Cerebrovascular Reacivity Assessment in Patients with Carotid Artery Disease: A Combined TCD and NIRS Study

BACKGROUND AND PURPOSE Transcranial Doppler (TCD) and near-infrared spectroscopy (NIRS) are two noninvasive diagnostic tools that have been shown to evaluate cerebral vasomotor reactivity by measuring changes in mean cerebral blood flow velocities (MCBFV) of proximal intracranial arteries and absolute brain-tissue oxygen-saturation (TOS) in microcirculation, respectively, during hemodynamic challenge. We evaluated the potential correlation between TCD and NIRS measurements of vasomotor reactivity (VMR) in patients with carotid artery disease (CARAD). METHODS Consecutive patients (n = 24) with CARAD underwent simultaneously TCD and NIRS examinations during voluntary breath-holding (BH). MCBFV and TOS values were recorded at baseline (BAS) and at the end of BH, while BH duration (DBH) was documented. VMR was quantified by means of TCD-BHI (Breath-holding Index: [MCBFVBH- MCBFVBAS]x 100/MCBFVBAS/DBH) and NIRS-BHI ([TOSBH- TOSBAS]x 100/ TOSBAS/DBH). RESULTS TCD-BHI correlated positively with NIRS-BHI in the affected side (r = .538, P = .007). A stronger correlation between TCD-BHI and NIRS-BHI was documented in the nonaffected side (r = .768, P< .001). After adjusting for demographic characteristics, stroke risk factors and symptomatic status NIRS-BHI was linearly and independently associated with TCD-BHI both in the affected (beta:+ .813, P = .001) and unaffected (beta:+ .823, P < .001) side. CONCLUSIONS Circulatory assessment of VMR in proximal cerebral vessels by TCD correlates positively to functional measurements of VMR in microcirculation by NIRS in CARAD patients.