Role of Conventional Angiography in Evaluation of Patients With Carotid Artery Stenosis Demonstrated by Doppler Ultrasound in General Practice

Abstract

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 Ն50% stenosis and asymptomatic patients with Ն60% 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, 69Ϯ8.8 years) who met Doppler ultrasound criteria, 22 (17%) and 8 patients (6%)were found to have 30% to 49% or Ͻ30% stenosis by angiography, respectively. The positive predictive value of carotid Doppler ultrasound for identifying appropriate symptomatic candidates for carotid intervention (angiographic stenosis Ն50%) 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 Ն60%) 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.

Reliability of Carotid Doppler performed in a dedicated Stroke Prevention Clinic

“…We report a high accuracy rate of carotid DUS when performed in the SPC. The misclassification rate in our study for symptomatic stenosis (50-99%) was 2.2 % (95%CI: 0 -6.5%), and overall 1.45% (95%CI: 0 -4.3%), which is much lower than the recently reported misclassification rate of 28% 8 and the false positive rate of 20% 12 . The wide variation in the reported accuracy rates of DUS cannot solely be explained on the basis of difference in the experience or skill of the technologist, because all these studies were carried out in institutions where DUS imaging is performed by fully trained and accredited ultrasonographers.…”

“…A previous study in 1987 reported a sensitivity of 96%, specificity of 95% and accuracy rate of 95% in 62 patients with an occluded artery demonstrated by duplex scanning. 13 In a more recent study, out of 16 patients with DUS diagnosed complete occlusion, two had stenosis of 70-99% on a subsequent angiogram 12 . This variation in reported diagnostic accuracy of DUS in differentiating between a tight stenosis and complete occlusion has resulted in angiographic confirmation of the ultrasound findings, a widely accepted practice.…”

“…In this study, the authors concluded that clinical evaluation and DUS findings could be used to identify a minority of patients for whom conventional angiography is necessary prior to CEA. Recently another study reported a false positive rate of 20% for DUS (ICA stenosis ≥50%) in identifying symptomatic patients who are appropriate candidates for CEA, and 41% for asymptomatic patients (ICA stenosis ≥60%) when compared to angiographic findings 12 . The false positive rate for the 19 external DUS laboratories was 41% overall, compared to 20% (p=0.03) for the hospital's own internal service.…”

Estenose de carótida extracraniana

“…Entretanto, Qureshi e cols. 22 observaram que o ultra-som apresentou falso positivo de 20% para estenoses > 50% em pacientes sintomáticos e falso positivo de 41% para estenoses < 60% em pacientes assintomáticos. Assim, é recomendada, antes de tomar a devida conduta, realizar angiografia de carótidas nos pacientes cujo ultra-som detectou estenose > 50% 22 .…”

“…22 observaram que o ultra-som apresentou falso positivo de 20% para estenoses > 50% em pacientes sintomáticos e falso positivo de 41% para estenoses < 60% em pacientes assintomáticos. Assim, é recomendada, antes de tomar a devida conduta, realizar angiografia de carótidas nos pacientes cujo ultra-som detectou estenose > 50% 22 . Como alternativa para esse subgrupo, foram estudados 92 pacientes com evidências clí-nicas e ultra-sonográficas de estenose, utilizando ressonância nuclear magnética tridimensional contrastada comparada à angiografia com subtração digital, obtendo-se uma sensibilidade, especificidade e acurácia de 97%, 82% e 92,5% respectivamente 23 .…”