Differentiating Carotid Free-Floating Thrombus From Atheromatous Plaque Using Intraluminal Filling Defect Length on
Carlos Torres1, Cheemun Lum2, Paulo Puac-Polanco2
1From the Division of Neuroradiology (C.T., P.P.-P.), Department of Radiology, Division of Neurology (G.S., M.C.F.S., D.B., R.L., P.D., D.D.), Department of Medicine, Division of Medical Physics (R.T.), Department of Radiology, and School of Epidemiology and Public Health (F.M.), University of Ottawa; Neuroscience Program (C.T., G.S., M.C.F.S., D.B., D.D.), The Ottawa Hospital Research Institute; Division of Neuroradiology (A.B.), Department of Medical Imaging, St. Michael's Hospital, University of Toronto, Ontario; and Departments of Clinical Neurosciences, Radiology, and Community Health Sciences (B.K.M.), University of Calgary, Foothills Medical Centre, Alberta, Canada. catorres@toh.ca.
Objective:
To validate a previously proposed filling defect length threshold of >3.8 mm on CT angiography (CTA) to discriminate between free-floating thrombus (FFT) and plaque of atheroma.
Methods:
This was a prospective multicenter observational study of 100 participants presenting with TIA/stroke symptoms and a carotid intraluminal filling defect on initial CTA. Follow-up CTA was obtained within 1 week and at weeks 2 and 4 if the intraluminal filling defect was unchanged in length. Resolution or decreased length was diagnostic of FFT, whereas its static appearance after 4 weeks was indicative of plaque. Diagnostic accuracy of FFT length was assessed by receiver operating characteristic analysis.
Results:
Ninety-five participants (mean [SD] age 68 [13] years, 61 men, 83 participants with FFT, 12 participants with a plaque) were evaluated. The >3.8-mm threshold had a sensitivity of 88% (73 of 83) (95% confidence interval [CI] 78%-94%) and specificity of 83% (10 of 12) (95% CI 51%-97%) (area under the curve 0.91, p < 0.001) for the diagnosis of FFT. The optimal length threshold was >3.64 mm with a sensitivity of 89% (74 of 83) (95% CI 80%-95%) and specificity of 83% (10 of 12) (95% CI 51%-97%). Adjusted logistic regression showed that every 1-mm increase in intraluminal filling defect length is associated with an increase in odds of FFT of 4.6 (95% CI 1.9-11.1, p = 0.01).
Conclusion:
CTA enables accurate differentiation of FFT vs plaque using craniocaudal length thresholds.
Trial Registration Information:
ClinicalTrials.gov Identifier: NCT02405845.
Classification Of Evidence:
This study provides Class I evidence that in patients with TIA/stroke symptoms, the presence of CTA-identified filling defects of lengths >3.8 mm accurately discriminates FFT from atheromatous plaque.
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