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.

Practice patterns of carotid endarterectomy as performed by different surgical specialties at a single institution and the effect on perioperative stroke and cost of preoperative imaging

BACKGROUND

Carotid endarterectomy (CEA) is currently performed by various surgical specialties with varying outcomes. This study analyzes different surgical practice patterns and their effect on perioperative stroke and cost.

METHODS

This is a retrospective analysis of prospectively collected data of 1000 consecutive CEAs performed at our institution by three different specialties: general surgeons (GS), cardiothoracic surgeons (CTS), and vascular surgeons (VS).

RESULTS

VS did 474 CEAs, CTS did 404, and GS did 122. VS tended to operate more often on symptomatic patients than CTS and GS: 40% vs 23% and 31%, respectively (P < .0001). Preoperative workups were significantly different between specialties: duplex ultrasound (DUS) only in 66%, 30%, and 18%; DUS and computed tomography angiography in 27%, 35%, and 29%; and DUS and magnetic resonance angiography in 6%, 35%, and 52% for VS, CTS, and GS, respectively (P < .001). The mean preoperative carotid stenosis was not significantly different between the specialties. The mean heparin dosage was 5168, 7522, and 5331 units (P = .0001) and protamine was used in 0.2%, 19%, and 8% (P < .0001) for VS, CTS, and GS, respectively. VS more often used postoperative drains; however, no association was found between heparin dosage, protamine, and drain use and postoperative bleeding. Patching was used in 99%, 93%, and 76% (P < .0001) for VS, CTS, and GS, respectively. Bovine pericardial patches were used more often by CTS and ACUSEAL (Gore-Tex; W. L. Gore and Associates, Flagstaff, Ariz) patches were used more often by GS (P < .0001). The perioperative stroke/death rates were 1.3% for VS and 3.1% for CTS and GS combined (P = .055); and were 0.7% for VS and 3% for CTS and GS combined for asymptomatic patients (P < .034). Perioperative stroke rates for patients who had preoperative DUS only were 0.9% vs 3.3% for patients who had extra imaging (computed tomography angiography/magnetic resonance angiography; P = .009); and were 0.9% vs 3% for asymptomatic patients (P = .05). When applying hospital billing charges for preoperative imaging workups (cost of DUS only vs DUS and other imaging), the VS practice pattern would have saved $1180 per CEA over CTS and GS practice patterns; a total savings of $1,180,000 in this series.

CONCLUSIONS

CEA practice patterns differ between specialties. Although the cost was higher for non-VS practices, the perioperative stroke/death rate was somewhat higher. Therefore, educating physicians who perform CEAs on cost-saving measures may be appropriate.

Duplex Ultrasound Verified by Angiography in Patients with Severe Primary and Restenosis of Internal Carotid Artery

There are very limited data in the literature about the reliability of duplex ultrasound (DU) verified by angiography in patients with restenosis of the internal carotid artery (ICA) after carotid surgery compared with primary carotid artery stenosis patients. Our objective was to compare the reliability of DU verified by conventional angiography in the diagnosis of severe primary stenosis versus restenosis of ICA. One hundred thirty-four patients (238 arteries) were examined by both DU and angiography. Severe stenosis (>70%) was found in 47 primary stenotic arteries and in 70 restenotic arteries. Accuracy, specificity, sensitivity, positive predictive value (PPV), and negative predictive value were obtained for basic DU criteria after verification of ultrasound data by angiography. The best accuracy for detection of >70% stenosis by end diastolic velocity was found for the velocity of 70 cm/sec or more in both groups, but accuracy for the restenosis group was significantly higher (96.9% vs. 89.8%, p = 0.025). Additionally, specificity (p = 0.01) and PPV (p = 0.01) were significantly higher in the restenosis group. The best accuracy for detection of >70% stenosis by peak systolic velocity was found for the velocity of 220 cm/sec or more for restenoses and 200 cm/sec or more for primary stenoses. The accuracy of the ultrasound was significantly higher in the restenosis group (94.6% vs. 87%, p = 0.04), as were specificity (p = 0.01) and PPV (p = 0.02). The diagnosis of severe restenosis by DU is reliable and can be used for decision making regarding surgery or stenting without angiography. In patients with Doppler parameters pointing to borderline moderate/severe primary carotid stenosis and technically complicated cases, angiography in addition to sonography before surgery is recommended.

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.

Is carotid duplex scanning sufficient as the sole investigation prior to carotid endarterectomy?

Carotid endarterectomy (CEA) is the accepted treatment for certain patients who have had, or who are at risk of having, a stroke if they have a significant narrowing of the internal carotid artery. Rapid and accurate classification of the degree of stenosis is important as the benefit of surgery is highly dependent on this. The aim of this study was to assess whether the addition of angiography to duplex scanning resulted in a change in patient management in a unit where duplex scanning was used as the sole imaging investigation prior to CEA. The study population consisted of 64 patients with significant internal carotid artery stenosis on duplex scanning who were suitable for, and wished to be considered for, CEA. All patients underwent an angiogram. In this study 9 (14%) patients did not proceed to surgery on the basis of angiography and in a further 11 (17%) patients insufficient views of the distal vessel were obtained on duplex scanning. Three of these patients had extensive disease which excluded surgery. One patient experienced a transient ischaemic attack (TIA) at the time of angiography. In conclusion, this audit has highlighted the limitations in performing duplex scanning alone, and the costs that this can incur on the patient who may undergo an unnecessary operation. We cannot recommend duplex scanning as the sole investigation prior to CEA. There is need to evaluate the role of additional non-invasive carotid imaging such as magnetic resonance angiography or CT angiography in the assessment of these patients.

Quantification of Internal Carotid Artery Stenosis with Duplex US: Comparative Analysis of Different Flow Velocity Criteria

PURPOSE

To compare 13 previously published sets of duplex ultrasonographic (US) criteria with the US criteria used at the authors' institution in terms of agreement with carotid artery angiographic results.

MATERIALS AND METHODS

The authors studied 1,006 carotid arteries in 503 patients at duplex US and angiography. The degree of stenosis was determined by using duplex flow US velocities and applying 13 previously published sets of criteria and the criteria used at the authors' institution. Two independent observers evaluated the angiograms according to North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria. kappa statistics, sensitivities, specificities, positive predictive values (PPVs), negative predictive values (NPVs), and generalized linear mixed regression models were used to assess agreement between duplex US and angiographic findings.

RESULTS

Stenoses of 0%-29%, 30%-49%, 50%-69%, 70%-99%, and 100% could be differentiated with 73% overall agreement between duplex US and angiographic findings according to flow velocity criteria (kappa = 0.57; 95% confidence interval [CI]: 0.54, 0.60); however, with duplex US, the angiographic degree of stenosis tended to be overestimated. In the differentiation of stenoses of less than 70%, only 45% agreement (kappa = 0.26; 95% CI: 0.23, 0.29) was observed, whereas in the differentiation of high-grade (> or =70%) stenoses, 96% agreement was observed (kappa = 0.85; 95% CI: 0.83, 0.87). The PPV and NPV for the identification of 70%-99% angiographic stenosis were 69% and 98%, respectively, with use of the most sensitive duplex US criteria.

CONCLUSION

Duplex US is an excellent examination to screen for high-grade carotid artery stenosis; however, it tends to lead to an overestimation of the degree of stenosis. Exclusion of 70%-99% angiographic stenosis can be achieved with a sensitivity of up to 98%.

Magnetic resonance angiography minimizes need for arteriography after inadequate carotid duplex ultrasound scanning

PURPOSE

We prospectively evaluated whether magnetic resonance angiography (MRA) enabled definition of cerebrovascular anatomy after indeterminate or inadequate results at duplex ultrasound scanning to facilitate patient selection for carotid endarterectomy (CEA) and for technical planning.

METHODS

After implementation of a protocol in October 1998 to minimize use of cerebral arteriography, MRA (arch/cervical two-dimensional and cranial three-dimensional time of flight technique) was performed in 138 consecutive patients with cerebrovascular occlusive disease and inconclusive duplex scans obtained by an ICAVL-approved laboratory. The ability of MRA to define anatomic features unresolved at duplex scanning was compared between categories of duplex scan inadequacies. Operative outcome was compared between patients requiring MRA before CEA (n = 66) and a concurrent cohort undergoing CEA on the basis of duplex scan results only (n = 69).

RESULTS

Incomplete imaging of the carotid bifurcation, because of high bifurcation, long (>3 cm) internal carotid artery (ICA) plaque, or calcific shadows, was the most common reason for inadequate duplex scans (n = 74, 53%), followed by borderline severe ICA disease (23.17%), suspected extracervical disease (supra-aortic trunk, vertebral, or intracranial, 22, 16%), ICA near- occlusion (12.9%), and diffuse recurrent stenosis (7.5%). MRA enabled resolution of duplex scan inadequacies in 95% of patients with disease confined to the carotid bifurcation, and 90% of all patients, but was least accurate for delineation of extracervical lesions (77%) and near-occlusions (75%). In 5 of 8 patients (6%) arteriography was performed to determine operability of ICA near-occlusion or extracervical lesions. Combined stroke and death rates after CEA were not statistically different (P =.3) between patients requiring MRA (3 of 66, 4.6%) and the concurrent group in whom MRA was performed solely on the basis of duplex results (1 of 69, 1.5%). However, intraoperative technical adjustments (anatomy that precluded shunt use, extended endarterectomy length, ICA shortening due to tortuosity) were planned in 71% of patients (12 of 17) with MRA-defined anatomy, but only 36% of patients (4 of 11) with long CEA on the basis of duplex results only (P =.08).

CONCLUSION

MRA replaces the need for cerebral arteriography in most patients after inadequate carotid duplex scanning. Delineation of cerebrovascular anatomy at MRA assists in determination of CEA candidacy and operative planning.

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.

Duplex ultrasound criteria for defining the severity of carotid stenosis

Duplex ultrasound scan (DUS) criteria for grading >50% carotid artery stenosis is typically divided into broad categories such as 50-79% stenosis, 80-99% stenosis, and occlusion. The purpose of this study is to validate DUS criteria for stratifying 50 to 100% carotid stenosis into 10% intervals using digital substraction cerebral angiography (DSCA) as the standard of comparison. Between 1996 and 2001, 163 patients were evaluated with duplex ultrasound and angiography. A total of 326 carotid arteries were studied using DUS in an accredited ICAVL vascular laboratory. Threshold velocity criteria for determining the degree of carotid stenosis was defined according to seven categories: <50%, 50-59%, 60-69%, 70-79%, 80-89%, 90-99%, and occlusion. Treatment decisions were based on the angiographic findings. In cases where the degree of stenosis as defined by duplex velocity criteria did not correlate with angiographically defined stenosis, each record was reviewed to determine whether the angiographic findings altered the surgeon's treatment decision. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for DUS-defined degree of stenosis as compared to angiographically defined stenosis were determined. There was a high correlation (R = 0.96) between duplex scan and angiography in 93% (302/326) of the cases. Clinical management was altered in only 3% (10/326) of the cases because of the results of angiography. The DUS velocity criteria to grade the severity of carotid disease in 10% intervals is reliable and accurate. Clinical management of patients with carotid stenosis can be based solely on carotid DUS in 97% of patients considered for treatment of carotid artery disease.

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%.

Carotid artery endarterectomy solely based on duplex scan findings

The purpose of this study was to review experience with carotid artery surgery based on findings obtained solely from duplex scanning with special regard to unexpected findings during surgery and the early outcome. From January 1993 through December 1999, 271 consecutive patients underwent 287 carotid endarterectomies (CEAs), 229 (80%) of which were performed solely based on duplex scan findings. During the study period 5,932 carotid artery duplex scans were performed in 4,466 patients. Of 589 patients with internal carotid artery (ICA) stenosis 70%, 246 underwent CEA compared to 25 of 156 with 50-69% ICA stenosis. The indications for CEA were transient ischemic attack (TIA) in 88 (30.7%), amaurosis fugax in 60 (20.9%), previous stroke in 91 (31.7%) and asymptomatic disease in 48 (16.7%) cases. There were no statistically significant differences between the groups operated on with and without preoperative angiography with respect to the indications for surgery, associated risk factors, or the degree of stenosis on the contralateral side. In patients undergoing surgery without angiography, there were no unexpected findings that influenced the performance of surgery, in all except 1. There were no significant differences in perioperative morbidity and mortality in patients undergoing surgery with and without conventional angiography. The combined mortality and major stroke rates were 3.4% and 2.2%, respectively. It is concluded that CEA can safely be performed without preoperative angiography in cases with conclusive duplex scan findings.

Angio-RM das artérias carótidas e vertebrais: análise de diferentes técnicas de volume e diluição de contraste em aparelho de 1,0 t e gradiente de 15 mt/m

OBJETIVO: Avaliar as artérias cervicais (carótidas e vertebrais) por meio da angio-RM, utilizando-se diferentes dosagens e diluições de contraste paramagnético. MATERIAIS E MÉTODOS: Estudo prospectivo em 15 pacientes, com análise de 30 artérias carótidas comuns, 30 artérias carótidas internas, 30 artérias carótidas externas e 30 artérias vertebrais, utilizando-se diferentes volumes e dosagens de contraste paramagnético: grupo I <FONT FACE=Symbol>-</FONT> dose única (14 ml de Gd-DTPA); grupo II <FONT FACE=Symbol>-</FONT>dose dupla (28 ml de Gd-DTPA); grupo III <FONT FACE=Symbol>-</FONT> dose única e diluída a 50%. A injeção de contraste foi realizada com a utilização de bomba injetora e com velocidades de injeção de 2 ml/s (grupo I) e 3 ml/s (grupos II e III). Os segmentos arteriais foram analisados por três examinadores em consenso de forma subjetiva, avaliando-se o grau de visibilidade, intensidade de contrastação e definição de seus contornos. RESULTADOS: Em todos os itens analisados os pacientes do grupo II apresentaram melhor resultado (visibilização total, boa contrastação dos vasos e contornos bem definidos). No grupo I houve boa visibilização das artérias carótidas e vertebrais, porém a intensidade de contraste e a definição dos contornos apresentaram variabilidade qualitativa. O grupo III apresentou os piores resultados, com dificuldade de visibilização, intensidade de contrastação baixa e contornos mal definidos. CONCLUSÃO: Entre os grupos analisados, a técnica utilizando dose dupla de gadolínio é a que permite melhor avaliação das artérias cervicais. A utilização de contraste diluído prejudica a avaliação dos vasos do pescoço.

Magnetic resonance angiography and evaluation of cervical arteries

Multiple clinical trials have demonstrated the efficacy of endarterectomy in selected groups of patients based primarily on percent diameter stenosis. Although measurement of stenosis in the clinical trials was established by conventional angiography, there is considerable interest in noninvasive alternatives. Magnetic resonance angiography, performed using time-of-flight methods or with contrast enhancement, is one of several alternatives for noninvasive carotid evaluation. Screening examinations are routinely performed for carotid stenosis. Preoperative evaluations based on one or a combination of noninvasive tests have been proposed, although these proposals are the subject of ongoing controversy. Evaluation of the vertebral arteries is more difficult and less well studied: however, the increasing availability of therapies for posterior circulation atherosclerotic narrowing is resulting in increased interest in this problem.

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.

Redefined duplex ultrasonographic criteria for diagnosis of carotid artery stenosis

OBJECTIVE

To evaluate duplex ultrasonographic criteria for the determination of 50% or more and 70% or more stenosis of the diameter of the internal carotid artery based on conventional angiography in order to align ultrasonographic diagnostic categories with current clinical management schemes.

PATIENTS AND METHODS

Between January 1, 1995, and June 30, 1999, 915 patients underwent both carotid duplex ultrasonography and cerebral angiography within 30 days at Mayo Clinic, Rochester, Minn. Of these patients, 294 were excluded from this study because of occlusion of one or both of the internal carotid arteries or atypical flow characteristics. In the remaining 621 patients (61 % male, 39% female; mean age, 67.7 years [range, 14-88 years]), 1218 vessels were available for correlation. Several Doppler ultrasonographic velocity variables were compared with the angiographic findings by use of receiver operating characteristic curve analysis. The primary end point was verification of optimal ultrasonographic criteria to diagnose 70% or more internal carotid artery stenosis. The secondary end point was establishment of threshold values to detect stenosis of 50% or more.

RESULTS

At angiography, 382 patients had internal carotid arteries with 70% or more stenosis. Peak systolic and end diastolic velocities of the internal carotid artery and internal carotid artery:common carotid artery peak systolic velocity ratios were measured. For an internal carotid artery stenosis of 70% or more, a peak systolic velocity of 230 cm/s or more resulted in a sensitivity of 86.4%, a specificity of 90.1%, a positive predictive value of 82.7%, a negative predictive value of 92.3%, and an accuracy of 88.8%. An end diastolic velocity of 70 cm/s or more and an internal carotid artery:common carotid artery ratio of 3.2 or more yielded similar values. For an internal carotid artery stenosis of 50% or more, a peak systolic velocity of 130 cm/s or more resulted in a sensitivity of 92.1 %, a specificity of 89.5%, a positive predictive value of 90.3%, a negative predictive value of 91.3%, and an overall accuracy of 90.8%. An internal carotid artery:common carotid artery ratio of 1.6 or more yielded similar values.

CONCLUSION

In our ultrasonography laboratory, a carotid artery stenosis of 70% or more (for which carotid endarterectomy is typically recommended in symptomatic patients) is diagnosed reliably with the following duplex ultrasonographic criteria: a peak systolic velocity of 230 cm/s or more, an end diastolic velocity of 70 cm/s or more, or an internal carotid artery:common carotid artery ratio of 3.2 or more.

Color-coded duplex ultrasound compared to CT angiography for detection and quantification of carotid artery stenosis

OBJECTIVE

The purpose of this study was to compare findings on color-coded duplex ultrasound and CT angiography for grading internal carotid artery stenosis, and to investigate whether both these imaging modalities are necessary for an accurate diagnosis of carotid stenosis in the pre-surgical assessment of the internal carotid artery.

PATIENTS AND METHODS

We examined 92 internal carotid arteries from 46 randomly chosen patients with suspected carotid stenosis by color-coded duplex ultrasound and by three-dimensional CT angiography (CTA). This retrospective study adhered to international guidelines with gradings of mild, moderate, severe, and occlusive carotid disease.

RESULTS

The study demonstrated agreement between the degree of stenosis found on color-coded duplex ultrasound and that found on CTA in 78% of cases overall and in 79% of patients requiring surgical intervention. When compared to CTA, color-coded duplex ultrasound yielded a sensitivity of 78.9% and a specificity of 96.3%. Although findings on color-coded duplex ultrasound and CTA were comparable, disagreement affecting treatment decision occurred in 10:92 arteries.

CONCLUSION

CTA was not found to be beneficial for patients exhibiting mild stenosis on color-coded duplex ultrasound, as none of the mild groupings found by sonography were interpreted as severe or occluded by CTA. However, CTA may be an important adjunct to color-coded duplex ultrasound regarding the categories of moderate, severe and occluded when carotid endarterectomy is considered.

Magnetic resonance angiography is an accurate imaging adjunct to duplex ultrasound scan in patient selection for carotid endarterectomy

PURPOSE

The purpose of this study was to evaluate the accuracy of magnetic resonance angiography (MRA) for categorizing the severity of carotid disease relative to duplex ultrasound scan and cerebral contrast arteriography (CA) to determine if MRA imaging could replace the need for cerebral angiography in cases of indeterminate or inadequate duplex scan imaging.

METHODS

Seventy-four carotid bifurcations in 40 patients undergoing 45 carotid endarterectomies from 1996 to 1998 were imaged with duplex ultrasound scan; MRA (two-dimensional neck and three-dimensional intracranial, time-of-flight technique); and biplanar, digital subtraction cerebral arteriography. Studies were blindly reviewed by one reader who used established threshold velocity criteria for the duplex scan and the North American Symptomatic Carotid Endarterectomy Trial method for MRA and CA to determine the percentage of diameter reduction of the internal carotid artery (ICA). Disease severity was grouped into four categories (< 50%, 50%-74%, 75%-99% stenosis and occlusion), and the results of MRA and duplex ultrasound scan were compared with CA.

RESULTS

Sensitivity, specificity, positive predictive value, and negative predictive value for detection of > 50% ICA stenosis were 100%, 96%, 98%, and 100% for MRA and 100%, 72%, 88%, and 100% for duplex ultrasound scan, respectively; similarly, for detection of > 75% ICA stenosis values were 100%, 77%, 76%, and 100% for MRA and 90%, 74%, 72%, and 91% for duplex ultrasound scan, respectively. Both MRA and duplex ultrasound scan accurately differentiated all cases of > 95% stenosis (n = 7) from occlusion (n = 4). Short length ICA flow gaps were present on MRA in all cases of 75% to 99% stenosis and one half of cases of CA-defined 50% to 74% stenosis. In patients with 50% to 74% stenosis, the mean angiographic stenosis was significantly greater when a flow gap was present on MRA (64% +/- 6%) versus no flow gap (57% +/- 7%) (P =.04). There was overall agreement among duplex ultrasound scan, MRA, and CA in 73% of carotids imaged. Of the 24% discordant results between MRA and duplex ultrasound scan, MRA correctly predicted disease severity in all cases, and inaccurate duplex ultrasound scan results were due to overestimation in 83% of cases. The operative plan was altered by CA findings in only one patient (2%) after duplex ultrasound scan and MRA.

CONCLUSIONS

MRA can accurately categorize the severity of carotid occlusive disease. Duplex ultrasound scan facilitates patient selection for carotid endarterectomy in most cases, but adjunct use of MRA improves diagnostic accuracy for > 75% stenoses and may obviate the need for cerebral arteriography when duplex scan results are inconclusive or demonstrate borderline disease severity.

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.

Are we still performing inappropriate carotid endarterectomy?

OBJECTIVES

the 1998 ECST final report suggests that the decision to operate on patients with greater than 70% symptomatic stenosis should be based on a statistical model incorporating age, sex and degree of stenosis. The aim of this study was to identify patients operated on the basis of the 1991 reports who would not now be offered surgery according to the 1998 ECST recommendations and to determine the surgical morbidity and mortality arising from these <<<<inappropriate>>>> CEAs.

METHODS

interrogation of a prospectively gathered database of all CEAs performed for symptomatic stenosis between 1st January 1994 and 1st May 1998. CEAs were classified as <<<<beneficial>>>>, <<<<uncertain>>>> or <<<<hazardous>>>> according to the 1998 ECST recommendations.

RESULTS

there were 154 males and 72 females (median age (range) was 67 (39-85) and 65 (38-81), respectively). In males 101 (66%) of CEAs were <<<<beneficial>>>>, 51 (33%) were <<<<uncertain>>>> and only two (1%) were <<<<hazardous>>>>. In women, the corresponding proportions were 13 (18%), 45 (63%) and 14 (19%), respectively. The combined peri-operative major stroke (Rankin 3-5) and death rate was 1.8% (4 patients). Of these, three, one and zero patients were in the <<<<beneficial>>>>, <<<<uncertain>>>> and <<<<hazardous>>>> groups.

CONCLUSIONS

strict adherence to the 1998 ECST recommendations would reduce by 50% the number of CEAs currently performed in this vascular unit and, in general, would restrict CEA to a higher risk group. The validity of the ECST model requires further evaluation.

Selection of patients for carotid endarterectomy

OBJECTIVE

The aim of this study was the definition of the duplex scan parameters that best select patients for carotid endarterectomy.

METHODS

This study was set in a regional vascular unit. Duplex scanning and angiography were performed prospectively on 50 patients who were symptomatic (100 carotid bifurcation) to identify the most accurate and sensitive duplex scan criteria to identify an 80% to 99% stenosis according to the European Carotid Symptomatic Trial. With data from the European Carotid Symptomatic Trial, we estimated the effect of three different approaches used to select patients for carotid endarterectomy. The first approach was the selection of patients for carotid surgery on the basis of duplex scanning alone with the most accurate duplex scan criteria (approach I). The second approach was the selection of patients for carotid surgery on the basis of duplex scanning alone with a 100% sensitive duplex scan criteria (approach II). The third approach was the selection of patients for angiography with duplex scanning (100% sensitive criteria) and then the use of angiography to define which patients should undergo surgery (approach III).

RESULTS

All three approaches appeared to have a similar potential in stroke reduction. However, approach I, which minimized the number of patients who underwent surgery (19% less than approach II) or invasive imaging (65% less than approach III), appeared to be the most appropriate.

CONCLUSION

These data support the selection of patients for carotid endarterectomy on the basis of duplex scanning alone. The duplex scan criteria should be validated against angiography.

Carotid arteries: maximizing arterial to venous contrast in fluoroscopically triggered contrast-enhanced MR angiography with elliptic centric view ordering

PURPOSE

To obtain high-spatial-resolution, venous-suppressed, contrast material-enhanced, three-dimensional (3D) magnetic resonance (MR) angiograms of the carotid arteries and aortic arch by using an elliptic centric view ordering with MR fluoroscopic triggering.

MATERIALS AND METHODS

Forty consecutive patients with cerebrovascular disease in the differential diagnosis were evaluated with fluoroscopically triggered 3D MR angiography (gadoteridol dose range, 0.1-0.3 mmol per kilogram of body weight; mean acquisition time, 40 second +/- 8 [SD]). The contrast-enhanced 3D MR angiograms were evaluated for overall quality, vascular signal intensity, venous suppression, and motion artifact. Twenty patients also underwent two-dimensional (2D) time-of-flight (TOF) MR angiography. The overall quality of the 2D TOF MR angiograms and comparative quality between the 2D TOF and contrast-enhanced 3D MR angiograms were determined.

RESULTS

The contrast-enhanced 3D MR angiograms were of excellent or more than adequate quality for diagnosis in 36 of the 40 studies (90%). In 35 of the 38 contrast-enhanced 3D studies in which the contrast material bolus was detected fluoroscopically, the internal jugular vein signal intensity was either not detectable or barely visible. In 18 of the 20 patients who also underwent 2D TOF MR angiography, the quality of the contrast-enhanced 3D MR angiograms was graded as markedly superior or superior.

CONCLUSION

Contrast-enhanced, elliptic centric 3D MR angiography with real-time MR fluoroscopic triggering offers high-spatial-resolution images of the carotid arteries and aortic arch with reliable venous suppression.

Carotid endarterectomy without angiography does not compromise operative outcome

OBJECTIVES

Carotid angiography is associated with a 2% risk of stroke and, since the advent of colour-duplex ultrasound, its role in the assessment of patients with carotid disease has been the subject of debate. The aim of this study was to evaluate a policy of adopting routine duplex supplemented by selective angiography on operative outcome over a 5-year period.

METHODS

A prospective audit of the results of carotid endarterectomy without routine angiography from January 1992 to December 1996. Angiography was performed only if the ultrasonography was concerned about the distal or proximal extent of disease or to assess subocclusion.

RESULTS

During the study period, 494 carotid endarterectomies were performed but only 35 patients underwent carotid angiography. The indications for angiography were subocclusion/string sign in 22 patients, to assess the limits of proximal or distal disease in 12 and abnormal anatomy in one. During the 5-year study period the overall perioperative death and/or stroke rate was 4.2%. By 1997, the perioperative stroke rate had fallen to 1.3%. In no case in this series was the operation abandoned due to unexpected findings.

CONCLUSION

Although concerns exist about the precise duplex criteria for diagnosing a severe stenosis, this study has shown that a policy of selective angiography does not compromise patient safety or operability and avoids the unnecessary mortality, morbidity and costs associated with routine angiography.

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.

Improving the cost-effectiveness of carotid endarterectomy

PURPOSE

Carotid endarterectomy (CEA) has been shown to significantly reduce the risk of stroke caused by carotid artery stenosis. Limiting the costs of CEA without increasing the risks will improve the cost-effectiveness of this procedure.

METHODS

Results were prospectively collected from 63 consecutive CEAs performed in 60 patients who were entered into a clinical pathway for CEA that included avoidance of cerebral arteriography, preferential use of regional anesthesia, selective use of the intensive care unit (ICU), and early hospital discharge. The mortality rate, complications, hospital costs, and net income in these patients were then compared with results from 45 CEAs performed in 42 consecutive patients immediately before beginning the CEA pathway. Age, comorbid risk factors, incidence of symptoms, and degree of carotid artery stenosis were similar in both patient groups.

RESULTS

The rates of mortality and complications associated with CEA were low (mortality rate, 0%; stroke, 0.9%; transient ischemic attack, 2.8%) and did not vary between the two groups. Implementation of the CEA pathway resulted in significant (p < 0.001) reductions in the use of arteriography (74% to 13%), general anesthesia (100% to 24%), ICU use (98% to 30%), and mean hospital length of stay (5.8 days to 2.0 days). These changes resulted in a 41% reduction in mean total hospital cost ($9652 to $5699) and a 124% increase in mean net hospital income ($1804 to $4039) per CEA (p < 0.01). For the 39 patients (62%) who achieved all elements of the CEA pathway, the mean hospital length of stay was 1.3 days, the mean hospital cost was $4175, and the mean hospital income was $4327.

CONCLUSIONS

Costs associated with CEA can be reduced substantially without increased risk. This makes CEA an extremely cost-effective treatment of carotid disease against which new therapeutic approaches must be measured.