Identification of hemodynamic compromise by cerebrovascular reserve and oxygen extraction fraction in occlusive
Edwin M Nemoto1, Howard Yonas, Hiroto Kuwabara
1Department of Neurological Surgery, University of Pittsburgh Medical Center, Pennsylvania, USA. nemotoem@upmc.edu
Insights
Cerebrovascular reserve (CVR) and oxygen extraction fraction (OEF) are negatively related in carotid occlusion, but CVR changes can indicate compromise before OEF does, correlating with infarction.
Area of Science:
- Neurology
- Vascular Medicine
- Medical Imaging
Background:
- Cerebrovascular reserve (CVR) and oxygen extraction fraction (OEF) assess hemodynamic compromise in carotid occlusive disease.
- Evidence suggests CVR and OEF are not interchangeable measures.
Purpose of the Study:
- To investigate the relationship between CVR and OEF.
- To evaluate their equivalence and stages of hemodynamic compromise in patients with carotid occlusion.
Main Methods:
- 12 symptomatic patients with carotid occlusion underwent stable xenon-CT CBF for CVR after acetazolamide.
- Positron emission tomography (PET) was used for OEF within 24 hours.
- Analysis included middle cerebral artery territories, hemispheres, and white matter infarction grading via MRI.
Main Results:
- A significant negative linear relationship was found between CVR and OEF (P = 0.001).
- 37.5% of hemispheres showed compromised CVR with normal OEF, correlating with subcortical white matter infarction (P = 0.019).
- Elevated CMRO2 was observed in stage II hemodynamic compromise (CVR < 10%, OEF > 50%).
Conclusions:
- CVR and OEF exhibit a significant negative linear relationship in stage II hemodynamic compromise.
- Compromised CVR with normal OEF identifies hemispheres at risk for infarction, suggesting CVR may detect compromise earlier than OEF.
Abstract:
Cerebrovascular reserve (CVR) and oxygen extraction fraction (OEF) are used to identify hemodynamic compromise in symptomatic patients with carotid occlusive vascular disease, but evidence suggests that they are not equivalent. The authors studied the relationship between CVR and OEF to evaluate their equivalence and stages of hemodynamic compromise. Symptomatic patients (N = 12) with carotid occlusion were studied by stable xenon-computed tomography CBF after intravenous acetazolamide administration for CVR, followed within 24 hours by positron emission tomography (PET) for OEF. Middle cerebral artery territories were analyzed by hemisphere and level. Hemispheric subcortical white matter infarctions were graded with magnetic resonance imaging. Both hemispheric and level analysis of CVR and OEF showed a significant (P = 0.001), negative linear relationship [CVR (%) = -1.5 (OEF) + 83.4, (r = -0.57, P = 0.001, n = 24]. However, 37.5% of the hemispheres showed compromised CVR but normal OEF and were associated (P = 0.019) with subcortical white matter infarction. CMRO2 was elevated in stage II hemodynamic compromise (CVR < 10%, OEF > 50%). CVR and OEF showed a significant negative linear relationship in stage II hemodynamic compromise but revealed hemispheres in hemodynamic compromise by CVR but normal OEF that were associated with subcortical white matter infarction.
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