Accompanying the rapid growth of interest in percutaneous vascular interventions, there has been increasing interest among cardiologists in performing noninvasive vascular testing using ultrasound. In an attempt to provide recommendations on the best practices in vascular laboratory testing, this report has been prepared by a writing group from the American Society of Echocardiography (ASE) and the Society of Vascular Medicine and Biology. The document summarizes principles integral to vascular duplex ultrasound–including color Doppler, spectral Doppler waveform analysis, power Doppler, and the use of contrast. Appropriate indications and interpretation of carotid artery, renal artery, abdominal aorta, and peripheral artery ultrasound imaging are described. A dedicated section summarizes noninvasive techniques for physiologic vascular testing of the lower extremity arteries–including measurement of segmental pressures and pulse volume plethysmography. The use of exercise testing in the evaluation of peripheral artery disease, ultrasound evaluation of the lower extremities after percutaneous revascularization, and the diagnosis and management of iatrogenic pseudoaneurysm (PSA) is also discussed. A section on the important topic of vascular laboratory accreditation is included. Finally, additional details regarding proper technique for performance of the various vascular tests and procedures are included in the Appendix. There has been increasing demand for vascular ultrasound training among cardiologists in practice and in training. For example, the recent document on training for cardiology fellows, COCATS-2, has recommended 2 months of dedicated or aggregate “instruction in the noninvasive laboratory” for Level 1 training in vascular ultrasound.1Beller G.A. Bonow R.O. Fuster V. ACC revised recommendations for training in adult cardiovascular medicine core cardiology training II (COCATS 2) (revision of the 1995 COCATS training statement).J Am Coll Cardiol. 2002; 39: 1242-1246Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar This article will review general principles, indications, and interpretation of noninvasive vascular testing of the carotid arteries, renal arteries, abdominal aorta, and peripheral arteries. Additional details regarding the techniques of performing vascular ultrasound are provided in the Appendix. Another article by this working group, “Clinical Application of Noninvasive Vascular Ultrasound in Cardiovascular Risk Stratification,” will review the application of carotid artery (intimal-medial thickness) and brachial artery (flow-mediated dilatation) measurements for cardiovascular risk stratification. Vascular testing includes duplex ultrasound and physiologic evaluation. Vascular ultrasound tests require a machine equipped with 5- to 12-MHz linear-array transducers (for the neck and extremities) and 2.25- to 3.5-MHz curved linear- or phased-array transducers (for the abdomen). A vascular software package is required in addition to the appropriate transducers. Duplex scanning refers to an ultrasound scanning procedure recording both gray scale and Doppler information. This includes 2-dimensional structure and motion, Doppler spectrum analysis, and color flow velocity mapping. Carotid arteries, renal arteries, abdominal aorta, and peripheral arteries can be appropriately evaluated using this equipment. Physiologic testing includes segmental pulse volume recording and segmental pressure measurements with cuffs appropriately sized for the lower extremities and a plethysmographic recording device. The ultrasound beam is directed perpendicular to the surface of interest to obtain the brightest echo with gray-scale imaging and optimal imaging of the artery wall. The perpendicular angle is often readily obtained, as arteries generally are parallel to the surface of the transducer (Figure 1). For the Doppler component of duplex imaging, an angle of 60 degrees between the Doppler insonation beam and the vessel wall should be maintained. This Doppler angle becomes an important consideration when the velocity data are used to classify disease.2Philips D. Beach K. Primozich J. Should results of ultrasound Doppler criteria be reported in units of frequency or velocity?.Ultrasound Med Biol. 1989; 15: 205-212Abstract Full Text PDF PubMed Scopus (53) Google Scholar Angles above 60 degrees can result in significant overestimation of the velocity and should be avoided. Angles that are not relevant to the vessel wall may misrepresent the true peak velocity3Logason K. Barlin T. Jonsson M.L. et al.The importance of Doppler angle of insonation on differentiation between 50-69% and 70-99% carotid artery stenosis.Eur J Endovasc Surg. 2001; 21: 311-313Abstract Full Text PDF PubMed Scopus (45) Google Scholar (Figure 2).Figure 2Angle of 60 degrees of Doppler insonation relative to vessel axis provides most accurate Doppler velocities. Angle correction should be used to maintain Doppler angle of 60 degrees or less. Doppler cursor should be parallel to vessel axis in center stream of arterial flow. Left, Appropriate alignment of Doppler beam at 60 degrees to vessel wall with sample volume cursor parallel to vessel axis (imaginary line drawn in center of vessel). Right, Inaccurate Doppler angle. There is misalignment of the cursor not parallel to vessel axis. Pulsed wave Doppler images obtained from same internal carotid artery demonstrates underestimation of peak systolic velocity with inaccurate Doppler angle (right).View Large Image Figure ViewerDownload Hi-res image Download (PPT) The pulse repetition frequency scale determines the degree of color saturation and is adjusted so that normal laminar flow appears as a region of homogeneous color. Stenosis results in the production of a high velocity jet and an abrupt change in the color flow pattern. This is identified as either aliasing or desaturation (whitening) of the color display at the site of luminal narrowing. Aliasing occurs when the flow velocity exceeds the Nyquist limit and results in color display of the reverse flow direction (wrap around). The poststenotic region demonstrates a mosaic pattern indicating turbulent flow (Figure 3). Gray-scale settings are adjusted to optimize visualization of intraluminal plaque or thrombus at these sites of abnormal flow. Color Doppler provides additional information used to detect a significant stenosis. Color aliasing, persistence, and bruit all indicate flow disturbance. Color persistence is a continuous flow signal that is color of the forward direction only, in contrast to the alternating color in normal arteries.4Pellerito J. Color persistence indicator of hemodynamically significant peripheral arterial stenosis.Radiology. 1991; 181: 89PubMed Google Scholar Color persistence corresponds to the monophasic spectral Doppler waveform of severe stenosis. A color bruit in the surrounding soft tissue also indicates flow disturbance. This color artifact is attributed to vibration in the surrounding soft tissue in the presence of a high velocity jet. Abnormalities of color flow indicate possible stenosis that is then characterized using pulsed wave Doppler determination of velocities. A normal pulsed wave Doppler waveform is a sharply defined tracing with a narrow Doppler spectrum indicating that blood cells are moving at similar speed throughout the cardiac cycle (Figure 4). Flow becomes turbulent at bifurcations and luminal narrowings causing spectral broadening of Doppler waveform, with filling in of the low velocity region in the spectral waveform as the blood cells move at a wide range of velocities (Figure 4). The normal peripheral artery waveform is triphasic (Figure 4). The first component is the consequence of initial forward flow during systole, and results in peak systolic velocity (PSV) measurements that are typically less than 125 cm/s5Jager K. Non-invasive mapping of lower limb arterial lesions.Ultrasound Med Biol. 1985; 11: 515-521Abstract Full Text PDF PubMed Scopus (243) Google Scholar for each arterial segment. There is early diastolic flow reversal in the second phase of the waveform as left ventricular pressure decreases before aortic valve closure. In late diastole, there is a small amount of forward flow that reflects elastic recoil of vessel walls. This diastolic component is absent in stiff atherosclerotic vessels. Waveform shape is also characterized as high resistance (eg, normal peripheral arterial waveform), or low resistance (eg, normal internal carotid artery [ICA] waveform) (Figure 4). The amount of flow during diastole is determined by the degree of dilation in the distal resistance arterioles. Power (or energy) Doppler is a technique that displays the total strength (amplitude) of the returning Doppler signal without distinguishing direction.6Rubin J. Power Doppler US a potentially useful alternative to mean frequency-based color Doppler US.Radiology. 1994; 190: 853-856PubMed Google Scholar Sensitivity is increased by a factor of 3 to 5 times6Rubin J. Power Doppler US a potentially useful alternative to mean frequency-based color Doppler US.Radiology. 1994; 190: 853-856PubMed Google Scholar with power Doppler compared with color flow Doppler. Power Doppler can, therefore, identify very slow flow that may not be detected by color flow Doppler. Power Doppler is less angle dependent than is color Doppler and it improves delineation of the lumen.7Griewing B. Doherty C. Kessler C. Power Doppler ultrasound examination of the intracerebral and extracerebral vasculature.J Neuroimaging. 1996; 6: 32-35PubMed Google Scholar Power Doppler is used to differentiate high-grade stenosis from occlusion, to detect collateral vessels, and to identify small vessel disease. Doppler velocity is the main tool used to evaluate stenosis severity. Characteristic duplex ultrasound features of stenosis include elevated velocities, color disturbance, spectral broadening, and poststenotic waveforms (Table 1). If no poststenotic turbulence can be identified, inappropriate angle alignment or a tortuous vessel should be suggested as a cause of artifactually high velocities.Table 1Duplex evidence of arterial stenosis •Elevated velocities: diagnostic criteria use peak systolic velocity (eg, >125 cm/s), ratios of distal to proximal sequential peak systolic velocities (eg, 2:1), and elevated end-diastolic velocity, supportive criteria include aliasing of color Doppler signal•Diameter reduction: transverse or longitudinal measurements indicating reduction in luminal diameter are supportive, not diagnostic•Spectral broadening or color mosaic pattern: the presence of turbulent flow is supportive, not diagnostic; it is most prominent just distal to significant stenosis•Color bruit, color persistence: color bruit, providing evidence of vibration in the tissue surrounding arterial narrowing, is supportive, not diagnostic; continuous forward flow, or persistence, is supportive evidence of arterial stenosis Open table in a new tab Ultrasonographic assessment of peripheral vascular disease is largely dependent on the functioning of the equipment and the skill of the operator.8Beckett Jr, W.W. Davis P.C. Hoffman Jr, J.C. Duplex Doppler sonography of the carotid artery false-positive results in an artery contralateral to an artery with marked stenosis.AJNR Am J Neuroradiol. 1990; 11: 1049-1053PubMed Google Scholar The addition of duplex color Doppler techniques has allowed for improved identification of the anatomy of peripheral vascular disorders, including the location, length, and presence of stenosis or occlusion; development of collateral vessels; and areas of reconstitution. Ultrasound contrast agents also appear useful in enhancing suboptimal images and improving arterial diagnosis in areas where calcification in the vessel wall obscures the view of the lumen and the ability to determine velocity.3Logason K. Barlin T. Jonsson M.L. et al.The importance of Doppler angle of insonation on differentiation between 50-69% and 70-99% carotid artery stenosis.Eur J Endovasc Surg. 2001; 21: 311-313Abstract Full Text PDF PubMed Scopus (45) Google Scholar Contrast agents have been shown investigationally to better outline the lumen of the carotid arteries and facilitate measurement of intimal-medial thickness, and to help in outlining plaque morphology, and in differentiating between occlusion and high-grade stenosis. Contrast enhancement of the renal vasculature has been reported to be useful in cases where multiple main renal arteries are present.3Logason K. Barlin T. Jonsson M.L. et al.The importance of Doppler angle of insonation on differentiation between 50-69% and 70-99% carotid artery stenosis.Eur J Endovasc Surg. 2001; 21: 311-313Abstract Full Text PDF PubMed Scopus (45) Google Scholar, 9Ringer A.J. et al.Follow-up of stented carotid arteries by Doppler ultrasound.Neurosurgery. 2002; 51: 639-643PubMed Google Scholar Several large-scale studies have found improvement in peripheral artery diagnosis using contrast after suboptimal baseline ultrasound scans.10Yadav J.S. et al.Protected carotid-artery stenting versus endarterectomy in high-risk patients.N Engl J Med. 2004; 351: 1493-1501Crossref PubMed Scopus (2537) Google Scholar Contrast appears to have use in improving images of vessels difficult to adequately capture using traditional ultrasound techniques, such as the iliac arteries, the superficial artery in the adductor canal, the trifurcation vessels, and the plantar arteries. Contrast enhancement may also be useful in differentiating between patent and nonpatent vessels in patients with conditions that interfere with ultrasound scanning (ie, obesity, edema, dense calcification).11Medicare services of Missouri draft policy for non-invasive vascular studies. AC-PN 2003-01, pg. 29, March 2003.Google Scholar Nonetheless, it should be emphasized that despite these reports documenting the efficacy of contrast agents in enhancing vascular ultrasound imaging, they have not received US Food and Drug Administration approval for all these indications and, hence, this application should still be, at present, considered experimental. The goal of noninvasive ultrasound testing for carotid disease is to distinguish normal from diseased vessels, to classify a wide range of disease states, to assess the cerebral collateral circulation, and to do so in a safe and cost-effective manner. The primary aim is to identify patients who are at risk for stroke and who may require specific treatment. A secondary aim is to document progressive or recurrent disease in patients already known to be at risk. Appropriate indications for carotid artery testing are listed in Table 2.12Fell G. Breslau P. Knox R. Importance of non-invasive ultrasonic Doppler testing in the evaluation of patients/asymptomatic carotid bruits.Am Heart J. 1981; 102: 221-226Abstract Full Text PDF PubMed Scopus (21) Google Scholar, 13Zwiebel W.J. Duplex sonography of the cerebral arteries efficacy, limitations, and indications.AJR Am J Roentgenol. 1992; 158 ([comment]): 29-36Crossref PubMed Scopus (48) Google Scholar, 14Ackerstaff R.G. et al.Ultrasonic duplex scanning of the prevertebral segment of the vertebral artery in patients with cerebral atherosclerosis.Eur J Vasc Surg. 1988; 2: 387-393Abstract Full Text PDF PubMed Scopus (23) Google Scholar, 15Transamerica Occidental Life Insurance Company payment safeguard administrator proposal local medical review policy for the state of California for noninvasive vascular studies.Google ScholarTable 2Indications for carotid artery ultrasound •Cervical bruits•Amaurosis fugax•Hemispheric stroke•Focal cerebral or ocular transient ischemic attacks (which demonstrate localizing symptoms, such as weakness of one side of the face, slurred speech, weakness of a limb, retinal or hemispheric visual field deficits)•Drop attacks or syncope (rare indications primarily seen in vertebrovascular insufficiency or bilateral carotid artery disease)•Vasculitis involving extracranial arteries•Pulsatile mass in the neck•Trauma to neck•Follow-up of carotid artery atherosclerosis not requiring revascularization•Follow-up surveillance after carotid revascularization, a baseline ultrasound is recommended within 30 days after carotid stenting Open table in a new tab Duplex imaging should include, at a minimum, common carotid artery (CCA), ICA, external carotid artery, and vertebral artery. The interpretation of the spectral waveforms is based on parameters such as PSV, end-diastolic velocity, and the extent of spectral broadening (Figure 5). Individual vascular laboratories must validate their own results against a suitable gold standard (eg, arteriography). Several velocity criteria used to detect presence and severity of carotid artery disease have been published.16Grant E.G. et al.Carotid artery stenosis gray-scale and Doppler US diagnosis–Society of Radiologists in Ultrasound consensus conference.Radiology. 2003; 229: 340-346Crossref PubMed Scopus (1054) Google Scholar Table 3 summarizes useful absolute velocities and velocity ratios to diagnose significant ICA stenosis.16Grant E.G. et al.Carotid artery stenosis gray-scale and Doppler US diagnosis–Society of Radiologists in Ultrasound consensus conference.Radiology. 2003; 229: 340-346Crossref PubMed Scopus (1054) Google Scholar When all categories of carotid disease are considered, criteria distinguishing between normal and diseased ICA have a specificity of 84% and a sensitivity of 99% when compared with angiography.17Langlois Y. Roederer G. Strandness D.J. Ultrasonic evaluation of carotid bifurcation.Echocardiography. 1987; 4: 141-159Crossref Scopus (14) Google Scholar The accuracy for detecting 50% to 99% diameter stenosis is 93%. The agreement with angiography is excellent for classification of lesions that result in greater than 50% diameter reduction.18Roederer G. Langlois Y. Jager K. A simple spectral parameter for accurate classification of severe carotid artery disease.Bruit. 1989; 3: 174-178Google Scholar Experience with duplex scanning in patients undergoing carotid endarterectomy indicates that the results of arteriography rarely altered the clinical treatment plan when a technically adequate duplex scan showed an 80% to 99% stenosis in an asymptomatic patient, or ipsilateral 50% to 99% stenosis in a patient with hemispheric neurologic symptoms.19Mattos M.A. Hodgson K.J. Faught W. Carotid endarterectomy without angiography is color-flow duplex scanning sufficient?.Surgery. 1994; 116: 776-783PubMed Google Scholar, 20Dawson D. Zierler R. Strandess D.J. The role of duplex scanning and arteriography before endarterectomy a prospective study.J Vasc Surg. 1993; 18: 673-683Abstract Full Text Full Text PDF PubMed Scopus (151) Google ScholarTable 3Criteria for classification of internal carotid artery disease by duplex scanning with spectral waveform analysis of pulsed Doppler signalsDegree of stenosis, %ICA/PSV, cm/sPlaque estimate, %ICA EDV, cm/sICA CCA PSV ratioNormal<1250<40<2<50<125<50<40<250-69125-230>5040-1002-4>70>230>50>100>4Subtotal occlusionVariable>50 Narrow lumen>0VariableTotal occlusion0>500<1CCA, Common carotid artery; EDV, end-diastolic velocity; ICA, internal carotid artery; PSV, peak systolic velocity. Open table in a new tab CCA, Common carotid artery; EDV, end-diastolic velocity; ICA, internal carotid artery; PSV, peak systolic velocity. Absolute velocity criteria by duplex ultrasound may be less reliable than change in velocity criteria over time to diagnose recurrent stenosis after carotid artery stenting. A thumping sound may be encountered at the origin of the occluded ICA as a result of flow striking the occlusion followed by flow reversal. Stenosis proximal to the imaged segment is suggested by parvus et tardus waveforms. Diagnosis criteria for stenosis in the CCA are less extensively described. A doubling of PSV from proximal to distal sample indicates greater than 50% stenosis. A parvus et tardus waveform in the CCA again suggests there is stenosis proximal to the imaged region. Interpretation should comment on the direction of vertebral artery flow, forward (toward the brain) or reverse (away from the brain). In addition, the vertebral artery waveform should be described as normal (low resistance) or abnormal (biphasic or high resistance). Correct determination of ICA versus external carotid artery is essential for interpretation of study results (Table 4).Table 4Differentiation of internal and external carotid arteriesInternal carotid arteryExternal carotid artery •Usually larger•Usually lateral and posterior•Usually incorporates carotid bulb•No branches in the neck•Low resistance spectral waveform•Usually no oscillations in Doppler on temporal tap test •Usually smaller•Usually medial and anterior•Usually does not incorporate bulb•Eight branches in the neck•High resistance spectral waveform at rest•Visible and audible oscillations on Doppler signal waveform on temporal tap test Open table in a new tab Disease may be underestimated in the presence of long smooth plaque that does not have the accelerated turbulent flow patterns associated with hemodynamically significant lesions. High and low cardiac output can affect PSV. In the setting of markedly abnormal cardiac output, the ICA/CCA PSV ratio should be the primary diagnostic criteria for ICA stenosis. Contralateral ICA occlusion may result in overestimation of stenosis in the ipsilateral carotid artery,8Beckett Jr, W.W. Davis P.C. Hoffman Jr, J.C. Duplex Doppler sonography of the carotid artery false-positive results in an artery contralateral to an artery with marked stenosis.AJNR Am J Neuroradiol. 1990; 11: 1049-1053PubMed Google Scholar due to compensatory increase in peak systolic velocity. Atherosclerotic renal artery stenosis has become increasingly recognized as a contributing factor to resistant hypertension,21Hollenberg N.K. Medical therapy for renovascular hypertension a review.Am J Hypertens. 1988; 1: 338-343SCrossref Scopus (11) Google Scholar and may promote deterioration in renal function. Patients with severe bilateral renal artery stenosis, or stenosis to a solitary functioning kidney, are at risk for the development of end-stage renal disease.22Mailloux L.U. et al.Renal vascular disease causing end-stage renal disease, incidence, clinical correlates, and outcomes a 20-year clinical experience.Am J Kidney Dis. 1994; 24: 622-629PubMed Scopus (374) Google Scholar Long-term survival of patients with atherosclerotic renal artery stenosis requiring dialysis support is dismal.23Scoble J.E. et al.Atherosclerotic renovascular disease causing renal impairment–a case for treatment.Clin Nephrol. 1989; 31: 119-122PubMed Google Scholar Although a number of noninvasive methods of diagnosis in renal artery stenosis have been proposed, none have obviated the role of the gold standard, renal arteriography. Each screening test has significant limitations that prevent widespread acceptance. Duplex ultrasonography is the ideal method of determining the adequacy of renal artery revascularization (Table 5).25Eidt J. Fry R. Clagett G. Postoperative follow-up of renal artery reconstruction with duplex ultrasound.J Vasc Surg. 1988; 8: 667-673PubMed Scopus (24) Google Scholar Duplex ultrasonography is helpful in detecting important areas of restenosis after endovascular therapy (percutaneous angioplasty with stent deployment).26Dorros G. Jaff M. Mathiak L. Four-year follow-up of Palmaz-Schatz stent revascularization as treatment for atherosclerotic renal artery stenosis.Circulation. 1998; 98: 642-647Crossref PubMed Scopus (393) Google Scholar The renal duplex examination includes spectral Doppler velocities from the renal arteries, renal parenchyma, and abdominal aorta. PSV and peak end-diastolic velocities obtained in branches of the renal artery at the level of the medulla are used to calculate the renal resistive index, a value reflecting the health of the renal parenchyma itself (Table 6). In addition, the examination should define the pole-to-pole length of each kidney. Figure 6 illustrates duplex findings of renal artery stenosis.Table 5Indications for renal duplex ultrasound24Gray B.H. et al.Clinical benefit of renal artery angioplasty with stenting for the control of recurrent and refractory congestive heart failure.Vasc Med. 2002; 7: 275-279Crossref PubMed Scopus (173) Google Scholar •Sudden exacerbation of previously well-controlled hypertension•New onset hypertension at a young age•Malignant hypertension•Unexplained azotemia•Hypertension and aortoiliac or infrainguinal atherosclerosis•Azotemia after administration of an angiotensin-converting enzyme inhibitor•An atrophic kidney•Recurrent flash pulmonary edema without cardiac explanation•Evaluation of adequacy of renal artery revascularization•Detection of restenosis after endovascular therapy Open table in a new tab Table 6Diagnostic criteria for significant renal artery stenosisRenal artery to aorta peak systolic velocity ratio is >3.5PSV > 200 cm/s with evidence of poststenotic turbulenceEDV > 150 cm/s (>80% renal artery stenosis)RI > 0.8 (used to predict response of blood pressure, renal function, to renal revascularization)An occluded renal artery demonstrates no flow in the affected vesselEDV, End-diastolic velocity; PSV, peak systolic velocity; RI, resistive index (1 − [EDV/maximum systolic velocity] × 100). Open table in a new tab EDV, End-diastolic velocity; PSV, peak systolic velocity; RI, resistive index (1 − [EDV/maximum systolic velocity] × 100). Ultrasound imaging is highly sensitive for assessing and following up abdominal aneurysms.27Harter L.P. et al.Ultrasonic evaluation of abdominal aortic thrombus.J Ultrasound Med. 1982; 1: 315-318PubMed Google Scholar, 28Steiner E. et al.Sonographic examination of the abdominal aorta through the left flank a prospective study.J Ultrasound Med. 1986; 5: 499-502PubMed Google Scholar A family history of an abdominal aneurysm has been reported to increase the risk of developing this condition 4-fold. In addition, if an aneurysm is found in one vascular territory, such as the popliteal artery, there is an increased risk of an aneurysm in the aorta. Major indications for assessment of abdominal aortic aneurysm with ultrasound imaging are included in Table 7.Table 7Indications for abdominal aorta ultrasound •Abdominal pain•Pulsatile and enlarged aorta on physical examination•Hemodynamic compromise suggestive of a ruptured aneurysm•An immediate family member with a history of abdominal aortic aneurysm•An aneurysm found in another vascular territory•Follow-up of aortic endograft Open table in a new tab A normal diameter of the abdominal aorta is approximately 2.0 cm (range: 1.4-3.0 cm) in most individuals (Table 8). A mildly dilated abdominal aorta is described as ectatic, whereas it is reported as aneurysmal when the diameter is greater than 3.0 cm.28Steiner E. et al.Sonographic examination of the abdominal aorta through the left flank a prospective study.J Ultrasound Med. 1986; 5: 499-502PubMed Google Scholar, 29Yucel E.K. et al.Sonographic measurement of abdominal aortic diameter interobserver variability.J Ultrasound Med. 1991; 10: 681-683PubMed Google Scholar Abdominal aortic aneurysms are described as saccular (ie, having a baglike structure protruding asymmetrically from the aorta); fusiform (ie, spindle-shaped and tapering from the middle toward each end); or cylindric. The majority of abdominal aortic aneurysms are fusiform in shape, located below the renal arteries, and they may involve one or both of the iliac arteries. Atherosclerotic changes and/or mural thrombus can line the aneurysmal sac. Dissection has been reported with abdominal aortic aneurysm, but is not common. The typical growth rate reported in the literature of abdominal aortic aneurysms measuring 3 to 5.9 cm is approximately 0.3 to 0.4 cm per year.30Scott R.A. Ashton H.A. Kay D.N. Abdominal aortic aneurysm in 4237 screened patients prevalence, development and management over 6 years.Br J Surg. 1991; 78 ([comment]): 1122-1125Crossref PubMed Scopus (253) Google Scholar However, larger aneurysms may progress more quickly than others. Aneurysms repaired by endografts and endovascular stents have unique ultrasound characteristics. Thrombus develops in the aneurysm outside of the endograft. Over time, the maximal diameter of the aneurysm sac surrounding an endograft is expected to decrease.Table 8Diagnostic criteria for abdominal aortic aneurysm and endoleak •Aneurysm: diameter > 3.0 cm•Endoleak: flow outside of the aortic endograft, and within the aneurysm sac•Dissection: true and false lumen present Open table in a new tab The goals of noninvasive testing for peripheral arterial disease are to confirm a clinical diagnosis and further define the level and extent of obstruction. A variety of algorithms are used to noninvasively diagnose peripheral arterial disease in the vascular laboratory. Some of these include segmental limb pressures with pulse volume plethysmography, exercise treadmill testing, and arterial ultrasonography. The major indications for assessment of peripheral arterial disease with noninvasive testing are summarized in Table 9.Table 9Indications for noninvasive physiologic testing •Exercise-related limb pain (claudication symptoms)•Limb pain at rest•