Transcranial Doppler waveform blunting in severe extracranial carotid artery stenosis

OBJECTIVE: To investigate the frequency of transcranial Doppler (TCD) waveform blunting in patients with severe (80-99%) symptomatic or asymptomatic extracranial carotid artery stenosis. BACKGROUND: Severe carotid artery stenosis has been identified as a risk factor for ischemic stroke. Blunted Doppler flow waveforms (reduced systolic flow velocity and pulsatility) of the middle cerebral artery (MCA) are inferred to reflect hemodynamic impairment, possibly indicating an increased risk of stroke. METHODS: The 114 consecutive patients (mean age 72.4 years, SD 9.0 years; 37% women; 46 clinically symptomatic, 68 asymptomatic) with 80-99% stenosis of the extracranial internal carotid artery (ICA), as determined by duplex sonography, were examined with TCD. Flow velocities, pulsatility index, and spectral waveforms of the MCA distal to the ICA stenosis were assessed blinded to the clinical status of the ICA: Doppler waveform blunting was defined as loss of the characteristic systolic peak. Odds ratios with 95% confidence intervals and chi(2) statistics were used to describe the association between waveform blunting and the symptomatic status of the ICA stenosis. RESULTS: Among symptomatic patients, 23 (50%) had completed strokes, and a further 23 (50%) had transient neurologic deficits in the territory of the stenotic ICA. Blunted spectral waveform was found in 37 (80%, 95% CI 68-92%) of the symptomatic and 25 (37%; 95% CI 25-49%) of the asymptomatic patients. Symptomatic patients had significantly increased odds of having blunted TCD waveforms (OR 7.5, 95% CI 3.1-18.1, p < 0.001). CONCLUSIONS: Our findings suggest that TCD waveform blunting in the MCA as here described may be an additional risk factor in the setting of severe extracranial carotid artery stenosis. A prospectively designed study to confirm our results seems warranted.