CEREBRAL HEMODYNAMIC CONSIDERATIONS IN OBSTRUCTIVE CAROTID-ARTERY DISEASE

46 subjects with obstructive carotid artery disease were investigated with transcranial Doppler ultrasonography. Their baseline blood veloci ties (V) in the middle, anterior and posterior cerebral artery (MCA, A CA and PCA) and in the extracranial internal carotid artery (ICA) were measured and the pulsatility index (PI) calculated for each vessel. T hereafter the vasomotor reserve in both MCAs was tested. Typical patte rns of V, PI and vasomotor reactivity are presented. Arterial collater als were recognized by their relatively increased velocities. We demon strated a close association of the baseline variables V and PI and the total vasomotor reactivity (hypocapnic plus no, hypercapnic response) by calculating an index of U-hem related to the cerebrovascular tone. The U-hem index is expressed by: U-hem index = V-MCA. PIMCA/V-PCA. PI PCA The relationship between U-hem index and the total vasomotor react ivity seemed to correspond to a hyperbolic curve. The hyperbolic tange nt of U-hem index and total vasomotor reactivity correlated highly sig nificantly, r = 0.8203, p < 0.0001, n = 49. the best fit for the regre ssion line was Y = -0.0005+U-hem index 51.3. On the 99% significance l evel an U-hem index greater than or equal to 0.94 indicated normal tot al cerebral vasomotor reactivity in contrast to an impaired reactivity when less than or equal to 0.81. Findings in 20 patients investigated post hoc supported the validity of our concept.