2007 Abstracts: Accuracy and Utility of 3D Contrast-Enhanced MR Angiography in Planning Carotid Stenting

Background: Contrast-enhanced magnetic resonance angiography (CE-MRA) is a proven diagnostic tool for the evaluation of carotid artery occlusive disease; however, its utility in planning carotid artery stenting (CAS) has not been addressed. The purpose of this study was to assess the accuracy of 3-dimensional CE-MRA as a non-invasive screening tool, compared with digital subtraction angiography (DSA), for evaluating carotid and arch morphology prior to CAS.
Methods: In a series of 96 CAS procedures over a 2-year period, carotid and aortic arch CE-MRA and DSA were obtained prior to CAS in 82 patients. Four additional patients, initially considered potential candidates for CAS, were also evaluated with CE-MRA and DSA. The 2 x 2 table method, kappa statistic, and Bland-Altman analysis were used to characterize the ability of CE-MRA to discriminate carotid and arch anatomy, suitability for CAS and degree of carotid stenosis confirmed angiographically.
Results: The sensitivity and specificity of CE-MRA were 95% and 98% to determine CAS suitability, 96% and 99% to define aortic arch type and 98% and 100% to determine severe carotid tortuosity, respectively. CE-MRA had a sensitivity and specificity of 92% and 79%, respectively, for the detection of carotid stenosis ≥ 70%. The accuracy of CE MRA to determine optimal imaging angles and stent and embolic protection device (EPD) sizes was > 90%. The operative technique for CAS was altered based on the findings of preoperative CE-MRA in 33 patients (38 %). The most frequent changes in the operative plan included the use of different guiding catheter or telescoping technique in 22 patients (26%). Based on CE-MRA findings, carotid and arch morphology could be determined with good to excellent reliability (kappa= 0.74; 95% CI, 0.59-0.88). In four patients (5%), CAS was aborted due to unfavorable anatomy identified on CE-MRA, including prohibitive ICA tortuosity (n=1), long string sign of the ICA (n=2), and concomitant intracranial disease (n=1). Patients considered suitable for CAS based on CE-MRA had 100% technical success and 1.2% 30-day stroke-death rate.
Conclusions: CE MRA of the arch and carotid arteries is accurate in determining suitability for CAS and may alter the plan for CAS in 38% of patients. Certain anatomic contraindications for CAS may be detected without subjecting the patients to DSA. Although CE-MRA is less reliable for the precise determination of the degree of stenosis, it can accurately predict imaging angles, stent and EPD size, which may facilitate safe and expeditious CAS. CE-MRA with the use of carotid MRI analyses of plaque burden and composition prior to CAS deserve further study and has the potential to provide a comprehensive and noninvasive evaluation in a single study.