Carotid endarterectomy without arteriography

Duplex ultrasound for diagnosing symptomatic carotid stenosis in the extracranial segments

BACKGROUND

Carotid artery stenosis is an important cause of stroke and transient ischemic attack. Correctly and rapidly identifying patients with symptomatic carotid artery stenosis is essential for adequate treatment with early cerebral revascularization. Doubts about the diagnostic value regarding the accuracy of duplex ultrasound (DUS) and the possibility of using DUS as the single diagnostic test before carotid revascularization are still debated.

OBJECTIVES

To estimate the accuracy of DUS in individuals with symptomatic carotid stenosis verified by either digital subtraction angiography (DSA), computed tomography angiography (CTA), or magnetic resonance angiography (MRA).

SEARCH METHODS

We searched CRDTAS, CENTRAL, MEDLINE (Ovid), Embase (Ovid), ISI Web of Science, HTA, DARE, and LILACS up to 15 February 2021. We handsearched the reference lists of all included studies and other relevant publications and contacted experts in the field to identify additional studies or unpublished data.

SELECTION CRITERIA

We included studies assessing DUS accuracy against an acceptable reference standard (DSA, MRA, or CTA) in symptomatic patients. We considered the classification of carotid stenosis with DUS defined with validated duplex velocity criteria, and the NASCET criteria for carotid stenosis measures on DSA, MRA, and CTA. We excluded studies that included < 70% of symptomatic patients; the time between the index test and the reference standard was longer than four weeks or not described, or that presented no objective criteria to estimate carotid stenosis.

DATA COLLECTION AND ANALYSIS

The review authors independently screened articles, extracted data, and assessed the risk of bias and applicability concerns using the QUADAS-2 domain list. We extracted data with an effort to complete a 2 × 2 table (true positives, true negatives, false positives, and false negatives) for each of the different categories of carotid stenosis and reference standards. We produced forest plots and summary receiver operating characteristic (ROC) plots to summarize the data. Where meta-analysis was possible, we used a bivariate meta-analysis model.

MAIN RESULTS

We identified 25,087 unique studies, of which 22 were deemed eligible for inclusion (4957 carotid arteries). The risk of bias varied considerably across the studies, and studies were generally of moderate to low quality. We narratively described the results without meta-analysis in seven studies in which the criteria used to determine stenosis were too different from the duplex velocity criteria proposed in our protocol or studies that provided insufficient data to complete a 2 × 2 table for at least in one category of stenosis. Nine studies (2770 carotid arteries) presented DUS versus DSA results for 70% to 99% carotid artery stenosis, and two (685 carotid arteries) presented results from DUS versus CTA in this category. Seven studies presented results for occlusion with DSA as the reference standard and three with CTA as the reference standard. Five studies compared DUS versus DSA for 50% to 99% carotid artery stenosis. Only one study presented results from 50% to 69% carotid artery stenosis. For DUS versus DSA, for < 50% carotid artery stenosis, the summary sensitivity was 0.63 (95% confidence interval [CI] 0.48 to 0.76) and the summary specificity was 0.99 (95% CI 0.96 to 0.99); for the 50% to 69% range, only one study was included and meta-analysis not performed; for the 50% to 99% range, the summary sensitivity was 0.97 (95% CI 0.95 to 0.98) and the summary specificity was 0.70 (95% CI 0.67 to 0.73); for the 70% to 99% range, the summary sensitivity was 0.85 (95% CI 0.77 to 0.91) and the summary specificity was 0.98 (95% CI 0.74 to 0.90); for occlusion, the summary sensitivity was 0.91 (95% CI 0.81 to 0.97) and the summary specificity was 0.95 (95% CI 0.76 to 0.99). For sensitivity analyses, excluding studies in which participants were selected based on the presence of occlusion on DUS had an impact on specificity: 0.98 (95% CI 0.97 to 0.99). For DUS versus CTA, we found two studies in the range of 70% to 99%; the sensitivity varied from 0.57 to 0.94 and the specificity varied from 0.87 to 0.98. For occlusion, the summary sensitivity was 0.95 (95% CI 0.80 to 0.99) and the summary specificity was 0.91 (95% CI 0.09 to 0.99). For DUS versus MRA, there was one study with results for 50% to 99% carotid artery stenosis, with a sensitivity of 0.88 (95% CI 0.70 to 0.98) and specificity of 0.60 (95% CI 0.15 to 0.95); in the 70% to 99% range, two studies were included, with sensitivity that varied from 0.54 to 0.99 and specificity that varied from 0.78 to 0.89. We could perform only a few of the proposed sensitivity analyses because of the small number of studies included.

AUTHORS' CONCLUSIONS

This review provides evidence that the diagnostic accuracy of DUS is high, especially at discriminating between the presence or absence of significant carotid artery stenosis (< 50% or 50% to 99%). This evidence, plus its less invasive nature, supports the early use of DUS for the detection of carotid artery stenosis. The accuracy for 70% to 99% carotid artery stenosis and occlusion is high. Clinicians should exercise caution when using DUS as the single preoperative diagnostic method, and the limitations should be considered. There was little evidence of the accuracy of DUS when compared with CTA or MRA. The results of this review should be interpreted with caution because they are based on studies of low methodological quality, mainly due to the patient selection method. Methodological problems in participant inclusion criteria from the studies discussed above apparently influenced an overestimated estimate of prevalence values. Most of the studies included failed to precisely describe inclusion criteria and previous testing. Future diagnostic accuracy studies should include direct comparisons of the various modalities of diagnostic tests (mainly DUS, CTA, and MRA) for carotid artery stenosis since DSA is no longer considered to be the best method for diagnosing carotid stenosis and less invasive tests are now used as reference standards in clinical practice. Also, for future studies, the participant inclusion criteria require careful attention.

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.

Acoustic shadowing impairs accurate characterization of stenosis in carotid ultrasound examinations

OBJECTIVE

Duplex ultrasonography (DUS) has been the mainstay for diagnosing carotid artery stenosis and is often the sole diagnostic modality used prior to intervention. Highly calcified plaque, however, results in an acoustic shadow (AcS) that obscures the vessel lumen and inhibits the sonographer's ability to obtain Doppler velocity measurements. It is unknown whether DUS can accurately determine the degree of carotid stenosis in these settings.

METHODS

From July 2012 to December 2013, all patients with AcS on DUS measuring ≥5 mm in the longitudinal axis were cross-referenced with multidetector computed tomographic angiography (MD-CTA) images of the neck to define the study population. After standardizing the MD-CTA windows, percent stenosis was determined by cross-sectional area reduction using two separate previously described methods based on North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST) criteria. DUS waveform parameters in the internal carotid artery near the AcS were then compared with these MD-CTA measurements to determine the accuracy of DUS in characterizing the severity of carotid stenosis.

RESULTS

During this period, 8517 DUS studies were performed at the Massachusetts General Hospital, 550 of which had AcS, for an incidence of 6.45%. There were 92 lesions with a concomitant MD-CTA; however, seven were excluded because of poor study quality, because ≥6 months had elapsed between DUS and MD-CTA, or because the patient had undergone carotid reconstruction between studies. Of the 85 remaining lesions, DUS characterized 17 as severe (peak systolic velocity [PSV] >250 cm/s), 31 as moderate (PSV = 151-250 cm/s), and 37 as mild (PSV ≤150 cm/s) stenoses using PSV criteria. PSV weakly correlated with CTA-NASCET (r = 0.361; P = .004) and CTA-ECST (r = 0.306; P = .004) percent stenosis. Using PSV >250 cm/s as the predictor of >70% stenosis, and a ≥70% cutoff by both CTA-ECST and CTA-NASCET methods as the reference measure, DUS sensitivity ranged from 22.7% to 32.5%, specificity from 89.4% to 91.1%, positive predictive value from 88.2% to 76.4%, and negative predictive value from 25% to 60.2%. A subgroup analysis of lesions identified as non-severe by DUS revealed that waveforms with lower deceleration were associated with severe stenosis on CTA.

CONCLUSIONS

In the presence of AcS, DUS alone is inadequate to accurately determine the degree of carotid stenosis with sensitivity, specificity, and negative predictive values far below that needed for clinical decision-making. MD-CTA may be necessary for improved characterization of plaque in these AcS lesions. Further studies are needed to determine DUS parameters that may identify patients who should undergo further evaluation with MD-CTA to characterize the true severity of the stenosis.

Perioperative evaluation of carotid endarterectomy by 3D-CT angiography with refined reconstruction: preliminary experience of CEA without conventional angiography

Three-dimensional CT angiography (3D-CTA) was employed for perioperative evaluation of carotid endarterectomy (CEA) as an alternative to conventional angiography. A total of 62 carotid arteries were examined before and after CEA, 26 with an early 3D-CT system and 36 with multidetector helical CT allowing sophisticated reconstruction by a personal workstation. In addition to patients who had undergone conventional angiography at other institutes, 10 subjects underwent CEA on the basis of 3D-CTA findings alone. The findings provided detailed information with an excellent view of carotid stenoses. Volume rendering images comprehensively visualized lesions and surrounding structures as well as calcifications, which were also well depicted by maximum intensity projection images. Evaluation of the cerebral circulation is one problem that still requires solution, although cerebral vessels were delineated by 3D-CTA. One patient experienced transient hemiparesis, but no significant permanent deficit. We conclude that 3D-CTA is a safe and accurate modality that is a practical alternative to conventional perioperative angiography.

Accuracy of Conventional plus Transoral Carotid Ultrasonography in Distinguishing Pseudo-Occlusion from Total Occlusion of the Internal Carotid Artery

BACKGROUND

To investigate the accuracy of conventional carotid ultrasonography (CCU) combined with transoral carotid ultrasonography (TOCU) for distinguishing pseudo-occlusion from total occlusion of the internal carotid artery (ICA).

METHODS

This study included 95 patients who were suspected of having an occlusion of the ICA on magnetic resonance angiography (MRA) and underwent both CCU and conventional digital subtraction angiography (DSA) in order to confirm the diagnosis. TOCU was also performed to observe the cervical portion of the ICA distal to the stenosis. We compared the ultrasonographic findings with the DSA findings.

RESULTS

Twelve of the 95 patients were defined as having an ICA pseudo-occlusion on DSA. On B-mode images with CCU color Doppler, slight residual flow signals in the ICA lumen were shown in 20 patients. Among them, 2 patients had a pulsed Doppler waveform of the distal ICA occlusion pattern. Among the remaining 18 patients, 4 had a pulsed Doppler waveform of the to and fro flow pattern, and 14 had a weak antegrade flow pattern in the ICA lumen. The conventional ultrasonographic method showed 100% sensitivity with 93% specificity for diagnosing an ICA pseudo-occlusion. The addition of TOCU findings increased the specificity to 98%. In 2 patients, who were overdiagnosed as having an ICA pseudo-occlusion even using TOCU, DSA revealed an occlusion of the ICA distal to the ophthalmic artery with a severe stenosis of the proximal ICA.

CONCLUSIONS

Using conventional and transoral carotid ultrasonography, an ICA pseudo-occlusion can be diagnosed with higher accuracy.

Contrast-Enhanced 3-D MRA in Decision Making for Carotid Endarterectomy: A 6-Year Experience

BACKGROUND

Systematic need for angiography in diagnosis of carotid artery stenosis and indication of surgical therapy is still debated. Noninvasive imaging techniques such as MR angiography (MRA) or CT angiography (CTA) offer an alternative to digital subtraction angiography (DSA) and are increasingly used in clinical practice. In this study, we present the radiological characteristics and clinical results of a series of patients operated on the basis of combined ultrasonography (US)/MRA.

METHODS

This observational study included all the patients consecutively operated for a carotid stenosis in our Department from October 1998 to December 2004. The applied MRA protocol had previously been established in a large correlation study with DSA. DSA was used only in case of discordance between US and MRA. The preoperative radiological information furnished by MRA was compared with intraoperative findings. The outcome of the operation was assessed according to ECST criteria.

RESULTS

Among 327 patients, preoperative MRA was performed in 278 (85%), DSA in 44 (13.5%) and CT angiography in 5 (1.5%). Most of DSA studies were performed as emergency for preparation of endovascular therapy or for reasons other than carotid stenosis. Eleven additional DSA (3.3%) complemented US/MRA, mostly because diverging diagnosis of subocclusion of ICA. No direct morbidity or intraoperative difficulty was related to preoperative MRA. Combined mortality/major morbidity rate was 0.9% (3 patients) and minor morbidity rate 5.5% (18 patients).

CONCLUSIONS

This observational study describes a well-established practice of carotid surgery and supports the exclusive use of non invasive diagnostic imaging for indicating and deciding the operation.

Safety and efficacy of carotid arteriography in vascular surgery practice

OBJECTIVE

Carotid arteriography (CA) is an important method of assessing carotid artery occlusive disease and is the best method of planning for carotid angioplasty and stent placement (CAS). This study compared the results of CA performed by vascular surgeons in a contemporary series against widely recognized interdisciplinary quality standards for this procedure. Although many vascular surgeons perform CA, there is a paucity of data about its safety, efficacy, and compliance with quality standards in vascular practice. The importance of quality CA will likely increase as CAS emerges to assume a broader clinical role.

METHOD

Carotid arteriograms performed by seven vascular surgeons at three institutions from September 2000 to May 2004 were reviewed. These results were compared with quality standards for the performance of CA.

RESULTS

Five hundred three carotid arteriograms were performed over 45 months. Indications for the procedure were extracranial cerebrovascular disease (86%), trauma (5%), and other conditions (9%). Indications for the procedure were appropriate in 100% of patients (as determined by guidelines document) and exceeded the recommended standard of appropriate indications in 99%. All procedures successfully provided the information required, exceeding the threshold of 98% for procedural success. Reversible neurologic deficits occurred in 0.6% (two transient ischemic attacks and one stroke) compared with the threshold of 2.5%. A permanent neurologic deficit occurred in 0.2% (1 patient) compared with the published guideline of 1% after carotid arteriography. Major non-neurologic complications occurred in 1.2% (6 patients), less than the standard of 2.0%.

CONCLUSIONS

The safety and efficacy of a contemporary series of CA performed in vascular surgery practice compared favorably with recognized interdisciplinary quality standards for this procedure. Ensuring safe and effective CA is likely to support the successful growth of CAS as a treatment option.

Carotid Endarterectomy: Experience in 5425 Cases

From 1992 to December 2002, 3967 patients (2619 males; 1348 females) with a mean age of 68.4A years (range 32-92) underwent 5425 carotid endarterectomy (CE) procedures at our institute. Neurological history was positive for stroke in 1130 cases (21%) and for transient ischemic attack (TIA) in 2121 cases (39%). In 2174 cases (40%) patients were neurologically asymptomatic or presented nonspecific symptoms. Our current clinical protocol has been designed to optimize resources and reduce complications. Some of the major features, along with the respective percentages in this series, are as follows. Duplex scanning was performed at a validated laboratory as the principal preoperative exam (86.9%). Locoregional anesthesia and neurological monitoring were performed during carotid cross-clamping (96.3%). Selective shunting was carried out with a Javid shunt (10.7%). The choice of surgical technique was made according to carotid anatomy and cerebral tolerance of cross-clamping. Those used were a standard technique (now abandoned, 12.1%), synthetic patching (46.4%), and eversion endarterectomy (41.5%). Intraoperative completion arteriography was routinely performed for eversion endarterectomy and only in dubious cases with other techniques. The option of staying in an postoperative intensive care unit (ICU) was available (selective use, 2%). In uncomplicated cases, early discharge (after 1.5 postoperative days) was considered safe. The overall perioperative mortality was 0.37% (20/5425). Causes of death were myocardial infarction in seven cases, ischemic stroke in six cases, hemorrhagic stroke in five cases, respiratory failure caused by cervical hematoma in one case, and wound infection in one case. Perioperative neurological morbidity was 1.31% (71/5425); there were 43 major and 28 minor strokes. In conclusion, CE is effective for stroke prevention when there is significant symptomatic and asymptomatic carotid stenosis, as low mortality and morbidity may be achieved in an experienced center. At our institute, the reduction of costs did not have negative consequences on the quality of the surgical care.

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.

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.

Role of conventional angiography in evaluation of patients with carotid artery stenosis demonstrated by Doppler ultrasound in general practice

BACKGROUND AND PURPOSE

Previous studies have suggested that patients with carotid stenosis who are candidates for endarterectomy can be effectively identified on the basis of carotid Doppler ultrasound alone. Before widespread acceptance of this policy, the accuracy of carotid Doppler ultrasound outside selected centers and clinical trials needs to be evaluated. We performed a 12-month prospective study to evaluate the accuracy of Doppler ultrasound in identifying patients for carotid intervention in general practice settings.

METHODS

Each patient referred to our endovascular service for diagnostic angiography to evaluate for carotid stenosis was interviewed and examined by a neurologist. Subjects consisted of symptomatic patients with >/=50% stenosis and asymptomatic patients with >/=60% stenosis by Doppler ultrasound. Information pertaining to demographic and cerebrovascular risk factors and the results of the carotid Doppler ultrasound were recorded. The severity of stenosis on angiograms was measured with North American Symptomatic Carotid Endarterectomy Trial criteria by a blinded observer. The results of both studies were compared to determine the relative accuracy of ultrasound results.

RESULTS

Of 130 patients (mean age, 69+/-8.8 years) who met Doppler ultrasound criteria, 22 (17%) and 8 patients (6%) were found to have 30% to 49% or <30% stenosis by angiography, respectively. The positive predictive value of carotid Doppler ultrasound for identifying appropriate symptomatic candidates for carotid intervention (angiographic stenosis >/=50%) was 80%, with a false-positive value of 20%. The positive predictive value of carotid Doppler ultrasound for identifying appropriate asymptomatic candidates for carotid intervention (angiographic stenosis >/=60%) was 59%, with a false-positive value of 41%. Carotid endarterectomy or angioplasty and stent placement were undertaken subsequently in 60 (46%) of the patients. In 94 patients who underwent cerebral angiography alone, no complications were observed.

CONCLUSIONS

The present accuracy of carotid Doppler ultrasound in general practice does not justify its use as the sole basis of selecting appropriate patients for carotid intervention. Given the relatively low rate of associated morbidity with present day techniques, additional confirmatory studies such as angiography should be performed in every patient before a decision regarding intervention is made.

Results of carotid endarterectomy performed with preoperative duplex ultrasound assessment alone

Contrast injection cerebral angiography has been considered for several decades the "gold-standard" technique for diagnosis and operative planning of carotid disease. More recently, however, an increasing number of institutions are using duplex ultrasound as the single independent preoperative test. The objective of this investigation was to evaluate the impact of the utilization of duplex ultrasonography as the only preoperative test on the outcome of the procedure. Between 1993 and 1996, the authors performed 1,149 carotid procedures. Duplex ultrasound as the only preoperative test was employed with increasing frequency in a total of 728 cases. In 1995 and 1996, a cerebral arteriogram was performed only if duplex ultrasound was technically inadequate or questionable or showed an atypical pattern of disease. During the 4 years analyzed in this study, the number of the procedures increased from 165 in 1993 to 412 in 1996. The thirty-day mortality rate was 0.43%, and neurologic morbidity was 1.65%. According to the year in which the procedure was performed, the mortality/morbidity rates were 1.2/2.4 in 1993, 0.52/2.08 in 1994, 0.26/1.57 in 1995, and 0.24/1.21 in 1996. Indication to perform an arteriogram became very selective in 1995. Regardless of these changes in the diagnostic work-up, some degree of reduction in both 30-day mortality and neurologic morbidity was recorded. Considering a cost of 724 European Currency Units (ECU) per arteriogram, 527,072 ECU were saved in this period. In the last 4 years, duplex ultrasound has replaced arteriography as the first-choice technique for preoperative assessment of carotid disease at the authors' institution. There was definitely no detrimental effect on the clinical results that, on the contrary, improved during the same period. This policy has allowed a significant reduction in the cost of the procedure and has most likely prevented several arteriography-related complications. The authors recommend this policy to all institutions in which accurate duplex ultrasound is available.

Carotid endarterectomy without angiography: a prospective randomised pilot study

OBJECTIVES

to determine whether duplex ultrasonography alone is an adequate examination prior to carotid endarterectomy.

DESIGN

prospective, randomised, single centre study.

MATERIAL AND METHODS

all patients with carotid bifurcation stenosis greater than 70% - based on duplex scanning - were randomised to arteriography followed by carotid surgery (Group A n=96) or carotid surgery alone (Group B n=90). Study endpoints were neurological complications or death occurring between the day of randomisation and until 30 days after surgery.

RESULTS

major neurological complications of death in 1 (1%) vs 3 (3.3%) patients in group A and B, respectively (n.s.). Minor neurological complications (only TIA) were observed in 0 and 3 (3.3%) patients, respectively.

CONCLUSIONS

complication rates were low in both groups and within the generally accepted rate after carotid surgery in asymptomatic and symptomatic patients.

Effect of contralateral disease on duplex measurements of internal carotid artery stenosis

BACKGROUND

Duplex ultrasonography is increasingly used as the sole method of imaging before carotid endarterectomy. This study investigated the measured degree of stenosis in the contralateral carotid artery before and after operation.

METHODS

Duplex-derived peak systolic velocity (PSV), end-diastolic velocity (EDV) and internal carotid artery/common carotid artery (ICA/CCA) velocity ratios were measured in the contralateral unoperated ICA before 131 consecutive unilateral endarterectomies and compared with preoperative angiographic findings. Three months later duplex scans were repeated to assess whether there had been any alteration in the severity of the stenosis in the contralateral unoperated artery.

RESULTS

Bilateral ICA disease (greater than 50 per cent stenosis) was present in 50 patients (38 per cent). Three months after operation, ultrasonography of the 105 unoperated, patent, contralateral arteries showed a decrease in mean(s.d.) PSV (1.21(0. 83) versus 1.07(0.69) m/s; P < 0.01) and EDV (0.41(0.29) versus 0. 35(0.24) m/s; P < 0.01). This resulted in 14 (42 per cent) of 33 patients with contralateral disease being downgraded to a less severe category of stenosis. Use of the ICA/CCA velocity ratio prevented overestimation in eight of the 14 patients, while preoperative angiography correctly classified 13 of the 14 patients.

CONCLUSION

Bilateral carotid artery disease can cause overestimation of the severity of stenosis by duplex ultrasonography if absolute velocity is used as the main criterion.

Artificial neural network analysis of common femoral artery Doppler shift signals: classification of proximal disease

The aim of this study was to apply artificial neural networks (ANNs) to the problem of the diagnosis of aorto-iliac arterial disease on the basis of the profile of the common femoral artery (CFA) Doppler flow velocity waveform. The maximum frequency envelopes obtained from the CFA of 180 subjects were used to create sets of training and testing vectors for a back-propagation ANN. The ANN had three outputs: one representing the absence of significant aorto-iliac disease (i.e., < 50% diameter stenosis), one representing the presence of a hemodynamically significant aorto-iliac stenosis (i.e., 50-99% stenosis), and the other representing the presence of an aorto-iliac occlusion. After training, the ANN correctly classified 80% of "no significant disease" testing data, 45% of "significant stenosis" data and 85% of "occlusion" data. This work, thus, demonstrated the ability of an ANN to identify the severity of aorto-iliac disease from the CFA waveform. Although the ANN outperformed standard univariate methods and visual classification of the data, it would appear that further work is needed to increase the accuracy of the ANN to a clinically acceptable standard.

New duplex ultrasound scan criteria for managing symptomatic 50% or greater carotid stenosis

PURPOSE

The North American Symptomatic Carotid Endarterectomy Trial (NASCET) showed that selected patients benefited from surgery when their carotid artery was 50% or more stenosed. This study assessed the accuracy of color-flow duplex ultrasound scanning (DUS) parameters to detect 50% or greater carotid artery stenosis and to determine the situations in which carotid endarterectomy (CEA) without angiography could be justified.

METHODS

From March 1, 1995, to December 1, 1995, all patients considered for CEA were studied with DUS and carotid angiography. Results of the two tests were blindly compared. DUS measurements of internal carotid artery (ICA) peak systolic velocity (PSV), end diastolic velocity, and ratio of the ICA to common carotid artery PSV (ICA/CCA) were subjected to receiver operator characteristic curve analysis to determine the most accurate criterion predicting 50% or greater angiographic stenosis. The criterion for identifying patients for CEA without angiography was selected from criteria with a high positive predictive value (PPV) and sensitivity.

RESULTS

A total of 188 carotid bifurcations were available for comparison. A PSV (ICA/CCA) of 2 or higher was the most accurate criterion for detection of 50% or greater stenosis, with an accuracy rate of 93% (sensitivity, 96%; specificity, 89%; PPV, 92%). A PSV (ICA/CCA) of 3.6 or higher was the best criterion for identifying candidates for CEA who had not undergone earlier angiography, with PPV, sensitivity, specificity, and accuracy rates of 98%, 77%, 98%, and 86%, respectively.

CONCLUSION

These redefined criteria detect the NASCET-defined threshold level of 50% or greater ICA stenosis, above which CEA results in stroke reduction. A management algorithm based on these criteria should help to minimize both angiography and unnecessary intervention.

Vascular surgery without arteriography: use of Duplex ultrasound

Although contrast arteriography has served as the historical 'gold standard' for diagnosis of arterial disease, recent improvements in noninvasive diagnostic methods have made it possible to plan surgical treatment without subjecting patients to this invasive procedure. This approach avoids both the risks and costs associated with arteriography. Duplex scanning has become the standard noninvasive test for extracranial carotid artery disease, and it can also be used to directly evaluate the lower extremity arteries. In addition to the standard duplex criteria for classification of carotid stenosis, new criteria are available that reflect the stenosis thresholds identified in randomized clinical trials. Clinical experience has clearly shown that carotid endarterectomy can be performed safely based on the duplex scan alone in the majority of patients: however, arteriography is still indicated in selected cases. The evaluation of lower extremity arterial disease requires examination of multiple arterial segments, and most vascular surgeons still rely on the anatomic detail provided by arteriography for preoperative planning. Still, it may be possible to avoid formal preoperative arteriography in selected patients by using a combination of lower extremity duplex scanning and intraoperative arteriography. Further developments in noninvasive testing will continue to reduce the need for diagnostic arteriography prior to direct arterial surgery.

Computerized tomographic angiography scan following carotid endarterectomy

The purpose of this study was to evaluate the role of computed tomographic angiography (CTA) for postoperative assessment of carotid endarterectomy (CE). Twenty carotid endarterectomies were performed and controlled by using (1) intraoperative angiography, (2) postoperative duplex scanning and CTA with multiprojection volume reconstruction (MPVR). Intraoperative angiographic controls were deemed satisfactory for all patients. In 12 patients, the postoperative morphological aspect was satisfactory with CTA and duplex scanning. In the eight remaining patients, CTA and/or duplex scanning revealed 12 abnormalities: 3 were equally visualized on CTA and duplex scanning, 6 only on CTA and 3 only on duplex scanning. CTA is a rapid and noninvasive technique allowing the surgeon to get informative and comparative data. It might be an interesting alternative to postoperative angiography.

Predictive ability of duplex ultrasonography for internal carotid artery stenosis of 70%-99%: a comparative study

This study prospectively compared the accuracy of published duplex ultrasonographic criteria for 70%-99% internal carotid artery (ICA) stenosis according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method to determine angiographic stenosis. From March 1, 1995 to December 1, 1995, all patients considered for carotid endarterectomy (CEA) were studied with carotid duplex ultrasound and carotid angiography within 1 month of the ultrasound study. Duplex measurements of ICA peak systolic velocity (PSV), end diastolic velocity (EDV), and ratio of the ICA to common carotid artery (CCA) PSVs were recorded. Degree of stenosis on angiography was determined using NASCET criteria. A MEDLINE search to identify duplex ultrasound criteria to predict NASCET defined 70%-99% ICA stenosis was carried out. In addition, the original University of Washington criteria for critical stenosis (> or = 80%) was also examined. The accuracy of these criteria was determined with angiographic results and the positive predictive value (PPV) of each criterion were compared. Ninety-nine patients with 185 carotid bifurcations were available for comparison. The different duplex criteria for determining NASCET defined 70%-99% ICA stenosis were: ICA PSV > 175 cm/sec or PSV < 40 cm/sec, PSV > 230 cm/sec, ratio of ICA to CCA PSVs > 4, PSV > 130 cm/sec plus EDV > 100 cm/sec, and PSV > 270 cm/sec plus EDV > 110 cm/sec. When compared with angiography, the calculated PPVs for these criteria were 71% (73/103), 81% (71/88), 86% (67/78), 88% (62/70), and 90% (57/63), respectively. The University of Washington criteria for critical stenosis (PSV > 125 cm/sec plus EDV > 135 cm/sec) had the highest PPV at 91.6% (55/60). The University of Washington criteria for critical stenosis had the highest PPV to predict a 70%-99% angiographic stenosis.

A brief history of Doppler ultrasound in the diagnosis of peripheral vascular disease

The history of Doppler ultrasound in peripheral vascular diagnosis is considered in terms of basic developments, clinical applications and impact on medical practice. Many early developments occurred at Osaka University in Japan and the University of Washington in the United States. Through progressive steps, Doppler ultrasound technology has provided clinical applications in blood-flow sensing, waveform analysis, localizing blood flow and two-dimensional (2-D) mapping of blood flow. An important advance was the development of duplex and color Doppler scanning. Real time velocity measurements and flow mapping have led to many clinical applications. Two important applications have been detection and grading of atherosclerotic plaques in the internal carotid artery and the diagnosis of deep venous thrombosis. Doppler ultrasound is the preferred noninvasive imaging method for each of these clinical problems. The recent reaffirmation of carotid endarterectomy as the appropriate management for certain categories of carotid atherosclerotic occlusive disease has led to guidelines for selecting patients for carotid endarterectomy. New Doppler ultrasound criteria are being developed to identify categories of stenosis that relate to these guidelines. The establishment of Doppler ultrasound has led to training programs for technologists and physicians, certification of technologists and establishment of standards and quality control measures for vascular laboratories.

Can duplex ultrasonography select appropriate patients for carotid endarterectomy?

OBJECTIVES

This study investigated the reliability of carotid duplex ultrasound (DUS) to identify appropriate candidates for carotid endarterectomy (CEA) according to a panel of vascular specialists.

DESIGN

Prospective study.

MATERIAL

102 patients with 145 carotid bifurcation stenosis or occlusions.

METHODS

All patients who required a carotid angiogram were evaluated using DUS followed by carotid angiography. A blinded panel of four vascular specialists individually decided whether CEA would be appropriate for each patient based on pre-angiographic information. Angiograms were then shown to panelists to see if their management decision was altered by the angiogram.

RESULTS

For stenosis > or = 80% on DUS (n = 60), panelists unanimously agreed on CEA without angiography in 57 lesions. In 50 lesions (87.7%), angiography showed > or = 70% stenosis and the management plan remained unchanged. For the other seven lesions, intracranial aneurysms (n = 2), tandem intracranial lesion (n = 1), unsuspected proximal common carotid lesion (n = 1), a 40% stenotic lesion (n = 1), and high carotid bifurcations (n = 2) were seen. In lesions with 50-79% stenosis on DUS (n = 66), none of the panelists recommended CEA without prior angiography. Eighteen (27%) of these lesions were > or = 70% stenosed on angiogram. Complications of angiograms included one stroke, one haematoma, and one severe allergic reaction.

CONCLUSION

Carotid duplex ultrasonography without angiography can reliably select lesions appropriate for surgery only when critical stenosis > or = 80% is chosen. Routine angiography is recommended for carotid stenosis of 50-79% when CEA is considered.

Safe and cost-effective approach to carotid surgery

OBJECTIVE

To evaluate the safety and cost effectiveness of carotid surgery performed altering the perioperative protocol in an attempt to decrease resource utilisation.

SETTING

Department of vascular surgery in a large metropolitan teaching hospital in northern Italy.

DESIGN

Prospective, non-selective study.

MATERIALS AND METHODS

Three hundred and eighty carotid procedures were performed in 1995 on 343 patients (274 males, 69 females, mean age 68.2 years, range 47-86 years). The most important cost containment measures, were: (i) limiting the use of contrast arteriography to cases of dubious ultrasonographic diagnosis; (ii) routine use of loco-regional anaesthesia; (iii) postoperative admission to an intensive care unit (ICU) only in selected cases; (iv) early postoperative discharge where possible.

RESULTS

Mortality was 0.26% and neurological morbidity 1.58%. General anaesthesia was required in eight patients (2.1%), and only seven patients (1.8%) were admitted postoperatively to the ICU. Arteriography was performed in 56 cases (14.7%). The average hospital stay was 5 days with a global cost of 43,036 ECU, as compared with a cost of 6764 ECU for patients treated traditionally with routine arteriography, general anaesthesia and routine ICU admission.

CONCLUSIONS

Selective use of arteriography and ICU, routine use of loco-regional anaesthesia and reduced hospital stay make it possible to lower the cost of carotid surgery without sacrificing quality.

Preoperative testing before carotid endarterectomy: a survey of vascular surgeons' attitudes

Traditional surgical practice and published consensus statements from major vascular surgery specialty societies have considered contrast arteriography to be a routine part of the diagnostic evaluation prior to carotid endarterectomy (CEA). However, some surgeons now omit routine preoperative arteriography if a technically adequate carotid duplex scan is performed and indications for CEA are clear. To better establish current practice patterns and to characterize vascular surgeons' opinions about the role of preoperative arteriography, the Peripheral Vascular Surgery Society membership was surveyed by mail. Eighty-six percent of the members responded (430 of 502). Ninety-three percent of all patients considered for CEA are evaluated with duplex scanning; 82% with arteriography. While the majority of surgeons typically obtain both a duplex scan and an arteriogram, 70% have performed CEA without a preoperative arteriogram. Brain imaging studies (CT or MRI) are obtained in 26% and MR angiograms in 10% of cases. Seventy-five percent of the surgeons agreed with the statement that CEA without preoperative arteriography is an acceptable practice if appropriate indications for surgery are present. Furthermore, one third believed that CEA without a preoperative arteriogram is generally acceptable (acceptable more than half the time). Respondents were stratified by surgical experience time in practice and practice type. No significant differences in responses were found, suggesting the acceptance of CEA without preoperative arteriography is broad-based. This survey demonstrates changing attitudes among practicing vascular surgeons regarding the necessity for routine arteriography prior to CEA. Carotid endarterectomy on the basis of duplex scanning and clinical assessment should be considered an accepted alternative.

Duplex ultrasound criteria for the identification of carotid stenosis should be laboratory specific

BACKGROUND AND PURPOSE

Published criteria for the determination of carotid stenosis have been widely applied by vascular laboratories. We compared two vascular laboratories and their duplex ultrasound (DU) machines in terms of their overall diagnostic performance and the optimal criteria to identify patients who have a 70% to 99% stenosis of the internal carotid artery.

METHODS

Measurements of stenosis by DU and angiography were compared for 123 carotid arteries (60 arteries, laboratory A; 63 arteries, laboratory B). Receiver operating characteristic (ROC) curves were created, and the areas under the ROC curves and the optimal criteria for determining a 70% to 99% stenosis were compared. Multiple regression analysis was used to measure the effect of laboratory on the relationship between angiographic stenosis and DU velocity parameters.

RESULTS

Areas under the ROC curves were similar for both laboratories (0.89 to 0.90, laboratory A; 0.90 to 0.92, laboratory B). However, the optimal criterion for the identification of a 70% to 99% carotid stenosis was different for each laboratory. For most velocity parameters, based on regression analyses, the predicted percent angiographic stenosis for laboratory A was significantly greater than that for laboratory B. In addition, performance differed between the laboratories when established criteria from the literature were applied.

CONCLUSIONS

Two vascular laboratories with similar diagnostic accuracy by ROC analysis have markedly different "optimal" DU criteria. For a given angiographic stenosis, velocities in one laboratory were consistently greater than those in the other laboratory. Laboratory-specific criteria rather than published criteria should be used to identify patients with internal carotid artery stenoses.

The practice of carotid endarterectomy in Australasia

BACKGROUND

Carotid endarterectomy (CEA) is a frequently performed surgical procedure and there are variations in the preoperative, operative and postoperative management related to this operation.

METHODS

Questionnaires were sent to all 191 members of the Division of Vascular Surgery, Royal Australasian College of Surgeons, and the Australasian Chapter of the International Society of Cardiovascular Surgery.

RESULTS

The questionnaire was returned by 179 surgeons (94%). One hundred and fifty-nine were vascular surgeons, of whom 139 perform CEA. Most surgeons reported performing more CEA than 5 years previously. Surgery for asymptomatic carotid stenosis was performed by 78% of surgeons at the time of the survey. Routine carotid angiography is performed pre-operatively for symptomatic patients by 61% of surgeons and for asymptomatic patients by 56%. Intra-operative shunting is used routinely by 37% of surgeons, selectively by 58% and never by 5%. Arteriotomy patch closure is performed routinely by 16%, usually by 30%, rarely by 52% and never by 3%. The favoured patch material is Dacron 39%, PTFE 19%, ankle long saphenous vein (LSV) 22%, thigh LSV 18% or other materials 2%. Compared to their practice 5 years previously, arterial patch closure is used more often by 42% of surgeons, the same by 51% and less by 7%. Postoperatively, patients are nursed mainly in intensive care (34%) or a high-dependency unit (33%).

CONCLUSIONS

The practice of CEA by Australasian vascular surgeons reflects the recent trends reported in the world literature. Most Australasian surgeons perform CEA for asymptomatic disease. Forty per cent are performing CEA on the basis of duplex scanning alone. There is a trend towards increased use of patch closure. Most patients are managed in intensive care or high-dependency units.

Neural network analysis of Doppler ultrasound blood flow signals: a pilot study

It has been hypothesised that each artery in the human body has its own characteristic "signature" -a unique Doppler flow profile which can identify the artery and which may also be modified by the presence of disease. To test this hypothesis an artificial neural network (ANN) was trained to recognise three groups of maximum frequency envelopes derived from Doppler ultrasound spectrograms; these were the common carotid, common femoral and popliteal arteries. Data were collected from 24 subjects known to have no significant atheromatous disease. The maximum frequency envelopes were used to create sets of training and testing vectors for a backpropagation ANN. The ANN demonstrated a high success rate for appropriate classification of the test vectors: 100% for the carotid; 92% for the femoral; and 96% for the popliteal artery. This work has demonstrated the ability of the ANN to differentiate accurately between different and similar flow profiles, outlining the potential of this technology to identify subtle changes induced by the onset of arterial disease within a specific vessel. It should be noted that the ANN not only models the maximum frequency envelope but also, unlike standard indices, makes a decision as to which artery the maximum frequency envelope belongs to, thus providing the potential to obviate human subjective classification.

Magnetic resonance angiography of the aortic arch

Duplex ultrasound and magnetic resonance angiographic (MRA) studies are the principal noninvasive methods for evaluation of extracranial occlusive disease in patients at risk for stroke, but each has limited ability to diagnose aortic arch and arch vessel disease. Recent favorable reports of the nonnephrotoxic contrast agent Gadolinium (Gd) being used to enhance MRA images of the abdominal aorta prompted us to examine its utility for the aortic arch vessels. Prospectively, 28 patients with suspected carotid or arch vessel disease were imaged by contrast arteriographic examination and MRA + Gd of the aortic arch within 30 days of each other. One (for contrast arteriograms) or two (for MRA) blinded readers measured stenoses with the contrast arteriograms as the standard. A total of 196 arch vessels containing 58 stenoses and four occlusions (by arteriogram) were examined with each method. Interobserver agreement for interpretation of MRA studies was substantial (kappa = 0.68). MRA detected all anatomic anomalies (e.g., bovine arch). The correlation of MRA with arteriographic scans for arch vessel stenoses > 50% was sensitivity, 73% (readers 1 and 2); specificity, 98% (reader 1), 89% (reader 2); positive predictive value, 73% (reader 1), 89% (reader 2); negative predictive value, 98% (readers 1 and 2); accuracy, 97% (reader 1), 98% (reader 2). MRA + Gd is an accurate new noninvasive imaging method for detection of significant aortic arch disease. In its current state of development, however, it cannot obviate the need for contrast arteriographic examination.

An analysis of perioperative surgical mortality and morbidity in the asymptomatic carotid atherosclerosis study. ACAS Investigators. Asymptomatic Carotid Atherosclerosis Study

BACKGROUND AND PURPOSE

Our aim was to determine the perioperative morbidity and mortality rates of patients in the surgical arm of the multi-institutional, prospective, randomized Asymptomatic Carotid Atherosclerosis Study (ACAS).

METHODS

Of 828 patients with carotid stenosis of 60% or more randomized to the surgical arm of ACAS, 721 underwent carotid endarterectomy (CEA). To qualify for participation, surgeons were required to have performed at least 12 CEAs per year with a combined neurological morbidity and mortality rate no greater than 3% for asymptomatic patients and 5% for symptomatic patients. Clinical centers had to demonstrate arteriographic morbidity less than 1% and mortality less than 0.1% per year. Primary events were stroke and death in the period between randomization and 30 days after surgery; secondary events were transient ischemic attack and myocardial infarction occurring in the same period.

RESULTS

Of the 721 patients who underwent CEA, 1 died and 10 others had strokes within 30 days (1.5%). Of the 415 who underwent arteriography after randomization but before CEA, 5 (1.2%) suffered transient ischemic attack or stroke caused by arteriography. Thus, a nearly equal risk of stroke was associated with both CEA and carotid arteriography. In addition, 6 transient ischemic attacks and 3 myocardial infarctions could be directly linked to CEA, for a total CEA event rate of 2.6%.

CONCLUSIONS

Patients with asymptomatic internal carotid artery stenosis exceeding 60% reduction in diameter who are acceptable candidates for elective operation may be considered for CEA if the combined arteriographic and surgical complication rates are 3% or less.

Accuracy of duplex sonography before carotid endarterectomy--a comparison with angiography

OBJECTIVES

The aim of this prospective study was to contribute to the evaluation of the reliability of Duplex sonography (DS) before carotid endarterectomy (CEA).

DESIGN

The study was performed prospectively in a university hospital setting.

METHODS

Eighty-one consecutive patients aged 49-83 years were examined with DS and carotid angiography (CAG) before CEA. The results of the DS were judged as either confident, or CAG was assessed to be necessary preoperatively. The results from the DS and the CAG were then compared.

RESULTS

DS was judged as confident in 148 of the 162 arteries examined. In none of these 148 arteries did CAG change patient management in any way, and the agreement between DS and CAG was good. In the remaining 14 arteries CAG was judged necessary, in 11 arteries because DS assessed the internal carotid artery (ICA) as occluded, which was confirmed by CAG in 10 arteries. In three arteries the reason was poor quality of the DS, however these three arteries were correctly assessed as severely diseased.

CONCLUSIONS

This study confirms that DS alone is sufficient in the preoperative evaluation before CEA, provided that CAG is performed whenever DS shows occlusion of the ICA, or when the quality of the DS is poor.

Carotid endarterectomy without angiography

Between 1 January 1990 and 1 September 1994 a total of 109 carotid endarterectomies were performed without preoperative angiography. Only two cases were considered by the surgeon to have a poor correlation between the duplex examination results and intraoperative findings; the outcome was good in both. The perioperative mortality rate was 1.8 per cent, one patient dying from sudden haematoma causing asphyxia and the other from unrelated causes following a myocardial revascularization procedure. Two non-disabling strokes also occurred. These results suggest that carotid endarterectomy based on carotid duplex scanning alone without preoperative angiography is safe in selected patients.

Corotid endarterectomy for symptomatic carotid artery disease demonstrated by duplex ultrasound with minimal arteriographic findings

Ulcerated or irregular heterogeneous carotid plaque as seen by duplex ultrasound can cause hemispheric transient ischemic attacks (TIAs) and/or a cerebrovascular accident, even if only associated with nonsignificant carotid stenosis on arteriography. The purpose of this study was to review our experience in patients who underwent a carotid endarterectomy after medical treatment had failed, based on pathologic findings detected by carotid duplex ultrasound with minimal disease on arteriography. The medical records of 14 patients who underwent carotid endarterectomy for TIA symptoms related to ulcerated or irregular heterogeneous plaques were analyzed. All had had preoperative carotid duplex ultrasound, arteriography, and cardiac and neurologic workups to rule out other causes for their TIAs. Medical treatment had failed in all of them. There were 10 men and four women whose median age was 68 years. Carotid duplex ultrasound showed irregular heterogeneous carotid plaque in all patients associated with 20% to 50% stenosis in 12 and approximately 50% to 60% stenosis in two. All had normal to < 20% stenosis on arteriograms. The duplex ultrasound findings were all confirmed at operation. All had an uneventful postoperative course with relief of symptoms. Carotid duplex ultrasound is superior to carotid arteriography in detecting irregular or ulcerative heterogeneous plaque associated with nonsignificant stenosis. Carotid duplex ultrasound can be used to determine the desirability of carotid endarterectomy after failed medical treatment in patients with classical and persistent TIA symptoms despite normal or minimal disease on arteriograms. A successful endarterectomy appears to predict an asymptomatic postoperative course.

The relative contributions of carotid duplex scanning, magnetic resonance angiography, and cerebral arteriography to clinical decisionmaking: a prospective study in patients with carotid occlusive disease

PURPOSE

Recent reports suggest that 80% to 90% of patients can safely undergo carotid endarterectomy on the basis of duplex scanning alone without cerebral angiography. Other investigators have recommended that a complementary imaging study such as magnetic resonance angiography (MRA) also be obtained.

METHODS

We prospectively evaluated 103 consecutive patients with carotid occlusive disease. Eighty percent of patients were symptomatic. All 103 patients underwent duplex scanning and arteriography. Additional noninvasive tests included computed tomography, magnetic resonance imaging, and MRA in 50%, 56%, and 48% of patients, respectively. At a multispecialty conference all studies except angiograms were reviewed, and a treatment decision was made by a panel of attending vascular surgeons, neurosurgeons, and neurologists. The cerebral angiograms then were reviewed and changes made to final treatment plans were noted.

RESULTS

After review of noninvasive studies, 30 of 103 of patients (29%) were believed to require arteriography because of diagnostic uncertainty of carotid occlusion in three patients, suggestion of nonatherosclerotic disease in four, suggestion of proximal disease in two, suboptimal noninvasive studies in one, and uncertainty of therapy despite good-quality noninvasive studies in 20 patients primarily with borderline stenoses and unclear symptoms. In 10 of these 30 patients (33%) management decisions were changed on the basis of angiogram results. Of the remaining 73 patients (71%) in whom the panel felt comfortable proceeding with operative or medical therapy without angiography, only one patient (1.4%) would have had management altered by results of angiography. MRA results concurred with duplex findings in 92% of studies, but did not alter management in any patient.

CONCLUSIONS

In patients with good-quality duplex images, focal atherosclerotic bifurcation disease, and clear clinical presentation, treatment decisions can be made without arteriography. In 30% of patients angiography is useful in clarifying decisionmaking. MRA is unlikely to influence management decisions and is thus rarely indicated.

A critical analysis of cerebral computed tomography scanning before elective carotid endarterectomy and its correlation to carotid stenosis

BACKGROUND

Cerebral computed tomography (CT) scanning has been suggested to play a role in the management of patients before carotid endarterectomy (CEA). This prospective study analyzes the value of CT scanning before elective CEA and the correlation of CT findings to significant carotid stenosis.

METHODS

This study includes 131 consecutive patients considered for CEA during a 2-year period. All patients underwent carotid duplex ultrasonography, carotid arteriography, and CT scanning.

RESULTS

Eighty patients (61%) had transient ischemic attacks or prior strokes, and 51 (39%) had nonhemispheric symptoms or were asymptomatic. The CT scan was abnormal in 36 (27%) patients; however, no brain tumors or abnormalities to affect clinical management were revealed. Ninety-two CEAs were performed on 87 patients. Twenty-nine (32%) in the operative group had abnormal CT scans, but these did not influence operative decisions. On the basis of this rate of 0% of patients with CT findings to change surgical management in 92 cases, a maximum true rate of occurrence of up to 5% could be detected with alpha equals 0.05 by sampling a population of this size. Four patients (4%) had postoperative cerebral vascular accidents, and all of these had normal preoperative scans. Patients with 50% or more carotid stenosis on arteriogram were significantly more likely to have abnormal CT scans than patients with less than 50% stenosis (20% versus 7%, p = 0.0034). As carotid stenosis became more significant, the frequency of abnormal CT scans increased (p < 0.01). The cost of CT scanning was $66,089.50 in this study.

CONCLUSIONS

Significant carotid stenosis was associated with a higher frequency of abnormal CT scans; however, routine preoperative CT scanning was unnecessary before elective CEA.

Carotid endarterectomy in asymptomatic patients--is contrast angiography necessary? A morbidity analysis

PURPOSE

Findings from the Asymptomatic Carotid Atherosclerosis Study (ACAS) indicate that carotid endarterectomy can be beneficial in symptom-free patients with 60% to 99% carotid artery stenosis. However, patients in ACAS who underwent contrast angiography (CA) before carotid endarterectomy were exposed to an additional 1.2% risk of stroke.

METHODS

We used the methods of decision analysis to assess whether the overall 5-year stroke risk in symptom-free patients with suspected carotid artery disease can be reduced by preoperative imaging with magnetic resonance angiography (MRA) or duplex ultrasonography (DU). We compared four strategies for the preoperative evaluation of carotid artery stenosis in symptom-free patients: 1) CA alone, 2) MRA alone, 3) DU alone, and 4) MRA and DU with CA when the results of these tests disagree. Accuracies of MRA and DU were estimated from 81 patients exposed to all three procedures; stroke risks for patients with 60% to 99% carotid artery stenosis were obtained from ACAS.

RESULTS

For predicting 60% to 99% carotid stenoses, sensitivity and specificity for noninvasive tests, optimized to reduce morbidity, were as follows: DU (0.96, 0.66), MRA (1.00, 0.76), DU/MRA (1.00, 0.86; 26% would require CA). The 5-year stroke risk of these four strategies in order of decreasing benefit was MRA, 6.17%; MRA/DU, 6.34%; DU, 6.35%; and CA, 7.12%. In sensitivity analyses, noninvasive tests were advantageous even if the stroke rate with CA diminished to 0.4%, or if the sensitivity and specificity of noninvasive tests fell to 70%.

CONCLUSION

The preoperative use of noninvasive tests resulted in a lower 5-year stroke risk compared with CA in symptom-free patients with suspected carotid artery stenosis.

Carotid endarterectomy--when to do it, how to do it?

With the completion of the major carotid endarterectomy trials the indications for this procedure can be defined. The procedure, if done by experienced teams, has been shown to improve the chance of stroke free survival in symptomatic and asymptomatic patients with a high-grade stenosis of the internal carotid artery. In asymptomatic patients the risk reduction gained by prophylactic carotid endarterectomy may be small in relation to the risk of coincident factors particularly coronary artery disease. The benefit gained by carotid endarterectomy depends closely on the risk of the procedure itself, and a single little flaw during the management can annulate the benefit of the operation in asymptomatic patients. There are still considerable controversies with regard to peri-operative management and surgical technique, e.g., the necessity of routine pre-operative arteriography has recently been questioned. Quality control programmes become a requirement with the publication of performance standards for carotid endarterectomy. According to a consensus of the American Heart Association, the surgical morbidity/mortality must be less than 6% for symptomatic carotid lesions and less than 3% for asymptomatic lesions. The present review discusses the steps of the pre-operative work-up, the procedure itself and the post-operative management with the aim to identify accepted safety standards as well as areas of uncertainty.

Cost-effective carotid endarterectomy in community practice

The purpose of this study was to compare hospital charges for carotid endarterectomy on a surgeon-specific basis. The cost of carotid endarterectomy is influenced by preoperative evaluation, operating time, use of the intensive care unit, length of hospital stay, and surgical results. Length of stay and average hospital charges for 18 doctors performing 344 carotid endarterectomies at three hospitals were analyzed. Outcome data were also reviewed. The results demonstrated a wide variation in hospital charges among surgeons. Surgeons using the most cost-effective measures achieved comparable or superior outcomes. In an era of managed care, severe cost constraints mandate that surgeons perform similar studies in their own communities so that cost-effective clinical pathways can be developed. With the use of appropriate guidelines, carotid endarterectomy can be performed at relatively low cost without sacrificing quality.

Carotid artery stenosis: preoperative noninvasive evaluation in a community hospital

PURPOSE

The purpose of this study was to determine whether noninvasive evaluation with duplex ultrasonography and magnetic resonance angiography of patients with carotid artery stenosis can replace contrast angiography at our institution.

METHODS

This study consisted of a retrospective chart review of 40 patients (74 carotid arteries) in combination with a blinded reanalysis of original data. Contrast angiography was compared with duplex ultrasonography and magnetic resonance angiography. The overall diagnostic accuracy of duplex ultrasonography and magnetic resonance angiography was determined individually and concordantly in patients being evaluated for carotid artery stenosis.

RESULTS

The overall sensitivity of duplex ultrasonography was 88.5%, and the specificity was 91.7% (Spearman correlation coefficient = 0.8456; p < 0.001). For magnetic resonance angiography the sensitivity was 92.3%, and the specificity was 97.9% (Spearman correlation coefficient = 0.9086; p < 0.001). In the presence of concordance, the noninvasive studies exhibited a sensitivity of 100%, (correlation coefficient = 0.9661; kappa value = 0.9655). No occlusions or severe lesions were missed by both studies. In only one vessel (1.52%) was a false-positive concordance noted.

CONCLUSIONS

Carotid endarterectomy may be undertaken with a high degree of confidence that the operation will be appropriate if the noninvasive evaluations are concordant. In the absence of concordance of the noninvasive studies, contrast angiography should be considered.

Distinguishing carotid artery pseudo-occlusion with color-flow Doppler

BACKGROUND AND PURPOSE

This study was undertaken to determine the impact of color-flow Doppler on the accuracy of noninvasive carotid imaging for distinguishing an internal carotid artery pseudo-occlusion (string sign) from a complete occlusion.

METHODS

From January 1985 to January 1994, review of noninvasive vascular studies, arteriograms, and operative reports of 26 consecutive patients undergoing 27 carotid endarterectomies for carotid pseudo-occlusion was performed. Further review was conducted of all patients identified with carotid occlusion by noninvasive testing who underwent confirmatory arteriography during the same interval.

RESULTS

Conventional gray-scale duplex scanning (January 1985 to December 1989) correctly identified 3 of 11 (27%) pseudo-occluded internal carotid arteries compared with 15 of 16 (94%) internal carotid artery pseudo-occlusions correctly identified by color-flow Doppler (January 1990 to June 1994) (P < .01). Similarly, carotid occlusion was more accurately identified by color-flow Doppler (33 of 33, 100%) compared with gray-scale duplex scanning (19 of 27, 90%) (P < .01).

CONCLUSIONS

The addition of color-flow Doppler to the duplex evaluation of the extracranial carotid circulation improves the accuracy of distinguishing carotid pseudo-occlusion from the occluded internal carotid artery and may obviate the need for arteriography to identify patients with this critical level of carotid stenosis.