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A broad diagnostic battery for bedside transcranial Doppler to detect flow changes with internal carotid artery
I Christou1, R A Felberg, A M Demchuk
1Center for Noninvasive Brain Perfusion Studies, Stroke Program, University of Texas-Houston, USA.
Background And Purpose:
The authors establish accuracy parameters of a broad diagnostic battery for bedside transcranial Doppler (TCD) to detect flow changes due to internal carotid artery (ICA) stenosis or occlusion.
Methods:
The authors prospectively studied consecutive patients with stroke or transient ischemic attack referred for TCD. TCD was performed and interpreted at bedside using a standard insonation protocol. A broad diagnostic battery included major criteria: collateral flow signals, abnormal siphon or terminal carotid signals, and delayed systolic flow acceleration in the middle cerebral artery. Minor criteria included a unilateral decrease in pulsatility index (< or = 0.6 or < or = 70% of contralateral side), flow diversion signs, and compensatory velocity increase. Angiography or carotid duplex ultrasound (CDU) was used to grade the degree of carotid stenosis using North American criteria. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of TCD findings were determined.
Results:
Seven hundred and twenty patients underwent TCD, of whom 517 (256 men and 261 women) had angiography and/or CDU within 8.8 +/- 0.9 days. Age was 63.1 +/- 15.7 years. For a 70% to 99% carotid stenosis or occlusion, TCD had sensitivity of 79.4%, specificity of 86.2%, PPV of 57.0%, NPV of 94.8%, and accuracy of 84.7%. For a 50% to 99% carotid stenosis or occlusion, TCD had sensitivity of 67.5%, specificity of 83.9%, PPV of 54.5%, NPV of 90.0%, and accuracy of 81.6%. TCD detected intracranial carotid lesions with 84.9% accuracy and extracranial carotid lesions with 84.4% accuracy (sensitivity of 88% and 79%, specificity of 85% and 86%, PPV of 24% and 54%, and NPV of 99% and 95%, respectively). The prevalence of the ophthalmic artery flow reversal was 36.4% in patients with > or = 70% stenosis or occlusion. If present, this finding indicated a proximal ICA lesion location in 97% of these patients.
Conclusions:
In symptomatic patients, bedside TCD can accurately detect flow changes consistent with hemodynamically significant ICA obstruction; however, TCD should not be a substitute for direct carotid evaluation. Because TCD is sensitive and specific for a > or = 70% carotid stenosis or occlusion in both extracranial and intracranial carotid segments, it can be used as a complementary test to refine other imaging findings and detect tandem lesions.