The Common Carotid Artery in the Ultrasound Evaluation of Giant Cell Arteritis

OBJECTIVES

Vascular ultrasound is commonly used to diagnose giant cell arteritis (GCA). Most protocols include the temporal arteries and axillary arteries, but it is unclear which other arteries should be included. This study investigated whether inclusion of intima media thickness (IMT) of the common carotid artery (CCA) in the ultrasound evaluation of GCA improves the accuracy of the examination.

METHODS

We formed a fast-track clinic to use ultrasound to rapidly evaluate patients with suspected GCA. In this cohort study, patients referred for new concern for GCA received a vascular ultrasound for GCA with the temporal arteries and branches, the axillary artery, and CCA.

RESULTS

We compared 57 patients with GCA and 86 patients without GCA. Three patients with GCA had isolated positive CCA between 1 and 1.49 mm, and 21 patients without GCA had isolated positive CCA IMT. At the 1.5-mm CCA cutoff, 4 patients without GCA had positive isolated CCA, and 1 patient with GCA had a positive isolated CCA. The sensitivity of ultrasound when adding carotid arteries to temporal and axillary arteries was 84.21% and specificity 65.12% at an intima media thickness (IMT) cutoff of ≥1 mm and 80.70% and 87.21%, respectively, at a cutoff of ≥1.5 mm.

CONCLUSION

Measurement of the CCA IMT rarely contributed to the diagnosis of GCA and increased the rate of false-positive results. Our data suggest that the CCA should be excluded in the initial vascular artery ultrasound protocol for diagnosing GCA. If included, an IMT cutoff of higher than 1.0 mm should be used.

The Usefullness of Subclavian Artery Ultrasound Assessment in Giant Cell Arteritis Evaluation

OBJECTIVE

Vascular ultrasound has been increasingly used to diagnose giant cell arteritis (GCA). The temporal and axillary arteries are commonly evaluated. However, the usefulness of including the subclavian artery remains unclear. This study investigated whether inclusion of the subclavian artery in addition to the temporal and axillary arteries in the ultrasound evaluation of GCA improves the accuracy of the examination beyond ultrasonography of the temporal and axillary arteries alone.

METHODS

We formed a fast-track clinic to use ultrasound to rapidly evaluate patients with suspected GCA. In this cohort study, patients referred for new concern for GCA received a vascular ultrasound for GCA. Subclavian intima-media thickness (IMT) cutoffs of 1.0 and 1.5 mm were retrospectively assessed.

RESULTS

Two hundred thirty-seven patients were referred to the fast-track clinic from November 2017 to August 2021. One hundred sixty-eight patients received an ultrasound for concern for new GCA. With a subclavian IMT cutoff of 1.5 mm, inclusion of the subclavian artery did not identify any patients with GCA who were not otherwise found to have positive temporal and/or axillary artery examinations, and at this cutoff, there was 1 false-positive result. A subclavian IMT cutoff of 1.0 mm identified several subjects diagnosed with GCA who had otherwise negative ultrasounds, but most subjects with an isolated subclavian IMT greater than 1.0 mm had false-positive results, and the specificity of this cutoff was poor.

CONCLUSION

Inclusion of the subclavian artery in the ultrasound assessment of GCA at 2 different cutoffs rarely contributed to the accurate diagnosis of GCA and increased the rate of false-positive results.

Vascular Ultrasound for Giant Cell Arteritis: Establishing a Protocol Using Vascular Sonographers in a Fast-Track Clinic in the United States

Objective

We developed a fast‐track clinic (FTC) to expedite the evaluation of patients suspected of having giant cell arteritis (GCA) using vascular ultrasound. Though FTCs have demonstrated efficacy in Europe, no protocolized clinic in the United States has been developed. This study introduces a new FTC model unique to the United States, using vascular sonographers, and describes the protocols used to develop reliable findings. We evaluate clinical outcomes using vascular ultrasound and temporal artery biopsy (TAB).

Methods

A retrospective review included all subjects referred to the University of Washington FTC aged 50 years old or older who received both ultrasound and TAB between November 2017 and November 2019. Ultrasound was performed by a vascular sonographer trained in GCA detection. Ultrasound results were read by a vascular surgeon and reviewed by four rheumatologists certified in musculoskeletal ultrasound who had completed a course in vascular ultrasound use in GCA and large‐vessel vasculitis.

Results

A total of 43 subjects underwent both vascular ultrasound and TAB. Six subjects had both positive ultrasound and TAB results. There were also seven positive ultrasound results in patients with negative TAB results, most due to detection of large‐vessel GCA (LV‐GCA). All 29 subjects with negative ultrasound results had negative TAB results.

Conclusion

This is the first study in the United States to demonstrate a reliable FTC protocol using vascular sonographers. This protocol demonstrated good agreement between ultrasound and TAB and allowed for the detection of additional cases of LV‐GCA by vascular ultrasound. Vascular ultrasound improved the rate of GCA diagnosis primarily by detecting additional cases of LV‐GCA.

Changes in Internal Carotid Artery Doppler Velocity Measurements With Different Angles of Insonation: A Pilot Study

OBJECTIVES

Doppler velocity measurements are fundamental diagnostic criteria for vascular ultrasound examinations. Insonation angles are kept to 60° or less to minimize error. The purpose of this study was to assess variance of Doppler-detected peak systolic velocity (PSV) measurements in the internal carotid arteries at different angles (45°, 50°, 55°, and 60°) with different beam steering.

METHODS

The PSV was recorded from the right and left internal carotid arteries in 22 asymptomatic volunteers with straight vessels (total of 44 vessels). A standardized approach was used for recording velocities with the Doppler cursor center steered and steered 15° from right to left. An analysis of variance was performed.

RESULTS

The PSV varied significantly with the 4 different angles of insonation (P < .01). The maximum variation between 45° and 60° angles within a single vessel was 29 cm/s. The average variation over the 4 angles was 14 ± 6 cm/s. Relative to the calculated mean velocity for all patients, the standard deviation for the PSV at 60° was nearly twice that recorded at 50° (7.9 versus 3.9). The best correlation of the calculated mean velocity for all patients existed between the angles of 45° and 50° [r(36) = 0.92; P < .001 for center-steered data; and r(40) = 0.96; P < .001 for right-steered data].

CONCLUSIONS

These results indicate a statistically significant difference in the PSV measurements taken at varying Doppler angles. The greatest mean, variance, and lowest correlations all result when using 60°. The findings support the need for consistent ultrasound techniques and suggest that further study is warranted regarding the optimal Doppler angle for velocity measurements.

From Doppler to duplex: A personal early history of the vascular laboratory

In the mid-1970s, a group of clinicians and bioengineers at the University of Washington, under the direction of Dr D Eugene Strandness, Jr, built a prototype duplex scanner that combined B-mode imaging and pulsed Doppler flow detection in a single instrument. At that time, I was a general surgery resident with an interest in vascular disease, and arrangements were made for me to spend a year in the Strandness laboratory. The prototype duplex system was just being completed when I arrived in 1978, and I immediately became involved in a series of validation studies in which patients with carotid disease were scanned and spectral waveform parameters were correlated with independently read contrast arteriograms. This work resulted in the University of Washington duplex criteria for carotid artery disease, which have been widely adopted and modified. Subsequent advances in ultrasound technology expanded the applications of duplex scanning to the peripheral arteries and veins, as well as the abdominal vessels. In 1984, I joined Dr Strandness on the faculty in the Department of Surgery at the University of Washington where I have remained throughout my career. Over the years, I have had the opportunity to participate in many important developments, described in this article, that have helped to make the vascular laboratory the essential clinical resource that it is today.

Interpretation of peripheral arterial and venous Doppler waveforms: A consensus statement from the Society for Vascular Medicine and Society for Vascular Ultrasound

This expert consensus statement on the interpretation of peripheral arterial and venous spectral Doppler waveforms was jointly commissioned by the Society for Vascular Medicine (SVM) and the Society for Vascular Ultrasound (SVU). The consensus statement proposes a standardized nomenclature for arterial and venous spectral Doppler waveforms using a framework of key major descriptors and additional modifier terms. These key major descriptors and additional modifier terms are presented alongside representative Doppler waveforms, and nomenclature tables provide context by listing previous alternate terms to be replaced by the new major descriptors and modifiers. Finally, the document reviews Doppler waveform alterations with physiologic changes and disease states, provides optimization techniques for waveform acquisition and display, and provides practical guidance for incorporating the proposed nomenclature into the final interpretation report.

Duplex ultrasound follow-up after fenestrated and branched endovascular aneurysm repair (FEVAR and BEVAR)

Endovascular aneurysm repair (EVAR) is now the predominant method for treatment of infrarenal abdominal aortic aneurysms. Although EVAR has numerous advantages over standard open surgical repair, it also exposes patients to risks such as aneurysm sac enlargement, endoleaks, and graft migration, which make surveillance or follow-up mandatory. Fenestrated (FEVAR) and branched (BEVAR) endografts have extended the application of EVAR to juxtarenal, pararenal/paravisceral, and thoracoabdominal aneurysms, with some complex aneurysms requiring combined approaches (F-BEVAR). Duplex ultrasound has been recommended as an alternative to frequent computed tomography imaging for EVAR follow-up when it can provide the clinically necessary information. The major components of a post-EVAR duplex examination include measurement of aortic aneurysm sac size, assessment for endoleak, and evaluation of the endograft for patency and integrity. The duplex protocol for EVAR follow-up can be extended for follow-up after FEVAR, BEVAR, and F-BEVAR, with additional attention to the device components associated with fenestrations and branches. At the University of Washington, the physician-modified endovascular graft approach has been used for FEVAR. During these procedures, covered stents are placed in the renal arteries through fenestrations and the superior mesenteric artery is perfused through a fenestration, but typically remains unstented. Duplex scanning of the renal and mesenteric arteries has been performed preoperatively and at 30 days, 6 months, 1 year, and annually. In a review of patients having covered stents placed in non-stenotic renal arteries during FEVAR, both peak systolic velocity and the renal to aortic velocity ratio remained below the standard significant stenosis threshold in most patients. The duplex velocity criteria for stenosis in native renal arteries appeared to overestimate the severity of stenosis in renal artery covered stents. The unstented superior mesenteric artery remained widely patent in the presence of fenestrations or crossing struts and was not associated with endoleaks. Duplex ultrasound protocols for follow-up after FEVAR, BEVAR, and F-BEVAR can be based on those that have been established for standard EVAR, along with assessment of fenestrations and branches, as well as patency of the renal and mesenteric arteries.

Carotid duplex criteria: What have we learned in 40 years?

Before the development of the first prototype duplex ultrasound scanner at the University of Washington in the late 1970s, the only noninvasive tests available for extracranial carotid artery disease were indirect methods, such as the periorbital Doppler examination and oculoplethysmography. The duplex scanner combined real-time two-dimensional B-mode imaging and pulsed-Doppler flow detection in a single instrument and provided Doppler spectral waveforms from discrete sites within the vessel lumen. Spectral waveforms allowed characterization of the flow patterns and velocity changes associated with normal and diseased arteries. In a series of validation studies, Dr. D. Eugene Strandness, Jr. and colleagues compared various spectral waveform parameters obtained from internal carotid arteries to independently read carotid arteriograms and established quantitative threshold criteria for classification of carotid artery disease. These criteria were based on peak systolic velocity and end-diastolic velocity, as well as features such as spectral broadening and flow separation. Internal carotid arteries were classified as normal, 1% to 15% diameter reduction, 16% to 49% diameter reduction, 50% to 79% diameter reduction, 80% to 99% diameter reduction, and occluded. Since the 1980s, the University of Washington carotid duplex criteria have been widely used and modified in vascular laboratories throughout the world. Additional clinically relevant criteria have also been developed, such as a threshold for the 70% to 99% North American Symptomatic Carotid Endarterectomy Trial (NASCET) stenosis. Validation of carotid criteria has always depended on comparing spectral waveform parameters to the "gold standard" of contrast arteriography. However, experience has shown that the relationship between velocity and arteriographic stenosis is subject to significant variability. Based on these observations, standardization of carotid duplex criteria should lead to more consistent reporting among vascular laboratories, but it is unlikely to result in improved correlation with arteriography.

Effectiveness of bedside investigations to diagnose peripheral artery disease among people with diabetes mellitus: A systematic review

The accurate identification of peripheral artery disease (PAD) in patients with diabetes and foot ulceration is important, in order to inform timely management and to plan intervention including revascularisation. A variety of non-invasive tests are available to diagnose PAD at the bedside, but there is no consensus as to the most useful test, or the accuracy of these bedside investigations when compared to reference imaging tests such as magnetic resonance angiography, computed tomography angiography, digital subtraction angiography or colour duplex ultrasound. Members of the International Working Group of the Diabetic Foot updated our previous systematic review, to include all eligible studies published between 1980 and 2018. Some 15 380 titles were screened, resulting in 15 eligible studies (comprising 1563 patients, of which >80% in each study had diabetes) that evaluated an index bedside test for PAD against a reference imaging test. The primary endpoints were positive likelihood ratio (PLR) and negative likelihood ratio (NLR). We found that the most commonly evaluated test parameter was ankle brachial index (ABI) <0.9, which may be useful to suggest the presence of PAD (PLR 6.5) but an ABI value between 0.9 and 1.3 does not rule out PAD (NLR 0.31). A toe brachial index >0.75 makes the diagnosis of PAD less likely (NLR 0.14-0.24), whereas pulse oximetry may be used to suggest the presence of PAD (if toe saturation < 2% lower than finger saturation; PLR 17.23-30) or render PAD less likely (NLR 0.2-0.27). We found that the presence of triphasic tibial waveforms has the best performance value for excluding a diagnosis of PAD (NLR 0.09-0.28), but was evaluated in only two studies. In addition, we found that beside clinical examination (including palpation of foot pulses) cannot reliably exclude PAD (NLR 0.75), as evaluated in one study. Overall, the quality of data is generally poor and there is insufficient evidence to recommend one bedside test over another. While there have been six additional publications in the last 4 years that met our inclusion criteria, more robust evidence is required to achieve consensus on the most useful non-invasive bedside test to diagnose PAD.

Performance of prognostic markers in the prediction of wound healing or amputation among patients with foot ulcers in diabetes: A systematic review

Clinical outcomes of patients with diabetes, foot ulceration, and peripheral artery disease (PAD) are difficult to predict. The prediction of important clinical outcomes, such as wound healing and major amputation, would be a valuable tool to help guide management and target interventions for limb salvage. Despite the existence of a number of classification tools, no consensus exists as to the most useful bedside tests with which to predict outcome. We here present an updated systematic review from the International Working Group of the Diabetic Foot, comprising 15 studies published between 1980 and 2018 describing almost 6800 patients with diabetes and foot ulceration. Clinical examination findings as well as six non-invasive bedside tests were evaluated for their ability to predict wound healing and amputation. The most useful tests to inform on the probability of healing were skin perfusion pressure ≥ 40 mmHg, toe pressure ≥ 30 mmHg, or TcPO₂  ≥ 25 mmHg. With these thresholds, all of these tests increased the probability of healing by greater than 25% in at least one study. To predict major amputation, the most useful tests were ankle pressure < 50 mmHg, ABI < 0.5, toe pressure < 30 mmHg, and TcPO₂  < 25 mmHg, which increased the probability of major amputation by greater than 25%. These indicative values may be used as a guide when deciding which patients are at highest risk for poor outcomes and should therefore be evaluated for revascularization at an early stage. However, this should always be considered within the wider context of important co-existing factors such as infection, wound characteristics, and other comorbidities.

Guidelines on diagnosis, prognosis, and management of peripheral artery disease in patients with foot ulcers and diabetes (IWGDF 2019 update)

The International Working Group on the Diabetic Foot (IWGDF) has published evidence-based guidelines on the prevention and management of diabetic foot disease since 1999. This guideline is on the diagnosis, prognosis, and management of peripheral artery disease (PAD) in patients with foot ulcers and diabetes and updates the previous IWGDF Guideline. Up to 50% of patients with diabetes and foot ulceration have concurrent PAD, which confers a significantly elevated risk of adverse limb events and cardiovascular disease. We know that the diagnosis, prognosis, and treatment of these patients are markedly different to patients with diabetes who do not have PAD and yet there are few good quality studies addressing this important subset of patients. We followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology to devise clinical questions and critically important outcomes in the patient-intervention-comparison-outcome (PICO) format, to conduct a systematic review of the medical-scientific literature, and to write recommendations and their rationale. The recommendations are based on the quality of evidence found in the systematic review, expert opinion where evidence was not available, and a weighing of the benefits and harms, patient preferences, feasibility and applicability, and costs related to the intervention. We here present the updated 2019 guidelines on diagnosis, prognosis, and management of PAD in patients with a foot ulcer and diabetes, and we suggest some key future topics of particular research interest.

Effectiveness of revascularisation of the ulcerated foot in patients with diabetes and peripheral artery disease: A systematic review

In patients with diabetes, foot ulceration and peripheral artery disease (PAD), it is often difficult to determine whether, when and how to revascularise the affected lower extremity. The presence of PAD is a major risk factor for non-healing and yet clinical outcomes of revascularisation are not necessarily related to technical success. The International Working Group of the Diabetic Foot updated systematic review on the effectiveness of revascularisation of the ulcerated foot in patients with diabetes and PAD is comprised of 64 studies describing >13 000 patients. Amongst 60 case series and 4 non-randomised controlled studies, we summarised clinically relevant outcomes and found them to be broadly similar between patients treated with open vs endovascular therapy. Following endovascular revascularisation, the 1 year and 2 year limb salvage rates were 80% (IQR 78-82%) and 78% (IQR 75-83%), whereas open therapy was associated with rates of 85% (IQR 80-90%) at 1 year and 87% (IQR 85-88%) at 2 years, however these results were based on a varying combination of studies and cannot therefore be interpreted as cumulative. Overall, wound healing was achieved in a median of 60% of patients (IQR 50-69%) at 1 year in those treated by endovascular or surgical therapy, and the major amputation rate of endovascular vs open therapy was 2% vs 5% at 30 days, 10% vs 9% at 1 year and 13% vs 9% at 2 years. For both strategies, overall mortality was found to be high, with 2% (1-6%) perioperative (or 30 day) mortality, rising sharply to 13% (9-23%) at 1 year, 29% (19-48%) at 2 years and 47% (39-71%) at 5 years. Both the angiosome concept (revascularisation directly to the area of tissue loss via its main feeding artery) or indirect revascularisation through collaterals, appear to be equally effective strategies for restoring perfusion. Overall, the available data do not allow us to recommend one method of revascularisation over the other and more studies are required to determine the best revascularisation approach in diabetic foot ulceration.

Analysis of Factors Influencing Accuracy of Volume Flow Measurement in Dialysis Access Fistulas Based on Duplex Ultrasound Simulation

OBJECTIVE

We developed a duplex ultrasound simulator and used it to assess accuracy of volume flow measurements in dialysis access fistula (DAF) models.

METHODS

The simulator consists of a mannequin, computer, and mock transducer. Each case is built from a patient's B-mode images that are used to create a 3-dimensional surface model of the DAF. Computational fluid dynamics is used to determine blood flow velocities based on model vessel geometry. The simulator displays real-time B-mode and color-flow images, and Doppler spectral waveforms are generated according to user-defined settings. Accuracy was assessed by scanning each case and measuring volume flow in the inflow artery and outflow vein for comparison with true volume flow values.

RESULTS

Four examiners made 96 volume flow measurements on four DAF models. Measured volume flow deviated from the true value by 35 ± 36%. Mean absolute deviation from true volume flow was lower for arteries than veins (22 ± 19%, N = 48 vs. 58 ± 33%, N = 48, p < 0.0001). This finding is attributed to eccentricity of outflow veins which resulted in underestimating true cross-sectional area. Regression analysis indicated that error in measuring cross-sectional area was a predictor of error in volume flow measurement (β = 0.948, p < 0.001). Volume flow error was reduced from 35 ± 36% to 9 ± 8% (p < 0.000001) by calculating vessel area as an ellipse.

CONCLUSIONS

Duplex volume flow measurements are based on a circular vessel shape. DAF inflow arteries are circular, but outflow veins can be elliptical. Simulation-based analysis showed that error in measuring volume flow is mainly due to assumption of a circular vessel.

Formative Assessment of Performance in Diagnostic Ultrasound Using Simulation and Quantitative and Objective Metrics

BACKGROUND

We developed simulator-based tools for assessing provider competence in transthoracic echocardiography (TTE) and vascular duplex scanning.

METHODS

Psychomotor (technical) skill in TTE image acquisition was calculated from the deviation angle of an acquired image from the anatomically correct view. We applied this metric for formative assessment to give feedback to learners and evaluate curricula.Psychomotor skill in vascular ultrasound was measured in terms of dexterity and image plane location; cognitive skill was assessed from measurements of blood flow velocity, parameter settings, and diagnosis. The validity of the vascular simulator was assessed from the accuracy with which experts can measure peak systolic blood flow velocity (PSV).

RESULTS

In the TTE simulator, the skill metric enabled immediate feedback, formative assessment of curriculum efficacy, and comparison of curriculum outcomes. The vascular duplex ultrasound simulator also provided feedback, and experts' measurements of PSV deviated from actual PSV in the model by <10%.

CONCLUSIONS

Skill in acquiring diagnostic ultrasound images of organs and vessels can be measured using simulation in an objective, quantitative, and standardized manner. Current applications are provision of feedback to learners to enable training without direct faculty oversight and formative assessment of curricula. Simulator-based metrics could also be applied for summative assessment.

Evaluation of Examiner Performance Using a Duplex Ultrasound Simulator. Flow Velocity Measurements in Dialysis Access Fistula Models

We developed a duplex ultrasound simulator for training and assessment of scanning skills. We used the simulator to test examiner performance in the measurement of flow velocities in dialysis access fistulas. Test cases were created from 3-D ultrasound scans of two dialysis access fistulas by reconstructing 3-D blood vessel models and simulating blood flow velocity fields within the lumens. The simulator displays a 2-D B-mode or color Doppler image corresponding to transducer position on a mannequin; a spectral waveform is generated according to Doppler sample volume location and system settings. Examiner performance was assessed by comparing the measured peak systolic velocity (PSV) with the true PSV provided by the computational flow model. The PSV measured by four expert examiners deviated from the true value by 7.8 ± 6.1%. The results indicate the ability of the simulator to objectively assess an examiner's measurement accuracy in complex vascular targets.

The Society for Vascular Surgery practice guidelines on follow-up after vascular surgery arterial procedures

Although follow-up after open surgical and endovascular procedures is generally regarded as an important part of the care provided by vascular surgeons, there are no detailed or comprehensive guidelines that specify the optimal approaches with regard to testing methods, indications for reintervention, and follow-up intervals. To provide guidance to the vascular surgeon, the Clinical Practice Council of the Society for Vascular Surgery appointed an expert panel and a methodologist to review the current clinical evidence and to develop recommendations for follow-up after vascular surgery procedures. For those procedures for which high-quality evidence was not available, recommendations were based on observational studies, committee consensus, and indirect evidence. Recognizing that there are numerous published reports on the role of duplex ultrasound for surveillance of infrainguinal vein bypass grafts, the Society commissioned a systematic review and meta-analysis on this topic. The panel classified the strength of each recommendation and the corresponding quality of evidence on the basis of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system: recommendations were graded either strong or weak, and the quality of evidence was graded high, moderate, or low. The resulting recommendations represent a wide variety of open surgical and endovascular procedures involving the extracranial carotid artery, thoracic and abdominal aorta, mesenteric and renal arteries, and lower extremity arterial revascularization. The panel also identified many areas in which there was a lack of high-quality evidence to support their recommendations. This suggests that there are opportunities for further clinical research on testing methods, threshold criteria, and the role of surveillance as well as on the modes of failure and indications for reintervention after vascular surgery procedures.

Simulation for competency assessment in vascular and cardiac ultrasound

Healthcare providers who use peripheral vascular and cardiac ultrasound require specialized training to develop the technical and interpretive skills necessary to perform accurate diagnostic tests. Assessment of competence is a critical component of training that documents a learner's progress and is a requirement for competency-based medical education (CBME) as well as specialty certification or credentialing. The use of simulation for CBME in diagnostic ultrasound is particularly appealing since it incorporates both the psychomotor and cognitive domains while eliminating dependency on the availability of live patients with a range of pathology. However, successful application of simulation in this setting requires realistic, full-featured simulators and appropriate standardized metrics for competency testing. The principal diagnostic parameter in peripheral vascular ultrasound is measurement of peak systolic velocity (PSV) on Doppler spectral waveforms, and simulation of Doppler flow detection presents unique challenges. The computer-based duplex ultrasound simulator developed at the University of Washington uses computational fluid dynamics modeling and presents real-time color-flow Doppler images and Doppler spectral waveforms along with the corresponding B-mode images. This simulator provides a realistic scanning experience that includes measuring PSV in various arterial segments and applying actual diagnostic criteria. Simulators for echocardiography have been available since the 1990s and are currently more advanced than those for peripheral vascular ultrasound. Echocardiography simulators are now offered for both transesophageal echo and transthoracic echo. These computer-based simulators have 3D graphic displays that provide feedback to the learner and metrics for assessment of technical skill that are based on transducer tracking data. Such metrics provide a motion-based or kinematic analysis of skill in performing cardiac ultrasound. The use of simulation in peripheral vascular and cardiac ultrasound can provide a standardized and readily available method for training and competency assessment.

Can preeclampsia be considered a renal compartment syndrome? A hypothesis and analysis of the literature

The morbidity and mortality associated with preeclampsia is staggering. The physiology of the Page kidney, a condition in which increased intrarenal pressure causes hypertension, appears to provide a unifying framework to explain the complex pathophysiology. Page kidney hypertension is renin-mediated acutely and ischemia-mediated chronically. Renal venous outflow obstruction also causes a Page kidney phenomenon, providing a hypothesis for the increased vulnerability of a subset of women who have what we are hypothesizing is a "renal compartment syndrome" due to inadequate ipsilateral collateral renal venous circulation consistent with well-known variation in normal venous anatomy. Dynamic changes in renal venous anatomy and physiology in pregnancy appear to correlate with disease onset, severity, and recurrence. Since maternal recumbent position is well known to affect renal perfusion and since chronic outflow obstruction makes women vulnerable to the ischemic/inflammatory sequelae, heightened awareness of renal compartment syndrome physiology is critical. The anatomic and physiologic insights provide immediate strategies to predict and prevent preeclampsia with straightforward, low-cost interventions that make renewed global advocacy for pregnant women a realistic goal.

Development of a Duplex Ultrasound Simulator and Preliminary Validation of Velocity Measurements in Carotid Artery Models

OBJECTIVE

Duplex ultrasound scanning with B-mode imaging and both color Doppler and Doppler spectral waveforms is relied upon for diagnosis of vascular pathology and selection of patients for further evaluation and treatment. In most duplex ultrasound applications, classification of disease severity is based primarily on alterations in blood flow velocities, particularly the peak systolic velocity (PSV) obtained from Doppler spectral waveforms. We developed a duplex ultrasound simulator for training and assessment of scanning skills.

METHODS

Duplex ultrasound cases were prepared from 2-dimensional (2D) images of normal and stenotic carotid arteries by reconstructing the common carotid, internal carotid, and external carotid arteries in 3 dimensions and computationally simulating blood flow velocity fields within the lumen. The simulator displays a 2D B-mode image corresponding to transducer position on a mannequin, overlaid by color coding of velocity data. A spectral waveform is generated according to examiner-defined settings (depth and size of the Doppler sample volume, beam steering, Doppler beam angle, and pulse repetition frequency or scale). The accuracy of the simulator was assessed by comparing the PSV measured from the spectral waveforms with the true PSV which was derived from the computational flow model based on the size and location of the sample volume within the artery.

RESULTS

Three expert examiners made a total of 36 carotid artery PSV measurements based on the simulated cases. The PSV measured by the examiners deviated from true PSV by 8% ± 5% (N = 36). The deviation in PSV did not differ significantly between artery segments, normal and stenotic arteries, or examiners.

CONCLUSION

To our knowledge, this is the first simulation of duplex ultrasound that can create and display real-time color Doppler images and Doppler spectral waveforms. The results demonstrate that an examiner can measure PSV from the spectral waveforms using the settings on the simulator with a mean absolute error in the velocity measurement of less than 10%. With the addition of cases with a range of pathologies, this duplex ultrasound simulator will be a useful tool for training health-care providers in vascular ultrasound applications and for assessing their skills in an objective and quantitative manner.

Performance of prognostic markers in the prediction of wound healing or amputation among patients with foot ulcers in diabetes: a systematic review

Prediction of wound healing and major amputation in patients with diabetic foot ulceration is clinically important to stratify risk and target interventions for limb salvage. No consensus exists as to which measure of peripheral artery disease (PAD) can best predict outcomes. To evaluate the prognostic utility of index PAD measures for the prediction of healing and/or major amputation among patients with active diabetic foot ulceration, two reviewers independently screened potential studies for inclusion. Two further reviewers independently extracted study data and performed an assessment of methodological quality using the Quality in Prognostic Studies instrument. Of 9476 citations reviewed, 11 studies reporting on 9 markers of PAD met the inclusion criteria. Annualized healing rates varied from 18% to 61%; corresponding major amputation rates varied from 3% to 19%. Among 10 studies, skin perfusion pressure ≥ 40 mmHg, toe pressure ≥ 30 mmHg (and ≥ 45 mmHg) and transcutaneous pressure of oxygen (TcPO2 ) ≥ 25 mmHg were associated with at least a 25% higher chance of healing. Four studies evaluated PAD measures for predicting major amputation. Ankle pressure < 70 mmHg and fluorescein toe slope < 18 units each increased the likelihood of major amputation by around 25%. The combined test of ankle pressure < 50 mmHg or an ankle brachial index (ABI) < 0.5 increased the likelihood of major amputation by approximately 40%. Among patients with diabetic foot ulceration, the measurement of skin perfusion pressures, toe pressures and TcPO2 appear to be more useful in predicting ulcer healing than ankle pressures or the ABI. Conversely, an ankle pressure of < 50 mmHg or an ABI < 0.5 is associated with a significant increase in the incidence of major amputation.

Effectiveness of revascularization of the ulcerated foot in patients with diabetes and peripheral artery disease: a systematic review

Symptoms or signs of peripheral artery disease (PAD) can be observed in up to 50% of the patients with a diabetic foot ulcer and is a risk factor for poor healing and amputation. In 2012, a multidisciplinary working group of the International Working Group on the Diabetic Foot published a systematic review on the effectiveness of revascularization of the ulcerated foot in patients with diabetes and PAD. This publication is an update of this review and now includes the results of a systematic search for therapies to revascularize the ulcerated foot in patients with diabetes and PAD from 1980 to June 2014. Only clinically relevant outcomes were assessed. The research conformed to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, and Scottish Intercollegiate Guidelines Network methodological scores were assigned. A total of 56 articles were eligible for full-text review. There were no randomized controlled trials, but there were four nonrandomized studies with a control group. The major outcomes following endovascular or open bypass surgery were broadly similar among the studies. Following open surgery, the 1-year limb salvage rates were a median of 85% (interquartile range of 80-90%), and following endovascular revascularization, these rates were 78% (70-89%). At 1-year follow-up, 60% or more of ulcers had healed following revascularization with either open bypass surgery or endovascular techniques. Studies appeared to demonstrate improved rates of limb salvage associated with revascularization compared with the results of conservatively treated patients in the literature. There were insufficient data to recommend one method of revascularization over another. There is a real need for standardized reporting of baseline demographic data, severity of disease and outcome reporting in this group of patients.

Effectiveness of bedside investigations to diagnose peripheral artery disease among people with diabetes mellitus: a systematic review

Non-invasive tests for the detection of peripheral artery disease (PAD) among individuals with diabetes mellitus are important to estimate the risk of amputation, ulceration, wound healing and the presence of cardiovascular disease, yet there are no consensus recommendations to support a particular diagnostic modality over another and to evaluate the performance of index non-invasive diagnostic tests against reference standard imaging techniques (magnetic resonance angiography, computed tomography angiography, digital subtraction angiography and colour duplex ultrasound) for the detection of PAD among patients with diabetes. Two reviewers independently screened potential studies for inclusion and extracted study data. Eligible studies evaluated an index test for PAD against a reference test. An assessment of methodological quality was performed using the quality assessment for diagnostic accuracy studies instrument. Of the 6629 studies identified, ten met the criteria for inclusion. In these studies, the patients had a median age of 60-74 years and a median duration of diabetes of 9-24 years. Two studies reported exclusively on patients with symptomatic (ulcerated/infected) feet, two on patients with asymptomatic (intact) feet only, and the remaining six on patients both with and without foot ulceration. Ankle brachial index (ABI) was the most widely assessed index test. Overall, the positive likelihood ratio and negative likelihood ratio (NLR) of an ABI threshold <0.9 ranged from 2 to 25 (median 8) and <0.1 to 0.7 (median 0.3), respectively. In patients with neuropathy, the NLR of the ABI was generally higher (two out of three studies), indicating poorer performance, and ranged between 0.3 and 0.5. A toe brachial index <0.75 was associated with a median positive likelihood ratio and NLRs of 3 and ≤ 0.1, respectively, and was less affected by neuropathy in one study. Also, in two separate studies, pulse oximetry used to measure the oxygen saturation of peripheral blood and Doppler wave form analyses had NLRs of 0.2 and <0.1. The reported performance of ABI for the diagnosis of PAD in patients with diabetes mellitus is variable and is adversely affected by the presence of neuropathy. Limited evidence suggests that toe brachial index, pulse oximetry and wave form analysis may be superior to ABI for diagnosing PAD in patients with neuropathy with and without foot ulcers. There were insufficient data to support the adoption of one particular diagnostic modality over another and no comparisons existed with clinical examination. The quality of studies evaluating diagnostic techniques for the detection of PAD in individuals with diabetes is poor. Improved compliance with guidelines for methodological quality is needed in future studies.

Incomplete restoration of homeostatic shear stress within arteriovenous fistulae

Arteriovenous fistulae are surgically created to provide adequate access for dialysis patients suffering from end-stage renal disease. It has long been hypothesized that the rapid blood vessel remodeling occurring after fistula creation is, in part, a process to restore the mechanical stresses to some preferred level, i.e., mechanical homeostasis. We present computational hemodynamic simulations in four patient-specific models of mature arteriovenous fistulae reconstructed from 3D ultrasound scans. Our results suggest that these mature fistulae have remodeled to return to ''normal'' shear stresses away from the anastomoses: about 1.0 Pa in the outflow veins and about 2.5 Pa in the inflow arteries. Large parts of the anastomoses were found to be under very high shear stresses >15 Pa, over most of the cardiac cycle. These results suggest that the remodeling process works toward restoring mechanical homeostasis in the fistulae, but that the process is limited or incomplete, even in mature fistulae, as evidenced by the elevated shear at or near the anastomoses. Based on the long term clinical viability of these dialysis accesses, we hypothesize that the elevated nonhomeostatic shear stresses in some portions of the vessels were not detrimental to fistula patency.

Agreement between site-reported and ultrasound core laboratory results for duplex ultrasound velocity measurements in the Carotid Revascularization Endarterectomy versus Stenting Trial

OBJECTIVE

Patients in the Carotid Revascularization Endarterectomy vs Stenting Trial (CREST) had duplex ultrasound (DU) scans prior to treatment and during follow-up to document the severity of carotid disease and the anatomic outcome of carotid endarterectomy (CEA) or carotid artery stenting (CAS). An ultrasound core laboratory (UCL) reviewed DU data from the clinical sites. This analysis was done to determine the agreement between site-reported and UCL-verified DU velocity measurements.

METHODS

Clinical site DU worksheets, B-mode images, and Doppler velocity waveforms for the treated carotid arteries were reviewed at the UCL. The highest internal carotid artery peak systolic velocity (PSV) and associated Doppler angle were verified. If the angle was misaligned by >3 degrees, it was remeasured at the UCL and the PSV was recalculated. Agreement for PSV was defined as site-reported PSV within ± 5% of UCL-verified PSV. Transcription errors were corrected by the UCL but were not considered as disagreements. Follow-up analysis was limited to patients who received the assigned treatment.

RESULTS

The UCL reviewed 1702 prior-to-treatment and 1743 12-month follow-up DU scans (873 CEA, 870 CAS) from 111 clinical sites. Site-reported and UCL-verified PSV agreed in 1124 (66%) of the prior-to-treatment scans and 1200 (69%) of the follow-up scans. In those cases with a disagreement, Doppler angle accounted for disagreement in 339 (59%) of the prior-to-treatment scans and 277 (51%) of the follow-up scans. Based on a threshold PSV for ≥ 70% stenosis of ≥ 230 cm/s on the prior-to-treatment scans and ≥ 300 cm/s on the follow-up scans, UCL review resulted in reclassification of stenosis severity in 75 (4.4%) of the prior-to-treatment scans and 13 (0.75%) of the follow-up scans. There is evidence that the proportion of reclassification at follow-up was greater for CAS (10 scans; 1.2%) than for CEA (three scans; 0.34%) (P = .057).

CONCLUSIONS

There was a high rate of agreement between site-reported and UCL-verified DU results in CREST, and UCL review was associated with a low rate of stenosis reclassification. However, angle alignment errors were quite common and prompted recalculation of velocity in 20% of prior-to-treatment scans and 18% of follow-up scans. The use of a UCL provides a uniform process for DU interpretation and can identify sources of error and suggest technical improvements for future studies.

Hemodynamic conditions in a failing peripheral artery bypass graft

OBJECTIVE

The mechanisms of restenosis in autogenous vein bypass grafts placed for peripheral artery disease are not completely understood. We investigated the role of hemodynamic stress in a case study of a revised bypass graft that failed due to restenosis.

METHODS

The morphology of the lumen was reconstructed from a custom three-dimensional ultrasound system. Scans were taken at 1, 6, and 16 months after a patch angioplasty procedure. Computational hemodynamic simulations of the patient-specific model provided the blood flow features and the hemodynamic stresses on the vessel wall at the three times studied.

RESULTS

The vessel was initially free of any detectable lesions, but a 60% diameter-reducing stenosis developed during the 16-month study interval. As determined from the simulations, chaotic and recirculating flow occurred downstream of the stenosis due to the sudden widening of the lumen at the patch location. Curvature and a sudden increase in the lumen cross-sectional area induced these flow features that are hypothesized to be conducive to intimal hyperplasia. Favorable agreement was found between simulation results and in vivo Doppler ultrasound velocity measurements.

CONCLUSIONS

Transitional and chaotic flow occurs at the site of the revision, inducing a complex pattern of wall shear as computed with the hemodynamic simulations. This supports the hypothesis that the hemodynamic stresses in the revised segment, produced by the coupling of vessel geometry and chaotic flow, led to the intimal hyperplasia and restenosis of the graft.

Carotid Doppler velocity measurements and anatomic stenosis: correlation is futile

BACKGROUND

Duplex ultrasound with Doppler velocimetry is widely used to evaluate the presence and severity of internal carotid artery stenosis; however, a variety of velocity criteria are currently being applied to classify stenosis severity. The purpose of this study is to compare published Doppler velocity measurements to the severity of internal carotid artery stenosis as assessed by x-ray angiography in order to clarify the relationship between these 2 widely used approaches to assess carotid artery disease.

METHODS

Scatter diagrams or "scattergrams" of correlations between Doppler velocity measurements and stenosis severity as assessed by x-ray contrast angiography were obtained from published articles for native and stented internal carotid arteries. The scattergrams were graphically digitized, combined, and segmented into categories bounded by 50% and 70% diameter reduction. These data were combined and divided into 3 sets representing different velocity parameters: (1) peak systolic velocity, (2) end-diastolic velocity, and (3) the internal carotid artery to common carotid artery peak systolic velocity ratio. The horizontal axis of each scattergram was transformed to form a cumulative distribution function, and thresholds were established for the stenosis categories to assess data variability.

RESULTS

Nineteen publications with 22 data sets were identified and included in this analysis. Wide variability was apparent between all 3 velocity parameters and angiographic percent stenosis. The optimal peak systolic velocity thresholds for stenosis in stented carotid arteries were higher than those for native carotid arteries. Within each category of stenosis, the variability of all 3 velocity parameters was significantly lower in stented arteries than in native arteries.

CONCLUSION

Although Doppler velocity criteria have been successfully used to classify the severity of stenosis in both native and stented carotid arteries, the relationship to angiographic stenosis contains significant variability. This analysis of published studies suggests that further refinements in Doppler velocity criteria will not lead to improved correlation with carotid stenosis as demonstrated by angiography.

The Risk Factors and Clinical Outcomes of Upper Extremity Deep Vein Thrombosis

The prevalence of upper extremity deep vein thrombosis (UEDVT) has shown a dramatic increase with the use of central venous catheters (CVCs) for patient care. The objective of this study was to identify risk factors and clinical outcomes in patients diagnosed with UEDVT at an academic medical center over a 1-year period. Medical records of 373 consecutive patients who underwent upper extremity venous duplex ultrasound (VDU) examination were retrospectively reviewed. A quarter of the patients screened by VDU (94 of 373) had acute UEDVT; 63% presented with arm swelling or arm pain; 48% had cancer; and 93% had indwelling CVCs. Cancer patients with CVCs were more likely to develop UEDVT (48%). Of the 94 UEDVTs, 16% had concurrent lower extremity DVT. The incidence of objectively confirmed pulmonary embolism (PE) was 9% (8 of 94 patients), and the 1-month mortality rate was 6.4%. The majority of patients (80%) with UEDVT received anticoagulation therapy and 20% were not treated. The most common risk factors for UEDVT were indwelling CVCs and a diagnosis of cancer. The incidence rate of PE and mortality rate from UEDVT were not insignificant at 9% and 6%, respectively. There were no institutional screening protocols for patients at risk of UEDVT associated with CVCs. Future research should focus on risk assessment and management protocols for patients at risk of UEDVT. In addition, a comparison of clinical outcomes associated with the type, size, and duration of catheter placement should be conducted in patients at risk of or diagnosed with UEDVT.

Diagnosis and treatment of peripheral arterial disease in diabetic patients with a foot ulcer. A progress report of the International Working Group on the Diabetic Foot

The International Working Group on the Diabetic Foot (IWDGF) has produced in 2011 a guideline on the diagnosis and treatment of peripheral arterial disease in patients with diabetes and a foot ulcer. This document, together with a systematic review that provided the background information on management, was produced by a multidisciplinary working group of experts in the field and was endorsed by the IWDGF. This progress report is based on these two documents and earlier consensus texts of the IWDGF on the diagnosis and management of diabetic foot ulcers. Its aim is to give the clinician clear guidance on when and how to diagnose peripheral arterial disease in patients with diabetes and a foot ulcer and when and which treatment modalities should be considered, taking both risks and benefits into account.

A systematic review of the effectiveness of revascularization of the ulcerated foot in patients with diabetes and peripheral arterial disease

In several large recent observational studies, peripheral arterial disease (PAD) was present in up to 50% of the patients with a diabetic foot ulcer and was an independent risk factor for amputation. The International Working Group on the Diabetic Foot therefore established a multidisciplinary working group to evaluate the effectiveness of revascularization of the ulcerated foot in patients with diabetes and PAD. A systematic search was performed for therapies to revascularize the ulcerated foot in patients with diabetes and PAD from 1980-June 2010. Only clinically relevant outcomes were assessed. The research conformed to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, and the Scottish Intercollegiate Guidelines Network methodological scores were assigned. A total of 49 papers were eligible for full text review. There were no randomized controlled trials, but there were three nonrandomized studies with a control group. The major outcomes following endovascular or open bypass surgery were broadly similar among the studies. Following open surgery, the 1-year limb salvage rates were a median of 85% (interquartile range of 80-90%), and following endovascular revascularization, these rates were 78% (70.5-85.5%). At 1-year follow-up, 60% or more of ulcers had healed following revascularization with either open bypass surgery or endovascular revascularization. Studies appeared to demonstrate improved rates of limb salvage associated with revascularization compared with the results of medically treated patients in the literature. There were insufficient data to recommend one method of revascularization over another. There is a real need for standardized reporting of baseline demographic data, severity of disease and outcome reporting in this group of patients.

Standardized ultrasound evaluation of carotid stenosis for clinical trials: University of Washington Ultrasound Reading Center

Introduction

Serial monitoring of patients participating in clinical trials of carotid artery therapy requires noninvasive precision methods that are inexpensive, safe and widely available. Noninvasive ultrasonic duplex Doppler velocimetry provides a precision method that can be used for recruitment qualification, pre-treatment classification and post treatment surveillance for remodeling and restenosis. The University of Washington Ultrasound Reading Center (UWURC) provides a uniform examination protocol and interpretation of duplex Doppler velocity measurements.

Methods

Doppler waveforms from 6 locations along the common carotid and internal carotid artery path to the brain plus the external carotid and vertebral arteries on each side using a Doppler examination angle of 60 degrees are evaluated. The UWURC verifies all measurements against the images and waveforms for the database, which includes pre-procedure, post-procedure and annual follow-up examinations. Doppler angle alignment errors greater than 3 degrees and Doppler velocity measurement errors greater than 0.05 m/s are corrected.

Results

Angle adjusted Doppler velocity measurements produce higher values when higher Doppler examination angles are used. The definition of peak systolic velocity varies between examiners when spectral broadening due to turbulence is present. Examples of measurements are shown.

Discussion

Although ultrasonic duplex Doppler methods are widely used in carotid artery diagnosis, there is disagreement about how the examinations should be performed and how the results should be validated. In clinical trails, a centralized reading center can unify the methods. Because the goals of research examinations are different from those of clinical examinations, screening and diagnostic clinical examinations may require fewer velocity measurements.