Transcranial Doppler in Asymptomatic Carotid Stenosis Representing Hemodynamic Impairment: Correlation Study with Magnetic Resonance Imaging

Unilateral versus bilateral middle cerebral artery detection of right-to-left shunt by power M-mode transcranial doppler

BACKGROUND AND PURPOSE

Comparison was performed between unilateral and bilateral power M-mode transcranial Doppler to detect right-to-left circulatory shunt (RLS).

METHODS

Recorded Doppler data from 87 patients with confirmed RLS referred for transcatheter closure of patent foramen ovale were reanalyzed for embolic tracks (ET) counted from left and right temporal bone windows during bubble study. Unilateral counts were obtained by multiplying each side by 2; bilateral counts were obtained by summing left and right ET. Both unilateral and bilateral ET were converted to a 6-point logarithmic grade. Sex and age group subanalyses were performed.

RESULTS

At rest, significantly more ET were detected with bilateral versus unilateral detection (P= .01), but not following Valsalva (P= .13). Unilateral and bilateral detection were equally able to detect large RLS (grades IV or V) following Valsalva (P= 1.00). For the group aged > or =55 years, the right-hand side yielded greater ET than the left-hand side (mean difference 9%+/- 37; 95% confidence interval -3 to 21%) at rest (P= .01), but not following Valsalva (mean difference 1%+/- 25; 95% confidence interval -7 to 9%, P= .10).

CONCLUSIONS

Unilateral detection of ET by power M-mode transcranial Doppler is equivalent to bilateral detection to assess RLS.

The impact of carotid stenting on the hemodynamic parameters and cerebrovascular reactivity of the ipsilateral middle cerebral artery

OBJECTIVE

The study was conducted to determine the effect of carotid angioplasty and stenting (CAS) on the hemodynamic parameters and cerebrovascular reactivity (CVR) of the ipsilateral middle cerebral artery (MCA) and examine the relation between preprocedural exhausted CVR and perioperative neurologic events.

METHODS

The study included 29 patients with severe extracranial carotid stenosis undergoing CAS. Transcranial Doppler imaging was performed before the procedure, 2 days, and 2 to 4 months postoperatively. Peak systolic velocity, end-diastolic velocity, mean flow velocity, and pulsatility index of the ipsilateral MCA were recorded at rest. CVR was assessed with the breath holding test: the increase of mean flow velocity and the breath holding index were calculated.

RESULTS

Peak systolic and mean flow velocities increased significantly in both postoperative studies compared to the preoperative values, end-diastolic velocity was significantly elevated only in the first study, and pulsatility index did not change significantly. When stimulated by breath holding, preoperative mean flow velocity did not increase significantly compared with the resting values; however, it did increase significantly during breath holding in both studies after CAS. The breath holding index improved significantly from -0.35 (-0.71 to 0.55) to 0.38 (0.12 to 0.61) at 2 days (P = .049) and 0.44 (0.31 to 0.92) at 2 to 4 months (P = .020). Exhausted CVR of the MCA preoperatively was associated with increased risk of neurological complications during or after the procedure (P = .006).

CONCLUSIONS

CAS may improve the hemodynamic parameters and the vasomotor reactivity in the ipsilateral MCA. Exhausted CVR is associated with an increased risk of periprocedural neurologic complications.

Cerebral hemodynamics in symptomatic and asymptomatic patients with severe unilateral carotid stenosis before and after carotid endarterectomy

BACKGROUND

Data concerning hemodynamic status prior to and after carotid endarterectomy (CEA) in symptomatic and asymptomatic patients is insufficient. Transcranial Doppler (TCD) provides information regarding compensatory collateral flow as well as mechanisms of cerebral autoregulation in patients with carotid stenosis.

PATIENTS AND METHODS

Forty eight symptomatic and 81 asymptomatic patients with unilateral severe carotid stenosis were examined by TCD before and in early postoperative period after CEA.

RESULTS

Cigarette smoking was the only risk factor significantly more frequent in symptomatic patients. Preoperative anterior cerebral artery (ACA) and middle cerebral artery (MCA) asymmetry, basilar artery velocity and number of ophthalmic arteries with reversed flow, were not significantly different between the two groups. Pulsatility index, cerebrovascular reactivity and flow acceleration on the side of stenosis were significantly lower in symptomatic patients. After surgery there was a significant improvement of all TCD parameters in symptomatic as well as asymptomatic patients.

CONCLUSIONS

The exhausted ability of cerebral autoregulation is an important factor differentiating between symptomatic and asymptomatic patients with severe carotid stenosis. Successful surgery provides good recovery of cerebral hemodynamics in both symptomatic and asymptomatic patients.