to properly evaluate inflow and outflow vessels as well as bypass grafts. Studies by two groups of researchers confirmed excellent sensitivity and specificity with MRA. Another study not only confirmed excellent image quality with MRA but also detected four additional high-grade stenoses not seen on US and confirmed with DSA.

In addition to the regular MRA contraindications, artifacts from metallic clips and stents, as well as venous contamination can limit its utility for evaluating bypass grafts. New MRA techniques using dedicated calf and foot imaging and time-resolved MRA have improved the diagnostic performance of this modality. Use of these state-of-the-art techniques will depend on the availability of local equipment and expertise.

Computed Tomography Angiography

Multidetector computed tomography (MDCT) angiography has gained tremendous momentum as a noninvasive imaging tool for evaluating peripheral atherosclerotic occlusive disease (PAOD), as well as lower-extremity bypass grafts, prior to reintervention. Early studies have suggested that CTA would be a viable substitute for DSA, but large randomized controlled trials are not available. Studies demonstrated the accuracy of CTA for evaluating PAOD, as well as strong concordance between CTA and DSA for establishing an accurate treatment plan. A randomized controlled trial comparing CTA (4-slice) to DSA demonstrated slightly lower physician confidence in CTA, but there were no significant differences in quality-of-life measures and outcomes, and CTA was significantly less expensive.

As MDCT has evolved, image quality has improved significantly with submillimeter z-axis resolution and isotropic data sets. A prospective randomized trial confirmed this when comparing CTA (16-detector) to DSA. The researchers reported CTA sensitivity of 96% and specificity of 97%, including identical sensitivity and specificity when evaluating the small infrapopliteal runoff vessels at a much lower radiation dose than DSA causes.

The choice of CTA or MRA for evaluating clinically suspect lower-extremity bypass grafts can be difficult. Both modalities have proved to be an effective substitute for DSA in the evaluation of PAOD and bypass graft analysis. A research group performed two randomized controlled trials comparing CTA and MRA. Physician confidence was similar between modalities, clinical outcomes were similar, but MRA was more expensive.

Summary

• Routine duplex US surveillance of lower-extremity bypass grafts has not been shown to improve the long-term patency of the grafts in a recent large randomized controlled trial.
• Many vascular surgeons continue to routinely image the grafts along with clinical examination and noninvasive testing (US segmental Doppler pressures and pulse recordings), until further evidence is available. When there is suspicion that a graft is at risk for failure and ultimately occlusion, endovascular or surgical intervention should be planned based on accurate anatomic mapping of the graft and the native inflow and outflow arteries.
• DSA has been and remains the gold standard, but there are downsides, including invasive risks, higher radiation dose, and cost.
• MRA and CTA have proven themselves to be equally accurate for evaluating bypass grafts at risk for failure, as well as progressive native vessel peripheral vascular disease. The choice between MRA and CTA will often be based on whether local expertise with MRA is available, as CTA is technically a more simple examination to perform.

Anticipated Exceptions

Nephrogenic systemic fibrosis (NSF) is a disorder with a scleroderma-like presentation and a spectrum of manifestations that can range from limited clinical sequelae to fatality. It appears to be related to both underlying severe renal dysfunction and the administration of gadolinium-based contrast agents. It has occurred primarily in patients on dialysis, rarely in patients with very limited glomerular filtration rate (GFR) (i.e., <30 mL/min/1.73 m²), and almost never in other patients. There is growing literature regarding NSF. Although some controversy and lack of clarity remain, there is a consensus that it is advisable to avoid all gadolinium-based contrast agents in dialysis-dependent patients unless the possible benefits clearly outweigh the risk, and to limit the type and amount in patients with estimated GFR rates <30 mL/min/1.73 m². For more information, please see the American College of Radiology (ACR) Manual on Contrast Media (see the "Availability of Companion Documents" field).

Abbreviations

• ABI, ankle-brachial indices
• CTA, computed tomography angiography
• Med, medium
• MRA, magnetic resonance angiography
• US, ultrasound

Algorithms were not developed from criteria guidelines.

The recommendations are based on analysis of the current literature and expert panel consensus.

Selection of appropriate radiologic imaging procedures to aid in differential diagnosis of patients with recurrent symptomatic and asymptomatic stenosis following lower extremity arterial bypass surgery

In addition to the regular magnetic resonance angiography (MRA) contraindications, artifacts from metallic clips and stents, as well as venous contamination can limit its utility for evaluating bypass grafts.

The American College of Radiology (ACR) Committee on Appropriateness Criteria and its expert panels have developed criteria for determining appropriate imaging examinations for diagnosis and treatment of specified medical condition(s). These criteria are intended to guide radiologists, radiation oncologists, and referring physicians in making decisions regarding radiologic imaging and treatment. Generally, the complexity and severity of a patient's clinical condition should dictate the selection of appropriate imaging procedures or treatments. Only those exams generally used for evaluation of the patient's condition are ranked. Other imaging studies necessary to evaluate other co-existent diseases or other medical consequences of this condition are not considered in this document. The availability of equipment or personnel may influence the selection of appropriate imaging procedures or treatments. Imaging techniques classified as investigational by the U.S. Food and Drug Administration (FDA) have not been considered in developing these criteria; however, study of new equipment and applications should be encouraged. The ultimate decision regarding the appropriateness of any specific radiologic examination or treatment must be made by the referring physician and radiologist in light of all the circumstances presented in an individual examination.

An implementation strategy was not provided.

Not applicable: The guideline was not adapted from another source.

The American College of Radiology (ACR) provided the funding and the resources for these ACR Appropriateness Criteria®.

Committee on Appropriateness Criteria, Expert Panel on Vascular Imaging

Panel Members: Scott A. Koss, MD (Principal Author); E. Kent Yucel, MD (Panel Chair); Frank J. Rybicki, MD, PhD (Panel Vice-Chair); Richard A. Baum, MD; Benoit Desjardins, MD, PhD; Scott D. Flamm, MD; W. Dennis Foley, MD; Michael R. Jaff, DO; Leena Mammen, MD; M. Ashraf Mansour, MD; Vamsidhar R. Narra, MD

Not stated

This is the current release of the guideline.

This guideline updates a previous version: Casciani T, Bettmann MA, Gomes AS, Grollman JH, Holtzman SR, Polak JF, Sacks D, Schoepf J, Stanford W, Jaff M, Moneta GL, Expert Panel on Cardiovascular Imaging. Follow-up of lower extremity arterial bypass surgery. [online publication]. Reston (VA): American College of Radiology (ACR); 2005. 6 p. [30 references]

The appropriateness criteria are reviewed biennially and updated by the panels as needed, depending on introduction of new and highly significant scientific evidence.

Electronic copies: Available in Portable Document Format (PDF) from the American College of Radiology (ACR) Web site.

Print copies: Available from the American College of Radiology, 1891 Preston White Drive, Reston, VA 20191. Telephone: (703) 648-8900.

The following are available:

• ACR Appropriateness Criteria®. Overview. Reston (VA): American College of Radiology; 2 p. Electronic copies: Available in Portable Document Format (PDF) from the American College of Radiology (ACR) Web site.
• ACR Appropriateness Criteria®. Literature search process. Reston (VA): American College of Radiology; 1 p. Electronic copies: Available in Portable Document Format (PDF) from the ACR Web site.
• ACR Appropriateness Criteria®. Evidence table development. Reston (VA): American College of Radiology; 4 p. Electronic copies: Available in Portable Document Format (PDF) from the ACR Web site.
• ACR Appropriateness Criteria®. Radiation dose assessment introduction. Reston (VA): American College of Radiology; 2 p. Electronic copies: Available in Portable Document Format (PDF) from the ACR Web site.
• ACR Appropriateness Criteria® Manual on contrast media. Reston (VA): American College of Radiology; 90 p. Electronic copies: Available in PDF from the ACR Web site.

None available

This summary was completed by ECRI on February 20, 2001. The information was verified by the guideline developer on March 14, 2001. This summary was updated by ECRI on March 29, 2006. This NGC summary was updated by ECRI Institute on June 8, 2010. This summary was updated by ECRI Institute on January 13, 2011 following the U.S. Food and Drug Administration (FDA) advisory on gadolinium-based contrast agents.

Instructions for downloading, use, and reproduction of the American College of Radiology (ACR) Appropriateness Criteria® may be found on the ACR Web site .