Prospective evaluation of new duplex criteria to identify 70% internal carotid artery stenosis

Accuracy of the Society of Radiologists in Ultrasound (SRU) Carotid Doppler Velocity Criteria for Grading North American Symptomatic Carotid Endarterectomy Trial (NASCET) Stenosis: A Meta-Analysis

PURPOSE

The Society of Radiologists in Ultrasound (SRU) consensus panel proposed six Doppler velocity cut points for classifying internal carotid artery (ICA) stenosis of 50% and 70% according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method. Their relative accuracies have not been compared.

MATERIALS AND METHODS

Meta-analysis performed following comprehensive literature review and identification of manuscripts with graphs of individual patient NASCET ICA stenosis measured by arteriography versus ICA peak-systolic velocity (PSV), end-diastolic velocity (EDV) and ICA PSV to common carotid artery (CCA) PSV. True positives, true negatives, false positives, and false negatives were calculated and used in two-level mixed effects models. Hierarchical summary receiver operating characteristic (ROC) curves were generated. Areas under the ROC curves were estimated.

RESULTS

Nine studies performed between 1993 and 2016 were identified after review of 337 manuscripts. There were 1738 bifurcation data points extracted for PSV, 1026 for EDV, and 775 for ICA/CCA ratio. The highest sensitivity was 96% (95% CI: 93%, 98%) for PSV of 125 cm/s (50% stenosis) and highest specificity 86% (95% CI: 71%, 93%) for PSV of 230 cm/s (70% stenosis). Areas under the ROC curves ranged from a high of 0.93 (95% CI: 0.92, 0.95) for PSV (50% stenosis) to a low of 0.86 (95% CI: 0.84, 0.88) for EDV (70% stenosis).

CONCLUSIONS

The SRU consensus Doppler cut points vary in their accuracies for predicting ICA stenosis. The PSV cut points have tradeoffs: high sensitivity/low specificity for 50% stenosis and high specificity/moderate sensitivity for 70% stenosis.

Atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia despite substantial efforts to understand the pathophysiology of the condition and develop improved treatments. Identifying the underlying causative mechanisms of AF in individual patients is difficult and the efficacy of current therapies is suboptimal. Consequently, the incidence of AF is steadily rising and there is a pressing need for novel therapies. Research has revealed that defects in specific molecular pathways underlie AF pathogenesis, resulting in electrical conduction disorders that drive AF. The severity of this so-called electropathology correlates with the stage of AF disease progression and determines the response to AF treatment. Therefore, unravelling the molecular mechanisms underlying electropathology is expected to fuel the development of innovative personalized diagnostic tools and mechanism-based therapies. Moreover, the co-creation of AF studies with patients to implement novel diagnostic tools and therapies is a prerequisite for successful personalized AF management. Currently, various treatment modalities targeting AF-related electropathology, including lifestyle changes, pharmaceutical and nutraceutical therapy, substrate-based ablative therapy, and neuromodulation, are available to maintain sinus rhythm and might offer a novel holistic strategy to treat AF.

Optimization of duplex velocity criteria for diagnosis of internal carotid artery (ICA) stenosis: A report of the Intersocietal Accreditation Commission (IAC) Vascular Testing Division Carotid Diagnostic Criteria Committee

Diagnostic criteria to classify severity of internal carotid artery (ICA) stenosis vary across vascular laboratories. Consensus-based criteria, proposed by the Society of Radiologists in Ultrasound in 2003 (SRUCC), have been broadly implemented but have not been adequately validated. We conducted a multicentered, retrospective correlative imaging study of duplex ultrasound versus catheter angiography for evaluation of severity of ICA stenosis. Velocity data were abstracted from bilateral duplex studies performed between 1/1/2009 and 12/31/2015 and studies were interpreted using SRUCC. Percentage ICA stenosis was determined using North American Symptomatic Carotid Endarterectomy Trial (NASCET) methodology. Receiver operating characteristic analysis evaluated the performance of SRUCC parameters compared with angiography. Of 448 ICA sides (from 224 patients), 299 ICA sides (from 167 patients) were included. Agreement between duplex ultrasound and angiography was moderate (κ = 0.42), with overestimation of degree of stenosis for both moderate (50–69%) and severe (⩾ 70%) ICA lesions. The primary SRUCC parameter for ⩾ 50% ICA stenosis of peak-systolic velocity (PSV) of ⩾ 125 cm/sec did not meet prespecified thresholds for adequate sensitivity, specificity, and accuracy (sensitivity 97.8%, specificity 64.2%, accuracy 74.5%). Test performance was improved by raising the PSV threshold to ⩾ 180 cm/sec (sensitivity 93.3%, specificity 81.6%, accuracy 85.2%) or by adding the additional parameter of ICA/common carotid artery (CCA) PSV ratio ⩾ 2.0 (sensitivity 94.3%, specificity 84.3%, accuracy 87.4%). For ⩾ 70% ICA stenosis, analysis was limited by a low number of cases with angiographically severe disease. Interpretation of carotid duplex examinations using SRUCC resulted in significant overestimation of severity of ICA stenosis when compared with angiography; raising the PSV threshold for ⩾ 50% ICA stenosis to ⩾ 180 cm/sec as a single parameter or requiring the ICA/CCA PSV ratio ⩾ 2.0 in addition to PSV of ⩾ 125 cm/sec for laboratories using the SRUCC is recommended to improve the accuracy of carotid duplex examinations.

Ultrasonography for the diagnosis of extra-cranial carotid occlusion - diagnostic test accuracy meta-analysis

Background: The correct diagnosis of internal carotid artery (ICA) occlusion is crucial as it limits unnecessary intervention, whereas correct identification of patients with severe ICA stenosis is paramount in decision making and selecting patients who would benefit from intervention. We aimed to evaluate the accuracy of ultrasonography (US) in the diagnosis of ICA occlusion. Methods: We conducted a systematic review in compliance with the Preferred Reporting Items for a Systematic Review and Meta-analysis (PRISMA) of diagnostic test accuracy studies. We interrogated electronic bibliographic sources using a combination of free text and thesaurus terms to identify studies assessing the diagnostic accuracy of US in ICA occlusion. We used a mixed-effects logistic regression bivariate model to estimate summary sensitivity and specificity. We developed hierarchical summary receiver operating characteristic (HSROC) curves. Results: We identified 23 studies reporting a total of 5,675 arteries of which 722 were proven to be occluded by the reference standard. The reference standard was digital subtraction or cerebral angiography in all but two studies, which used surgery to ascertain a carotid occlusion. The pooled estimates for sensitivity and specificity were 0.97 (95% confidence interval (CI) 0.94 to 0.99) and 0.99 (95% CI 0.98 to 1.00), respectively. The diagnostic odds ratio was 3,846.15 (95% CI 1,375.74 to 10,752.65). The positive and negative likelihood ratio were 114.71 (95% CI 58.84 to 223.63) and 0.03 (95% CI 0.01 to 0.06), respectively. Conclusions: US is a reliable and accurate method in diagnosing ICA occlusion. US can be used as a screening tool with cross-sectional imaging being reserved for ambiguous cases.

Diagnostic criteria for the determination of clinically significant internal carotid artery stenosis using duplex ultrasound

BACKGROUND

Carotid endarterectomy is beneficial in symptomatic patients with ≥70% stenosis at the bifurcation of the internal carotid artery. The fact that the duplex ultrasound is widely used, inexpensive and non-invasive for examination of the carotid arteries underlines the importance of high accuracy of this method for grading internal artery stenosis.

PATIENTS AND METHODS

Duplex scans and arteriograms of carotid arteries of 142 patients were reviewed. Peak and end-diastolic velocities of the common and internal carotid arteries were recorded, and the percent stenosis of the internal carotid artery was determined by arteriogram. Receiver-operator characteristic curves of sensitivity, specificity, positive and negative predictive values and accuracy were determined.

RESULTS

The recommended criteria for the detection of ≥70% stenosis of the internal carotid artery were: peak systolic velocity in the internal carotid artery ≥215 cm/s, end-diastolic velocity in the internal carotid artery ≥65 cm/s, ratio of peak systolic velocities in the internal and common carotid arteries ≥2.7 and ratio of the end-diastolic velocities of the internal and common carotid arteries ≥3.7.

CONCLUSION

These criteria allow for reliable determination of internal carotid artery stenosis ≥70% by duplex ultrasound.

Carotid Endarterectomy Based on Duplex Ultrasonography: A Safe Approach Associated with Long-term Stroke Prevention

To evaluate the short-term and long-term safety of carotid endarterectomy (CEA) based on duplex ultrasound without confirmatory diagnostic arteriography.

A 4-year retrospective review of CEA based on duplex ultrasound alone (n = 653) or with confirmatory arteriography (n = 118) was performed in 244 women and 458 men whose ages ranged from 39 to 92 years (mean, 70 years). Practice patterns, perioperative morbidity, and stroke rate (life-table analysis) of a community-based and university- based vascular surgical practice were analyzed and compared.

Surgical intervention based on duplex ultrasound was judged possible in 85% of the patients (community, 93%; university, 55%). Indications for arteriography included: testing completed prior to surgical consultation (44%), nonfocal extracranial carotid stenosis (23%), nonhemispheric symptoms (13%), and prior stroke (9%). This approach was safe (with a combined operative mortality and neurologic morbidity of 1.8%), asso ciated with long-term stroke prevention (a 95% stroke-free survival at 4 years), and yielded results similar to CEA with arteriography (operative morbidity, 2.6%; 91% stroke- free survival). The incidence and nature of late neurologic deficits were similar after CEA with and without arteriography. Twenty-three (4%) of the patients who underwent CEA based on duplex ultrasound developed late neurologic symptoms including 9 contralat eral and 4 ipsilateral strokes; and 4 ipsilateral and 4 contralateral transient ischemic attacks (TIAs). Cardiac embolism from atrial fibrillation accounted for 6 strokes, lacunar infarct associated with hypertension (3 strokes), intracranial atherosclerosis (3 strokes), and contralateral internal carotid artery (ICA) occlusion (1 stroke). Forty patients (6.8%) died predominantly from cardiac events. After CEA with arteriography 6 (5%) of the patients died. Six late strokes (4 contralateral, and 2 ipsilateral hemisphere) occurred as a result of progressive, untreated ICA stenosis (n = 3), and lacunar infarct (n = 3). Overall, 11% of the patients underwent contralateral CEA for progressive ICA stenosis.

CEA, based on duplex scanning, is safe and applicable for the majority of patients undergoing surgical evaluation. Short-term and long-term outcomes were similar to outcomes in patients having CEA based on diagnostic arteriography.

Effect of Ultrasonography in the Assessment of Carotid Artery Stenosis

Although ultrasonography (US) advantageously portrays lumen and wall thickness, velocity criteria have been used primarily to interpret carotid artery stenosis. The relationship of US and velocity measurements was investigated.

Peak-systolic and end-diastolic velocities (PSV, EDV) increase exponentially as the lumen of the internal carotid artery narrows and the percent stenosis (%S) increases. We tested the consistency of the relationship between carotid velocities and US %S in two distinct data sets. One data set was used to obtain regression equations relating velocity parameters and %S based on US. Validation of these equations was conducted using a separate, independent data set. US measurements were classified in 12 %S intervals. PSV, EDV, the ratio of the internal carotid artery to the common carotid artery PSV, and %S were entered consecutively until 10 records for each %S interval were obtained. Regression equations obtained in the first data set were used to predict %S in the second data set. Predicted %S was then compared with actual US %S.

The highest correlation in the first data set ( r = .89) was between %S and the natural logarithm (ln) of PSV. This ln PSV -%S equation was then applied to a second data set of an additional 120 carotid duplex images. In the second data set, actual %S and PSV–predicted %S differed by > 10% in 38 cases (32%). When all velocity-%S regression equations were used for comparison, differences between actual and at least one velocity-predicted %S were > 10% in 19% of the arteries. Conversely, actual %S matched at least one prediction of %S based on velocity data in 81% of the cases.

US %S differed significantly from single velocity-based estimates of %S in at least one-third of the cases. On the other hand, four of five US measurements were confirmed by at least one velocity parameter. Emphasis on US, in addition to velocity data, is recommended for the interpretation of duplex US carotid examinations.

Carotid duplex criteria for patients with contralateral occlusion

BACKGROUND

Contralateral occlusion (CLO) occurs in approximately 8% of patients undergoing intervention for carotid artery stenosis. Patients with CLO have increased stroke risk compared with patients without CLO, but standard carotid duplex ultrasonography (CDUS) criteria are not a reliable manner to screen or follow patients with CLO. Because appropriate duplex criteria for these patients are not well understood, this article defines CDUS parameters that accurately predict carotid artery stenosis at our institution.

METHODS

Sixty-five patients with ipsilateral carotid stenosis and CLO were identified from our institutional database. Fifteen of sixty-five patients had arteriography, computed tomography angiography, or magnetic resonance angiography within 6 mo of CDUS. We determined accuracy of our laboratory's criteria for determining stenosis category compared with three-dimensional imaging. Receiver operating characteristic curves were used to determine optimal peak systolic velocity (PSV), end diastolic velocity (EDV), and systolic ratio (SR) cutoff values for diagnosing ≥50% stenosis in this pilot cohort. Finally, the revised criteria were prospectively applied to a validation cohort (n = 8) from the same institution.

RESULTS

Categorization of stenosis by standard PSV, EDV, and SR criteria saw similar accuracy trends in both pilot (46.7, 53.3, and 66.7%) and validation (25, 25, and 62.5%) cohorts. Receiver operating characteristic curve analysis in the pilot cohort identified optimized PSV, EDV, and SR cutoffs (≥250, ≥90, and ≥2.3 cm/s, respectively) for diagnosing ≥50% stenosis. In the pilot cohort, new PSV criteria increased specificity (60%-100%) with minimal decreased sensitivity (90%-80%), whereas new EDV criteria increased specificity (40%-71.4%) and maintained 100% sensitivity. New SR criteria failed to improve sensitivity or specificity above 80%. Similar trends for the new CDUS velocity criteria were observed in the validation cohort.

CONCLUSIONS

Increasingly stringent ultrasound parameters can provide reliable criteria for determining ≥50% carotid stenosis in patients with CLO. Further prospective validation that includes more patients with high-grade ipsilateral stenosis will help identify the role of SR in segregating high-grade versus moderate stenosis in CLO patients.

Comparison of Doppler ultrasound velocity parameters in the determination of internal carotid artery stenosis

This study aims to compare the evidence base and practical results of the Joint Recommendations for Reporting Carotid Ultrasound Investigations in UK, published in 2009, and existing carotid scan protocols based on the Society of Radiologists in Ultrasound 2003 Consensus. A prospective sequential evaluation of the 2009 recommendations was performed at the University Hospital of Wales, Cardiff. Additional measurements in line with the recommendations were made during carotid scans. The grading of internal carotid artery stenosis using the 2003 and 2009 UK recommendations, and recommended measures of PSV, PSV ratio and St Mary’s ratio were compared. In comparison to PSV classification, PSV ratio produced lower stenosis classification in 29% and 24% of cases in the 50–69% and 70–89% stenosis bands respectively. St Mary’s ratio produced poor classification agreement across all bands, particularly the 50%–69% stenosis band. Agreement of two measures is recommended for diagnostic confidence; however, in the 50%–69% and 70%–89% stenosis bands, agreement of two measures only occurred in 70% of scans. This evaluation suggests that the use of three measurements in the 2009 recommendations complicates rather than aids diagnosis, especially in the 50%–69% and 70%–89% stenosis bands, and does not provide significant improvement over the 2003 guidelines. No evidence was found to support the combined use of the three measures.

High range resolution ultrasonographic vascular imaging using frequency domain interferometry with the Capon method

For high range resolution ultrasonographic vascular imaging, we apply frequency domain interferometry with the Capon method to a single frame of in-phase and quadrature (IQ) data acquired using a commercial ultrasonographic device with a 7.5 MHz linear array probe. In order to tailor the adaptive beam forming algorithm for ultrasonography we employ four techniques: frequency averaging, whitening, radio-frequency data oversampling, and the moving average. The proposed method had a range resolution of 0.05 mm in an ideal condition, and experimentally detected the boundary couple 0.17 mm apart, where the boundary couple was indistinguishable from a single boundary utilizing a B-mode image. Further, this algorithm could depict a swine femoral artery with a range beam width of 0.054 mm and an estimation error for the vessel wall thickness of 0.009 mm, whereas using a conventional method the range beam width and estimation error were 0.182 and 0.021 mm, respectively. The proposed method requires 7.7 s on a mobile PC with a single CPU for a 1×3 cm region of interest. These findings indicate the potential of the proposed method for the improvement of range resolution in ultrasonography without deterioration in temporal resolution, resulting in enhanced detection of vessel stenosis.

Measurement of carotid artery stenosis: correlation analysis between B-mode ultrasonography and contrast arteriography

Purpose

To evaluate the efficacy of B-mode ultrasonography (US) in measurement of carotid stenosis% (CS%).

Methods

One hundred and thirth-three carotid arteries in 96 patients who underwent both carotid US and carotid arteriography (CA) were included in this retrospective study. To measure CS% on US, a cross sectional view of the most stenotic segment of the internal carotid artery was captured and residual diameter and original diameter of that segment were measured with electronic caliper on the same plane and in the same direction. To measure CS% on an angiogram, we used European Carotid Surgery Trial (ECST) and the North American Symptomatic Carotid Endarterectomy Trial (NASCET) methods. Pearson's correlation analysis and linear regression analysis were used to determine the correlation between CS% on an US and angiogram.

Results

Pearson's correlation coefficient (R) between CS% measured in US and CA were 0.853 (ECST method, P < 0.001) and 0.828 (NASCET method, P < 0.001). Accuracies of B-mode US were 93.2%, 88.0%, and 81.2% for estimating CS% by ECST method and 86.5%, 82.7%, and 82% for estimating CS% by NASCET method.

Conclusion

CS% measured in B-mode US was simpler and showed a strong positive correlation with that measured on an arteriogram either ECST or NASCET method.

Subtle Cerebral Damage after Shunting vs Non Shunting during Carotid Endarterectomy

OBJECTIVE

To compare the extent of subtle cerebral damage (SCD) in patients undergoing carotid endarterectomy with or without shunt placement.

DESIGN

Prospective, randomised study.

PATIENTS AND METHODS

We assessed a consecutive series of 96 patients undergoing endarterectomy for severe unilateral left carotid stenosis who had been randomly assigned to receive a shunt (48) or not (48). Eligibility criteria included age up to 80 years and Mini-Mental State Examination score >24 points. Patients underwent neuropsychological testing before surgery. Serum concentrations of S100 protein, neuron-specific enolase (NSE) and interleukin-6 (IL-6) were measured intraoperatively before and after carotid clamping. Finally, each patient underwent neuropsychological testing 3 weeks after surgery.

RESULTS

Patients with and without shunt had similar serum concentrations of S100 protein, NSE and IL-6 as well as similar neuropsychological test scores, all p>0.05.

CONCLUSIONS

There was no difference in subtle cerebral damage between patients randomized to receive a shunt or not.

Reduced flow velocity in the internal carotid artery independently of cardiac hemodynamics in patients with cerebral ischemia

PURPOSE

To retrospectively investigate the relationships between carotid flow velocities, clinical features and cardiac hemodynamics to assess the meaning and significance of reduced carotid flow velocities in patients with cerebral ischemic symptoms.

METHODS

We selected the files from patients who had undergone duplex Doppler sonographic examination of extracranial carotid arteries, echocardiography, and MR angiography, and in whom the following parameters were available: peak systolic (PSV) and end diastolic (EDV) flow velocity, pulsatility index (PI), and diameter of the left and right common (CCA) and internal (ICA) carotid arteries, intima-media thickness (IMT) of the left and right CCA, left ventricle (LV) mass, peak flow velocity on LV outflow tract, and fractional shortening (FS). Patients with stenosis of the carotid artery or its main intracranial branches were excluded, as were patients with major cerebral infarction, severe intracranial abnormality, or heart function disorder. The remaining 59 patients were subdivided according to the presence or absence of cerebral ischemic symptoms, diabetes mellitus, arterial hypertension, and hyperlipidemia for multivariate analyses and stepwise regressions.

RESULTS

Women had smaller diameters and lower PI in the left and right CCA, and smaller LV mass than men. Age, CCA diameter, and IMT showed an inverse correlation with carotid flow velocities in several arterial segments. There was a positive correlation between PSV in the left CCA and ICA and FS, and between PSV in the left CCA and peak velocity on LV outflow tract. Flow velocities in the left and right ICA were significantly slower in patients with than in patients without cerebral ischemic symptoms.

CONCLUSIONS

Cardiac hemodynamics and carotid flow velocities are significantly related, only on the left side, probably due to larger hemodynamic stress. Increased intracerebral circulatory resistance is probably involved in the decrease in carotid flow velocity and increase in PI in patients with cerebral ischemic symptoms.

Prediction of the Exact Degree of Internal Carotid Artery Stenosis Using an Artificial Neural Network Based on Duplex Velocity Measurements

Duplex ultrasound criteria use a combination of velocity measurements to evaluate internal carotid artery (ICA) stenosis. These evaluations divide ICA stenosis into broad categories. The aim of this study was to design an artificial neural network (ANN) capable of predicting the exact degree of ICA stenosis based on duplex velocity measurements. Consecutive patients with significant carotid atherosclerosis underwent carotid duplex ultrasound and angiography. Peak systolic and end-diastolic velocities in the ICA and common carotid artery were measured. Multilayered perceptron ANNs were constructed and trained to predict the degree of ICA stenosis and band the degree of ICA stenosis into 10% intervals based on these measurements. The accuracy of the ANN models in predicting the degree of ICA stenosis and classifying the ICA stenosis was compared with the angiographic degree of ICA stenosis and duplex velocity criteria. A total of 208 carotid bifurcations were studied. ANNs were able to accurately predict the degree of angiographic ICA stenosis (R2 = 0.9374, p < 0.0001) and band the ICA stenosis into the predefined 10% intervals [sensitivity 97.3% (95% CI 90.7-99.3), specificity 97.7 % (95% CI 93.6-99.2), accuracy 97.5%]. The ANN model was more accurate [discriminant power (DP) = 4.11] in banding the degree of ICA stenosis than duplex velocity criteria (DP = 1.67) (p < 0.05). The accuracy of the ANN in correctly identifying >70% ICA stenosis was 98.4% [sensitivity 96.4% (95% CI 93.8-99.3), specificity 98.7% (95% CI 93.4-99.8), DP = 4.21]. ANNs can accurately predict the degree of ICA stenosis. With further refinement, ANNs could replace velocity criteria in the assessment of ICA stenosis using duplex ultrasound.

Are we undertreating carotid stenoses diagnosed by ultrasound alone?

Clinical management of carotid disease is primarily based on results of national trials (ACAS and NASCET) that used the distal internal carotid artery diameter as a reference. However, commonly accepted ultrasound (US) criteria for carotid stenosis were derived from the correlation of velocity measurements with angiographic bulb diameter reductions (BDR). This study was undertaken to compare the degree of carotid stenosis determined by conventional velocity criteria to the degree of stenosis measured by B-mode (gray scale) diameter at both the carotid bulb and at the distal internal carotid artery, and, second, to evaluate US imaging to derive distal diameter reductions (DDR) noninvasively. During a 3-month period patients referred for carotid US were prospectively analyzed for standard velocity criteria and plaque morphology. Minimum carotid diameter was measured by longitudinal and transverse B-mode measurements and compared to carotid bulb diameter and internal carotid diameter distal to all disease. B-mode diameter reductions were compared to the degree of stenosis determined by velocity criteria and to patient symptoms and the decision for carotid endarterectomy. In total, 131 carotid arteries in 74 patients were evaluated. Based on the University of Washington velocity criteria, lesions were classified as grade I (n = 61, 46%), IIA (n = 58, 44%), IIB (n = 7, 5%), or III (n = 5, 4%). BDR measured by B-mode predicted the grade of disease based on velocity criteria (p < 0.001) with an overall accuracy of 95%. With use of the B-mode for DDR (NASCET style), 18 patients exceeded the 60% threshold for surgical intervention. Of these, only 3 patients were symptomatic and were operated on. An additional 3 operated-on patients had an asymptomatic grade III stenosis, our usual threshold for intervention. Twelve additional patients were appropriate for surgical intervention by B-mode but were not treated based on conventional velocity criteria alone. Bulb diameter reduction by B-mode imaging correlates strongly with diameter reduction determined by velocity criteria, and independently predicts the grade of carotid disease. With this in mind, the accuracy of B-mode imaging may be extended to the measurement of carotid stenosis based on DDR. By B-mode criteria, many patients appropriate for intervention were not offered treatment based on conventional velocity criteria. Modern B-mode imaging provides a noninvasive method to obtain 'arteriographic equivalent'' measurements and should be added as a routine to carotid ultrasound interrogation.

Sensitivity and specificity of color duplex ultrasound measurement in the estimation of internal carotid artery stenosis: A systematic review and meta-analysis

BACKGROUND

Duplex ultrasound is widely used for the diagnosis of internal carotid artery stenosis. Standard duplex ultrasound criteria for the grading of internal carotid artery stenosis do not exist; thus, we conducted a systematic review and meta-analysis of the relation between the degree of internal carotid artery stenosis by duplex ultrasound criteria and degree of stenosis by angiography.

METHODS

Data were gathered from Medline from January 1966 to January 2003, the Cochrane Central Register of Controlled Trials and Database of Systematic Reviews, Database of Abstracts of Reviews of Effects, ACP Journal Club, UpToDate, reference lists, and authors' files. Inclusion criteria were the comparison of color duplex ultrasound results with angiography by the North American Symptomatic Carotid Endarterectomy Trial method; peer-reviewed publications, and >/=10 adults.

RESULTS

Variables extracted included internal carotid artery peak systolic velocity, internal carotid artery end diastolic velocity, internal carotid artery/common carotid artery peak systolic velocity ratio, sensitivity and specificity of duplex ultrasound scanning for internal carotid artery stenosis by angiography. The Standards for Reporting of Diagnostic Accuracy (STARD) criteria were used to assess study quality. Sensitivity and specificity for duplex ultrasound criteria were combined as weighted means by using a random effects model. The threshold of peak systolic velocity >/=130 cm/s is associated with sensitivity of 98% (95% confidence intervals [CI], 97% to 100%) and specificity of 88% (95% CI, 76% to 100%) in the identification of angiographic stenosis of >/=50%. For the diagnosis of angiographic stenosis of >/=70%, a peak systolic velocity >/=200 cm/s has a sensitivity of 90% (95% CI, 84% to 94%) and a specificity of 94% (95% CI, 88% to 97%). For each duplex ultrasound threshold, measurement properties vary widely between laboratories, and the magnitude of the variation is clinically important. The heterogeneity observed in the measurement properties of duplex ultrasound may be caused by differences in patients, study design, equipment, techniques or training.

CONCLUSIONS

Clinicians need to be aware of the limitations of duplex ultrasound scanning when making management decisions.

Notions d’hémodynamique et techniques ultrasonores pour l’exploration des artères

Arterosclerosis is the main cause of arterial lesions and leads to arterial stenoses. In order to preserve distal perfusion, flow velocities increase at the site of stenosis due to reduced peripheral resistance. Doppler sonography (US) allows detection of hemodynamic abnormalities at the site of stenosis and evaluation of its impact on distal flow. Several parameters and imaging features including resistive indices and systolic velocities are measured in order to characterize the degree of stenosis and its impact on perfusion. In addition, B-mode US allows morphologic evaluation of lesions. Doppler US is useful to evaluate lower limb arteries, renal arteries and neck arteries.

[Significance of Doppler ultrasound procedures for diagnosis of carotid stenoses]

Determining degree and morphology of stenoses is important for surgical planning or stent implantation. Vascular ultrasound is usually the first modality to evaluate carotid artery stenosis. Due to rapid development various methods of vascular ultrasound are applied including continuous wave (CW) Doppler, duplex Doppler, colour-coded duplex sonography (CCDS), power Doppler and B-flow technique. For quantitative assessment of the degree of stenosis the most frequently used parameters are peak systolic velocity (PSV), end-diastolic velocity (EDV) in the internal carotid artery (ICA), as well as ICA to CCA ratios of PSV and EDV. Different results reported in the literature may reflect differences in defining the degree of stenosis and methodological differences in protocol or imaging techniques. Differences in defining the degree of stenosis, advantages and disadvantages of the different Doppler techniques and future developments are discussed in detail.

Evaluation of extracranial carotid artery duplex ultrasound scanning parameters in cerebral ischemic or nonischemic patients without significant cervical carotid artery stenosis

Although extracranial carotid artery duplex ultrasound scanning (ECADUS) is frequently used to detect cervical carotid artery stenosis, the method for interpreting the parameters obtained by ECADUS is not well established when cervical carotid artery stenosis does not exist. We retrospectively studied the parameters obtained from 180 patients without significant cervical carotid artery stenosis. The peak systolic velocity (PSV), end diastolic velocity (EDV), pulsatility index (PI) and diameter of the cervical internal carotid artery, and intima media thickness (IMT) of the common carotid artery were obtained bilaterally. These parameters were evaluated according to the side and the patient's sex, age, and cerebral ischemic symptoms. No significant effects of the side or sex were observed on any parameters. Aging affected the IMT and PI positively and the EDV negatively. The PI correlated positively with the IMT. In the symptomatic group the PSV and EDV decreased; this was still observed after adjustments for age. These results confirm the effects of aging. PI seems to be another indicator of cerebral atherosclerosis, because it correlates well with IMT, a well-recognized indicator. Cerebral ischemic symptoms may be affected by reduced velocity more than by atherosclerotic progression. This phenomenon requires further evaluation.

Association of increased carotid intima-media thickness with the extent of coronary artery disease

OBJECTIVE

To investigate (a) the relation between intima-media thickness (IMT) in carotid arteries and the extent of coronary artery disease (CAD); and (b) whether IMT is predictive of coronary atherosclerosis. The coexistence of severe extracranial atherosclerosis in patients with CAD was also analysed.

METHODS

Coronary angiography and carotid ultrasound evaluation were performed in 558 consecutive patients (438 men), with a mean (SD) age of 58.8 (9.2) years and suspected CAD. Mean IMT was measured at both carotid arteries and expressed as the mean aggregate value. The relation between IMT and severity of CAD was determined.

RESULTS

A significant correlation between mean IMT and advancing CAD (p < 0.0001) was found. Four independent predictors of CAD were found in the discriminant analysis: age (p = 0.0193), hyperlipidaemia (p < 0.0001), smoking (p = 0.0032), and IMT (p < 0.0001). A significant increase in IMT was observed among patients with one, two, and three vessel CAD. A log normal distribution of IMT values showed that if mean IMT was over 1.15 mm, patients had a 94% probability of having CAD, with sensitivity of 65% and specificity of 80% in the patients with a high risk of CAD. The number of critically stenosed extracranial arteries increased with advancing CAD. None of the patients with normal coronary arteries had severe stenosis of the extracranial arteries. Severe carotid, vertebral, or subclavian stenosis was found in 16.6% of patients with three vessel CAD.

CONCLUSIONS

IMT increases with advancing CAD, patients with mean IMT over 1.15 mm have a 94% likelihood of having CAD, and the coexistence of CAD with severe stenosis of aortic arch arteries is relatively high and was found in 16.6% of patients with three vessel CAD.

Gender differences in blood velocities across carotid stenoses

OBJECTIVES

Carotid duplex scanning is the standard test for documenting carotid disease. Carotid endarterectomy effectively reduces stroke in selected patients with carotid artery disease. Data from large national randomized trials suggest that the benefits of CEA may be gender dependent. Because many diagnoses are made and treatment is based on the results of carotid duplex ultrasound scanning alone, it is important to determine whether different diagnostic thresholds should be used in men and women. The purpose of this study was 2-fold: to examine whether there is an overall gender difference in carotid velocity at similar arteriographic stenoses, and to determine whether there are significant differences at clinically relevant thresholds of disease.

METHODS

A database of 938 carotid arteriogram entries was established prospectively, with accompanying measurements of peak systolic velocity (PSV) and end-diastolic velocity (EDV). The percent of internal carotid artery stenosis seen on arteriograms was calculated according to criteria from the North American Symptomatic Carotid Endarterectomy Trial. Analyses were made in 536 carotid arteries in men and 402 carotid arteries in women. In addition, the single most diseased artery per patient was analyzed by gender. PSV and EDV were averaged for data subsets according to 10% intervals of internal carotid artery stenoses. Velocity for each interval was compared between men and women with the Student t test. Receiver operator characteristic curves were developed to define optimal duplex criteria for 60% and 70% stenosis.

RESULTS

For all intervals, PSV and EDV averaged 9% and 6% higher, respectively, in women than in men. Significant gender differences existed between PSV and EDV for 60% and 70% stenosis (P = .03). When a single vessel per patient was analyzed these observations persisted, but lost significance for PSV at 60% stenosis (P = .18). Receiver operator characteristic curves at 90% sensitivity demonstrated that optimal PSV for 60% stenosis was 160 cm/s and 180 cm/s, and for 70% stenosis was 185 cm/s and 202 cm/s, in male and female patients, respectively.

CONCLUSIONS

Women have higher carotid blood flow velocity than men do. Gender differences exist, and are notably different at clinically relevant thresholds for intervention. These data indicate that different criteria should be used for interpreting carotid velocity profiles in women than in men, and have potentially important implications for patient care.

Comparison of ultrasonography, CT angiography, and digital subtraction angiography in severe carotid stenoses

Digital subtraction angiography (DSA) is considered to be the 'gold standard' for confirmation of severe (70-99%) stenoses of internal carotid arteries (ICAs). However, it is associated with a risk of complications. The aim of this study was to assess the accuracy of ultrasonography (US), computed tomographic angiography (CTA), and their combined use for the detection and quantification of severe carotid stenoses, when compared with DSA. Severe ICA stenoses were diagnosed by US in a set of 29 patients. All patients also underwent CTA and DSA. Sensitivity, specificity, positive (PPV), negative predictive values (NPV), and Pearson's correlation coefficient were used in the evaluation of the percentage of stenosis results. Homogeneity chi2 test was applied when assessing statistical significance. Severe stenosis was diagnosed in 34 ICAs. Two ICAs with uninterpretable CTA finding were excluded. The number of ICAs with stenoses 70-99%/<70%- US 32/0; CTA 29/3; US + CTA 29/3; DSA 24/8. Pearson's correlation coefficient - US 0.601; CTA 0.725; US + CTA 0.773. Sensitivity/specificity/PPV/NPV - US 1.0/0.75/0.75/xxx; CTA 1.0/0.844/0.828/1.0; US + CTA 1.0/0.844/0.828/1.0. Homogeneity chi2 test results - US, P = 0.002; CTA, P = 0.098; US + CTAG, P = 0.098. US in combination with CTA can be used for relatively secure diagnostics of severe ICA stenoses. Thus, invasive DSA can be avoided in a substantial number of patients.

Three-Dimensional Assessment of Extracranial Doppler Sonography in Carotid Artery Stenosis Compared With Digital Subtraction Angiography

Background and Purpose— Difficulties in data presentation, data storage, and a high interobserver variability may influence color-coded Duplex sonography assessment of internal carotid artery stenosis (ICAS). The aim of our study was to evaluate the between-method agreement of ICAS using 3D color Doppler sonography (CDS) compared with digital subtraction angiography (DSA).

Methods— Forty-nine patients with 64 ICASs (age 64±9 years) were involved. The patients were investigated with a color-coded duplex system using the power mode. The 3D system consists of an electromagnet that induces a low-intensity magnetic field near the patient’s head. A magnetic position sensor is attached to the probe and transmits the spatial orientation to a personal computer.

Results— A total of 62 ICASs were reconstructed successfully with 3D CDS in 47 of 49 patients. High agreement for 2 independent observers was found in 3D CDS (weighted κ coefficient of 0.88). Three-dimensional CDS slightly underestimated the mean stenotic degree (mean 3D CDS 68.47±10.5 versus DSA 71.3±10.0). The intermethod agreement comparing DSA with 3D CDS was analyzed with the Bland and Altman test, which showed good agreement. Mean sensitivity of 3D CDS was 93%, mean specificity 82.5%, mean positive predictive value 82%, and mean negative predictive value 98%.

Conclusions— The 3D CDS findings demonstrated good agreement compared with the gold standard, DSA, yielding higher accuracy than CDS alone. Compared with angiography or magnetic resonance angiography, 3D CDS can be performed easily on critically ill patients in stroke or intensive care units and may therefore provide a useful tool for patients unable to undergo more invasive imaging techniques.

B-flow imaging of internal carotid artery stenosis: Comparison with power Doppler imaging and digital subtraction angiography

PURPOSE

Digital subtraction angiography (DSA) is the gold standard in the diagnosis of carotid artery stenosis, but it has a relatively high complication rate. We evaluated the efficacy of B-flow imaging (BFI) in examining internal carotid artery stenosis (ICAS) compared with power Doppler imaging (PDI) and DSA.

METHODS

We performed BFI, PDI, and DSA on 56 consecutive patients with suspected ICAS. The degree of stenosis was calculated for each technique, and results of BFI and PDI were then correlated with those of DSA.

RESULTS

Measurements of the percentage of stenosis made using both sonographic techniques were significantly correlated with those of DSA (p < 0.0001). However, the coefficient of correlation between DSA and BFI (r = 0.94) was higher than that between DSA and PDI (r = 0.87). The mean difference between ICAS measurements with BFI and DSA was -1.3% (95% confidence interval [CI], -2.5 to 0). The mean difference between ICAS measurements with PDI and DSA was -6.5% (95% CI, -8.2 to -4.7). ICAS was graded significantly lower on PDI than on DSA, whereas BFI findings were similar to those of DSA.

CONCLUSION

BFI shows high correlation with DSA and provides a more accurate planimetric evaluation of ICAS than PDI does.

Carotid artery stenosis: grayscale and Doppler ultrasound diagnosis--Society of Radiologists in Ultrasound consensus conference

The Society of Radiologists in Ultrasound convened a multidisciplinary panel of experts in the field of vascular ultrasonography (US) to come to a consensus regarding Doppler US for assistance in the diagnosis of carotid artery stenosis. The panel's consensus statement is believed to represent a reasonable position on the basis of analysis of available literature and panelists' experience. Key elements of the statement include the following: First, all internal carotid artery (ICA) examinations should be performed with grayscale, color Doppler, and spectral Doppler US. Second, the degree of stenosis determined at grayscale and Doppler US should be stratified into the categories of normal (no stenosis), less than 50% stenosis, 50 to 69% stenosis, > or =70% stenosis to near occlusion, near occlusion, and total occlusion. Third, ICA peak systolic velocity (PSV) and the presence of plaque on grayscale and/or color Doppler images are primarily used in the diagnosis and grading of ICA stenosis. Two additional parameters (the ICA-to-common carotid artery PSV ratio and ICA end diastolic velocity) may also be used when clinical or technical factors raise concern that ICA PSV may not be representative of the extent of disease. Fourth, ICA should be diagnosed as normal when ICA PSV is less than 125 cm/second and no plaque or intimal thickening is visible, less than 50% stenosis when ICA PSV is less than 125 cm/second and plaque or intimal thickening is visible, 50 to 69% stenosis when ICA PSV is 125 to 230 cm/second and plaque is visible, > or =70% stenosis to near occlusion when ICA PSV is more than 230 cm/second and visible plaque and lumen narrowing are seen, near occlusion when there is a markedly narrowed lumen on color Doppler US, and total occlusion when there is no detectable patent lumen on grayscale US and no flow on spectral, power, and color Doppler US. Fifth, the final report should discuss velocity measurements and grayscale and color Doppler findings. Study limitations should be noted when they exist. The conclusion should state an estimated degree of ICA stenosis as reflected in these categories. The panel also considered various technical aspects of carotid US and methods for quality assessment, and identified several important unanswered questions meriting future research.

Carotid artery stenting: is there a need to revise ultrasound velocity criteria?

OBJECTIVES

Ultrasound (US) velocity criteria have not been well-established for patients undergoing carotid artery stenting (CAS). A potential source of error in using US after CAS is that reduced compliance in the stented artery may result in elevated velocity relative to the native artery. We measured arterial compliance in the stented artery, and developed customized velocity criteria for use early after CAS.

METHODS

US was performed before and within 3 days after CAS, and after 1 month in a subset of 26 patients. Post-procedural peak systolic velocity (PSV) and end-diastolic velocity (EDV) of the internal carotid artery (ICA), PSV/EDV ratio, and internal carotid artery to common carotid artery ratio (ICA/CCA) were recorded. These were compared with degree of in-stent residual stenosis determined at carotid angiography performed at the completion of CAS. Peterson's elastic modulus (Ep) and compliance (Cp) of the ICA were determined in a subgroup of 20 patients at the distal end of the stent and in the same region in the native ICA before stenting.

RESULTS

Ninety CAS procedures were analyzed. Mean (+/-SD) angiographic residual stenosis after CAS was 5.4 +/- 9.1%, whereas corresponding PSV by US was 120.4 +/- 32.4 cm/s; EDV, 41.4 +/- 18.6 cm/s; PSV/EDV ratio, 3.3 +/- 1.2; and ICA/CCA ratio, 1.6 +/- 0.5. PSV was unchanged at 1 month. Post-CAS PSV and ICA/CCA ratio correlated most with degree of stenosis (P <.0001 for both). Only six patients demonstrated in-stent residual stenosis 20% or greater, but the standard US threshold of PSV 130 cm/s or greater (validated for >20% ICA stenosis in our laboratory) categorized 38 of 90 patients as having stenosis 20% or greater. Receiver operator curve analysis demonstrated that a combined threshold of PSV 150 cm/s or greater and ICA/CCA ratio 2.16 or greater were optimal for detecting residual stenosis of 20% or greater, with sensitivity 100%, specificity 98%, positive predictive value 75%, and negative predictive value 100%. After placement of a stent, the ICA demonstrated significantly increased Ep (1.2 vs 4.4 x 10(3) mm Hg; P =.004) and decreased Cp (9.8 vs 3.2 %mm Hg x 10(-2); P =.0004).

CONCLUSIONS

Currently accepted US velocity criteria validated in our laboratory for nonstented ICAs falsely classified several stented ICAs with normal diameter on carotid angiograms as having residual in-stent stenosis 20% or greater. We propose a new criterion that defines PSV less than 150 cm/s, with ICA/CCA ratio less than 2.16, as the best correlate to a normal lumen (0%-19% stenosis) in the recently stented ICA. This was associated with increased stiffness of the stented ICA (increased Ep, decreased Cp). These preliminary results suggest that placement of a stent in the carotid artery alters its biomechanical properties, which may cause an increase in US velocity measurements in the absence of a technical error or residual stenotic disease.

Carotid arteries: contrast-enhanced US angiography--preliminary clinical experience

B-mode ultrasonographic (US) angiography enhanced with a microbubble-based US contrast agent (FS069) was evaluated in human subjects with carotid artery disease. Results at contrast material-enhanced US angiography and duplex US were compared with those at conventional angiography. Both US angiography and duplex US accurately depicted stenoses of 70% or more compared with those depicted at conventional angiography. The percentage diameter stenosis of the internal carotid artery measured at US angiography strongly correlated with that measured at conventional angiography (r = 0.988). The percentage area stenosis measured at US angiography strongly correlated with ex vivo measurements of the resected carotid plaque at magnetic resonance imaging (r = 0.979). US angiography depicted unsuspected wall irregularities, ulceration, and dissection.

Carotid artery stenosis: gray-scale and Doppler US diagnosis--Society of Radiologists in Ultrasound Consensus Conference

The Society of Radiologists in Ultrasound convened a multidisciplinary panel of experts in the field of vascular ultrasonography (US) to come to a consensus regarding Doppler US for assistance in the diagnosis of carotid artery stenosis. The panel's consensus statement is believed to represent a reasonable position on the basis of analysis of available literature and panelists' experience. Key elements of the statement include the following: (a) All internal carotid artery (ICA) examinations should be performed with gray-scale, color Doppler, and spectral Doppler US. (b) The degree of stenosis determined at gray-scale and Doppler US should be stratified into the categories of normal (no stenosis), <50% stenosis, 50%-69% stenosis, > or =70% stenosis to near occlusion, near occlusion, and total occlusion. (c) ICA peak systolic velocity (PSV) and presence of plaque on gray-scale and/or color Doppler images are primarily used in diagnosis and grading of ICA stenosis; two additional parameters, ICA-to-common carotid artery PSV ratio and ICA end-diastolic velocity may also be used when clinical or technical factors raise concern that ICA PSV may not be representative of the extent of disease. (d) ICA should be diagnosed as (i) normal when ICA PSV is less than 125 cm/sec and no plaque or intimal thickening is visible; (ii) <50% stenosis when ICA PSV is less than 125 cm/sec and plaque or intimal thickening is visible; (iii) 50%-69% stenosis when ICA PSV is 125-230 cm/sec and plaque is visible; (iv) > or =70% stenosis to near occlusion when ICA PSV is greater than 230 cm/sec and visible plaque and lumen narrowing are seen; (v) near occlusion when there is a markedly narrowed lumen at color Doppler US; and (vi) total occlusion when there is no detectable patent lumen at gray-scale US and no flow at spectral, power, and color Doppler US. (e) The final report should discuss velocity measurements and gray-scale and color Doppler findings. Study limitations should be noted when they exist. The conclusion should state an estimated degree of ICA stenosis as reflected in the above categories. The panel also considered various technical aspects of carotid US and methods for quality assessment and identified several important unanswered questions meriting future research.

Management of mobile floating carotid plaque using carotid artery stenting

PURPOSE

To present management techniques for dealing with mobile floating carotid plaque (MFCP), which represents an indeterminate risk of embolic cerebrovascular events.

CASE REPORTS

Two high-risk patients with a history of carotid endarterectomy were diagnosed with MFCP by duplex ultrasound scanning. One patient had a left hemispheric transient ischemic attack while the other was asymptomatic with a moderate stenosis. Both were successfully treated with carotid artery stenting, achieving complete coverage of the MFCP. Their outcomes were uneventful, and sustained patency of the stented arteries has been observed during an event-free survival of 32 and 44 months, respectively.

CONCLUSIONS

Based upon the unique nature of these lesions and our satisfactory clinical results, we believe that carotid stenting may be a viable option for the treatment of MFCP.

Carotid surgery without external carotid endarterectomy: a 6-year clinical experience with 1027 cases

PURPOSE

previously we routinely performed endarterectomy of the external carotid artery (ECA) during carotid surgery. However, discouraging experience and lack of supportive data in the literature made us question its necessity. The present report describes our experience with a modified carotid endarterectomy (CEA) technique where the ECA is left undisturbed regardless of its degree of stenosis.

METHODS

from January 1996 to June 2001, 1027 CEAs were performed in 905 patients with this technique at our institution. All operations were performed for at least 60% internal carotid artery (ICA) stenosis. A preoperative carotid duplex scan was available for review in 990 cases (96%). Follow-up duplex scans were recovered from 0 to 1 months in 851 cases (83%) and from >1 month in 655 cases (64%). Seventy percent of these cases were performed for asymptomatic lesions.

RESULTS

the perioperative (30-day) mortality rate for the entire group of patients was 0.5% and the stroke rate was 0.7%. Mean follow-up was 18 months (range: 2-66 months). Only two ECAs occluded in the first postoperative month. During the follow-up period, 37 additional ECAs (5.6%) were found to progress from mild to severe (>75%) stenosis postoperatively. In addition, 7% of the cases were found to have worsened the degree of stenosis, 8% improved and 85% remained unchanged.

CONCLUSION

these data support sparing of the ECA during CEA.

Duplex ultrasound and magnetic resonance angiography compared with digital subtraction angiography in carotid artery stenosis: a systematic review

BACKGROUND AND PURPOSE

The purpose of this work was to review and compare published data on the diagnostic value of duplex ultrasonography (DUS), MR angiography (MRA), and conventional digital subtraction angiography (DSA) for the diagnosis of carotid artery stenosis.

METHODS

We performed a systematic review of published studies retrieved through PUBMED, from bibliographies of review papers, and from experts. The English-language medical literature was searched for studies that met the selection criteria: (1) The study was published between 1994 and 2001; (2) MRA and/or DUS was performed to estimate the severity of carotid artery stenosis; (3) DSA was used as the standard of reference; and (4) the absolute numbers of true positives, false negatives, true negatives, and false positives were available or derivable for at least one definition of disease (degree of stenosis).

RESULTS

Sixty-three publications on duplex, MRA, or both were included in the analysis, yielding the test results of 64 different patient series on DUS and 21 on MRA. For the diagnosis of 70% to 99% versus <70% stenosis, MRA had a pooled sensitivity of 95% (95% CI, 92 to 97) and a pooled specificity of 90% (95% CI, 86 to 93). These numbers were 86% (95% CI, 84 to 89) and 87% (95% CI, 84 to 90) for DUS, respectively. For recognizing occlusion, MRA yielded a sensitivity of 98% (95% CI, 94 to 100) and a specificity of 100% (95% CI, 99 to 100), and DUS had a sensitivity of 96% (95% CI, 94 to 98) and a specificity of 100% (95% CI, 99 to 100). A multivariable summary receiver-operating characteristic curve (ROC) analysis for diagnosing 70% to 99% stenosis demonstrated that the type of MR scanner predicted the performance of MRA, whereas the presence of verification bias predicted the performance of DUS. For diagnosing occlusion, no significant heterogeneity was found for MRA; for DUS, the presence of verification bias and type of DUS scanner were explanatory variables. MRA had a significantly better discriminatory power than DUS in diagnosing 70% to 99% stenosis (regression coefficient, 1.6; 95% CI, 0.37 to 2.77). No significant difference was found in detecting occlusion (regression coefficient, 0.73; 95% CI, -2.06 to 3.51).

CONCLUSIONS

These results suggest that MRA has a better discriminatory power compared with DUS in diagnosing 70% to 99% stenosis and is a sensitive and specific test compared with DSA in the evaluation of carotid artery stenosis. For detecting occlusion, both DUS and MRA are very accurate.

Stump pressure and transcranial Doppler for predicting shunting in carotid endarterectomy

OBJECTIVES

to compare stump pressure (SP) and transcranial Doppler (TCD) with neurologic monitoring during carotid endarterectomy (CEA).

MATERIALS

one hundred and forty-seven CEAs performed under local anaesthesia.

METHODS

neurologic monitoring and SP were performed in all cases, while mean velocity of the middle cerebral artery (mvMCA) by TCD was done in 140/147 (95%) cases. Shunts were applied in all cases on the basis of neurologic monitoring. The following haemodynamic criteria have been compared to neurologic monitoring: (a) <25 mmHg SP; (b) <50 mmHg SP; (c) < or =10 cm/s mvMCA after carotid occlusion; (d) > or =70 decrease of mvMCA after carotid occlusion. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated for each haemodynamic criterion.

RESULTS

shunt was used in 18/147 (12.2%) cases. With regards to <25 mmHg SP, < or =50 mmHg SP, < or =10 cm/s mvMCA after carotid occlusion, and > or =70 decrease of mvMCA after carotid occlusion, sensitivity resulted 33, 89, 80 and 80%, respectively. Specificity resulted 96, 82, 97 and 96%, respectively. Positive predictive value resulted 55, 41, 75 and 71%, respectively. Negative predictive value 91, 98, 98 and 98%, respectively. Accuracy resulted 88, 76, 89 and 94%, respectively.

CONCLUSIONS

none of the haemodynamic criteria by SP and TCD resulted absolutely reliable in predicting the need for carotid shunt.

The vascular laboratory in practice: a national survey in the Netherlands

OBJECTIVES

to overview Dutch vascular laboratory practice and specifically the variation in duplex criteria.

METHODS

a questionnaire was sent to all vascular laboratories in The Netherlands (n=140).

RESULTS

the response rate of the inquiry was 64% (n=89). There is no consensus on interpretation of outcome. In 22% of the clinics (n=20) a diagnostic angiography will be omitted when a percutaneous angioplasty is advised on account of duplex ultrasound. Only 5% (n=4) relies upon duplex ultrasound for operation without diagnostic angiography. In 44% (n=39) a PSV (peak systolic velocity) of 125 cm/s is used to identify a>70% or internal carotid artery stenosis. In 44% (n=39) a PSV of 210 cm/s and 10% (n=9) a PSV > or =150 cm/s is used. For grading a relevant stenosis in the femoro-politeal arteries a PSV ratio > or =2.5 is chosen in 75% (n=67). Criteria used for graft surveillance shows also a wide variation.

CONCLUSIONS

a commission for the accreditation of vascular laboratories should be established with the goal of creating standards and performing quality control.

B-flow evaluation of carotid arterial stenosis: initial experience

In this prospective pilot trial, B-flow ultrasonographic (US) imaging was compared with color duplex flow US in the evaluation of internal carotid arterial stenosis. Despite almost excellent interobserver variability, none of the investigated B-flow imaging parameters correlated with those of duplex US. In conclusion, the investigated B-flow imaging parameters cannot be used in evaluating internal carotid arterial stenosis.

Cerebral haemodynamic aspects of severe carotid stenosis: asymptomatic vs symptomatic

OBJECTIVES

to compare cerebral haemodynamics in patients with asymptomatic and symptomatic severe (> or =70%) internal carotid artery (ICA) stenosis.

METHODS

we assessed 195 consecutive patients, 116 with asymptomatic carotid stenosis (ACS) and 79 with symptomatic carotid stenosis (SCS). Using transcranial Doppler we assessed cerebral vasoreactivity (CVR) following acetazolamide test, the middle cerebral artery flow velocity ratio after/before carotid clamping (mv-MCA ratio), and the carotid back pressure (CBP) during crossclamping.

RESULTS

no significant differences between the two groups were demonstrated regarding CVR (47 vs 39%), mv-MCA ratio (50 vs 52%), or CBP (36 vs 44 mmHg). However, in patients with contralateral ICA occlusion all three variables were significantly lower as compared to patients with patent contralateral ICA. Also patients who needed a shunt during surgery had significantly lower values of mv-MCA ratio and CBP. Patients who suffered peri-operative neurologic deficits (n=6; 3%) did not differ from patients who had an uneventful course.

CONCLUSIONS

clinical state of ICA stenosis is independent of cerebral haemodynamics. Occluded contralateral ICA is more important for predicting cerebral ischaemia caused by carotid clamping. Finally, none of the haemodynamic parameters showed predictive value for peri-operative neurologic morbidity.

Critical review of non- or minimally invasive methods (duplex ultrasonography, MR- and CT-angiography) for evaluating stenosis of the proximal internal carotid artery

OBJECTIVE

to assess the performance of non- or minimally invasive methods (duplex ultrasonography, MR- and CT-angiography) in measuring stenosis of the proximal internal carotid prior to endarterectomy without preoperative intra-arterial digital subtraction angiography (DSA).

METHODS

systematic review of the literature (five databases, 1990 to February 2001). The value of each imaging technique was studied through its reproducibility and its sensitivity/specificity compared to DSA.

RESULTS

sensitivity exceeded 80% and specificity 90% in over two-thirds of the methodologically sound studies, regardless of technique, although direct comparisons between results had to be avoided since the findings originated from different populations. The main drawback of duplex ultrasonography is its levels of reproducibility. In contrast, only a few studies have addressed the reproducibility of MR- and CT-angiography. When the results of duplex and MR-angiography agree, the combination use of these two techniques provides a better diagnosis than either technique taken alone.

CONCLUSIONS

all three techniques appear suitable for measuring stenosis of the proximal internal carotid when compared to DSA.

Diagnostic performance of duplex ultrasonography in the detection of high grade internal carotid artery stenosis

OBJECTIVES

to establish on a national basis whether the diagnostic accuracy of carotid duplex justifies carotid surgery without preoperative angiography.

DESIGN

prospective national multicentre study with 10 participating university and county hospitals.

MATERIAL AND METHODS

one hundred and thirty-four patients, aged 69+/-9 years, were subjected to routine carotid duplex ultrasonography and angiography. The influence of relevant factors on the relation between ultrasonographic and angiographic variables was evaluated using multiple regression analysis. The capacity of carotid ultrasonography to detect internal carotid artery (ICA) stenosis > or =80% was assessed by receiver operating characteristic analysis.

RESULTS

the correlation between peak systolic velocity in ICA (PSV(ICA)) and the angiographic degree of stenosis was strong and significantly influenced only by the applied Doppler angle. Accordingly, the optimal PSV(ICA) cutpoint values for the diagnosis of ICA stenosis > or =80% (ECST method) differed substantially (2.1 and 3.2 m/s) between the two considered angle ranges (0-49 degrees and 50-62 degrees ), the ability to identify high grade ICA stenosis being significantly better at small Doppler angles (0-49 degrees ).

CONCLUSION

ultrasonographic duplex technique identifies high grade ICA stenosis with a high degree of accuracy, which can be further improved by the application of small Doppler angles and the use of angle range specific PSV(ICA) cut-off points.

The impact of different spectral Doppler criteria on the proportion of high-grade internal carotid artery stenosis in patients undergoing duplex scanning

AIM

To investigate the impact of different spectral Doppler criteria on the proportion of high-grade ICA stenosis in patients undergoing carotid artery duplex scanning.

MATERIAL AND METHODS

Duplex scans of 4,548 internal carotid arteries (ICA) in 2,349 patients were retrospectively analyzed. The following different criteria were applied for each scan for definition of ICA stenosis > or = 70%: Criteria I=ICA peak systolic velocity (PSV) > 130 cm/sec and ICA end-diastolic (EDV) > 100 cm/sec, Criteria II=PSV ICA/common carotid artery (CCA) ratio > 4, Criteria III=ICA PSV > or = 230 cm/sec, Criteria IV=ICA PSV > 230 cm/sec and/or ICA EDV > or = 100 cm/sec and/or PSV ICA/CCA ratio > or = 3.2.

RESULTS

The frequency of detecting a > or = 70% ICA stenosis with criteria I, II, III, and IV were 5.5%, 6.8%, 8.4%, and 9.6%, respectively (p < 0.05).

CONCLUSION

The use of various duplex criteria significantly affected the number of scans receiving a diagnosis of ICA stenosis of > or = 70%.