Temporal stability of hemodynamic status in patients with carotid occlusion

The purpose of our investigation was to assess cerebral hemodynamic status longitudinally with serial positron-emission tomogra phy (PET) studies in patients with carotid artery occlusion. We obtained regional measurements of cerebral blood flow (CBF), volume (CBV), cerebral rate of oxygen metabolism (CMRO2), oxygen extraction fraction (OEF), and mean transit time (MTT) using PET scanning in 16 patients with unilateral carotid artery occlusion and repeated these measures 12 to 24 months later. Mean hemispheric quantitative values and left to right hemispheric ratios of these mean values were compared. Hemodynamic stage was assigned based on left to right hemispheric ratios as: Stage 0, normal hemodynamics; Stage 1, increased MTT (autoregulatory vasodilatation); and Stage 2, increased OEF. Statistical significance (p < 0.05) was measured with paired t-tests. The assigned hemodynamic stage remained stable (11 patients) or worsened (3 patients) in 14 of 16 patients. Two patients increased from Stage 0 to 1 and one from Stage 0 to 2. Hemodynamic status improved in two patients. One fell from Stage 1 to 0. The second patient suffered a clinically silent caudate nucleus infarction with subsequent interval reduction in ipsilateral hemispheric CBF and CMRO2. There was no significant change in hemispheric ratios between initial and repeated PET studies for any of the five physiological measurements. A statistically significant increase in mean CMRO2 and CBF between initial and follow-up examinations was observed bilaterally. The results of these data indicate that a one-time measurement of hemodynamic status can adequately assess long-term hemodynamic risk in the majority of patients.

Duke Scholars

Author William John Powers Hospital Neurology