Impact of oxygen extraction fraction on long-term prognosis in patients with reduced blood flow and vasoreactivity because of occlusive carotid artery disease.
BACKGROUND
Reduced cerebral blood flow and cerebrovascular reactivity to acetazolamide (type 3 ischemia) is believed as an independent predictor for subsequent ischemic stroke in patients with occlusive carotid artery diseases. However, recent studies have shown that type 3 patients can be divided into 2 pathophysiologically different subgroups as follows: those with elevated OEF and those with normal OEF. This study was aimed to clarify whether there is a difference in the prognosis between patients with type 3 and elevated OEF and those with type 3 but normal OEF.


METHODS
Twenty type 3 patients were enrolled in this prospective, longitudinal cohort study. Hemodynamic and metabolic parameters were quantitatively determined by (15)O-gas PET. All of them were medically treated.


RESULTS
Oxygen extraction fraction was elevated in 9 patients but was normal in other 11. During an average follow-up period of 45.6 months, 3 of 9 patients with type 3 and elevated OEF developed ipsilateral ischemic stroke. The annual risk was 10.6%. The location and shape of cerebral infarction strongly suggested a key role of hemodynamic compromise in their recurrence. On the other hand, no subsequent stroke occurred in none of 11 patients with type 3 but normal OEF. There was a statistically significant difference in the incidence of ipsilateral ischemic stroke between 2 groups (P = .0303).


CONCLUSIONS
Type 3 patients may be categorized into 2 subgroups as follows: those with elevated OEF and higher stroke risk and those with normal OEF and lower stroke risk, although larger number of subjects should be analyzed.
Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo 060-8638, Japan.
Masaaki
M
Hokari
Satoshi
S
Kuroda
Tohru
T
Shiga
Naoki
N
Nakayama
Nagara
N
Tamaki
Yoshinobu
Y
Iwasaki
D000086:Acetazolamide; D000368:Aged; D002545:Brain Ischemia / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology; D002257:Carbonic Anhydrase Inhibitors; D016893:Carotid Stenosis / Q000150:complications / Q000503:physiopathology*; D002536:Cerebral Arteries / Q000378:metabolism / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D010104:Oxygen Radioisotopes; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D055502:Secondary Prevention; D020521:Stroke / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*; D015899:Tomography, Emission-Computed, Single-Photon
D002257:Carbonic Anhydrase Inhibitors; D010104:Oxygen Radioisotopes; D000086:Acetazolamide